Heat pipe

An improved heat engine is disclosed. The heat engine comprises at least one heat pipe containing a working fluid flowing in a thermal cycle between vapor phase at an evaporator end and liquid phase at a condenser end. Heat pipe configurations for high-efficiency/high-performance heat engines are disclosed. The heat pipe may have an improved capillary structure configuration with characteristic pore sizes between 1μ and 1 nm (e.g. formed through nano- or micro-fabrication techniques) and a continuous or stepwise gradient in pore size along the capillary flow direction. The heat engine may have an improved generator assembly configuration that comprises an expander (e.g. rotary/turbine or reciprocating piston machine) and generator along with magnetic bearings, magnetic couplings and/or magnetic gearing. The expander-generator may be wholly or partially sealed within the heat pipe. A heat engine system (e.g. individual heat engine or array of heat engines in series and/or in parallel) for conversion of thermal energy to useful work (including heat engines operating from a common heat source) is also disclosed. The system can be installed in a vehicle or facility to generate electricity.

RELATED APPLICATIONS

U.S. patent application Ser. No. 13/724,412 entitled HEAT ENGINE, filed 21 Dec. 2012, is related to the present application which is herein incorporated by reference in its entirety.

U.S. patent application Ser. No. 13/724,567 entitled HEAT ENGINE SYSTEM, filed 21 Dec. 2012 , is related to the present application which is herein incorporated by reference in its entirety.

FIELD

The present invention relates to a heat pipe with a capillary structure. The present invention also relates to a heat engine with a capillary-pumped heat pipe. The present invention further relates to a heat engine with a generator. The present invention further relates to an improved-performance heat engine system.

BACKGROUND

A heat pipe configuration employing a working fluid in a phase-change thermal cycle to facilitate heat transfer between an evaporator section at one end (where the working fluid is heated to the vapor phase) and a condenser section at the other end (where the working fluid is condensed to the liquid phase) is known. Known heat pipe configurations provide a passage for flow of the vapor phase working fluid from the evaporator section to the condenser section and a passage for flow of the liquid phase working fluid from the condenser section to the evaporator section in a cycle. Such known heat pipe configurations operate in a generally continuous thermal cycle, absorbing heat from a heat source at the evaporator end where the working fluid is heated to vapor phase and rejecting heat at the condenser end where the working fluid is condensed to liquid phase.

It is known to provide a heat pipe in a generally cylindrical form having an exterior shell or wall; the interior of such known heat pipes will typically include for flow of the vapor phase fluid a centralized axial internal passage (for flow from evaporator to condenser) and for flow of the liquid phase fluid an annular or ring-shaped capillary or wick structure (for flow from condenser to evaporator). The central passage and capillary structure together provide the flow circuit for the working fluid during the continuous thermal cycle of operation for the conventional heat pipe.

It is known that within such a heat pipe a pressure differential is developed in the working fluid between the evaporator section (with the working fluid at higher pressure) and the condenser section (with the working fluid at lower pressure); the flow of the (higher pressure) vapor phase working fluid can be directed to perform useful work. It has been disclosed that a heat pipe may be configured to include an internal gas turbine (powered by flow of the vapor phase working fluid) coupled to a generator; such a heat pipe with turbine and generator may be used to produce electricity (i.e. electric power).

However, notwithstanding such known heat pipe configurations, there has not been widespread successful commercial and industrial application of heat pipe configurations for power generation.

SUMMARY

It would be advantageous to provide for an improved heat pipe configuration modified to achieve enhanced efficiency of operation to perform useful work (e.g. for power generation) in commercial and industrial applications. For example, it would be advantageous to provide for a capillary-pumped heat pipe configuration that has an enhanced capillary structure so that the heat pipe can operate with a higher pressure differential and higher temperature differential between the evaporator section and the condenser section and realize improved efficiency in operation (by extracting more power from the working fluid).

It would also be advantageous to provide for a heat engine that employs an improved heat pipe configuration and/or other design modifications that use and integrate technology enhancements to achieve improved performance and efficiency in operation. For example, it would be advantageous to provide for a heat engine that employs a capillary-pumped heat pipe configuration with an enhanced capillary structure. It would be advantageous to provide for a heat engine that employs an improved expander-generator configuration able to operate at higher pressure and higher speeds (e.g. higher rotational speed) to achieve higher performance, for example, through the use of a magnetic bearing system and/or magnetic coupling system. It would be advantageous to provide for a heat engine that has an integrated sealed construction (e.g. by using a magnetic coupling system rather than a mechanical coupling for transmission of rotational energy and torque) and/or modular construction to provide greater ease of installation and use and enhanced reliability.

It would further be advantageous to provide for a heat engine system that comprises one or more heat engines employing a heat pipe configured for improved efficiency and performance in operation. For example, it would be advantageous to provide for a heat engine system that uses a high-efficiency capillary-pumped heat pipe configuration. It would be advantageous to provide for a heat engine system that comprises an array of heat engines configured to use a common heat source and/or to generate electric power that can be delivered through a common outlet (e.g. shared bus). It would be advantageous to have a heat engine system comprising a heat engine array (e.g. using heat engines having a modular design) that can be configured use for in a wide variety of applications, including commercial, industrial, residential, consumer and other applications.

The present application relates to improved heat pipe configurations, to improved heat engine configurations, and to heat engine system configurations that can be used in a wide variety of applications including electric power generation.

The present invention also relates to improved configurations for capillary-pumped (i.e., “heat pipe”) heat engines, particularly including heat pipe heat engines comprising nanofabricated capillary structures (wicks) with characteristic capillary pore sizes between 1 μ and 1 nm, and with capillary structures having continuous or stepwise gradients in pore size along the capillary flow direction. Specific geometries for heat-pipe heat engines are disclosed.

The present invention further relates to improved configurations for capillary-pumped turbo-generators, including multistage turbines, magnetically-supported and magnetically-coupled turbines, integrated fully sealed turbo-generators, and magnetically-geared turbo-generators. The invention further relates to capillary-pumped heat engines comprising positive-displacement expanders using non-turbine mechanisms such as screw expanders, reciprocating piston devices, rotary engine configurations, etc.

The present invention further relates to capillary-pumped heat engine systems for conversion of thermal energy to useful work, including in parallel configurations of individual capillary-pumped heat engines, and arrays of heat engines operating from a common heat source.

DESCRIPTION

Referring toFIG. 1Aa power generation system100is shown schematically. System100comprises a heat engine system200comprising at least one heat engine, and a generator system300employing an expander and generator capable of generating power for delivery to a network or distribution system400. According to an exemplary embodiment, system100is configured to generate power such as electricity for use in a facility, vehicle, etc. System100also comprises a control system110, a heat exchanger180providing thermal energy from a heat source to the evaporator end of the heat engine, and a heat exchanger190to reject heat at the condenser end of the heat engine. Control system110comprises an instrumentation and control system120for heat engine system200and an instrumentation and control system130for generator system300(as well as instrumentation and control for other components of system100). The heat source to provide thermal energy to the heat engine system may be waste heat from a power plant, solar energy, geothermal energy or other available sources of heat, for example, from commercial or industrial processes. According to an exemplary embodiment shown schematically inFIG. 1A, heat engine system200comprises an array of heat engines210. According to other exemplary embodiments, the heat engine system will comprise at least one heat engine. See, e.g.,FIG. 25andFIGS. 30A through 30E.

Referring toFIG. 1B, according to an exemplary embodiment, each heat engine comprises a heat pipe that contains a working fluid that in a two-phase thermal cycle is evaporated into a (high pressure) vapor phase V at an evaporator end E and flows through a passage to a condenser end C where it is condensed to a (low pressure) liquid phase L; the liquid phase working fluid L flows through a flow path shown as a capillary structure (or wick) from the condenser end C to the evaporator end E to continue the cycle. Thermal energy is supplied at the evaporator end E of the heat pipe from heat exchanger180(to heat the working fluid to a vapor or gas); a heat exchanger190is used to recover heat at the condenser end C of the heat pipe (and to cool the working fluid to a liquid). According to an exemplary embodiment, the heat pipes may be sealed individually and each heat pipe will self-contain suitable supply of working fluid for operation over a useful period of life (e.g. with limited or routine maintenance).

