Aircraft air chiller with reduced profile

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.

BACKGROUND

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 beverages 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.

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 vapor 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.

The second type of cooling system utilizes the same conventional refrigerant vapor compression and expansion technology, but the cooling medium is a chilled liquid rather than a air. 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.

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

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 refrigerant vapor compression 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.

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.

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

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1illustrates 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 framework100includes a plurality of compartments above a work deck110, where the space above the work deck110is reserved for various food service equipment such as coffee brewers, refrigerators, food storage, utensil storage, and the like. Below the work deck110is a series of bays120for housing beverage carts (not shown) that the flight attendants push down the aircraft'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 unit140is located in a designated peripheral compartment150with air passages above and below for directing and receiving air from the bays120. Each bay120includes openings160along the bottom edge where chilled air can pass through from adjacent bays or, in the case of the first bay, from the compartment150. Air flows in each bay as shown by arrows170around the bay, and back toward the peripheral compartment150as it warms. From the top of compartment150, the air is drawn back into the chiller140where it is cooled and recirculated. The compact nature of the chiller140and its vertical orientation allows the unit to be stored in a designated peripheral compartment150adjacent the bays120. Moreover, as explained below, the elimination of tubing at the rear surface of the chiller140reduces the necessary depth of the compartment150by at least four inches.

FIGS. 2 and 3illustrate a chiller unit140that is particularly suited for the galley of a commercial aircraft, as set forth below. The chiller140is formed within a housing135and includes the basics of a vapor cycle refrigeration system, including a compressor180, a heat exchanger185, a liquid cooled condenser190, and an evaporator195. Warm air215enters through the top of the chiller140, and cooled air220exits the chiller through the bottom opening198where it is directed to the bays120below the galley work deck110. Circulating air215is delivered by the axial fan200through the evaporator195and bottom opening198as part of the air cooling process. A liquid cooling system for liquid-cooled condenser is employed circulating a coolant, such as propylene glycol water (“PGW”), which is passed through a liquid cooled condenser190and into a liquid reservoir205where it is collected. The PGW is then pumped by a liquid pump210via fluid quick disconnect250to a heat sink in the aircraft, where the PGW was cooled by cooling medium (air or liquid). The cooled PGW is then passed through another fluid quick disconnect240flow back into the condenser190to cool the superheated vapor of the refrigerant from the compressor180.

FIGS. 3 and 4further illustrates the path of the refrigerant and chilled air. Circulating refrigerant (e.g., R134a, R1234yf, or other refrigerants) enters the compressor180in the thermodynamic state known as a low pressure superheated 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 with higher pressure and temperature, and it is at a temperature and pressure at which it can be condensed with either cooling liquid or cooling air. This hot vapor is routed through the condenser190where it is cooled and condensed into a liquid by flowing through a coil or tubes with cool liquid or cool air directed across outside 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 liquid or air. The now-cooled condensed liquid refrigerant, in the thermodynamic state known as saturated, passes through a service block182containing a sight glass (not shown) and a filter/drier assembly (not shown). The refrigerant then passes through a refrigerant heat exchanger185for sub-cooling, in which heat is exchanged between the refrigerant liquid passing from the service block182to the expansion valve189and the refrigerant vapor passing from the evaporator195to the compressor180. In particular, the refrigerant heat exchanger185performs a refrigerant liquid sub-cooling and refrigerant vapor superheating process by which the liquid refrigerant passing from the service block182to the expansion valve189via the refrigerant heat exchanger185transfers heat to the vapor refrigerant passing from the evaporator195to the compressor180. By superheating the refrigerant before entering the compressor180, refrigerant liquid droplets may be prevented from entering the compressor180.

The refrigerant is next routed through an expansion valve189where it undergoes an abrupt reduction in pressure. The pressure reduction results in the adiabatic flash evaporation of a part of the 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 galley beverage cart compartments120. The cold liquid-vapor mixture is then routed through the coil or tubes in the evaporator195. The fans200draw in the warmer air215from the galley compartment across the coil or tubes carrying the cold refrigerant liquid and vapor mixture with lower pressure. That warm air215evaporates the liquid part of the cold refrigerant mixture. As a result, the circulating air215as it passes through the evaporator195is cooled, and this cooled air is forced out of the chiller along the bottom opening198where it is carried into the adjacent beverage cart compartments120. The evaporator195is where the circulating refrigerant absorbs and removes heat which is subsequently rejected in the condenser and transferred elsewhere by the liquid or air used in the condenser190. The expansion valve189may also be coupled with a thermal expansion remote bulb192. The remote bulb192may be coupled with the expansion valve189by a capillary tube that communicates a working gas between the expansion valve189and the remote bulb192for sensing a temperature of the refrigerant leaving the evaporator195. Thus, the expansion valve189may serve as a thermostatic expansion valve and operate to control a flow of refrigerant into the evaporator195according to the temperature of the refrigerant leaving the evaporator195. After the cold liquid/vapor mixture exits the expansion valve189, the refrigerant moves through the refrigerant tubing and enters the evaporator195.

To complete the refrigeration cycle, the refrigerant vapor from the evaporator195in its now saturated-vapor state is routed back into the compressor180through heat exchanger185.

The chiller140preferably includes two fluid quick disconnects (QD) at the rear of the housing135. The first disconnect250is coupled to a tubing255that delivers fluid to the aircraft heat sink from the chiller140, and the second disconnect240supplies fluid via tubing245from the aircraft heat sink to the chiller140. These quick disconnect valves240and250are used to deliver cooling liquid to the condenser and carry heated fluid to the aircraft heat sink.

The compact configuration of the chiller140makes 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 as space. In a preferred embodiment, the chiller unit140has 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 compartment150adjacent the trolley bays120. Also, the chiller140takes 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.

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.