US20130105110A1

US20130105110A1 - Integrated absorption-cycle refrigeration and power generation system

Info

Publication number: US20130105110A1
Application number: US13/284,776
Authority: US
Inventors: Frank Mills
Original assignee: Lockheed Martin Corp
Current assignee: Lockheed Martin Corp
Priority date: 2011-10-28
Filing date: 2011-10-28
Publication date: 2013-05-02

Abstract

An integrated power and refrigeration system is disclosed. The integrated system includes a solution comprising an absorber fluid and a working fluid that can be selectively dissolved into the absorber fluid. The integrated system also includes a first subsystem configured to extract heat from an external cooling load by pumping the solution through a vapor absorption cycle and a second subsystem configured to provide power by accepting a first portion of the solution from the first subsystem, extracting at least a portion of the working fluid from the accepted solution, heating the extracted working fluid, using the heated extracted working fluid to drive a turbine that is coupled to a power generator, and then returning the extracted working fluid and the remaining accepted solution to the first subsystem.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

Statement Regarding Federally Sponsored Research or Development

Not applicable.

BACKGROUND

1. Field
The present disclosure generally relates to systems and methods of generating refrigeration and power and, in particular, mobile systems that use waste heat to improve the performance of refrigeration and power generation systems.
2. Description of the Related Art
A traditional passive absorption-cycle refrigerator uses ammonia and water as ammonia will dissolve in water at certain temperatures and pressures. The ammonia can be extracted from the ammonia-water solution using heat while maintaining a constant pressure, as ammonia boils at −33 degrees C. at a pressure of 1 atmosphere. In a ground-based system, such as the propane-powered refrigerators used in recreational vehicles, there is no pump in the absorption-cycle system. The cooling cycle starts with liquefied ammonia entering an evaporator at room temperature wherein the ammonia boils from the heat extracted from the external cooling load. The gaseous ammonia is introduced at the bottom of an uphill series of tubes into which water is added at the top. The ammonia dissolves in the water, producing a ammonia/water solution that collects at the bottom and passes to a generator. In the generator, the ammonia/water solution is heated in a vertical column which releases the ammonia as bubbles in the liquid solution, which is now mainly water. The buoyancy of the ammonia bubbles force the remaining water up the column. At the top of the column, the water spills over into a tube that provides a pressure head to drive the water back to the top of the uphill series of tubes while the gaseous ammonia is carried off to a condenser that cools the ammonia to a liquid, thereby completing the vapor absorption cycle. Operation of this type of system depends on the partial pressure of ammonia to drive part of the cycle and hydrogen gas is provided in part of the system to maintain a constant total pressure while allowing the partial pressure of the ammonia to vary.
A traditional vapor-compression refrigerator uses a single refrigerant, such as Freon® or other haloalkane refrigerant, in a closed-loop system. Liquid refrigerant is provided to an expansion valve where it undergoes a reduction in pressure, causing part of the liquid refrigerant to evaporate and cool the remaining liquid. This cold liquid/gas fluid is carried to an evaporator coupled to the heat load wherein heat is extracted from the heat load by warming the liquid/gas fluid and evaporating the liquid to form a gas. This fluid is compressed to a higher pressure and temperature in a compressor and provided to the condenser which cools the fluid and provides it to the expansion valve, thereby completing the cycle.

