| WHAT IS CLAIMED IS 1. A vehicle having a temperature controlled cabin, the vehicle including a fuel storage tank, an engine configured to convert the fuel to propulsion energy, and a system for cooling the cabin; the system including; a boiler in which the fuel is converted to thermal energy to convert a motive refrigerant to a motive pressure and temperature; an ejector configured to mix the motive refrigerant with a working refrigerant; an evaporator positioned to transfer heat from the cabin to the working refrigerant; wherein the ejector comprises: a converging-diverging nozzle through which the motive refrigerant enters at the motive pressure and from which the motive refrigerant exits at a lower pressure; a mixing section in which the motive refrigerant is mixed with the working refrigerant which exits the evaporator and enters the ejector at an evaporator pressure; and a diffusion section which further mixes the refrigerants so that the motive refrigerant becomes part of the working refrigerant, and wherein the working refrigerant exits the ejector at a pressure lower than the motive pressure but higher than the evaporator pressure and; a condenser located to transfer heat from the working refrigerant exiting the ejector to an area outside the cabin, wherein the working refrigerant enters the condenser at a condensing pressure. 2. The vehicle of claim 1, further comprising a heat transfer loop comprising; a liquid heat transfer fluid; a pump to circulate the heat transfer fluid through at least one heat exchanger; wherein the at least one heat exchanger is configured to transfer heat from a first source of thermal energy to the heat transfer fluid; and the boiler where thermal energy is transferred from the heat transfer fluid to the motive refrigerant. 3. The vehicle of claim 2, further comprising a second heat exchanger configured to transfer thermal energy from a second source of thermal energy to the heat transfer fluid. 4. The vehicle of claim 3, wherein the first and second sources of thermal energy each comprise one of the following: an engine cooling system; an engine exhaust system; a cooling system of an auxiliary engine; an exhaust system of the auxiliary engine, a fuel-burning auxiliary heater device or system, or an electric resistance element. 5. The vehicle of claim 3, further comprising a controller, wherein the controller is configured to actuate the second source of thermal energy such that when the engine is running, thermal energy is provided from the first source of thermal energy to the heat transfer fluid, and such that when the engine is not running, thermal energy is provided from the second source of thermal energy to the heat transfer fluid. 6. The vehicle of claim 2, further comprising a second heat exchanger configured to transfer thermal energy from the heat transfer fluid to the cabin. 7. The vehicle of claim 1, which further includes an electrically-powered compressor. 8. The vehicle of claim 7 wherein the electrically-powered compressor is positioned between the evaporator and the ejector and is configured to raise the pressure of the working refrigerant from the evaporator pressure to a pressure higher than the evaporator pressure but lower than the condensing pressure. 9. The vehicle of claim 7, wherein the electrically-powered compressor is positioned between the condenser and the ejector and is configured to raise the pressure of the working refrigerant exiting the ejector to the condensing pressure. 10. The vehicle of claim 7, further comprising an electrical storage device for providing power to the electrically-powered compressor. 11. The vehicle of claim 10, further comprising a connection configured to connect to an off vehicle electrical energy source for providing power to the electrically-powered compressor. 12. The vehicle of claim 7, wherein the electrically-powered compressor is a variable-speed compressor. 13. The vehicle of claim 12, in which the flow capacity of the variable-speed compressor is dynamically adjustable. 14. The vehicle of claim 7, further comprising a controller, wherein the controller is configured to direct electrical power to the electrically-powered compressor from an alternator of the engine when the engine is running and from an electrical storage device or off vehicle electrical energy source when the engine is not running. 15. An air conditioning system for a vehicle having a temperature controlled cabin, the vehicle including a fuel storage tank, an engine configured to convert the fuel to propulsion energy, and a system for cooling the cabin; the system including; a boiler in which the fuel is converted to thermal energy that converts a motive refrigerant from a liquid state to a vapor having a motive pressure and motive temperature; an evaporator positioned to transfer heat from the cabin to a working refrigerant and wherein the working refrigerant exits the evaporator at an evaporator pressure; an ejector configured to mix the motive refrigerant and the working refrigerant so that the motive refrigerant becomes part of the working refrigerant and wherein the working refrigerant exits the ejector at a pressure which is lower than the motive pressure but higher than the evaporator pressure; a condenser located to transfer heat from the working refrigerant exiting the ejector to an area outside the cabin; wherein the working refrigerant enters the condenser at a condensing pressure and a variable speed electrically powered compressor configured to raise the pressure of the working refrigerant in order to improve the efficiency of the ejector. 16. The system of claim 15, wherein compressor is located between the evaporator and the ejector, and wherein the compressor is configured to raise the pressure of the working refrigerant to a pressure lower than the condensing pressure. 17. The system of claim 15, wherein compressor is located between the ejector and the compressor, and wherein the compressor is configured to raise the pressure of the working refrigerant to a pressure lower than the motive pressure. 18. The vehicle of claim 15, further comprising a controller configured to control at least one of thermal energy transfer from first and second thermal energy sources to the boiler via a heat transfer fluid and the source of electrical power to the electrically powered compressor. 19. The vehicle of claim 18, wherein the controller is configured to actuate the second thermal energy source such that when the engine is running, thermal energy is provided from the first source of thermal energy to the heat transfer fluid, and such that when the engine is not running, thermal energy is provided from the second source of thermal energy to the heat transfer fluid. 20. The vehicle of claim 18, wherein the controller is configured to direct electrical power to the electrically powered compressor from an alternator of the engine when the engine is running and from an electrical storage device or off vehicle electrical energy source when the engine is not running. |
SYSTEM
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to and the benefit of U.S. Provisional Application No. 61/176,063, filed May 6, 2009, which is incorporated by reference herein in its entirety.
