Abstract:
A method of separating a liquid portion (F 1 ) of a working fluid from a vaporous flow of the working fluid (F 3 ). The method includes the steps of allowing a vapor portion of the working fluid (F 3 ) to flow through the system enabling a liquid portion (F 1 ) of the working fluid to separate using a combination of cooling means ( 234; 236 ) and a fluid separator ( 212 ). The cooling is accomplished by methods of spraying the saturated working fluid (F 3 ) with chilled fluid (F 1cooled ) having the capacity to remove heat form the working fluid by direct contact. The fluid separator ( 212 ) arranged with the cooling methods enhances the condensate rate of the overall working fluid flow, whereby at least a portion of the working fluid is separated out of the cooled vaporous working fluid in liquid form (F 1 ). Arrangements of systems for facilitating separation are also provided.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Statement of the Technical Field 
         [0002]    The invention concerns a condenser assembly, and more particularly systems and methods which include direct contact mixing and separation of working fluids and the creation of desired fluid states. 
         [0003]    2. Description of the Related Art 
         [0004]    Heat engines and the like use energy provided in the form of heat to perform mechanical work. In most systems, a condenser is included to condense the working fluid after it has been vaporized and expanded. By condensing the working fluid, it changes at least a portion of the working fluid back into a liquid which may be returned to a boiler or the like of the system. This allows clean and treated condensate to be reused and it is generally easier to pump liquid than vapor. It is desirable to increase the efficiency of the cycle by optimally balancing the temperature, pressure and mass flow rate between the boiler and the condenser. 
       SUMMARY OF THE INVENTION 
       [0005]    The unique embodiment of the general concept relies on the ability to not fully condense 100 percent of the working fluid subsequent to performing work. Traditional Rankine cycles require 100 percent condensing. The invention incorporates methods enabling a useful portion of the working fluid, remaining in a vapor state, to pass thru the condensing means, being useful to aid in the separation process more efficiently than the prior art of full condensation as defined by current cycle architectures. 
         [0006]    Embodiments of the invention concern a method of separating a liquid portion of a working fluid from a vaporous flow of the working fluid. The method includes the steps of directing a liquid portion of the working fluid which has previously been separated through a chiller such that said portion of the first working fluid is cooled to define a cooling fluid; spraying the cooling fluid into the vaporous flow of the working fluid with a resultant cooled vaporous working fluid; and passing the cooled vaporous working fluid through a separator whereby at least a portion of the working fluid is separated out of the cooled vaporous working fluid in liquid form. 
         [0007]    The invention also includes a system for separating a liquid portion of a working fluid from a vaporous flow of the working fluid. The system includes a separator having a body and defining a reservoir for a liquid portion of the working fluid to collect. A chiller is configured to cool a previously separated liquid portion of the working fluid drawn from the reservoir to define a cooling fluid. A sprayer is positioned relative to the separator and configured to spray the cooling fluid into a flow of the vaporous working fluid before the vaporous working fluid reaches the separator. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Embodiments will be described with reference to the following drawing figures, in which like numerals represent like items throughout the figures, and in which: 
           [0009]      FIG. 1  is a schematic drawing that is useful for understanding a heat engine incorporating an exemplary condenser assembly in accordance with an embodiment of the invention. 
           [0010]      FIG. 2  is a schematic diagram of a condenser assembly in accordance with an exemplary embodiment of the invention. 
           [0011]      FIG. 3  is a side elevation of an exemplary centrifugal liquid-vapor separator of the condenser assembly of  FIG. 2 . 
           [0012]      FIG. 4  is a cross-sectional view along the line  4 - 4  in  FIG. 3 . 
           [0013]      FIG. 5  is a schematic diagram of an alternative condenser assembly in accordance with an exemplary embodiment of the invention. 
           [0014]      FIG. 6  is a schematic diagram of another alternative condenser assembly in accordance with an exemplary embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    The invention is described with reference to the attached figures. The figures are not drawn to scale and they are provided merely to illustrate the instant invention. Several aspects of the invention are described below with reference to example applications for illustration. It should be understood that numerous specific details, relationships, and methods are set forth to provide a full understanding of the invention. One having ordinary skill in the relevant art, however, will readily recognize that the invention can be practiced without one or more of the specific details or with other methods. In other instances, well-known structures or operation are not shown in detail to avoid obscuring the invention. The invention is not limited by the illustrated ordering of acts or events, as some acts may occur in different orders and/or concurrently with other acts or events. Furthermore, not all illustrated acts or events are required to implement a methodology in accordance with the invention. 
