22 May 2008


Variable speed compressor is one of the most promising ways to modulate the capacity of heat pump units. The paper describes some common obstacles in the evaluation of variable speed heat pump systems. The inconsistencies between the compared system components, the complexity in the measurement of some detailed parameters, too much focus on unit efficiency solely, but also not considering the effect of system dynamics are some of the mentioned problems. Dynamic modelling and simulation of a heat pump system taking all system components into consideration and validation of the model based on experiments are suggested as the solution. This paper describes a parameter estimation approach to variable speed heat pump unit modelling that requires a relatively low demand of measured input data. The outputs of the model are a number of parameters such as total isentropic efficiency of compressor as a function of frequency, superheat temperature and sub-cooling temperature, etc. Making use of the model provides the opportunity to evaluate the dynamics of the whole system including building and heat source in TRNSYS.