In this study

simulation and experimental testing were carried out in a 28 kW variable refrigerant flow system to evaluate the contributions to annual performance factor (APF) from key factors

including heat exchanger area

compressor efficiency

refrigerant charge

system pressure loss

and oil return system. The APF values obtained experimentally and numerically are 4.59 and 4.61

respectively. Meanwhile

the maximum deviation between simulation and experiment is 5.1% at a single test condition

and the deviation of the APF is 0.5%. The results show that for the experimental system

the improvement in a single factor has a limited effect on the APF. For example

if the compressor efficiency increases by 3%

the APF increases by 2.8%. The optimization of the oil return system leads to an approximately 5% increase in the APF. A 10% increase in KA of the heat exchanger results in a 1% improvement of the APF. Therefore

many factors must be considered simultaneously to improve the APF.