Method and apparatus for cooling an airline galley cart using a skin heat exchanger

A system for cooling a thermally insulated galley cart in an aircraft incorporates a skin heat exchanger configured to transfer heat to an aircraft skin. A cooling system is in communication with the skin heat exchanger and is configured to be removably coupled with a thermally insulated galley cart.

REFERENCE TO RELATED APPLICATIONS

This application is copending with application Ser. No. 14/267,188 filed on May 1, 2014 entitled Optimally Configured Air-Flow Galley Cart having a common assignee with the present invention, the disclosure of which is incorporated herein by reference.

BACKGROUND INFORMATION

Field

Embodiments of the disclosure relate generally to galley cart systems for transportation vehicles and, more particularly, to a system for providing cooled working fluid to insulated galley carts and freezer galley inserts with an ambient air skin heat exchanger on an aircraft having high cruising altitude and a simplified interface between the galley and the carts and inserts.

Background

Galley carts employed for food service in transportation vehicles, such as aircraft and trains, often require cooling to maintain food and beverages at a temperature that is cooler than a cabin of the vehicle. At least some known carts include or connect to an active refrigeration system (a chiller) that provides cool air to an interior volume of the cart to cool the food/beverages. However, the chiller is powered by the vehicle systems, reducing the amount of power available to the vehicle for propulsion, thrust, etc. As such, the chiller is an inefficient draw on the power supply system of the vehicle. Further, such a chiller system adds weight and complexity to the vehicle and may produce undesirable noise. Accordingly, some galley carts are configured to contain water ice or dry ice that cools the food/beverages as it melts or sublimates. Either of these cooling approaches requires the regular replacement of the cooling media, such as the water ice or dry ice. An additional drawback with the use of dry ice is the carbon dioxide gas (CO2) sublimate that is released. The Federal Aviation Administration has set forth requirements for the maximum CO2concentration in a cabin of the aircraft.

It is therefore desirable to provide improved and cost effective systems for providing cooling for galley carts and freezer galley inserts.

SUMMARY

Exemplary embodiments provide a system for cooling a thermally insulated galley cart in an aircraft. A skin heat exchanger is configured to transfer heat to an aircraft skin. A cooling system is in communication with the skin heat exchanger and is configured to be removably coupled with a thermally insulated galley cart.

The embodiments provide a method for maintaining temperature control of foodstuffs for use in an aircraft. The insulated galley cart is cooled with an internal heat sink during on ground or climb out operations. Aircraft altitude is monitored to determine when the aircraft reaches a critical altitude to provide external temperatures sufficient for cooling in a skin heat exchanger closed coolant loop. When critical altitude has been reached, a coolant pump is turned on. Blower locations in a semi closed air loop in communication with the closed coolant loop through a coolant to air heat exchanger are monitored to determine if an insulated galley cart is loaded into position at that location. If an ICC is loaded in or returned to the blower location, the blower at that position is turned on.

DETAILED DESCRIPTION

The embodiments described herein employ thermally insulated galley carts (IGC) and a heat exchanger system communicating with the exterior skin of an aircraft. The IGC may employ an internal heat sink keep its contents cool during portions of a flight when the skin heat exchanger is not effective, such as on the ground or during takeoff. Cooling of the cart on the airplane in flight is achieved by a cooling system having at least one loop and, in particular, a two or three loop cooling system. In such a multi-loop cooling system the first loop contains a liquid coolant that is pumped through a skin heat exchanger to release heat, and then pumped through coolant/air heat exchangers. The coolant/air heat exchangers cool cabin air as a working fluid that flows through the IGCs. The first heat exchanger in the loop receives the coolest fluid, and depending on cooling requirements, may be used by a galley insert in the form of a freezer, or a galley cart dedicated to frozen food storage. The cold coolant continues from the first heat exchanger and enters a second heat exchanger in-line with, and downstream from, the first heat exchanger. Air from the second heat exchanger is then blown through an IGC.

During low altitude phases of the flight and while on the ground, the foodstuffs in the IGC or freezer galley insert may be chilled by an internal heat sink, such as dry ice or water ice The use of the internal heat sink allows for the benefits of active refrigeration with a system that is more inexpensive and lighter weight than conventional galley/cart cooling systems. Because the system described herein uses heat exchangers and does not require an active refrigeration heat pump, the major consumer of power in a chiller, the power requirements are reduced. In addition, maintenance issues associated with the use of a heat pump are also eliminated. The embodiments disclosed may be used in conjunction with cold air distribution configurations in the IGCs as described in copending application Ser. No. 14/267,188 entitled “Optimally Configured Air-Flow Galley Cart” for enhanced efficiency.

