Abstract:
Described in this application for patent is a novel method and apparatus for providing cooling to an aircraft galley. The aircraft galley is cooled by means of a central aircraft cooling line, including a phase change cooling system and a ram air heat exchanger.

Description:
BACKGROUND 
       [0001]    The present invention relates to a configurable cooling apparatus, and more specifically to a heat exchanger circuit for use in cooling one or more aircraft galley monuments. 
         [0002]    Galleys in private or commercial aircraft are very common. These areas store food and beverages for aircraft passengers on long flights and have become a staple of the airline industry. These galleys often incorporate parking areas (or galley cooling units) where a food transport cart can be stored. The galley cooling units include a cooling element for keeping the food at a temperature lower than the surrounding environment. 
         [0003]    One method of providing cooling to these galley cooling units is the use of a central aircraft cooling line that provides cooling throughout the aircraft and a heat exchanger between the central aircraft cooling line and the galley cooling unit. A fan module may also be provided for circulating the cool air into or over the galley cooling unit to provide cooling. 
         [0004]    The central aircraft cooling line contains a fluid which may have a high specific heat, that is, the fluid is able to absorb large amounts of heat without a significant change in temperature. This allows the fluid of the central aircraft cooling line to maintain a relatively stable temperature while absorbing heat from multiple locations. 
         [0005]    The central aircraft cooling line is typically a closed system where the cooling fluid (or coolant) is cycled through the cooling line to draw heat from various components. Therefore, whatever heat is absorbed by the coolant must be extracted to maintain cooling. 
         [0006]    The central aircraft cooling line is currently cooled by use of a phase change circuit that utilizes a refrigerant in a separate and closed evaporator/condenser fluid line to cool the central aircraft cooling line, and therefore the coolant contained therein. This process is well known to those in the art and generally includes a compressor for compressing a gas, a condenser for converting the gas into a liquid, and an evaporator for converting the liquid into a gas to thereby draw heat from the surrounding environment. 
         [0007]    The compressor of a phase change cooling circuit produces heat in excess of that absorbed by the evaporator and this heat is dissipated through the condenser. As the gas is condensed into a liquid, heat is released and preferably removed by means of a tertiary closed-circuit cooling line. 
         [0008]    The tertiary closed-circuit cooling line generally cycles between a first heat exchanger a second heat exchanger. The first heat exchanger is in thermal communication with the tertiary line and the condenser and the second heat exchanger is in thermal communication with the tertiary line and the ram air. Ram air is air that is drawn from the boundary layer (or near boundary layer) of the outside of the aircraft and passed through a heat exchanger matrix. Ram air at approximately 35,000 feet is typically −55° C. (−67° F.), and may vary by up to 20° C. (36° F.) depending on weather conditions. 
         [0009]    The current method of providing cooling to the galley cooling units requires a number of phase change coolers to provide adequate cooling for the central aircraft cooling line. A cooling method and apparatus that would remove one or more of the phase change coolers would reduce the weight of the aircraft and improve efficiency. 
       SUMMARY 
       [0010]    Described herein is a novel method for cooling the galley of an aircraft. The method includes the steps of providing a preferred temperature for a cooling line, and the cooling line includes a coolant, a heat source, a phase change cooler, and a heat exchanger. Heat from the heat source is collected by means of the coolant which is then transferred to the heat exchanger. The heat is transferred from the heat exchanger to the air source and the output temperature of the coolant from the heat source is determined. If the output temperature is higher than the preferred temperature, than the phase change cooler is engaged to provide supplemental cooling of the coolant. 
         [0011]    Also described herein is an apparatus for aircraft galley cooling. The apparatus comprises a central cooling line, a galley monument, and a preferred temperature for the central cooling line. The cooling line further includes a phase change cooling system, a ram heat exchanger and a galley heat exchanger in thermal communication with the galley monument. If an output temperature of the heat exchanger is less than or equal to the preferred temperature, then the phase change cooling system may be disengaged. 