BACKGROUND
[0002] For trucks, cars, trains, trolleys and vans and other forms of vehicular transport, the ability to maintain a comfortable interior air temperature with minimal expenditure of energy is increasingly important. The state of the art for heating these vehicles is one or more of three methods - heat exchange between air and engine coolant, electrically-powered Rankin-cycle heat pumps and fossil fuel- fired burners. Of these, capturing waste heat from the engine coolant is the most energy efficient and electrically-powered heat pumps the least efficient. The state of the art for cooling the air in a vehicle is a Rankin-cycle system using either a compressor which is belt-driven from the propulsion engine or one that is electrically-powered. The electrical power for these compressors comes from either energy which has been stored in a battery or from an alternator driven by an internal combustion engine. None of these cooling systems can make use of waste heat and all suffer multiple loss-inducing power conversions from their original fossil fuel power source.
[0003] Recent legislation and the rising cost of diesel fuel have created demand for what is popularly known as "no-idle" truck cab air conditioning systems. These systems are used to control the temperature of the sleeping cabin of Class 8 type long-haul trucks during the driver's mandatory rest stops without running the main propulsion engine. Since heating of the cabs is also required, separate heating systems are also commonly installed. The air conditioning systems typically use electric compressors. The electricity is supplied by running small diesel- powered generators or, increasingly often, by batteries. The batteries are later recharged once the truck resumes its journey by an alternator attached to the main propulsion engine. The battery-powered air conditioning is preferred to the small diesel generators because of the lower purchase, maintenance and operating cost as well as the reduction in diesel air emissions and noise. However, the battery systems themselves suffer from substantial and costly technical problems. These include the initial cost, replacement cost and substantial added weight associated with carrying and using the batteries. The battery pack used to power in a typical no- idle truck air conditioning system will cost $1,000 USD, weigh over 400 pounds and require replacement every two years.
[0004] Because these vehicles also operate in very cold climates, they are typically outfitted with a stand-alone heating system. These heaters burn fuel (generally diesel) drawn from the same storage tank as the propulsion engine in a separate burner. The heaters may disperse their heat directly to the air or indirectly through a two-loop hydronic system.
[0005] In addition to class 8 trucks, many other types of vehicles also require energy efficient air conditioning and heating to be available when the propulsion engine is not running. Such vehicles include but are not limited to local and regional delivery trucks, ambulances, utility service vehicles, hybrid-electric cars and trucks, cranes, construction and other off-road vehicles, trains, trolleys, busses and marine vessels.
[0006] While not in common use, a number of systems have been developed that attempt to capture waste heat from a propulsion engine for the purpose of powering the air conditioning system of a vehicle. These systems have at their foundation two different technologies - absorption and steam ejector. Absorption technology has been successfully applied to many land-based applications but, in general, has proven to be too large, heavy, and problematic for vehicular use. Therefore, absorption technology is outside the scope of consideration in this application. The second technology - cooling air through the use of steam-powered ejectors - has been applied to passenger trains to divert a portion of the locomotive steam pressure for air conditioning use. While such systems provide effective cooling, they did so by decreasing the amount of power available for propulsion. [0007] Other systems have attempted to avoid the propulsion issue in air conditioning systems for internal combustion automobiles be generating steam for an ejector system by capturing heat from the water cooling system of the propulsion engine that would otherwise be wasted. In addition to providing cooling, the entire system may be simplified with the addition of control valves that allow many of the cooling components to be used to redirect heat into the vehicle when operating in cold climates. To engage a heating mode, the boiled refrigerant vapor is bypassed around the ejector and directly into the evaporator. Such systems make no provision for supplying heat to the refrigerant boiler other than by capturing it from the cooling system of the vehicle driving engine, precluding use of the system when heat is insufficient in either quality and/or quantity from the source. The flow of refrigerant into the evaporator is accomplished indirectly by monitoring the level of refrigerant in the condenser. This refrigerant flow suffers the disadvantage of having no means to compensate for the volume change associated with leaks or normal expansion and contraction as temperature changes.
