Airflow and Air Quality in a Large Enclosure

Abstract

Knowledge of air flow patterns and thermal parameters are essential in the design of a ventilation system for large enclosures. The objective of this paper is to evaluate the possibility of using computer simulation to predict the airflow pattern and removal effectiveness of ventilation systems in large enclosures. The quality of air and thermal comfort in a three-floor shopping center are studied by the computational fluid dynamics (CFD) method. Two ventilation systems are selected. In System 1, rooms are ventilated by two ceiling slot diffusers, supplying air downward into the rooms. The halls are equipped with wall jet diffusers delivering air in a horizontal direction. Airflow and air quality, under both summer and winter conditions, are investigated. In System 2, the air in each room is supplied in a radial manner by four ceiling rectangular diffusers. The hall and balconies have jet diffusers which supply air vertically downward. Different ventilation rates, outdoor air ratios and supply air temperatures are studied. Occupants are simulated by heat and CO2 sources without aerodynamic blockages. It was found that the summer and winter air temperature differences in the shopping center differ by approximately 2°C. The rectangular air diffusers should he used in the rooms and the jet diffusers in the halls and balconies. Both the variable air volume and the constant air volume methods, with an adjusted supply air temperature, can be used for air conditioning control in a large enclosure.