Patent Publication Number: US-2022227198-A1

Title: Ejector-Enhanced Heat Recovery Refrigeration System

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of U.S. patent application Ser. No. 16/094,345, filed Oct. 17, 2018, entitled “Ejector-Enhanced Heat Recovery Refrigeration System”, which is a 371 US national stage application of PCT/US17/29326, filed Apr. 25, 2017, which claims benefit of U.S. Patent Application No. 62/331,313, filed May 3, 2016, and entitled “Ejector-Enhanced Heat Recovery Refrigeration System, the disclosure of which applications are incorporated by reference herein in their entireties as if set forth at length. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to refrigeration. More particularly, the invention relates to heat recovery refrigeration systems such as refrigerated transport systems. 
     A transport refrigeration system used to control an enclosed area, such as the box of a truck, trailer, intermodal container, or the like, functions by absorbing heat from the enclosed area and releasing heat outside of the box into the environment. A number of transport refrigeration units, including units currently sold by assignee, employ a reciprocating compressor to pressurize refrigerant to enable the removal of heat from the box. 
     A number of systems power the vapor compression system via an internal combustion engine. Some systems directly couple the engine to the compressor to mechanically drive the compressor. Others electrically power the compressor via a generator. When an engine is present, a number of systems have been proposed to use heat recovery from the engine. Several recent systems include those of US Patent Application Publication No. 2012/0116594A1 of Aidoun et al., published May 10, 2012. 
     SUMMARY OF THE INVENTION 
     One aspect of the invention involves a refrigerated transport system comprising an engine. A vapor compression system comprises: a compressor for compressing a flow of a refrigerant; a first heat exchanger along a refrigerant flowpath of the refrigerant; and a second heat exchanger along the refrigerant flowpath of the refrigerant. A heat recovery system has: 
     a first heat exchanger for transferring heat from the engine to a heat recovery fluid along a heat recovery flowpath; and a second heat exchanger along the heat recovery flowpath. The heat recovery system second heat exchanger and the vapor compression system first heat exchanger are respective portions of a shared tube/fin package. 
     In one or more embodiments of any of the foregoing embodiments, a separate subcooler has respective legs along the vapor compression flowpath and the heat recovery flowpath and the heat recovery system second heat exchanger is a condenser. 
     In one or more embodiments of any of the foregoing embodiments, there is no separate subcooler; and the heat recovery system second heat exchanger is an evaporator. 
     In one or more embodiments of any of the foregoing embodiments, the heat recovery system further comprises: an ejector having a motive flow inlet, a secondary flow inlet, and an outlet; a pump; and a loop of the heat recovery flowpath passing through the pump to the heat recovery system first heat exchanger, through the motive flow inlet and from the outlet back to the pump. 
     In one or more embodiments of any of the foregoing embodiments, the heat recovery system first heat exchanger has a leg along a coolant flowpath of the engine. 
     In one or more embodiments of any of the foregoing embodiments, the refrigerated transport system further comprises: an engine radiator; and a valve along the coolant flowpath for apportioning a total coolant flow between the radiator and the heat recovery system first heat exchanger. 
     In one or more embodiments of any of the foregoing embodiments, the engine is coupled to the compressor to drive the compressor. 
     In one or more embodiments of any of the foregoing embodiments, the engine is coupled to the compressor to mechanically drive the compressor. 
     In one or more embodiments of any of the foregoing embodiments, the engine is mechanically coupled to an electrical generator and the electrical generator is electrically coupled to an electric motor of the compressor. 
     In one or more embodiments of any of the foregoing embodiments, the refrigerated transport system further comprises a refrigerated compartment in thermal communication with the vapor compression system second heat exchanger. 
     In one or more embodiments of any of the foregoing embodiments, the refrigerated transport is a truck or a trailer. 
     In one or more embodiments of any of the foregoing embodiments, the engine, vapor compression system, and heat recovery system are mounted along a front of the compartment. 
