Patent Publication Number: US-2022213847-A1

Title: System and apparatus for energy conversion

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of the earliest available effective filing date and is a continuation application of U.S. patent application Ser. No. 16/418,129 titled “SYSTEM AND APPARATUS FOR ENERGY CONVERSION” having a filing date of May 21, 2019 and which is incorporated herein by reference in its entirety. 
    
    
     FIELD 
     The present subject matter relates generally to energy conversion systems, power generation systems, and energy distribution systems. The present subject matter additionally relates to heat exchangers and heat exchanger systems. The present subject matter further relates to piston engine assemblies, such as closed-cycle engine systems. The present subject matter still further relates to systems and methods for control or operation of one or more systems of the present subject matter herein. 
     BACKGROUND 
     Power generation and distribution systems are challenged to provide improved power generation efficiency and/or lowered emissions. Furthermore, power generation and distribution systems are challenged to provide improved power output with lower transmission losses. Certain power generation and distribution systems are further challenged to improve sizing, portability, or power density generally while improving power generation efficiency, power output, and emissions. 
     Certain engine system arrangements, such as closed cycle engines, may offer some improved efficiency over other engine system arrangements. However, closed cycle engine arrangements, such as Stirling engines, are challenged to provide relatively larger power output or power density, or improved efficiency, relative to other engine arrangements. Closed cycle engines may suffer due to inefficient combustion, inefficient heat exchangers, inefficient mass transfer, heat losses to the environment, non-ideal behavior of the working fluid(s), imperfect seals, friction, pumping losses, and/or other inefficiencies and imperfections. As such, there is a need for improved closed cycle engines and system arrangements that may provide improved power output, improved power density, or further improved efficiency. Additionally, there is a need for an improved closed cycle engine that may be provided to improve power generation and power distribution systems. 
     Additionally, or alternatively, there is a general need for improved heat transfer devices, such as for heat engines, or as may be applied to power generation systems, distribution systems, propulsion systems, vehicle systems, or industrial or residential facilities. 
     BRIEF DESCRIPTION 
     Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
     An aspect of the present disclosure is directed to a system for energy conversion. The system includes a closed cycle engine containing a volume of working fluid. The engine includes an expansion chamber and a compression chamber each separated by a piston attached to a connection member of a piston assembly. The engine further includes a plurality of heater conduits extended from the expansion chamber. The engine includes a plurality of chiller conduits extended from the compression chamber. The expansion chamber and heater conduits are fluidly connected to the compression chamber and chiller conduits via a walled conduit. 
     In various embodiments, the system includes a cold side heat exchanger through which the plurality of chiller conduits is positioned. The cold side heat exchanger comprises a chiller working fluid passage in direct thermal communication with the plurality of chiller conduits. The chiller working fluid passage is fluidly separated from a chiller passage within the plurality of chiller conduits. In one embodiment, the plurality of chiller conduits is extended at least partially co-directional to an extension of the expansion chamber and the compression chamber within the piston body. In another embodiment, the plurality of chiller conduits is extended at least partially circumferentially relative to the piston body. In yet another embodiment, the system further includes a chamber wall extended between an inner volume wall and an outer volume wall. The inner volume wall at least partially defines the compression chamber. The chamber wall, the inner volume wall, and the outer volume wall together define the chiller working fluid passage, and the plurality of chiller conduits is positioned within the chiller working fluid passage fluidly separated from a chiller working fluid within the chiller working fluid passage. 
     In still various embodiments, the system further includes two or more piston bodies in which the expansion chamber and the compression chamber are positioned within each piston body. The chiller working fluid passage at least partially circumferentially surrounds the piston body in thermal communication with the plurality of chiller conduits. In various embodiments, the chiller working fluid passage includes a first chiller working fluid passage and a second chiller working fluid passage. The first chiller working fluid passage is positioned laterally proximate to the expansion chamber and the second chiller working fluid passage is positioned laterally distal to the expansion chamber relative to the first chiller working fluid passage. In one embodiment, the chiller working fluid flowpath is extended from the first chiller working fluid passage at one piston body to the second chiller working fluid passage at another piston body. 
     In one embodiment, the engine includes a ratio of maximum cycle volume of the working fluid to a volume of the plurality of chiller conduits between 10 and 100. 
     In various embodiments, the engine includes a ratio of surface area of the plurality of chiller conduits to volume of the working fluid within the plurality of chiller conduits between 7 and 40. In one embodiment, the surface area of the plurality of chiller conduits is between a chiller passage opening in fluid communication with the compression chamber and a chiller collection chamber opening in fluid communication with a chiller collector. 
     In one embodiment, the engine includes a ratio of maximum cycle volume of the working fluid to a volume of the plurality of heater conduits between 2.5 and 25. 
     In still various embodiments, the engine includes a ratio of surface area of the plurality of heater conduits to volume of the working fluid within the plurality of heater conduits between 8 and 40. In one embodiment, the surface area of the plurality of heater conduits is between a first opening in direct fluid communication with the expansion chamber and a second opening in direct fluid communication with the walled conduit. 
     In various embodiments, the engine includes a first operating parameter defining a maximum ratio of power output from the connection member, in which the first operating parameter includes a multiplication product of pressure of the working fluid, a swept volume of the working fluid, and a cycle frequency of the piston assembly, the maximum ratio being greater than or equal to 0.15. In one embodiment, the maximum ratio of power output from the connection member to the product of pressure of the working fluid, the swept volume of the working fluid, and the cycle frequency of the piston assembly is less than or equal to 0.35. 
     In one embodiment, the engine includes a second operating parameter defining a ratio of mechanical power output from the piston assembly to maximum cycle volume of the working fluid between 0.0005 and 0.0040 at an engine efficiency of at least 50%. 
     In various embodiments, the system includes a heater body configured to provide thermal energy to the engine working fluid at the plurality of heater conduits. The engine defines an outer end and an inner end each relative to a lateral extension of the piston assembly, and the outer end defines laterally distal ends of the engine and the inner end defines a laterally inward position of the engine, and the heater body is positioned at the outer end. In one embodiment, the system further includes a load device operably coupled to the piston assembly, in which the load device is positioned at the inner end of the system between the pistons of the piston assembly. 
     In one embodiment, the engine includes four or more piston assemblies. 
     In another embodiment, the system includes a third operating parameter defining a multiplication product of power density and efficiency between 51 and 400 kW/cubic meters. In one embodiment, the third operating parameter defines a multiplication product of power density and system efficiency between 51 and 400. In yet another embodiment, the third operating parameter defines a multiplication product of power density and Carnot efficiency of the system between 51 and 400. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure including the best mode, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
         FIG. 1.2 . 1  is a schematic block diagram depicting a system for energy conversion according to an aspect of the present disclosure; 
         FIG. 1.3 . 1  is a cross sectional view of an exemplary embodiment of a closed cycle engine and load device according to an aspect of the present disclosure; 
         FIG. 1.3 . 2  is a perspective cutaway view of an exemplary portion of an exemplary embodiment of an engine according to an aspect of the present disclosure; 
         FIG. 1.4 . 1  is a perspective cutaway view of an exemplary portion of an engine according to an aspect of the present disclosure; 
         FIG. 1.4 . 2  is a perspective cutaway view of another exemplary portion of a an engine according to an aspect of the present disclosure; 
         FIG. 1.4 . 3  is a cutaway view of a portion of an exemplary embodiment of an engine according to an aspect of the present disclosure; 
         FIG. 1.4 . 4  is a perspective view of a portion of an exemplary embodiment of an engine according to an aspect of the present disclosure; 
         FIG. 1.4 . 5  is a top-down view of fluid flowpaths within a portion of an exemplary embodiment of an engine such as provided in regard to  FIG. 1.4 . 4 ; 
         FIG. 1.4 . 6  is a bottom-up view of fluid flowpaths within a portion of an exemplary embodiment of an engine such as provided in regard to  FIG. 1.4 . 4 ; 
         FIG. 1.4 . 7  is a perspective cutaway view of a portion of an exemplary embodiment of an engine such as provided in regard to  FIG. 1.4 . 4 ; 
         FIG. 1.4 . 8  is a perspective view with a partial cutaway view of a portion of an exemplary embodiment of an engine according to an aspect of the present disclosure; 
         FIG. 1.5 . 1  is a perspective view of a portion of an exemplary embodiment of an engine such as provided according to an aspect of the present disclosure; 
         FIG. 1.6 . 1 A schematically depicts an exemplary regenerator system of an engine according to an aspect of the present disclosure; 
         FIG. 1.6 . 1 B schematically depicts a cross-sectional view of an exemplary regenerator body in relation to a portion of an engine according to an aspect of the present disclosure; 
         FIG. 1.6 . 1 C schematically depicts a top cross-sectional view of the exemplary regenerator body of  FIG. 1.6 . 1 B; 
         FIG. 1.6 . 1 D schematically depicts an enlarged perspective cross-sectional view of the exemplary regenerator body of  FIG. 1.6 . 1 B; 
         FIG. 1.7 . 1  is a side view of an exemplary embodiment of a portion of an engine according to an aspect of the present disclosure; 
         FIG. 1.7 . 2  is a perspective view of an exemplary embodiment of a portion of an engine such as provided in regard to  FIG. 1.7 . 1 ; 
         FIG. 1.7 . 3  is another perspective view of an exemplary embodiment of a portion of an engine such as provided in regard to  FIGS. 1.7 . 1  through  FIG. 1.7 . 2 ; and 
         FIG. 1.7 . 4  is an end view of an exemplary embodiment of a portion of an engine such as provided in regard to  FIGS. 1.7 . 1  through  FIG. 1.7 . 2 . 
     
    
    
     Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present disclosure. 
     DETAILED DESCRIPTION 
     Reference now will be made in detail to embodiments of the disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the disclosure and not limitation. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope of the disclosure. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. In another instance, ranges, ratios, or limits associated herein may be altered to provide further embodiments, and all such embodiments are within the scope of the present disclosure. Unless otherwise specified, in various embodiments in which a unit is provided relative to a ratio, range, or limit, units may be altered, and/or subsequently, ranges, ratios, or limits associated thereto are within the scope of the present disclosure. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
     As used herein, the terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. 
     The terms “upstream” and “downstream” refer to the relative direction with respect to fluid flow in a fluid pathway. For example, “upstream” refers to the direction from which the fluid flows, and “downstream” refers to the direction to which the fluid flows. The term “loop” can be any suitable fluid pathway along which fluid can flow and can be either open or closed, unless stated otherwise. 
     Power generation and distribution systems are generally challenged to reduce production inefficiencies, transmission losses, and emissions (e.g., oxides of nitrogen, sulfur, or carbon) during and post energy production. For example, the U.S. Energy Information Administration (EIA) estimates that electricity transmission and distribution (T&amp;D) losses average about 5% annually in the United States, with other estimates of line losses of 8% or higher. With average power plant efficiencies in the United States of about 30% to 40%, overall electrical efficiency at the end user (e.g., residences, businesses, etc.) is approximately 25% to 35%. Local, distributed, or on-demand power generation may not require access to T&amp;D networks or grids, such as to result in an at least 5% improvement in efficiency, in addition to reducing emission and adverse environmental impacts. 
     Heat engines and other devices for converting thermal energy into useful work are generally inefficient relative to their maximum theoretical efficiency. Carnot&#39;s theorem states that the maximum theoretical efficiency (η Carnot ) for an ideal, reversible heat engine is given by: 
     
       
         
           
             
               η 
               Carnot 
             
             = 
             
               1 
               - 
               
                 ( 
                 
                   
                     T 
                     
                       Hot 
                       , 
                       engine 
                     
                   
                   
                     T 
                     
                       Cold 
                       , 
                       ambient 
                     
                   
                 
                 ) 
               
             
           
         
       
     
     where T hot,engine  is the absolute temperature (e.g. in Rankine or Kelvin) at which heat enters the engine and T cold,ambient  is the absolute temperature of the environment into which the engine exhausts its waste heat. T Hot,engine  is generally limited by the maximum operating temperature of the materials in the engine and T Cold,ambient  is limited by an available heat sink available (e.g., the atmosphere at ambient temperature, the temperature of a body of water, etc.). Closed cycle heat engines operate through an exchange of thermal energy to and from relatively hot and cold volumes of a piston engine. Closed cycle heat engines, such as Stirling arrangements, or variations thereof, such as Franchot or Vuilleimier arrangements, generally have a maximum theoretical efficiency that is the Carnot efficiency. As such, closed cycle engines such as Stirling arrangements are considered to have a greater potential as high efficiency engines based at least on the difference in maximum theoretical efficiency and actual efficiency. 
     Achieving maximum theoretical efficiency of a system is challenged or limited based at least on inefficient combustion, inefficient heat exchange, heat losses to a surrounding environment, non-ideal behavior of one or more working fluids, friction losses, pumping losses, or other inefficiencies and imperfections, or energy required to operate the system. Actual or real thermal efficiency η th,system  of a system including a heat engine, heat generation sources, heat removal systems, or other heat exchangers, is given by: 
     
       
         
           
             
               
                 η 
                 
                   th 
                   , 
                   system 
                 
               
               ≡ 
               
                 
                   W 
                   out 
                 
                 
                   
                     Q 
                     in 
                   
                   + 
                   
                     E 
                     in 
                   
                   + 
                   
                     W 
                     in 
                   
                 
               
             
             = 
             
               
                 ( 
                 
                   
                     Q 
                     in 
                   
                   + 
                   
                     E 
                     in 
                   
                   + 
                   
                     
                       W 
                       in 
                     
                     ⁢ 
                     
                       E 
                       in 
                     
                   
                   + 
                   
                     Q 
                     in 
                   
                   - 
                   
                     ∑ 
                     
                       Q 
                       out 
                     
                   
                 
                 ) 
               
               
                 
                   Q 
                   in 
                 
                 + 
                 
                   E 
                   in 
                 
                 + 
                 
                   
                     W 
                     in 
                   
                   ⁢ 
                   
                     Q 
                     in 
                   
                 
               
             
           
         
       
     
     Actual or real thermal efficiency η th  of a heat engine is given by: 
     
       
         
           
             
               η 
               th 
             
             = 
             
               
                 
                   W 
                   out 
                 
                 
                   Q 
                   in 
                 
               
               = 
               
                 
                   
                     
                       Q 
                       in 
                     
                     - 
                     
                       Q 
                       out 
                     
                   
                   
                     Q 
                     in 
                   
                 
                 = 
                 
                   1 
                   - 
                   
                     
                       Q 
                       out 
                     
                     
                       Q 
                       in 
                     
                   
                 
               
             
           
         
       
     
     where W out  is the net useful work done by the engine, Q in  is the thermal energy received by the engine, and Q out  is the thermal energy lost or rejected to the environment. E in  is the electrical energy used by the system for operation of the system (e.g., fuel and/or oxidizer pumps, cooling sources, etc.). W in  is work input into the system. Achievable thermal efficiency tends to increase with power output. For example, motor vehicle applications are generally 20% to 35% thermally efficient, while large marine and stationary diesel systems can exceed 50% thermal efficiency ( FIG. 1.1 . 3 ). Stirling engines have demonstrated thermal efficiencies up to 38%. 
     The useful work generated by a heat engine can further be converted into electrical energy. The electrical efficiency (η El ) can be calculated in the same manner as the thermal efficiency: 
     
       
         
           
             
               η 
               El 
             
             = 
             
               
                 E 
                 out 
               
               
                 Q 
                 in 
               
             
           
