Calculating Energy Efficiency Index of VRF System by Supply-Air Temperature Estimation

Variable Refrigerant Flow (VRF) Systems, which are a type of air-conditioning system, are used throughout the world. For post-installation evaluation of the efficiency of VRF controls for energy saving, an energy efficiency index, such as the Coefficient of Performance (COP), is needed. In order to calculate COP, it is necessary to grasp the amount of heat from the air-conditioning system to the rooms. When calculating heat quantity by using the air enthalpy method, although most of the necessary data are obtainable from a Building Energy Management System (BEMS), supply-air temperature is not always measured. This paper presents a supply-air temperature estimation model by regression analysis using field data. We also show evaluation results of calculation of COP for which the estimated data are used. Using other data collected from a BEMS, we found that the estimation error of the proposed methods was approximately 4% to 10%. The characteristics of COP using estimated data roughly correspond to those of COP using actual data.