     In one or more embodiments of any of the foregoing embodiments, the vapor compression system refrigerant and the heat recovery fluid are different from each other. 
     In one or more embodiments of any of the foregoing embodiments, the refrigerant is less flammable, less toxic, and/or less harmful to the contents of the refrigerated compartment than the heat recovery fluid. 
     In one or more embodiments of any of the foregoing embodiments, a method for operating the refrigerated transport system comprises, in a first mode: running the engine to drive the compressor to compress the flow of refrigerant and drive the refrigerant along the refrigerant flowpath; transferring the heat from the engine to the heat recovery fluid along the heat recovery flowpath; and rejecting heat from the refrigerant in the vapor compression system first heat exchanger. 
     In one or more embodiments of any of the foregoing embodiments, heat is absorbed by the heat recovery fluid in the heat recovery system second heat exchanger. 
     In one or more embodiments of any of the foregoing embodiments, in the first mode heat is rejected by the heat recovery fluid in the heat recovery system second heat exchanger. 
     In one or more embodiments of any of the foregoing embodiments, a separate subcooler has respective legs along the vapor compression flowpath and the heat recovery flowpath. The method further comprises, in the first mode transferring heat from the refrigerant in the vapor compression system t to the heat recovery fluid in the heat recovery system in the subcooler via a refrigerant-refrigerant heat exchange without airflow. 
     In one or more embodiments of any of the foregoing embodiments, the refrigerated transport system further comprises a radiator and the method further comprises, in the first mode using a valve to apportion engine coolant between the heat recovery system first heat exchanger and the radiator. 
     Another aspect of the invention involves a combined cooling heating and power (CCHP) system comprising: a heat source. A vapor compression system comprises: a compressor for compressing a flow of a refrigerant; a first heat exchanger along a refrigerant flowpath of the refrigerant; and a second heat exchanger along the refrigerant flowpath of the refrigerant. A heat recovery system has: a first heat exchanger for transferring heat from the heat source to a heat recovery fluid along a heat recovery flowpath; and a second heat exchanger along the heat recovery flowpath. The heat recovery system second heat exchanger and the vapor compression system first heat exchanger are respective portions of a shared heat exchanger for rejecting heat to a heat transfer fluid. Further embodiments may variations be along the lines of the other embodiments discussed above and below. 
     In one or more embodiments of any of the foregoing embodiments, the heat source comprises an engine and an electric generator is mechanically coupled to the engine to be driven by the engine. 
     In one or more embodiments of any of the foregoing embodiments, the shared heat exchanger is a water-cooled condenser (WCC). 
     In one or more embodiments of any of the foregoing embodiments, the water-cooled condenser is selected from the group consisting of: a shell and tube WCC; tube-in-tube water WCC; and a brazed plate WCC. 
     Another aspect of the invention involves a system comprising a heat source. A vapor compression system comprises: a compressor for compressing a flow of a refrigerant; a first heat exchanger along a refrigerant flowpath of the refrigerant; and a second heat exchanger along the refrigerant flowpath of the refrigerant. A heat recovery system has: a first heat exchanger for transferring heat from the heat source to a heat recovery fluid along a heat recovery flowpath; and a second heat exchanger along the heat recovery flowpath. The heat recovery system second heat exchanger and the vapor compression system first heat exchanger are respective portions of a shared heat exchanger for rejecting heat to a heat transfer fluid and/or are in common (e.g., series or parallel) along a heat transfer fluid flowpath. Further embodiments may variations be along the lines of the other embodiments discussed above and below. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a refrigeration system of a refrigerated transport system. 
         FIG. 2  is a schematic view of the refrigerated transport system. 
         FIG. 3  is a schematic view of a second refrigeration system. 
         FIG. 4  is a schematic view of a third refrigeration system. 
         FIG. 5  is a schematic view of a fourth refrigeration system. 
         FIG. 6  is a schematic view of a combined cooling heating and power (CCHP) system. 