         
       
     
     where E out  is the net electrical energy output from an electric machine that is operatively coupled to the engine and Q in  is the thermal energy received by the engine. E out  may be calculated by subtracting any electricity required to operate the power generation system from the gross power generated by the system. If combustion is the source of heating working fluid for the engine, the electrical efficiency may be calculated using a lower heating value (LHV) of the fuel. Stirling engines have demonstrated LHV electrical efficiencies between 10% and 30%. 
     Closed cycle engines, such as Stirling arrangements, are challenged to produce increasing levels of power output and power density, and generally compromise improved efficiency or power output with larger sizes and scaling. Such larger sizes or scales can negate other desirable qualities of the engine, such as relatively small-scale or portability. 
     Stirling engines may generally include two types: kinematic or free piston. Kinematic Stirling engines use mechanically-connected piston assemblies to transmit and convert linear motion of the pistons to a rotary motion for an output shaft. Although such systems may address issues regarding power transmission and stability of the engine, mechanically-connected piston assemblies introduce relatively large power losses via the mechanical members. Additionally, or alternatively, the relatively fixed relationship of mechanically-connected piston assemblies limits the mechanical stroke of the piston assembly. As such, the efficiency of mechanically-connected multi-piston assemblies in a closed cycle engine is decreased in addition to mechanical losses (e.g., friction, leakage, inertia, etc.). 
     Single-piston free piston closed cycle engine arrangements generally exchange improved thermal efficiency for lower total power generation and density. As such, single-piston free piston closed cycle engine arrangements are not generally suited for higher power output applications. 
     Multi-piston free piston closed cycle engine arrangements may provide thermal efficiencies of single-piston free piston arrangements and further increase total power generation. However, multi-piston free piston arrangements generally differ from single-piston arrangements and mechanically-connected multi-piston arrangements in that the cycle or motion of a multi-piston free piston arrangement is generally determined by thermo-mechanical interactions of the entire system including the free pistons, the thermal source(s), and a power extraction apparatus. The thermo-mechanical interactions may further include mechanical losses and their effect on balance of the entire system. 
     For example, multi-piston free-piston closed cycle engines are challenged to respond to time lags. As another example, if one piston assembly drifts from an intended position a subsequent oscillation can become unbalanced. An unbalanced arrangement may lead to undesired vibrations, crashing of the pistons to end walls, or other mechanical losses that may further reduce power output, induce wear and deterioration, or otherwise reduce efficient, stable, or effective use of a multi-piston free piston engine. 
     As such, there is a need for improved closed cycle engines such as Stirling engines that provide improved power generation efficiency and output. Additionally, there is a need for such improved closed cycle engines that may further retain or improve power density, such as to provide relatively small-scale or portability such as to provide improved application to power generation and distribution systems. 
     Referring now to  FIG. 1.2 . 1 , an exemplary schematic block diagram depicting a system for energy conversion (hereinafter, “system A 10 ”) is provided. Various embodiments of the system A 10  provided herein include systems for power generation, a heat recovery system, a heat pump or cryogenic cooler, a system including and/or acting as a bottoming cycle and/or a topping cycle, or other system for producing useful work or energy, or combinations thereof. Referring additionally for  FIG. 1.3 . 1 , various embodiments of the system A 10  include a closed cycle engine apparatus (hereinafter, “engine A 100 ”, apparatus “A 100 ”, or otherwise denoted herein) operably coupled to a load device C 092 . The engine A 100  contains a substantially fixed mass of an engine working fluid to which and from which thermal energy is exchanged at a respective cold side heat exchanger A 42  and a hot side heat exchanger C 108 . In one embodiment, the engine working fluid is helium. In other embodiments, the engine working fluid may include air, nitrogen, hydrogen, helium, or any appropriate compressible fluid, or combinations thereof. In still various embodiments, any suitable engine working fluid may be utilized in accordance with the present disclosure. In exemplary embodiments, the engine working fluid may include a gas, such as an inert gas. For example, a noble gas, such as helium may be utilized as the engine working fluid. Exemplary working fluids preferably are inert, such that they generally do not participate in chemical reactions such as oxidation within the environment of the engine. Exemplary noble gasses include monoatomic gases such as helium, neon, argon, krypton, or xenon, as well as combinations of these. In some embodiments, the engine working fluid may include air, oxygen, nitrogen, or carbon dioxide, as well as combinations of these. In still various embodiments, the engine working fluid may be liquid fluids of one or more elements described herein, or combinations thereof. It should further be appreciated that various embodiments of the engine working fluid may include particles or other substances as appropriate for the engine working fluid. 
     In various embodiments, the load device C 092  is a mechanical work device or an electric machine. In one embodiment, the load device C 092  is a pump, compressor, or other work device. In another embodiment, the load device C 092  as an electric machine is configured as a generator producing electric energy from movement of a piston assembly A 1010  at the engine. In still another embodiment, the electric machine is configured as a motor providing motive force to move or actuate the piston assembly A 1010 , such as to provide initial movement (e.g., a starter motor). In still various embodiments, the electric machine defines a motor and generator or other electric machine apparatus such as described further herein. 
     A heater body C 100  is thermally coupled to the engine A 100 . The heater body C 100  may generally define any apparatus for producing or otherwise providing a heating working fluid such as to provide thermal energy to the engine working fluid. Various embodiments of the heater body C 100  are further provided herein. Exemplary heater bodies C 100  may include, but are not limited to, a combustion or detonation assembly, an electric heater, a nuclear energy source, a renewable energy source such as solar power, a fuel cell, a heat recovery system, or as a bottoming cycle to another system. Exemplary heater bodies C 100  at which a heat recovery system may be defined include, but are not limited to, industrial waste heat generally, gas or steam turbine waste heat, nuclear waste heat, geothermal energy, decomposition of agricultural or animal waste, molten earth or metal or steel mill gases, industrial drying systems generally or kilns, or fuel cells. The exemplary heater body C 100  providing thermal energy to the engine working fluid may include all or part of a combined heat and power cycle, or cogeneration system, or power generation system generally. 
     In still various embodiments, the heater body C 100  is configured to provide thermal energy to the engine working fluid via a heating working fluid. The heating working fluid may be based, at least in part, on heat and liquid, gaseous, or other fluid provided by one or more fuel sources and oxidizer sources providing a fuel and oxidizer. In various embodiments, the fuel includes, but is not limited to, hydrocarbons and hydrocarbon mixtures generally, “wet” gases including a portion of liquid (e.g., humid gas saturated with liquid vapor, multiphase flow with approximately 10% liquid and approximately 90% gas, natural gas mixed with oil, or other liquid and gas combinations, etc.), petroleum or oil (e.g., Arabian Extra Light Crude Oil, Arabian Super Light, Light Crude Oil, Medium Crude Oil, Heavy Crude Oil, Heavy Fuel Oil, etc.), natural gas (e.g., including sour gas), biodiesel condensate or natural gas liquids (e.g., including liquid natural gas (LNG)), dimethyl ether (DME), distillate oil #2 (DO2), ethane (C 2 ), methane, high H 2  fuels, fuels including hydrogen blends (e.g., propane, butane, liquefied petroleum gas, naphtha, etc.), diesel, kerosene (e.g., jet fuel, such as, but not limited to, Jet A, Jet A-1, JP1, etc.), alcohols (e.g., methanol, ethanol, etc.), synthesis gas, coke over gas, landfill gases, etc., or combinations thereof. 
     In various embodiments, the system A 10  includes a working fluid body C 108 , such as further described herein. In one embodiment, the working fluid body C 108  defines a hot side heat exchanger A 160 , such as further described herein, from which thermal energy is output to the engine working fluid at an expansion chamber A 221  of the engine. The working fluid body C 108  is positioned at the expansion chamber A 221  of the engine in thermal communication with the heater body C 100 . In other embodiments, the working fluid body C 108  may be separate from the heater body C 100 , such that the heating working fluid is provided in thermal communication, or additionally, in fluid communication with the working fluid body C 108 . In particular embodiments, the working fluid body C 108  is positioned in direct thermal communication with the heater body C 100  and the expansion chamber A 221  of the engine A 100  such as to receive thermal energy from the heater body C 100  and provide thermal energy to the engine working fluid within the engine. 
     In still various embodiments, the heater body C 100  may include a single thermal energy output source to a single expansion chamber A 221  of the engine. As such, the system A 10  may include a plurality of heater assemblies each providing thermal energy to the engine working fluid at each expansion chamber A 221 . In other embodiments, such as depicted in regard to  FIG. 1.3 . 1 , the heater body C 100  may provide thermal energy to a plurality of expansion chambers A 221  of the engine. In still other embodiments, such as depicted in regard to  FIG. 8 , the heater body includes a single thermal energy output source to all expansion chambers A 221  of the engine. 
     The system A 10  further includes a chiller assembly, such as chiller assembly A 40  further described herein. The chiller assembly A 40  is configured to receive and displace thermal energy from a compression chamber A 222  of the engine. The system A 10  includes a cold side heat exchanger A 42  thermally coupled to the compression chamber A 222  of the closed cycle engine and the chiller assembly. In one embodiment, the cold side heat exchanger A 42  and the piston body C 700  defining the compression chamber A 222  of the engine are together defined as an integral, unitary structure, such as further shown and described in regard to  FIGS. 1.4 . 1 - 1 . 4 . 7 . In still various embodiments, the cold side heat exchanger A 42 , at least a portion of the piston body C 700  defining the compression chamber A 222 , and at least a portion of the chiller assembly together define an integral, unitary structure. 
     In various embodiments, the chiller assembly A 40  is a bottoming cycle to the engine A 100 . As such, the chiller assembly A 40  is configured to receive thermal energy from the engine A 100 . The thermal energy received at the chiller assembly A 40 , such as through a cold side heat exchanger A 42 , or cold side heat exchanger A 170  further herein, from the engine A 100  is added to a chiller working fluid at the chiller assembly A 40 . In various embodiments, the chiller assembly A 40  defines a Rankine cycle system through which the chiller working fluid flows in closed loop arrangement with a compressor. In some embodiments, the chiller working fluid is further in closed loop arrangement with an expander. In still various embodiments, the system A 10  includes a heat exchanger A 88  ( FIG. 1.3 . 2 ). In various embodiments, the heat exchanger A 188  may include a condenser or radiator. The cold side heat exchanger A 40  is positioned downstream of the compressor and upstream of the expander and in thermal communication with a compression chamber A 222  of the closed cycle engine, such as further depicted and described in regard to  FIG. 1.3 . 1 - FIG. 1.3 . 2 . In various embodiments, the cold side heat exchanger A 42  may generally define an evaporator receiving thermal energy from the engine A 40 . 
     Referring still to  FIG. 1.2 . 1 , in some embodiments, the heat exchanger A 188  is positioned downstream of the expander and upstream of the compressor and in thermal communication with a cooling working fluid. In the schematic block diagram provided in  FIG. 1.2 . 1 , the cooling working fluid is an air source. However, in various embodiments, the cooling fluid may define any suitable fluid in thermal communication with the heat exchanger. The heat exchanger may further define a radiator configured to emit or dispense thermal energy from the chiller assembly A 40 . A flow of cooling working fluid from a cooling fluid source is provided in thermal communication with the heat exchanger to further aid heat transfer from the chiller working fluid within the chiller assembly A 40  to the cooling working fluid. 
     As further described herein, in various embodiments the chiller assembly A 40  may include a substantially constant density heat exchanger. The constant density heat exchanger generally includes a chamber including an inlet and an outlet each configured to contain or trap a portion of the chiller working fluid for a period of time as heat from the closed cycle engine is transferred to the cold side heat exchanger A 42 . In various embodiments, the chamber may define a linear or rotary chamber at which the inlet and the outlet are periodically opened and closed via valves or ports such as to trap the chiller working fluid within the chamber for the desired amount of time. In still various embodiments, the rate at which the inlet and the outlet of the chamber defining the constant density heat exchanger is a function at least of velocity of a particle of fluid trapped within the chamber between the inlet and the outlet. The chiller assembly A 40  including the constant density heat exchanger may provide efficiencies, or efficiency increases, performances, power densities, etc. at the system A 10  such as further described herein. 
     It should be appreciated that in other embodiments, the chiller assembly A 40  of the system A 10  may include a thermal energy sink generally. For example, the chiller assembly A 40  may include a body of water, the vacuum of space, ambient air, liquid metal, inert gas, etc. In still various embodiments, the chiller working fluid at the chiller assembly A 40  may include, but is not limited to, compressed air, water or water-based solutions, oil or oil-based solutions, or refrigerants, including, but not limited to, class 1, class 2, or class 3 refrigerants. Further exemplary refrigerants may include, but are not limited to, a supercritical fluid including, but not limited to, carbon dioxide, water, methane, ethane, propane, ethylene, propylene, methanol, ethanol, acetone, or nitrous oxide, or combinations thereof. Still exemplary refrigerants may include, but are not limited to, halon, perchloroolefin, perchlorocarbon, perfluoroolefin, perfluororcarbon, hydroolefin, hydrocarbon, hydrochloroolefin, hydrochlorocarbon, hydrofluoroolefin, hydrofluorocarbon, hydrochloroolefin, hydrochlorofluorocarbon, chlorofluoroolefin, or chlorofluorocarbon type refrigerants, or combinations thereof. Still further exemplary embodiments of refrigerant may include, but are not limited to, methylamine, ethylamine, hydrogen, helium, ammonia, water, neon, nitrogen, air, oxygen, argon, sulfur dioxide, carbon dioxide, nitrous oxide, or krypton, or combinations thereof. 
     It should be appreciated that where combustible or flammable refrigerants are included for the chiller working fluid, various embodiments of the system A 10  may beneficially couple the heater body C 100 , and/or the fuel source, and the chiller assembly A 40  in fluid communication such that the combustible or flammable working fluid to which thermal energy is provided at the chiller assembly A 40  may further be utilized as the fuel source for generating heating working fluid, and the thermal energy therewith, to output from the heater body C 100  to the engine working fluid at the engine A 100 . 
     Various embodiments of the system A 10  include control systems and methods of controlling various sub-systems disclosed herein, such as, but not limited to, the fuel source, the oxidizer source, the cooling fluid source, the heater body C 100 , the chiller assembly C 40 , the engine A 100 , and the load device C 092 , including any flow rates, pressures, temperatures, loads, discharges, frequencies, amplitudes, or other suitable control properties associated with the system A 10 . In one aspect, a control system for the system A 10  defining a power generation system is provided. The power generation system includes one or more closed cycle engines (such as engine A 100 ), one or more load devices defining electric machines (such as load device C 092 ) operatively coupled to the engine, and one or more energy storage devices in communication with the electric machines. 
     The control system can control the closed cycle engine and its associated balance of plant to generate a temperature differential, such as a temperature differential at the engine working fluid relative to the heating working fluid and the chiller working fluid. Thus, the engine defines a hot side, such as at the expansion chamber A 221 , and a cold side, such as at the compression chamber A 222 . The temperature differential causes free piston assemblies A 1010  to move within their respective piston chambers defined at respective piston bodies C 700 . The movement of the pistons A 1011  causes the electric machines to generate electrical power. The generated electrical power can be provided to the energy storage devices for charging thereof. The control system monitors one or more operating parameters associated with the closed cycle engine, such as piston movement (e.g., amplitude and position), as well as one or more operating parameters associated with the electric machine, such as voltage or electric current. Based on such parameters, the control system generates control commands that are provided to one or more controllable devices of the system A 10 . The controllable devices execute control actions in accordance with the control commands. Accordingly, the desired output of the system A 10  can be achieved. 
