Abstract:
Environmental control systems and methods to control environmental temperature of an enclosed space by integrating a passive heat exchange subsystem (e.g., a loop heat pipe (LHP) heat exchange subsystem) having a closed loop heat exchange fluid circuit in heat-exchange relationship with the enclosed space for providing environmental temperature control therewithin, a RAM-air subsystem having a RAM-air circuit for circulating RAM cooling air, and a vapor compression cycle machine (VCM) subsystem having a VCM fluid circuit having a compressor, an evaporator, a condenser and an expansion valve.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based on and claims domestic priority benefits under 35 USC §119(e) from U.S. Provisional Application Ser. No. 61/581,378 filed on Dec. 29, 2011, the entire contents of which are expressly incorporated hereinto by reference. 
     
    
     FIELD 
       [0002]    The embodiments disclosed herein relate generally to the environmental control and thermal management (e.g., heating, cooling) of compartments/enclosures (e.g., within an aircraft fuselage) using an integrated architecture of environmental control systems, such as heat pipes, skin heat exchangers and/or vapor compression cycle systems. Embodiments of the methods and systems disclosed herein enable aircraft compartments/enclosures to be cooled with minimal aircraft power consumption (ultimately, minimal aircraft fuel consumption) demand during various phases of aircraft operation. 
       BACKGROUND 
       [0003]    The concepts of future generation aircraft systems tend to demand an increase in electric power consumption. As a consequence, these systems will require the dissipation of more heat per volume. The increase in heat dissipation and the recent requirements to reduce aircraft fuel consumption conflict with one another and thus require the advent of more efficient cooling systems. 
         [0004]    Currently, aircraft compartments/enclosures (electronic bays, galleys and the like) are provided with cooling systems that are commonly based on air cycle and/or vapor cycle systems and are not optimized in terms of the fuel penalty that such systems may extract on the overall aircraft performance. Thus, the higher the cooling requirement, the higher the cooling system power consumption and, as a consequence, the higher the aircraft fuel consumption. These cooling systems operate during all phases of the flight, including when the aircraft is on ground. 
         [0005]    However, a dramatically large heat rejection potential exists when an aircraft is in flight due to the significant temperature difference between outside air (heat sink) and the specific compartments/enclosures/equipment being cooled. In order to develop more efficient cooling systems, there is a need to minimize the thermal resistance between the equipment and the heat sink. 
         [0006]    Recently, a more efficient cooling system has been proposed by US Published Application No. 2004/0159119 (incorporated fully by reference herein) that mainly includes a liquid loop, a eutectic thermal battery and heat pump and skin heat exchanger (SHX). Similarly, US Published Application No. 2007/0095521 (incorporated fully by reference herein) mainly proposes the combination of loop heat pipe (LHP), cold storage unit and SHX. 
         [0007]    There are several problems to be solved before greater fuel efficiencies can be fully realized. For example, current technologies lack a smart management of the available heat sinks for a compartment/enclosure cooling, causing more fuel consumption (fuel penalty over the aircraft performance) than is necessary, since the availability of heat sinks is not sufficiently used. For instance, sometimes a vapor compression cycle machine (VCM) needs to be used to cool electronic equipment inside the cabin, in spite of the cool air already available outside of the in-flight aircraft. 
         [0008]    In addition, there currently is a lack of flexibility for use of the available heat sinks. By way of example, one electronic box cannot be installed in a predetermined compartment/enclosure because the outside air heat sink is located to far of a distance from that compartment/enclosure. 
         [0009]    Furthermore, high thermal resistance between the compartment/enclosure (heat load) and the heat sink typically exists. This high thermal resistance requires active cooling systems (heat pumps) even when the temperature of the heat load is higher than the temperature of the heat sink. This effect happens most of the time during an aircraft mission. LHP&#39;s and other phase change passive heat transmission devices can be useful to diminish this thermal resistance. 
         [0010]    It is therefore towards providing solutions to such problems that the embodiments of the present invention are directed. 
       SUMMARY 