SUMMARY

Traditional vapor-compression refrigeration system are driven by electrical power that is a significant load on an aircraft power generation system. It is desirable to provide refrigeration for equipment and personnel on aircraft using a reduced amount of electrical power. While it may be easier to compress a liquid, such as the ammonia-water solution used in a traditional vapor absorption cycle refrigeration system, to a specified pressure rather than to compress a gas to this same pressure, a traditional absorption-cycle refrigeration system will not operate in a variable-orientation and/or variable acceleration environment such as on-board an aircraft. As such, neither of the traditional vapor-compression or vapor absorption systems met this need.
There is growing interest in converting aircraft waste heat (e.g., engine heat dissipations, exhaust gas) into useable power or refrigeration. Conversion of such “low-grade” heat into electrical power or directly into refrigeration can be inherently inefficient if the size and weight of the conversion equipment is low.
The goal of this invention is to convert waste heat into useful power and/or refrigeration. The invention uses a working fluid that can be dissolved into an absorber fluid to reduce the amount of work required to pressurize the solution, and then extract the working fluid at the higher pressure to drive either a power turbine or provide cooling.
In certain embodiments, an integrated power and refrigeration system is disclosed. The integrated system includes a solution comprising an absorber fluid and a working fluid that can be selectively dissolved into the absorber fluid. The integrated system also includes a first subsystem configured to extract heat from an external cooling load by pumping the solution through a vapor absorption cycle and a second subsystem configured to provide power by accepting a first portion of the solution from the first subsystem, extracting at least a portion of the working fluid from the accepted solution, heating the extracted working fluid, using the heated extracted working fluid to drive a turbine that is coupled to a power generator, and then returning the extracted working fluid and the remaining accepted solution to the first subsystem.
In certain embodiments, an integrated power and refrigeration system is disclosed. The integrated system includes a solution comprising an absorber fluid and a working fluid selected such that the working fluid can be at least partially absorbed into the absorber fluid. The solution is characterized as a strong solution when the percentage of working fluid is greater than a determined value and characterized as a weak solution when the percentage of working fluid is less than or equal to the determined value. The integrated system includes a first pump configured to accept a flow of strong solution, increase the pressure of the accepted strong solution, and provide a flow of pressurized strong solution. The integrated system also includes a low-pressure generator coupled to a heat source. The low-pressure generator is configured to accept a first portion of the pressurized strong solution flow from the first pump, extract at least a portion of the working fluid from the strong solution using heat extracted from the heat source, and provide both a flow of pressurized working fluid and a flow of weak solution. The integrated system also includes a condenser coupled to a cooling medium. The condenser is configured to accept the pressurized working fluid from the low-pressure generator, decrease the temperature of the accepted pressurized working fluid by rejecting heat to the cooling medium, and provide a flow of cool pressurized working fluid. The integrated system also includes a throttle configured to accept the flow of cool pressurized working fluid from the condenser and reduce the pressure of the cool pressurized working fluid so as to vaporize a portion of the cool pressurized working fluid thereby reducing the temperature of the fluid, and provide a flow of cold working fluid. The integrated system also includes an evaporator coupled to an external cooling load. The evaporator is configured to accept the flow of cold working fluid from the throttle, vaporize at least a further portion of the cold working fluid using heat extracted from the external cooling load, and provide a flow of working fluid. The integrated system also includes a second pump configured to accept a second portion of the pressurized strong solution flow from the first pump, increase the pressure of the accepted pressurized strong solution, and provide a flow of highly pressurized strong solution. The integrated system also includes a high-pressure generator coupled to the heat source. The high-pressure generator is configured to accept the highly pressurized strong solution flow from the second pump, extract at least a portion of the working fluid from the strong solution using heat extracted from the heat source, and provide both a flow of highly pressurized working fluid and a flow of weak solution. The integrated system also includes a superheater coupled to the heat source. The superheater is configured to accept the highly pressurized working fluid from the high-pressure generator, increase the temperature of the accepted highly pressurized working fluid using heat extracted from the heat source, and provide a flow of hot highly pressurized working fluid. The integrated system also includes a power generator configured to provide power and a power turbine coupled to the power generator and the first and second pumps. The power turbine is configured to accept the hot highly pressurized working fluid, expand and extract work from the hot highly pressurized working fluid thereby driving the power generator and the first and second pumps, and provide a flow of working fluid. The integrated system also includes a first cooler coupled to the cooling medium. The first cooler is configured to accept the flows of working fluid from both the evaporator and the turbine, reject heat from the accepted working fluid to the cooling medium, and provide a flow of working fluid. The integrated system also includes a second cooler coupled to the cooling medium. The second cooler is configured to accept the flows of weak solution from both the low-pressure generator and the high-pressure generator, reject heat from the accepted weak solution to the cooling medium, and provide a flow of weak solution. The integrated system also includes an absorber configured to accept the flow of weak solution from the second cooler and the flow of working fluid from the first cooler, dissolve the working fluid in the weak solution to create a strong solution, and provide a flow of the strong solution to the first pump.
In certain embodiments, a method of providing power and refrigeration on a vehicle having an engine is disclosed. The method includes the steps of pressurizing a strong solution wherein the percentage of a working fluid dissolved in an absorber fluid is greater than a determined value, extracting at least a portion of the working fluid from the pressurized strong solution using heat extracted from the engine, condensing a first portion of the extracted working fluid by rejecting heat to a cooling medium, providing refrigeration to an external cooling load by evaporating the condensed working fluid using heat extracted from the external cooling load, heating a second portion of the extracted working fluid using heat extracted from the engine, and providing power by expanding and extracting work from the heated second portion of the extracted working fluid in a turbine that is coupled to a power generator.
In certain embodiments, a power system is disclosed that includes a solution comprising an absorber fluid and a working fluid selected such that the working fluid can be at least partially absorbed into the absorber fluid. The solution is characterized as a strong solution when the percentage of working fluid is greater than a determined value and characterized as a weak solution when the percentage of working fluid is less than or equal to the determined value. The power system also includes a pump configured to accept a flow of strong solution, increase the pressure of the accepted strong solution, and provide a flow of pressurized strong solution. The power system also includes a generator coupled to a heat source. The generator is configured to accept the pressurized strong solution flow from the pump, extract at least a portion of the working fluid from the strong solution using heat extracted from the heat source, and provide both a flow of pressurized working fluid and a flow of weak solution. The power system also includes a superheater coupled to the heat source. The superheater is configured to accept the pressurized working fluid flow from the generator, increase the temperature of the accepted pressurized working fluid using heat extracted from the heat source, and provide a flow of hot pressurized working fluid. The power system also includes a power generator configured to provide power and a power turbine coupled to the power generator and the pump. The power turbine is configured to accept the hot pressurized working fluid from the superheater, expand and extract work from the hot pressurized working fluid thereby driving the power generator and the pump, and provide a flow of expanded working fluid. The power system also includes an absorber configured to accept the flow of weak solution and the flow of expanded working fluid, dissolve the working fluid into the weak solution to create a strong solution, and provide a flow of the strong solution to the pump.
In certain embodiments, a refrigeration system is disclosed that includes a solution comprising an absorber fluid and a working fluid selected such that the working fluid can be at least partially absorbed into the absorber fluid. The solution is characterized as a strong solution when the percentage of working fluid is greater than a determined value and characterized as a weak solution when the percentage of working fluid is less than or equal to the determined value. The refrigeration system also includes a pump configured to accept a flow of strong solution, increase the pressure of the accepted strong solution, and provide a flow of pressurized strong solution. The refrigeration system also includes a generator coupled to a heat source. The generator is configured to accept a first portion of the pressurized strong solution flow from the pump, extract at least a portion of the working fluid from the strong solution using heat extracted from the heat source, and provide both a flow of pressurized working fluid and a flow of weak solution. The refrigeration system also includes a condenser coupled to a cooling medium. The condenser is configured to accept the pressurized working fluid from the generator, decrease the temperature of the accepted pressurized working fluid by rejecting heat to the cooling medium, and provide a flow of cool pressurized working fluid. The refrigeration system also includes a throttle configured to accept the flow of cool pressurized working fluid from the condenser and reduce the pressure of the cool pressurized working fluid so as to vaporize a portion of the cool pressurized working fluid thereby reducing the temperature of the fluid, and provide a flow of cold working fluid. The refrigeration system also includes an evaporator coupled to an external cooling load. The evaporator is configured to accept the flow of cold working fluid from the throttle, vaporize at least a further portion of the cold working fluid using heat extracted from the external cooling load, and provide a flow of working fluid. The refrigeration system also includes an absorber configured to accept the flow of working fluid from the evaporator and the flow of weak solution from the generator, dissolve the working fluid in the weak solution to create a strong solution, and provide a flow of the strong solution to the pump.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide further understanding and are incorporated in and constitute a part of this specification, illustrate disclosed embodiments and together with the description serve to explain the principles of the disclosed embodiments. In the drawings:

