Abstract: In order to reveal some relationships between system parameters and R407C incomplete phase changing in condenser and evaporator, a concept is presented firstly, that is the maximum flow rate of heat-transfer fluids. Afterwards thermodynamics cycle analyzing is used, and some important system parameters are given, such as temperature difference between R407C and heat-transfer fluids, compressor discharge capacity. These parameters can affect on the maximum flow rate of heat-transfer fluids, and the results are shown in some figures. Lastly, relationship is discussed too between R407C’s pressure drop in condenser or evaporator and the incomplete phase change.