Performance Evaluation of Decentralized Split Unit Air-to-air Heat Pumps

A holistic evaluation is performed to investigate the energy performance of air-to-air split units (also called air-conditioning units), including laboratory measurements and steady-state simulations of the refrigerant cycle. Several aspects are considered, such as indoor fan speed, varying compressor frequency, defrost and “on/off” cycles. The laboratory measurements include steady-state test points as well as dynamic operation.The measured Coefficient of Performance (COP) varies from 1.8 to 4.9, and the maximum measured heating capacity was 2.5 kW, close to the nominal value of 2.7 kW. The measured reduction due to the defrost cycle was up to 14% in the heating capacity and 16% in the COP. It was also found that the indoor air flows were on average 40% less than the ones listed in the datasheet.