         FIG. 6A  is a view of a shell and tube condenser of the CCHP system of  FIG. 6 . 
         FIG. 7  is a schematic view of a second CCHP system. 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
       FIG. 2  shows a refrigerated transport unit (system)  20  in the form of a refrigerated trailer. The trailer may be pulled by a tractor  22 . The exemplary trailer includes a container/box  24  defining an interior/compartment  26 . An equipment housing  28  mounted to a front of the box  24  may contain an electric generator system including an engine  30  (e.g., diesel) and an electric generator  32  mechanically coupled to the engine to be driven thereby. A refrigeration system  34  may be electrically coupled to the generator  32  to receive electrical power. 
       FIG. 1  shows further details of the exemplary refrigeration system  34 . The system  34  includes a control system  200 . The control system  200  may include: one or more user interface (e.g., input/output) devices  202 ; processors  204 ; memory  206 ; storage  208 ; and hardware interface devices  210  (e.g., ports). 
     The system  34  further includes a compressor  40  having a suction (inlet) port  42  and a discharge (outlet) port  44 . An exemplary compressor  40  is an electrically-powered reciprocating compressor having an integral electric motor  46 . The compressor  40  may be coupled to the control system  200  to regulate its operation and to the generator  32  via power lines  48  to receive power. The compressor is a portion of a vapor compression system  50  having a recirculating refrigerant flowpath or loop  52 . The exemplary refrigeration system  34  further comprises a heat recovery system  56  having a heat recovery flowpath or loop  58 . 
     Along the refrigerant flowpath  52 , the vapor compression system  50  includes, in a downstream direction from the discharge port or outlet  44 , a heat exchanger  60 , a leg  62 - 1  of a subcooler  62 , an expansion device  64 , and a heat exchanger  66  before returning to the suction port  42 . In a normal operational mode, the heat exchanger  60  is a heat rejection heat exchanger (condenser or gas cooler) and the heat exchanger  66  is a heat absorption heat exchanger (evaporator). Both heat exchangers  60  and  66  may be refrigerant-air heat exchangers having respective fans  70  and  72  driving airflows  520  and  522  along air flowpaths across the heat exchangers. The heat exchanger  66  is in thermal communication with the box interior to cool the box in the normal cooling mode(s). The heat exchanger  60  is in thermal communication with an exterior of the box to reject heat to the airflow  520  in the normal cooling mode. Thus, the airflow  520  may be an external airflow and the airflow  522  may be an interior airflow. 
     As is discussed further below, the subcooler  62  is a refrigerant-refrigerant heat exchanger wherein the leg  62 - 1  along the refrigerant flowpath  52  is in heat exchanger relation with a leg  62 - 2  along the heat recovery flowpath  58 . The heat recovery fluid flowing along the heat recovery flowpath may go through a phase change (e.g., as discussed below) and may otherwise be characterized as a refrigerant. However, for convenience of reference, it will be hereafter referred to as the heat recovery fluid. The heat recovery fluid and the refrigerant may, in some implementations, have identical compositions or may be different. In the latter situation, there will be no fluid communication between the two loops. In the former, there could be. 
     The heat recovery system  56  includes a pump  80  having an inlet  82  and an outlet  84 . The pump is along a sub-loop or flowpath branch  86  of the heat recovery flowpath  58  which also includes the primary flowpath of an ejector  90 . The branch  86  may also provide a convenient location for a receiver (not shown; e.g., at the pump inlet). The ejector has a primary or motive flow inlet  92  at the inlet of a nozzle (e.g., a convergent-divergent nozzle)  94  and an outlet  96  at the downstream end of a diffuser  98 . The ejector further comprises a mixer  100  and a secondary or suction inlet port  102 . Sequentially along the loop  86  proceeding downstream from the pump  80  in a normal operational mode, flow passes through a leg  110 - 1  of a heat exchanger  110 , the ejector primary inlet  92 , the ejector outlet  96 , and a heat exchanger  112  before returning to the pump. 