     Furthermore, the control system can monitor and anticipate load changes on the electric machines and can control the engine A 100  to anticipate such load changes to better maintain steady state operation despite dynamic and sometimes significant electrical load changes on the electric machines. A method of controlling the power generation system is also provided. In another aspect, a control system for a heat pump system is provided. The heat pump system includes one or more of the closed cycle engines described herein. A method of controlling the heat pump system is also provided. The power generation and heat pump systems as well as control methods therefore are provided in detail herein. 
     Referring now to  FIG. 1.3 . 1 - FIG. 1.3 . 2 , exemplary embodiments of the system A 10  are further provided.  FIG. 1.3 . 1  is an exemplary cross sectional view of the system A 10  including the heater body C 100  and the chiller assembly A 40  each in thermal communication with the engine A 100 , or particularly the engine working fluid within the engine A 100 , such as shown and described according to the schematic block diagram of  FIG. 1.2 . 1 .  FIG. 1.3 . 2  is an exemplary cutaway perspective view of a portion of the engine A 100 . The system A 10  includes a closed cycle engine A 100  including a piston assembly A 1010  positioned within a volume or piston chamber C 112  defined by a wall defining a piston body C 700 . The volume within the piston body C 700  is separated into a first chamber, or hot chamber, or expansion chamber A 221  and a second chamber, or cold chamber (relative to the hot chamber), or compression chamber A 222  by a piston A 1011  of the piston assembly A 1010 . The expansion chamber A 221  is positioned thermally proximal to the heater body C 100  relative to the compression chamber A 222  thermally distal to the heater body C 100 . The compression chamber A 222  is positioned thermally proximal to the chiller assembly A 40  relative to the expansion chamber A 221  thermally distal to the chiller assembly A 40 . 
     In various embodiments, the piston assembly A 1010  defines a double-ended piston assembly A 1010  in which a pair of pistons A 1011  is each coupled to a connection member A 1030 . The connection member A 1030  may generally define a rigid shaft or rod extended along a direction of motion of the piston assembly A 1010 . In other embodiments, the connection members A 1030  includes one or more springs or spring assemblies, such as further provided herein, providing flexible or non-rigid movement of the connection member A 1030 . In still other embodiments, the connection member A 1030  may further define substantially U- or V-connections between the pair of pistons A 1011 . 
     Each piston A 1011  is positioned within the piston body C 700  such as to define the expansion chamber A 221  and the compression chamber A 222  within the volume of the piston body C 700 . The load device c 092  is operably coupled to the piston assembly A 1010  such as to extract energy therefrom, provide energy thereto, or both. The load device c 092  defining an electric machine is in magnetic communication with the closed cycle engine via the connection member A 1030 . In various embodiments, the piston assembly A 1010  includes a dynamic member A 181  positioned in operable communication with a stator assembly A 182  of the electric machine. The stator assembly A 182  may generally include a plurality of windings wrapped circumferentially relative to the piston assembly A 1010  and extended along a lateral direction L. In one embodiment, such as depicted in regard to  FIG. 1.3 . 1 , the dynamic member A 181  is connected to the connection member A 1030 . The electric machine may further be positioned between the pair of pistons A 1011  of each piston assembly A 1010 . Dynamic motion of the piston assembly A 1010  generates electricity at the electric machine. For example, linear motion of the dynamic member A 181  between each pair of chambers defined by each piston A 1011  of the piston assembly A 1010  generates electricity via the magnetic communication with the stator assembly A 182  surrounding the dynamic member A 181 . 
     Referring to  FIG. 1.3 . 1 - FIG. 1.3 . 2 , in various embodiments, the working fluid body C 108  may further define at least a portion of the expansion chamber A 221 . In one embodiment, such as further described herein, the working fluid body C 108  defines a unitary or monolithic structure with at least a portion of the piston body C 700 , such as to define at least a portion of the expansion chamber A 221 . In some embodiments, the heater body C 100  further defines at least a portion of the working fluid body C 108 , such as to define a unitary or monolithic structure with the working fluid body C 108 , such as further described herein. In one embodiment, such as further shown and described in regard to  FIG. 1.5 . 1 , the system A 10  includes the hot side heat exchanger or working fluid body C 108  positioned between the heater body C 100  and the expansion chamber A 221  of the piston body C 700 . In various embodiments, such as further shown and described in regard to  FIG. 1.5 . 1 , the working fluid body C 108  includes a plurality of heater conduits or working fluid pathways C 110  extended from the expansion chamber A 221 . 
     The engine A 100  defines an outer end A 103  and an inner end A 104  each relative to a lateral direction L. The outer ends A 103  define laterally distal ends of the engine A 100  and the inner ends  104  define laterally inward or central positions of the engine A 100 . In one embodiment, such as depicted in regard to  FIG. 1.3 . 1 - FIG. 1.3 . 2 , the heater body C 100  is positioned at outer ends A 103  of the system A 10 . The piston body C 700  includes a dome structure A 26  at the expansion chamber A 221 . The expansion chamber dome structure A 26  provides reduced surface area heat losses across the outer end A 103  of the expansion chamber A 221 . In various embodiments, the pistons A 1011  of the piston assembly A 1010  further include domed pistons A 1011  corresponding to the expansion chamber A 221  dome. The dome structure A 26 , the domed piston A 1011 , or both may provide higher compressions ratios at the chambers A 221 , A 222 , such as to improve power density and output. 
     The chiller assembly A 40  is positioned in thermal communication with each compression chamber A 222 . Referring to  FIG. 1.3 . 1 - FIG. 1.3 . 2 , the chiller assembly A 40  is positioned inward along the lateral direction L relative to the heater body C 100 . In one embodiment, the chiller assembly A 40  is positioned laterally between the heater body C 100  and the load device c 092  along the lateral direction L. The chiller assembly A 40  provides the chiller working fluid in thermal communication with the engine working fluid at the cold side heat exchanger A 42  and/or compression chamber A 222 . In various embodiments, the piston body C 700  defines the cold side heat exchanger A 42  between an inner volume wall A 46  and an outer volume wall A 48  surrounding at least the compression chamber A 222  portion of the piston body C 700 . 
     In various embodiments, such as depicted in regard to  FIG. 1.3 . 1 - FIG. 1.3 . 2 , the load device c 092  is positioned at the inner end A 104  of the system A 10  between laterally opposing pistons A 1011 . The load device c 092  may further include a machine body c 918  positioned laterally between the piston bodies C 700 . The machine body c 918  surrounds and houses the stator assembly A 182  of the load device c 092  defining the electric machine. The machine body c 918  further surrounds the dynamic member A 181  of the electric machine attached to the connection member A 1030  of the piston assembly A 1010 . In various embodiments, such as depicted in regard to  FIG. 1.3 . 1 - FIG. 1.3 . 2 , the machine body c 918  further provides an inner end wall A 50  at the compression chamber A 222  laterally distal relative to the expansion chamber A 221  dome. 
     Referring now to  FIG. 1.4 . 1 - FIG. 1.4 . 7 , exemplary embodiments of a portion of the piston body C 700 , cold side heat exchanger A 42 , and chiller assembly A 40  are provided. In various embodiments, the system A 10  includes the cold side heat exchanger A 42  further including a plurality of chiller conduits A 54  each defining chiller passages A 56  providing fluid communication of the engine working fluid through the chiller conduit A 54  and the compression chamber A 222 . The piston body C 700  includes the outer volume wall A 48  and an inner volume wall A 46  each separated along a radial direction R perpendicular to the lateral direction L. Each volume wall A 46 , A 48  may be defined at least partially circumferentially relative to a piston body centerline A 12  extended through each piston body C 700 . 
     In the embodiments depicted in the perspective cutaway views of  FIGS. 1.4 . 1 - 1 . 4 . 2 , each volume wall A 46 , A 48  is extended along the lateral direction L. The outer volume wall A 48  surrounds the plurality of chiller conduits A 54 . The plurality of chiller conduits A 54  is positioned between the outer volume wall A 48  and the inner volume wall A 46 . The cold side heat exchanger A 42  further includes a chamber wall A 52  extended between the outer volume wall A 48  and the inner volume wall A 46 . The chamber wall A 52 , the outer volume wall A 48 , and the inner volume wall A 46  together define a chiller working fluid passage A 66  surrounding the plurality of chiller conduits A 54 . The chiller conduits A 54  define walled manifolds fluidly separating the chiller passage A 56  (i.e., the passage through which the engine working fluid flows) and the chiller working fluid passage A 66  (i.e., the passage through which the chiller working fluid flows). As such, the chiller working fluid flowing through the chiller working fluid passage A 66  is fluidly separated from the engine working fluid flowing through the chiller conduits A 54 . Additionally, the chiller working fluid flowing through the chiller working fluid passage A 66  is in thermal communication with the engine working fluid flowing through the chiller conduits A 54 . 
     In various embodiments, the chamber wall A 52  is extended between the volume walls at an acute angle relative to the lateral direction L along which the piston assembly A 1010  is extended. In one embodiment, the chamber wall A 52  is extended between 0 degrees and approximately 90 degrees relative to the lateral direction L. In another embodiment, the chamber wall A 52  is extended between 30 degrees and approximately 60 degrees relative to the lateral direction L along which the volume walls A 46 , A 48  are substantially extended. In yet another embodiment, the chamber wall A 52  is extended approximately 45 degrees relative to the lateral direction L. The chamber wall A 52  is further connected to the outer volume wall A 48 , the inner volume wall A 46 , and the chiller conduits A 54  such as to provide support to one another. The chamber walls A 52  extended along an acute angle may further provide advantageous placement of the chiller conduits A 54  within the chiller working fluid passage A 66  such as to promote thermal energy transfer from the engine working fluid to the chiller working fluid. 
     During operation of the engine A 100 , a portion of the engine working fluid is admitted from the compression chamber A 222  into the plurality of chiller conduits A 54  via the plurality of chiller passage openings A 58 . The chiller passage opening A 58  is defined at a fluid interface of the chiller conduit A 54  to the compression chamber A 222 . In various embodiments, the chiller passage opening A 58  provides direct fluid communication with the compression chamber A 222 . In one embodiment, a distance between the compression chamber A 222  of the engine and the cold side heat exchanger A 42 , or particularly the plurality of chiller conduits A 54  in direct thermal communication with the chiller working fluid, is substantially zero. Stated differently, the distance from the compression chamber A 222  to the chiller conduits A 54  in direct thermal communication with the chiller working fluid (i.e., the chiller working fluid is fluidly contacting an outer wall of the chiller conduits A 54  such as to provide direct thermal communication to the engine working fluid within the chiller conduit A 54 ) is the thickness of the chamber wall A 52  through which the plurality of chiller passage openings A 58  is defined. A distance between the compression chamber A 222  and the cold side heat exchanger A 42  beyond or greater than the thickness of the chamber wall A 52  is approximately zero. 
     Still further, during operation of engine A 100 , the compression stroke of the piston assembly A 1010  may generally push the engine working fluid through the chiller conduits A 54 . The engine working fluid within chiller passages A 56  in the chiller conduits A 54  is in thermal communication with the chiller working fluid surrounding the chiller conduits A 54  within the chiller working fluid passage A 66 . The expansion stroke of the piston assembly A 1010  may generally pull the engine working fluid through the chiller conduits A 54  such as to egress the engine working fluid from the chiller conduits A 54  through the chiller passage openings A 58  and into the compression chamber A 222 . As further described herein, the chiller working fluid passage A 66  is in fluid communication with a chiller working fluid outlet opening A 78  and a chiller working fluid outlet opening A 80  together providing flow of the chiller working fluid such as to remove and displace thermal energy from the engine working fluid at the chiller conduits A 54 . As still further described herein, the chiller working fluid passage A 66 , the chiller working fluid outlet opening A 78 , and/or the chiller working fluid output may form a circuit of the chiller assembly at which thermal energy from the engine working fluid at the compression chamber A 222  is released from the closed cycle engine. 
     An outer chamber wall A 53  and at least one chamber wall A 52  may together define a chiller collection chamber A 62  at which the engine working fluid may egress the plurality of chiller conduits A 54  and collect into a volume. The outer chamber wall A 53  defines a plurality of chiller collection chamber openings A 60  each corresponding to a respective chiller conduit A 54  and chiller passage opening A 58 . As further described herein in regard to  FIGS. 1.4 . 5 - 1 . 4 . 7  and  FIGS. 1.7 . 1 - FIG. 1.7 . 4 , the chiller collection chamber A 62  is further in fluid communication with a walled conduit A 1050  such as to provide fluid communication between the compression chamber A 222  of one piston assembly A 1010  and the expansion chamber A 221  of another piston assembly A 1010 . 
     In various embodiments, the compression chamber A 222  of one piston assembly A 1010  is fluidly connected to the expansion chamber A 221  of another piston assembly A 1010  via the walled conduit A 1050  to provide a balanced pressure and/or balanced phase fluid coupling arrangement of the plurality of chambers A 221 , A 222 . An interconnected volume of chambers including the expansion chamber A 221  of one piston assembly A 1010  and the compression chamber A 222  of another piston assembly A 1010  defines a fluid interconnection of the chambers A 221 , A 222  at different piston assemblies A 1010 . The fluid interconnection of chambers A 221 , A 222  at different piston assemblies is such that if there is any fluid communication or fluid leakage path between the expansion chamber A 221  and the compression chamber A 222  of the same piston assembly A 1010 , a single fluid loop of connected chambers A 221 , A 222  is provided that is separated from the chambers A 221 , A 222  outside of the interconnected volume of chambers. In one embodiment, the balanced pressure arrangement, or additionally, the balance phase arrangement, of the piston assemblies A 1010  is the fluid interconnection of the walled conduits A 1050  and the chambers A 221 , A 222  such that the chambers within the interconnected volume are substantially fluidly and/or pneumatically separated from those outside of the interconnected volume to provide a substantially equal and opposite force relative to one another to at least one piston assembly A 1010  when the engine working fluid within the chambers A 221 , A 222  is at a uniform temperature. Stated differently, when one piston assembly A 1010  is articulated, such as along the lateral direction L, the fluid interconnection of chambers A 221 , A 222  via the walled conduit A 1050  provides a substantially net zero force at another piston assembly A 1010  when the engine working fluid is at a substantially uniform temperature. As such, when one piston assembly A 1010  is articulated under such conditions, adjacent or other piston assemblies A 1010  remain stationary due at least to the net zero force at the piston assembly A 1010 . In various embodiments, the substantially uniform temperature is defined when no heat input or thermal energy is provided from the heater body C 100  or working fluids body C 108  to the engine working fluid. 
     Referring now to  FIG. 1.4 . 3 , a side cutaway view of an embodiment of a pair of piston bodies C 700  is provided. The embodiment depicted in regard to  FIG. 1.4 . 3  is configured substantially similarly as shown and described in regard to  FIGS. 1.4 . 1 - 1 . 4 . 2 .  FIG. 1.4 . 3  further provides a partial cutaway view within the piston body C 700  exposing a portion of the plurality of chiller conduits A 54  between the volume walls A 46 , A 48 . In various embodiments, the chiller conduit A 54  extends along the lateral direction L between the chiller passage opening A 58  and the chiller collection chamber A 62 . In one embodiment, the chiller conduit A 54  extends at least partially along an oblique or orthogonal direction relative to the lateral direction L. In various embodiments, the chiller conduit A 54  extends substantially circumferentially around the piston body C 700 . The chiller conduit A 54  may extend at least partially along the oblique or orthogonal direction relative to the lateral direction L such as to desirably increase a surface area of the chiller passage A 56  defined within the chiller conduit A 54  at which the engine working fluid is in thermal communication with the chiller working fluid in the cold side heat exchanger A 42 . The desirable increase in surface area of the chiller passage A 56  defined by the chiller conduit A 54  provides the surrounding chiller working fluid in the first and second chiller working fluid passage A 68 , A 70  to be in thermal communication so as to improve the opportunity for the transfer of thermal energy from the engine working fluid to the chiller working fluid. In one embodiment, the surface area over which the engine working fluid is desirably in thermal communication with the surrounding chiller working fluid is desirably adjusted by adjusting the lateral, circumferential, or orthogonal extension of the chiller conduits A 54  such as to adjust the heat exchanging surface area of the chiller passage A 56 . In one embodiment, the chiller conduit A 54  may extend at least partially in a curved or circumferential or spiral direction, such as a helix, between the chiller passage opening A 58  and the chiller collection chamber A 62 . In another embodiment, the chiller conduit A 54  may extend in a zig-zag or serpentine pattern between the chiller passage opening A 58  and the chiller collection chamber A 62 . However, it should be appreciated that other geometries may be defined such as to produce the desired heat exchanging surface area of the chiller conduit A 54  relative to the chiller working fluid passage A 66 . 
