FREEZING PREVENTING CONTROL FOR ENGINE-DRIVEN HEAT PUMP

PURPOSE:To prevent breakage of a compressor because of a large quantity of refrigerants flowing to an indoor heat-exchanger in a short time by a method wherein a temperature change in a specified time is approximated using a linear formula on each occasion of measurement togetherwith a plurality of past temperatures in succession, and opening and closing of a bypass valve are controlled based on the degree of freezing, classified by a grade, of the indoor heat-exchanger. CONSTITUTION:The temperature of a refrigerant flowing in and out from an indoor heat- exchanger 84 is measured at intervals of a given time by means of sensors 5 and 6. Togetherwith a plurality of past temperatures in succession where an inflow temperature and an outflow temperature are measured in priority, a temperature change in a specified time is caused to approximate to a primary formula each time measurement is carried out. Based on a determined initial temperature and the magnitude of an average rate of change, the degree of freezing of the indoor heat-exchanger 84 is classified by a grade. Based on the degree of freezing, bypass valves 2 and 3 located between a refrigerant pipe 1 on the inlet side of an accumulator 88 and a refrigerant pipe 1 on the outlet side thereof are opened and closed. This constitution prevents the breakage of a compressor because of a large quantity of refrigerants flowing in the indoor heat-exchanger in a short time and a liquid refrigerant incapable of being entirely vaporized flowing to the compressor.