[0008] Other systems may capture waste engine heat but without relying on the engine cooling system as the source for that heat. The system captures heat from the engine exhaust stream. While exhaust heat is advantageous in that it is more quickly available upon engine startup and is likely to be of higher quality, it suffers many of the same limitations as reliance on coolant heat, including extreme variable with engine load and the inability to function without the engine running. The system may attempt to overcome the inherent control problems by offering additional control valves and a second evaporator.
[0009] Some systems may improve the level of efficiency and control by separating liquid drops from the vapor steam using a heat exchanger design that more efficiently captures waste heat from the engine exhaust stream and by adding a recirculation means between the condenser and the evaporator and generator. While the systems strive to improve overall efficiency, there is no suggestion for increasing the quantity or quality of heat available to drive the system beyond that which can be captured from the exhaust of the vehicle propulsion engine. [0010] A total energy system for domestic, commercial, and light-industrial applications may endeavor to capture and transfer heat from multiple sources to a building's conventional hydronic heating system. The heating system stores the heat and supplements it, as required, for use at a time air conditioning is required to drive a heat operated air ejector air conditioning system. While the system theoretically possesses the capability of capturing and utilizing heat from multiple sources, it is inherently problematic to actually do use multiple sources efficiently with this system because of the limitation imposed by the use of a common storage point and temperature. Any devices producing waste heat below the storage temperature will not be able to be captured and stored while the air conditioning system is operating. To avoid this problem entirely may not be possible and minimizing the problem may impose significant system design constraints that would increase cost and reduce potential application of the technology. An example of these design constraints is illustrated when one closely examines usage of solar energy, waste heat from refrigeration, and an internal combustion engine together to provide heat. In such a system, the heat may only be transferred to the common storage tank if that storage tank were below the operating temperature of the individual devices. Therefore, by necessity, the storage temperature must always be below the operating temperature of the lowest temperature device in the system. Because the temperature of the storage device determines the boiler temperature of the ejector air conditioning system and because the efficiency and capacity of an ejector air conditioning system increases proportionate to an increase in boiler temperature, attempting to capture heat from lower temperature devices (such as refrigeration condensers) may actually make the system use more energy than is gained from those devices. The higher the boiler operating temperature, the more efficient the air conditioning system but the greater the number of lower-temperature devices that cannot be incorporated in the system.
[0011] Some vehicle air conditioning systems may use one or more of three different heat sources - engine cooling water, an oil circulation system, or engine exhaust. The amount of heat available for powering the air conditioning is dependent on waste heat generated by the engine. The cooling system cannot operate independent of the engine operation. [0012] An ejector air conditioning system may use two or more refrigerants (one with a lower saturation temperature and one with a higher saturation temperature) to provide a greater relative difference between the ejector motive force and the evaporator pressure. The source of the boiler heat may be waste heat from the propulsion engine cooling system and/or exhaust system.
[0013] In another system, a thermally-powered ejector air conditioning system may be combined with an engine-driven compressor circuit. The two systems operate in parallel such that the engine-driven compressor circuit provides immediate cooling power when insufficient waste engine heat is available to fully power the ejector circuit. In such systems, no provision is made for operation independent of the engine and, when in operation, the engine driven compressor circuit functions with the same high-side and low-side pressures as the ejector circuit.
[0014] Some air conditioning systems may be optimized for the relatively low temperatures and instability that is typical of ejector systems relying on waste engine heat. A hydrocarbon refrigerant may provide decreased vapor entropy under decreased pressure. Additionally, heat storage is provided for improving the system's transient response and for compensating for fluctuations in the amount of waste engine heat available to the refrigerant boiler.
[0015] Another vehicle air conditioning system uses an ejector circuit to enhance the heat output of a heat-pump HVAC system by selectively increasing the compression ratio of the compressor through the reduction of pressure at the low pressure side of an engine-driven compressor.
[0016] Another system incorporates an ejector in a vehicle air conditioning system using an engine-driven, variable-displacement (not variable-speed) compressor to provide a higher and lower evaporator temperature in two separate but inter-connected evaporator coils.