     It should be appreciated that in various embodiments the surface area of the chiller passage A 56  defined within each chiller conduit A 54  described herein corresponds to the chiller passage A 56 , such as an internal wall or surface of the chiller conduit A 54  at which the engine working fluid is in direct contact. In one embodiment, the surface area defines a nominal surface area of the chiller passage A 56 , such as a cross section of the chiller conduit A 54 . In other embodiments, features may be added or altered to the chiller passage A 56  within the chiller conduit A 54 , such as, but not limited to, surface roughness, protuberances, depressions, spikes, nodules, loops, hooks, bumps, burls, clots, lumps, knobs, projections, protrusions, swells, enlargements, outgrowths, accretions, blisters, juts, and the like, or other raised material, or combinations thereof, to desirably alter flow rate, pressure drop, heat transfer, flow profile or fluid dynamics of the engine working fluid. 
     Referring still to  FIG. 1.4 . 3 , various embodiments further include a connecting chiller conduit A 72  extended between the first piston body C 700  and the second piston body C 700 . The connecting chiller conduit A 72  provides fluid communication of the chiller working fluid between two or more piston bodies C 700 . In various embodiments, the chiller working fluid passage A 66  at each piston body C 700  includes a first chiller working fluid passage A 68  and a second chiller working fluid passage A 70  each in thermal communication with the compression chamber A 222 . The second chiller working fluid passage A 70  is positioned proximal to the chiller passage opening A 58  at the compression chamber A 222 . The first chiller working fluid passage A 68  is positioned distal to the chiller passage opening A 58  at the compression chamber A 222 . Additionally, or alternatively, the first chiller working fluid passage A 68  is positioned proximal to the chiller collection chamber A 62  or the expansion chamber A 221 . The connecting chiller conduit A 72  is configured to fluidly connect the first chiller working fluid passage A 68  of one piston body C 700  (e.g., the first piston body  82 ) to the second chiller working fluid passage A 70  of another piston body C 700  (e.g., the second piston body  84 ), such as further depicted in the embodiments in regard to  FIGS. 1.4 . 4 - 1 . 4 . 7 . As further shown and described in regard to  FIGS. 1.4 . 4 - 1 . 4 . 7  and  FIGS. 1.7 . 1 - FIG. 1.7 . 4 , the chiller working fluid may enter the chiller assembly A 40  and flow at the first chiller working fluid passage A 68  of one piston body C 700  and the second chiller working fluid passage A 70  of another piston body C 700 . Stated differently, in various embodiments, the chiller working fluid may enter the chiller assembly A 40  and flow in thermal communication with a generally hotter portion of one piston body C 700  (i.e., proximate along the lateral direction L to the expansion chamber A 221 ) and engine working fluid positioned proximal to the hot or expansion chamber A 221 . The chiller working fluid may then flow to another piston body C 700  to a portion distal to the hot or expansion chamber A 221  of the other piston body C 700 , such as may be generally cooler relative to first piston body C 700 . 
     Referring now to  FIG. 1.4 . 4 , a perspective view of an exemplary embodiment of a portion of the engine A 100  is provided. Referring additionally to  FIGS. 1.4 . 5 - 1 . 4 . 6 , further embodiments of the portion of the engine A 100  are provided.  FIG. 1.4 . 4  includes a partial cutaway view within the piston body C 700  exposing chiller conduits A 54  between the volume walls A 46 , A 48 .  FIG. 1.4 . 4  depicts at least a pair of the piston bodies C 700  including the connecting chiller conduit A 72  such as to provide fluid communication and thermal communication from the first chiller working fluid passage A 68  of the first piston body C 700  to the second chiller working fluid passage A 70  of the second piston body C 700 . Additionally, the second piston body C 700  includes the connecting chiller conduit A 72  providing fluid communication and thermal communication from the first chiller working fluid passage A 68  of the second piston body C 700  to another adjacent second chiller working fluid passage A 70  of another adjacent piston body C 700  different from the first piston body C 700  and the second piston body C 700 . 
     Referring to  FIG. 1.4 . 5 , a top-down view of an exemplary embodiment of the portion of the engine depicted in  FIG. 1.4 . 4  is provided. Referring additionally to  FIG. 1.4 . 6 , a bottom-up view of an exemplary embodiment of the portion of the engine depicted in  FIG. 1.4 . 4  is provided. Referring to  FIGS. 1.4 . 5 - 1 . 4 . 6 , the embodiments further depict the connecting chiller conduit A 72  extended between pairs of the piston body C 700 . In one embodiment, such as depicted in regard to  FIGS. 1.4 . 5 - 1 . 4 . 6 , the engine includes a chiller working fluid inlet opening A 78  through which chiller working fluid is provided to the chiller working fluid passage A 66 . The chiller working fluid inlet opening A 78  may be positioned generally inward within the engine or proximal to the reference longitudinal axis C 204 . Referring to  FIG. 1.4 . 6 , in one embodiment, the chiller working fluid passage A 66  may define a flowpath from the chiller working fluid inlet opening A 78  and at least partially around one piston body C 700 . The flowpath may further extend across the connecting chiller conduit A 72  to another or second piston body  84  adjacent or next to the first piston body  82 . The flowpath of the chiller working fluid passage A 66  further extends substantially circumferentially around the other piston body C 700  (e.g., depicted at the second piston body C 700 ). The flowpath is in fluid communication with a chiller working fluid outlet opening A 80 . In various embodiments, the chiller working fluid outlet opening A 80  is positioned outward or distal from the reference longitudinal axis C 204 . 
     In various embodiments, the flowpath of the chiller working fluid passage A 66  extends from the chiller working fluid inlet opening A 78  at least partially circumferentially around one piston body C 700  and further across the connecting chiller conduit A 72  to extend at least partially circumferentially, or substantially circumferentially, around another or adjacent piston body C 700 . Similarly, the other or second piston body C 700  includes the chiller working fluid opening and flowpath extended at least partially circumferentially to the connecting chiller conduit A 72  to provide fluid communication and thermal communication to yet another piston body C 700  and circumferentially around the yet another piston body C 700  to the chiller working fluid outlet opening A 80 . 
     In still various embodiments, the chiller working fluid inlet opening A 78 , the chiller working fluid outlet opening A 80 , or both extend at least partially along the lateral direction L or orthogonal to the flowpath of the chiller working fluid passage A 66  such as to ingress and egress the chiller working fluid through the chiller working fluid passage A 66 . 
     In one embodiment, the engine includes the chiller working fluid inlet opening A 78  corresponding to each piston body C 700 . Additionally, or alternatively, the engine includes the chiller working fluid outlet opening A 80  corresponding to each piston body C 700 . It should further be appreciated that in various embodiments, the flowpath of the chiller working fluid passage A 66  extends at least partially along the lateral direction L such as shown and described in regard to  FIG. 1.4 . 3 . As further described in various embodiments herein, the flowpath arrangement shown and described in regard to  FIGS. 1.4 . 3 - 1 . 4 . 7  provides thermal communication of the chiller working fluid with the engine working fluid, such as the engine working fluid within the chiller conduits A 54  at each piston body C 700 . Furthermore, the flowpath arrangements shown and described in regard to  FIGS. 1.4 . 3 - 1 . 4 . 7  further provide a desired amount of heat exchanging surface area for thermal energy transfer from the engine working fluid to the chiller working fluid. As such, embodiments of the chiller conduits A 54 , the chiller working fluid passage A 66 , or both, may provide an improved transfer of thermal energy from the engine working fluid to the chiller working fluid. Further still, embodiments of the chiller conduits A 54 , the chiller working fluid passage A 66 , or both, may desirably increase a temperature differential of the engine working fluid from the cold or compression chamber A 222  relative to the hot or expansion chamber A 221 . Additionally, or alternatively, embodiments of the chiller conduits, A 54 , the chiller working fluid passage A 66 , or both, may desirably a stroke or cycle time or period of the engine A 100 . 
     Referring now to  FIG. 1.4 . 7 , a cutaway perspective view of an exemplary embodiment of the portion of the engine A 100  depicted in  FIG. 1.4 . 4  is provided. The exemplary embodiment in regard to  FIG. 1.4 . 7  may be configured substantially similarly as shown and described in regard to  FIGS. 1.4 . 1 - 1 . 4 . 6 . The cutaway view further depicts the chiller conduit A 54  surrounded by the chiller working fluid passage A 66 . The embodiment in regard to  FIG. 1.4 . 7 , and further depicted at least in part in  FIGS. 1.4 . 5 - 1 . 4 . 6 , a portion of the walled conduit A 1050  is extended through the engine A 100  inward of the plurality of piston bodies C 700  relative to the radial direction R from the longitudinal axis C 204 . In one embodiment, such as depicted in regard to  FIG. 1.4 . 7 , the plurality of walled conduits A 1050  is extended proximal to a reference longitudinal axis C 204 , such as inward of the piston bodies C 700  along a radial direction R relative to the longitudinal axis C 204 . However, in other embodiments, such as depicted in regard to  FIG. 1.7 . 1  through  FIG. 1.7 . 4 , the walled conduits A 1050  may extend outward of the piston bodies C 700 , such as outward along the radial direction R relative to the longitudinal axis C 204 . 
     Referring now to  FIG. 1.4 . 8 , a perspective view of another exemplary embodiment of the engine A 100  is provided. The perspective view in  FIG. 1.4 . 8  further includes a partial cutaway view within the piston body C 700  exposing the chiller working fluid passage A 66  and chiller conduits A 54 . The embodiment provided in regard to  FIG. 1.4 . 8  is configured substantially similarly as shown and described in regard to  FIGS. 3-1.4 . 7 . In  FIG. 1.4 . 8 , the chiller working fluid passage A 66  depicts a single or common chiller working fluid inlet opening A 78  from which the chiller working fluid passage A 66  provides separate flowpaths to each piston body C 700 . The chiller working fluid passage A 66  further depicts a single or common chiller working fluid outlet opening A 80  at which the chiller working fluid passage A 66  re-combines the separated chiller working fluid passages A 66  before egressing the chiller working fluid through the single chiller working fluid outlet opening A 80 . 
     Referring to  FIG. 1.4 . 8 , the chiller working fluid passage A 66  at the chiller working fluid inlet opening A 78  separates into the shorter chiller working fluid flowpath provided to piston bodies C 700  proximate to the chiller working fluid inlet opening A 78 . The chiller working fluid passage A 66  at the chiller working fluid inlet opening A 78  further separates into the longer chiller working fluid flowpath provided to piston bodies C 700  distal to the chiller working fluid inlet opening A 78 . 
     In various embodiments, the piston bodies C 700  distal to the chiller working fluid inlet opening A 78  additionally are proximate to the chiller working fluid outlet opening A 80 . The shorter chiller working fluid flowpath provides the shorter flowpath from the piston body C 700  proximate to the chiller working fluid outlet opening A 80 . The chiller working fluid flowpath A 66  further provides the longer flowpath (relative to the first chiller working fluid flowpath) from the piston body C 700  distal to the chiller working fluid outlet opening A 80 . 
     In one embodiment, the piston body C 700 , such as proximate to the chiller working fluid inlet opening A 78 , receives chiller working fluid via the shorter chiller working fluid flowpath and egresses chiller working fluid via the longer chiller working fluid flowpath. Alternatively, the piston body C 700 , such as proximate to the chiller working fluid outlet opening A 80 , receives chiller working fluid via the longer chiller working fluid flowpath and egresses chiller working fluid via the shorter chiller working fluid flowpath. Altogether, the chiller working fluid passage A 66  may define a substantially equal volume flowpath at each piston body C 700  between the chiller working fluid inlet opening A 78  and the chiller working fluid outlet opening A 80 . The substantially equal volume arrangement may provide a substantially even thermal energy transfer from the engine working fluid at each piston body C 700  to the chiller working fluid. 
     Referring still to  FIG. 1.4 . 8 , in one embodiment, the chiller working fluid passage A 66  at least partially circumferentially surrounds each piston body C 700 . Still further, the chiller working fluid passage A 66  is extended along the lateral direction L or otherwise co-directional to the piston body C 700  such that the chiller working fluid surrounds the piston body C 700 . 
     In various embodiments, such as depicted in regard to  FIG. 1.4 . 8 , the chiller conduit A 54  is extended from the compression chamber A 222  along a first lateral direction and extends along a second lateral direction opposite of the first lateral direction. The chiller conduit A 54  includes an approximately 180 degree turn between the chiller passage opening A 58  and the chiller collection chamber A 62 . The chiller working fluid passage A 66  further surrounds the chiller conduit A 54  along the lateral direction L. In various embodiments, such as depicted in  FIG. 1.4 . 8 , the chiller working fluid passage A 66  further surrounds the 180 degree turn portion of the chiller conduit A 54 . The chiller passage openings A 58  may generally be positioned such as to prevent the piston A 1011  of the piston assembly A 1010  from covering or otherwise obscuring the chiller passage openings A 58  during operation of the system A 10 . 
     During operation, chiller working fluid flowing through the chiller working fluid passage A 66  may receive thermal energy from the engine working fluid within one or more of the chiller conduits A 54 . The rate or quantity of thermal energy transferring from the engine working fluid to the chiller working fluid within the chiller working fluid passage A 66  may vary as between respective portions of the chiller working fluid passage A 66 , such as shown and described in regard to the first chiller working fluid passage A 68  and the second chiller working fluid passage A 70 , and/or between respective piston bodies (e.g., the first piston body and the second piston body). For example, the rate or quantity of thermal energy transferring from the engine working fluid to the chiller working fluid passage A 66  may depend at least in part on a temperature gradient between the chiller conduit A 54  and the chiller working fluid passage A 66 , such as a temperature gradient between the engine working fluid and the chiller working fluid. In some embodiments, however, the engine working fluid within the plurality of chiller conduits A 54  may exhibit a temperature that differs as between at least two piston bodies C 700  (e.g., first piston body and second piston body) and/or as between at least two portions along the lateral extension of the chamber  222  (i.e., temperature gradient of the chamber  222  along the lateral direction L) within a given piston body. Additionally, or in the alternative, the engine working fluid within the plurality of piston bodies C 700  may exhibit a temperature that differs as between at least two piston bodies. For example, the engine working fluid within the plurality of chiller conduits A 54  corresponding to one piston body (e.g., the first piston body) may exhibit a temperature different from the plurality of chiller conduits A 54  corresponding to another piston body (e.g., the second piston body) based at least on the phase difference of the piston assemblies A 1010  within the respective piston bodies during operation of the engine. 
     In some embodiments, the temperature of the chiller working fluid may increase as the chiller working fluid flows through the chiller working fluid passage A 66  and receives thermal energy from the engine working fluid within the chiller conduits A 54 . In one embodiment, as depicted in regard to  FIGS. 1.4 . 3 - 1 . 4 . 7 , the chiller working fluid passage A 66  extending at least partially circumferentially around one piston body (e.g., the first piston body), and further extended at least partially circumferentially around one or more other piston bodies (e.g., the second piston body) includes the chiller working fluid increasing in temperature by receiving thermal energy at one piston body. 
     In some embodiments, engine working fluid flowing from a first piston body flowing to another or second piston body may exhibit a temperature that differs from the engine working fluid flowing in an opposite direction, from the other piston body to the first piston body. 
     In various embodiments, the chiller working fluid and the engine working fluid may exhibit a temperature gradient that depends at least in part on whether the engine working fluid is flowing towards one piston body or another piston body. For example, a first temperature gradient may correspond to the engine working fluid flowing towards one piston body and a second temperature gradient may correspond to the engine working fluid flowing towards another piston body. In some embodiments the first temperature gradient may be smaller than the second temperature gradient. In other embodiments the second temperature gradient may be greater than the first temperature gradient. For example, the first temperature gradient may be smaller than the second temperature gradient at least in part because of the temperature of the engine working fluid flowing towards one piston body is greater than the temperature of engine working fluid flowing towards the other piston body. 
