Experimental performance analysis of beeswax/expanded graphite composite for thermal energy storage in a shell and tube unit

Abstract

In this study, pure beeswax and its novel composite with expanded graphite (10% wt.) were tested for thermal storage efficiency in a rectangular shell and helical tube storage unit. Low thermal conductivity of beeswax is improved by adding expanded graphite of 10% wt. Thermal characterization of beeswax and its composite was performed using differential scanning calorimetry and thermogravimetric analysis. Effect of hot fluid flow rates (0.25 liter per minute [LPM], 0.5 LPM, and 1.0 LPM) and inlet temperatures (60ºC, 70ºC, and 80ºC) on the charging time of beeswax and its composite was studied and compared. Charging time of beeswax and its composite reduced with an increase in fluid flow rate and inlet temperature. At 0.5 LPM flow rate and 80°C inlet fluid temperature, the charging time of composite was reduced by 630 min as compared to pure beeswax. Smaller charging time, improved thermal conductivity, and better thermal storage efficiency of composite material suggest it as a useful storage material for a wider range of applications.