Comparative analysis of cooling energy performance between water-cooled VRF and conventional AHU systems in a commercial building

Abstract

With recent efforts to minimize the energy consumption of heating, ventilation and air conditioning (HVAC) systems in buildings, the variable refrigerant flow heat pump (VRF-HP) system has drawn much attention, replacing the conventional HVAC system in the market. The VRF-HP system has several advantages, such as enhancing the aesthetics of buildings, reducing installation costs and offering high technology products. Although various studies relevant to VRF-HP systems are currently in progress, the evaluation of quantitative energy based on the actual performance information of such systems is still insufficient because it is difficult to accurately reflect various factors affecting their inherent heating and cooling performance in a simulation environment during the design stage. To obtain reliable results for this study, a water-cooled VRF-HP system equipped with a direct expansion air handling unit (DX-AHU) was selected from among various types of VRF-HP systems, and a standardized heating and cooling performance curve in diverse temperatures and part-load conditions based on the heating and cooling field measurement catalog performance data was developed. This paper aims to conduct a comparative assessment of the cooling energy performance between a water-cooled VRF-HP system and a chiller based conventional AHU system through co-simulation between EnergyPlus, MATLAB, and BCVTB after an extensive validation and calibration process. The results indicate that the water-cooled VRF-HP system can reduce cooling energy by up to 15% compared with the chiller based conventional AHU system.