Patent Publication Number: US-11035595-B2

Title: Recuperated superheat return trans-critical vapor compression system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a non-provisional application of U.S. provisional application 62/547,501 filed Aug. 18, 2017. The entire contents of the above-identified application is hereby incorporated by reference. 
     TECHNICAL FIELD 
     This disclosure relates to cooling systems. 
     BACKGROUND 
     From a controls perspective, a Low Pressure Receiver (LPR) architecture for a cooling system is relatively simple. A gravity-fed evaporator included in a typical LPR architecture has a dependency on gravity to provide consistent coolant flow. 
     One or more primary system evaporators in the LPR architecture may exhaust into a low pressure receiver (a type of vapor-liquid separator) before flow continues on to a compressor. As a result, the low pressure receiver may need to be large enough to remove saturated liquid in the flow to the compressor. Otherwise, liquid remaining in the flow to the compressor may cause serious problems in the compressor. For example, liquid that settles in the oil of the compressor may boil, which may then cause oil to foam and enter a compression chamber of the compressor. Including an over-sized low pressure receiver may help eliminate saturated liquid in the flow to the compressor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments may be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale. Moreover, in the figures, like-referenced numerals designate corresponding parts throughout the different views. 
         FIG. 1  is a schematic diagram of an example of a cooling system that has a recuperated superheat return (RSR) architecture; 
         FIG. 2  is a pressure-enthalpy diagram that illustrates an example of the progression of the pressure and the enthalpy of coolant as the coolant flows through the cooling system; 
         FIG. 3  illustrates a cross-sectional view of an example of the evaporator that cools two independent coolant loops; 
         FIG. 4  is a schematic diagram of an example of an integrated power and thermal management system that includes the cooling system; 
         FIG. 5  illustrates an example where the pressure drop element and the mixer are integral components of an eductor, an ejector, or a venture valve; and 
         FIG. 6  illustrates an example of a directed-energy weapon included in the customer platform component  418 . 
     
    
    
     DETAILED DESCRIPTION 
     Methods and systems for recuperated superheat return are provided. For example, in one such system, the system includes a compressor, a gas cooler, a recuperator, a thermal expansion valve, an evaporator, a vapor-liquid separator, a liquid return valve, a pressure drop element, and a mixer. The compressor may compress a coolant that is supplied to the compressor in a vapor state. The gas cooler may cool the coolant compressed by the compressor. The recuperator may have a high pressure side and a low pressure side that are fluidly isolated from each other. Thermal energy may be transferred from the high pressure side of the recuperator to the low pressure side, thereby cooling coolant in the high pressure side and heating coolant in the low pressure side. The recuperator may receive the coolant cooled by the gas cooler at an inlet of the high pressure side. The coolant in the high pressure side is cooled in the recuperator when the thermal energy is transferred to the low pressure side. Correspondingly, the coolant in the low pressure side is heated to a vapor state. The coolant in the vapor state may be supplied to the compressor from an outlet of the low pressure side. The thermal expansion valve may receive the coolant cooled by the recuperator from an outlet of the high pressure side of the recuperator. The evaporator may receive the coolant from the thermal expansion valve and cool a thermal load with the coolant. The vapor-liquid separator may receive the coolant from the evaporator and separate the coolant into a vapor portion and a liquid portion. The liquid return valve may control a flow of the liquid portion out of the vapor-liquid separator. The pressure drop element may cause the pressure of the vapor portion of the coolant that exits the vapor-liquid separator to drop to a decreased pressure. The mixer may form a mixture of the vapor portion of the coolant at the decreased pressure and the liquid portion of the coolant received through the liquid return valve. The recuperator may receive the mixture at an inlet of the low pressure side of the recuperator. 
     In some examples, an interesting feature of the systems and methods described below may be that liquid coolant entering the compressor may be avoided. Alternatively, or in addition, an interesting feature of the systems and methods described below may be that a smaller and/or a less efficient vapor-liquid separator may be utilized than in some other systems. Alternatively, or in addition, an interesting feature of the systems and methods described below may be mass may be returned to the system more rapidly than in some other systems so as to more rapidly adjust to sudden onset of high thermal loads. Alternatively, or in addition, an interesting feature of the systems and methods described below may be to improve a Coefficient of Performance at high heat rejection temperature and/or pressure. 
       FIG. 1  is a schematic diagram of an example of a cooling system  100  that has a recuperated superheat return architecture. The cooling system  100  shown in  FIG. 1  includes a compressor  102 , a gas cooler  104 , a recuperator  106 , a thermal expansion valve  108 , an evaporator  110 , a vapor-liquid separator  112  (for example, a low pressure receiver), a liquid return valve  114 , a pressure drop device  116 , and a mixer  118 . The system  100  may include additional, fewer, and/or different components than the example shown in  FIG. 1 . 