As shown inFIGS. 1A and 1B, heat engine system200is coupled to generator system300. Generator system300is shown schematically inFIG. 1D. Generator system300comprises an expander310(e.g. a turbine system, turbo-machine, screw expander, root expander or gear pump, reciprocating piston expander, etc.) and a generator360(i.e. with associated power conditioning/converter electronics). As indicated inFIGS. 1A, 1B and 1C, in operation of the heat engine, useful work can be performed by the working fluid in vapor phase V (i.e. at high differential pressure and temperature) flowing from the evaporator section E of the heat pipe through expander310(e.g. a turbo-machine) to the condenser section C of the heat pipe. According to an exemplary embodiment, the expander produces a mechanical output (e.g. a rotating shaft) that serves as the input to an electric generator. Referring toFIG. 1D, generator system300comprises an interface500between expander310and generator360; interface500comprises (among other things) a bearing system600and a coupling system700to transmit torque/rotational energy.

According to an exemplary embodiment shown inFIG. 1C, the expander will be in the form of a turbine310aconfigured to perform mechanical work (i.e. driving a rotating shaft) acting through the interface to operate the generator (i.e. an electromagnetic generator). According to an exemplary embodiment, the interface may also comprise seals for any components (e.g. dynamic seals for shaft305) that extend through the shell of the heat pipe as well as a thermal management system (such as insulation) between the heat pipe and other external components of the heat engine or generator system that are adjacent to the heat pipe.

Definitions

The term “heat engine” generally refers to a device or apparatus that converts heat to useful work. A heat engine comprises a single assembly (i.e. “heat pipe” or “heat tube”) that has a hot end (coupled to a heat source) and a cold end (coupled to a heat sink). A heat engine can provide a mechanical output (i.e., a rotating, or possibly oscillating, member that can drive a mechanical load). A heat engine may comprise a heat pipe with an expander (e.g. turbine, turbine stage or turbine stages, turbo-machine, piston, screw expander, gear arrangement, etc.). A heat pipe configuration with an expander that forms a single assembly with a single output would operate as a heat engine (for example, with several wicks and evaporators feeding a single turbine assembly, or two heat pipes connected in series with turbines sharing a common shaft, etc.). Series-connected heat pipes with turbines that are not on a common shaft may be considered as either one heat engine or two heat engines.

“Generator” is a device or apparatus that converts mechanical power to electric power. A generator may include conventional (commutated electro-magnetic) generators, alternators, piezoelectric generators, etc. “Generator assembly” or “generator system” is a generator and any associated apparatus with the generator, such as bearings, thermal management/cooling systems, transformer(s), AC-DC inverter/converter, DC-DC converter, control electronics, couplings, gears/gearing, clutches, transmissions, etc. A “generator subsystem” is a set of generators.

An “integrated” generator is a generator where at least some components of the generator (usually the rotor) are inside a sealed heat pipe (e.g. not readily removable). An “integral” or “internal” generator is physically contained substantially or entirely inside a heat pipe (i.e. within the pressure envelope within the heat pipe), for example, with only electrical connections through the wall or shell of the heat pipe. A generator may be partially integrated if certain of the components are included within the heat pipe and certain of the components are external to the heat pipe, for example, with the rotor and shaft within the heat pipe and magnetic/electromagnetic elements (e.g. stator) and associated wiring/coils external to the heat pipe. A generator may also be partially integrated if it comprises rotating elements that are magnetically coupled to rotating elements of the expander (e.g. turbo-machine, etc.) within a sealed heat pipe (rather than with a dynamic mechanical connection). A “discrete” or “separate” generator would have substantially all components of the generator outside the heat pipe, for example, with a coupling through the shaft of the expander or turbo-machine within the heat pipe of the heat engine (e.g. in concept the discrete generator could be disconnected from the heat engine and attached to some other mechanical driver).

A “heat engine generator” or “heat engine system” refers to a heat engine in combination with the components of the generator (or other apparatus) to convert the mechanical output to electricity (e.g. includes the generator assembly). A “heat engine array” is a set of any number of heat engines installed at one location (e.g. configured to use a common heat source) an “assembly” or “subarray” can be a subset of a heat engine array with heat engines that are mechanically or otherwise connected together. For example, a heat engine array might have any number of heat engines (e.g., two or four or six or ten or sixteen, etc.) arranged in an assembly; a heat engine array may be modular insofar as it allows for selective removal and replacement of one or more heat engines from the array.

“Capillary” or “capillary structure” refers to any structure that can be used to transport liquid (such as the flow of working fluid in liquid phase) via capillary forces from a lower-temperature region such as the condenser section or reservoir to a higher temperature region such as the evaporator section. A capillary structure may also be referred to as a “wick” (as the term generally used to refer to a capillary structure fabricated from a woven material). The term “capillary structure” is to be given its broadest meaning to include a structure comprising grooves, screens or meshes, open-celled foams, porous materials such as sintered particles, nanoporous materials such as zeolites, aerogels, etc. and combinations. Capillary structures may be comprised of metal, plastic, glass, ceramics, fabric, or any other suitable material. According to an exemplary embodiment, the capillary structure will comprise a material that is “wetted” by the liquid of interest (i.e. that is at least partially hydrophilic) and which is compatible (i.e. capable of use and operation) within the operating conditions such as the temperature range to which the capillary structure is exposed. The configuration of the capillary structure in combination with the characteristics of the working fluid and operating conditions will typically determine the amount of surface energy/capillary force that is developed within the capillary structure and as a result the pressure differential that exists between the condenser section C and the evaporator section E of the heat pipe.

Capillary structures are characterized by a “feature size” or “pore size” or “channel size” which describes the size and scale over or through/across which capillary forces are exerted. For a given liquid, capillary forces (and therefore maximum pressure differentials) increase with decreasing pore size. Depending on the liquid properties, the flow resistance for a given liquid will generally also increase with decreasing pore size. For many capillary structures such as those made of sintered materials or open cell foams, the actual size of an individual pore or channel may not be uniform if examined at a given cross-section of the capillary structure (i.e. varying with some statistical distribution about a mean size), in which case the characteristic (or effective) pore size will generally be considered either the statistical mean size at the section, or some other function of the statistical distribution which characterizes the capillary properties. “Pore size” describes random or periodic patterns of holes, like grids or open-cell foams; “channel size” is used to describe more-or-less continuous channels, like etched or milled channels or stacks of fibers. “Pores” or “channels” or “features” and “pore size” or “channel size” and “feature size” are intended as general terms to have the broadest meaning.

A “capillary-pumped” heat engine is a heat pipe configured to operate as a heat engine (i.e. to perform useful work) and that comprises a capillary structure for flow of the working fluid from the condenser section to the evaporator section. The term “capillary-pumped heat engine system” refers to a heat engine system with at least one capillary-pumped heat engine (i.e. one or multiple heat engines) that within the heat pipe that comprises a capillary structure of some kind for flow of the liquid phase working fluid and also an expander such as a turbo-machine that can be used to perform useful work in an application.

The general terms are “microfabrication” for structures down to 1 μm, and “nanofabrication” for smaller structures. Microfabrication and nanofabrication techniques could be used to fabricate the capillary structure of a heat pipe according to exemplary and alternative embodiments.

“Lithography” is intended as a catch-all term for (e.g. by micro- or nano-fabrication) “writing” a pattern or shape on a surface or object and then by some further process fabricating a permanent structure. Lithographic techniques could be used to fabricate the capillary structure of a heat pipe.

“Photolithography” (and more generally “photoetching”) uses an optical process to expose a photosensitive resist applied to the surface (or object). In fabrication, either the exposed or unexposed resist is washed away (depending on the type of resist) and the underlying surface material is then removed (i.e. exposed material not protected by the resist). The material can be removed by chemical (i.e. wet) etching, plasma or reactive ion etching, ion milling, etc. There are variations such as e-beam lithography that can form structures as small as a few nanometers in size (e.g. for channels or holes, including “deep” holes (up to 100:1 aspect ratio)). Photolithography is an example of a lithographic technique that could be used to fabricate the capillary structure of a heat pipe.

