Abstract:
An improved aircraft air chiller unit particularly suited for an aircraft galley that requires refrigerated or cooled beverage/meal carts and/or chilled storage compartments. The chiller of the present invention takes the form of a line replaceable unit (“LRU”) and incorporates a liquid-cooled refrigerant vapor compression cycle, arranged in a housing with a vertical orientation. Because of the vertical orientation, ducting on the rear surface of the chiller is omitted, reducing the overall footprint.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims priority from U.S. Provisional Patent Application No. 61/885,388, filed Oct. 1, 2013, the content of which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    It is customary in the airline industry to provide food and beverages on flights to the passengers as well as the crew. Depending upon the duration of the flight, the service can be as little as beverages and a light snack to multiple meals for longer flights. To store, prepare, and serve food and beverage on an aircraft requires that provisions be made to the aircraft to safely maintain the food and drinks in a proper manner. For perishables, that means preserving the food and drinks in an environment that will keep the products fresh and viable. In most cases, this means a refrigeration system that can store and chill food and beverages until they are ready to be served to the passengers. 
         [0003]    Large commercial passenger carrying airplanes predominantly utilize one of two cooling systems for maintaining perishable food stuffs and non-perishable beverages at their optimum temperatures. Chilling is necessary to preserve perishables and make certain beverages and foods more palatable, especially during long haul and ultra-long haul aircraft journeys. The first cooling system utilizes a standard vapor cycle based air chiller that utilizes conventional refrigerant gas compression and expansion technology to generate a secondary re-circulated chilled air loop. The chilled air is generally supplied and returned via thermally insulated air ducting to and from a suitable storage structure, such as a galley. The air chiller may be located in the galley, or mounted proximally in another part of the aircraft airframe. 
         [0004]    The second type of cooling system utilizes the same conventional refrigerant gas compression and expansion technology, but the cooling medium is a chilled liquid rather than a gas. Chilled liquid has a higher thermal capacity but requires more sophisticated pumping and conduit architecture to operate the system. The chilled liquid is pumped in a closed loop to and from a suitable storage structure such as a galley. The chilled liquid in some cases is configured to serve a large centralized system for the whole aircraft. In other cases, the chilled liquid can be circulated at each separate galley compartment to form a local area chilling loop, or be based on each individual galley as a standalone system. At the galley, the liquid is passed via a control valve and electronic control system to a heat exchanger, where an electric axial (or other) fan blows or sucks air through its matrix and to the storage compartment that requires chilling, such as, for example, a galley cart bay or refrigeration compartment. The heat exchanger fan and its control system (though not necessarily all) are grouped together to form a chilled air recirculation unit that may be fitted in or on the galley or remotely from it, or the galley complex. 
         [0005]    One drawback of these various chiller systems is that they take up a large percentage of available space in the galley, which is at a premium in an aircraft for obvious reasons. Further, the chillers tend to be very heavy, which is also a drawback to their use on aircraft. There are also issues with condensation collection and removal, and the need for improvements in heat transfer efficiency. Accordingly, it would be beneficial to have a chiller system that takes up less space and reflects a reduction in weight over conventional chiller systems currently in use, while providing for condensation collection and improved heat transfer efficiency. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention is an improved aircraft air chiller unit that weighs less than its counterparts and has a reduced overall foot print. This compact system is particularly suited for an aircraft galley that requires refrigerated or cooled beverage/meal carts and/or chilled storage compartments. The present invention is also particularly useful for large single aisle aircraft galleys and point of use (POU) carts. The chiller of the present invention is seated in a cavity created at the side of the galley compartment below the work deck of the aircraft galley. In a preferred embodiment, the chiller takes the form of a line replaceable unit (“LRU”), in other words a component that can be replaced in the field. The chiller incorporates a liquid-cooled refrigerant vapor compression cycle, arranged in a housing with a vertical orientation. A plurality of axial fans along an upper surface draw air into the unit, where it is introduced into a vapor cycle. The axial fans can, in an alternate embodiment, be replaced with scroll type fans. The vapor cycle includes an evaporator, an expansion valve, a liquid cooled condenser, and a compressor in a compact, vertical arrangement. The chilled air re-circulates from the top of the unit to the bottom of the unit, eliminating the need for an air duct at the rear of the chiller. The elimination of the air duct reduces the required depth of the chiller compartment by at least four inches, which represents a significant space savings over existing chiller units. The chiller preferably utilizes quick disconnect valves for the condenser cooling liquid inlet and the outlet, which in turn is coupled to the aircraft heat sink. A display is provided on the unit for controlling the temperature and other operations of the unit. 
         [0007]    The location of the chiller plays a role in both the galley foot print and weight reduction, as well as the efficient distribution of chilled air around the below work deck installed trolley or cart. 
         [0008]    Other features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments in conjunction with the accompanying drawings, which illustrate by way of example the operation of the invention 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a perspective view of an aircraft galley structure illustrating a possible location for the chiller of the present invention. 