     The pressure drop device  116  may include a means for creating a pressure drop. The pressure drop device  116  may create the pressure drop between an inlet of the pressure drop device  116  and an outlet of the pressure drop device  116 . Examples of the pressure drop device  116  may include a restriction, a length of pipe or tubing, a pipe or a tubing having a cross-sectional area change, a pipe or a tubing including an obstruction, an orifice, a valve, a bent pipe, an automated valve, a venturi valve, and/or any other physical structure that causes a pressure drop on a fluid as the fluid flows through the physical structure. The pressure drop device  116  may be a passive device and/or an active device. 
     The vapor-liquid separator  112  may include any device configured to separate a vapor-liquid mixture into vapor and liquid portions. The vapor-liquid separator  112  may be a vessel in which gravity causes the liquid portion to settle to a bottom portion of the vessel and the vapor portion to rise to a top portion of the vessel. Alternatively, the vapor-liquid separator  112  may use centrifugal force to drive the liquid portion towards an outer edge of the vessel for removal and the vapor portion may migrate towards a center region of the vessel. In some examples, the vapor-liquid separator  112  may include a level sensor mechanism that monitors a level of the liquid in the vessel. Examples of the vapor-liquid separator may include a low pressure receiver and a flash tank. 
     The compressor  102  may be any mechanical device that increases a pressure of a gas by reducing the volume of the gas. Examples of the compressor  102  may include any gas compressor, such as a positive displacement compressor, a dynamic compressor, a rotary compressor, a reciprocating compressor, a centrifugal compressor, an axial compressor, and/or any combination thereof. 
     The mixer  118  may be any device that combines fluid received in two or more inlets into fluid that exits an outlet. An example of the mixer  118  includes a junction. 
     The compressor  102 , the gas cooler  104 , the recuperator  106 , the thermal expansion valve  108 , the evaporator  110 , the vapor-liquid separator  112 , the liquid return valve  114 , the pressure drop device  116 , and the mixer  118  may be in fluid communication with each other and form a coolant circuit through which a coolant may flow. Tubing may connect the components of the coolant circuit. A high pressure side of the coolant circuit may be a portion that extends from an outlet of the compressor  102  to an inlet of the thermal expansion valve  108 . A low pressure side of the coolant circuit may be a portion that extends from an outlet of the thermal expansion valve  108  to an inlet of the compressor  102 . In some examples, a first portion  120  of the coolant circuit may include the compressor  102 , the gas cooler  104 , and the recuperator  106 . A second portion  122  of the coolant circuit may include the thermal expansion valve  108 , the evaporator  110 , the vapor-liquid separator  112 , the liquid return valve  114 , the pressure drop device  116 , and the mixer  118 . 
     The coolant may be any substance suitable for cooling systems. The coolant or refrigerant may be any substance suitable for a trans-critical cooling system and/or a sub-critical cooling system. Examples of the coolant may include carbon dioxide (CO 2 ), anhydrous ammonia, a halomethane, a haloalkane, a hydrofluorocarbon (HFC), chlorofluorocarbons (CFC), a hydrochlorofluorocarbon (HCFC), any two-phase refrigerants, and/or a nanofluid. 
     During operation of the system  100 , the compressor  102  may compress the coolant, which is supplied to the compressor in a vapor state. The coolant compressed by the compressor  102  may flow to the gas cooler  104 . In some examples, the compressed coolant may flow through an oil separator  124  to the gas cooler  104 . The oil separator  124  may separate oil from the compressed coolant and return the oil to the compressor  102 . The gas cooler  104  may cool the coolant compressed by the compressor  102 . The coolant cooled by the gas cooler  104  may flow to the recuperator  106 . 
     The recuperator  106  may have a high pressure side and a low pressure side. The recuperator  106  may include a heat exchanger that transfers heat from the coolant on the high pressure side to the coolant on the low pressure side. The recuperator  106  may receive the coolant cooled by the gas cooler  104  at an inlet  126  of the high pressure side and supply the coolant to the second portion  122  of the coolant circuit from an outlet  128  of the high pressure side. The recuperator  106  may receive the coolant returned by the second portion  122  of coolant circuit at an inlet  130  of the low pressure side of the recuperator  106 . The recuperator  106  may supply the coolant to the compressor  102  from an outlet  132  of the low pressure side of the recuperator  106 . 
     By transferring thermal energy from the high pressure side to the low pressure side, the recuperator  106  may cause the coolant to exit the outlet  132  of the low pressure side in a vapor state. Due to thermal energy transferred to the coolant before the coolant flows out of the outlet  132  of the low pressure side to the compressor, the compressor  102  receives the coolant from the recuperator  106  in the vapor state and, in some examples, superheated. 
