Performance characteristics of microencapsulated phase change material slurry in a helically coiled tube

•Friction factor correlation for MPCM slurry in a coiled tube has been postulated.•Local heat transfer of MPCM slurry in a coiled tube is characterized.•Nusselt number correlation for MPCM slurry in a coiled tube is proposed.•A helically coiled tube enhances the phase change process of MPCM particles. Flow and heat transfer characteristics of microencapsulated phase change material (MPCM) slurry as a heat transfer fluid (HTF) in a heated helically coiled tube have been investigated experimentally. Thermophysical properties of MPCM slurry were determined experimentally. A fully instrumented helical coil system was designed, built, and characterized to conduct pressure drop and heat transfer experiments at different mass fractions of MPCM slurries under turbulent flow conditions. Pressure drop and friction factor of MPCM slurry in the coiled tube were measured and correlated using the Dean number. Local convective heat transfer of MPCM slurry flowing through the coiled tube was characterized under turbulent flow and constant heat flux conditions. In addition, useful correlations have been postulated to predict Nusselt number of MPCM slurry. Furthermore, overall thermal performance analyses have been conducted to determine the benefits of using MPCM slurry in terms of heat transfer and heat capacity, respectively. The results showed that the enhancement in heat transfer performance is restricted due to the high viscosity and low latent heat of fusion of phase change material (PCM), but MPCM slurry still exhibits enhanced heat capacity when compared to water. Also, it was found that a helically coiled tube is more appropriate for convection of MPCM slurry than a straight tube.