FIG. 1 is a schematic diagram of an exemplary integrated power and refrigeration system according to certain aspects of this disclosure.

FIG. 2 is another embodiment of the integrated power and refrigeration system according to certain aspects of this disclosure.

FIG. 3 is a schematic diagram of an another embodiment of the integrated power and refrigeration system according to certain aspects of this disclosure.

FIG. 4 is a schematic diagram of another embodiment of an integrated power and refrigeration system according to certain aspects of this disclosure.

FIG. 5 is a schematic diagram of another embodiment of an integrated power and refrigeration system according to certain aspects of this disclosure.

FIG. 6 is a schematic diagram of a power system in accordance with certain aspects of this disclosure.

FIG. 7 is a schematic diagram of a refrigeration system =according to certain aspects of this disclosure.

DETAILED DESCRIPTION

The following description discloses embodiments of an integrated power generation and refrigeration system driven by a heat source and a cooling medium. In certain embodiments, the heat source is waste heat from a device such as a propulsion engine. In certain embodiments, the cooling medium is ambient air.
The disclosed systems use a pair of fluids wherein one of the fluids, referred to herein as a “working fluid,” will dissolve into the other fluid, referred to as an “absorber fluid,” under certain conditions of temperature and pressure to form a solution. The working fluid can be extracted from a solution of the two fluids under certain other conditions of temperature and pressure. An exemplary pair of fluids is ammonia as the working fluid and water as the absorber fluid. Another pair of fluids uses water as the working fluid and lithium bromide as the absorber fluid.
The amount of working fluid dissolved into the absorber fluid is different at various points in the disclosed processes. The solution is characterized herein as a “strong solution” when the amount of the working fluid that is dissolved in the absorber fluid is greater than a determined percentage, and characterized herein as a “weak solution” when the amount of the working fluid that is dissolved in the absorber fluid is less than or equal to the determined percentage. The percentage of working fluid in the absorber fluid for the strong solution is a design choice for a particular system and the percentage of working fluid in the weak solution, and therefore the determined percentage that separates a weak solution from a strong solution, are related to other design choices, such as the mass flow rate of the strong solution and the energy input in the generator, that are made for that particular system.
In certain embodiments of an ammonia/water system, a strong solution comprises approximately 30% ammonia by weight and a weak solution comprises less than 25% ammonia by weight. In certain embodiments, the weak solution comprises less than 20% by weight. The amount of ammonia extracted as a “working fluid” from the strong solution, and therefore the composition of the weak solution, is a function of the mass flow rate of the strong solution and the energy input rate. In addition, the working fluid that is extracted from the strong solution may include some amount of the absorber fluid. For example, the flow of the working fluid extracted from a working solution of 30% ammonia may be 90% ammonia and 10% water. The water vapor will tend to condense into liquid in the condenser, resulting in a flow of gaseous working fluid from the condenser that is primarily ammonia and flow of liquid that is primarily water, which is directed into the weak solution.
Within this disclosure, the phrase “a highly pressurized solution” or fluid indicates only that the pressure of the solution is greater than that of the solution in “a pressurized solution” that is itself an indication that the pressure is greater than that of “a solution.” There is no implication of the amount of the difference in pressure between “highly pressurized” and “pressurized,” only that “highly pressurized” is greater than “pressurized.”
Within this disclosure, the phrase “a hot working fluid” or other fluid indicates only that the temperature of the “hot working fluid” solution is greater than that of “a working fluid.” There is no implication of the amount of the difference in temperature between a “hot” material and a material that lacks the adjective “hot,” only that the temperature of the “hot” material is greater than the temperature of the material that lacks the adjective “hot.”
Similarly, within this disclosure the phrase “a cold solution” indicates only that the temperature of the “cold” solution is less than that of “a cool solution” that is itself an indication that the temperature is less than that of “a solution.” There is no implication of the amount of the difference in temperature between a “cold” material and a “cool” material, only that the temperature of the “cold” material is less than the temperature of the “cool” material, and likewise for a “cool” material compared to a material lacking a temperature-related adjective. In certain embodiments of the present disclosure, a “cold” fluid may have a larger fraction of liquid than a “cool” fluid.
In the following schematic diagrams, lines carrying certain types of fluids are indicated by the type of line drawn in the schematic. For example, a thin black line indicates a line carrying a working fluid where a thick black line indicates a line carrying a weak solution. Each figure using these types of line includes a legend that depicts sample line types.
Within the scope of this disclosure, reference to a particular line in a schematic is considered equivalent and interchangeable with a reference to the type of fluid carried in that line. For example, the phrase “pressurized strong solution 42” is equivalent and interchangeable with “line 42.” In certain instances, the composition of the fluid in two lines may be identical but carry different reference indicators to indicate a difference in the pressure, temperature, or other physical characteristic of the fluids in the two lines.