     With respect to the second portion  122  of the coolant circuit, the coolant may flow from the outlet  128  of the high pressure side of the recuperator  106  to the thermal expansion valve  108 . The coolant exits the thermal expansion valve  108  and flows to the evaporator  110 . The evaporator  110  may cool a thermal load  134 . The thermal expansion valve  108  may regulate a high pressure and/or mass flow in the system  100  to control Coefficients of Performance (COP) and/or evaporator heat duty. For example, the thermal expansion valve  108  may control high side pressure to achieve a target heat rejection and CoP may be dictated by other factors such as an ambient temperature. The system  100  may include one or more processors  140  configured to cause the thermal expansion valve  108  to regulate the high pressure side, regulate compressor speed, regulate liquid return, regulate oil return from the oil separator and regulate condenser fan(s) speed. 
     As a result of the recuperator  106  transferring thermal energy from the high pressure side to the low pressure side, the coolant that exits the gas cooler  104  may be cooled or sub-cooled prior to entering the thermal expansion valve  108 . This cooling results in lowering the vapor quality in the flow to the evaporator  110 . The lower vapor quality in the coolant entering the evaporator  110  may make for better liquid distribution and improved evaporator performance than without the lower vapor quality. In addition, the evaporator  110  may be physically smaller than an evaporator that receives the coolant without the lowered vapor quality and yet still have the same cooling capacity as the larger evaporator. 
     The coolant that exits the evaporator  110  flows into an inlet of the vapor-liquid separator  112 . The coolant separates into a liquid and a vapor in the vapor-liquid separator  112 . 
     The vapor-liquid separator  112  includes a liquid outlet  136  and a vapor outlet  138 . An inlet of the pressure drop device  116  receives a first portion of the coolant through the vapor outlet  138  of the vapor-liquid separator  112 . An inlet of the liquid return valve  114  receives a second portion of the coolant through the liquid outlet  136  of the vapor-liquid separator  112 . 
     The first portion of the coolant exits an outlet of the pressure drop device  116  at a lower pressure than at the inlet of the pressure drop device. The second portion of the coolant exits an outlet of the liquid return valve  114 . The mixer  118  mixes the first portion of the coolant with the second portion of the coolant to form a mixture. An outlet of the mixer  118  may supply the mixture of the first portion of the coolant and the second portion of the coolant to the inlet  130  of the low pressure side of the recuperator  106 . The pressure drop created by the pressure drop device  116  may aid in causing the coolant to flow to the recuperator  106  without relying on gravity to cause the flow. 
     In some examples, the pressure drop device  116  and the mixer  118  may be one device. For example, the pressure drop device  116  may be an eductor, an ejector, and/or a venturi valve that receives the first portion of the coolant through the vapor outlet  138  of the vapor-liquid separator  112  and the second portion of the coolant through the outlet of the liquid return valve  114 . An outlet of the eductor, the ejector, and/or the venturi valve may supply the mixture of the first portion of the coolant and the second portion of the coolant to the recuperator  106 . 
     Accordingly, the second portion  122  of the coolant circuit is configured to return to the inlet  130  of the low pressure side of the recuperator  106  the mixture of the first portion of the coolant released at the outlet of the pressure drop device  116  and the second portion of the coolant supplied by the liquid outlet  136  of the vapor-liquid separator  112 . 
     Due to the thermal energy transferred to the low pressure side of the recuperator  106 , the coolant entering the inlet  130  of the low pressure side of the recuperator  106  may include liquid. The coolant entering the inlet  130  of the low pressure side may include as much as, for example, twenty percent liquid by mass, and the coolant entering the compressor  102  may be, nevertheless, in a vapor state due to the heat transferred to the coolant by the recuperator  106 . Accordingly, the physical size of the vapor-liquid separator  112  may be smaller than if the system  100  did not transfer the heat to the coolant with the recuperator  106 . 
     The processor  140  may be configured to cause the liquid return valve  114  to adjust the flow of the second portion of the coolant based on a temperature of the coolant supplied to the compressor  102 . For example, the liquid return valve  114  may adjust the flow of the second portion of the coolant such that a temperature of the coolant supplied to the compressor  102  indicates that the coolant is supplied to the compressor in the vapor state, and in some examples, superheated. As another example, the liquid return valve  114  may adjust the flow of the second portion of the coolant such that a temperature of the coolant supplied to the compressor  102  remains below a threshold value. If the temperature of the coolant supplied to the compressor  102  were above the threshold value selected, then the overheated coolant may damage the compressor  102  or a subcomponent thereof. 
     In one example, the liquid return valve  114  may be adjusted to increase the flow of the second portion of the coolant in response to a temperature of the coolant supplied to the compressor  102  exceeding an upper value in a predetermined temperature range. Conversely, the liquid return valve  114  may be adjusted to decrease the flow of the second portion of the coolant in response to a temperature of the coolant supplied to the compressor  102  falling below a lower value in the predetermined temperature range. In other words, the processor may attempt to keep the temperature of the coolant supplied to the compressor  102  within the predetermined temperature range by causing the liquid return valve  114  to adjust the flow of the second portion of the coolant supplied by the liquid outlet  136  of the vapor-liquid separator  112 . 