       [0011]    The disclosed embodiments herein are provided so as to achieve the goal of removing heat from a compartment/enclosure while minimizing the fuel penalty over the entire aircraft operation by using the features to be discussed in greater detail below. Additionally the heat removed from one compartment/enclosure may also be used as heat source for another compartment/enclosure. It may also be used for heating of an internal or external surface of the aircraft, as may be required for thermal management or ice and atmospheric protection. Generally, the embodiments as disclosed herein integrate various environmental control systems, such as heat pipes and skin heat exchangers, to minimize thermal resistance and reduce system power consumption. 
         [0012]    According to some embodiments, a combination of multiple innovative environmental control components may be employed, for example (1) a loop heat pipe (LHP) condenser integrated with a vapor compression cycle machine (VCM) evaporator, in a single heat exchanger, and (2) a compact skin heat exchanger (SHX) embedded into a duct that is equipped with a ground cooling fan. 
         [0013]    A system is also provided according to some embodiments for cooling a compartment/enclosure using a smart integration among different technologies for heat transport and heat sinks (VCM, SHX, LHP, RAM-air with ground cooling fan) and a proper operational logic, comprised of a hybrid system capable to operate with less power consumption over an entire aircraft mission, taking advantage from any one of the technologies being applied. 
         [0014]    According to some embodiments, environmental control systems and methods are provided which control environmental temperature of an enclosed space by integrating a loop heat pipe (LHP) heat exchange subsystem having a closed loop heat exchange fluid circuit in heat-exchange relationship with the enclosed space for providing environmental temperature control therewithin, a RAM-air subsystem having a RAM-air circuit for circulating RAM cooling air, and a vapor compression cycle machine (VCM) subsystem having a VCM fluid circuit comprising a compressor, an evaporator and a condenser. The evaporator of the VCM subsystem may thus be integrated with the LHP heat exchange subsystem by being in operative heat-exchange relationship therewith, while the condenser of the VCM subsystem may be integrated with the RAM-air system so as to be in operative heat-exchange relationship therewith. 
         [0015]    Some embodiments may include a LHP condenser of the LHP subsystem in operative heat-exchange relationship with the VCM evaporator of the VCM subsystem. The LHP heat exchange subsystem in other embodiments may also be provided with a LHP condenser skin heat exchanger (SHX), and a control valve for directing the working fluid to either the LHP condenser or the LHP condenser SHX. 
         [0016]    The RAM-air circuit of certain embodiments may include an air duct having an inlet and an inlet control door for controlling air flow into the duct, and a cooling fan for drawing air into the inlet and through the duct. Other embodiments may be provided with a RAM-air subsystem which comprises an embedded skin heat exchanger (SHX) in operative heat-exchange relationship with the air flow in the duct. 
         [0017]    Certain other embodiments may be provided with a LHP heat exchange subsystem having a LHP condenser in operative heat-exchange relationship with the VCM evaporator of the VCM subsystem, and a LHP condenser skin heat exchanger (SHX). A control valve may thus be provided for directing the working heat exchange fluid to either the LHP condenser of the LHP heat exchange subsystem, the LHP condenser SHX of the LHP heat exchange subsystem or the embedded skin heat exchanger SHX of the RAM-air subsystem. 
         [0018]    The VCM subsystem may include a VCM condenser skin heat exchanger (SHX) downstream of the VCM condenser. In certain embodiments, the VCM condenser SHX may be in operative heat-exchange relationship with an on-board fluid, such as on-board fuel and/or cabin air. Other embodiments may be provided with a VCM subsystem having a bypass valve to direct the VCM fluid circuit to or bypass the VCM fluid circuit around the VCM condenser SHX. 
         [0019]    The heat released by skin heat exchangers may be used for heating an internal or external surface of the aircraft. For example, the heat released by a SHX can be used as sole or complementary ice and rain protection system for the external surface which it constitutes or is part of. Also, this heat can be used to heat door sills, galleys, among other aircraft regions. 
         [0020]    These and other aspects and advantages of the present invention will become more clear after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof. 
       ACRONYMS 
       [0021]    Structures and systems may sometimes be referenced herein by the following acronyms:
       LHP—loop heat pipe   CPL—capillary pumped loop   LTS—loop thermosyphon   SHX—skin heat exchanger   VCM—vapor compression cycle machine   E-bay—electronic bay       
 
         [0028]    It will be understood that whenever LHP, CPL, LTS appear hereinbelow, all the possible variants for phase change heat dissipation devices are contemplated such as, for example, conventional heat pipes, thermosyphons, pulsating heat pipes, and the like. Therefore, reference to any specific acronym is non-limiting and merely employed for ease of discussion. 
     
