Effect of surface roughness on heat transfer in a thermal energy storage system employing microencapsulated phase change material slurry

摘要

This study examines the effect of surface roughness on the heat transfer efficiency factor in a thermalenergy storage system employing microencapsulated phase change material (MEPCM) slurry. Theheat transfer efficiency factor is defined as the mean Nusselt number ratio for a MEPCM slurry withand without surface roughness. The model employed is applicable to a laminar andhydrodynamically fully developed MEPCM slurry flowing inside a tube using a two-dimensionalconvective heat transfer model. The surface roughness effect was incorporated into the model usinga surface enlargement function defined as the surface area ratio of a MEPCM with and withoutsurface roughness. A range of surface enlargement values were used to calculate the heat transferefficiency factor under a host of conditions. Results show that as the surface roughness of theMEPCM’s increases, the heat transfer efficiency factor decreases. This result emphasizes the needto incorporate surface roughness into MEPCM slurry models in order to avoid over-predicting theheat transfer rate in such systems.