     Alternatively or in addition, the processor  140  may be configured to cause the liquid return valve  114  to adjust the flow of the second portion of the coolant based on an operation state of the system  100 . The system  100  may operate, for example, in a low heat duty state or a high heat duty state. In the low heat duty state, the thermal load  134  may be relatively low compared to the high heat duty state. In contrast, in the high heat duty state, the thermal load  134  may be relatively high compared to the low heat duty state. During the low heat duty state, the compressor  102  may be operated at a speed lower than the speed during the high heat duty state. 
     During steady-state operation of the system  100 , less liquid may be returned through the liquid return valve  114  than when transitioning from the low heat duty state to the high duty state. Steady-state operation applies to the low heat duty state and the high heat duty state. 
     In some examples, during steady-state operation, the system  100  may monitor a compressor discharge temperature (in other words, the temperature of the coolant at an outlet of the compressor  102 ) and adjust the flow of the liquid returned through the liquid return valve  114  so that the compressor discharge temperature remains at or above a lower threshold temperature and below an upper threshold temperature. The lower threshold temperature may be, for example, a temperature at which the coolant is superheated. The upper threshold temperature may be, for example, a maximum compressor discharge temperature specified by a manufacturer of the compressor  102 . Accordingly, the system  100  may, for example, superheat the coolant entering the compressor  102  as much as possible without the coolant exiting the compressor  102  exceeding the maximum compressor discharge temperature. 
     In some examples, adjusting the flow of the second portion of the coolant from the liquid return valve  114  may not involve modifying a size of an opening in the liquid return valve  114  or otherwise actively changing any geometry of the system  100 . Instead, the flow adjustment may result from inherent characteristics of the components of the system  100 . For example, if the thermal load applied to the system  100  at the evaporator  110  were to decrease for any reason, then the vapor flow through the vapor outlet  138  of the vapor-liquid separator  112  may correspondingly decrease. As a result of the vapor flow through the vapor outlet  138  decreasing, the pressure drop created by the pressure drop device  116  may decrease. Due to the decrease in the pressure drop created by the pressure drop device  116 , the flow of the second portion of the coolant from the liquid return valve  114  may decrease. 
       FIG. 2  is a pressure-enthalpy diagram  200  that illustrates an example of the progression of the pressure and the enthalpy of the coolant as the coolant flows through the cooling system  100 . The diagram  200  includes a liquid line  202  and a vapor line  204  for the coolant used in the cooling system  100 . 
     In the example illustrated in  FIG. 2 , the coolant entering the compressor  102  may start as sub-critical superheated vapor. As the coolant is compressed ( 206 ) by the compressor  102 , the pressure and enthalpy of the coolant increase. As the coolant is cooled ( 208 ) by the gas cooler  104 , the enthalpy of the coolant decreases. As the coolant is cooled ( 210 ) in the high pressure side of the recuperator  106 , the enthalpy of the coolant decreases even further. The pressure of the coolant drops below the liquid line  202  and/or the vapor line  204  when expanded ( 212 ) at the thermal expansion valve  108 . When the evaporator  110  cools the thermal load  134 , the coolant is correspondingly heated ( 214 ) in the evaporator  110  by the thermal load  134 . The enthalpy of the coolant increases as the coolant is heated ( 214 ) in the evaporator  110 . The coolant in the vapor-liquid separator  112  will be sub-critical and therefore separate into a liquid portion and a vapor portion. Similarly, the mixture of the first portion of the coolant supplied by the vapor outlet  138  and the second portion of the coolant supplied by the liquid outlet  136  will be subcritical as the mixture enters the inlet  130  of the low pressure side of the recuperator  106 . The coolant in the low pressure side is then heated ( 216 ) by the recuperator  106  into the superheated region. 
     The processor  140  may be any device that performs logic operations. The processor  140  may be in communication with a memory (not shown). Alternatively or in addition, the processor  140  may be in communication with other components, such as the compressor  102 , the liquid return valve  114 , and/or the thermal expansion valve  108 . The processor  140  may include a controller, a general processor, a central processing unit, a server device, an application specific integrated circuit (ASIC), a digital signal processor, a field programmable gate array (FPGA), a digital circuit, an analog circuit, a microcontroller, any other type of processor, or any combination thereof. The processor  140  may include one or more elements operable to execute computer executable instructions or computer code embodied in the memory. 
     The memory may be any device for storing and retrieving data or any combination thereof. The memory may include non-volatile and/or volatile memory, such as a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), or flash memory. Alternatively or in addition, the memory may include an optical, magnetic (hard-drive) or any other form of data storage device. 
     The cooling system  100  may include additional, fewer, or different components than shown in  FIG. 1 . For example, although the evaporator  110  illustrated in  FIG. 1  appears as a single evaporator, the evaporator  110  may include multiple evaporators. Alternatively or in addition, the system  100  may include one or more evaporators connected in series and/or in parallel with the evaporator  110 . In some examples, the cooling system  100  may include one or more pumps for the coolant. Alternatively or in addition, the system  100  may not include the oil separator  124 . 
