Performance of Air Curtain located at the top of entrance opening - Difference among indoor/outdoor/double-sided installation

Abstract

Large openings of buildings are often used open, which results in heat loss due to intrusion of outdoor airflow and leakage of indoor air through the opening. To reduce air-conditioning load and to improve thermal environment in such a building, installing an air curtain at the opening can be a beneficial technique. The airflow blowing out of the device suppresses the heat exchange by buoyancy-induced convection through the opening. The impact of temperature difference, blowing speed, and installation position of the air curtain on temperature distribution and invasion flow rate of outdoor air was investigated by full-scale experiment under heating operation. Thermocouples were installed to measure vertical temperature distribution. Outdoor air infiltration was measured using tracer-gas method. The amount of outdoor air infiltration was evaluated based on both temperature difference and CO2 concentration. Comparing the results, it was found that the indoor air curtain was able to suppress the airflow through the opening. The indoor-outdoor temperature difference and CO2 concentration were highest when the air velocity was 4 m/s, suggesting that there is an optimal air velocity at which the air curtain can effectively suppress the airflow through the opening.