Referring to the drawings,FIG. 1shows an exemplary system for cooling an IGC in an aircraft employing a skin heat exchanger configured to transfer heat to an aircraft skin and a cooling system in communication with the skin heat exchanger, wherein the cooling system is configured to be removably coupled with the IGC. A closed coolant loop10operates with a skin heat exchanger12to condition a working fluid coolant during flight at high altitudes where cold external temperatures outside the aircraft skin may be employed by the skin heat exchanger12as a cold sink. The closed coolant loop10provides coolant for conditioning of a semi-closed IGC air loop14and, in certain embodiments, a semi-closed freezer galley insert air loop16.

As shown in detail inFIG. 2, the closed coolant loop10employs the skin heat exchanger12in contact with the aircraft skin20with the external ambient air22convectively cooling the skin. A coolant pump24, is configured to circulate a non-freezing coolant, such as propylene glycol, as a primary working fluid through the skin heat exchanger18for cooling. Primary working fluid exiting the heat exchanger18flows through a bypass valve26and through an insulated coolant accumulator28, positioned intermediate the pump and the skin heat exchanger12, to a freezer-insert-coolant to air heat exchanger30aand an IGC coolant air heat exchanger30b. The primary working fluid then flows through the pump24for circulation back to the skin heat exchanger12. The insulated coolant accumulator28allows for thermal expansion and contraction of the coolant and maintains a reservoir of cold primary working fluid available for use at lower altitudes or in alternative operating scenarios as described in greater detail subsequently. Primary working fluid may be bypassed around the accumulator20at the bypass valve26sending warmer coolant (as ambient conditions allow) to the freezer insert and IGC coolant air heat exchangers30a,30bfor defrost cycles or other temperature control functions. Operation of the pump24and bypass valve26may be accomplished with a controller29receiving in input from the flight control system of the aircraft for aircraft altitude and inputs from flight crew for special operations as defined below.

As shown in detail inFIG. 3, the semi-closed IGC air loop14and semi-closed freezer galley insert air loop16are interconnected to the closed coolant loop10through the freezer insert and IGC coolant to air heat exchangers30aand30b. In a particular embodiment, the semi-closed freezer air loop16makes use of aircraft cabin air as a circulating secondary working fluid for temperature control of a freezer galley insert32. The air loop16is not a sealed system and air leakage is expected around the freezer galley insert32and in a galley hay34in which the insert32is housed. A blower36draws cabin air through the freezer insert coolant to air heat exchanger30aand delivers cooled air through the freezer galley insert32. Air exhausted from the freezer galley insert32is routed back to the freezer insert coolant to air heat exchanger30athrough a filter38.

The freezer insert coolant to air heat exchanger30aoperates in a primary mode to provide cooling to the freezer galley insert32using the coolant in the closed coolant loop10as the heat sink. As a secondary function, placement of the freezer insert coolant to air heat exchanger30aupstream of the IGC coolant to air heat exchanger30ballows heating of the coolant in the closed coolant loop10to acceptable temperatures for the ICC cooling, as will be described in detail subsequently. Operation with the coolant in the closed coolant loop10at a warm condition when the aircraft is not at altitude may be employed to defrost the freezer insert coolant heat exchanger30aand/or the freezer galley insert32. A heating element40may be employed in the freezer insert coolant to air heat exchanger30ato achieve desired temperatures for defrosting or otherwise controlling temperatures of the coolant as the primary working fluid or circulated cabin air as the secondary working fluid.

The semi-closed IGC air loop14operates similarly with aircraft cabin air as the circulating secondary working fluid for temperature control of a high performance IGC42. The air loop14is not a sealed system and air leakage is expected around the IGC42and in a galley bay44in which the IGC42is housed. A blower46draws cabin air through the IGC coolant to air heat exchanger30band delivers cooled air through the IGC42. Air exhausted from the IGC42is routed back to the IGC coolant to air heat exchanger30bthrough a filter48.