           [0010]      FIG. 2  is an elevated, perspective view of the components of a first embodiment of the chiller of the present invention; and 
           [0011]      FIG. 3  is a perspective view of the elements of the chiller unit. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0012]      FIG. 1  illustrates a portion of an aircraft galley structural framework showing a position of the new chiller unit in relation to the beverage cart bays. The galley framework  100  includes a plurality of compartments above a work deck  110 , where the space above the work deck  110  is reserved for various food service equipment such as coffee brewers, refrigerators, food storage, utensil storage, and the like. Below the work deck  110  is a series of bays  120  for housing beverage carts (not shown) that the flight attendants push down the aircraft&#39;s aisle(s) to bring food and beverages to the passengers. The beverage carts are intended to be kept at a temperature that allows the beverages and perishables inside to be preserved and served at an acceptable temperature. To maintain the carts at the proper temperature, a chiller unit  140  is located in a designated peripheral compartment  150  with air passages above and below for directing and receiving air from the bays  120 . Each bay  120  includes openings  160  along the bottom edge where chilled air can pass through from adjacent bays or, in the case of the first bay, from the compartment  150 . Air flows in each bay as shown by arrows  170  around the bay, and back toward the peripheral compartment  150  as it warms. From the top of compartment  150 , the air is drawn back into the chiller  140  where it is cooled and recirculated. The compact nature of the chiller  140  and its vertical orientation allows the unit to be stored in a designated peripheral compartment  150  adjacent the bays  120 . Moreover, as explained below, the elimination of tubing at the rear surface of the chiller  140  reduces the necessary depth of the compartment  150  by at least four inches. 
         [0013]      FIGS. 2 and 3  illustrate a chiller unit  140  that is particularly suited for the galley of a commercial aircraft, as set forth below. The chiller  140  is formed within a housing  135  and includes the basics of a vapor cycle refrigeration system, including a compressor  180 , a heat exchanger  185 , a liquid cooled condenser  190 , and an evaporator  195 . Cooled “supply” air  220  is delivered by the evaporator  195  through the bottom opening  198  as part of the evaporation process, as ambient air  215  is drawn into the evaporator  195  by axial fans  200 . A liquid cooling system is employed circulating a refrigerant, such as polyethylene glycol water (“PGW”), which is passed through a liquid cooled condenser  190  and into a liquid reservoir  205  where it is collected. The PGW is then pumped via a liquid pump  210  to a heat exchanger  185 , where the fans  200  cools the PGW. The cooled PGW is then passed through a flow meter and back into the condenser  190  to cool the air from the compressor  180 . Warm air  215  enters through the top of the chiller  140 , and cooled air  220  exits the chiller through the bottom opening  198  where it is directed to the bays  120  below the galley work deck  110 . 
         [0014]      FIG. 3  further illustrates the path of the refrigerant and chilled air. Circulating refrigerant (e.g., PGW) enters the compressor  180  in the thermodynamic state known as a saturated vapor and is compressed to a higher pressure, resulting in a higher temperature as well. The hot, compressed vapor is then in the thermodynamic state known as a superheated vapor and it is at a temperature and pressure at which it can be condensed with either cooling water or cooling air. This hot vapor is routed through the condenser  190  where it is cooled and condensed into a liquid by flowing through a coil or tubes with cool water or cool air directed across the coil or tubes. This is where the circulating refrigerant rejects heat from the system and the rejected heat is carried away by the circulating air. The now-cooled condensed liquid refrigerant, in the thermodynamic state known as a saturated liquid, is next routed through an expansion valve where it undergoes an abrupt reduction in pressure. The pressure reduction results in the adiabatic flash evaporation of a part of the saturated liquid refrigerant. The auto-refrigeration effect of the adiabatic flash evaporation lowers the temperature of the liquid and vapor refrigerant mixture to where it is colder than the ambient temperature in the beverage cart compartments  120 . The cold liquid-vapor mixture is then routed through the coil or tubes in the evaporator  195 . The fans  200  draw in the warmer air  215  from the bays  120  across the coil or tubes carrying the cold refrigerant liquid and vapor mixture. That warm air  215  evaporates the liquid part of the cold refrigerant mixture. As a result, the circulating air  220  as it passes through the evaporator  195  is cooled, and this cooled air is forced out of the chiller along the bottom opening  198  where it is carried into the adjacent beverage cart compartments  120 . The evaporator  195  is where the circulating refrigerant absorbs and removes heat which is subsequently rejected in the condenser and transferred elsewhere by the air used in the condenser  190 . To complete the refrigeration cycle, the refrigerant vapor from the evaporator  195  in its now saturated-vapor state is routed back into the compressor  180 . 
         [0015]    The chiller  140  preferably includes two fluid quick disconnects at the rear of the housing  135 . The first disconnect  240  is coupled to a tubing  245  that delivers fluid from the CAX heat exchanger  185 , and the second disconnect  250  supplies fluid via tubing  255  to the CAX heat exchanger  185 . These quick disconnect valves  240 ,  250  are used to deliver cooling liquid to the condenser and carry heated fluid to an aircraft heat sink (not shown). 
         [0016]    The compact configuration of the chiller  140  makes it extremely suitable for aircraft utilization. The capacity to be stored in a small, adjacent compartment and provide chilled air to beverage trolley bays results in weight and energy savings, as well can saves space. In a preferred embodiment, the chiller unit  140  has a height of 31.5 inches with a trapezoidal profile including a base length of 8.7 inches and the opposite side having a length of 5.9 inches. The chiller has a depth of 34.3 inches in the preferred embodiment, allowing the chiller to fit inside a small compartment  150  adjacent the trolley bays  120 . Also, the chiller  140  takes the form of a galley line replaceable unit, or LRU, enabling the chiller to be quickly and easily removed and replaced without disassembling the galley architecture, leading to simpler maintenance and less downtime during repair or replacement. Because the chiller of the present invention does not utilize ducting on the side or rear wall, the footprint of the chiller is reduced and no ducting is needed to deliver the chilled air. Therefore, the chiller can fit in a smaller compartment while serving the same size and number of cart bays. 
         [0017]    The present invention serves to demonstrate an adjacent-the-bay, POU, chiller system for a beverage trolley bay of an aircraft galley. The system is effective at removal of condensate from the evaporator, and improves the overall heat transfer efficiency of the evaporator and the system in general.