         [0012]    Also described herein is a method for regulating temperature in a central aircraft cooling line. The method includes the steps of providing a phase change cooling system and a heat exchanger, both in thermal communication with the central aircraft cooling line. The heat loss through the heat exchanger is determined and the phase change cooling system is selectively engaged or disengaged based on this heat loss. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0013]      FIG. 1  shows a view of an aircraft according to one embodiment of the invention. 
           [0014]      FIG. 2  shows a schematic view of the cooling system according to one embodiment. 
           [0015]      FIG. 3  shows a schematic view of a phase change cooler according to one embodiment. 
           [0016]      FIG. 4  shows a top plan view of a heat exchanger. 
           [0017]      FIG. 5  shows a schematic view of a galley cooling unit according to the present invention. 
           [0018]      FIG. 6  shows a schematic view of the cooling system according to an alternative embodiment. 
           [0019]      FIG. 7  shows a flowchart according to one embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]      FIG. 1  shows an illustration of an aircraft  100  according to one embodiment of the present invention. The aircraft generally consists of fuselage  102 , wings  104 , tail,  106 , and nose  108  sections. Further, a ram air intake  110  is located on the aircraft fuselage  102  which provides air cooling. 
         [0021]      FIG. 2  shows a schematic view of the central aircraft cooling line  112  that provides cooling throughout the aircraft  100 . The central aircraft cooling line  112  is a continuous closed circuit, but will generally be described as originating at a phase change cooling system  114 . The central aircraft cooling line  112  may then pass to the aft section of the circuit where it interacts with the various galley cooling units  116 . The central aircraft cooling line  112  may next pass through a cargo hold heat exchanger  118  to cool cargo air  117  and a cabin air heat exchanger  119  to cool cabin air  121 . Finally, the central aircraft cooling line  112  is run through a ram air heat exchanger  120  and through a pump  122  before returning to the phase change cooling system  114  where heat is extracted. 
         [0022]    The phase change cooling system  114  is generally shown in  FIG. 3  and consists of a closed refrigerant line  124 , evaporator  126 , compressor  128 , expansion valve  130  and condenser  132 . As is well known in the art, a phase change cooling system  114  generally operates by compressing a gas by means of the compressor  128 ; dissipating heat from the gas through a condenser  132 , thereby causing the gas to condense into a fluid; passing the fluid through an expansion valve  130 ; and allowing the gas to expand in an evaporator  126 , thereby drawing heat from the surrounding area into the fluid of the closed refrigerant line  124 . 
         [0023]    As further shown in  FIG. 3 , the evaporator  126  may be adjacent to a heat exchanger matrix  134  that is part of the central aircraft coolant line  112 . As the refrigerant in the closed refrigerant line  124  evaporates, heat will be drawn from the heat exchanger matrix  134  of the central aircraft coolant line  112 . The winding path of the heat exchanger matrix  134  and evaporator  126  maximizes heat transfer between the two closed systems. 
         [0024]    Further shown in  FIG. 3 , adjacent to the condenser  132  may be a secondary cooling line  136  which includes a secondary cooling heat exchanger matrix  138  in thermal communication with the condenser  132 . As will be appreciated by those having skill in the art, the secondary cooling heat exchanger matrix  138  includes a winding path to maximize heat transfer between the condenser  132  and the secondary cooling heat exchanger matrix  138 . This secondary cooling line  136  therefore carries heat away from the condenser  132 . 
         [0025]    As further shown in  FIG. 2 , a number of phase change cooling units  114  may be positioned in series, where each unit  114  reduces the temperature in the central aircraft cooling line  112 . According to this arrangement, the output from each heat exchanger matrix  134  would be in fluid communication with the input of the next heat exchanger matrix  134  so that the fluid of the central aircraft cooling line  112  is progressively reduced. Alternatively, although not shown, the phase change cooling units  114  may be provided in parallel, whereby each cooling unit  114  cools a portion of the central aircraft cooling line  112 . 
         [0026]    As further shown in  FIG. 3 , the secondary cooling line  136  draws heat from the condensers  132  of the phase change cooling units  114 . The secondary cooling line  136  is shown to engage the cooling units  114  in parallel so that the temperature of the secondary cooling line  136  may be approximately equal across each condenser  132 . Alternatively, the secondary cooling line  136  may be arranged so that the condensers  132  are in series. 