The cooling capability of the IGC coolant to air heat exchanger30bin the semi-closed IGC air loop14may be employed for multiple IGCs in the galley as shown inFIG. 4, wherein multiple blowers46a,46band46care connected by a manifold50to provide cooling airflow through associated IGCs42a,42band42c. Each IGC42may be equipped with a proximity sensor52s,52b,52cproviding an output to the controller29that, in turn, provides a control input to activate an associated blower46a,46bor46cwhen the associated IGC42a,42b,42cis placed into a location in the galley bay44adjacent the associated blower in that location. Individual connections from the controller29to the proximity sensors52aand52band blowers46aand46bare not shown inFIG. 4for simplicity. Alternatively, a blower46may be manually activated or deactivated using a power switch or circuit breaker54a,54b,54cto preclude cold air from issuing from a blower without an IGC interconnected. A similar manifold arrangement with multiple blowers may be employed for the freezer insert coolant to air heat exchanger30ain the semi-closed freezer galley insert air loop16.

FIG. 5Ais an isometric view of the IGC42, which may be employed in the embodiments disclosed herein. In one aspect of this embodiment, the IGC42includes a housing102. In the illustrated embodiment, the housing102has a first side104, a second side106, a top108, and a bottom110. The IGC42further includes a first door112positioned on one end of the housing102. The door112can further include one or more hinges114and a latch116. The hinges114pivotally attach the doors112to the housing102. The latch116can be configured to releasably engage corresponding receivers118attached to the housing102when the door112is in a closed position as illustrated inFIG. 5A. As shown inFIG. 5B, the IGC42employs a inlet port120and an outlet port122in a rear wall113each having flow operated valves as will be describe in greater detail subsequently. Dry ice or water ice compartments may be provided within the IGC42for passive cooling of the IGC42during transit to and from the aircraft or during use in the aircraft when disengaged from the galley bay44(shown inFIG. 3).

Employing an architecture for cabin air as the secondary working fluid, which is not required to be completely sealed, provides a simplification in the overall structure of the galley and IGCs. As shown inFIGS. 6A and 6B, a supply duct60, into which the blower46provides airflow, introduces cold air to the IGC42through an inlet valve62. An exhaust duct64allows air to be exhausted from the IGC42through an exhaust valve66. A simple supply opening72of, for example, approximately 2 inch (5.1 cm) diameter and an exhaust opening74of comparable size allow flow out of the supply duct60and into the exhaust duct64without using valves or dampers. The supply duct60and exhaust duct64may be constructed by interconnecting multiple panels or by removing core material68from a composite panel70to create voids for the channels with simple holes for the supply and exhaust openings. With the associated blower turned off, essentially no flow is present in the supply duct or exhaust duct.

The inlet valve62and exhaust valve66provide automatic actuation for opening when engaged to the supply duct60and exhaust duct64in the galley and for closing when disengaged. The valves62,66may be simple flow actuated valves devices opened by flow pressure created by the blower46. As shown inFIG. 7A, an inlet valve plate76is received in a relief78in the rear wall113of the IGC42. The valve plate76covers an inlet aperture80. In a particular embodiment, the inlet valve plate76is a magnetic material and is attracted to a magnetic element82positioned circumferentially around the inlet aperture80. Guide rails84terminating in retention clips86allow reciprocation of the valve plate76to an open position as shown inFIG. 7Bwhen activation of the blower46creates airflow in the inlet duct60and through supply opening72as represented by arrow88. A compliant seal89may be employed between the rear wall113of the IGC42and the galley wall composite70to create at least a partial seal around the inlet aperture80. For an exemplary embodiment, three guide rails with retention clips are employed for the inlet valve62as shown inFIG. 7C.

Air pressure in the IGC42created by the inflow of air through the inlet valve62operates on the exhaust valve66as shown inFIGS. 7D and 7E. An exhaust valve plate90is received in a relief92in the rear wall113of the IGC42. The valve plate covers an exhaust aperture94in the closed position as shown inFIG. 7D. In a particular embodiment, the exhaust valve plate90is a magnetic material and is attracted to a magnetic element96positioned circumferentially around the exhaust aperture94. Guide rails84terminating in retention clips86allow reciprocation of the exhaust valve plate90to an open position as shown inFIG. 7Ewhen activation of the blower46creates airflow in the inlet duct60and through supply opening72resulting in internal pressure in the IGC as represented by arrow98. For an exemplary embodiment, three guide rails with retention clips are employed for the exhaust valve66as shown inFIG. 7C. As with the inlet valve, a compliant seal89may be employed around the exhaust aperture94to provide at least a partial seal around the opening.