     The compressor  102  may include a variable flow device. Varying the speed of the compressor  102  may regulate mass flow rate of the coolant in the system  100 . Varying the mass flow rate of the coolant may have a substantial and direct effect on the thermal expansion valve  108 . The processor  140  may control the variable flow device. 
     In the example shown in  FIG. 1 , the evaporator  110  cools the thermal load  134 . In alternative examples, such as the example shown in  FIG. 3  the evaporator  110  cools multiple thermal loads. 
       FIG. 3  illustrates a cross-sectional view of an example of the evaporator  110  that cools two independent coolant loops, namely a hotel coolant loop  302  and a primary coolant loop  304 . The hotel coolant loop  302  may cool a device that generates less heat than a device cooled by the primary coolant loop  304 . 
     The evaporator  110  may include conduits  306  that transport a coolant  308 , which enters the evaporator  110  through an inlet  310  of the evaporator  110 , through to an outlet (not shown) of the evaporator  110 . The coolant  308  may be in a liquid state at the inlet  310  of the evaporator  110 . Accordingly, the coolant  308  may divide evenly among the conduits  306  using a simple manifold  312  that has an opening for each of the conduits  306 . The manifold  312  may operate independently of gravitational forces because the coolant  308  is in the liquid state at the inlet  310  and under pressure. 
     The single set of the conduits  306  cool both of the independent cooling loops  302  and  304 . The evaporator  110  includes a first section  314  and a second section  316 . The single set of the conduits  306  extend through the first section  314  and the second section  316 . The first section  314  is isolated and/or insulated from the second section  316 . Coolant in the hotel coolant loop  302  may flow around the conduits  306  in the first section  314 , transferring heat from the coolant in the hotel coolant loop  302  to the coolant in the conduits  306 . Coolant in the primary coolant loop  304  may flow around the conduits  306  in the second section  316 , transferring heat from the coolant in the primary coolant loop  304  to the coolant in the conduits  306 . Accordingly, as the coolant flows through the conduits  306 , the temperature of the coolant in each of the conduits  306  increases from section to section. Correspondingly, the percentage of vapor in each of the conduits  306  may rise from section to section. 
     Despite the potential presence of vapor in the coolant in the conduits  306  as the coolant enters the second section  316 , the coolant does not need to be distributed among conduits  306  because the coolant in the conduits  306  remain isolated from each other. In contrast, if two discrete evaporators were used instead of the single evaporator  110  shown in  FIG. 3 , then the coolant entering the second evaporator would need to be distributed among a second set of conduits in the second evaporator. A more complex mechanism for evenly distributing the coolant among the second set of conduits in the second evaporator would be needed because of the potential presence of vapor in the coolant entering the second evaporator. 
     In other examples, the evaporator  110  may cool more than two independent cooling loops. The evaporator  110  may include a section for each of the independent cooling loops and the conduits  306  may extend through all of the sections. 
     The conduits  306  and the evaporator  110  shown in  FIG. 3  are flat. However, the conduits  306  and the evaporator  110  may have any shape. For example, the evaporator  110  may be a plate heat exchanger, where the conduits  306  are defined by plates. Alternatively or in addition, the evaporator  110  may be a tubular heat exchanger, where the conduits  306  are tubes. 
       FIG. 4  illustrates a schematic of an example of an integrated power and thermal management system  400  that includes the cooling system  100 . The IPTMS  400  may include an engine  402 , a gearbox  404 , a generator  406  (two generators are shown in  FIG. 4 ), an electrical bus  408  for the generator  406 , power electronics  410 , thermal management system components  412 , and thermal management coolant loops  414 . The thermal management system components  412  may include the cooling system  100 . 
     The engine  402  may include any source of mechanical power that can drive the generator  406 . Examples of the engine  402  may include a gas turbine engine, an internal combustion engine, a gas engine, a reciprocating engine, a diesel engine, a turbo fan, any other type of engine, propeller(s) of a wind turbine, and any other source of mechanical power. The engine  402  represented in  FIG. 4  is a gas turbine engine. 
     The gearbox  404  may include any device that performs speed and/or torque conversions from a rotating power source to another device. Examples of the gearbox  404  may include gears, a gear train, a transmission, or any other type of device that performs rotational speed and/or torque conversions. 
     The generator  406  may include any type of electrical generator. Examples of the generator  406  may include a synchronous generator, an induction generator, an asynchronous generator, a permanent magnet synchronous generator, an AC (Alternating Current) generator, a DC (Direct Current) generator, a synchronous generator with stator coils, or any other device that converts mechanical power to electric power. 
     The electrical bus  408  may include any connector or connectors that conduct electricity. Examples of the electrical bus  408  may include a busbar, a busway, a bus duct, a solid tube, a hollow tube, a wire, an electrical cable, or any other electrical conductor. 