    
     
       BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS 
         [0029]    The disclosed embodiments of the present invention will be better and more completely understood by referring to the following detailed description of exemplary non-limiting illustrative embodiments in conjunction with the drawings of which: 
           [0030]      FIG. 1  is a schematic diagram of an embodiment of a system architecture for cooling a compartment/enclosure; 
           [0031]      FIG. 2  is a schematic diagram of a LHP/CPL/LTS loop being used to cool the compartment/enclosure, with the SHX being used to cool the LHP condenser; 
           [0032]      FIG. 3  is a schematic diagram of a RAM-air duct embedded finned skin heat exchanger which may be used to cool the LHP condenser; 
           [0033]      FIGS. 4A and 4B  are respective side and top views of a RAM-air duct embedded, finned SHX; 
           [0034]      FIG. 5  is a schematic diagram of a VCM being used to cool the LHP condenser; SHX being used to cool the VCM condenser fluid (NACA air inlet closed); 
           [0035]      FIG. 6  is a schematic diagram of a VCM being used to cool the LHP condenser; NACA/RAM-air being used to cool the VCM condenser fluid (NACA air inlet shut off) with a ground cooling fan static operation; 
           [0036]      FIG. 7  is a schematic diagram of a system embodiment without the SHX being embedded into the RAM-air duct; 
           [0037]      FIG. 8  is a schematic diagram of a system embodiment without both the SHX for the LHP condenser and the SHX for the VCM condenser; and 
           [0038]      FIG. 9  is a schematic diagram of a system embodiment with a VCM condenser being cooled by other means, such as on board fuel or ambient cabin air. 
       
    
    
