Abstract:Heat transfer equations describing the phase change in a cold storage sphere were set up. The control volume method was used to construct finite differential equations. Temperature curves in an ice sphere during phase change processes were measured by experiments. The numerical results of these temperature curves agree well with experimental ones. It is found that phase change time for a sphere of 100 mm diameter is 2.4 times of that needed for a sphere of 50 mm diameter. When the convective heat transfer coefficient is at a low value, increase of the coefficient can decrease the phase change time remarkably. Phase change time increases linearly with the initial temperature of ice sphere. When the temperature of heat transfer fluid is near 0 ℃, change of temperature influences phase change time sharply. The calculated results can be used to determine the heat transfer parameters of ice spheres for thermal storage usage.