Abstract: VRF system, because of its flexible control and high efficiency, is widely used in office and residential buildings with "part time, part space" requirement. However, in winter intermittent heating mode, after starting VRF system, although only some rooms need to be heated, each room still needs to go through a long time to reach setting temperature. This process would also affect the thermal comfort of the room. A VRF system of a residential building in Nanjing is taken as an example to establish a performance model of startup process of the VRF system. The feasibility of rapid heating is analyzed through the TRNSYS-TRNBUILD simulation platform, the VRF system performance and indoor comfort improvement effects under this scenario are analyzed. The results show that: in the rapid heating mode, the advantage of wide range of VRF capacity adjustment can be used for heat scheduling. The rapid heating of local room can be realized. Compared with the conventional heating start-up mode, the adoption of rapid heating mode will improve the system energy efficiency COP and indoor comfort.

Key words: VRF system, Intermittent heating, Rapid heating, PPD, COP, Air conditioner