     In some embodiments, the rate and/or quantity of thermal energy transfer from the engine working fluid to the chiller working fluid may depend on whether the engine working fluid defines the first temperature gradient or the second temperature gradient. For example, a first rate and/or quantity of thermal energy transfer from the engine working fluid to the chiller working fluid may correspond to engine working fluid flowing towards one piston body and a second rate and/or quantity of thermal energy transfer from the engine working fluid to the chiller working fluid may correspond to the engine working fluid flowing towards another piston body. In some embodiments the first rate and/or quantity of thermal energy transfer may be smaller than the second rate and/or quantity of thermal energy transfer. In other words, the second rate and/or quantity of thermal energy transfer may be greater than the first rate and/or quantity of thermal energy transfer. For example, the first rate and/or quantity of thermal energy transfer may be smaller than the second rate and/or quantity of thermal energy transfer at least in part because of the first temperature gradient corresponding to engine working fluid flowing towards one piston body being smaller than the second temperature gradient corresponding to engine working fluid flowing towards another piston body. 
     In some embodiments, the efficiency of thermal energy transfer from the engine working fluid to the chiller working fluid may be enhanced at least in part by the second rate and/or quantity of thermal energy transfer corresponding to the engine working fluid flowing towards the first piston body being greater than the first rate and/or quantity of thermal energy transfer corresponding to the engine working fluid flowing towards second piston body. For example, in this way, a relatively larger proportion of the thermal energy input from the chiller conduits A 54  may be applied to the chiller working fluid as the chiller working fluid flows from one piston body to another piston body to which the chiller working fluid passage A 66  is thermally coupled (i.e., via the connecting chiller conduit A 72 ). The thermal energy input to the chiller working fluid during the cycle of the piston assembly in a first direction (e.g., downstroke portion of the stroke cycle) may contribute to the downstroke (e.g., directly) by further cooling and thereby further contracting the engine working fluid. During another portion of the engine cycle (e.g., the upstroke portion of the stroke cycle), a relatively smaller proportion of the thermal input by the engine working fluid in the chiller conduits A 54  may be applied to the chiller working fluid, which may reduce or mitigate a potential for thermal energy output from the engine working fluid to counteract the upstroke by further heating and thereby contracting the engine working fluid, providing an additional or alternative efficiency enhancement. With a relatively smaller proportion of the thermal energy input by the chiller conduits A 54  applied to the chiller working fluid during the upstroke, a smaller portion of the thermal energy input may be transferred to the chiller working fluid. 
     As the chiller working fluid flows through the chiller working fluid passage A 66 , thermal energy may preferentially transfer to the chiller working fluid within the chiller working fluid passage A 66  where the temperature gradient is larger or largest, thereby preferentially providing thermal energy to the chiller working fluid at the walled conduit and/or first or second chiller working fluid passage A 70  where there is a greater capacity to receive thermal energy from the engine working fluid. For example, the first chiller working fluid passage A 68 , positioned more proximate to the expansion chamber A 221  than the second chiller working fluid passage A 70 , may exhibit a larger temperature gradient between the engine working fluid and the chiller working fluid. The second chiller working fluid passage A 70 , positioned distal to the expansion chamber A 221  relative to the first chiller working fluid passage A 68 , may exhibit a lower temperature gradient between the engine working fluid and the chiller working fluid. Additionally, such as described herein, the chiller working fluid passage A 66  at one piston body may exhibit a larger temperature gradient than another piston body to which the chiller working fluid passage A 66  is thermally coupled (i.e., via the connecting chiller conduit A 72 ), such as based on the cycle or stroke of the engine during operation. Still further, the temperature gradient at the first chiller working fluid passage A 68  at one piston body may be different (e.g., greater or lesser) than the second chiller working fluid passage A 70  at another piston body to which the chiller working fluid passage A 66  is thermally coupled, such as due at least in part to the cycle or stroke of the engine. As such, thermal energy may preferentially transfer from the engine working fluid to the chiller working fluid based at least on the larger temperature gradient at any time during the cycle of the engine. 
     It should be appreciated that embodiments of the chiller assembly including the chiller working fluid passage A 66  and the cold side heat exchanger A 42  may function substantially similarly as shown and described by embodiments of the hot side heat exchanger C 108  provided herein. 
     Now referring to  FIG. 1.5 . 1 , an exemplary embodiment of the working-fluid body c 108  is provided. The presently disclosed working-fluid bodies c 108  may define part of the heater body c 100  the piston body C 700 . The working fluid body C 108  includes a plurality of heater conduits or working-fluid pathways C 110  through which engine working fluid flows between the expansion chamber A 221  and the compression chamber A 222 . 
     The plurality of working-fluid pathways c 110  may extend between respective ones of a plurality of a first opening or piston chamber apertures c 111  and respective ones of a plurality of a second opening or regenerator apertures c 113 . The piston chamber apertures c 111  provide fluid communication between the working-fluid pathways c 110  and the piston chamber c 112 , and the regenerator apertures c 113  provide fluid communication between the working-fluid pathways c 110  and the regenerator conduit c 1000 . The piston chamber apertures c 111  may define a first end of the working-fluid pathways c 110  and the regenerator apertures c 113  may define a second end of the working-fluid pathways c 110 . 
     Operation of the engine A 100  and system A 10  includes the plurality of piston assemblies A 1010  moving in cyclic operation, such as in back and forth movement between the piston body c 700  at the first end A 101  and another piston body c 700  at the second end A 102  ( FIG. 1.3 . 1 ). Pressure increases and decreases at respective chambers A 221 , A 222  correspond to movement of the piston assemblies A 1010 , such as further described herein. In exemplary embodiments such as depicted in regard to  FIG. 1.3 . 1 . or  FIG. 1.7 . 1 , the plurality of piston bodies c 700  may include the expansion chamber A 221  and the compression chamber A 222  defined at each end A 101 , A 102  of each piston assembly A 1010 , such as to provide eight each of the expansion chamber A 221  and the compression chamber A 222  at four piston assemblies A 1010 . The plurality of piston assemblies A 1010  may be disposed radially relative to the longitudinal axis C 204 . 
     The plurality of working fluid pathways C 110  extend in fluid communication from a expansion chamber A 221  to the walled conduit A 1050 . In various embodiments, such as further described herein, the working fluid pathways C 110  extend in fluid communication from the expansion chamber A 221  to a corresponding regenerator body C 800  at the walled conduit A 1050 . A first plurality of heater conduits or working-fluid pathways C 110  may fluidly communicate between an expansion chamber A 221  defined by a first piston body C 700  and a first compression chamber A 222  defined by another piston body C 700  different from the first piston body C 700  (e.g., not the first piston body). A second plurality of working-fluid pathways C 110  may fluidly communicate between a second expansion chamber A 221  (i.e., different from the first expansion chamber) defined by a second piston body c 700  and a compression chamber A 222  defined by another piston body C 700  (e.g., not the second piston body). 
     Fluid communication between the expansion chamber A 221  of one piston body C 700  and the compression chamber A 222  of another piston body C 700  through the heater conduits or working fluid pathways C 110  provides for the engine working fluid to be in thermal communication with the heating working fluid surrounding the working fluid pathways C 110 . For example, the heating working fluid, such as described herein, is provided in thermal and/or fluid communication around the working fluid pathways C 110 . The working fluid pathways C 110  fluidly separate the heating working fluid and the engine working fluid while further providing heat transfer between the heating working fluid and the engine working fluid (e.g., heat transfer from the heating working fluid to the engine working fluid). 
     The engine working fluid is heated at least at the working fluid pathways C 110  and provides for pressure change at the respective expansion chamber A 221  (e.g., pressure increase at the expansion chamber A 221 ). Based at least on the engine cycle, such as the movement of the piston assemblies A 1010 , pressure changes at the engine working fluid between the fluidly connected expansion chamber A 221  and the compression chamber A 222  via the heater conduit or working fluid pathways C 110  correspond to heat transfer to the engine working fluid from the heating working fluid. As further described herein, based at least on the engine cycle, heat transfer, or an amount of heat transferred, to the engine working fluid may be based on the engine cycle. For example, the amount of heat transferred to the engine working fluid may correspond to whether the expansion chamber A 221  is increasing in pressure or decreasing in pressure, or whether a corresponding fluidly connected compression chamber A 222  is decreasing in pressure or increasing in pressure. 
     As further described herein, the plurality of heater conduits or working fluid pathways C 110  beneficially provides for heat exchange, such as heat transfer to from the heating working fluid to the engine working fluid. The plurality of working fluid pathways C 110  provides a desired amount of heat transfer to the engine working fluid, such as to improve operation of the engine A 100 . Improved operation of the engine A 100  may include improved power output, improved power density, and/or improved efficiency of the engine A 100 . 
     Now referring to  FIGS. 1.6 . 1  through  1 . 6 . 6 D, exemplary regenerator bodies c 800  will be described. The presently disclosed regenerator bodies c 800  may define part of the heater body c 100  and/or an engine c 002 , such as shown and described in regard to system A 10  and engine A 100  herein. For example, a regenerator body c 800  may define at least a portion of a monolithic body or a monolithic body-segment. Such monolithic body or monolithic body-segment may define at least a portion of the heater body c 100  and/or the engine c 002 . Additionally, or in the alternative, the presently disclosed regenerator bodies c 800  may be provided as a separate component, whether for use in connection with a heater body c 100 , an engine c 002 , or any other setting whether related or unrelated to a heater body c 100  or an engine c 002 . It will be appreciated that an engine c 002  and/or a heater body c 100  may include any desired number of regenerator bodies c 800 . 
       FIG. 1.6 . 1 A through  1 . 6 . 1 D show an exemplary regenerator body c 800  implemented within an exemplary engine c 002 . The regenerator body c 800  may fluidly communicate with one or more piston bodies c 700 . For example, a plurality of working-fluid pathways c 110  may provide fluid communication between a regenerator body c 800  and a piston body c 700 . The working-fluid pathways c 110  may fluidly communicate between a piston chamber c 112  defined by the piston body c 700  and a regenerator conduit c 1000  defined by the regenerator body c 800 . 
     The plurality of working-fluid pathways c 110  may extend between respective ones of a plurality of piston chamber apertures c 111  and respective ones of a plurality of regenerator apertures c 113 . The piston chamber apertures c 111  provide fluid communication between the working-fluid pathways c 110  and the piston chamber c 112 , and the regenerator apertures c 113  provide fluid communication between the working-fluid pathways c 110  and the regenerator conduit c 1000 . The piston chamber apertures c 111  may define a first end of the working-fluid pathways c 110  and the regenerator apertures c 113  may define a second end of the working-fluid pathways c 110 . 
     A piston body c 700  may define a hot-side c 1002  of the piston chamber c 112  and a cold side piston chamber c 1004 . A regenerator conduit c 1000  may include a hot-side portion c 1006  and a cold-side portion c 1008 . A plurality of hot-side working-fluid pathways c 1010  may provide fluid communication between the regenerator body c 800  and a first piston body c 700 , such as between the hot-side portion c 1006  and the hot-side c 1002  of the piston chamber c 112 . A plurality of cold-side working-fluid pathways c 1010  may provide fluid communication between the regenerator body c 800  and a second piston body c 700 , such as between the cold-side regenerator conduit c 1008  the cold-side c 1004  of the piston chamber c 112 . 
     The first piston body c 700  may include a first piston assembly c 090  disposed therein and/or the second piston body c 700  may include a second piston assembly c 090  disposed therein. Heat may be input (Q IN ) to engine-working fluid disposed within the hot-side working-fluid pathways c 1010 , such as from a heater body c 100  or any other suitable heat source. Heat may be extracted (Q OUT ) from engine-working fluid disposed within the cold-side working-fluid pathways c 1012 , such as from a chiller body (not shown) or any other suitable cooling source. A regenerator body c 800  may be disposed adjacent to a piston body c 700 , such as circumferentially adjacent to a piston body c 700 . As shown in  FIG. 1.6 . 1 C, a regenerator body c 800  may circumferentially surround a piston body c 700 . Alternatively, a regenerator body c 800  may be disposed adjacent to a piston body c 700 . In some embodiments, a semi-annular regenerator body c 800  may be disposed circumferentially adjacent to a piston body c 700 . 
     During operation, engine-working fluid flowing from the plurality of hot-side working-fluid pathways c 1010  to the regenerator body c 800  enters the regenerator conduit c 1000 . Fluid passing through the regenerator conduit c 1000  may flow out of the regenerator body c 800  and into the plurality of cold-side working-fluid pathways c 1012 . The regenerator conduit c 1000  includes a heat storage medium c 1014  disposed therein. The heat storage medium c 1014  may be any suitable thermal energy storage medium within which heat from the hot-side working-fluid pathways c 1010  may be intermittently stored as the engine-working fluid flows from the regenerator body c 800  to the cold-side working-fluid pathways c 1012 . In some embodiments, the heat storage medium c 1014  may include a plurality of fin arrays c 1016 ; however, other heat storage medium may additionally or alternatively be utilized, including sensible heat storage and/or latent heat storage technologies. Other suitable heat storage medium may include packed beds, include molten salts, miscibility gap alloys, silicon materials (e.g., solid or molten silicon), phase change materials, and so forth. 
     The plurality of fin arrays c 1016  include an array of high-surface area heat transfer fins having a thermally conductive relationship with engine-working fluid in the regenerator conduit c 1000 . As fluid flows from the hot-side working-fluid pathways c 1010  into or through the regenerator conduit c 1000 , heat transfers to the heat storage medium  1014  (e.g., the plurality of fin arrays c 1016 ), preserving thermal energy from being extracted (Q OUT ) at the chiller body (not shown) or other suitable cooling source. As fluid flows from the cold-side working-fluid pathways c 1012  into or through the regenerator conduit c 1000 , heat transfers from the heat storage medium  1014  (e.g., the plurality of fin arrays c 1016 ) back to the engine-working fluid, thereby returning thermal energy to the engine-working fluid flowing into the hot-side working-fluid pathways c 1010 . 
     Still referring to  FIG. 1.6 . 1 A, in some embodiments, a heat storage medium c 1014  may include a plurality of fin arrays c 1016  adjacently disposed within a regenerator conduit c 1000 . The plurality of fin arrays c 1016  may be respectively supported by the regenerator conduit c 1000  in spaced relation to one another. The spaced relation of the plurality of fin arrays c 1016  may define a gap, G c 1018  longitudinally separating adjacent ones of the plurality of fin arrays c 1016 . 
     Referring again to  FIG. 1.6 . 1 A, in some embodiments, a regenerator body c 800  may include a hot-side portion c 1006  and a cold-side portion c 1008 . The hot-side portion c 1006  may be operably coupled and fluidly communicate with the cold-side portion c 1008 . The hot-side portion c 1006  of the regenerator body c 800  may include a hot-side regenerator conduit c 1038  and a hot-side plurality of fin arrays c 1040  adjacently disposed within the hot-side regenerator conduit c 1038  in spaced relation to one another. The cold-side portion c 1008  of the regenerator body c 800  may include a cold-side regenerator conduit c 1042  and a cold-side plurality of fin arrays c 1044  adjacently disposed within the cold-side regenerator conduit c 1042  in spaced relation to one another. 
     The hot-side portion c 1006  and the cold-side portion c 1008  of the regenerator body c 800  may be separated by a hot-to-cold gap H-C c 1046 . For example, in some embodiments, the spaced relation (e.g., the hot-to-cold gap H-C c 1046 ) of the hot-side plurality of fin arrays c 1040  to the cold-side plurality of fin arrays c 1044  may define a hot-to-cold gap H-C c 1038  longitudinally separating the hot-side plurality of fin arrays c 1040  from the cold-side plurality of fin arrays c 1042 . Additionally, or in the alternative, the hot-side regenerator conduit c 1038  and the cold-side regenerator conduit c 1042  may be in the spaced relation to one another, further defining the hot-to-cold gap H-C c 1046 . The hot-to-cold gap H-C c 1046  may reduce or minimize thermally conductive heat transfer between the hot-side portion c 1006  and the cold-side portion c 1008  of the regenerator body c 800 . In some embodiments, the hot-to-cold gap H-C c 1046  may allow a regenerator body c 800  to provide at least two thermally distinct thermal storage bodies within the same regenerator body c 800 . 
