COMBINED OIL RETURN AND COMPRESSOR DISCHARGE TEMPERATURE LIMITATION REGARDING FLOODED ECONOMIZER HEAT EXCHANGER

摘要

A refrigeration system of the type having aneconomizer cycle is provided with a null cycle, in additionto heating and cooling cycles, without shutting a compres-sor prime mover down, to preserve air flow in a conditionedspace. First, second and third controllable valves respec-tively: (1) select main and auxiliary condensers, (2) openand close a liquid line, and (3) open and close a linewhich provides a warm liquid to an economizer heat exchang-er. The valves are controlled in at least one predeter-mined open/close pattern during a null cycle, and prefera-bly in a plurality of selectable predetermined open/closepatterns, to provide a null cycle at any instant which sub-stantially matches the net heat gain or loss taking placein the conditioned space. Thus, the temperature of theserved space will be more apt to remain in a null tempera-ture range close to set point, providing smoother and moreaccurate control over the temperature of the conditionedspace for longer shelf life of perishables stored therein.The system achieves the latter by controlling coolingcirculation in the compressor oil cooler.