Performance of a direct-contact latent heat energy storage during discharging process has been investigated. The storage medium used is sodium thiosulphate pentahydrate of which the melting temperature is 48 degrees C and the heat exchanging fluid is heat transfer oil. An empirical expression to evaluate the volumetric heat transfer coefficient has been carried out. A lumped analysis is also found to be quite suitable to analyze the temperature of the storage medium and its solid fraction including the temperature of the oil leaving the storage. The results agree well with those of the experiments.