In the following detailed description, numerous specific details are set forth to provide a full understanding of the present disclosure. It will be apparent, however, to one ordinarily skilled in the art that embodiments of the present disclosure may be practiced without some of the specific details. In other instances, well-known structures and techniques have not been shown in detail so as not to obscure the disclosure.
The method and system disclosed herein are presented in terms of systems in use on an aircraft propelled by a turbojet engine. This exemplary utilization of the disclosed system is sufficient to describe the attributes and use of the components of a variety of embodiments of the system. Utilization of the disclosed system is not limited to aircraft, however, and advantageous application may be found in other environments where waste heat is readily available, such as a diesel-engine train or ground-based locations having available heat but restricted in electrical power. Nothing in this disclosure shall be interpreted to limit the application of the disclosed systems and processes to an aircraft unless explicitly stated as such.
FIG. 1 is a schematic diagram of an exemplary integrated power and refrigeration system 10 according to certain aspects of this disclosure. In the diagram, beginning at the lower right, a pump 12 pressurizes a strong solution 40 of a working fluid dissolved in an absorber fluid, such as ammonia dissolved in water, and provides this pressurized strong solution 30 to a low-pressure generator 14. The low-pressure generator 14 is coupled to a heat source 6A, such as the waste heat from an on-board engine (not shown in FIG. 1), and uses this heat to extract the working fluid from the strong solution 30. The remaining weak solution 33 is returned to an absorber 22 as is discussed in greater detail below. The extracted pressurized working fluid 32 is provided to a condenser 16 that is coupled to a cooling medium 4. The working fluid 32 is cooled by rejecting heat from the working fluid 32 to the cooling medium 4 within the condenser 16, thereby converting at least a portion of the working fluid 32 to a liquid. The cool pressurized working fluid 34 passes to a flow control throttle 18 that reduces the pressure of the cool pressurized working fluid 34 so as to vaporize a portion of the cool pressurized working fluid 34 thereby reducing the temperature of the fluid, and provide a flow of cold working fluid 36. In the evaporator 20, heat is extracted from the cooling load 2 by evaporation of the liquid portion of the cold working fluid 36. This evaporated working fluid 38 passes to an absorber 22 that, as stated above, also receives the weak solution 33 from the low-pressure generator 14. In the absorber 22, the evaporated working fluid 38 and the weak solution 33 are combined and the evaporated working fluid 38 dissolves into the weak solution 33, thereby creating a strong solution 40. The strong solution 40 is provided by the absorber 22 back to the pump 12, thereby completing the vapor absorption cycle.
In certain embodiments, the portion of the circulation path from the pump 12 through the generator 14 to the throttle 18 is at a generally uniform first pressure while the portion of the path from the throttle 18 through the evaporator 20 to the pump 12 is at a generally uniform second pressure. The work required within pump 12 to increase the pressure of the liquid strong solution 40 that is at the second pressure to the first pressure of the pressurized strong solution 30 may be less than the work required to compress an amount of gas of the same thermal capacity from the second pressure to the first pressure.
In the system of FIG. 1, a power subsystem 50 provides power in addition to the refrigeration provided by the portion of the main system 10 that is not within the dashed-line box 50 in FIG. 1. A second pump 52 accepts a portion of the pressurized strong solution 30B and further pressurizes this liquid to form a highly pressurized strong solution 42 while the remaining pressurized strong solution 30A is directed to the low-pressure generator 14 as described above. The highly pressurized strong solution 42 is provided to a high-pressure generator 54. The high-pressure generator 54 is coupled to a heat source 6B and uses heat extracted from the heat source 6B to extract the highly pressurized working fluid 44 from the strong solution 42. The remaining weak solution 43 is returned to absorber 22. The extracted highly pressurized working fluid 44 travels to a superheater 56 that is coupled to a heat source 6C wherein the highly pressurized working fluid 44 is heated to form a hot highly pressurized working fluid 46. This hot highly pressurized working fluid 46 is provided to a turbine 58 wherein the hot highly pressurized working fluid 46 is expanded and work extracted from it so as to drive shaft 62 that is coupled to power generator 60 and, in certain embodiments, pumps 12 and 52. The expanded working fluid 48 is returned to the absorber 22 along with the evaporated working fluid 38 from the evaporator 20.
In certain embodiments, the heat sources 6A, 6B, and 6C are a common heat source. In certain embodiments, the heat sources 6A, 6B, and 6C are waste heat from an on-board engine (not shown in FIG. 1). In certain embodiments, the heat sources 6A, 6B, and 6C are waste heat from a propulsive engine (not shown in FIG. 1). In certain embodiments, the heat sources 6A, 6B, and 6C are exhaust gas from a turbojet or turbofan engine (not shown in FIG. 1). In certain embodiments, the heat sources 6A, 6B, and 6C are exhaust gas from a reciprocating-piston engine (not shown in FIG. 1).