         [0027]    As further shown in  FIG. 2 , according to one embodiment of the invention the secondary cooling line  136  is in thermal communication with an external heat sink  140 . This external heat sink  140  may be a ram air heat exchanger positioned in a pack bay  142  (see  FIG. 1 ) of the aircraft  100 , or may consist of a secondary line and heat exchanger. 
         [0028]    As shown in  FIG. 4 , the ram heat exchanger  120  generally consists of a serpentine shape in thermal communication with ram air  144  that is passed over the heat exchanger  120 . The ram air  144  draws heat from the central aircraft cooling line  112  by means of this thermal communication. 
         [0029]    Returning to  FIG. 2 , the central aircraft cooling line  112  may include a number of galley cooling units  116  arranged in parallel with one another. These cooling units  116  are further illustrated in  FIG. 5 . Those skilled in the art will appreciate that the galley cooling units may be alternatively arranged in series, or in an arrangement combining parallel and series. 
         [0030]    As shown in  FIG. 5 , the galley cooling unit  116  generally includes a galley heat exchanger  146  with both an input  148  and output  150 . As with previous heat exchangers, the galley heat exchanger  146  includes a serpentine construction. Also shown is an optional fan module  152  that circulates air into and out from the area adjacent a number of galley carts  153 . There may also be present temperature sensors  154  that measure the temperature of the air as it is cycled over the carts  153  and returned. This provides feedback to a control system (not shown) so that the temperature of the food can be regulated. 
         [0031]    Returning again to  FIG. 2 , the central aircraft cooling line  112  may include a cargo hold heat exchanger  118  which may transfer heat to or from the air of the cargo hold, depending on the relative temperatures of the cargo hold air and aircraft cooling line  112 . This cargo hold heat exchanger  118  is substantially similar to the heat exchangers described above. 
         [0032]    Finally, the central aircraft cooling line  112  is passed through the ram heat exchanger  120  which includes a serpentine arrangement similar to heat exchangers previously described. Heat is drawn from the ram heat exchanger  120  by means of ram air  144  that passes over the heat exchanger  120 . This ram air is significantly cold at altitude (for example, −55° C. at 35,000 feet) to provide sufficient cooling for the cold air system. 
         [0033]    As shown in  FIG. 6 , each of the heat exchangers  118 ,  120  may include a bypass path  156  and diverter valve  158  that allows flow of coolant to be diverted around the heat exchangers  118 ,  120 . The diverter valve  158  may be configured to divert some or all of the fluid around the heat exchanger, thereby regulating the temperature of the fluid. Temperature sensors  154  can measure the temperature of the un-cooled fluid (A), the cooled fluid (B) and the combined fluid (C) and regulate the position of the diverter valve  158  to control the temperature in the line  112 . 
         [0034]    The system is preferably automated to maintain a preferred temperature within the system. Because of the electrical draw and increased heat generated by the phase change coolers  114 , it is desirable to reduce the time that these systems are in use. Therefore, a system as illustrated in the flowchart of  FIG. 7  may be utilized to improve the system. 
         [0035]    As shown in  FIG. 7 , the first step in regulating the temperature of the central aircraft cooling line  112  is to determine the fluid temperature entering (T IN ) and leaving (T OUT ) the ram air heat exchanger  120 . This information can be used to determine the amount of heat removed from the cooling line  112  by the ram air heat exchanger  120  based on the difference between these temperatures, flow rate through the cooling line  112 , and specific heat of the coolant, which are all known variables. 
         [0036]    The output temperature (T OUT ) of the ram heat exchanger  120  is next compared against a known preferred temperature (T PREF ) of the cooling line. This preferred temperature (T PREF ) may be a constant or determined based on the amount of cooling required. For example, if fewer galley cooling units  116  are in use, the temperature of the central aircraft cooling line  112  does not need to be as cool as less heat is being introduced into the line  112 . The preferred temperature (T PREF ) is typically within a range from a minimum preferred temperature (T MIN ) to a maximum preferred temperature (T mAx ). When a temperature is referred to as “equal to” the preferred temperature (T PREF ), this means that the temperature is within the acceptable range between the minimum (T MIN ) and maximum (T mAx ) preferred temperatures. A temperature referred to as “below” or “lower than” the preferred temperature (T PREF ) is a temperature that is below the minimum preferred temperature (T MIN ). A temperature referred to as “above” or “higher than” the preferred temperature (T PREF ) is a temperature that is above the maximum preferred temperature (T MAX ). 
