Cool release process of phase change material (PCM) includes the dissolution process of the PCM. Experimental research on the cool release process in a new gas-hydrate cool storage system is performed in this paper. In the system, the inner-heat exchange/outer-crystallization technology and the integrated condenser/evaporator structure design were adopted. The influences of different proportions of calcium hypochlorite or benzenesulfonic acid sodium salt on the dissolution process are studied. The results show that the instantaneous dissolution rate is close to twice as the corresponding instantaneous formation rate of gas-hydrate, and the cold energy release rate, i.e. energy release per unit time, is obviously higher than the corresponding cold energy storage rate at different conditions, which is mainly due to the heat transfer temperature difference of the discharging (release) and charging (store) processes. Both the charging and the discharging processes are simultaneously dominated by the heat transfer and the mass transfer processes. However, as to the dissolution (discharging) process of the gas-hydrate by heating, the effect of the heat transfer process is the main influence factor. The temperature difference between the heating medium and the gas-hydrate in the discharging process, which is larger than that between the cooling medium and the gas-hydrate in the charging process, makes a higher cold energy release rate compared with the cold energy storage rate. The results also indicate that the dissolution rate of gas-hydrate is accelerated, and the cold energy release rate of the cool storage system is increased by adding reasonable proportions of the additives. (C) 2008 Elsevier B.V. All rights reserved.