         [0016]    The invention concerns a condenser assembly  210  for use in a Hybrid Thermal Cycle (HTC), or other energy transfer operations utilizing fluids F 1 , F 2 , and F 3  where F 3  is comprised of a mixture of fluids F 1  and F 2 . The F 1  fluid is a fluid construct that is advantageously selected so that it is capable of transitioning from a liquid to a vapor in some parts of the cycle, and from a vapor to a liquid during other portions of the cycle. Fluid F 2  is preferably selected so that it remains vaporous throughout the cycle. The F 1  fluid is mixed with the F 2  fluid in parts of the cycle to form the F 3  fluid. Later in the cycle the F 1  fluid is separated from the F 3  fluid. Following a compression portion of the cycle during which F 2  is compressed, there is an expansion part of the cycle during which F 3 , comprised of a mixture of F 1  and F 2 , is expanded. During this expansion, the F 1  fluid functions to support or maintain the temperature of the F 2  fluid, preventing it from cooling more rapidly than without the latent heat that is available from the F 1  fluid. If the F 2  fluid were expanded without the portion of the F 1  fluid it would cool more rapidly, having less capacity to perform work. This characteristic or effect in the cycle is desirable as it enables the fluid mixture F 3  to perform work for a longer period of time during expansion. This ability of F 1  to effectively delay the cooling of F 2  essentially ends when the F 1  fluid reaches a point where it transitions from a vapor back into a liquid. At the end of the expansion process, at least a portion of the F 1  fluid condenses out of the F 3 , leaving a residual portion, which is F 2 . 
         [0017]    An exemplary heat engine  200  incorporating the condenser assembly  210  is illustrated in  FIG. 1 . It should be appreciated that the heat engine shown is similar to that of a Rankine cycle machine that has been modified to allow a portion of the non-condensed working fluid to be returned to the cycle for reuse. This example is merely provided as a way of incorporating the condenser assembly  210  and is not intended to limit the invention. Many variations of heat engines incorporating the inventive assembly are possible. Accordingly, heat engines incorporating the inventive assembly can include more or fewer components or steps and still remain within the scope of the invention. 
         [0018]    The heat engine  200  makes use of a high temperature thermal source  225  and optionally a low temperature thermal source  227 . The “high temperature” nomenclature which is used to describe thermal source  225  is intended to emphasize that such thermal source is at a higher temperature as compared to the temperature of low temperature thermal source  227 . Although thermal source  225  will have a higher temperature compared to low temperature thermal source  227 , it should be appreciated that high temperature thermal source  225  can actually have a relatively low temperature as compared to those temperatures which are normally used to provide efficient operation of a conventional heat engine. For example, in some embodiments, the high temperature thermal source  225  may actually only have a temperature of about 800° F. or less. In other embodiments, the high temperature thermal source  225  can have a temperature of about 400° F. or less. The ability to efficiently utilize such sources of heat is a significant advantage of the present invention. 
         [0019]    Suitable choices for working fluids F 1  and F 2  will be described below in further detail. Still, given the anticipated temperatures for thermal source  225 ,  227 , it can be advantageous to select the working fluid F 1  to be a low vapor state formulation to facilitate vaporization of such working fluid at relatively low temperatures. Examples of such low vapor state formulations can include fluids such as methanol or pentane. 
         [0020]    A high pressure boiler  203  can use as its primary heat source a supply of steam from the high temperature thermal source  225 . For example, the high temperature thermal source can be a geothermal well or waste heat from some high temperature process or other power generation system. The low temperature thermal source can be a thermal source that is entirely independent of the high temperature thermal source  225 . However, it can be advantageous to select the optional low temperature thermal source  227  to be a down-line flow from the high temperature thermal source  225 , after such flow has provided a portion of its thermal energy to the high pressure boiler  203 , as illustrated in  FIG. 1 . However, it is appreciated that a separate low temperature thermal source may be utilized. 
         [0021]    The exemplary heat engine  200  also includes a low pressure boiler  207 . The high pressure boiler  203  will generally have a higher internal operating pressure as compared to the optional low pressure boiler  207 . However, it should be appreciated that high pressure boiler  203  can actually have a relatively low pressure as compared to those operating pressures which are normally used to provide efficient operation of a conventional heat engine. For example, in conventional heat engines, high pressure boilers typically are understood as boilers that operate in the range of 1000 to 3000 psi. In contrast, the high pressure boiler  203  can operate at a pressure in the range of 300 psi or less. Still, the invention is not limited in this regard and the actual operating pressure in the high pressure boiler  203  and optional low pressure boiler  207  can vary in accordance with the available heat source and other design conditions. 