Alternative valve structures providing automatic opening and closing when engaged to the supply duct60or exhaust duct64, or upon activation of the blower46may be employed. An alternative valve arrangement is shown inFIGS. 7F and 7Gwherein the inlet valve plate76′ incorporates one or more magnets77. The magnetic element82of the valve structure ofFIGS. 7A-7Cis removed and replaced with magnetic elements82′ embedded in the core material68surrounding the supply opening72or suspended in the supply opening72by struts83. Polarity of the magnetic elements82′ and the magnets77in the valve plate76′ are opposite to provide a repulsion force urging the valve plate76′ open upon engaging the IGC42against the supply opening72as shown inFIG. 7F. Guide rails84′ and retention clips86′ constrain the motion of the valve plate76′ as in the prior embodiment. Upon removal of the IGC42from the galley, a spring87urges the valve plate76′ into a closed position as shown inFIG. 7G. For an exhaust valve, a reversal of the orientation of the valve plate76′ and associated guide rails, retention clips and spring may be employed with the polarity of the magnetic elements82′ surrounding the exhaust opening74and the magnets77in the valve plate76′ aligned for attraction to urge the valve plate76′ open.

The embodiments disclosed provide a simplified cooling system for galley supply components such as IGCs and freezer galley inserts and their operation. As shown inFIGS. 8A and 8B, an IGC, such as IGC42, may be retained on the ground in a catering facility cold soak room that is cooled by active refrigeration until ready to be loaded on the aircraft, step802. A catering truck may then be employed to transport the IGC to the aircraft with cooling in the IGC supplied by an internal heat sink, such as dry ice or water ice, step804, with or without supplemental active refrigeration in the truck. Once loaded in the aircraft, during on-ground or climb-out operations, except as described subsequently, the IGC remains initially cooled by the internal heat sink, step806.

Similarly, if freezer galley inserts, such as insert32, are employed, the freezer galley insert is cooled by active refrigeration in a catering facility freezer room until ready to be loaded on the aircraft, step808. A catering truck may then be employed to transport the freezer galley insert to the aircraft with cooling in the freezer galley insert supplied by an internal heat sink, such as dry ice, step810, with or without supplemental active refrigeration in the truck. Once loaded in the aircraft, during on-ground or climb-out operations, the freezer galley insert remains cooled by the internal heat sink, step812.

Upon powering up of the aircraft, power is applied to the skin heat exchanger and galley bay, step814. Aircraft status is monitored with a system controller to determine if the aircraft has reached or remains above a critical altitude to provide external temperatures sufficient for cooling in the skin heat exchanger closed coolant loop, step816. As such, the system controller determines if the aircraft is at least at the critical altitude. If the aircraft is not at or above the critical altitude, the coolant pump, such as pump24, is deactivated, step818. If the critical altitude has been reached, the coolant pump is activated, step820. Each blower location in the semi-closed freezer galley insert air loop and semi-closed IGC air loop is then monitored to determine if an IGC or freezer galley insert is loaded into position at that location, step822. If not, the blower at that IGC or freezer galley insert position is turned off, step824. If an IGC or freezer galley insert is loaded in or returned to the blower location, the blower at that position is turned on, step826. In special operations as determined by the system controller, for temperature control a bypass valve may be activated to bypass a coolant accumulator, step828. A heating element in a coolant to air heat exchanger in the semi-closed freezer galley insert air loop may be activated to further control coolant temperature, step830. With appropriate environmental conditions when the aircraft is below the critical altitude, the coolant pump may be operated to defrost the coolant air heat exchanger in the semi-closed air loop, step832. In alternative operating scenarios, stored coolant in the accumulator may also be used to cool carts during the climb out or descent by selectively turning on the coolant pump, step834, when the aircraft has not reached or does not remain above the critical altitude. Also during thru-catered situations (the round-trip flight is catered from one location and the food for both the outbound and return flight are loaded at once), stored coolant in the accumulator may be used to cool carts while on the ground, step836.

Having now described various embodiments of the invention in detail as required by the patent statutes, those skilled in the art will recognize modifications and substitutions to the specific embodiments disclosed herein. Such modifications are within the scope and intent of the present invention as defined in the following claims.