     The power electronics  410  may include any device or combination of devices that control and/or convert electric power. Examples of the power electronics  410  may include a power converter, a rectifier, an AC to DC converter, a DC to DC converter, a switching device, a diode, a thyristor, an inverter, a transistor, and a capacitor. The power electronics  410  may include semiconductor and/or solid state devices. 
     The thermal management system components  412  may include any component of a thermal management system. Examples of the thermal management system components  412  may include the cooling system  100 , a thermal energy storage, a vapor cycle system (VCS), a conventional air cycle system (ACS), a compressor, a valve, a gas cooler, a heat exchanger, a recuperator, an evaporator, a condenser, a battery, a coolant pump, a controller, and any other component of any type of cooling system. The thermal management system components  412  together and/or separately may have a capability to provide cooling and/or heating. 
     As described in more detail below, the cooling and/or heating provided by the thermal management system components  412  may be distributed by the coolant through the thermal management coolant loops  414 . In more general terms, the combination of the thermal management system components  412  and the thermal management coolant loops  414  form a thermal management system  416 . The thermal management system  416  may provide cooling and/or heating to one or more target devices or target components. These target devices may impose the thermal load  134  on the cooling system  100 . 
     During operation of the integrated power and thermal management system  400  (IPTMS), the IPTMS  400  may provide electrical power to a customer platform component  418 . Alternatively or in addition, the IPTMS  400  may cool and/or heat the customer platform component  418 . The electrical power may by generated by the generator  406  of the IPTMS  400  and the cooling and/or the heating may be provided by the thermal management system  416  of the IPTMS  400 . For example, the cooling system  100  may provide the cooling at least part of the time. 
     The customer platform component  418  may include any device or combination of devices that consumes electricity that may benefit from cooling and/or heating. Examples of the customer platform component  418  may include solid state electronics, a light-emitting diode (LED), an analog circuit, a digital circuit, a computer, a server, a server farm, a data center, a hoteling circuit such as vehicle electronics, a vehicle, an aircraft, a directed-energy weapon, a laser, a plasma weapon, a railgun, a microwave generator, a pulse-powered device, a satellite uplink, an electric motor, an electric device, or any other electronic device that may benefit from heating and/or cooling. 
     The integrated power and thermal management system  400  may be considered “integrated” because electrical power generated by the IPTMS  400  may power devices within the IPTMS  400 , such as components of the thermal management system  416 . For example, the IPTMS  400  may provide electrical power to compressor  102  of the cooling system  100 . Alternatively or in addition, the thermal management system  416  may cool and/or heat components of the IPTMS  400 , such as the power electronics  410 , the gearbox  404 , or any component of the engine  402 . 
     As mentioned above, the cooling and/or heating provided by the thermal management system components  412  may be distributed by a coolant via the thermal management coolant loops  414 . The thermal management coolant loops  414  may include independent loops in which coolant is circulated using, for example, pumps. Heat may be exchanged between two independent loops using a heat exchanger, such as a recuperator, an evaporator, or a condenser. 
     For example, a first loop  420  may be cooled by the thermal management system components  412 . The cooled coolant in the first loop  420  may cool a coolant in a second loop  422  via a heat exchanger (not shown). In one such example, the first loop  420  may include the cooling circuit of the cooling system  100 , the heat exchanger may include the evaporator  110  of the cooling system  100 , and the second loop  422  may include the primary coolant loop  304 . In cooling the coolant in the second loop  422 , the coolant in the first loop  420  may become warmer. The warmed coolant in the first loop  420  may be pumped back to the thermal management system components  412  where the coolant is again cooled. Meanwhile, the cooled coolant in the second loop  422  may be pumped to the customer platform component  418  where the coolant cools the customer platform component  418 . In cooling the customer platform component  418 , the coolant in the second loop  422  may become warmer. The warmed coolant in the second loop  422  may be pumped back to the heat exchanger where the coolant is again cooled by the first loop  420  via the heat exchanger. 
     In another example, the cooled coolant in the first loop  420  may cool a coolant in a third loop  424  via a heat exchanger (not shown) in a similar manner. The cooled coolant in the third loop  424  may cool the power electronics  410  by passing through a power electronics heat exchanger  426  that cools a coolant in a fourth loop  428 . The cooled coolant in the fourth loop  428  may cool the power electronics  410  and/or cool one or more additional independent cooling loops  430  that in turn cool the power electronics  410 . In some examples, the third loop  424  may include the hotel coolant loop  302  and the heat exchanger may include the evaporator  110  of the cooling system  100 . 
     Alternatively or in addition, the cooled coolant in the third loop  424  (or the warmed coolant in the third loop  424  that exits the power electronics heat exchanger  426 ) may pass through a gearbox heat exchanger  432 . The coolant in the third loop  424  that passes through the gearbox heat exchanger  432  may cool oil in an oil loop  434  that flows through the gearbox  404 . In such a configuration, the thermal management system  416  may cool the oil in the gearbox  404 . 