         [0022]    Referring again to  FIG. 1 , a first working fluid F 1  (in liquid form) is pressurized using a pump  201   a  and a first flow F 1 (1) of the working fluid F 1  fluid is communicated to the interior of the low pressure boiler  207 . The low pressure boiler  207  can have a relatively low internal pressure as compared to the high pressure boiler  203 . In a preferred embodiment of the invention, the pressure within the low pressure boiler  207  is maintained such that it is approximately equal to a vaporization pressure of F 1  at a temperature corresponding to the low temperature thermal source  227 . The temperature in the low pressure boiler  207  is determined by the low temperature thermal source  227 . The relatively low pressure and relatively low temperature within the low pressure boiler  207  facilitates vapor formation (sometimes referred to herein as F 1 (1) vapor). The F1(1) vapor from the low pressure boiler  207  is communicated to a mixing chamber  206  (sometimes referred to herein as a mixer), which will be discussed below in further detail. The F1(1) vapor will contain a certain amount of thermal potential energy (heat energy) when it enters into the mixing chamber  206 . 
         [0023]    A second flow F 1 (2) of a first liquid working fluid F 1  is pressurized using a pump  201   b . It is understood that the pumps  201   a  and  201   b  may combined in a single pump. The pressurized fluid is communicated to the high pressure boiler  203  which is maintained at a relatively high temperature as determined by high temperature thermal source  225 . The high pressure boiler  203  will add a predetermined amount of thermal energy to the F 1 (2) working fluid. As a result of these operations, the F 1 (2) working fluid is converted to a vapor (sometimes referred to herein as F 1 (2) vapor). 
         [0024]    The F1(2) vapor formed in high pressure boiler  203  is communicated to an expander  209  where the thermal energy contained in the F1(2) vapor is used to perform work. Still, a designer may choose to omit the expander  209  in some embodiments. The F1(2) vapor, after exiting the expander  209 , still contains high quantities of thermal energy, and is therefore communicated to the mixing chamber  206 . 
         [0025]    The F1(1) and F1(2) flow of F1working fluid vapor are communicated to the mixing chamber  206 . Within the mixing chamber  206 , F1(2) vapor and the F1(1) vapor are mixed with a vaporous flow of working fluid F2 which has been compressed in compressor  204 . In the example provided, the compressor  204  is powered by the expander  209 . These three separate vaporous fluid flows comprised of F1(1), F1(2) and F2 are combined or mixed to form a vaporous mixture which is referred to herein as third working fluid F3 (or F3 vapor). Due to this mixing of the working fluids, the transfer of thermal energy between the fluids is facilitated. In some embodiments, additional thermal energy can optionally be provided from an independent source to the F3 vapor contained in the mixing chamber  206 . For example, the additional thermal energy can be provided to the mixer from a source that is external to the system shown in  FIG. 1 . It should be understood that the construct of the mixing chamber may comprise a broad array of physical embodiments. These features may include lower and higher pressure zones, artifacts to induce or reduce turbulence, one or more venturis to increase or decrease specific flow velocities and expansion or restrictions that are intended to enhance, tune and optimize the condition of the overall fluid mixture F3 entering the expander  208 . 
         [0026]    It is not necessary for all thermal energy transfer between the F 1 (1), F 1 (2) and F 2  vapor to occur within the mixing chamber  206 . In some embodiments of the invention, a portion of such transfer can occur after the F 3  vapor exits the mixing chamber. For example, in an embodiment of the invention, at least a portion of such transfer can continue occurring as the F 3  vapor continues through an expansion cycle discussed below. Also, it is possible for the F 1 (1), F 1 (2) vapor, and the F 2  vapor fluids to enter the mixer at approximately the same temperatures and pressures. However, as a result of the different chemical compositions of such fluids, transfer or exchange of thermal energy as between them, can still potentially take place in a subsequent expansion cycle. Details of the expansion cycle are discussed below with regard to expander  208 . 