As discussed above, the portion of the integrated system 100 that is not included in the power subsystem 50 forms a refrigeration subsystem 11. The refrigeration subsystem 11 extracts heat from an external cooling load using a vapor absorption cycle that comprises a pressurizing pump 12 to allow operation in a variable orientation and/or variable acceleration environment. The power subsystem 50 provides power by accepting a portion of the strong solution 30 from the refrigeration subsystem 11, extracting at least a portion of the working fluid from the accepted strong solution 30B, heating the extracted working fluid 44, expanding the heated extracted working fluid 46 to extract work thereby driving a turbine 58 that is coupled to a power generator 60, and then returning the expanded working fluid 48 and the remaining accepted solution 43 to the refrigeration subsystem 11 where the expanded working fluid 48 is combined with the vaporized working fluid 38 and the remaining accepted solution 43 is combined with the weak solution 33.
FIG. 2 is another embodiment 10A of the integrated power and refrigeration system according to certain aspects of this disclosure. In the system 10A, a pair of coolers 23A and 23B have been added to the system. Each cooler 23A and 23B are coupled to a cooling medium 4B and 4C, respectively, and pre-cool the returning evaporated working fluid 38 and the weak solution 33, respectively. The cooled working fluid 39 and the cold weak solution 35 coming out of the coolers 23A and 23B are then provided to the absorber 22, wherein the cooled working fluid 39 and weak solution 35 are mixed as described in FIG. 1.
In certain embodiments, the cooling media 4A, 4B, and 4C are a common cooling medium. In certain embodiments, the cooling media 4A, 4B, and 4C are all stream of ambient air drawn from the ambient environment (not shown in FIG. 2), for example a ram air duct mounted on an exterior of an aircraft.
FIG. 3 is a schematic diagram of an another embodiment 10B of the integrated power and refrigeration system according to certain aspects of this disclosure. In this embodiment, the heat source is a stream of exhaust gas 106 from a propulsion engine 20. In this embodiment, the exhaust gas 106 is split into three portions. A portion 106A is coupled to the low-pressure generator 14 and provides the heat therein to separate the working fluid 32 from the strong solution 30A. A second portion 106B is coupled to the high-pressure generator 54 and provides the heat therein to extract the working fluid 44 from the strong solution 42. A third portion 106C is coupled to the superheater 56 and therein heats the highly-pressurized working fluid 44 to become a hot, highly-pressurized working fluid 46 that is then provided to turbine 58. A flow of cooling media 104 is air drawn from the ambient airflow 80A and, after passing through condenser 16, is exhausted to the ambient airflow 80B that is, in certain embodiments, downstream of the ambient airflow 80A.
FIG. 4 is a schematic diagram of another embodiment 10C of an integrated power and refrigeration system according to certain aspects of this disclosure. In this embodiment, heat exchangers 210, 220 are used in place of direct heating and cooling of the generators 14 and 54, condenser 16, and superheater 56 so as to decouple the exhaust gas 106 from the components that require a heat source and ambient airflow 80 from the components that require a cooling medium. In this embodiment 10C, the heat exchanger 210 has three circulating paths 206A, 206B, and 206C coupled to the low-pressure generator 14, the high-pressure generator 54 and the superheater 56, respectively. A heat transfer fluid 206 circulates through these three lines 206A, 206B, and 206 thereby providing heat extracted from the exhaust gas 106 to each of the three components 14, 54, and 56. Similarly, a heat exchanger 220 is coupled to the ambient airflow 80. In this embodiment, cooling medium 204 is also provided to absorber 22 to assist in the absorption of the cooled working fluid 39 by the weak solution 35 in the absorber 22. The heat exchanger 220 is coupled to four re-circulating lines 204A-204D that provide a cooling medium 204 to the four components 16, 23A, 23B, and 22 that require cooling herein. As the cooling medium 204 circulates through these four paths 204A-204D, each of the components 16, 23A, 23B, and 22 rejects heat to the cooling medium 204 that is then returned to the heat exchanger 220. In certain embodiments, the cooling medium is provided to the components 16, 23A, 23B, and 22 via other configurations of paths 204A-204D.
In certain embodiments, the heat exchanger 210 is incorporated into the body of an engine and the heat transfer fluid 206 circulated through cooling channels (not shown in FIG. 4) in the body of engine 20 and thereby extracts heat from the engine 20. In certain embodiments, the heat transfer fluid 206 is ambient air that is passed through cooling channels of the body of engine 20 and then passed through the low-pressure generator 14, high-pressure generator 54, and superheater 56 and then exhausted to the ambient airflow 80B.
In certain embodiments, a flow of fuel (not shown in FIG. 4) replaces the ambient airflow 80 as the heat sink coupled to heat exchanger 220. In certain embodiments, fuel is received from a fuel reservoir, passes through the heat exchanger 220 wherein heat is rejected from the cooling medium 204 to the fuel, and then the fuel is directed back to the fuel reservoir. In certain embodiments, a portion of the fuel exiting the heat exchanger 220 is directed to engine 20 or to another engine (not shown in FIG. 4).
FIG. 5 is a schematic diagram of another embodiment 10D of an integrated power and refrigeration system according to certain aspects of this disclosure. In system 10D, regenerative heat exchangers 300 and 302 have been added to the subsystems 11 and 50B. Regenerative heat exchanger 300 has been added in conjunction with low-pressure generator 14, such that the weak solution 33 that is expelled from the low-pressure generator 14 warms the incoming strong solution 30A thereby improving the efficiency of the refrigeration subsystem 11. Similarly, a regenerative heat exchanger 302 has been added in association with high-pressure generator 54 wherein the weak solution 43 exiting the high-pressure generator 54 is warming the highly-pressurized strong solution 42 thereby improving the efficiency of the power subsystem 50B. The weak solutions 33, 43 exiting from the regenerative heat exchangers 300, 302 are combined in the refrigeration subsystem 11 and directed to absorber 22.