     As described herein, at least a portion of a regenerator body c 800  may define an additively manufactured monolithic body or an additively manufactured monolithic body-segment. The regenerator body c 800  may define a portion of a larger monolithic body or monolithic body segment, or the regenerator body c 800  may define a module insertable into a monolithic body or a monolithic body-segment. In some embodiments, the plurality of fin arrays c 1016  may be monolithically integrated with the regenerator conduit c 100 . For example, the array of interconnected fins c 1056  and fin supports c 1058  may define a monolithic structure such as a portion of a monolithic body or monolithic body-segment. 
     A regenerator body c 800  may be formed of one or more materials selected at least in part on one or more thermal storage properties. For example, one or more materials may be selected for a regenerator body c 800  based at least in part on a thermal conductivity and/or a heat capacity of the material. In some embodiments, the plurality of fin arrays c 1016  may include a first material and the regenerator conduit may include a second material that differs from the first material. For example, the thermal conductivity of the first material may exceed the thermal conductivity of the second material. Additionally, or in the alternative, the heat capacity of the first material may exceed the heat capacity of the second material. In some embodiments, the plurality of fin arrays c 1016  may include a material selected for thermal conductivity and/or the regenerator conduit c 1000  may include a material selected for thermal resistivity. In an exemplary embodiment, the plurality of fin arrays c 1016  may include a metal or metal alloy, and the regenerator conduit c 1000  may include a ceramic. In other embodiments, the regenerator conduit c 1000  may additionally or alternatively include a metal or metal alloy, and/or the plurality of fin arrays c 1016  may include a ceramic. 
     Exemplary metal or metal alloys may be selected for high thermal conductivity and/or heat capacity properties. Suitable metal or metal alloys may include copper, aluminum, tin, zinc, nickel, chromium, titanium, tellurium, magnesium, and/or iron. In some embodiments, the metal or metal alloy may include a rare earth element. Exemplary copper alloys may include CuSn, CuZn, CuZnAs, CuZnP, CuZnFe, CuZnNi, CuCr, and/or CuTeSn. 
     Exemplary ceramics may be selected for low thermal conductivity and/or heat capacity properties. Suitable ceramics may include alumina, beryllia, ceria, and/or zirconia. In some embodiments, the ceramic may include a carbide, a boride, a nitride, and/or a silicide. 
     It should be appreciated that in various embodiments the surface area within the heater conduits or working-fluid pathways C 110  corresponds to an internal wall or surface of the heater conduit C 110  at which the engine working fluid is in direct contact. In one embodiment, the surface area defines a nominal surface area of the working-fluid pathway C 110 , such as a cross sectional area within the working-fluid pathway C 110 . In other embodiments, features may be added or altered to the working-fluid passage C 110  within the heater conduit, such as, but not limited to, surface roughness, protuberances, depressions, spikes, nodules, loops, hooks, bumps, burls, clots, lumps, knobs, projections, protrusions, swells, enlargements, outgrowths, accretions, blisters, juts, and the like, or other raised material, or combinations thereof, to desirably alter flow rate, pressure drop, heat transfer, flow profile or fluid dynamics of the engine working fluid. 
     The cross sectional view provided in  FIG. 1.3 . 1  is cut along the lateral direction L such as to depict two of four piston assemblies A 1010  of the system A 10 . In various embodiments, the system A 10  provided in regard to  FIG. 1.3 . 1  further includes the walled conduits A 1050  disposed inward of the piston bodies C 700  proximate to the reference longitudinal axis C 204 , such as shown and described in regard to  FIGS. 1.4 . 5 - 1 . 4 . 7 . In other embodiments, the system A 10  provided in regard to  FIG. 1.3 . 1  further includes the walled conduits A 1050  disposed outward of the piston bodies C 700 , such as shown and described in regard to  FIG. 1.7 . 1  through  FIG. 1.7 . 4 . 
     Referring to  FIG. 1.7 . 1  through  FIG. 1.7 . 4 , side, end, and perspective views of a portion of the system A 10  are provided. The embodiments provided in regard to  FIG. 1.7 . 1  through  FIG. 1.7 . 4  are configured substantially similarly as shown and described in regard to  FIG. 1.3 . 1 - FIG. 1.3 . 2 . In regard to  FIGS. 1.7 . 1 - FIG. 1.7 . 4 , the portions of the system A 10  depicted therein include four piston assemblies A 1010  positioned within eight respective piston bodies C 700 . The piston bodies C 700  may generally include the first volume wall and the second volume wall shown and described in regard to  FIG. 1.3 . 1 - FIG. 1.3 . 2 . The piston bodies C 700  may generally define cylinders into which pistons A 1011  of the piston assembly A 1010  are each positioned such as to define the expansion chamber A 221  and the compression chamber A 222  within each piston body C 700 . However, it should be appreciated that other suitable geometries of the piston body C 700  containing the piston A 1011  may be utilized. 
     The engine A 100  further includes a plurality of walled conduits A 1050  connecting particular chambers A 221 , A 222  of each piston body C 700  ( FIG. 1.3 . 1 ) such as to define a balanced pressure arrangement of the pistons A 1011 . In various embodiments, the engine A 100  includes at least one interconnected volume of chambers A 221 , A 222  such as described herein. In one embodiment, such as depicted in regard to  FIGS. 1.7 . 1 - FIG. 1.7 . 4 , the engine A 100  includes two interconnected volumes in which each interconnected volume includes an expansion chamber A 221  of a first piston body C 700  of a first piston assembly A 1010  connected in fluid communication of the engine working fluid with a compression chamber A 222  of a second piston body C 700  of a second piston assembly A 1010  each connected by a conduit A 1050 . More particularly, the balanced pressure arrangement of piston assemblies A 1010  depicted in regard to  FIGS. 1.7 . 1 - FIG. 1.7 . 4  includes two interconnected volumes each substantially fluidly separated from one another and/or substantially pneumatically separated from one another. The fluidly separated and/or pneumatically separated arrangement of chambers A 221 , A 222  into the interconnected volume, and those chambers A 221 , A 222  outside of the interconnected volume or in another interconnected volume, is particularly provided via the arrangement of expansion chambers A 221  connected to compression chambers A 222  via the walled conduits A 1050  such as further described herein. 
     In various embodiments, the interconnected volume includes pairs of the expansion chamber A 221  fluidly coupled to the compression chamber A 222  each defined at laterally separated ends of the piston assemblies A 1010 . In one embodiment, the engine A 100  defines a first end  101  separated along the lateral direction L by the connection member A 1030  from a second end  102 , such as depicted in  FIG. 1.7 . 2  and  FIG. 1.7 . 3 . Each end of the engine A 100  defines an expansion chamber A 221  and a compression chamber A 222  at each piston A 1011  of each piston assembly A 1010 . The engine A 100  depicted in  FIGS. 1.7 . 1 - FIG. 1.7 . 4 , and further in regard to  FIG. 1.3 . 1 , includes the expansion chamber A 221  at one end connected to a respective compression chamber A 222  at another end via respective conduits. In one embodiment, such as depicted in  FIGS. 1.7 . 2  and  1 . 7 . 3 , the engine A 100  includes two expansion chambers A 221  at the first end  101  each connected to respective compression chambers A 222  at the second end  102  via respective conduits A 1050 . The engine A 100  further includes two expansion chambers A 221  at the second end  102  each connected to respective compression chamber A 222  at the first end  101  via respective conduits A 1050 . The system A 10  further includes four expansion chambers A 221  at one end each connected to respective compression chambers A 222  at the same end via respective conduits A 1050 . In one embodiment, the system A 10  includes two expansion chambers A 221  at the first end  101  each connected to respective compression chambers A 222  at the first end  101  via respective walled conduits A 1050 . The system A 10  further includes two expansion chambers A 221  at the second end  102  each connected to respective compression chambers A 222  at the second end  102  via respective walled conduits A 1050 . 
     To provide a balanced pressure arrangement of piston assemblies A 1010 , one interconnected volume includes a pair of the expansion chamber A 221  at one end (e.g., the first end  101  or the second end  102 ) connected to the compression chamber A 222  at the other or opposite end. In one embodiment, the expansion chamber A 221  at the first end  101  is fluidly connected to the compression chamber A 222  at the second end  102 . In another embodiment, the expansion chamber A 221  at the second end  102  is fluidly connected to the compression chamber A 222  at the first end  101 . The interconnected volume further includes a pair of expansion chambers A 221  at the first end  101  or the second end  102  connected to a respective compression chamber A 222  at the same end, opposing ends, or both, relative to the expansion chamber A 221 . In one embodiment, the expansion chamber A 221  at the first end  101  is fluidly connected to the compression chamber A 222  at the same end (i.e., the first end  101 ). In another embodiment, the expansion chamber A 221  at the second end  102  is fluid connected to the compression chamber A 222  at the same end (i.e., the second end  102 ). In yet another embodiment, the expansion chamber A 221  at the first end  101  is fluidly connected to the compression chamber A 222  at the second end  102  (i.e., the opposing end). In still yet another embodiment, the expansion chamber A 221  at the second end  102  is fluidly connected to the compression chamber at the first end  101  (i.e., the opposing end). It should be appreciated that the arrangement described herein includes each expansion chamber A 221  of one piston body C 700  of one piston assembly A 1010  connected to a respective compression chamber A 222  of another, different piston body C 700  of another, different piston assembly A 1010 . It should further be appreciated that, in various embodiments, the expansion chamber A 221  of one piston body C 700  and one piston assembly C 1010  is exclusively fluidly connected to the compression chamber A 222  of another piston body C 700  of another piston assembly C 1010  (i.e., each walled conduit A 1050  fluidly connects only one expansion chamber A 221  to only one compression chamber A 222 ). 
     The balanced pressure arrangement of piston assemblies A 1010  described herein is such that a uniform temperature applied at the expansion chambers A 221  and the compression chambers A 222  provides an equal pressure at the expansion chamber A 221  of one piston body C 700  counteracted by an equal and opposite pressure at the same piston body C 700  relative to the expansion chamber A 221 . Stated alternatively, when a uniform temperature is applied to the expansion chambers A 221  and the compression chambers A 222 , movement of one piston assembly A 1010  defining a free piston assembly A 1010  results in pressure cancellation at adjacent piston assemblies A 1010  such that pressure waves will not propagate to induce movement of the adjacent piston assembly A 1010 . 
     It should be appreciated that each interconnected volume described herein includes one or more passages, chambers, openings, or other flowpaths between the arrangements of the compression chamber A 222  and the expansion chamber A 221  described above. For example, the particular arrangements of walled conduits A 1050  providing fluid communication of the engine working fluid between the compression chamber A 222  and the expansion chamber A 221  such as described in regard to  FIGS. 1.7 . 1  through  1 . 7 . 4  further includes the chiller conduits A 54 , collection chambers A 62 , A 64 , heater conduits C 110 , etc. such as shown and described in regard to  FIG. 1.4 . 1  through  FIG. 1.5 . 1 . Additionally, or alternatively, the particular arrangements of walled conduits A 1050  providing fluid communication between the compression chamber A 222  and the expansion chamber A 221  such as described in regard to  FIG. 1.7 . 1  through  FIG. 1.7 . 2  may further include a heat exchanger or regenerator, or features thereof, such as shown and described in regard to  FIG. 1.6 . 1 . 
     Although depicted as a balanced pressure arrangement of four piston assemblies A 1010  at eight piston bodies C 700  defining eight fluidly connected pairs of expansion chambers A 221  and compression chambers A 222 , it should be appreciated that the engine A 100  generally includes an interconnected volume such as described above. As such, other embodiments of the engine A 100  may include a quantity of two or more piston assemblies A 1010  in which the arrangements of the piston assembly A 1010  are scaled accordingly based on the arrangement described above such as to provide at least one interconnected volume of chambers A 221 , A 222  and conduits  1050 . 
     In various embodiments, the system A 10  defines the reference longitudinal axis C 204  extended co-directional to the lateral direction L or generally along a direction along which the pistons A 1011  articulate within the chambers A 221 , A 222 . The chambers A 221 , A 222  are positioned in circumferential arrangement relative to the reference longitudinal axis C 204 . Each chamber  221 ,  222  is extended along the lateral direction L or otherwise co-directional to the reference longitudinal axis C 204 . 
     In one embodiment, the engine includes four piston assemblies A 1010  extended along the lateral direction L and in circumferential arrangement relative to the reference longitudinal axis C 204 . The piston assemblies A 1010  may be positioned equidistant to one another around the reference longitudinal axis C 204 . In one embodiment, a pair of the heater body is positioned at outer ends A 103  of the engine. The heater body is positioned proximate to the expansion chamber A 221  and distal to the compression chamber A 222 . Each heater body may be positioned and configured to provide a substantially even flow of thermal energy to four hot side heat exchangers  160  or expansion chambers A 221  at a time. 
     In other embodiments, the engine A 100  includes two or more piston assemblies A 1010  in side-by-side arrangement. The piston assemblies A 1010  may be positioned equidistant relative to one another. In still various embodiments, a single heater body C 100  may be positioned relative to each hot side heat exchanger or working fluid body C 108 . It should be appreciated that various embodiments of the system A 10  provided herein may include any quantity of heater bodies positioned at any quantity of expansion chambers A 221  as desired. It should be appreciated that other arrangements may be utilized as desired such as to provide thermal energy to the expansion chambers A 221 . In still various embodiments, other arrangements may be utilized such as to provide selective or independent operability of a plurality of heater bodies C 100 . For example, selective or independent operability of the plurality of heater bodies C 100  may desirably control a temperature, flow rate, or other property of thermal energy, or particularly the heating working fluid, provided in thermal communication to the working fluid body C 108 . Selective operability may further include selective on/off operation of one or more heater bodies C 100  independent of one another. 
     It should further be appreciated that although the piston assemblies A 1010  of the engine A 100  are depicted in straight, flat, inline, or horizontally opposed arrangements, the piston assemblies A 1010  and heater bodies C 100  may alternatively be arranged in V-, W-, radial, or circumferential arrangements, or other suitable piston assembly A 1010  arrangements. For example, one or more embodiments of the system A 10  may include a center and/or outer heater body C 100  around which the plurality of piston assemblies A 1010  is positioned. 
     In general, the exemplary embodiments of system A 10  and engine, or portions thereof, described herein may be manufactured or formed using any suitable process. However, in accordance with several aspects of the present subject matter, some or all of system A 10  may be formed using an additive manufacturing process, such as a 3-D printing process. The use of such a process may allow portions of the system A 10  to be formed integrally, as a single monolithic component, or as any suitable number of sub-components. In various embodiments, the manufacturing process may allow the all or part of the heater body, the chiller assembly, the load device c 092 , or the engine to be integrally formed and include a variety of features not possible when using prior manufacturing methods. For example, the additive manufacturing methods described herein provide the manufacture of the system A 10  having unique features, configurations, thicknesses, materials, densities, and structures not possible using prior manufacturing methods. Some of these novel features can, for example, improve thermal energy transfer between two or more components, improve thermal energy transfer to the engine working fluid, improve thermal energy transfer from the engine working fluid to the chiller working fluid, reduce leakages, or facilitate assembly, or generally improve thermal efficiency, power generation and output, or power density of the system A 10  using an additive manufacturing process as described herein. 
     As used herein, the terms “additively manufactured” or “additive manufacturing techniques or processes” refer generally to manufacturing processes wherein successive layers of material(s) are provided on each other to “build-up,” layer-by-layer, a three-dimensional component. The successive layers generally fuse together to form a monolithic component which may have a variety of integral sub-components. 
     Although additive manufacturing technology is described herein as providing fabrication of complex objects by building objects point-by-point, layer-by-layer, typically in a vertical direction, other methods of fabrication are possible and are within the scope of the present subject matter. For example, although the discussion herein refers to the addition of material to form successive layers, one skilled in the art will appreciate that the methods and structures disclosed herein may be practiced with any additive manufacturing technique or manufacturing technology. For example, embodiments of the present disclosure may use layer-additive processes, layer-subtractive processes, or hybrid processes. As another example, embodiments of the present disclosure may include selectively depositing a binder material to chemically bind portions of the layers of powder together to form a green body article. After curing, the green body article may be pre-sintered to form a brown body article having substantially all of the binder removed, and fully sintered to form a consolidated article. 
