Fuel conserving air-conditioning apparatus and method for aircraft

Abstract

An aircraft cabin air-conditioning system, of the type that uses engine bleed air, regulates the amount of tapped bleed air so as to be just sufficient to maintain a desired cabin pressure, thus minimizing the fuel burn allocated to the aircraft's environmental control system. The air-conditioning system cools the bleed air by passing it first through a heat exchanger 50 of a circulating glycol/water coolant loop 55 for heat transfer to a coolant and then through an evaporator 60 of an electrically-driven vapor-cycle loop 56 for supplemental heat transfer to a refrigerant. The rate at which the refrigerant is circulated through the evaporator 60 is regulated to be just sufficient to provide a required supplemental cooling capacity, thereby minimizing electrical power consumed by a compressor 63 that forms part of the vapor-cycle loop 56. A subbranch of the coolant loop 55 carries the coolant through a condenser 64 of the vapor-cycle loop 56 where there is an additional transfer of heat to the coolant. Bulk fuel in the aircraft fuel tanks as well as heat loss from the wing's lower and upper skin surfaces during flight are used as a heat sink for heat that has been transferred from the bleed air to the coolant, and for this purpose the coolant loop 55 circulates the fluid coolant through a fuel-cooled heat exchanger 59. To further conserve the volume of air that must be bled from the engine, used cabin air is filtered and recirculated through the evaporator 60 of the vapor-cycle loop 56 where it is recooled prior to being reintroduced into the cabin.

Dependencies are inferred from the claim text.