In the embodiment of FIG. 5, streams 104A, 104B of ambient air are directed from a source of ambient airflow 80A, such as an inlet of a ram air scoop (not shown in FIG. 5) through the absorber 22 and the condenser 16 and then exhausted to the ambient airflow 80B, such as an outlet of a ram air scoop.
FIG. 6 is a schematic diagram of a power system 400 in accordance with certain aspects of this disclosure. In this system, the pump 52 accepts a strong solution 40 from absorber 22 and provides a highly-pressurized strong solution 42 directly to generator 54 which provides highly pressurized working fluid 44 to superheater 56. Hot, highly pressurized working fluid 46 from the superheater 56 passes to the turbine 58 and, after being expanded and work extracted therefrom, the expanded working fluid 48 is directed back to absorber 22, which combines the working fluid 48 and weak solution 43 to create the strong solution 40 provided to pump 52. In this embodiment, the heat source used by the generator 54 and super heater 56 is provided as exhaust gas 106 from engine 20 and exhausted after use to the ambient airflow 80B. In certain embodiments, a cooling medium (not shown in FIG. 6) is provided to the absorber 22 similar to that shown in FIG. 5.
FIG. 7 is a schematic diagram of a refrigeration system 500 according to certain aspects of this disclosure. The refrigerator system 500 consists of a pump 12 that provides pressurized strong solution 30 to generator 14 which in turn provides pressurized working fluid 32 to condenser 16 and cool pressurized working fluid 34 to throttle 18 and liquid working fluid 36 to evaporator 20 as before. The weak solution 33 leaving generator 14 is provided to absorber 22 as is the evaporated working fluid 38 from the evaporator 20. In the absorber 22, the working fluid 38 and weak solution 33 are combined to produce the strong solution 40 that is provided back to pump 12. In this embodiment, the heat source used by generator 14 is a stream of exhaust gas 106 from engine 20 and the cooling media used by condenser 16 is a stream of ambient air 104 coupled to the condenser 16. In both cases, the hot exhaust gas leaving generator 14 and the warmed air flow 104 leaving condenser 16 are both exhausted into the ambient airflow 80B.
The concepts disclosed herein provide a system and method of providing one or both of refrigeration and power using an absorption cycle system. In certain embodiments, the power and refrigeration systems are integrated and share one or more components, thus simplifying the system design as well as potentially reducing the size, weight, and cost of the integrated system. In certain embodiments, waste heat from an engine or other existing heat source may be used to operate either or both of the power and refrigeration systems. In certain embodiments, a portion of the exhaust gas is passed through the various components that require a heat source.
It will be obvious to those of skill in the art that the various elements of the disclosed embodiments of the present disclosure may be combined in other configurations to provide either or both of power and refrigeration. In addition, it will be apparent that various types of power generators, for example an electrical generator, an electrical alternator, or a hydraulic pump, may be used alone or together in the disclosed system.
The previous description is provided to enable a person of ordinary skill in the art to practice the various aspects described herein. While the foregoing has described what are considered to be the best mode and/or other examples, it is understood that various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but are to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” Unless specifically stated otherwise, the terms “a set” and “some” refer to one or more. Pronouns in the masculine (e.g., his) include the feminine and neuter gender (e.g., her and its) and vice versa. Headings and subheadings, if any, are used for convenience only and do not limit the invention.
It is understood that the specific order or hierarchy of steps in the processes disclosed is an illustration of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the processes may be rearranged. Some of the steps may be performed simultaneously. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented.
Terms such as “top,” “bottom,” “front,” “rear” and the like as used in this disclosure should be understood as referring to an arbitrary frame of reference, rather than to the ordinary gravitational frame of reference. Thus, a top surface, a bottom surface, a front surface, and a rear surface may extend upwardly, downwardly, diagonally, or horizontally in a gravitational frame of reference.
A phrase such as an “aspect” does not imply that such aspect is essential to the subject technology or that such aspect applies to all configurations of the subject technology. A disclosure relating to an aspect may apply to all configurations, or one or more configurations. A phrase such as an aspect may refer to one or more aspects and vice versa. A phrase such as an “embodiment” does not imply that such embodiment is essential to the subject technology or that such embodiment applies to all configurations of the subject technology. A disclosure relating to an embodiment may apply to all embodiments, or one or more embodiments. A phrase such an embodiment may refer to one or more embodiments and vice versa.
The word “exemplary” is used herein to mean “serving as an example or illustration.” Any aspect or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or designs.
All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.” Furthermore, to the extent that the term “include,” “have,” or the like is used in the description or the claims, such term is intended to be inclusive in a manner similar to the term “comprise” as “comprise” is interpreted when employed as a transitional word in a claim.