         [0027]    The vaporous third working fluid F 3  is communicated under pressure from the mixing chamber  206  to expander  208  for performing useful work. Well known conventional expander technology can be used for purposes of implementing expander  208 , provided that it is capable of using a pressurized vapor to perform useful work. For example, the expander  208  can be an axial flow turbine, custom turbo-expander, vane expander or reciprocating expander. Advantageously the expander  208  will be selected by those skilled in the art to provide high conversion efficiency based on the specific thermodynamic and fluid properties of F 3  delivered to the expander for a particular embodiment of the cycle. Still, the invention is not limited in this regard. 
         [0028]    After such work is performed by the expander  208 , the F 3  working fluid is communicated from the expander to a condenser assembly  210  including a condenser  212 . The condenser assembly  210  includes at least three ports. Port  221  is used to receive the F 3  working fluid provided to the condenser. Port  222  is used to communicate Fl working fluid condensate (F 1  liquid) out of the condenser, and thereafter to pump  201  for re-use within the system. Port  223  is used to communicate a vaporous flow of the residual portion of F 3  to the compressor  204  where it is re-used, being identified as the F 2  working fluid. 
         [0029]    As is well known in the art, condensing is commonly performed by cooling the working fluid under designated states of temperature and pressure. This cooling process will generally involve a release of latent heat contained in the third working fluid F 3 . The condenser cools the F 3  fluid and thereby facilitates the condensing of the F 1  fluid contained within the F 3  fluid mixture. The F 1  portion therefore drops out as a liquid in the form of condensate  219 , and is collected in the condenser as F 1  fluid (liquid), and is available for reuse. This process leaves a residual portion of the F 3  working fluid. The residual portion of F 3  is a remaining portion of the one or more fluids previously comprising F 3  that exist after the F 1  condensate has been extracted from F 3 . With the F 1  (liquid) condensate and the residual portion of F 3  available as the F 2  working fluid, the process has essentially returned to its starting point. Thereafter, the entire process described above can be repeated in a continuous cycle. 
         [0030]    The performance of the condenser  212  is reliant on many factors, including the properties of the constituent fluids, the flow rates of the fluids, the ratios of the fluids, the condenser pressure and temperature, and hardware or apparatus physical configuration. These are all common variables that are well understood by those skilled in the art of condenser designs. The temperature and pressure conditions inside the condenser  212  are chosen so that the F 1  constituent part of F 3  is converted to a condensate within the condenser, while the second working fluid F 2  is not condensed. In other words, a residual portion of F 3  will remain in a vaporous state. Those skilled in the art will appreciate that this condensing process applied for purposes of separating F 1  from the residual portion of F 3  can be accomplished by choosing the first and second working fluid to have different thermal properties. Under some operational parameters it is possible to have the F 1 , F 2  and therefore the F 3  fluids all be the same fluid. In this case, simply a portion of the overall flow is converted back and forth between liquid and vapor states. 
         [0031]    In conventional Rankine cycle heat engines, the condensers can often be the most constraining part of the system. This is because it is necessary to completely condense 100% of the vapor that comprises the working fluid. Because of the difficulty in accomplishing 100% condensate, many systems will bleed a portion of the working fluid outside of the main system. This bleed process may include directly releasing working fluid to the atmosphere or to an independent reservoir that is outside of the primary condenser of the system. A key advantage of the current invention is the ability to not require a full condensate process. Accordingly, condenser  212  may not actually condense 100% of F 1  from the vaporous F 3  mixture. Advantageously, this condition is acceptable for purposes of the present invention, and a portion of F 1  can be permitted to remain mixed within a residual portion of F 3 . For purposes of the present description, any portion of the residual F 1 , either in the vapor or liquid form (carried in the fluid stream), after the condensing process, therefore remaining in F 2 , can be considered a constituent of F 2  by design. 
         [0032]    The present invention can include several possible configurations with respect to the overall condenser assembly  210 . In a first embodiment illustrated in  FIGS. 2-4 , the exemplary condenser assembly  210  includes a centrifugal liquid-vapor separator  212 , or liquid separator of similar method such as a centrifuge separator. The condensing process may be facilitated by spray cooling of the F 3  working fluid and exposing the flow to centrifugal separation. The centrifugal separator is a very efficient method of exposing the working fluid F 3  to a large effective surface area, however, for the passing flow within the overall architecture such separation alone is often insufficient. By direct contact cooling of the F 3  working flow returning from the expander  208 , this accelerates the potential to condense the overall flow within the separator  212 . The arrangement of the spraying or other cooling methods relative to the use of the separator may vary from design to design. Following are some examples of how this technique could be implemented. 
