Experimental study on steady state heating performance of a multi-type heat pump system for finding the optimum control variable

This paper describes the steady state heating performance of a multi-type heat pump system. The operation range of such systems has extended to cover various situations, and there is a requirement for systems that provide sufficient performance in those situations. Thus, many researchers have made efforts to design a controller or develop control logic that ensures optimal operation. In a multi-type heat pump, effective control of individual indoor units is necessary for satisfying heating or cooling demands. In such systems, a successfully designed controller must consider cross-coupling effects among indoor units during alteration of control variables such as expansion valve opening and compressor speed. Thus, we investigated cross-coupling effects among indoor units under various working conditions to help determine an optimum and effective control variable. The heating performance and the relationship among the operating variables of the multi-type heat pump system with R410A indicated that the temperature of the indoor units' secondary fluid was a suitable control variable.