Claims

What is claimed is:

1. An integrated power and refrigeration system comprising:

a solution comprising an absorber fluid and a working fluid that can be selectively dissolved into the absorber fluid;

a first subsystem configured to extract heat from an external cooling load by pumping the solution through a vapor absorption cycle; and

a second subsystem configured to provide power by accepting a first portion of the solution from the first subsystem, extracting at least a portion of the working fluid from the accepted solution, heating the extracted working fluid, expanding the heated extracted working fluid to extract work thereby driving a turbine that is coupled to a power generator, and then returning the expanded working fluid and the remaining accepted solution to the first subsystem.

2. The system of claim 1, wherein:

the solution is characterized as a strong solution when the amount of the working fluid that is dissolved in the absorber fluid is greater than a determined percentage and characterized as a weak solution when the amount of the working fluid that is dissolved in the absorber fluid is less than or equal to the determined percentage; and

the first subsystem comprises:

a first pump configured to accept a strong solution, increase the pressure of the accepted strong solution, and provide a pressurized strong solution; and

a first generator thermally coupled to an engine, the first generator configured to accept a second portion of the pressurized strong solution, extract a portion of the working fluid from the accepted pressurized strong solution using heat extracted from the engine, and provide both a pressurized working fluid and a weak solution.

3. The system of claim 2, wherein the second subsystem comprises:

a second generator thermally coupled to the engine, the second generator configured to accept the first portion of the pressurized strong solution received from the first subsystem, extract a portion of the working fluid from the pressurized strong solution using heat extracted from the propulsive engine, and provide both a pressurized working fluid and a weak solution;

a superheater thermally coupled to the engine, the superheater configured to accept the pressurized working fluid, heat the pressurized working fluid using heat extracted from the engine, and provide a hot pressurized working fluid;

a power generator configured to provide power; and

a turbine coupled to the power generator, the turbine configured to accept the hot pressurized working fluid from the superheater, expand and extract work from the hot pressurized working fluid thereby driving the power generator, and provide a working fluid.

4. The system of claim 3, wherein the turbine is further coupled to the first pump and a portion of the work extracted from the hot pressurized working fluid drives the first pump.

5. The system of claim 4, wherein:

the second subsystem further comprises a second pump configured to accept the first portion of pressurized strong solution received from the first subsystem, increase the pressure of the accepted pressurized strong solution, and provide a highly pressurized strong solution;

the second generator is configured to accept the highly pressurized strong solution from the second pump in place of the pressurized strong solution from the first subsystem and to provide a highly pressurized working fluid in place of the pressurized working fluid;

the superheater is configured to accept the highly pressurized working fluid in place of the pressurized working fluid and to provide a hot highly pressurized working fluid in place of the hot pressurized working fluid;

the turbine is further coupled to the second pump; and

the turbine is configured to accept the hot highly pressurized working fluid in place of the hot pressurized working fluid and expand and extract work from the hot highly pressurized working fluid thereby driving the power generator and the first and second pumps.

6. The system of claim 4, wherein:

the first subsystem further comprises an absorber configured to accept the working fluid from both the evaporator and the turbine and the weak solution from both the first and second generators, dissolve the accepted working fluid in the accepted weak solution, and provide a strong solution to the first pump.

7. The system of claim 2, wherein the engine is a Brayton-cycle engine.

8. The system of claim 2, wherein the engine is a Otto-cycle engine.

9. The system of claim 2, wherein the engine is a Diesel-cycle engine.

10. An integrated power and refrigeration system comprising:

a solution comprising an absorber fluid and a working fluid selected such that the working fluid can be at least partially absorbed into the absorber fluid, wherein the solution is characterized as a strong solution when the percentage of working fluid is greater than a determined value and characterized as a weak solution when the percentage of working fluid is less than or equal to the determined value;

a first pump configured to accept a flow of strong solution, increase the pressure of the accepted strong solution, and provide a flow of pressurized strong solution;

a low-pressure generator coupled to a heat source, the low-pressure generator configured to accept a first portion of the pressurized strong solution flow from the first pump, extract at least a portion of the working fluid from the strong solution using heat extracted from the heat source, and provide both a flow of pressurized working fluid and a flow of weak solution;

a condenser coupled to a cooling medium, the condenser configured to accept the pressurized working fluid from the low-pressure generator, decrease the temperature of the accepted pressurized working fluid by rejecting heat to the cooling medium, and provide a flow of cool pressurized working fluid;

a throttle configured to accept the flow of cool pressurized working fluid from the condenser and reduce the pressure of the cool pressurized working fluid so as to vaporize a portion of the cool pressurized working fluid thereby reducing the temperature of the fluid, and provide a flow of cold working fluid;

an evaporator coupled to an external cooling load, the evaporator configured to accept the flow of cold working fluid from the throttle, vaporize at least a further portion of the cold working fluid using heat extracted from the external cooling load, and provide a flow of working fluid;

