Wind effects on air curtain performance at building entrances

Abstract

Air curtains have been widely used as a mean of reducing infiltration and associated energy losses through building entrances. Since quantifying the infiltration rate through the entrances is directly related to air curtain energy performance, previous studies investigated the infiltration through air curtain doors accounting for door operation, usage frequency, air supply angle and velocity etc. Limited studies have focused on the effect of the wind on air curtain performance, although wind is quite common and could interact with air curtain directly. The purpose of this study is to evaluate experimentally the performance of air curtain under different wind speeds and directions, and their interactions with air curtain jet considering different supply speeds, angles, and pressure differences across the air curtain. The experiments were mostly conducted in an atmospheric boundary layer wind tunnel in a sub-scale building model to represent the actual large-scale air curtain performance in terms of the function of dimensionless air infiltration rate versus the dimensionless pressure difference across the air curtain. The study found that air curtains could resist a certain level of wind speed but could be penetrated by high wind mostly at the lower section of the door, which may be avoided by selecting suitable air curtain speeds and angles, increase of indoor pressures, and entrance door types; the wind effect is the strongest for wind blowing straight-onto the air curtain and decreases with the inclined angles before arriving at the minimal effect at a certain angle, as defined by new wind pressure coefficients.