| 摘要 |
A system for controlling operation of a refrigerating device, which system comprises: a refrigerant circuit (9), in which a compressor (1), a condenser (6), a receiver (4), a pressure-reducing valve (5) and an evaporator (3) are connected to one another; and a cycle change-over mechanism (2) for changing over a refrigeration cycle of the refrigerant circuit (9) between the forward operation and the reverse operation; a refrigerating device, in which the pressure-reducing valve (5) is disposed on the downstream side of the receiver (4) during either one of the refrigerating cycles, is of an accumulatorless structure, and liquid back-flow to the compressor at the time of a cycle change-over is prevented. The top portion of the receiver (4) is connected to a liquid line on the downstream side of the pressure-reducing valve (5) through a bypass path (4a), and an on-off valve (SV) is provided in this bypass path (4a). The on-off valve (SV) is controlled to be opened for a predetermined time before the cycle is switched to a reverse cycle defrost operation. With this arrangement, a liquid refrigerant is recovered by the receiver (4) to prevent liquid back-flow. The on-off valve (SV) of the bypass path (4a) is opened from the time, at which defrost progresses to a certain extent, to the completion of defrost during the reverse cycle defrost operation. With this arrangement, an excessive reduction of the low pressure and the liquid back-flow are prevented. After an electric expansion valve (5) as being the pressure-reducing valve and the on-off valve (SV) are closed for a predetermined time upon completion of the defrost, the electric expansion valve (5) is openend to a small degree and the on-off valve (SV) is opened for a predetermined time. With this arrangement, the rise of the high pressure is controlled and the liquid back-flow is prevented. |