     DETAILED DESCRIPTION 
       [0039]    Many of the details, dimensions, angles and other features shown in the figures of the present patent application are merely illustrative of particular embodiments of the invention. Accordingly, other embodiments can have other details, dimensions, angles and features, without departing from the spirit or scope of the present inventions. 
         [0040]    Several embodiments of innovative systems, as well as their logic of operation, are described hereinbelow as solutions to operate the aircraft with lower fuel consumption. 
         [0041]    The architecture associated with one embodiment of an environmental control system  10  is shown schematically in  FIG. 1 . As is shown the architecture of the environmental control system  10  is comprised of multiple subsystems to dissipate the compartment/enclosure thermal load to the outside air (heat sink), namely the LHP subsystem  12  having an LHP evaporator  26  and a LHP condenser SHX  28  (see explanation of  FIG. 2 ); the subsystem  14  having the internal embedded SHX  30  associated with the RAM-air circuit  20  (see explanation of  FIG. 3  and  FIGS. 4A-4B ); the VCM subsystem  16  having a VCM condenser SHX  42  (see explanation of  FIG. 5 ); and the subsystem  18  having a VCM condenser, conventional compact heat exchanger  40  (see explanation of  FIG. 6 ). The subsystems  14  and  18  depend on RAM air provided by the RAM-air circuit  20 , whereas the LHP subsystem  12  is a passive system and the VCM subsystem  16  is an active system. As will be explained in greater detail below, an on-board controller OBC is provided with environmental inputs (e.g., outside air temperature, aircraft velocity and weight on wheels) so as to selectively operate one or more of the subsystems  12 ,  14 ,  16  and/or  18  in dependence upon the phase of aircraft operation (e.g., in flight or on ground) and/or the outside aircraft air temperature by selective positioning of the system control valve CV. 
         [0042]    The LHP subsystem is shown in greater detail in  FIG. 2 . As shown, the equipment  22  installed in the compartment/enclosure  24  dissipates its thermal load to an LHP evaporator  26 , through air or other cooling medium circulating with in the compartment/enclosure  24  (e.g., via circulation fans (not shown)). The compartment/enclosure  24  (represented by the double line boundary around the equipment  22  and the LHP evaporator  26 ) may be an electronic compartment, galley compartment, baggage, live animal compartment or others. The compartment/enclosure  24  may also be only an electronic box properly equipped with a cold plate slot or surface, being the LHP evaporator part of such a cold plate. The control valve CV to select between one of the LHP condenser/VCM evaporator  43  or the LHP condenser/SHX  28  may or may not be necessary, since in some configurations there is a possibility that the LHP evaporator  26  can select passively the more suitable condenser  28  or  43  (i.e., the coldest condenser). This is the mode of operation for either high altitudes or during a cold-day on ground/low altitude operation. For these cold outside air operational conditions, the LHP condenser/SHX  28  is often enough to dissipate the equipment thermal load. 
         [0043]    The mode of operation for subsystem  14  depicted by  FIG. 3  is advantageous when outside air is at sufficiently low temperatures, ranging from cold to standard temperature days. The heat removal from the embedded finned SHX  30  will thus function also on the ground by cooling fan  32  airflow inside the duct  30 - 2  (see  FIG. 4 ) of the RAM-air circuit  20 . Heat removal during this mode of operation (e.g., standard temperature days on ground) would otherwise require a VCM operation or the installation of a conventional compact heat exchanger into the RAM-air line. A VCM condenser  40  (see  FIG. 5 ) could be inactive (i.e., VCM compressor  41  is turned off) or active in a lower capacity mode. The ground cooling fan  32  may be turned on, and the variable area NACA air inlet controlled door  30 - 3   a  may be fully open, based on outside air temperature, aircraft velocity and/or weight on wheels. The use of the embedded finned SHX  30  can be advantageous over a conventional compact heat exchanger because it is simpler, easier to install and maintain, and causes less pressure drop on the RAM-air circuit  20 . At flight conditions, it is possible that the ground cooling fan  32  becomes a ram air flow restriction. When sufficient ram air pressure is available in-flight, the fan windmills. However, the RAM-air circuit  20  presents means to diminish the flow restriction of the ground cooling fan  32  at flight operation, not shown in FIGS. (e.g.: installation of a fan bypass check valve that opens at flight). 
         [0044]    Accompanying  FIGS. 4A and 4B  depict side and top plan views, respectively, of a RAM-air duct embedded, finned SHX  30  that may be used in the subsystem  14  shown in  FIG. 3 . The finned SHX  30 - 1  is preferably installed on the RAM air duct wall  30 - 2 , with the fins (a few of which are identified in  FIG. 4B  as reference numeral  30 - 1   a ) oriented facing the internal side of the duct wall  30 - 2  and oriented along the longitudinal direction thereof (i.e., in the same direction as the RAM air flow (arrow A 1 ). The SHX  30 - 1  may act as a condenser for the LHP. Alternatively, the SHX  30 - 1  may be provided without fins if they are not deemed to be necessary. Ambient air, moved by the ground cooling fan  32 , intakes through the NACA duct RAM-air intake  30 - 3 , passes through the surface of the fins  30 - 1   a  (plain/strip/louvered fins or other variations) associated with the SHX  30 - 1  and is discharged (arrow A 2 ) from the RAM-air line through the outlet  30 - 4  so as to be directed to the VCM condenser  40  associated with the subsystem  16 . 
