Transport refrigeration system having means for achieving and

Abstract

A transport refrigeration system of the type which holds a set point by operating in heating and cooling cycles. The system includes a compressor, a condenser and an evaporator each having inlet and outlet ports. A three-way valve receives compressed gas discharged from the compressor and directs it selectively to first and second outlets. First outlet of the three-way valve directs hot compressor gas to the condenser for operation of the system in a conventional cooling cycle. A hot gas conduit is provided which connects the second outlet of the three-way valve directly to the inlet of the evaporator. A branch line extends from the hot gas line to the line interconnecting the condenser and the evaporator, upstream of the receiver. Another refrigerant line extends from the outlet of the condenser to establish fluid communication with the line interconnecting the outlet of the evaporator with the compressor suction port. Appropriate valve means are provided in the refrigerant lines such that, when appropriately actuated, the three-way valve directs hot gas only to the receiver. The portion of the liquid line which is downstream of the receiver, the hot gas line, and the line interconnecting the condenser outlet with the compressor suction line all are placed in fluid communication with the suction side of the compressor. The compressor then serves to draw down this portion of the refrigeration system to a low pressure thereby withdrawing the refrigerant therefrom and directing it via three-way valve and a portion of the hot gas line to the receiver.