In-situ method for air-to-air heat pump seasonal performance determination including steady-state and dynamic operations

Abstract There is no reliable in situ measurement method of air-to-air heat pump seasonal heating performances. Several methods were previously developed but they were only validated in steady-state conditions. In real life, dynamic sequences such as defrost cycle and starting phases occur, which are not considered in these methods. The goal of this work is to complete one of the existing methods so that it can address both steady-state and dynamic phases. The compressor energy balance method is used here: in the standard heating phase, refrigerant fluid measurements determine the refrigerant flow rate by using the compressor thermal balance. Modelling hypothesis are formulated regarding performance evaluation during defrost and start-up sequences. An algorithm is developed in order to identify the operating mode (standard heating phase, stop, start-up, defrost). Default parameters for this algorithm are proposed. The developed method is assessed over a long term test by comparison with a reference method based on intrusive measurement on the refrigerant. The integrated heat pump performance measured with the in-situ method is within 1 % of the reference measurement. Although large errors may occur in dynamic phases, their occurrence is low and some errors may compensate between the different phases. Leads on further work needed to bring this method closer to deployment are discussed. Better knowledge of the occurrence of the different operating modes is required. Further adaptation is also required for heat pumps using liquid injection at compressor suction.