18 May 2017
To investigate the effects of piping on the heating performance of the multi-split VRF system under part-load conditions, a steady-state model of the multi-split VRF system in heating mode has been developed with its refrigerant pipeline model validated by an experiment. Then, the model was utilized to study the effects of horizontal pipe length and the height difference between the outdoor unit and the indoor units on the heating performance under part-load conditions. The results showed that under the control strategy of constant discharge pressure, the lengthening of horizontal pipe will reduce the COP apparently as the pipe length increased even under part-load conditions. It was indicated that the height difference in range from -50 m to 50 m had low effect on the COP but it would affect the available pressure drop of EEV. In application of the developed model, more work has been expected for a comprehensive evaluation on the multi-split VRF systems in buildings in the future.