     Suitable additive manufacturing techniques in accordance with the present disclosure include, for example, Fused Deposition Modeling (FDM), Selective Laser Sintering (SLS), 3D printing such as by inkjets and laserjets, Sterolithography (SLA), Direct Laser Sintering (DLS), Direct Selective Laser Sintering (DSLS), Electron Beam Sintering (EBS), Electron Beam Melting (EBM), Laser Engineered Net Shaping (LENS), Laser Net Shape Manufacturing (LNSM), Direct Metal Deposition (DMD), Digital Light Processing (DLP), Direct Laser Melting (DLM), Direct Selective Laser Melting (DSLM), Selective Laser Melting (SLM), Direct Metal Laser Melting (DMLM), Binder Jetting (BJ), and other known processes. 
     The additive manufacturing processes described herein may be used for forming components using any suitable material. For example, the material may be plastic, metal, concrete, ceramic, polymer, epoxy, photopolymer resin, or any other suitable material that may be in solid, liquid, powder, sheet material, wire, or any other suitable form or combinations thereof. More specifically, according to exemplary embodiments of the present subject matter, the additively manufactured components described herein may be formed in part, in whole, or in some combination of materials including but not limited to pure metals, nickel alloys, chrome alloys, titanium, titanium alloys, magnesium, magnesium alloys, aluminum, aluminum alloys, and nickel or cobalt based superalloys (e.g., those available under the name Inconel® available from Special Metals Corporation). These materials are examples of materials suitable for use in the additive manufacturing processes described herein, and may be generally referred to as “additive materials.” 
     In addition, one skilled in the art will appreciate that a variety of materials and methods for bonding those materials may be used and are contemplated as within the scope of the present disclosure. As used herein, references to “fusing” or “binding” may refer to any suitable process for creating a bonded layer of any of the above materials. For example, if an object is made from polymer, fusing may refer to creating a thermoset bond between polymer materials. If the object is epoxy, the bond may be formed by a crosslinking process. If the material is ceramic, the bond may be formed by a sintering process. If the material is powdered metal, the bond may be formed by a melting or sintering process, or additionally with a binder process. One skilled in the art will appreciate that other methods of fusing materials to make a component by additive manufacturing are possible, and the presently disclosed subject matter may be practiced with those methods. 
     In addition, the additive manufacturing process disclosed herein allows a single component to be formed from multiple materials. Thus, the components described herein may be formed from any suitable mixtures of the above materials. For example, a component may include multiple layers, segments, or parts that are formed using different materials, processes, and/or on different additive manufacturing machines. In this manner, components may be constructed which have different materials and material properties for meeting the demands of any particular application. In addition, although the components described herein are constructed entirely by additive manufacturing processes, it should be appreciated that in alternate embodiments, all or a portion of these components may be formed via casting, machining, and/or any other suitable manufacturing process. Indeed, any suitable combination of materials and manufacturing methods may be used to form these components. 
     An exemplary additive manufacturing process will now be described. Additive manufacturing processes fabricate components using three-dimensional (3D) information, for example a three-dimensional computer model, of the component. Accordingly, a three-dimensional design model of the component may be defined prior to manufacturing. In this regard, a model or prototype of the component may be scanned to determine the three-dimensional information of the component. As another example, a model of the component may be constructed using a suitable computer aided design (CAD) program to define the three-dimensional design model of the component. 
     The design model may include 3D numeric coordinates of the entire configuration of the component including both external and internal surfaces of the component. For example, the design model may define the body, the surface, and/or internal passageways such as openings, support structures, etc. In one exemplary embodiment, the three-dimensional design model is converted into a plurality of slices or segments, e.g., along a central (e.g., vertical) axis of the component or any other suitable axis. Each slice may define a thin cross section of the component for a predetermined height of the slice. The plurality of successive cross-sectional slices together form the 3D component. The component is then “built-up” slice-by-slice, or layer-by-layer, until finished. 
     In this manner, the components described herein may be fabricated using the additive process, or more specifically each layer is successively formed, e.g., by fusing or polymerizing a plastic using laser energy or heat or by sintering or melting metal powder. For example, a particular type of additive manufacturing process may use an energy beam, for example, an electron beam or electromagnetic radiation such as a laser beam, to sinter or melt a powder material. Any suitable laser and laser parameters may be used, including considerations with respect to power, laser beam spot size, and scanning velocity. The build material may be formed by any suitable powder or material selected for enhanced strength, durability, and useful life, particularly at high temperatures. 
     Each successive layer may be, for example, between about 10 μm and 200 μm, although the thickness may be selected based on any number of parameters and may be any suitable size according to alternative embodiments. Therefore, utilizing the additive formation methods described above, the components described herein may have cross sections as thin as one thickness of an associated powder layer, e.g., 10 μm, utilized during the additive formation process. 
     In addition, utilizing an additive process, the surface finish and features of the components may vary as need depending on the application. For example, the surface finish may be adjusted (e.g., made smoother or rougher) by selecting appropriate laser scan parameters (e.g., laser power, scan speed, laser focal spot size, etc.) during the additive process, especially in the periphery of a cross-sectional layer which corresponds to the part surface. For example, a rougher finish may be achieved by increasing laser scan speed or decreasing the size of the melt pool formed, and a smoother finish may be achieved by decreasing laser scan speed or increasing the size of the melt pool formed. The scanning pattern and/or laser power can also be changed to change the surface finish in a selected area. 
     After fabrication of the component is complete, various post-processing procedures may be applied to the component. For example, post processing procedures may include removal of excess powder by, for example, blowing or vacuuming. Other post processing procedures may include a stress relief process. Additionally, thermal, mechanical, and/or chemical post processing procedures can be used to finish the part to achieve a desired strength, surface finish, a decreased porosity decreasing and/or an increased density (e.g., via hot isostatic pressing), and other component properties or features. 
     It should be appreciated that one skilled in the art may add or modify features shown and described herein to facilitate manufacture of the system A 10  provided herein without undue experimentation. For example, build features, such as trusses, grids, build surfaces, or other supporting features, or material or fluid ingress or egress ports, may be added or modified from the present geometries to facilitate manufacture of embodiments of the system A 10  based at least on a desired manufacturing process or a desired particular additive manufacturing process. 
     Notably, in exemplary embodiments, several features of the components described herein were previously not possible due to manufacturing restraints. However, the present inventors have advantageously utilized current advances in additive manufacturing techniques to develop exemplary embodiments of such components generally in accordance with the present disclosure. While certain embodiments of the present disclosure may not be limited to the use of additive manufacturing to form these components generally, additive manufacturing does provide a variety of manufacturing advantages, including ease of manufacturing, reduced cost, greater accuracy, etc. 
     In this regard, utilizing additive manufacturing methods, even multi-part components may be formed as a single piece of continuous metal, and may thus include fewer sub-components and/or joints compared to prior designs. The integral formation of these multi-part components through additive manufacturing may advantageously improve the overall assembly process, reduce potential leakage, reduce thermodynamic losses, improve thermal energy transfer, or provide higher power densities. For example, the integral formation reduces the number of separate parts that must be assembled, thus reducing associated time, overall assembly costs, reduces potential leakage pathways, or reduces potential thermodynamic losses. Additionally, existing issues with, for example, leakage, may advantageously be reduced. Still further, joint quality between separate parts may be addressed or obviated by the processes described herein, such as to desirably reduce leakage, assembly, and improve overall performance. 
     Also, the additive manufacturing methods described above provide much more complex and intricate shapes and contours of the components described herein to be formed with a very high level of precision. For example, such components may include thin additively manufactured layers, cross sectional features, and component contours. As another example, additive manufacturing may provide heat exchanger surface areas, volumes, passages, conduits, or other features that may desirably improve heat exchanger efficiency or performance, or overall engine or system performance. In addition, the additive manufacturing process provides the manufacture of a single component having different materials such that different portions of the component may exhibit different performance characteristics. The successive, additive steps of the manufacturing process provide the construction of these novel features. As a result, the components described herein may exhibit improved functionality and reliability. 
     Closed-cycle engine arrangements, such as Stirling engines, generally define a ratio of power output in Watts to a product of mean average engine working fluid pressure in Pascals, swept volume of the engine working fluid in cubic meters, and engine cycle frequency in Hertz (i.e., operating frequency of a piston assembly), otherwise referred to as a Beale number. A maximum operating Beale number for Stirling engines, depending on operating temperature and engine performance, generally ranges between 0.05 and 0.15. Referring to certain embodiments of the system A 10  shown and described herein, features, arrangements, ratios, or methods of manufacture and assembly shown and described herein provide the engine A 100  to define a first operating parameter in which the first operating parameter defines a maximum operational Beale number greater than or equal to 0.10. In another embodiment, the engine A 100  defines a maximum operational Beale number greater than 0.15. In still another embodiment, the engine A 100  defines a maximum operational Beale number greater than 0.20. In yet another embodiment, the engine A 100  defines a maximum operational Beale number greater than 0.23. In various embodiments, the engine A 100  defines a maximum operational Beale number less than or equal to 0.35. In still various embodiments, the engine A 100  defines a maximum operational Beale number less than 0.30. In one embodiment, embodiments of the engine A 100  shown and described herein define a maximum operational Beale number between 0.10 and 0.35, inclusive. In still various embodiments, the engine A 100  defines a maximum operational Beale number between 0.15 and 0.30. 
     Embodiments of the system A 10  and engine A 100  provided herein provide greater Beale numbers via one or more of the features, arrangements, ratios, or methods of manufacture and assembly provided herein. Greater Beale numbers are provided at least in part via lower average engine working fluid pressure, lower engine cycle frequency of the piston assemblies A 1010 , or lower swept volume of the engine working fluid between fluidly connected chambers A 221 , A 222 , or combinations thereof, relative to the power output from the piston assembly A 1010 . Exemplary embodiments of the system A 10  and engine A 100  provided herein may produce a mechanical power output from the piston assembly A 1010  up to 100 kilowatts (kW) or more. 
     Embodiments of the engine A 100  provided herein may provide greater Beale numbers based at least in part on the plurality of heater conduits C 110  collectively defining a desired heat transferability of thermal energy from the hot side heat exchanger C 108  to the engine working fluid within the plurality of heater conduits C 110 . In various embodiments, the system A 10  defines a ratio of maximum cycle volume of the engine working fluid to a collective volume of the plurality of heater conduits. The maximum cycle volume is the maximum volume of the engine working fluid within the expansion chamber A 221 , the compression chamber A 222 , and the fluid volume connected therebetween (e.g., the expansion chamber A 221  of one piston body and the compression chamber A 222  of another piston body connected by the walled conduit A 1050 ). The minimum cycle volume is the minimum volume of the engine working fluid within the expansion chamber A 221 , the compression chamber A 222 , and the fluid volume connected therebetween (e.g., the expansion chamber A 221  of one piston body and the compression chamber A 222  of another piston body connected by the walled conduit A 1050 ). The difference between the maximum cycle volume and the minimum cycle volume is the swept volume. In one embodiment, the ratio of maximum cycle volume of the engine working fluid to the volume of the passages within the plurality of heater conduits is between 2.5 and 25. For example, in various embodiments, the plurality of heater conduits together contain between two-fifths and one-twenty-fifth of the volume of the total volume of engine working fluid based on the maximum cycle volume. Stated differently, between two-fifths and one-twenty-fifth of the maximum cycle volume of the engine working fluid is receiving thermal energy from the hot side heat exchanger C 108  during operation of the system A 10 . 
     In still various embodiments, embodiments of the engine A 100  provided herein may provide greater Beale numbers based at least in part on a ratio of surface area of the plurality of heater conduits C 110  versus volume of the working fluid within the plurality of heater conduits C 110 . For instance, the plurality of heater conduits may provide a range of surface area collectively within the plurality of heater conduits C 110  relative to the volume of the engine working fluid within the plurality of heater conduits C 110 . The surface area may generally define the internal area of the heater conduits in direct fluid contact with the engine working fluid. In various embodiments, the ratio of surface area of the plurality of heater conduits to volume of the working fluid within the plurality of heater conduits is between 8 and 40. For example, in various embodiments, the plurality of heater conduits together defines a unit surface area within the conduits (i.e., surface area in fluid contact with the engine working fluid) between 8 and 40 times greater than a unit volume of the plurality of heater conduits. 
     In various embodiments, the internal surface area of the plurality of heater conduits is defined between a first opening and a second opening of the heater conduits C 110 . The first opening is in direct fluid communication with the expansion chamber A 221 , such as depicted at the piston chamber aperture C 111  in  FIG. 1.5 . 1 . The second opening is in direct fluid communication with the walled conduit C 1050 , such as depicted at the opening C 113  in  FIG. 1.5 . 1 . In one embodiment, the second opening is in direct fluid communication with the walled conduit C 1050  including the regenerator body C 800  defined therewithin. In another embodiment, the surface area of the plurality of heater conduits C 110  defines an internal area of the heater conduits C 110  corresponding to portions of the heater conduits C 110  receiving thermal energy from the heater body C 100 . In another embodiment, the surface area of the plurality of heater conduits C 110  defines an internal area of the heater conduits C 110  extending from a first opening, such as defined at the plurality of piston apertures C 111  in  FIG. 1.5 . 1 , to a first or proximal fin, tab, wall, or other feature of the fin array C 1016  of the regenerator body C 800  at the walled conduit C 1050 . In still another embodiment, such as an embodiment providing direct fluid communication of the heater conduits C 110  to the chiller conduits A 54 , the second opening, such as depicted at opening C 113  in  FIG. 1.5 . 1 ., is in direct fluid communication with chiller collection chamber A 62  or the chiller conduits A 54 . In various embodiments, the second opening, such as depicted at opening C 113  in  FIG. 1.5 . 1 ., is in direct fluid communication with the chiller collection chamber opening A 60 . 
     Embodiments of the engine A 100  provided herein may provide greater Beale numbers based at least in part on the plurality of chiller conduits A 54  collectively defining a desired heat transferability of thermal energy from the engine working fluid within the plurality of chiller conduits A 54  to the cold side heat exchanger A 42 . In various embodiments, the system A 10  defines a ratio of maximum cycle volume of the engine working fluid to a collective volume of the plurality of chiller conduits A 54 . In one embodiment, the ratio of maximum cycle volume of the engine working fluid to the volume of the plurality of chiller conduits A 54  is between 10 and 100. For example, in various embodiments, the plurality of chiller conduits A 54  together contain between one-tenth and one-hundredth of the volume of the total volume of engine working fluid based on the maximum cycle volume. Stated differently, between one-tenth and one-hundredth of the maximum cycle volume of the engine working fluid is transferring thermal energy to the cold side heat exchanger A 42  during operation of the system A 10 . 
