A comprehensive numerical study of the effects of the air distribution terminals on the performance of a novel VRF-SV hybrid system

Abstract

This study aims to numerically investigate the impact of air supply terminal devices (ASTDs) on the performance of novel variable refrigerant flow (VRF) integrated stratum ventilation (SV) system. The novel VRF-SV hybrid system was designed and analyzed in the authors’ previous work, where different design configurations were tested and their performances were compared. However, the effect of ASTDs on the performance of novel system has not yet been thoroughly explored. Therefore, this study was designed to investigate the effect of four types of ASTDs, including bar grille, double deflection grille, drum louver and jet slot diffusers installed in the laboratory and meeting room environments. The temperature and velocity field distribution, thermal comfort and indoor air quality (IAQ) were examined as performance indicators. The Re-Normalization Group (RNG), Realizable and Standard k-ϵ turbulence models were also employed in this study to verify and validate the numerical predictions with the experimental measurements. The experimental results found relatively close to the predictions obtained through RNG k-ϵ model with maximum deviations at any location were found to be 0.28 m/s in terms of velocity and 1.6°C in terms of temperature magnitude. Further research demonstrated that among the studied ASTDs, the bar grille diffuser provided an adequate thermal environment for the occupants with an acceptable jet throw and IAQ. This benefit also suggests that if the bar grille is installed with the VRF-SV system, the system would require less fan power, and thus, it reduces the energy use by the fan.