First, solid D- mannitol was poured into the glass vessel before the test heater was set. After D-mannitol was preheated to the melting tempera- ture by the oil bath, the test heater and thermocouple were inserted into liquid D-mannitol. An electric current was supplied to the test heater after the liquid temperature of D-mannitol was confirmed to be stable. The temperature of the test heater surface and the heat flux with passage of time were then measured.