         [0033]    Port  221  receives the F 3  working fluid from the expander  208  and, prior to entering the separator  212 , the F 3  working fluid is exposed to a cooled fluid spray F 1 (cooled) provided via nozzle  234  or some other form of sprayer. Providing the cooled fluid F 1 (cooled) as a spray of droplets allows the fluid to quickly combine with and cool the F 3  working fluid. 
         [0034]    The F 1  working fluid within the separator  212  is used to produce the cooling spray. To facilitate such, a portion of the F 1  fluid is drawn through port  224  by a pump  231  or the like to an external chiller  230 . The F 1  fluid passes through the external chiller  230  and across a coolant  232  whereby heat is removed to the external environment as indicated at  235  and the cooled fluid F 1 (cooled) exits the chiller  230 . The coolant  232  can be a natural source of coolant (e.g. ambient air or cool water) or any other source of coolant (e.g. a cold side of a refrigerant loop). The cooled fluid F 1 (cooled) travels to the nozzle  234  and is sprayed into and combines with the F 3  working fluid with the combined fluid F 3 (cooled) then entering the centrifugal separator  212 . This method can be advantageous, as direct contact cooling could reduce the cost of systems relative to the use of heat exchangers that require large contact areas comprising copper or similar coils or finned surfaces. 
         [0035]    Referring to  FIGS. 3 and 4 , an exemplary centrifugal separator  212  is illustrated. The centrifugal separator  212  has a cylindrical body  240  divided by a centrifugal assembly  241 . The centrifugal assembly  241  is defined by a conical support wall  242  and centrifugal guide vanes  244 , e.g. similar in construct to that of a squirrel cage blower, supported by the support wall  242 . The guide vanes  244  have a closed end at the wall  242  and an opposite open end  243  aligned with port  221 . As such the laminar flow of the combined fluid F 3 (cooled) is directed into the guide vanes  244  through the open end  243  and then is directed into a radial flow as indicated by arrows  246  in  FIG. 4 . The radial flow  246  of the combined fluid F 3 (cooled) provides significant contact between the fluid F 3 (cooled) and the cooler body  240  of the centrifugal assembly  241 . Having higher pressure and surface contact with liquid forming against the outer wall, a significant portion of the F 1  fluid therefore drops out as a liquid in the form of condensate  219 , and is collected in the condenser as F 1  fluid (liquid), and is available for reuse. With the significant condensation between the support wall  242  and the incoming end wall  248  of the body  240 , this first portion of the separator  212  may be considered a wet zone  247 . 
         [0036]    The residual vapor flow passes from the wet zone  247  to the dry zone  257  through the one or more through passages  250  through the support wall. Additional liquid may drop out of the overall flow in the dry zone where this liquid condensate accumulates and is removed at  222   b . The process that starts from  221  and ends at the dry zone  257  may be repeated in some embodiments making it a two stage separator further increasing the time of contact of the fluid on the surfaces of the cylindrical body  240  before the residual portion of F 3  exits through the port  223 . This further maximizes the amount of F 1  working fluid which condenses out of the F 3  working fluid. 
         [0037]    The F 1  liquid working fluid and the F 3  residual fluid (F 2 ) then proceed as described with reference to  FIG. 1  and the cycle continues. 
         [0038]    A condenser assembly  210 ′ in accordance with another alternative embodiment is shown in  FIG. 5 . The condenser assembly  210 ′ is similar to the previous embodiment and utilizes a nozzle  234  to spray the F 3  working fluid with cooled fluid F 1 (fluid) before entering the centrifugal separator  212 ′. The centrifugal separator  212 ′ is similar to the previous embodiment, however, prior to entering the separator  212 ′ there is included an internal refrigeration cycle  236  to which the combined fluid F 3 (cooled) is passed prior to entering the centrifugal separator  212 ′. In this example, a portion of the F 1  working fluid having been collected from the separator is used as a refrigerant in the internal refrigeration cycle  236 . As used herein, the phrase “internal refrigeration cycle” refers to a refrigeration cycle in which the F 1  or a residual portion of F 3  is used as a refrigerant. The internal refrigeration cycle in  FIG. 5  facilitates transfer of thermal energy from the F 3  working fluid prior to entering the separator  212 ′. The internal refrigeration cycle  236  includes an expansion valve  237  (or other type of throttling means), positioned between the F 1  reservoir and the pump  231 . The expansion valve  237  is sized and configured to accomplish the desired cooling described herein, within the fluid capabilities of the flow provided. The cycle  236  may also include heat exchanger cooling members  238  prior to the pump  231 . In this example, the F 1  working fluid might be a common refrigerant such as R245fa or R134a where the overall refrigerant loop is effectively a common commercial design. In this case, the F 1  working fluid accumulated in the separator  212 ′ is drawn through the expansion valve  237  and the cooling members  238  before reaching the pump  231 . This process provides the ability to cool the incoming F 3  combined fluid and also has the potential to cool the external housing  240  where condensate forms. The heat is rejected at  235  by means of heat exchanger  230 , where the F 1  working is later returned to the expansion valve  234 . It is notable to point out that the condensate forms in this zone comprising coils  236  and is collected as liquid  219 . The condenser assembly  210 ′ otherwise works substantially the same as described in the previous embodiment. 
