Evaluation of stack ventilation in a large space using zonal simulation and a reduced-scale model experiment with particle image velocimetry

Abstract

Stack-driven airflow is extensively utilized to improve thermal comfort and exploit energy saving potential during summertime. However, the thermal environment in large spaces is obviously stratified, and the stack ventilation is complex and dynamic. This paper presents a practical zonal stack ventilation method by combining the merits of the intuitive analytical model and the universal zonal model, thereby expanding their application in stack ventilation. As the boundary condition at the opening, the ventilation flow is obtained based on the building geometry, flow characteristics and nonuniform pressure gradient prompted by temperature disparity. Inside the space, an airflow network is constructed, and the airflow movement is determined by a simplified impulse equation, thereby balancing accuracy and efficiency. Moreover, an appropriate solution procedure was developed. Then, this general method was applied to an example large space. A reduced-scale building model was established to approximate the complex and stratified thermal environment in the large space, involving multiple realistic environmental conditions. A particle image velocimetry (PIV) measurement was conducted to investigate the integrated stack-induced airflow pattern in the thermal stratification and further explore the characteristics of the zonal model. After experimental verification, the ventilation flow rate at the opening was 0.001 kg/s for both the simulation and measurement. Inside the space, the maximum air temperature deviation was −0.16 °C, and the root-mean-square error was 0.21 °C.