     A second sub-loop or flowpath branch  120  branches off from the loop  86  between the heat exchanger  112  and pump  80  and passes sequentially through an expansion device  122 , the heat recovery loop leg  62 - 2  of the subcooler  62 , and returns to the ejector secondary or suction port  102 . In normal heat recovery operation, the heat exchanger  110  is a generator heat exchanger transferring heat from the engine to the heat recovery loop. Similarly, the heat exchanger  112  is a heat rejection heat exchanger. The heat recovery loop leg  62 - 2  of the subcooler serves as an evaporator or heat absorption heat exchanger absorbing heat from the vapor compression system leg  62 - 1  of the subcooler. 
       FIG. 1  further shows, associated with the engine  30 , a radiator  130  and a fan  132  (electric or mechanical) driving an airflow  524  across the radiator. For engine cooling, a coolant pump  134  (e.g., mechanical or electric) may drive fluid along a recirculating loop  136  outputting heated coolant from the engine and returning reduced temperature coolant. The coolant may be a conventional engine coolant such as a water and glycol mixture. In the exemplary implementation, a valve  140  allows selective communication of the coolant flow to the heat exchanger  110  and/or the radiator  130 . In this example, the valve  140  is a proportioning valve allowing a stepwise or continuous allocation of the refrigerant flow between the heat exchanger  110  and the radiator  130 . In alternative embodiments, the valve is bi-static. For example, one configuration of a bi-static valve may alternatively deliver coolant to the heat exchanger  110  or radiator while not delivering to the other. Yet other bi-static situations involve having flow to both in at least one condition. 
     In the exemplary implementation, the heat exchangers  60  and  112  are part of a single heat exchanger unit. In an exemplary implementation, the unit is a single bank of tubes and fins with the heat exchangers  60  and  112  representing separate groups of legs of the tubes but sharing fins and tube plates. In the exemplary illustrated implementation, the two heat exchangers  60  and  112  are in series along an air flowpath for the airflow  520 . In the exemplary embodiment in the normal cooling mode, the heat exchanger  112  is downstream of the heat exchanger  60  along the associated air flowpath. The integrated heat exchanger with series airflow may have advantages in terms of economizing on space, economizing on heat exchanger cost, and economizing on fan cost (e.g., by having a single fan servicing both). By having the heat exchanger  60  upstream along the air flowpath, it receives the coldest air in normal operation. 
     A number of variations are possible. Plural of these variations may coexist. One group of variations involves having the compressor  40  mechanically powered by the engine  30  (e.g., directly driven or driven via a transmission) rather than electrically driven. This would eliminate the motor  46  and eliminate the generator  32  (although the engine may include a generator for powering the engine (e.g., providing spark, starting, and the like)). 
     In other variations, the valve  140  may be eliminated so that all coolant passes in series through the heat exchanger  110  and the radiator  130  (e.g.,  FIG. 3 ). 
     Other variations involve eliminating the radiator  130  (and its fan  132 ) so that the coolant supply and return pass directly between the engine and the heat exchanger  110 . The radiator elimination may reduce cost and space consumed. The heat recovery loop takes heat from the engine coolant and the subcooler  62  and rejects it to air at the heat exchanger  112 . In order to protect the engine, the operation of this variation could be prioritized for engine heat rejection. For example this may involve running with the vapor compression system in a less-efficient state so as to consume more power (and thus require the engine to consume more fuel) than if the engine were rejecting heat via the omitted radiator. 
     Other variations involve altering the cycles of the vapor compression system  50  and/or the heat recovery system  56 . The exemplary illustrated systems are relatively simple and many additional features could be added as are known in the art or yet developed. These, for example, include the use of economized vapor compression systems or ejector cycles in the vapor compression system. 
     Further variations involve using engine exhaust heat in addition to or as an alternative to engine coolant for transferring heat to the heat recovery system in the heat exchanger  110 . These variations can increase the amount of heat and the temperature at heat exchanger  110 , leading to increased capacity and efficiency of the heat recovery loop. 