[0017] Another air conditioning system for on-road vehicles may vary the speed of brushless DC motor-drive air conditioning based on the power capacity of an electric power source. Another system uses two-loop vehicle cooling system incorporating high pressure and low pressure coolant loops. These systems require an electrically-driven compressor for operation with the compressor being the only source of compression for the cooling system. The system may include a fuel-fired boiler in the second loop of a two-loop system as a heater only. The boiler has no means of contributing to the cooling of the vehicle air.
[0018] There has been some investigation into the possibility of using compression boosters to improve the efficiency (COP) of a thermal ejector cooling system in the field of solar power. One system may focus on how to supply air conditioning within the temperature limitations imposed by non-concentrated solar thermal collectors. Another example may achieve the lower evaporator temperatures required by refrigerator and freezer food preservation systems.
[0019] There remains a need for an efficient and effective temperature control system for a vehicle cabin.
SUMMARY
[0020] According to an exemplary embodiment, a vehicle includes a temperature controlled cabin, a fuel storage tank, an engine configured to convert the fuel to propulsion energy, and a system for cooling the cabin. The system includes a boiler in which the fuel is converted to thermal energy to convert a motive refrigerant to a motive pressure and temperature, an ejector configured to mix the motive refrigerant with a working refrigerant, and an evaporator positioned to transfer heat from the cabin to the working refrigerant. The ejector includes a converging- diverging nozzle through which the motive refrigerant enters at the motive pressure and from which the motive refrigerant exits at a lower pressure, a mixing section in which the motive refrigerant is mixed with the working refrigerant which exits the evaporator and enters the ejector at an evaporator pressure, and a diffusion section which further mixes the refrigerants so that the motive refrigerant becomes part of the working refrigerant. The working refrigerant exits the ejector at a pressure lower than the motive pressure but higher than the evaporator pressure. The system also includes a condenser located to transfer heat from the working refrigerant exiting the ejector to an area outside the cabin. The working refrigerant enters the condenser at a condensing pressure. [0021] According to another exemplary embodiment, an air conditioning system for a vehicle has a temperature controlled cabin. The vehicle includes a fuel storage tank, an engine configured to convert fuel to propulsion energy, and a system for cooling the cabin. The system includes a boiler in which the fuel is converted to thermal energy that converts a motive refrigerant from a liquid state to a vapor having a motive pressure and motive temperature and an evaporator positioned to transfer heat from the cabin to a working refrigerant. The working refrigerant exits the evaporator at an evaporator pressure. The system includes an ejector configured to mix the motive refrigerant and the working refrigerant so that the motive refrigerant becomes part of the working refrigerant. The working refrigerant exits the ejector at a pressure which is lower than the motive pressure but higher than the evaporator pressure. The system includes a condenser located to transfer heat from the working refrigerant exiting the ejector to an area outside the cabin. The working refrigerant enters the condenser at a condensing pressure. The system includes a variable speed electrically powered compressor configured to raise the pressure of the working refrigerant in order to improve the efficiency of the ejector.
[0022] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] These and other features, aspects, and advantages of the present invention will become apparent from the following description, appended claims, and the accompanying exemplary embodiments shown in the drawings, which are briefly described below.
[0024] FIG. 1 is an isometric view of a vehicle including a system for cooling the vehicle cabin according to an exemplary embodiment.
[0025] FIG. 2 is a block diagram of a system for cooling the vehicle cabin according to an exemplary embodiment. [0026] FIG. 3 is a block diagram of a system for cooling the vehicle cabin according to another exemplary embodiment.
[0027] FIG. 4 is a block diagram of a system for cooling the vehicle cabin according to another exemplary embodiment.
[0028] FIG. 5 is a block diagram of a system for cooling the vehicle cabin according to another exemplary embodiment.
DETAILED DESCRIPTION
[0029] Hereinafter, various embodiments of the present invention will be described in detail with
[0030] Unlike the exemplary embodiments described herein, conventional systems do not use compression boosters to improve the performance of an ejector system incorporating a fuel-fired boiler. Conventional systems also do not applying compression booster technology to mobile applications. Conventional systems also do not allow the booster compressor to increase its capacity under certain conditions and assume a majoring of the system compression duty.
[0031] According to various exemplary embodiments a combined heating and air conditioning system may be physically small and light enough and have sufficient cooling and heating capacity to make it attractive for use in providing cabin occupant comfort in mobile vehicles. The system may provide heating and cooling which is fully operable without a running propulsion or auxiliary engine. The system may require less electrical storage capacity than currently available engine-off systems. The system may reduce the cost of heating and cooling systems by providing fuel burning and heating components which can function in both modes. The heating and cooling system may operate substantially from heat energy. The heating and cooling system may have the capacity to use waste heat as part of its energy source. The combined heating and cooling system may be powered substantially with energy derived by burning a petroleum-based or non-petroleum-based concentrated fuel source. Some exemplary embodiments of the combined heating and air conditioning system may trade increased component cost and complexity with improved operational efficiency.