     In still various embodiments, embodiments of the engine provided herein may provide greater Beale numbers based at least in part on a ratio of surface area of the plurality of chiller conduits A 54  versus volume of the working fluid within the plurality of chiller conduits A 54 . For instance, the plurality of chiller conduits A 54  may particularly provide a range of surface area collectively within the plurality of chiller conduits A 54  relative to the volume of the engine working fluid within the plurality of chiller conduits A 54 . In various embodiments, the ratio of surface area of the plurality of chiller conduits A 54  to volume of the working fluid within the plurality of chiller conduits A 54  is between 7 and 40. For example, in various embodiments, the plurality of chiller conduits A 54  together defines a unit surface area within the conduits (i.e., surface area in fluid contact with the engine working fluid) between 7 and 40 times greater than a unit volume of the plurality of chiller conduits A 54 . 
     In various embodiments, the surface area of the chiller conduits A 54  is defined from the chiller passage opening A 58  to the chiller collection chamber opening A 60 . In one embodiment, the surface area of the chiller conduits A 54  is the internal area within the chiller conduits A 54  corresponding to the portion of the chiller conduits A 54  at least partially surrounded by the chiller working fluid within the chiller working fluid passage A 66  in thermal communication with the engine working fluid. 
     Various embodiments of the system A 10  and engine A 100  shown and described herein provide desired power outputs, power densities, or efficiencies, or combinations thereof, based on one or more elements, arrangements, flowpaths, conduits, surface areas, volumes, or assemblies, or methods thereof, provided herein. Efficiencies described herein may include T Hot,engine  corresponding to temperature input to the engine working fluid at the heater conduits or working fluid pathways C 110  from the hot side heat exchanger C 108 . Still various embodiments include T Cold,ambient  corresponding to temperature removed from the engine working fluid at the chiller conduits A 54  to the cold side heat exchanger A 42 . In other instances, the temperature input may alternatively correspond to heat or thermal energy input to the engine working fluid, such as from the heating working fluid. Still further, the temperature removed may alternatively correspond to heat or thermal energy output from the engine working fluid, such as to the chiller working fluid. In still various embodiments, the environment is the chiller working fluid into which the engine A 100  rejects, exhausts, or otherwise releases heat or thermal energy from the engine working fluid at the chiller conduits A 54 . 
     In still yet various embodiments, efficiencies described herein may include Q Out  corresponding to thermal energy received by the engine working fluid at the heater conduits or working fluid pathways C 110  from the hot side heat exchanger C 108 . Still various embodiments include Q In  corresponding to thermal energy received at the chiller working fluid at the chiller working fluid passage A 56  at the cold side heat exchanger A 42  from the engine working fluid at the chiller conduits A 54 . 
     In still another embodiment, E out  is the net electrical energy output from the load device C 092  that is operatively coupled to the engine A 100  via the piston assembly C 1010 . 
     In various embodiments, the features, arrangements, surface areas, volumes, or ratios thereof provide the engine A 100  to operate at higher efficiencies over known closed cycle engines, or Stirling engines particularly. Various embodiments of the system A 10  provided herein may be configured to produce mechanical power output from the piston assembly A 1010  at a Carnot efficiency η Carnot  of up to approximately 80%. In some embodiments, the system A 10  provided herein may be configured to produce mechanical power output from the piston assembly A 1010  at an efficiency of up to approximately 80% cold environments, such as in space. In one embodiment, the Carnot efficiency corresponds to the thermal efficiency of the engine A 100  receiving thermal energy or heat at the heater conduits C 110  and expelling thermal energy or heat from the engine working fluid at the chiller conduits A 54 . In one embodiment, the Carnot efficiency corresponds at least to the engine A 100  including the hot side heat exchanger C 108  and the cold side heat exchanger A 42 , such as depicted at the engine level efficiency ( FIG. 1.2 . 1 ). 
     Various embodiments of the system A 10  provided herein may be configured to produce mechanical power output from the piston assembly A 1010  at electrical efficiency of up to approximately 80%. In one embodiment, the electrical efficiency corresponds to the useful work generated by the engine A 100  receiving heat or thermal energy from the heating working fluid and releasing heat or thermal energy to the chiller working fluid and converted into electrical energy via the load device C 092 , such as depicted within area A 106  in  FIG. 1.2 . 1 . In one embodiment, the electrical efficiency corresponds at least to the system A 10  including the engine A 100 , the heater body C 100 , and the chiller assembly A 40 , such as depicted at the system level efficiency ( FIG. 1.2 . 1 ). 
     In one embodiment, the system A 10  provides a temperature differential via the heater body C 100  and the chiller assembly C 40  in which the engine A 100  generates mechanical power output between 1 kW and 100 kW relative to the piston assembly A 1010 . In another embodiment, the system A 10  is configured to generate between 10 kW and 100 kW. In yet another embodiment, the system A 10  is configured to generate between 25 kW and 100 kW. In yet another embodiment, the system A 10  may be configured to produce greater than 100 kW. For example, the system A 10  may include a plurality of the engine A 100  operably coupled at two or more piston assemblies A 1010  and the load device c 092  to produce greater than 100 kW. In various embodiments, a plurality of the engine A 100  may be operably coupled to produce up to 5 megawatts. 
     In still various embodiments, the engine A 100  further defines a second operating parameter defining a ratio of mechanical power output from the piston assembly A 1010  to maximum cycle volume of the working fluid between 0.0005 and 0.0040 kW per cubic centimeter (cc) for a given efficiency. In various embodiments, the ratio of mechanical power output from the piston assembly A 1010  to maximum cycle volume of the working fluid is a range of maximum ratio at which the mechanical power output from the piston assembly A 1010  to maximum cycle volume of the working fluid is defined. In some embodiments, the engine A 100  defines a maximum ratio of mechanical power output from the piston assembly A 1010  to maximum cycle volume of the working fluid between 0.0005 and 0.0040 kW generated from the piston assembly A 1010  for one cubic centimeter of engine working fluid at an engine efficiency of at least 50%. Stated differently, between 0.0005 and 0.0040 kW is generated from the piston assembly A 1010  for one cubic centimeter of engine working fluid at an engine efficiency of at least 50%. In various embodiments, the engine A 100  defines a ratio of mechanical power output from the piston assembly A 1010  to the maximum cycle volume of the working fluid between 0.0010 and 0.0030 kW/cc at an engine efficiency of at least 50%. In another embodiment, the engine A 100  defines a ratio of mechanical power output from the piston assembly A 1010  to the maximum cycle volume of the working fluid between 0.0015 and 0.0025 kW/cc at an engine efficiency of at least 50%. In one embodiment, the system A 10  defines the ratio of mechanical power output from the piston assembly A 1010  to maximum cycle volume of the working fluid between 0.0005 kW/cc and 0.0040 kW/cc at a Carnot efficiency of the engine of up to 80%. In another embodiment, the engine A 100  defines the ratio of mechanical power output from the piston assembly A 1010  to maximum cycle volume of the working fluid between 0.0005 kW/cc and 0.0040 kW/cc with an efficiency of the engine A 100  of up to 60%. 
     Various embodiments of the system A 10  shown and described herein provide a power density by efficiency that may be advantageous over certain power generation or energy conversion systems including engine and heat exchanger systems. In certain embodiments, the system A 10  includes a third operating parameter defining a multiplication product of power density (kW/m 3 ) and system level efficiency greater than 51. For example, the power density is power output at the load device c 092  over volume of the engine working fluid at the engine A 100 . In particular embodiments, the system A 10  includes the power density over maximum cycle volume of the engine working fluid at the engine A 100 . In some embodiments, the system A 10  includes a power density (kW/m 3 ) by efficiency greater than 100 kilowatts over cubic meters (kW/m 3 ). In still other embodiments, the system A 10  includes a power density by efficiency greater than 255 kW/m 3 . In various embodiments, the system A 10  includes a power density by efficiency less than 400 kW/m 3 . In other embodiments, the system A 10  includes a power density by efficiency less than 125 (kW/m 3 ). In still various embodiments, the system A 10  includes a power density (kW/m 3 ) by efficiency between 51 and 400 kW/m 3 . 
     In still various embodiments, the engine A 100  includes a fourth operating parameter at which one or more of the efficiencies and ratio of mechanical power output from the piston assembly A 1010  to maximum cycle volume of the engine working fluid relative to a temperature differential of the engine working fluid at the expansion chamber A 221  and the compression chamber A 222 . In one embodiment, the fourth operating parameter defines the temperature differential of the engine working fluid at the expansion chamber A 221  an the compression chamber A 222  of at least 630 degrees Celsius. In one embodiment, the cold side heat exchanger A 42  is configured to reduce the temperature of the engine working fluid at the chiller conduits A 54  and/or compression chamber A 222  less than 120 degrees Celsius. In another embodiment, the cold side heat exchanger A 42  is configured to reduce the temperature of the engine working fluid at the chiller conduits A 54  or compression chamber A 222  to between approximately −20 degrees Celsius and approximately 120 degrees Celsius on average during steady-state full power operation. In still another embodiment, the cold side heat exchanger A 42  is configured to reduce the temperature of the engine working fluid at the chiller conduits A 54  or compression chamber A 222  to between 20 degrees Celsius and approximately 120 degrees Celsius on average during steady-state full power operation. In yet another embodiment, the hot side heat exchanger C 108  is configured to heat the engine working fluid at the heater conduits C 110  or expansion chamber A 221  to at least 750 degrees Celsius. However, it should be appreciated that an upper limit of the heat provided to the hot side heat exchanger C 108  or the expansion chamber A 221  is based at least on materials limits, such as one or materials listed or described herein, or another suitable material for constructing the engine and/or system. Material limits may include, but are not limited to, a melting point, tensile stress, yield stress, deformation or deflection limits, or desired life or durability of the engine. 
     It should be appreciated that performances, power outputs, efficiencies, or temperature differentials at the system A 10 , the engine A 100 , or both, provided herein may be based on a “Sea Level Static” or “Standard Day” input air condition such as defined by the United States National Aeronautics and Space Administration, unless otherwise specified. For example, unless otherwise specified, conditions provided to the heater body, the chiller assembly, or both, or any subsystems, components, etc. therein, or any other portions of the system A 10  receiving an input fluid, such as air, are based on Standard Day conditions. 
     The heat transfer relationships described herein may include thermal communication by conduction and/or convection. A heat transfer relationship may include a thermally conductive relationship that provides heat transfer through conduction (e.g., heat diffusion) between solid bodies and/or between a solid body and a fluid. Additionally, or in the alternative, a heat transfer relationship may include a thermally convective relationship that provides heat transfer through convection (e.g., heat transfer by bulk fluid flow) between a fluid and a solid body. It will be appreciated that convection generally includes a combination of a conduction (e.g., heat diffusion) and advection (e.g., heat transfer by bulk fluid flow). As used herein, reference to a thermally conductive relationship may include conduction and/or convection; whereas reference to a thermally convective relationship includes at least some convection. 
     A thermally conductive relationship may include thermal communication by conduction between a first solid body and a second solid body, between a first fluid and a first solid body, between the first solid body and a second fluid, and/or between the second solid body and a second fluid. For example, such conduction may provide heat transfer from a first fluid to a first solid body and/or from the first solid body to a second fluid. Additionally, or in the alternative, such conduction may provide heat transfer from a first fluid to a first solid body and/or through a first solid body (e.g., from one surface to another) and/or from the first solid body to a second solid body and/or through a second solid body (e.g., from one surface to another) and/or from the second solid body to a second fluid. 
     A thermally convective relationship may include thermal communication by convection (e.g., heat transfer by bulk fluid flow) between a first fluid and a first solid body, between the first solid body and a second fluid, and/or between a second solid body and a second fluid. For example, such convection may provide heat transfer from a first fluid to a first solid body and/or from the first solid body to a second fluid. Additionally, or in the alternative, such convection may provide heat transfer from a second solid body to a second fluid. 
     It will be appreciated that the terms “clockwise” and “counter-clockwise” are terms of convenience and are not to be limiting. Generally, the terms “clock-wise” and “counter-clockwise” have their ordinary meaning, and unless otherwise indicated refer to a direction with reference to a top-down or upright view. Clockwise and counter-clockwise elements may be interchanged without departing from the scope of the present disclosure. 
     Where temperatures, pressures, loads, phases, etc. are said to be substantially similar or uniform, it should be appreciated that it is understood that variations, leakages, or other minor differences in inputs or outputs may exist such that the differences may be considered negligible by one skilled in the art. Additionally, or alternatively, where temperatures or pressures are said to be uniform, i.e., a substantially uniform unit (e.g., a substantially uniform temperature at the plurality of chambers A 221 ), it should be appreciated that in one embodiment, the substantially uniform unit is relative to an average operating condition, such as a phase of operation of the engine, or thermal energy flow from one fluid to another fluid, or from one surface to a fluid, or from one surface to another surface, or from one fluid to another surface, etc. For example, where a substantially uniform temperature is provided or removed to/from the plurality of chambers A 221 , A 222 , the temperature is relative to an average temperature over a phase of operation of the engine. As another example, where a substantially uniform thermal energy unit is provided or removed to/from the plurality of chambers A 221 , A 222 , the uniform thermal energy unit is relative to an average thermal energy supply from one fluid to another fluid relative to the structure, or plurality of structures, through which thermal energy transferred. 
     Various interfaces, such as mating surfaces, interfaces, points, flanges, etc. at which one or more monolithic bodies, or portions thereof, attach, couple, connect, or otherwise mate, may define or include seal interfaces, such as, but not limited to, labyrinth seals, grooves into which a seal is placed, crush seals, gaskets, vulcanizing silicone, etc., or other appropriate seal or sealing substance. Additionally, or alternatively, one or more of such interfaces may be coupled together via mechanical fasteners, such as, but not limited to, nuts, bolts, screws, tie rods, clamps, etc. In still additional or alternative embodiments, one or more of such interfaces may be coupled together via a joining or bonding processes, such as, but not limited to, welding, soldering, brazing, etc., or other appropriate joining process. 
     It should be appreciated that ratios, ranges, minimums, maximums, or limits generally, or combinations thereof, may provide structure with benefits not previously known in the art. As such, values below certain minimums described herein, or values above certain maximums described herein, may alter the function and/or structure of one or more components, features, or elements described herein. For example, ratios of volumes, surface area to volume, power output to volume, etc. below the ranges described herein may be insufficient for desired thermal energy transfer, such as to undesirably limit power output, efficiency, or Beale number. As another example, limits greater than those described herein may undesirably increase the size, dimensions, weight, or overall packaging of the system or engine, such as to undesirably limit the applications, apparatuses, vehicles, usability, utility, etc. in which the system or engine may be applied or operated. Still further, or alternatively, undesired increases in overall packaging may undesirably decrease efficiency of an overall system, application, apparatus, vehicle, etc. into which the engine may be installed, utilized, or otherwise operated. For example, although an engine may be constructed defining a similar or greater efficiency as described herein, such an engine may be of undesirable size, dimension, weight, or overall packaging such as to reduce an efficiency of the system into which the engine is installed. As such, obviation or transgression of one or more limits described herein, such as one or limits relative to features such as, but not limited to, heater conduits, chiller conduits A 54 , chamber volumes, walled conduit volumes, or operational temperatures, or combinations thereof, may undesirably alter such structures such as to change the function of the system or engine. 
     Although specific features of various embodiments may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the present disclosure, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing. 
     This written description uses examples to describe the presently disclosed subject matter, including the best mode, and also to provide any person skilled in the art to practice the subject matter, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the presently disclosed subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.