Ice formation process for ice thermal energy storage by cooling water-oil emulsion with stirring in a vessel - effects of thermal resistance of wall with low critical surface tension on ice formation process

摘要

A water-oil emulsion which is the mixture of silanol-aqueous solution and silicone oil was frozen in a vessel with stirring under various cooling temperatures. The cooling surfaces of the vessels were PTFE or PFA whose critical surface tension is relatively low. The effects of the wall thermal resistance on ice formation process were investigated. The relationship between the state of formed ice and cooling heat flux during freezing was clarified. When the critical surface tension of the inner wall of the cooling surface is fixed, a smaller thermal resistance of wall enables the ice formation without ice adhesion to the surface at a higher ice formation rate. Ice can be formed without adhesion at the lower cooling temperature by using the vessel with a larger thermal resistance although the maximum cooling heat flux is relatively small. The maximum cooling heat flux decreases when the ratio of wall thermal resistance to overall thermal resistance before freezing is more than one half. It was shown that there were proper conditions to increase the cooling heat flux and that ice could be formed with high IPF under the proper conditions.