[0032] In various exemplary embodiments, the system may be an ejector air conditioning system for mobile vehicles which can be operated as its full cooling capacity when the propulsion engine is not running. The ejector air conditioning system for a mobile vehicle may boost ejector pressure with an electrically driven compressor. The ejector air conditioning system may use a flash boiler. The ejector air conditioning system may share a fuel-fired boiler with a vehicle heating system.
[0033] In various exemplary embodiments, the combined heating and air conditioning system may use a multi-temperature boiler which operates at a higher temperature range for cooling mode and a lower temperature range for heating mode. The combined heating and air conditioning system may allow the heated and refrigerating components to remain outside the temperature-control occupant cabin and transfer the heating and cooling to the cabin with a secondary water-circulating loop. The combined heating and air conditioning system may allow some of the heated and refrigerating components to remain outside the temperature-control occupant cabin and transfer the heating and cooling to the cabin with a functionally-connected but physically separate heat exchanger located within the occupied compartment. The vehicle cabin air conditioning and heating may use an off-vehicle electrical power source such as a grid- connected circuit in a parking area. The air conditioning and heating system for a vehicle may optimize energy input from multiple sources.
[0034] Referring to FIG. 1, a vehicle 100 may include an HVAC system 102 configured to provide climate control of a vehicle cabin 104, according to various exemplary embodiments. In situations where the primary engine or generator is not operating, the vehicle 100, a building, or a structure may rely on stored power from a variety of sources to provide heating and/or cooling for the occupied space (e.g., battery system, fuel system (chemical energy), phase-change material system, or various other systems). The HVAC system 102 may be an HVAC system installable in the vehicle 100 and having a heater 106 which provides thermal energy by, for example, burning a fuel. The HVAC system 102 may also include an electrical power source 110 to provide electrical power for use by various components of the HVAC system.
[0035] The HVAC system 102 may be controlled in a way that makes optimized use of energy from the engine 108, the heater 106, and/or the electrical power source 110 to condition the air for the occupied space of the cabin 104. For example, the system 102 may only use energy from the engine 108 when it is running and may use energy from the thermal energy source 106 and/or the electrical power source 110 when the engine 108 is not running.
[0036] Referring also to FIG. 2, according to an exemplary embodiment, the system 102 is a predominately heat-powered device which heats and cools the air of the vehicle cabin 104 to maintain a desired temperature for the comfort of its occupants. The system 102 may be an ejector type vapor compression environmental control system for a mobile vehicle which is capable of heating and cooling operation independent of the operation of the propulsion engine 108.
[0037] The system 102 includes a boiler 202 which in various modes may be used as the primary heat source to boil refrigerant for a primary cooling loop or circuit 204 (e.g., a liquid hydronic loop) when cabin cooling is desired or to heat the loop 204 when cabin heating is required. The boiler 202 may boil the refrigerant in the cooling loop 204 based on heat from a heat transfer fluid in a heat transfer loop 206. The heat transfer fluid may extract heat from a thermal energy source 208 (e.g., an engine cooling circuit of the engine 108, exhaust from the engine 108, the heater 106, etc.) and be forced through the boiler 202 via a pump 210. This heat may be used to boil the refrigerant in the loop 204 or to power an electric generator for firing the boiler 202.
[0038] Alternatively, the fuel source for the boiler 202 may be the same as that of the vehicle's propulsion engine 108 (such as diesel fuel) or may be of a different type and carried specifically for the purpose of powering this system (for example, propane). The most common fuel for the boiler 202 to use would be the type which is predominant on the vehicle. However, in some cases, it will be preferable to carry fuel specifically for use by the boiler 202. The boiler 202 may be fueled by a wide variety of petroleum and non-petroleum based fuels including but not limited to diesel, propane, biodiesel, hydrogen, gasoline, kerosene, aviation fuels, nuclear, solar thermal, electrical resistance, and friction.
