SYSTEM FOR CONTROLLING FLOW OF WORKING FLUIDS

摘要

A mass flow control apparatus and method for use in combination with a heat transfer system (10) having a compressor (16), condenser (18), expansion valve (22), evaporator (14) and working fluid (12) in a fluid circuit. The mass flow is controlled using a quality sensor (150) for the working fluid exiting the evaporator (14), and a high side pressure sensor (50). A control circuit (60, 160) is provided that monitors the quality sensor (150) and the high side pressure sensor (50), and controls operations of the compressor (16), condenser fan (20) and valve (22) in response thereto. A flow reduction mode is used to reduce high side pressure at the valve inlet without excessive compressor cycling by changing the quality sensor set point when the high side pressure exceeds the condenser fan turn-on pressure but is less than the compressor disengage pressure.