Experimental study on natural convective heat transfer of tube immersed in microencapsulated phase change material suspensions

• Synthesis stable suspensions with water–propanol mixture as the base fluid.
• Thermal properties of up to 30% mass fraction suspensions tested.
• Heat transfer coefficient decreases with increasing phase change material concentration.
• Temperature and flow rate of heat transfer fluid enhanced convective heat transfer.

Microencapsulated phase change material suspensions have many potential applications in the fields of energy storage, air-conditioning and exchanger, etc. In this paper, stable microencapsulated phase change material suspensions are prepared with the water–propanol mixture as the base fluid and the addition of dispersants. The dependence of the specific heat, phase change enthalpy, rheological behavior and thermal conductivity of such fluids on the concentration and temperature is experimentally determined. And the heat storage and the natural convective heat transfer performance of tube immersed in the 10wt%–30wt% microencapsulated phase change material suspensions are experimentally studied. The result shows that the natural convection process can be characterized by three regimes: the pure conduction, the quasi-steady and the decay period. The convective heat transfer coefficient of a thick suspension is lower than the diluted one, although more heat can be stored by the thick suspension. And the increase of the temperature and flow rate of heat transfer fluid inside the tube is beneficial to the natural convective heat transfer performance.

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