[0039] It may be desirable that the boiler 202 have a widely adjustable heat output. However, under many conditions, lower-cost non-variable boilers can be used. Liquid fueled burners may be of a high-pressure atomization, droplet diffusion or vaporization type. The heat exchanger, fluid containment, and thermal control system of the boiler 202 may be designed for flash or flooded operation or a combination of the two. Flooded type boilers are larger but require less exact capacity control than flash type boilers. In other embodiments, the boiler 202 may operate at different temperatures for the heating and the cooling modes. In these embodiments the boiler 202 may function as a lower-temperature flooded boiler when the system is operated in heating mode and as a higher-temperature flash boiler when the invention is operated in cooling mode. Therefore, the capacity and efficiency of the cooling mode can be maximized and the system pressure and temperature may be reduced when in heating mode.
[0040] The primary cooling loop 204 includes an evaporator 212 for transferring heat from the cabin 104 and an exterior condenser 214 for transferring heat to an area outside the cabin 104. The refrigerant is pumped to the boiler 202 and the evaporator 212 and from the condenser 214 by a pump 216.
[0041] The evaporator/condensor 212 may be of various types. In a single loop embodiment, the heat from the refrigerant is transferred directly to the air in the cabin compartment to be cooled or heated. In this embodiment a heat exchanger may be optimized for efficient exchange between mixed phase fluid and air (non- flooded) or liquid-air (flooded) mode. A flooded evaporator/condenser 212 is typically more efficient but also requires a greater refrigerant charge volume. In an embodiment incorporating an oil-lubricated mechanical compressor is used in the cooling (evaporator) mode, special attention may be paid to ensure that oil is returned to the compressor and not retained in the evaporator. In a two loop embodiment, the heat from the refrigerant is transferred to a secondary liquid loop. Therefore, the evaporator 212 design is optimized to transfer heat into and out of a liquid rather than air. Suitable evaporator/condenser 212 technologies may include, but are not limited to, oven-brazed microchannel, copper tube with pressed or integrally formed fins, skived fin, heat pipe, thermopipe, thermosyphon, pumped liquid, vapor chamber, tube-in-tube, tube-in-shell, flat plate, and metal foam.
[0042] The performance of the exterior condenser 214 at least partially determines the capacity and efficiency of the system 102. The exterior condenser 214 may dissipate about two to five times the heat that would be dissipated in a typical purely compressor-driven air conditioning system. Therefore, when choosing the materials, technology, and design of the condenser 214, factors such as performance relating to size, cost, weight, and longevity should considered. How these factors are weighed may vary between different applications of the system 102. Compatible exterior condenser technologies include, but are not limited to, oven-brazed microchannel, copper tube with pressed or integrally formed fins, skived fin, heat pipe, thermopipe, thermosyphon, pumped liquid, vapor chamber and metal foam. The fans used to force are across the external condenser 214 are typically tube-axial in design, but may also be axial, forward, or backward impeller or mixed flow fans. The driving motors are typically variable-speed permanent magnet brushless DC motors, but may also be induction AC, brush DC, universal, or reluctance motors.
[0043] The pump 216 (e.g., a liquid feed pump) should be capable of efficiently and reliably forcing the liquid condensate at the lower pressure of the condenser to the higher pressure of the boiler without inducing cavitation. The pump 216 may be a positive displacement type such as piston, rotary, or diaphragm although other types may be used as long as the liquid may be efficiently and reliably pumped without cavitation. The pump 216 may be hermetically sealed with a drive motors or may be magnetically coupled to reduce the potential for leaks. The pump 216 drive motor may be a variable-speed permanent magnet brushless DC motor, but may also be an induction AC, brush DC, universal, or reluctance motor.
[0044] The loop 204 also includes an ejector 218 (e.g., jet ejector, eductor, thermocompressor, Venturi ejector, etc.) configured to mix the motive refrigerant from the boiler 202 with the working refrigerant from the evaporator 212. The ejector 218 may include a converging- diverging nozzle through which the motive refrigerant enters at a motive pressure and from which the motive refrigerant exits at a lower pressure. The ejector 218 may also include a mixing section in which the motive refrigerant is mixed with the working refrigerant, which exits the evaporator 212 and enters the ejector 218 at an evaporator pressure. The ejector 218 may also include a diffusion section which further mixes the refrigerants so that the motive refrigerant becomes part of the working refrigerant. The working refrigerant exits the ejector 218 at a pressure lower than the motive pressure but higher than the evaporator pressure. While the ejector 218 may use refrigerant vapor as the motive fluid, in other exemplary embodiments, the ejector 218 may use pressurized liquid and provide higher compression ratios. The ejector 218 may be a fixed flow ejector or may be an adjustable or variable capacity ejector to aid in achieving efficient flow control.
[0045] The loop 204 may also include an electrically or mechanically-powered compressor 220 to improve the overall cooling efficiency of the system 102 (i.e. COP) and to increase cooling capacity. The compressor 220 may be located between the outlet of the evaporator 212 and the suction inlet of the ejector 218 to reduce the compression ratio between the suction and discharge of the ejector 218 by elevating the pressure of the gas entering the ejector 218 from the evaporator 212.