     Yet further variations involve adding a feature such as a de-superheater linking the two loops in addition to the subcooler  62 . An exemplary de-superheater is a refrigerant-refrigerant heat exchanger having a leg along the vapor compression system upstream of the heat exchanger  60  and a leg along the heat recovery flowpath downstream of the subcooler. This may decrease the compressor work and increase the system efficiency. 
     Yet further variations involve placing the heat exchangers  60  and  112  in parallel (e.g.,  FIG. 4 ) along air flowpaths rather than in series while still maintaining them as part of a single unit. In general, parallel flow increases thermodynamic efficiency because both heat exchangers are exposed to ambient inlet air (rather than one being exposed to air heated in the other). However, this may require increased space and potentially cost. In one group of examples, a single fan may pass flow across both in parallel, thus eliminating a fan and its cost. In other implementations, there may be separate fans  70 - 1 ,  70 - 2 , which could provide better control separate flows  520 - 1 ,  520 - 2 . 
     Yet further variations involve effectively eliminating the subcooler  62  and replacing it with an evaporator  63  in the heat recovery system (e.g.,  FIG. 5 ). The evaporator (heat rejection heat exchanger) may be placed in series with the heat exchanger  60  instead of placing the heat rejection heat exchanger  112  in series. In such implementations, the evaporator and the heat exchanger  60  may be the two sections of the integrated single unit. This would involve adding one net fan over the  FIG. 1  embodiment with one fan  70 - 2  driving airflow  520 - 2  only across the heat exchanger  112  and another fan  70 - 1  driving airflow  520 - 1  in series across the added heat recovery system evaporator and the heat exchanger  60 . An exemplary airflow direction places the added evaporator upstream to precool the air (which then flows across the heat exchanger  60 ) and thereby effectively provide interloop heat transfer from the vapor compression system to the heat recovery system. 
     Other possible integrations involve yet further integrating heat exchangers and/or combining air flowpaths. One example modifies the  FIG. 5  configuration by eliminating the fan  70 - 2  and integrating the heat exchanger  112  with heat exchangers  60  and  63  as sections of the integrated single unit (e.g.,  112  could be immediately downstream of  60  along the flowpath  520 - 1  of  FIG. 5 ). 
     Further variations may involve stationary or fixed site installations.  FIG. 6  shows an exemplary fixed site installation or system  320  embodied as a combined cooling, heating, and power (CCHP) system. Generally, like components to the system  20  are shown with like numerals even though the scale or form may ultimately be different in any particular implementation. The CCHP system  320  features refrigerant-water (generically including other liquids such as brine, glycols, other solutions, and the like)) heat exchangers in place of refrigerant-air heat exchangers. In addition to powering the compressor motor  46 , the generator  32  powers additional electric loads  322  of a building (e.g., beyond the loads of the system itself and, more broadly beyond heating ventilation and air conditioning (HVAC) loads). The vapor compression system evaporator  366  (legs  366 - 1  and  366 - 2  in heat exchange relation) cools a water flow  572  along a water flowpath (e.g., including along leg  366 - 2  and pumped via a pump  372  along a water line/conduit to/from cooling loads  371  such as air handling units, building cold water and the like). Condenser sections  360  and  412  along the two loops may be respective sections of a single refrigerant-water heater exchanger  600  ( FIG. 6A ). One example is a shell and tube heat exchanger. Another example is a brazed plate heat exchanger. Yet another example is a tube-in-tube heat exchanger.  FIG. 6  shows a water flow  570  along a water flowpath (e.g., pumped via a pump  369  along a water line/conduit) from/to a cooling tower  650  through the unit  600 . The unit  600  has a water inlet  602  and a water outlet  604 . The exemplary unit  600  is a shell and tube heat exchanger having a shell with a cylindrical wall  610  and end caps  612  and  614 . Plates  616  and  618  define plena at respective end and are spanned by tube groups  620  and  622 . The first end plenum formed by the plate  616  and end cap  612  is subdivided by a plate  624  into respective inlet and outlet plena  630  and  632 . The second end plenum  634  defines a turn in the flowpath with the flowpath proceeding sequentially through the inlet  602  into the plenum  630 , through the tubes  620  to the plenum  634 , and then back through the tubes  622  to the plenum  632  and the outlet  604 . 
