Thermal performance of double skin façade with built-in pipes utilizing evaporative cooling water in cooling season

Abstract

As an advanced envelope, the double skin façade (DSF) is popular due to its distinguished aesthetic and thermal performance. However, the temperatures of the air cavity and shading device of a DSF are both high in the daytime in summer. A system of embedding cooling pipes into the venetian blinds of DSFs to reduce the heat gain in summer is proposed in this study. Cooling water is circulated in the pipes to take away the radiant heat directly, and the cool water is provided by a natural cooling source. A comprehensive numerical model is presented to simulate the dynamic heat transfer in the DSF in a complete cooling season, and the model has been validated by experimental data. The performance of the pipe-embedded DSF is investigated regarding different ventilation and operation strategies. Cooling water is produced from a cooling tower as it is one of the most convenient ways to utilize natural cooling in buildings. The heat transfer process of the novel DSF is analyzed and compared with the traditional DSF. And influencing factors such as climate and orientation are evaluated. The results show that the pipe-embedded DSF is very effective in dealing with solar radiation, and thus it is suitable for operation in the daytime and in sunny positions. The cavity of the DSF should be closed because the air temperature in the cavity is even less than the ambient air temperature. The effectiveness of the pipe-embedded DSF is more than 20% in all the selected typical cities in China. In particular, the effectiveness is as high as 80% in Urumchi, due to its large solar radiation and efficient evaporative cooling. Thus the presented novel DSF is energy-efficient, and may be promising to popularize in most regions.