As another example, “nanoimprint” lithography can be used to “print” a pattern of material on the surface using essentially a “stamping” process. Nanoimprint lithography is less expensive potentially than photolithography and can make features down to a few nanometers in size, but with less alignment precision than photolithography. Nanoimprint fabrication is capable of making submicron capillary structures. Nanoimprint fabrication techniques could be used to fabricate the capillary structure of a heat pipe.

“3-D printing” and specifically “3-D nanofabrication” comprises techniques for three-dimensional (3-D) structures (as opposed to features formed on a basically two-dimensional (2-D) surface). The 3-D fabrication techniques at present can make arbitrary shapes such as stacks of cylinders down to submicron scales (though currently at relatively high cost). Such 3-D fabrication techniques could be used to fabricate the capillary structure of a heat pipe.

“MEMS” (microelectromechanical systems) comprises a set of (mostly lithographic) techniques for making complex structures on micron scales, including gears, turbines, bearings, etc. (potentially at a relatively less expense than by other fabrication techniques). MEMS can be used to form both capillary structures and for small turbine parts, bearings, etc. “NEMS” (nanoelectromechanical systems) comprises the same techniques as MEMS but operates at smaller scale. MEMS and NEMS techniques could be used to fabricate the capillary structure of a heat pipe.

“Photonic crystal fibers” are glass-fiber structures with precise patterns of micron-to-submicron holes; as an example fabrication of precision capillary-type structures on industrial scale. Photonic crystal fiber fabrication techniques are precise (and typically more expensive). Such fabrication techniques could be used to fabricate the capillary structure of a heat pipe.

Exemplary Embodiments

As shown inFIGS. 1A through 1C, the heat engine system comprises a heat engine210comprising at least one heat pipe.

Referring toFIGS. 2, 3A and 4, a heat pipe208is shown schematically according to an exemplary embodiment. Heat pipe208comprises an outer casing or wall shown as shell212. Heat pipe208comprises an evaporator section E and a condenser section C. In evaporator section E, the working fluid is heated and evaporated into a vapor phase; the vapor has a generally central flow path shown as passage214from evaporator section E to condenser section C. In condenser section C, the working fluid is cooled and condensed into a liquid phase; the liquid flow has a flow path inside of the wall shown as a capillary structure220from condenser section C to evaporator section E.

As shown schematically inFIG. 3AwithFIGS. 3B through 3J, flow path220for the working fluid in the liquid phase within comprises features or pores221through the capillary structure in the wall of heat pipe208. Flow of the liquid phase working fluid is induced by a pumping action produced by the capillary forces that draw the liquid phase working fluid into the capillary structure at the condenser section C and through the capillary structure into the evaporator section E to be heated into vapor phase working fluid. As indicated inFIGS. 3B through 3D, according to an exemplary embodiment, the features or pores of the capillary structure may be generally consistent in size/form along the length of the heat pipe; as shown schematically inFIG. 3B, the heat pipe may have a flow path220with a generally uniform pore size221bat condenser section C and at the evaporator section E. As indicated schematically inFIGS. 3E through 3G, the features or pores of the capillary structure may be provided (e.g. in a mesh/fiber or grid structure) to vary in size/form along the length of the heat pipe; according to an exemplary embodiment shown inFIG. 3G, at condenser section C the heat pipe has a capillary structure with pore size221g; as shown inFIG. 3F, at an intermediate section between condenser section C and evaporator section E the heat pipe has a capillary structure with reduced pore size221f; as shown inFIG. 3E, at evaporator section E the heat pipe has a capillary structure with a further reduced pore size221e. As indicated schematically inFIGS. 3H through 3J, the features or pores of the capillary structure may be provided (e.g. in a material or structure) to vary in size/form along the length of the heat pipe; according to an exemplary embodiment shown inFIG. 3J, at condenser section C the heat pipe has a capillary structure with pore size221j; as shown inFIG. 3I, at an intermediate section between condenser section C and evaporator section H the heat pipe has a capillary structure with reduced pore size221i; as shown inFIG. 3H, at evaporator section E the heat pipe has a capillary structure with a further reduced pore size221h. According to a preferred embodiment indicated schematically inFIGS. 3E and 3H, the heat pipe with a flow path220with a reduced pore size221eand221h(e.g. approximately 10 nanometers) at the evaporator section will elevate the differential pressure of the working fluid (e.g. to a pressure as high as 100 bar).

According to any exemplary embodiment, the heat pipe and capillary structure may be constructed in a wide variety of forms and of a wide variety of materials, depending upon the application and operating conditions, the working fluid, desired pore/feature size, etc. The capillary structure may comprise powdered metal, sintered metal, metal foam, metal fiber or particles, fiberglass, grooves/slots, a screen or mesh, a nano-structure, a grain structure, zeolites (or other compound or molecular form providing a small-scale porous structure), etc. According to an alternative embodiment, the capillary structure may be provided with a coating or chemical treatment to enhance the hydrophilic properties (e.g. increasing the surface tension or surface energy that can be developed within the capillary structure per unit of area). According to other exemplary embodiments, the capillary structure may be fabricated using lithographic, nano-imprint/printing, 3-D printing, MEMS, NEMS, micro-crystal formation, or other micro- or nano-fabrication techniques that allow for the creation of submicron- and nano-sized pores or features for a capillary structure that is capable of developing a higher surface tension/capillary forces and of withstanding a higher pressure differential.

According to preferred embodiments, the capillary structure will be configured to operate over wide range of operating pressures and to support a relatively high pressure differential (e.g. ranging from at or below 0.1 bar to 100 bar or above) between the evaporator section and condenser section of the heat tube without high flow resistance for the liquid phase working fluid. The selection of the capillary structure will according to any preferred embodiment be made according to design objectives for the heat pipe. According to an exemplary embodiment, the working fluid may be any fluid suitable for use in a heat pipe under the operating conditions (e.g. temperature and pressure), for example, water or methanol (for applications at relatively lower temperature), mercury or lithium or inorganic salts (for applications at higher temperature), etc.

According to an exemplary embodiment shown schematically inFIG. 5A through 5C, the heat pipe may provide a housing or shell212athat is orthogonal in form (in the exterior). As shown inFIG. 5A, the heat pipe may provide a central passage214for the vapor and an integrated annular flow path for the liquid comprising grooves220x. As shown inFIGS. 5B and 5C, the heat pipe may comprise a passage214for the vapor that is separate and in parallel with the flow path220for the liquid (with the passage and flow path connected at the condenser end and evaporator end of the heat pipe, seeFIG. 1B). As shown inFIGS. 5B and 5C, the cross-section area of the flow path may vary according to design and performance criteria; as shown inFIG. 5B, the flow path220yis larger than as shown inFIG. 5Cthe flow path220z. According to an exemplary embodiment, the flow path for the liquid may comprise a capillary structure that is fabricated as an insert (e.g. having one section or multiple sections) sized and shaped to be fitted and installed securely within the shell or housing of the heat pipe.

Referring toFIGS. 6A through 6N and 7A through 7G, according to other exemplary embodiments (shown schematically), the heat pipe may have any of a wide variety of forms, sizes, shapes and configurations that would allow or result in a corresponding variety of forms, sizes, shapes and configurations of the flow paths for the vapor flow and for the liquid flow within the heat pipe (e.g. as provided by the capillary structure). As shown inFIGS. 6A through 6E, the pore size of the flow path for the liquid may vary from relatively large (seeFIG. 6A) or relatively small (seeFIG. 6E) while the annular cross-sectional area of the flow path remains generally consistent. As shown inFIGS. 6F through 6H, the dimensions of the annular flow path may vary in size from smaller (FIG. 6F) to larger (FIG. 6H). As shown inFIGS. 6K through 6M, the cross-section of the heat pipe may comprise a central flow path for the working fluid in liquid phase along with an annular flow path (as shown inFIGS. 6K and 6L) or without any other flow path (as shown inFIG. 6M). As shown inFIGS. 6I and 6J, the heat pipe may have a rectangular cross-section or other non-circular cross-section. As shown inFIGS. 6F through 6K, the size of the central flow path for the working fluid in vapor phase may be reduced or enlarged. As shown inFIGS. 6J and 6N, the flow path for the working fluid in liquid phase may be at opposed internal walls within the heat pipe. Other variations of the heat pipe configuration according to other exemplary embodiments are shown inFIGS. 7A through 7G(including an asymmetrical flow path configuration as in the heat pipe208g).