         [0045]    Accompanying  FIG. 5  shows an operational mode of subsystem  16  when outside air is not cold enough to operate the system  10  under the configurations described and shown by the subsystems  12  and  14  depicted in  FIGS. 2 and 3 . In the subsystem  16  of  FIG. 5 , however, the use of RAM-air to cool the VCM condenser  40  downstream of the VCM compressor  41  is not necessary, since the SHX condenser  42  of the VCM would have sufficient airflow for heat removal by outside air convection. A two-way controlled valve  44  selects operation of the SHX condenser  42  of the VCM via line  46  or selects a bypass line  48  (see also  FIG. 1 ). As shown by the X&#39;s in  FIG. 5 , the ground cooling fan  32  is turned off, and the NACA inlet controlled door  30 - 3   a  is fully closed in response to a signal output of control logic based on outside air temperature, aircraft velocity and weight on wheels issued by the on-board controller OBC (see  FIG. 1 ). No drag due to RAM-air is thus imposed on the aircraft in such a configuration since the NACA inlet door  30 - 3   a  is fully closed. The VCM subsystem  16  needs to be operated, because the temperature difference between the equipment and the outside air (the heat sink) is low or even negative (equipment desired temperature is lower than heat sink outside air temperature). The SHX condenser  42  of the VCM subsystem  16  dissipates both the thermal load from the equipment (e.g., the LCP condenser/VCM evaporator  43 ) and the energy put into the system by the VCM compressor  41 . For this reason the skin temperature of the SHX  42  is higher than the temperature of the SHX  28  as described in  FIG. 2 . As such, the SHX  42  requires less surface area than the SHX  28 . The cooled working fluid may then be returned to the LHP evaporator  26  via lines  56   a  and  52   a.    
         [0046]    Accompanying  FIG. 6  depicts an operational mode for the hottest days, on ground or flying at low altitudes in relatively warm outside air. The VCM subsystem  16  needs to be turned on using either the RAM-air circuit  20 , for in-flight conditions, or the ground cooling fan  32 , for on ground operation. In such a condition, the two-way valve  44  is commanded by the on-board controller OCB to bypass the SHX condenser  42  of the VCM subsystem (i.e., via line  48  as shown also  FIG. 1 ). The ground cooling fan  32  may then be turned on, and the control door  30 - 3   a  of the NACA inlet  30 - 3  may be fully opened, based on outside air temperature, aircraft velocity and weight on wheels as commanded by the on-board controller OCB. 
         [0047]    The heat removed from the compartment/enclosure, by air or other cooling medium, or even using a cold plate or similar device, is drawn through the LHP evaporator  26 . Inside the LHP  26 , the working fluid is evaporated, by absorbing the heat from the equipment. The vaporized working fluid then flows towards the system control valve CV via line  50 . The on-board controller OCB can thus command the control valve CV to assume one of three different conditions so that the vaporized working fluid can then be directed in the following respective three different routes:
       1. For cold days, on ground or in-flight (see explanation of  FIG. 2 ), the vaporized working fluid is directed to the LHP condenser SHX  28  via line  52  so that the heat may be dissipated to the outside cold air by convection. The cooled working fluid is then returned to the LHP evaporator  26  via line  52   a.  This SHX  28  can be either an outside face plain SHX or a finned SHX as shown in  FIGS. 4A and 4B . This configuration does not consume any energy to operate (except energy for air movement inside the compartment/enclosure  24 , that would always be present), since the LHP condenser is a passive device.   2. If operating when outside air is at sufficiently low temperatures (ranging from cold to standard days), on ground, another configuration needs to be used, since the lack of induced airflow over the LHP condenser SHX  28  will not allow it to be used. In this case the configuration described above in relation to  FIG. 3  is used. For this purpose, the control valve CV drives the LHP working fluid in line  50  towards the RAM-air duct embedded finned SHX  30  via line  54 . The cooled working fluid is then returned to the LHP evaporator  26  via line  54   a  and  52   a.  The heat removal from this embedded finned SHX  30  depends upon the airflow provided by the ground cooling fan  32  inside the RAM-air duct  32  (see  FIGS. 4A and 4B ). During this mode of operation the VCM compressor  41  is turned off by the controller OBC. The controller OBC also turns the ground cooling fan  32  on, and fully opens the control door  30 - 3   a  associated with the variable area NACA air inlet  30 - 3 , based on outside air temperature, aircraft velocity and weight on wheels. The energy consumption during this mode of operation is therefore attributed only to the operation of the ground cooling fan  32 .   3. The control valve CV may be commanded to direct the LHP working fluid in line  50  towards the LHP condenser/VCM evaporator  43  via line  56  under the following conditions:   a. For hot days, with aircraft flying at low altitudes, the outside air may not be cold enough to operate the system  10  under the configurations of the subsystems  12  and  14  as described in relation to  FIGS. 2 and 3 , respectively. As a result, the VCM subsystem  16  is then required to be operated because the temperature difference between the equipment  22  within the enclosure  24  and the outside air (the heat sink) is low or even negative (e.g., equipment desired temperature lower than the available heat sink outside air temperature). However, the use of RAM-air to cool the VCM condenser  40  is not necessary, since the SHX condenser  42  of the VCM subsystem  16  would have sufficient heat removal capacity provided by external air convection (see  FIG. 5 ). The on-board controller OBC thus turns off the ground cooling fan  32 , and fully closes the inlet control door  30 - 3   a  of the NACA inlet  30 - 3  following a control logic based on outside air temperature, aircraft velocity and weight on wheels; or   b. For the hottest days, the outside air is not cold enough for the heat to be dissipated through the SHX condenser  42  of the VCM subsystem  16  for on ground aircraft operation, and for in-flight operation at low altitudes (e.g., with warm outside air temperatures). Under such conditions, the on-board controller OCB operates the control valve  44  so as to bypass the SHX condenser  42  of the VCM subsystem  16  and the VCM condenser  40  uses either RAM-air, for in-flight operation via the RAM-air subsystem  20 , or the ground cooling fan  32  of the RAM-air subsystem  20 , for on ground operation. For on ground operation the ground cooling fan  32  is turned on, and the NACA inlet controlled door  30 - 3   a  is fully open. For in-flight operation, the ground cooling fan  32  is turned off and the NACA inlet  30 - 3  and its associated RAM-air provides outside air to cool the VCM condenser  40 .       
 