         [0039]    Referring to  FIG. 6 , a condenser assembly  210 ″ in accordance with another alternative embodiment of the invention will be described. The condenser assembly  210 ′″ includes a centrifugal separator  212 ″ and is substantially the same as the condenser assembly  210 ′ of the previous embodiment. In the present embodiment, the F 3  working fluid enters the separator  212 ″ and first passes across the internal refrigeration cycle  236 . Thereafter, the F 3  working fluid is sprayed with F 1 (cooled) cooling fluid via nozzle  234 . In all other aspects, the condenser assembly  210 ″ functions similar to the condenser assembly  210 ′. 
         [0040]    In this embodiment, the first cooling of the inbound flow is followed by spraying the residual flow, which in some applications will prove to increase the capacity to remove additional condensate from the flow. With the ability to place the cooling in the most advantageous locations relative to the return flow F 3 , the condensing operation can be tailored to the overall system needs. 
         [0041]    In the examples provided the use of the internal cooling loop and spraying the inbound F 3  flow has been shown. It is possible to have a configuration similar to  FIG. 2  where there is no internal refrigerant loop. In this case the inbound flow of F 3  simply passes into the fluid separator  212 , where the fluid separator could be cooled by external means providing the capacity condense out an adequate quantity of F 1  liquid to satisfy the overall cycle needs. Additionally, in the examples of  FIGS. 5 and 6  it is not required that the cooling provided by the internal refrigerant loop be used to provide the cooling members  238 . Here it is possible to have external sources of cooling provided equivalently at these general locations, thereby providing the same intended cooling result. 
         [0042]    It can be observed from the examples provided, there are many combinations of the spray locations, cooling locations and separation locations that could be configured for a specific application. It is the intent of this invention to show that by having the inherent capacity to pass a volume of the residual F 3  flow through the condenser assembly  210 , this overall process enables many methods of forming condensate form the initial inbound flow of F 3 , that are not afforded by the current art. 
         [0043]    The specifics of a particular condenser assembly design are reliant on many factors, including the properties of the constituent fluids, the flow rates of the fluids, the ratios of the fluids, the condenser pressure and temperature, and hardware or apparatus physical configuration. These are all common variables that are well understood by those skilled in the art of condenser designs. 
         [0044]    The first and second working fluids, and ratios thereof, should also be selected such that they work in concert with one another. In particular, the more rapid cooling of the second fluid (as compared to the first fluid) during the expansion process can facilitate the exchange of energy from the first fluid to the second fluid. This leaves the first fluid very close to the vapor to liquid transition point as it approaches the end of the expansion cycle. As the first working fluid condenses, it is therefore separated from the second working fluid and can be collected in the condenser. This unique fluid capability provides the means to tune the thermal take-up rates (heat addition/vaporization) and additionally the drop-out rates (condensate rates) of the fluids in operation. 
         [0045]    Various examples of the operation of exemplary heat engine are provided in applicant&#39;s co-pending U.S. application Ser. No. 13/098,603, filed May 2, 2011; Ser. No. 13/239,674, filed Sep. 22, 2011; Ser. No. 13/477,394, filed May 22, 2012; Ser. No. 13/533,497, filed Jun. 26, 2012; and Ser. No. 13/556,387, filed on Jul. 24, 2012, each of which is incorporated herein by reference. 
         [0046]    Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
         [0047]    All of the apparatus, methods and algorithms disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the invention has been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the apparatus, methods and sequence of steps of the method without departing from the concept, spirit and scope of the invention. More specifically, it will be apparent that certain components may be added to, combined with, or substituted for the components described herein while the same or similar results would be achieved. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as defined.