Referring toFIGS. 8 through 11 and 12A through 12H, a heat engine210comprising a heat pipe with an expander310(such as a turbo-machine) for a generator system is shown according to exemplary embodiments. As shown inFIGS. 1A through 1C and 12A, in operation of heat engine210the vapor phase working fluid that is heated at the evaporator section E of the heat pipe (at higher pressure) is capable of performing useful work if directed to flow through an expander310(e.g. for a turbo-machine with rotating turbine blades as shown inFIG. 1Cin the form of a mechanical output on a rotating shaft); the working fluid is then condensed to liquid phase at the condenser section C and will return (e.g. through the capillary structure) to the evaporator section E in a continuous cycle. As shown inFIG. 8, the heat engine may comprise a heat pipe208with an external shell212providing a generally linear form; as shown inFIG. 9, the heat engine may comprise a heat pipe208with an external shell having curved (or bent) sections212aand212bso that the heat pipe may be sized and configured to be installed in or to fit around physical obstacles. As shown inFIG. 10, the heat engine may comprise a heat pipe with an elongated chamber218aat the evaporator section E sized and configured to improve heat transfer in contact with a heat source180w; the heat pipe may also have and an elongated chamber216aat the condenser section C configured to collect liquid working fluid F. As shown inFIG. 11, the heat engine may comprise a heat pipe208with a coil section218bintended to enhance heat transfer at the evaporator section E with heat source180and a coil section216bintended to enhance heat transfer (e.g. with a coolant or fluid to be heated) at the condenser section C with a heat exchanger element as shown in table190w.

As shown inFIGS. 1C, 12G through 12I and 16A through 16C, it is generally known to install a turbo-machine in a heat pipe to configure a heat engine capable of performing useful (mechanical) work. For example, as shown representationally inFIGS. 1C and 12G through 12I, U.S. Patent Application Publication No. 2007/0151969 has disclosed configurations of a heat pipe having a turbo-machine310(installed within the heat pipe). As shown schematically and representationally inFIGS. 12A through 12F, according to exemplary embodiments, any of a wide variety of types of expanders (shown generally inFIG. 12A) can be installed in a heat pipe to configure a heat engine: a single-stage turbine310b(FIG. 12B), a multi-stage turbine310cwith rotating segments shown as rotors380cand fixed or stationary segments shown as stators370c(FIG. 12C), a screw expander310d(FIG. 12D), a root expander or gear pump310e(FIG. 12E), a reciprocating piston system310f(FIG. 12F). As indicated, according to other embodiments, any of a wide variety of expander devices or other turbo-machines may be used in the heat engine; any and all suitable expanders or other turbo-machines (of any kind, present and future) suitable for use in a heat pipe to configure a heat engine are intended to be within the scope of the present application.

Referring toFIGS. 13A through 13F, a heat pipe having a capillary structure for the flow path for the liquid phase of the working fluid with a varying feature/pore size along the length of the heat pipe is shown schematically according to an exemplary embodiment. Heat pipes208gand208hare each shown schematically to have a capillary structure configuration where the feature/pore size221wat the condenser section C is larger than the feature/pore size221zat the evaporator section E. As shown schematically inFIG. 13E, heat pipe208ghas a configuration with discrete stepped or staged transitions T in feature/pore size between condenser section C and evaporator section E. As shown schematically inFIG. 13F, heat pipe208hhas a configuration with a continuously varying feature/pore size between condenser section C and evaporator section E.

Referring toFIGS. 14A through 14C, a heat pipe208kis shown having a cylindrical form with an asymmetrical interior configuration. Heat pipe208khas a passage214kproviding a path for the vapor phase of the working fluid and a capillary structure configuration220kproviding a flow path for liquid phase of the working fluid on the inside of shell212k. As shown, a path220kfor the liquid phase of the working fluid is wider on one side of a passage214kfor the vapor phase of the working fluid; passage214kis off-center within the interior of heat pipe208k. As shown inFIG. 14C, the heat engine system can be configured with an array of heat engines oriented so that the asymmetrical interior configuration brings passages214kof heat pipes210kinto closer proximity when installed in a generator system300k(e.g. so that associated systems of the generator system are in closer proximity) to allow a more compact size for the heat engine.

As shown schematically inFIGS. 15A and 15B, according to alternative embodiments, the heat pipe may be configured so the passage for the vapor phase of the working fluid and the flow path for the liquid phase of the working fluid may vary in size/dimension (e.g. cross-sectional area for flow) along the length of the heat pipe. As shown inFIG. 15A, a heat pipe208mhas a passage214mthat is progressively reduced in size and a capillary structure configuration220mthat is progressively expanded in size along the length of the heat pipe from evaporator section/end E to condenser section/end C. As shown inFIG. 15B, a heat pipe208nhas a passage214nthat is enlarged in an intermediate section (e.g. to provide a space for installation of an expander, for example as shown inFIGS. 12D and 12E). The heat pipe will have a corresponding cross-section along its length as shown inFIGS. 15C through 15E. According to other exemplary and alternative embodiments, the heat pipe may have any of a wide variety of other configurations, including with variations in the external dimensions to accompany variations in the internal dimensions (e.g. enlargement of the width of the heat pipe accompanying enlargement of the vapor passage within the heat pipe so that the liquid flow path remains generally the same size).

As shown inFIGS. 12 through 12D and 16A through 16C, it is generally known to combine a turbo-generator with a heat pipe to configure a heat engine. For example, as shown representationally inFIGS. 1C and 12G through 12I, U.S. Patent Application Publication No. 2007/0151969 has disclosed configurations of a heat pipe having a turbine310.

As shown representationally inFIGS. 16A through 16C, U.S. Patent Application Publication No. 2008/0178589 has disclosed configurations of a turbine system associated with a generator system having an stator370with a coil372external to the heat pipe: (a) a heat pipe310dhaving a turbine310dwith rotating blades312dand associated magnetic elements382dinstalled on a shaft305dwith an internal mounting plate320d; (b) a turbine310ewith rotating blades312eand associated magnetic elements382einstalled on a shaft with an internal mounting fixture320e; and (c) a turbine310fwith rotating turbine blades312fand a separate rotating element380finstalled on a shaft305fon opposite sides of an internal mounting plate320f. As indicated, such heat pipe configurations and turbine system configurations can be adapted/modified and integrated within a heat engine/power generation system according to exemplary embodiments of the heat engine.

Adaptations and modifications of a generator system integrated within a heat pipe for a heat engine are shown schematically according to exemplary embodiments inFIG. 17A through 17H. According to an exemplary embodiment, the expander of the generator system comprises a turbine system with a turbine/fan with blades/vanes installed between the evaporator section and the condenser section of the heat pipe in the passage for vapor phase working fluid. The expander (e.g. turbine, fan, screw, gear, piston, etc.) installed in the heat pipe is configured to rotate (or translate) continuously as driven by a generally continuous flow of vapor phase working fluid from the evaporator section to the condenser section in the thermal/energy cycle of the heat pipe; liquid phase working fluid is returned from the condenser section to the evaporator section by flow path220of the heat pipe. According to any exemplary embodiment, the expander configuration can be of any suitable known configuration for the operating conditions (e.g. suitable for installation and reliably use within the heat pipe and exposure to the vapor phase working fluid and associated temperature ranges, pressure ranges, flow rates, etc.). According to a particularly preferred embodiment of a heat engine, a micro-turbine system may be installed in the heat pipe.

As shown schematically inFIGS. 17A through 17C, a expander310may comprise a one-stage system with single stage320a, a two-stage system with first stage320aand second stage320b, and a three-stage system with first stage320aand second stage320band third stage320c. (In each system each stage of the turbo-machine may be installed on a common shaft; according to an alternative embodiment, each stage may be installed on a separate shaft.) According to other exemplary embodiments, the number of turbine stages may be expanded if suitable within a particular application (i.e. based on operating conditions such as pressure and temperature, etc.).

