Free cooling system is an energy saving system without chiller operation when the ambient temperature is relatively low and building needs the chilled water for cooling. The prediction method for free cooling performance is described in this paper with the theoretical formulae. The water temperature and the quantity of flow were measured in summer and winter in order to derive the parameters of the evaporative cooling tower. The predicted inlet and outlet water temperatures were agreed well with the measurement and it also shows the free cooling system with evaporative cooling tower may be available in Japan.
