R. Sabbah

This study numerically explores the effect of presence of micro-encapsulated phase change material (MEPCM) on the heat transfer characteristics of a fluid in a rectangular cavity driven by natural convection. The natural convection is generated by the temperature difference between two vertical walls at constant temperatures. The phase change material (PCM) melts in the vicinity of the hot wall and solidifies near the cold wall. Unlike the pure fluids, the heat transfer characteristics of MEPCM slurry cannot be simply presented in terms of corresponding dimensionless controlling parameters such as Rayleigh number. In the presence of phase change particles, the controlling parameters’ values change significantly due to the local phase change. The numerical results show significant increase in the heat transfer coefficient (up to 80%) at the considered operating conditions. This increase is a result of the MEPCM latent heat and the increased volumetric thermal expansion coefficient due to MEPCM volume change during melting.

This experimental study investigates the heat transfer characteristics of a liquid flow with micro-encapsulated phase change material (MEPCM). The MEPCM mass concentration is varied between 0 and 20 percent with average particle diameter of 10 μm. Tube wall temperature profile, fluid inlet and outlet temperatures are measured and the corresponding heat transfer coefficient is determined for various operating conditions. A wide range of the controlling parameters, MEPCM concentration, heat flux, inlet temperature, and flow rate are covered. The results showed significant enhancements in heat transfer coefficient (higher than 50%) and reduction in tube wall temperature (higher than 40%). The results also showed that the heat transfer enhancement curve showed resemblance to the MEPCM specific heat curve.

This numerical investigation fundamentally explores the thermal boundary layers’ characteristics of liquid flow with micro-encapsulated phase change material (MEPCM). Unlike pure liquids, the heat transfer characteristics of MEPCM slurry cannot be simply presented in terms of corresponding dimensionless controlling parameters, such as Peclet number. In the presence of phase change particles, the controlling parameters’ values change significantly along the tube length due to the phase change. The MEPCM slurry flow does not reach a fully developed condition as long as the MEPCM particles experience phase change. The presence of MEPCM in the working fluid slows the growth of the thermal boundary layer and extends the thermal entry length. The local heat transfer coefficient strongly depends on the corresponding location of the melting zone interface. The heat transfer characteristics of liquid flow with MEPCM are presented as well.