As shown schematically inFIG. 17D, the generator system can be configured to have an internal rotating element380(e.g. representative of rotor of a generator associated with a rotating turbine element) and an internal stationary element370(e.g. representative of the stator of a generator) within the heat pipe of the heat engine.

As shown schematically inFIG. 17E, the generator system can be configured to have an internal rotating element380(e.g. representative of the rotor of a generator associated with a rotating turbine element) and an external stationary element shown as armature370(e.g. representative of the stator of a generator) relative to the heat pipe of the heat engine.

As shown schematically inFIG. 17F, the generator system can be configured to have an internal rotating element380(e.g. representative of the rotor of a generator associated with a rotating turbine element) with magnetic elements382(e.g. magnets installed at the tips of the blades of the turbine) within the heat pipe and an external stationary element (e.g. representative of the stator of a generator).

As shown schematically inFIG. 17G, a turbine system may be installed within a heat pipe having an asymmetrical configuration in which the passage for vapor phase working fluid is offset within the heat pipe and the capillary structure configuration providing the flow path for liquid phase working fluid is wider on one side of the passage than on the other. See alsoFIGS. 14A through 14F.

As shown schematically inFIG. 17H, the generator system can be configured to have an internal rotating element380z(e.g. representative of the rotor of a generator associated with a rotating expander element) that is constrained within a set of guides or ring bearing system340z(i.e. a shaftless rotor); the heat pipe is configured to provide a capillary structure with a central flow path220zfor the return of liquid phase working fluid from the condenser section to the evaporator section. As shown, the flow path for the liquid phase working fluid does not include any annular flow path in or adjacent to the shell of the heat pipe; the heat pipe can be configured more readily to allow the passage of the magnetic field from within the heat pipe (e.g. to the coil of an external generator) without absorption or attenuation.

As indicated inFIGS. 17A through 17H, the components/elements of the generator system within the heat pipe are subjected to the environment and operating conditions of heat and pressure within the heat pipe and according to any preferred embodiment are designed to operate suitably under the operating conditions; components/elements of the generator system within the heat pipe are also generally inaccessible for purposes of monitoring/inspection and service/maintenance and more difficult to connect to an instrumentation and control system. According to other exemplary alternative embodiments, the generator system may be configured so that certain components/elements are installed outside of the heat pipe rather than within the heat pipe.

As shown inFIGS. 18A and 18B, a heat pipe engine can be provided with a generator system having an interior expander310(e.g. turbo-machine powered by vapor phase working fluid) connected to an exterior generator360by a coupling system350. For example, as shown representationally inFIG. 18A, U.S. Pat. No. 4,186,559 has disclosed a system in which the turbine is separate from the generator (e.g. coupled by a gear system comprising a pair of bevel gears); as shown, the generator is out of the gas/vapor flow path and not subjected to the same environment and operating conditions as the turbine. Return flow of liquid (in an annular flow path) bypasses the turbine.

As shown inFIG. 19, it is known that rotating machinery such as generator system will typically require a bearing system. For example, as shown representationally inFIG. 19, U.S. Pat. No. 2,707,863 has disclosed a bearing system for a rotating expander310within an enclosure to equipment (not shown) in the exterior of the enclosure. A mechanical bearing system602for shaft305(shown representationally) is exterior to the enclosure. (Shaft305extends through a seal390of the enclosure.) According to an exemplary embodiment, as shown inFIG. 19, the system may be adapted to provide a thermal barrier213comprising insulating material213ibetween the enclosure (which typically will contain gas/vapor at elevated temperature and pressure) and the equipment connected to the expander310within the enclosure. As indicated inFIG. 19, heat may be transmitted from the expander to the equipment by conduction through the shaft; exposure to elevated temperatures may be detrimental to component/elements of the system, including the mechanical bearings.

According to other exemplary embodiments, the expander may be connected to the generator (or other equipment) by a coupling system comprising a magnetic coupling system700of a type shownFIGS. 20A and 20B. A shown schematically inFIG. 20A, a magnetic coupling system700comprises an interface or coupler710with a shaft705connected to a magnetic gear system720. As shown representationally inFIGS. 20B through 20D, and as indicated in U.S. Pat. No. 3,301,091 (see FIG. 1), U.S. Pat. No. 4,146,805 (see FIG. 1), and U.S. Pat. No. 3,683,249 (see FIG. 8), configurations for magnetic coupling systems that can be used to transmit torque and rotation from a shaft of a rotating machine in a sealed chamber to a shaft external to the chamber without direct or intermediate physical contact between the shafts are known generally.

As indicated schematically and representationally inFIGS. 20A through 20D, according to an exemplary embodiment, the heat engine can be provided with a magnetic coupling system700through which rotating shaft305of the expander within the heat pipe of the heat engine by interface or coupling730can be coupled to a shaft704for the generator through interface or coupling710(without any direct or indirect physical contact of the shafts). Rotation/torque of the output shaft of the turbine system installed within the heat pipe is transmitted through the (non-conducting) exterior wall of the heat pipe by the magnetic coupling system to produce a rotation of the input shaft for the magnetic coupling system that can be connected to the generator of the heat engine. As shown schematically and representationally inFIGS. 20B through 20D, torque/rotation of an internal shaft305(input) is transmitted through magnetic coupling system700to an external shaft705(output); magnetic elements735on interface730(rotor) on shaft305within an enclosure of the heat pipe of the heat engine engage magnetic elements715of interface710with shaft705located outside of the enclosure of the heat pipe. According to any preferred embodiment, no components within the enclosure of the heat pipe of heat engine210(e.g. the sealed heat pipe of a partially-integrated heat engine) are exposed; none of the components of the generator system external to enclosure are exposed to the pressures and temperatures within the heat pipe of the heat engine. (As shown inFIG. 20D, a bearing system602dfor shaft305may also be provided within enclosure210.) The magnetic coupling system may provide a rotational gear ratio, such that the external (driven) shaft or magnetic field rotates at a different rate than the driving rotor assembly; the ratio of rotation rates may be any integer multiple or rational fraction, such as 10×, 1/100×, or ⅜×. Examples of magnetic gearing providing such rotational rate ratios include products of Magnomatics Limited of Sheffield, United Kingdom. See also U.S. Pat. No. 3,301,091. Such integral magnetic gearing may allow a turbine or other rotary expander to operate in an optimum speed range while the generator operates in a different optimum speed range; for example, a small-diameter turbine may have an optimum speed of 180,000 RPM while the associated generator has an optimum speed of 3600 RPM. According to a particularly preferred embodiment, the components of magnetic systems may be of a type providing contactless and lubricant-free operation, as commercially available for example from Magnomatics Limited of Sheffield, United Kingdom (gearing systems), Magna Drive Corporation of Woodinville, Wash. (coupling systems), SKF AB of Goteborg, Sweden (active bearing systems), and other vendors.

Referring toFIGS. 21A through 21F, according to exemplary embodiments, bearing systems for rotating elements such as shaft305of a expander310of the generator system (e.g. with generator360) associated with the heat engine system are shown schematically. As shown inFIG. 21A, a bearing system600amay comprise a set of bearings602, for example, mechanical bearings (e.g. passive bearings). In certain applications, mechanical bearings may impose a practical or effective limitation on the maximum rotational speed of the turbine system and output shaft; according to an exemplary embodiment, magnetic bearings (e.g. active bearings) capable of effective operation at higher rotational speeds may employed in the generator system.

As shown inFIG. 21B, according to an exemplary embodiment, a bearing system500bmay comprise two sets of bearings, for example, a set of mechanical bearings604(passive bearings) and a set of magnetic bearings606(active bearings). Referring toFIG. 21F, a bearing system600fmay comprise a set of mechanical bearings604and a set of magnetic bearings606and a control system620; control system620can be configured so that the mechanical bearings are in operation at a rotational speed below a designated threshold (and at start-up and shut-down of the system); by operation of control system620, mechanical bearings604are disengaged and magnetic bearings606are activated at a rotational speed above the designated threshold. The use of a magnetic bearing system allows for higher (rotational) speed operation of the generator system and associated improvements in operational efficiency (e.g. through the reduction of friction by eliminating contact of certain moving parts and the associated efficiency losses); the presence of a mechanical bearing system allows for safe and efficient operation at lower speeds during start-up and shut-down and potentially as a backup system in the event of a malfunction of the system.