     The thermal management coolant loops  414 , such as the first loop  420 , the second loop  422 , the third loop,  424 , and the fourth loop  428 , that are illustrated in  FIG. 4  are simply examples of the thermal management coolant loops  414 . In other examples, the thermal management coolant loops  414  may include additional, fewer, or different coolant loops than shown in  FIG. 4 . Alternatively or in addition, the thermal management system  416  may cool additional, fewer, or different components of the IPTMS  400  than shown in  FIG. 4 . 
     If the customer platform component  418  includes a directed-energy weapon or any a pulse-powered device, the thermal load  134  placed on the cooling system  100  by the customer platform component  418  may vary substantially over time. The differences between the peaks of the thermal load  134  and the valleys of the thermal load  134  may also be substantial. 
     With respect to generating electrical power, the engine  402  may cause a shaft of the generator  406  to rotate via the gearbox  404  during operation of the IPTMS  400 . As the shaft of the generator  406  rotates, the generator  406  may generate electricity. The electrical bus  408  may transmit the generated electricity to the power electronics  410 . The power electronics  410  may transform, control, and/or store the generated electricity. For example, the power electronics  410  may convert AC current generated by the generator  406  into DC current for delivery to the customer platform component  418 . The power electronics  410  may deliver electricity to one or more components of the thermal management system  416  and/or to any other component of the IPTMS  400 . 
     The IPTMS  400  may include additional, fewer, or different components than shown in  FIG. 4 . For example, the IPTMS  400  may include additional or fewer heat exchangers than shown in  FIG. 4 . As another example, the IPTMS  400  may not include the additional independent cooling loops  430  that cool the power electronics  410 . In still another example, the power electronics  410  may be integrated with the generator  406  so as to eliminate the discrete electrical bus  408  shown in  FIG. 4 . In yet another example, the IPTMS  400  may include a single generator. In some examples, the IPTMS  400  may not include the gearbox  404 . Instead, the generator  406  may be directly coupled to a mechanical output, such as a shaft, of the engine  402 . 
     To clarify the use of and to hereby provide notice to the public, the phrases “at least one of &lt;A&gt;, &lt;B&gt;, . . . and &lt;N&gt;” or “at least one of &lt;A&gt;, &lt;B&gt;, &lt;N&gt;, or combinations thereof” or “&lt;A&gt;, &lt;B&gt;, . . . and/or &lt;N&gt;” are defined by the Applicant in the broadest sense, superseding any other implied definitions hereinbefore or hereinafter unless expressly asserted by the Applicant to the contrary, to mean one or more elements selected from the group comprising A, B, . . . and N. In other words, the phrases mean any combination of one or more of the elements A, B, . . . or N including any one element alone or the one element in combination with one or more of the other elements which may also include, in combination, additional elements not listed. 
     While various embodiments have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible. Accordingly, the embodiments described herein are examples, not the only possible embodiments and implementations. 
     The subject-matter of the disclosure may also relate, among others, to the following aspects: 
     1. A cooling system comprising: 
     a compressor configured to compress a coolant supplied to the compressor in a vapor state; 
     a gas cooler configured to cool the coolant compressed by the compressor; and 
     a recuperator having a high pressure side and a low pressure side, wherein the recuperator, the gas cooler, and the compressor are included in a first portion of a coolant circuit, and the recuperator is configured to: 
     receive the coolant cooled by the gas cooler at an inlet of the high pressure side, 
     supply the coolant to a second portion of the coolant circuit from an outlet of the high pressure side, 
     receive the coolant returned by the second portion of the coolant circuit at an inlet of the low pressure side, 
     transfer heat from the coolant on the high pressure side to the coolant on the low pressure side, and 
     supply the coolant to the compressor from an outlet of the low pressure side. 
     2. The cooling system of aspect 1, wherein the second portion of the coolant circuit includes a vapor-liquid separator having a liquid outlet and a vapor outlet, and the second portion of the coolant circuit is configured to return the coolant, which includes coolant that exits the liquid outlet of the vapor-liquid separator, to the low pressure side of the recuperator.
 
3. The cooling system of aspect 2, wherein the second portion of the coolant circuit includes a means for creating a pressure drop, the means includes an inlet and an outlet, wherein the means is configured to create the pressure drop between the inlet and the outlet of the means, and wherein the inlet of the means is configured to receive a vapor portion of the coolant through the vapor outlet of the vapor-liquid separator, and wherein the coolant that the second portion of the coolant circuit is configured to return to the low pressure side of the recuperator includes a mixture of the vapor portion of the coolant supplied through the outlet of the means and a liquid portion of the coolant received through the liquid outlet of the vapor-liquid separator.
 
4. The cooling system of aspect 3, wherein the means for creating the pressure drop includes a venturi valve configured to create the pressure drop.
