Study on Enhancement Effect of Natural Convection During Melting Heat Storage Process of Phase Change Materials
In order to clarify the enhancement effect of natural convection during the melting heat storage of phase change material(PCM),the melting heat storage experiment of phase change paraffin under constant heat source on side was carried out.Based on the fluid-solid-thermal coupling theory,the calcu-lation model of melting heat storage in PCM was established.The size effect and directivity impacted by natural convection heat transfer were analyzed,and then the influence of heating temperature and initial temperature on heat storage efficiency was studied.The results show that at a constant temperature heat source on the side,the natural convection movement of liquid phase in the square cavity will lead to a in-clined melting front,and improve the melting heat storage efficiency by 12.1 times.There is a size effect under natural convection in liquid phase,the enhancement effect can be basically negligible when the side length of the square cavity is less than 2 mm.The natural convection movement in liquid phase is significantly affected by the direction of heat source.When the heat source direction angle rotates from 90° to 270°,the liquid phase natural convection effect will be gradually activated,the flow state of liquid phase will change from a single large circulation to several small irregular circulation,finally,the maxi-mum heat storage efficiency is achieved under the bottom heat source,and change into a wavy melting front.When the heating temperature increases from 60℃to 100℃,the natural convection enhancement coefficient is increased by 20%.When the initial temperature drops from 25℃to 5℃,the natural con-vection enhancement coefficient decreases by 10.2%.
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