As shown schematically inFIG. 21C, a bearing system600cmay comprise a set of bearings502cinstalled with expander310within heat pipe212. According to a preferred embodiment, the bearing system will be configured to withstand (being sealed within) the environmental conditions within the heat pipe for a suitable period of time before failure (e.g. useful life). As shown inFIG. 21E, a bearing system600einstalled within heat pipe212may comprise a set of bearings602eand a thermal management system610(e.g. comprising a heat exchanger such as a thermo-electric cooler) to protect the bearing system from high temperatures associated with the vapor phase of the working fluid (e.g. to extend the useful life of the bearing system).

As indicated inFIG. 21D, a bearing system600dmay be installed outside and shielded/protected from the environmental conditions within heat pipe212. As shown schematically inFIG. 21D, bearing system600dmay comprise two sets of bearings (e.g. mechanical bearings504and magnetic bearings506) installed outside of heat pipe212. According to other alternative embodiments, the bearing system may comprise other configurations of bearing sets (e.g. a set of bearings inside the heat pipe and a set of bearings outside the heat pipe).

Referring toFIGS. 22A through 22D, a heat engine210comprising a heat pipe with an installed expander310powered by vapor phase working fluid is shown; coupling systems for the rotating elements of the generator system associated with the heat engine system such a shaft305coupling a expander310to other equipment (such as a generator360) are also shown schematically according to exemplary embodiments.

InFIG. 22A, a generator system associated with a heat engine is shown with a generator360aand expander310installed within the heat pipe; generator360ais coupled to an outlet400for distribution of power generated by the generator system. Generator360ais coupled to expander310by a coupling system shown as mechanical shaft305. Generator360aand coupling system305must be configured to withstand the environmental/operating conditions within the heat pipe. A suitable dynamic seal (e.g. pressure seal) is provided for shaft305to pass through the shell of heat engine210.

InFIG. 22B, a generator system associated with a heat engine is shown with a generator360binstalled outside of heat engine210and expander310installed within heat engine210; generator360bis coupled to outlet400for distribution of power generated by the generator system. Generator360bis coupled to expander310by a coupling system shown as mechanical shaft305. Generator360bdoes not need to be configured to withstand the environmental/operating conditions within heat engine210. A suitable dynamic seal390is required for rotating shaft305through the wall/shell of the heat pipe. Shaft305may by conduction transmit heat outside of the heat engine and components must be configured to withstand the associated (elevated) temperatures.

InFIGS. 22C and 22E, a generator system associated with a heat engine is shown schematically with a magnetic coupling system700coupled to expander310within heat engine210. Rotating shaft305couples expander310to a magnetic coupling or interface730within heat engine210. Interface710of magnetic coupling system700on the outside of the heat pipe engages interface730on the inside of the heat pipe without contact across a non-conducting end wall portion of the heat pipe. Interface730connected to expander310is coupled to interface710and to shaft705and magnetic gear system720of magnetic coupling system700to recover output rotational energy from the generator system associated with the heat engine system. As shown schematically inFIG. 22E(andFIGS. 20C and 20D), magnetic elements735interface730(within the heat pipe) engage magnetic elements715on interface710(external to the heat pipe) to transmit torque/rotation from (input) shaft305to (output) shaft705. The coupling system does not require any mechanical connection of components/elements across the walls of the heat pipe; no associated seals are required for the shaft and heat pipe; the shell of the heat pipe of the heat engine may remain sealed and intact. See alsoFIG. 17H.

InFIG. 22D, a generator system associated with a heat engine is shown with a generator360outside of the heat pipe coupled to expander310within the heat pipe. Rotating elements of turbine system210(e.g. magnetic elements of a rotor) energize the wire coil of a stator370and transmit electrical energy to generator360. The coupling system does not require any mechanical connection of components/elements across the walls of the heat pipe; no associated seals are required; the shell of the heat pipe may remain intact.

Referring toFIGS. 23A through 23C, a generator system associated with a heat engine210having two heat pipes for a corresponding heat engine coupled together in series is shown according to exemplary embodiments. As shown schematically, an expander310(e.g. turbo-machine) is installed within each heat pipe; the heat pipe for each heat engine is coupled through expander310by a common rotating shaft305(i.e. heat engines can be coupled at their respective condenser sections/ends or alternatively in series from condenser section of one heat pipe to evaporator section of the other). As shown schematically inFIG. 23A, shaft305coupling each expander310requires a dynamic seal390(e.g. a pressure-tight dynamic seal) suitable to allow passage of rotating shaft305through the end wall of each heat pipe208without allowing the escape of working fluid and or pressure drop in the heat tube of the heat engine. As shown schematically inFIG. 23B, a coupling system500bcoupled to rotating shaft305(e.g. a gearbox or clutch and/or with instrumentation and control system) can be installed between the seals390of each heat engine. As shown schematically inFIG. 23C, the seals and bearing system can be integrated into a combined coupling system500c(which can be provided with an instrumentation and control system and thermal management system, etc.). As indicated inFIGS. 23B/23C with reference toFIG. 18A, the coupling system may be configured to allow the coupling of an output shaft and/or generator system between each heat engine.

According to any exemplary embodiment, the heat engine system may be arranged in any of a wide variety of configurations. According to an exemplary embodiment of the heat engine system, the heat engines may generally be identical in form and in operation. According to other exemplary embodiments, separate individual heat engines coupled in the heat engine system may have a different form or configuration. Each heat engine may operate under different operating conditions/ranges, such as temperature and pressure; each heat pipe may employ a different working fluid. The heat engines each may have a different construction (e.g. materials of construction) or a different configuration (e.g. of paths/passages and capillary structure and construction) or a different size (e.g. diameter and length).

As shown schematically inFIG. 24A, a heat engine210may include two expanders310; as shown inFIG. 24B, in a series connection a heat engine210vhas a separate expander310and a heat engine210whas a separate expander310(each coupled by a common rotating shaft305). As shown, heat engines can be coupled in series on a common output shaft and configured so that the condenser sections of a set of adjacent heat engines abut and operate at the same rotational speed. According to an alternative embodiment, heat engines may be configured in series and staged so that the first heat engine in series operates at a higher temperature and is thermally coupled (as well as mechanically coupled) to the second heat engine in series which operates at a lower temperature (referenced to the condenser end of the first heat engine); the second heat engine in series may use a different working fluid or have a different internal form to compensate for the variations in operating conditions while achieving intended efficiencies of operation. According to other exemplary embodiments, the heat engines can be combined in series and/or in parallel to achieve operational efficiencies and to improve net performance.

The operation of the power generation system with a heat engine system is shown schematically inFIGS. 25A and 25B. The heat engine system comprises at least one heat engine; each heat engine comprising a heat pipe that contains a working fluid and has an evaporator section/end and a condenser section/end. Each heat engine has a passage for flow of vapor phase working fluid from the evaporator section to the condenser section and a flow path for return of liquid phase working fluid from the condenser section to the evaporator section. According to any exemplary embodiment of the power generation system, the heat engine will be comprise a generator and at least one expander (e.g. turbo-machine) will be installed within each heat pipe of the engine; the heat engine (operating in a continuous cycle) supplied with thermal energy from a heat source will power the generator system to generate electrical energy.