[0046] Use of the electric booster compressor 220 may increase the total energy coefficient of performance (COP) and cooling capacity of the system 102, but also increase the amount of electricity the system 102 consumes. In various applications this tradeoff may be advantageous. It is desirable for the booster compressor 220 to be of a type that has low friction losses and is suitable for efficient pumping of gas at compression ratios below 4: 1. The compressor 220 may be variable in capacity by adjustment of either speed or displacement. Suitable electric booster compressor technologies may include, but are not limited to, rolling piston, scroll, rotary vane, turbine, boundary layer turbine, reciprocating piston, diaphragm, and sonic compressors. The compressor 220 may be hermetically sealed to prevent leakage and may be directly driven or magnetically coupled to permanent magnet brushless DC, reluctance, or induction motors. [0047] Under certain conditions, and if desirable, the capacity of this compressor 220 may be increased (by increasing speed or displacement) so that, in the absence of sufficient heat from the boiler 208, the compressor 220 provides most or all of the compression energy to power the system 102. However, in most cases, the capacity of the compressor 220 will be dynamically adjusted by a controller 222 relative to the demands on the system and the energy available from other sources so that the best and most energy-efficient operation is obtained.
[0048] The controller 222 may be configured to control selection of the electrical power source 110 and the thermal energy source 208 as described in greater detail below. The controller 222 may also be configured to control the speed at which the pumps 210, 216 operate. The controller 222 may be any software or hardware (e.g., digital and/or analog) controller configured to control the compressor 220 and selection of the electrical power source 110 and the thermal energy source 208. According to other exemplary embodiments, the controller for selection of the electrical power source 110 and the thermal energy source 208 may be a separate controller from the controller 222.
[0049] The system 102 may also include a metering device 224 located at the inlet of the evaporator 212. The metering device 224 is configured to control the amount of refrigerant that enters the evaporator 212 from the condenser 214. Any amount of refrigerant that does not enter the evaporator 212 flows back to the pump 216. The amount of refrigerant flow through the metering device 224 may be controlled by the controller 222.
[0050] Referring to FIG. 3, according to another exemplary embodiment, the compressor 220 may be located between the discharge of the ejector 218 and the inlet of the condenser 214. When so located, the compressor 220 may reduce the compression ratio of the ejector 218 by reducing the discharge pressure of the ejector 218 relative to the suction pressure. This location may also increase the efficiency of the ejector system and provide the additional benefit of increasing the operating temperature of the condenser 214, thereby reducing the condenser size, weight and cost. The choice of where the booster compressor is placed in the system may be used in selecting the best component. For example, if the booster is placed between the evaporator 212 outlet and the suction inlet of the ejector 218, a booster compressor 220 of less volumetric flow may be required than if the compressor 220 is placed between the ejector discharge 218 and the exterior condenser 214.
[0051] Referring to FIG. 4, the thermal energy sources 208 and the electrical power sources 110 of the system 102 are illustrated in greater detail, according to one exemplary embodiment. In the illustrated exemplary embodiment, the thermal energy source 208 may include a heat exchanger 302 of the engine 108 configured to extract heat from ambient heat from the engine 108, heat from an engine 108 cooling system, heat from an exhaust system of the engine 108, heat from an auxiliary engine, cooling system, or exhaust system, etc. The thermal energy source 208 may also include a heat exchanger 304 configured to extract heat from the auxiliary fuel- fired heater 106.
[0052] The electrical power source 110 may include an alternator 306 of the engine 308, a battery 310, and an AC shore power grid connection 312 coupled to an AC-DC rectifier 314. The battery 310 may be a lead-acid battery, a lithium-ion battery, a nickel- metal hydride battery, or any other battery or bank of batteries capable of powering the compressor 312.
[0053] The controller 222 may be configured to control selection of the electrical power source 110 and the thermal energy source 208. If the engine 108 is running, the controller 222 may switch the heater 106 off or may actuate valves in the loop 206 such that the boiler 202 receives heat via the heat transfer fluid from the heat exchanger 304 of the engine 108. Likewise, the controller 222 may direct electrical power to the compressor 220 (and the pumps 210, 216) from the alternator 306 of the en 1 gBi 1 ne 108.
