Operation characteristics based on a novel performance model based on capacity utilization rate of a variable refrigerant flow air conditioning system.

• To reflect the impact of indoor units on system performance, a novel index and model were proposed. • Simulation and experimental results validated the proposed performance model. • Proposed index was applied in a field test in an office and a residential building. In the context of a large market share, enhancing the actual performance of variable refrigerant flow (VRF) air-conditioning systems is of considerable importance. The operating states of indoor units (IUs) significantly influence the energy efficiency of a VRF system with multiple indoor terminals. Therefore, it is challenging to address accurate and concise representation of the operational characteristics of IUs for analyzing their impact on system performance. This study explored a novel performance index called capacity utilization rate (CUR) to illustrate the effect of IUs on system performance and developed a performance model based on this index. Simulation and experimental results demonstrated that energy efficiency and evaporating temperature decrease with a reduction in CUR under specific ambient temperatures and part-load rates. The proposed performance model was applied to real buildings in field tests to examine the operational characteristics of the VRF system. This research offers valuable insights for system design, performance simulation, and performance evaluation of VRF systems. [ABSTRACT FROM AUTHOR]