As shown inFIGS. 25A and 25B, a heat engine210is supplied thermal energy in the form of heat from heat exchanger180at the evaporator section to evaporate the working fluid into a vapor phase for flow through a central passage into the expander (e.g. turbo-machine) and then for return in liquid phase through a flow path inside of the walls of heat engine210. As shown inFIG. 25A, a heat engine210vmay include a single-stage expander310vhaving a single stage320a. As shown inFIG. 25B, a heat engine210wmay include a multi-stage expander310whaving a first stage320aand a second stage320band a third stage320c. According to a preferred embodiment, each stage of the expander may share a common shaft; according to an alternative embodiment, each stage may operate at a different rotational speed on separate shafts (e.g. the first stage at 100,000 RPM, the second stage at 25,000-50,000 RPM, and the third stage at 10,000 RPM). According to another alternative embodiment, each stage may comprise a different type of expander (see, e.g.,FIGS. 12A through 12H). Rotational energy from the expander310wis transmitted to a generator360where it is converted into power supplied to an outlet such as a distribution network400. According to an alternative embodiment, the generator system may comprise a micro-turbine with a compact alternator (e.g. configured similar to a brushless DC motor).

As shown schematically inFIGS. 26 and 27, the heat engine system may comprise heat engines210operating in parallel. As shown inFIG. 26, thermal energy is supplied to the evaporator section of heat engines at heat exchanger180; vapor phase working fluid powers an expander310in each of the heat engines; each of the turbine systems is coupled to a generation system360. Each heat engine also comprises a heat exchanger at the condenser section to recover rejected heat from the thermal cycle within each heat engine. As shown inFIG. 27, the heat engine system comprises three heat engines that in parallel operate two generator systems300xand300y; the heat engines share at the evaporator section a heat source shown as heat exchanger180x(to evaporate the working fluid into vapor phase for the turbine system) and share at the condenser section a heat exchanger190x(where heat is rejected as the working fluid is condensed to liquid phase). According to an exemplary embodiment, the generator can be installed with the expander in the heat pipe of the heat engine between the evaporator section and the condenser section.

Referring also toFIG. 31, a heat engine system200is shown schematically comprising heat engines210having thermal energy supplied in the form of heat at the evaporator section by heat exchanger180(e.g. connected to a heat source) to produce vapor phase working fluid and having thermal energy rejected at the condenser section by heat exchanger190jand heat exchanger190k(e.g. using cold plates or fluid/water-cooled) to condense the working fluid into liquid phase for return to the evaporator section. According to an exemplary embodiment, multiple heat engines may share a common heat exchanger which will tend to equalize the operating temperatures of the heat engines. According to another exemplary embodiment, a heat engine system may be configured so that the heat exchanger at the condenser section of one heat engine in the system operates as the heat exchanger at the evaporator section of another heat engine in the system (i.e. in thermal series) (with the heat pipes of each heat engine configured to operate efficiently over the resultant temperature ranges).

Referring toFIGS. 28A and 28B, a heat engine system220is shown having a reservoir290for working fluid supplying a set of heat engines210. In operation of the thermal cycle of the heat engine system, heat exchanger180supplies thermal energy to heat the working fluid from liquid phase L to vapor phase V to flow within passage214from evaporator end E through a generator system300to condenser end C. As shown inFIG. 28A, working fluid is condensed to liquid phase L at condenser end C and accumulates within reservoir290where by capillary forces the liquid will enter a capillary structure shown as flow path220within the heat pipe and return from the condenser end C to the evaporator end E. As shown inFIG. 28B, working fluid is condensed to liquid phase at low pressure at condenser end C and by a pump P pumped to an intermediate pressure into reservoir290where the liquid L will enter a capillary structure shown as tube182and flow into evaporator end E where the working fluid is evaporated to vapor phase at high pressure. (The pump supplies a portion of the pressure differential between the low pressure at the condenser section and the intermediate pressure in the reservoir; the capillary structure must be configured to support the remaining pressure differential between the intermediate pressure in the reservoir and the high pressure at evaporator end E.) According to a preferred embodiment, the thermal cycle and flow of working fluid from condenser end to evaporator end across the expander will operate substantially continuously. According to an exemplary embodiment, the heat engine system can be configured to use gravity to facilitate the operation, for example, to assist with the accumulation or flow of the liquid phase working fluid. According to an alternative embodiment, the system may be configured to operate in an artificial gravity or reduced-gravity or gravity-free environment (e.g. as may be encountered in a spacecraft).

Referring toFIGS. 29A and 29B and 30A through 30E, a power generation system with a heat engine system200and generator system300is shown schematically according to exemplary embodiments. As shown inFIGS. 29A and 29B, heat engine system200comprises a heat engine array having four heat engines210in parallel receiving thermal energy from a common heat exchanger/source180; generator system300comprises a set of expanders310powered by the working fluid within the heat tube of each heat engine and coupled to a common generator360. According to an exemplary embodiment shown inFIG. 29B, the heat engine array is configured with the expanders for each adjacent heat engine in a staggered orientation so that the heat engines may be located in a more compact arrangement (which reduces the size of the array in comparison with the embodiment shown inFIG. 29A).

InFIGS. 30A through 30C, the system comprises a heat engine system200with a heat engine array having eight heat engines210; the heat engine array is arranged to provide in-parallel sets of heat engines receiving thermal energy from a common heat exchanger/source180(FIG. 30A) from and individual corresponding heat source180(FIG. 30B) or from paired/shared heat source180(FIG. 30C). The systems also comprise a generator system300having a set of expanders310(e.g. a turbo-machine for each heat engine210) coupled to a generator360delivering power to a distribution system400. InFIG. 30D, the heat engine system200comprises a heat engine array with twenty four heat engines210arranged in eight parallel rows of three in-series heat engines. InFIG. 30E, a compact heat engine system is shown having an array with a total of eight heat engines (four rows of two in-series heat engines). As shown inFIGS. 30A and 30E, heat engine system200comprises an array of heat engines210that share a common heat exchanger system180and a common generator system300. As shown inFIG. 30D, each heat engine210has a corresponding individual heat exchanger180and turbo-generator300.

Each heat engine system200is connected to a generator system300(which will include associated power conditioning and conversion circuitry). As shown inFIGS. 30A and 30E, the heat engines210contribute to a common generator system; as shown inFIGS. 30B and 30D, each heat engine210(in a series) contributes to an individual generator; as shown inFIG. 30C, a set of two heat engines contribute to a shared generator system. Each generator system300is connected to the distribution network400.

Referring toFIGS. 33A and 33B, the power generation system100is shown having a base102onto which components are installed, for example, the heat engines210, generator system300and instrumentation and control system110. InFIG. 33A, base102is oriented in a horizontal direction. InFIG. 33B, base102is oriented in a vertical direction (e.g. as for mounting on a wall). Referring toFIG. 33A, the heat engine array of the heat engine system200comprises heat engines210both in parallel and in series.

According to an exemplary embodiment, the heat engines in parallel may be configured so that the temperature at the evaporator end of a heat engine is substantially the same as the temperature at the evaporator end of the adjacent heat engine (or heat engines); the heat engines in series may be configured end to end so that the temperature at the condenser end of a heat engine is substantially the same as the temperature at the evaporator end of the adjacent heat engine; the working fluid and capillary structure configuration of each heat engine can be modified for the operating conditions (e.g. including pressure, temperature and the heat of vaporization of the working fluid). According to an exemplary embodiment, the individual heat engines within the array may be identical or substantially identical in configuration; a heat engine array may have a modular construction that includes common elements such as heat engines that can be removed and replaced interchangeably (See, e.g.,FIG. 34). According to an alternative embodiment, the individual heat engines may receive thermal energy from different sources and may be operated under different conditions and/or using a different working fluid; the individual heat engines may have a different configuration or structure.

According an exemplary embodiment of the power generation system, each the turbine system and generator system will be configured to generate a direct current (DC) voltage; the DC voltage from each generator system can at distribution system400(i.e. cumulatively) be converted to an alternative current (AC) voltage for transmission. According to alternative embodiments the generator system may comprise an AC generator (i.e. generating an AC voltage). According to an alternative embodiment, the generator system may employ a micro-turbine (within the heat engine) and a compact generator (inside or exterior to the heat engine). According to any preferred embodiment, the power generation system will be configured to use conventional power generation equipment for the generator system.

