Experimental assessment on thermal storage performance of beeswax in a helical tube embedded storage unit

In the present study beeswax is considered as a natural latent heat storage material. A novel rectangular shell and tube type geometry is introduced as a thermal storage unit (TSU), in which copper helical coil carrying hot heat transfer fluid is embedded in the beeswax filled in rectangular shell. Thermal performance study of beeswax is carried out in a series of charging and discharging experiments with water as a heat transfer fluid (HTF). Temperature profiles along the axial and vertical direction of helical coil have been recorded by measuring nine temperatures to understand the mode of heat transfer within the beeswax. Effect of flow rates (0.25 LPM, 0.5 LPM, 0.75 LPM, 1.0 LPM) and inlet temperatures (60 °C, 70 °C, 80 °C) of HTF on charging time and thermal storage efficiency of beeswax is analyzed. It is observed that increase in fluid flow rate reduced the charging time and storage efficiency of the system, however increase in fluid inlet temperature increased the charging time of the system. Maximum efficiency of TSU during charging was 84% when HTF at 80 °C flows through TSU at 0.5 LPM. Results of the study prove beeswax as low cost and naturally available phase change material (PCM) performance wise better than conventional PCMs in lower temperature range.