[0054] If the engine 108 is not running, the controller 222 may direct electrical power to the compressor 220 (and the pumps 210, 216) from the shore power grid connection 312, if available. If shore power is not available, the controller 322 may direct electrical power to the compressor 220 from the battery 310. The controller 322 may actuate the heater 106 or valves in the loop 206 such that the boiler 202 receives heat via the heat transfer fluid from the heat exchanger 304 of the heater 106. As described above, the heater 106 may be powered by engine fuel or another fuel. Alternatively, the heater 106 may be an electric heater or resistance element that is electrically powered by the shore power connection 312 or by the battery 310.
[0055] Referring to FIG. 5, according to another exemplary embodiment similar to FIG. 4, the compressor 220 may be located between the discharge of the ejector 218 and the inlet of the condenser 214. When so located, the compressor 220 may reduce the compression ratio of the ejector 218 by reducing the difference between the discharge pressure and the suction pressure of the ejector 218. This location may also increase the efficiency of the ejector system and provide the additional benefit of increasing the operating temperature of the condenser 214, thereby reducing the condenser size, weight and cost. The choice of where the booster compressor is placed in the system may be used in selecting the most suitable compressor for the system. For example, if the booster is placed between the evaporator 212 outlet and the suction inlet of the ejector 218, a boost compressor 220 of less volumetric flow may be required than if the compressor 220 is placed between the ejector discharge 218 and the exterior condenser 214.
[0056] According to some exemplary embodiments, the system 102 may or may not include a liquid phase subcooling heat exchanger between the condenser and the motive fluid inlet to the ejector. The addition of such a heat exchanger may improve efficiency but increase cost and size.
[0057] In various exemplary embodiments, the system may use one or two heat transfer loops. In one exemplary embodiment similar to that shown in the figures and described above, a refrigerant is boiled in a single heat transfer loop which includes the boiler, ejector, exterior condenser, subcooler (optional), electric compressor (optional), waste heat recovery heat exchanger (optional), cabin-air heat exchanger, ejector/exterior condenser by-pass valves, and liquid refrigerant pump. In this single loop embodiment, in a cooling mode, refrigerant vapor from the boiler may be directed through the ejector and exterior condenser. In a heating mode, the refrigerant vapor bypasses the ejector and exterior condenser so that the refrigerant enters cab-air heat exchanger directly where it condenses thereby giving up latent and sensible heat to the cabin air. This exemplary embodiment provides a simple approach that may provide excellent efficiency due to direct heat transfer with the cabin air.
[0058] In another embodiment, a two loop system may be used. The primary loop is similar to that of the single loop embodiment described above except that the cabin-air heat exchanger is replaced with a liquid-liquid heat exchanger which transfers heat with the fluid (typically a water/glycol antifreeze solution) in the secondary heat exchanger. In cooling mode, the secondary heat exchanger may be operated at a temperature between about 35F and 6OF. In heating mode the secondary loop may be operated at a temperature between about 9OF and 180F. Having been increased or decreased to the desired temperature, the fluid of the secondary loop passes through a liquid-air heat exchanger which is positioned to add or remove heat from the cabin 104 air. The advantage of the two loop system is that the refrigerant loop, including the pressurized boiler 202, may be more easily located remote from the cabin air. This is particularly desirable when more dangerous and/or high pressure refrigerants are used or when it is desirous to maximize the cooling COP by operating the system at very high temperatures.
[0059] In other embodiments, additional heat transfer loops may be included which add heat to or extract heat from the primary loop. Such additional loops may be used, for example, to transport waste heat from an engine or solar heat from vehicle-mounted solar collectors into the primary loop. Similarly, in some vehicles it may be desired to have other heating/cooling loops directed to different compartments or sections of the vehicle. Such additional loops may or may not operate at the same temperature as other loops.
[0060] It is important to note that the construction and arrangement of the system as shown in the various exemplary embodiments is illustrative only. Although only a few embodiments of the present application 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 (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the application. For example, elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present application. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Any means-plus-function clause is intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present application.
[0061] The foregoing description of embodiments of the application has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the application to the precise form disclosed, and modifications and variations are possible in light of the above teachings, or may be acquired from practice of the application. The embodiments were chosen and described in order to explain the principles of the application and its practical application to enable one skilled in the art to utilize the application in various embodiments and with various modifications as are suited to the particular use contemplated.
[0062] Although the description contains many specificities, these specificities are utilized to illustrate some of the preferred embodiments of this application and should not be construed as limiting the scope of the application. The scope of this application fully encompasses other embodiments which may become apparent to those skilled in the art. All structural, chemical, and functional equivalents to the elements of the above-described application that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present application. A reference to an element in the singular is not intended to mean one and only one, unless explicitly so stated, but rather it should be construed to mean at least one. Furthermore, no element, component or method step in the present disclosure is intended to be dedicated to the public.