Referring toFIGS. 32A through 32H, a heat engine system is shown schematically according to an alternative embodiment in which heat engines210rare attached to a base102rby a shaft305s; in operation, heat engines210rrotate and shaft305sis fixed relative to base102r(as indicated, alternate heat engines in the array may be configured to rotate in opposite directions to reduce net gyroscopic effects). According to an exemplary embodiment, the heat engines may be designed (e.g. shaped and configured) so that rotation of the heat engine (e.g. in a range of speeds below 10,000 RPM to above 100,000 RPM) induces by centrifugal force a pumping effect that facilitates the flow of the working fluid within the heat pipe. As shown schematically inFIG. 32B, a expander310rinstalled within heat engine210r; as shown inFIG. 32C, turbine blades312rof expander310rare fixed to the interior of heat engine210r; flow of vapor phase working fluid through expander310racting on turbine blades312rinduces heat engine210rto rotate around shaft305son bearings602r; as shown inFIG. 32H, shaft305sextends from the end of heat engine210rthrough a dynamic seal and bearing390rand is mounted to base102r. As shown inFIG. 32B, a flow path shown as capillary structure220ris provided along the inside wall of heat engine210rand around expander310r. As shown schematically inFIGS. 32D and 32F, a stator370of the generator system may comprise a cylinder attached to shaft305; as shown schematically inFIGS. 32E and 32G, according to an alternative embodiment, stator370of the generator system may comprise a ring installed around the exterior of heat engine (having an exterior wall made of a non-conducting material). As shown inFIGS. 32F and 32G, according to an alternative embodiment, shaft305of rotating heat engine210rmay be fixed to base102rwithout requiring any portion of shaft305to extend through the end wall of heat engine210r; a magnetic coupling system700secure shaft305sis secured (through non-conducting material and) through an interface or magnetic coupling to a shaft705. In operation, when the magnetic coupling system is engaged, the internal shaft305and the magnetic gear system720are engaged, magnetic gear system720can operate as a brake or lock to retain shaft305in a fixed position while heat engine210rrotates around fixed shaft305(seeFIG. 32A).

Referring toFIG. 34, a system is shown with a heat engine array using modular components. As shown, an individual heat engine can be removed and replaced (e.g. when expended or no longer improper or suitable operation, or for periodic testing/evolution, etc.). According to an exemplary embodiment, the system can be configured to remain in (partial) operation during removal/replacement of an individual heat engine; couplings250aand250bfor the heat engine can facilitate the efficient disconnection/removal and connection/installation of a heat engine. As shown, a bypass module250xcan be provided for the array when a heat engine is removed but there is no replacement heat engine; the bypass module can be configured to transmit torque/rotational energy and/or working fluid through the array.

Referring toFIG. 35, the heat engine system is shown having a set of heat engines configured in a three-dimensional array200x. The heat engines share a common heat source180and a common platform shown as base102. The array is shown with heat engines in series and parallel (i.e. a 2×3×3 array). According to a preferred embodiment, the array will have a compact form to facilitate efficient operation and use in wide variety of facility types, such as a commercial, industrial, residential, medical, office or other facility having a room10. According to other exemplary embodiments, the array may be configured in other combinations of parallel and/or series heat engines. As shown, arrangement of the heat engines in a three-dimensional array will allow convenient installation of the system in a facility close or adjacent to a heat source and/or close to a location where generated electric power is to be used. According to an exemplary embodiment, the array can be constructed using modular heat pipe units (e.g. sealed units) that are coupled thermally (e.g. by heat exchangers) and mechanically and/or electrically/magnetically (e.g. by a magnetic coupling system with magnetic gearing system and magnetic bearing system).

Referring toFIGS. 36 and 37, example applications of a power generation system100with heat engine system are shown schematically according to exemplary embodiments. As shown inFIGS. 36 and 37, a heat source H provides thermal energy for power generation system100(e.g. through heat exchanger system180shown inFIG. 1). According to exemplary embodiments, the heat engine system of the power generation system can be configured to use heat/thermal energy from any of a wide variety of sources (individually or in combination), for example, waste heat from a power plant operation, waste heat from engine or power plant exhaust, solar-generated thermal energy, geothermal energy, etc. According to a particularly preferred embodiment, the power generation system will be installed adjacent or near to a power plant; waste heat from the power plant will be a conveniently-available source of thermal energy for the heat engine system of the power generation system.

As shown inFIG. 36, power generation system100can be installed in a vehicle20. The vehicle may be a commercial vehicle (e.g. for transport of cargo), a work vehicle (e.g. for construction, agriculture, etc.), a passenger vehicle (e.g. personal/family car), a commercial passenger transport (e.g. taxi, shuttle, van, bus, etc.), rail transport (e.g. train for cargo and/or passengers, subway, trolley, elevated rail, monorail, etc.), or any other type of vehicle. According to an exemplary embodiment, the vehicle includes vehicle systems such as a drive system/transmission, battery system or other system for propulsion of the vehicle; the vehicle also includes other power systems such as a vehicle electrical system; the vehicle may also include auxiliary power systems (e.g. internal to the vehicle or connected external to the vehicle, such as equipment, appliances, accessories, etc.). As shown schematically, vehicle10includes a power plant1010(e.g. a combustion engine, electric motor system or other type of vehicle power plant) supplying power to vehicle systems1030(e.g. comprising the drive system, electrical system, auxiliary systems, etc.). Power generation system100is configured to supply power to vehicle systems1020(e.g. comprising a drive system, electrical system, auxiliary systems, etc.). For example, according to an exemplary embodiment where the vehicle is a hybrid-electric vehicle, power plant1010may comprise an internal combustion engine and vehicle systems1030comprise a drive train for the vehicle; vehicle systems1020may comprise an electric motor system with a battery system that is powered power generation system100. As indicated, any substantial source of heat in or on or in association with the vehicle may be a potential source of thermal energy for the heat engine system of the power generation system. According to a preferred embodiment, waste heat from the vehicle power plant will be a primary source of heat for the heat engine system; according to an alternative embodiment, solar-generated thermal energy may comprise a source of heat for the heat engine system.

As shown inFIG. 37, power generation system100may be installed in a vehicle or facility30. The facility may be any type of facility, such as a power plant, an industrial plant, commercial building, storage location, office building, government facility, recreational/entertainment venue, school/educational facility, residential building, home, etc. Facility20comprises a power plant1000with a source of fuel or energy S. Power plant1000comprises a source of heat H for the heat engine system of power generation system100. Power plant1000and power generation system100provide energy to a system D for distribution and use within the facility and/or for delivery to other locations outside of the facility. According to a particularly preferred embodiment, the facility is a power plant (e.g., an electric generation station powered by coal, natural gas, oil, nuclear energy, wind, solar energy, etc.) that supplies waste heat as the source of thermal energy for the heat engine system of the power generation system.

According to any preferred embodiment, the heat engine array and individual heat engines may be configured as needed according to the desired or intended operating conditions, availability of thermal energy, output requirements, etc. Individual heat engines or portions of the array of heat pipes may be configured to operate over varying operating conditions with varying working fluids and may have varying materials of construction, varying configurations of the passage for the vapor phase working fluid (see, e.g.,FIGS. 7A through 7G, 14A and 14B and 15A and 15B), varying configurations of the capillary structure (see, e.g.,FIGS. 3B through 3J, 5A through 5C and 6A through 6N), varying expander/turbo-machine configurations (see, e.g.FIGS. 14C, 12A through 12H), varying generator system configurations (see, e.g.,FIGS. 16A through 16C, 17D through 17F, 18A and 18B and 30A through 30E), varying seal/bearing and coupling/power transmission configurations (see, e.g.FIGS. 19, 20A through 20D, 21A through 21F, 22A through 22E, and 23A through 23C), in varying uses and applications (see, e.g.FIGS. 35, 36 and 37), etc.

It is important to note that the construction and arrangement of the elements of the inventions as described in system and method and as shown in the figures above is illustrative only. Although some embodiments of the present inventions have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible without materially departing from the novel teachings and advantages of the subject matter recited. Accordingly, all such modifications are intended to be included within the scope of the present inventions. Other substitutions, modifications, changes and omissions may be made in the design, variations in the arrangement or sequence of process/method steps, operating conditions and arrangement of the preferred and other exemplary embodiments without departing from the spirit of the present inventions.