 
5. The cooling system of aspect 4, wherein the venturi valve is configured to mix the first portion of the coolant and the second portion of the coolant.
 
6. The cooling system of aspect 2, wherein the second portion of the coolant circuit further includes a liquid return valve, and the liquid return valve is configured to control a flow of the liquid portion of the coolant.
 
7. The cooling system of aspect 6, wherein a processor is configured to cause the liquid return valve to adjust the flow of the second portion of the coolant based on a temperature of the coolant supplied to the compressor.
 
8. The cooling system of aspect 6, wherein a processor is configured to cause the liquid return valve to adjust the flow of the second portion of the coolant such that a temperature of the coolant supplied to the compressor indicates that the coolant is supplied to the compressor in the vapor state.
 
9. A method comprising:
 
     supplying a coolant in a vapor state to a compressor; 
     compressing the coolant with the compressor; 
     cooling the coolant compressed by the compressor with a gas cooler; 
     supplying the coolant cooled by the gas cooler to an inlet of a high pressure side of a recuperator; 
     supplying the coolant from an outlet of the high pressure side of the recuperator to a portion of a coolant circuit; 
     supplying the coolant back from the portion of the coolant circuit to an inlet of a low pressure side of the recuperator; 
     heating the coolant in the low pressure side of the recuperator with thermal energy transferred by the recuperator from the coolant in the high pressure side of the recuperator; and 
     supplying the coolant in the vapor state from an outlet of the low pressure side of the recuperator to the compressor. 
     10. The method of aspect 9 further comprising: 
     reducing a pressure of a vapor portion of the coolant to a reduced pressure, the vapor portion of the coolant received through a vapor outlet of a vapor-liquid separator included in the portion of the coolant circuit; 
     adjusting a flow of a liquid portion of the coolant, the liquid portion of the coolant received from a liquid outlet of the vapor-liquid separator; and 
     mixing the vapor portion of the coolant at the reduced pressure with the liquid portion of the coolant to form a mixture of the liquid portion of the coolant and the vapor portion of the coolant, wherein the mixture is the coolant supplied back from the portion of the coolant circuit to the inlet of the low pressure side of the recuperator. 
     11. The method of aspect 10 wherein the reducing the pressure and the mixing are performed by a venturi valve. 
     12. The method of any of aspects 10 to 11, wherein adjusting the flow of the liquid portion comprises decreasing the flow in response to a decrease in a thermal load cooled by the coolant. 
     13. The method of any of aspects 10 to 12, wherein adjusting the flow of the liquid portion comprises increasing the flow in response to an increase in a thermal load cooled by the coolant. 
     14. The method of any of aspects 10 to 13, wherein adjusting the flow of the liquid portion comprises increasing the flow in response to a temperature of the coolant supplied to the compressor exceeding a threshold value. 
     15. The method of any of aspects 10 to 14, wherein adjusting the flow of the liquid portion comprises decreasing the flow in response to a temperature of the coolant supplied to the compressor falling below a threshold value. 
     16. A cooling system comprising: 
     a compressor configured to compress a coolant supplied to the compressor in a vapor state; 
     a gas cooler configured to cool the coolant compressed by the compressor; and 
     a recuperator having a high pressure side and a low pressure side, wherein the recuperator is configured to receive the coolant cooled by the gas cooler at an inlet of the high pressure side, supply the coolant in the vapor state to the compressor from an outlet of the low pressure side, and transfer heat from the high pressure side to the low pressure side; 
     a thermal expansion valve configured to receive the coolant from an outlet of the high pressure side of the recuperator; 
     an evaporator configured to receive the coolant from the thermal expansion valve and to cool a thermal load with the coolant; 
     a vapor-liquid separator configured to receive the coolant from the evaporator and to separate the coolant into a vapor portion and a liquid portion; 
     a liquid return valve configured to control a flow of the liquid portion out of the vapor-liquid separator; 
     a pressure drop element configured to cause a pressure of the vapor portion of the coolant that exits the vapor-liquid separator to drop to a decreased pressure; and 
     a mixer configured to form a mixture of the vapor portion of the coolant at the decreased pressure and the liquid portion of the coolant received through the liquid return valve, wherein the recuperator is further configured to receive the mixture at an inlet of the low pressure side. 
     17. The cooling system of aspect 16, wherein the pressure drop element and the mixer are integral components of an eductor or an ejector. 
     18. The cooling system of any of aspects 16 to 17, wherein the thermal load is imposed by a directed-energy weapon. 
     19. The cooling system of any of aspects 16 to 18, wherein the evaporator is configured to cool at least two independent coolant loops with a single set of conduits that transport the coolant through sections of the evaporator that correspond to the at least two independent coolant loops.
 
20. The cooling system of any of aspects 16 to 19, wherein the at least two independent coolant loops comprise a hotel coolant loop and a primary coolant loop.