Aerodynamic sealing using a segmented recirculating horizontal air curtain for buoyancy-driven flows in doorways

Abstract

Dealing with buoyancy-driven flow to reduce infiltration heat is challenging for buildings such as cold storages where the indoor-outdoor temperature differences are significant. In this study, a segmented recirculating horizontal air curtain (SRHAC) is proposed to respond to the vertical thermal buoyancy profile in doorways and recover the cold air entrained by the air curtain. Specifically, SRHAC is a planar turbulent impingement jet discharged through a vertically mounted rectangular nozzle. The discharge nozzle is divided into segments and the return vent recirculates the discharged air to the rear of the discharge nozzle. In this study, the aerodynamic sealing performance of the SRHAC is investigated by considering structural, operational, and ambient parameters. Orthogonal analysis reveals the flow rate, nozzle width, and discharge angle as significant factors affecting the thermal separation efficiency of the SRHAC. Increasing the flow rate and decreasing the nozzle width leads to an increase in the jet momentum flux, thereby enhancing the thermal separation efficiency, with a maximum efficiency of 75.9 %. Setting the discharge parameters in the three sections along the height improves the thermal separation efficiency by 16.5% points. The maximum efficiencies of two-, three-, and five-segment air curtains are 83.6 %, 87.3 %, and 90.3 %, respectively. The separation efficiency of the SRHAC remains relatively stable even when the indoor-outdoor temperature difference varies between 32 and 57 K. These results establish that the SRHAC is an efficient energy-saving device, with the ratio of reduced infiltration load to energy consumption as high as 110.9.