a second pump configured to accept a second portion of the pressurized strong solution flow from the first pump, increase the pressure of the accepted pressurized strong solution, and provide a flow of highly pressurized strong solution;

a high-pressure generator coupled to the heat source, the high-pressure generator configured to accept the highly pressurized strong solution flow from the second pump, extract at least a portion of the working fluid from the strong solution using heat extracted from the heat source, and provide both a flow of highly pressurized working fluid and a flow of weak solution;

a superheater coupled to the heat source, the superheater configured to accept the highly pressurized working fluid from the high-pressure generator, increase the temperature of the accepted highly pressurized working fluid using heat extracted from the heat source, and provide a flow of hot highly pressurized working fluid;

a power generator configured to provide power;

a power turbine coupled to the power generator and the first and second pumps, the power turbine configured to accept the hot highly pressurized working fluid, expand and extract work from the hot highly pressurized working fluid thereby driving the power generator and the first and second pumps, and provide a flow of working fluid;

a first cooler coupled to the cooling medium, the first cooler configured to accept the flows of working fluid from both the evaporator and the turbine, reject heat from the accepted working fluid to the cooling medium, and provide a flow of working fluid;

a second cooler coupled to the cooling medium, the second cooler configured to accept the flows of weak solution from both the low-pressure generator and the high-pressure generator, reject heat from the accepted weak solution to the cooling medium, and provide a flow of weak solution; and

an absorber configured to accept the flow of weak solution from the second cooler and the flow of working fluid from the first cooler, dissolve the working fluid in the weak solution to create a strong solution, and provide a flow of the strong solution to the first pump.

11. The system of claim 10, wherein the heat source is waste heat from an engine.

12. The system of claim 10, wherein the cooling medium is ambient air.

13. A method of providing power and refrigeration on a vehicle having an engine, the method comprising the steps of:

pressurizing a strong solution wherein the percentage of a working fluid dissolved in an absorber fluid is greater than a determined value;

extracting at least a portion of the working fluid from the pressurized strong solution using heat extracted from the engine;

condensing a first portion of the extracted working fluid by rejecting heat to a cooling medium;

providing refrigeration to an external cooling load by evaporating the condensed working fluid using heat extracted from the external cooling load;

heating a second portion of the extracted working fluid using heat extracted from the engine; and

providing power by expanding and extracting work from the heated second portion of the extracted working fluid in a turbine that is coupled to a power generator.

14. The method of claim 13, wherein the step of providing power comprises driving a first pump to perform the step of pressurizing the strong solution.

15. The method of claim 13, further comprising the steps of:

further pressurizing a portion of the pressurized strong solution to form a highly pressurized strong solution; and

extracting a highly pressurized working fluid from the highly pressurized strong solution using heat extracted from the engine;

wherein:

the step of heating a second portion of the extracted working fluid comprises heating the highly pressurized working fluid; and

the step of providing power comprises expanding and extracting work from the heated highly pressurized working fluid.

16. The method of claim 15, wherein the step of providing power comprises driving a second pump to perform the step of further pressurizing a portion of the pressurized strong solution.

17. The method of claim 13, further comprising the step of:

dissolving the evaporated working fluid that was used to provide cooling and the expanded working fluid that was used to provide power in a weak solution wherein the percentage of the working fluid dissolved in the absorber fluid is less than or equal to the determined value that was formed from the strong solution when the working fluid was extracted.

18. A power system comprising:

a pump configured to accept a flow of strong solution, increase the pressure of the accepted strong solution, and provide a flow of pressurized strong solution;

a generator coupled to a heat source, the generator configured to accept the pressurized strong solution flow from the pump, extract at least a portion of the working fluid from the strong solution using heat extracted from the heat source, and provide both a flow of pressurized working fluid and a flow of weak solution;

a superheater coupled to the heat source, the superheater configured to accept the pressurized working fluid flow from the generator, increase the temperature of the accepted pressurized working fluid using heat extracted from the heat source, and provide a flow of hot pressurized working fluid;

a power generator configured to provide power;

a power turbine coupled to the power generator and the pump, the power turbine configured to accept the hot pressurized working fluid from the superheater, expand and extract work from the hot pressurized working fluid thereby driving the power generator and the pump, and provide a flow of expanded working fluid; and

an absorber configured to accept the flow of weak solution and the flow of expanded working fluid, dissolve the working fluid into the weak solution to create a strong solution, and provide a flow of the strong solution to the pump.

19. The power system of claim 18, wherein the heat source is waste heat from an engine.

20. A refrigeration system comprising:

a generator coupled to a heat source, the generator configured to accept a first portion of the pressurized strong solution flow from the pump, extract at least a portion of the working fluid from the strong solution using heat extracted from the heat source, and provide both a flow of pressurized working fluid and a flow of weak solution;

a condenser coupled to a cooling medium, the condenser configured to accept the pressurized working fluid from the generator, decrease the temperature of the accepted pressurized working fluid by rejecting heat to the cooling medium, and provide a flow of cool pressurized working fluid;

an absorber configured to accept the flow of working fluid from the evaporator and the flow of weak solution from the generator, dissolve the working fluid in the weak solution to create a strong solution, and provide a flow of the strong solution to the pump.

21. The power system of claim 20, wherein the heat source is waste heat from an engine.