Abstract
There has been a growing awareness of the importance of conserving fossil energy resources and developing the techniques of passive heating/cooling systems in buildings which utilize natural sources of energy and the natural environment. It's necessary to investigate the possibility of passive cooling in summer as well as passive heating in winter. One technique of passive cooling, water evaporative cooling is considered to be promising. This study deals with water evaporative cooling by means of roof spraying. From the standpoint of saving water in roof spraying systems which use a minimum rate of water with no water recovery system, the optimum rate of water supply in roof spraying was examined experimentally through the use of wooden experimental structure. The experimental structure was designed so as to enable insulation properties of the walls, roof and floor to be controlled through the replacement of insulation materials. This paper describes the estimated optimum rate of water supply of roof spraying systems in various areas of Japan, by using the experimental results. Analyzing the relationship between the calculated evaporation rate and measured rates of supplied and returned water for experimental structure statistically, the regression line can be derived, which is used to calculate the required rate of water supply in roof spraying. Then a method is developed, which revises the required rate of water supply for various shapes of the roofs, using the parameter of L/S. Here L is the outline length [m] of a roof and S is the sprayed roof area [m^2], which can be covered by one sprinkler. After analyzing the regression line and the calculated evaporation rates in various areas of Japan, the required minimum rates of supply water in various parts of Japan were estimated, which are for roof spraying systems with no water recovery.
