Abstract:
Embodiments of the present invention relate generally to improved cooling systems and methods for use on aircraft trolleys and compartments. The systems use absorptive cooling with thermal conductive plates strategically positioned in order to keep trolleys and their contents cooled.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 61/712,368, filed Oct. 11, 2012, titled “Absorption Cooling Used on Galley&#39;s Trolley Compartment,” and U.S. Provisional Application Ser. No. 61/712,370, filed Oct. 11, 2012, titled “Absorption Cooling Used on Trolley Cooling,” the entire contents of each of which are hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    Embodiments of the present invention relate generally to improved cooling systems and methods for use on aircraft trolleys and compartments. 
       BACKGROUND 
       [0003]    Aircraft trolleys are used to chill and maintain the temperature of food and various other items that are to be served on-board an aircraft. The trolleys are generally chilled via an airflow from an air chiller or compressor that is directed over the items in the trolley. In many instances, the trolley has an opening in the back that can be aligned with a cool air blower that causes air to flow into the trolley and around the food and beverage items contained therein. This configuration can make it difficult to move and interchange the trolleys. Improvements to these cooling systems would be beneficial. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  shows a side cross-sectional view of a trolley cooling system. 
           [0005]      FIG. 2  shows a side cross-section view of an alternate trolley cooling system. 
           [0006]      FIG. 3  shows a schematic of the trolley cooling systems of  FIGS. 1 and 2 . 
           [0007]      FIG. 4  shows a top plan view of an alternate trolley cooling system. 
           [0008]      FIG. 5  shows a schematic of the trolley cooling system of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    Absorption cooling uses a heat source to drive the cooling system. For example, an absorption refrigerator is a refrigerator that uses a heat source (such as a solar source, a kerosene-fueled flame, or waste heat from factories) to provide the energy needed to drive the cooling system. In the early part of the twentieth century, the vapor absorption cycle using water-ammonia systems was widely used, but upon development of the vapor compression cycle, it lost much of its use. Absorption cooling technology has not been used for air conditioning or chilling inside aircraft. 
         [0010]    The present inventors have determined that if an appropriate heat source could be provided, the use of absorption cooling on-board aircraft or other vehicles could be a viable alternative to the cooling that is provided by air chillers or compressors in order to recycle the heat and to reduce noise from the traditional cooling systems. Replacing an electric air chiller with an absorption cooler can also reduce electricity loads. Embodiments of the present invention thus provide absorption cooling systems for trolleys and other containers in aircraft or other vehicle galleys. In a specific embodiment, the waste heat used to power the cooling system is provided from a fuel cell, which produces heat as one its by-products. Fuel cell technology has been contemplated by the current assignee and its related companies for powering more and more aircraft systems, particularly various galley (and lavatory) systems, because it is a clean and efficient power source. However, the primary way to make fuel cell technology efficient is by using the fuel cell by-products (water, heat, and oxygen depleted air) in addition to the energy created that is created by the fuel cell. One way to use the heat created is by delivering the heat to an absorptive cooling system. It should be understood that the heat may be provided from other aircraft systems, such as waste heat from one or more of the on-board ovens, from the aircraft engines, from the water system, or any other appropriate source. 
         [0011]    In one embodiment, there is provided a system  10  for absorptive cooling an aircraft trolley  12  or other compartment for use on board a passenger transport vehicle. As shown in  FIG. 1 , a thermal conductive plate  14  is positioned on the back  16  of the trolley  12 , and another thermal conductive plate  18  is positioned on the back of the galley trolley bay  20  (the space into which the trolley  12  is stored) for thermal connection. A fan  22  may be provided inside the trolley in order to generate air distribution through the trolley and over the items contained therein. This is an example of an “air over trolley.” The thermal plates transfer the cold temperature that is generated by the absorption cooler to the trolley interior. Contact between the plates  14 ,  18  creates a thermal connection for a cooling exchange between the plates. The thermal plates  14 ,  18  are mounted in such a way that they fully contact (or can otherwise be adjusted to fully contact) or substantially fully contact the other thermal plate to have maximum heat (cold) transfer. The transfer is conducted via thermal conductivity in the plates. 
         [0012]      FIG. 1  also illustrates that a heat source  24  is positioned behind the monument back wall  20  and associated with the absorption cooling system  10 . Waste heat from the heat source  24  is used to power the absorption cooling system  10 . In a specific embodiment, the heat generated may be a by-product from a fuel cell used to power one or more aircraft systems. 