         [0053]    Table 1 below presents a summary of the operational modes discussed above. 
         [0000]    
       
         
               
             
               
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Predicted modes of operation as a function of: 
               
               
                 ambient temperature, on ground versus in-flight 
               
               
                 operation and high altitude versus low altitude 
               
             
          
           
               
                   
                 Flight 
               
             
          
           
               
                   
                 Ground 
                 Low altitude 
                 High altitude 
               
               
                   
                   
               
             
          
           
               
                 Cold 
                 LHP using SHX 
                 LHP using SHX 
                 LHP using SHX 
               
               
                 day 
                 as a condenser; 
                 as a condenser; 
                 as a condenser; 
               
               
                   
                 zero consumption 
                 zero consumption 
                 zero consumption 
               
               
                   
                 (FIG. 2) 
                 (FIG. 2) 
                 (FIG. 2) 
               
               
                 Standard 
                 LHP using inter- 
                 LHP using inter- 
               
               
                 day 
                 nally embedded 
                 nally embedded 
               
               
                   
                 SHX into a duct, 
                 SHX into a duct, 
               
               
                   
                 cooled by a 
                 cooled by a 
               
               
                   
                 ground cooling fan; 
                 ground cooling fan; 
               
               
                   
                 consumption of a 
                 consumption of a 
               
               
                   
                 ground cooling fan 
                 ground cooling fan 
               
               
                   
                 (FIG. 3) 
                 (FIG. 3) 
               
               
                 Hot 
                 LHP using VCM, 
                 LHP using VCM, 
               
               
                 day 
                 with VCM 
                 with VCM 
               
               
                   
                 condenser being 
                 condenser being 
               
               
                   
                 cooled by the 
                 cooled by the 
               
               
                   
                 ground cooling 
                 SHX condenser of 
               
               
                   
                 fan; consumption 
                 the VCM; 
               
               
                   
                 of both the 
                 consumption of the 
               
               
                   
                 VCM compressor 
                 VCM compressor 
               
               
                   
                 and ground cooling 
                 (FIG. 5) 
               
               
                 Very 
                 fan (FIG. 6) 
                 LHP using VCM, 
               
               
                 hot 
                   
                 with VCM 
               
               
                 day 
                   
                 condenser being 
               
               
                   
                   
                 cooled by NACA/ 
               
               
                   
                   
                 RAM-air; 
               
               
                   
                   
                 consumption of 
               
               
                   
                   
                 the VCM 
               
               
                   
                   
                 compressor (FIG. 6) 
               
               
                   
               
             
          
         
       
     
         [0054]    Other embodiments based on the system architectures described above are shown by  FIGS. 7 ,  8  and  9 . As shown in  FIG. 7 , for example, the system  70  is similar to the system  10  described previously in connection with  FIG. 1 , but omits the line  54 , the internal embedded finned SHX  30  and cooling fan  32  associated with the RAM-air circuit  20 . Thus, in the embodiment of  FIG. 7 , the control valve CV is provided so as to direct the working fluid in line  50  to either the LHP condenser  43  or the LHP condenser SHX  28 . 
         [0055]    The system  80  shown in  FIG. 8  is similar to the embodiment shown in  FIG. 7  but omits the LHP condenser SHX  28  and the VCM condenser SHX  42 . As such, the control valve CV and the bypass valve  44  are unneeded in the  FIG. 8  embodiment. 
         [0056]    The system  90  shown in  FIG. 9  is similar to the system depicted in  FIG. 1 , but omits the subsystem  14  as described above in relation to  FIG. 3 . That is, the system  90  of  FIG. 9  does not include the internal embedded finned SHX  30  or the line  54 . Consequently the control valve CV in the system  90  need only direct the working heat-exchange fluid in the LHP subsystem  12  to either the LHP condenser  43  or the LHP condenser SHX  28 . The VCM subsystem of system  90  includes a VCM condenser heat exchanger that operates in heat-exchange relationship with an on-board fluid subsystem  20 - 1  (such as on-board fuel and/or cabin air) downstream of a VCM condenser  40  that operates in heat-exchange relationship with the ram air circuit  20 . A two-way controlled valve  44  selects operation of the VCM condenser  42  via line  46  (see  FIG. 9 ) or selects a bypass line  48  (see also  FIG. 9 ). 
         [0057]    While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope thereof.