Cooling load reduction effect and its mechanism in between-glass cavity and venetian blind operation during the summer season

The proper operation of venetian blinds in between-glass cavity airspaces is one of the most commonly used passive control techniques and can significantly reduce the cooling load and energy use in buildings. This study investigated the cooling load reduction effect of the blind integrated with the cavity operation. A full heat balance analysis was performed using EnergyPlus to provide a detailed understanding of the heat transfer mechanism that takes place around the blind and between-glass cavity. A sensitivity analysis was also carried out to evaluate the effects of different slat angles and blind operation hours. The results show that integration of the blind and between-glass cavity operations can significantly reduce the cooling load in buildings. The cooling load reduction effect of the cavity operation (by approximately 50%) was greater than that of the blind operation (by 5% to 40%, depending on slat angle and operating hours). It was found that the interzone heat transfers between the cavity and the room space and convection heat fluxes from each surface mainly contribute to the total cooling load reduction. In addition, the double-sided blind had a greater potential to reduce the cooling load compared with a conventional single-sided blind due to its greater capability of reflecting direct solar radiation and preventing diffuse solar radiation from penetrating the room space. The results of the study show that the largest reduction of cooling load can be achieved by the cavity operation, followed by the blind operation and the proper selection of operating hours for the blinds.