Abstract
The purpose of this study is to develope a passive cooling system in which water evaporative cooling and atmospheric radiative cooling are used together, effectively. The authors carried out a series of field experiments with twin test houses and simulations for these houses. The double envelope system which had outer insulation materials of a roof and walls saturated with water and had panels for solar shading at the outside wall surfaces was applied to the houses. To examine a method of making full use of atmospheric radiative cooling, the roof panel of one house was movable and could be opened in the nighttime, while the roof panel of the other took form of a duct and the air in the roof duct cooled by longwave radiative heat exchange to the sky was circulated through the test house. The former was designated the movable roof panel system and the latter was designated the air cycle system. The results were obtained as follows: (1) The water evaporative cooling system in which the outer insulation materials are wetted can be an effective method of preventing1 room air temperature rising excessively in the summer, including a rainy period. (2) The room air temperature of the air cycle system is approximately 5 degrees lower in the daytime and 0 to 1 degree higher in the nighttime than the outdoor air temperature. (3) In case of circulating the room air with fans, as the air circulation rate increases, the cooling effect of the air cycle system increases. (4) The insulation material that has been saturated with water in summer may be air-dried in winter as long as supply water is stopped. In this case, the room air temperature is 5 to 17 degrees higher all day long than the outdoor air temperature, because the outer insulation material has a high thermal resistance.