         [0037]    If the output temperature (T OUT ) of the ram heat exchanger  120  is above the preferred temperature (T PREF ), then the ram heat exchanger  120  is not dissipating enough heat to cool the central aircraft cooling line  112  on its own, and supplemental cooling from the phase change coolers  114  must be introduced. Based on the temperature difference between the ram heat exchanger  120  output (T OUT ) and the preferred temperature (T PREF ), one or more phase change coolers  114  may be engaged to produce the desired cooling. Alternatively, phase change coolers  114  may be engaged in sequence to progressively step down the temperature in the central aircraft cooling line  112 . 
         [0038]    The output temperature (T OUT ) of the ram heat exchanger  120  may also be below the preferred temperature (T PREF ) for the central aircraft cooling line  112 . In this case, the phase change coolers  114  do not need to be engaged, and control of the system will shift to the temperature sensor  154  that measures the combined temperature (T COMB ). 
         [0039]    The combined temperature (T COMB ) is the temperature of the fluid from the ram heat exchanger  120  and bypass path  156  modified by the proportion diverted by the diverter valve  158 . The combined temperature (T COMB ) may be modified by adjusting the diverter valve  158  to allow more or less flow through the bypass path  156 . The fluid flowing through the bypass path  156  maintains the same high temperature (T OUT ) as the input fluid to the ram heat exchanger  120 , and therefore is used to raise the temperature of the central aircraft heating line  112  to prevent the combined temperature (T COMB ) from falling below the preferred temperature (T PREF ). 
         [0040]    The combined temperature (T COMB ) may be either lower than, equal to, or higher than the preferred temperature (T PREF ). If the combined temperature is below the preferred temperature (T PREF ), then the diverter valve  158  may be adjusted to increase the flow through the bypass path  156  so that the combined temperature (T COMB ) reaches the preferred temperature (T PREF ). This is preferably maintained by a positive feedback control system that monitors and adjusts the diverter valve  158  to maintain the preferred temperature (T PREF ). 
         [0041]    If the combined temperature (T COMB ) is higher than the preferred temperature (T PREF ) (and the output temperature (T OUT ) is less than the preferred temperature (T PREF )), then the diverter valve  158  must be adjusted to reduce the flow through the bypass path  156  to thereby reduce the temperature (T COMB ) of the combined fluid. 
         [0042]    If the combined temperature (T COMB ) is equal to the preferred temperature (T PREF ) (and the output temperature (T OUT ) is less than the preferred temperature (T PREF )), then the flow through the bypass path  156  is appropriate and should be maintained. 
         [0043]    It may be appreciated by those having skill in the art that the bypass path  156  and diverter valve  158  may be combined with any of the heat exchanger matrices in the above described system, and a control system may be devised to monitor input, output, and combined temperatures within the central aircraft cooling line  112 . For example, sensors (not shown) may detect the temperature or presence of galley carts  153  in one or more of the galley cooling units  116  and selectively allow flow through the heat exchanger  146  of the galley cooling unit  116  to conserve energy. 
         [0044]    The invention has been described as utilizing a ram heat exchanger in communication with an exterior air source to provide heat transfer from the central cooling line. However, the ram heat exchanger may be replaced with any heat exchanger in thermal communication with outside air. One example of such a heat exchanger is a series of cooling lines adjacent or near the skin of the aircraft that utilize conduction to transfer heat from the cooling line to the aircraft skin and then to the outside air. 
         [0045]    The invention has been generally described with respect to a preferred embodiment. This embodiment is intended to be exemplary rather than limiting. Further, those skilled in the art will recognize that various modifications of the described embodiment may be made without departing from the scope of the invention. Any limitations will appear in the claims as allowed.