     To cool the fluid of the two loops, the interior of the shell is further subdivided by a dividing plate  640  into chamber  642  and  644  which effectively form the condensers  360  and  412 , respectively. The chamber  642  has an inlet  646  and an outlet  648 . The chamber  644  has inlet  647  and an outlet  649 . Refrigerant from the compressor passes into the inlet  646  where it rejects heat to the sections of the tubes  622  and  620  within the chamber  642  before passing out the outlet  648  to go to the subcooler. Similarly, heat recovery fluid from the ejector passes through the inlet  647  and rejects heat to the water flowing in sections of the tubes  622  and  620  within the chamber  644  before exiting the outlet  649 . 
     In yet further variations, instead of being an engine, the heat source  30  may be a fuel cell. 
     Other variations may be along the lines noted above for the refrigerated transport system. For example,  FIG. 7  shows a CCHP system  720  wherein the refrigerant-refrigerant subcooler is replaced with a refrigerant-water precooler  710  having a leg  710 - 2  along the cooling water flowpath rejecting heat to a leg  710 - 1  (acting as an evaporator) along the flowpath  58  upstream of the ejector suction port. This further cools the cooling water from the tower to further cool the refrigerant and heat recovery fluid in the unit  600  (in a fashion similar to the unillustrated modification of  FIG. 5  integrating the condenser  112  into the unit with  60  and  63 ). 
     In a variation on the  FIG. 7  system, rather than having a single integrated unit  600 , there are physically separate WCC for the two loops, each with its own water supply and return from the tower. The precooler (leg  710 - 1  forming heat recovery loop evaporator) cools the water supply (along leg  710 - 2 ) for the vapor compression system&#39;s WCC. Thus, the precooler (leg  710 - 2 ) and the vapor compression system&#39;s WCC are in series along the heat transfer fluid flowpath (the cooling water flowpath for the vapor compression system&#39;s WCC). 
     Thus, it is seen that one or more of several further shared features may exist between the loops of the various systems. A first area involves the physical integration of the heat exchangers of the vapor compression loop and heat recovery loop. Another area which may exist simultaneously with or alternatively to the first is the shared heat transfer fluid (air or water (generically including other liquids such as brine, glycols, other solutions, and the like)) whether in series or otherwise (e.g., the split series configuration of  FIG. 6 ). 
     Yet further variations on the foregoing systems involve the particular working fluids of the vapor compression system and heat recovery system. As mentioned above, they may be the same or different. In one possible area of differences, the refrigerant of the vapor compression system may be relatively non-flammable (and/or less toxic, and/or less harmful to the contents of the refrigerated compartment) when compared to the heat recovery fluid. For example, appropriate isolation allows only potential exposure/venting of the refrigerant into the box interior. The heat recovery fluid may be isolated from the box so as to not be able to accumulate in an enclosed space if there is a leak. Thus, one exemplary combination is a carbon dioxide-based refrigerant (e.g., R744) and a hydrocarbon heat transfer fluid (e.g., R290). An alternative pair is R452A/R245fa. 
     The physical configuration of the system is merely illustrative and may schematically represent any of a number of existing or yet-developed constructions. The inventive methods described below may also be applicable to other constructions. 
     The system may include various additional components including, receivers, filters, dryers, valves, sensors, and the like. 
     One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, when applied in the reengineering of baseline system configuration or the remanufacturing of a baseline system, details of the baseline may influence or dictate details of the particular implementation. Accordingly, other embodiments are within the scope of the following claims.