         [0013]    A cooling fluid circuit  26  is also provided behind the back wall of the trolley bay  20 . The coolant circuit  26  is associated with the thermal plate  18  of the back wall, as well as with the absorption cooling unit. As waste heat (with a temperature generally between about 50-90 ° C., and in some instances, between 60-80° C.) is transformed by the absorption cooler, the coolant circuit  26  delivers the cooled fluid to the thermal plate  18 . Its contact with the thermal plate  14  of the trolley transfers the cold to the trolley  12 . Fan  22  helps recirculate cooled air inside the trolley  12 . Although the Figures show a single trolley being interfaced with a single galley wall, it should be understood that the coolant circuit  26  may route cooled fluid to any number of galley bay locations such that multiple trolleys may be cooled at a time. 
         [0014]    An adjustment system may be provided to ensure contact between the plates  14  and  18 . Because the trolley has clearance and is moveable, an adjustment system may assure correct alignment of trolley to allow contact between the plates. 
         [0015]      FIG. 2  shows an embodiment with a duct  28  that has a fan  29  for air distribution or recirculation through the trolley  12 . Current installations also have ducting that may be connected to the air-chiller, which contains the cooling parts and a fan to recirculate the air through the ducting and the trolley (referred to as an “air through trolley”). It is desirable to use standard trolleys in connection with this disclosure. In this instance, the trolleys are provided with thermal conductivity via plate  14 , such that there is no need for electricity for the internal fan  22  as shown in  FIG. 1 . In this embodiment, there are holes present on the back of the trolley, through will cold air may be forced into and through the trolley. As the trolley is being cooled on the inside by means of the plate  14 , the fan can recirculate the air, creating a more steady atmosphere for the food/drinks inside the trolley. This is an example of an “air through trolley.” 
         [0016]    The schematic of  FIG. 3  shows how waste heat is delivered to an absorption cooler that uses the heat to drive the cooling system. The cooled fluid may take a first path and be delivered to a compartment to be chilled, as necessary. It may also be delivered to the fluid coolant circuit to cool a galley wall thermal plate  18 . The coolant circuit  26  may use any appropriate cooling fluid (such as refrigeration fluid, cooled air, cooled water, or any other fluid). In addition, any other form of heat/cold transportation can be used to deliver cooling fluid between the plates. Non-limiting examples include the thermal conductivity described, the use of heating pipes in contact, cooled air generation, and so forth. 
         [0017]    As discussed, in one aspect, thermal plate  18  on the monument aligns with a thermal plate  14  that is mounted on the back of the trolley to generate the desired cooling effect. This system uses less power than an air chiller, it uses waste heat and thus improves efficiency, it provides cooling directly in the area where it is needed, and it provides a modular principle that can be used with each trolley inside the trolley bay. 
         [0018]    Another embodiment that uses absorptive cooling technology for chilling trolleys is shown in  FIGS. 4 and 5 . This concept provides an envelope of cooled air around the trolley, rather than using a thermal plate directly positioned on the trolley. As shown in  FIG. 4 , the trolley cooling system includes thermal cooling plates  30  on the galley stowage area, and they may be included on the top (the view of  FIG. 4  shows a top view so the top plate is not shown), back wall  36 , as well as on the divider wall panels  38  between trolley storage areas. The cooling fluid from the absorption cooler may be pumped through these plates  30 , much like how the cooling fluid circuit cools the monument plate  18  described above. Providing a plate  30  on the divider wall panel  38  allows the sides of two trolley carts  12  to be cooled with a single plate. This adds to efficiency of the system as the heat (cold) transfer happens on both sides. This creates a cooled or refrigerated area into which the trolley can be positioned. A door or other cooled air containment feature may be added to the front of the trolley bay stowage area, but is not necessary as cooled air is generally desirable in the aircraft galley and cabin areas. 
         [0019]    The trolleys may include internal fans (as discussed above) to help move and recirculate cooled air through and over the items in the trolley to improve cooling efficiency and to create an even temperature range. External fans  40  may also be mounted to the back of the galley stowage space and are provided in order to circulate air over the trolley(s) to support the natural recirculation of air and to keep the temperature even in the trolley bay. 
         [0020]    These embodiments can alleviate the need for a duct pipe that is typically provided at the back of the monument to deliver chiller air from the air chiller to the trolley. Providing even slight space gains can translate to major costs savings for the airline, as a few inches of space saved can mean additional passenger seats that can be added to the aircraft. One of the other benefits of the above-described solutions is that they do not require modifications to current trolley designs or sizes, nor to the current catering processes. They also reduce electricity loads on the aircraft by providing cooled air using waste heat from fuel cells or other sources. 
         [0021]    Changes and modifications, additions and deletions may be made to the structures and methods recited above and shown in the drawings without departing from the scope or spirit of the invention and the following claims.