Experimental and computational investigation of wall-mounted displacement induction ventilation system

Abstract

Traditional displacement ventilation (DV) creates high indoor air quality in occupied zone in cooling season due to thermal plume created by heat sources which then effectively purge contaminants out of the breathing zone, but tend to be challenged when high cooling loads are present. In addition, traditional DV, when supplying heated air via its diffusers has low ventilation effectiveness in heating season. This study investigated a novel wall-mounted displacement induction ventilation (DIV) system in comparison to traditional DV system. The investigation used an environmental chamber to mimic a typical classroom and measured the distributions of air velocity, air temperature, and contaminant concentration for validating the subsequent computational fluid dynamics (CFD) model developed across an array of operational modes. Then the CFD model was employed to evaluate the performance of DIV system in terms of ventilation effectiveness, mean age of air and vertical temperature gradient as it relates to thermal comfort. Each DIV unit receives 100% outdoor (or primary) air to its plenum chamber. As the primary air pressurizes the chamber, it exits a series of nozzles, creating a low pressure which then induces room air across the integral hydronic coil. A room is typically supplied with multiple DIV units, which allows for individual control operation during both cooling and heating modes. Results showed that stratified air distribution was achieved in both cooling and heating modes with DIV system, which remedied the current limitation of traditional DV.