Thermal performance of microencapsulated phase change material slurries in a heated helical coil.

An experimental study has been performed to determine the thermal physical characteristics of microencapsulated phase change material (MPCM) slurries in a heated helical coil. A heated helical coil was fully instrumented to determine friction factor and heat transfer coefficient of water and MPCM slurries. The thermal and fluid properties of the MPCM slurries were determined using a differential scanning calorimeter (DSC) and a rotating drum viscometer, respectively. The pressure drop of MPCM slurries under turbulent flow conditions was measured, and an appropriate dimensionless friction factor correlation has been postulated for MPCM slurries. The local convective heat transfer coefficient of MPCM slurries under turbulent flow conditions was determined, and a Nusselt number correlation has been postulated. The benefits of using MPCM slurries in a helical coil have been quantified by using the performance efficiency coefficient (PEC). The experimental results showed that using MPCM slurries instead of water leads to better performance in terms of heat capacity; however, the heat transfer performance enhancement still is limited by viscosity-related effects. Nevertheless, MPCM slurries perform better in helical coils than in straight tubes, which highlights the importance of selecting and using the appropriate types of heat exchanger for MPCM slurry applications.