Numerical study on thermal stratification for impinging jet ventilation system in office buildings

Abstract

Thermal stratification is the key to improving energy efficiency and indoor air quality for impinging jet ventilation (IJV) system in cooling mode. However, unclear thermal stratification characteristics of IJV system can degrade the ventilation performance of the IJV. In the present study, the thermal stratification characteristics of an IJV is investigated by the validated simulation model for different supply air parameters and internal heat sources in interior zone of office buildings. The critical value of supply air parameters for the formation of thermal stratification is determined by thermal length scale, which considers the combined effect of inertial force and thermal buoyancy on the supply airflow. In addition, the cooling load in an IJV cooling room caused by the heat source intensity can be calculated directly and the heat source distribution is negligible. The results also indicate that the thermal stratification height (H) only depends on supply air parameters, while the temperature difference between head and ankle level (ΔT) is affected by both supply air parameters and cooling load. The predictive models of H and ΔT are obtained based on the simulation results, which could provide the theoretical basis for optimizing the design scheme of IJV system in interior zone of office buildings.