Experimental Investigation of Stearic Acid in the Thermal Battery Comprising a Fin and Tube Heat Exchanger

Abstract

Phase change materials (PCM) are employed in thermal energy storage (TES) systems for various applications due to their high energy density. This paper uses a fin and tube heat exchanger made of aluminium and copper in the thermal battery to enhance the heat transfer rate. The HYTHERM 600 is used as the heat transfer fluid (HTF), and stearic acid as the PCM. The experiment analyses the thermal behaviour of stearic acid in the thermal battery. The HTF maintains around 80°C and 85°C in the Hot HTF tank. Results show that conduction is dominant during the early melting stages; however, natural convection supersedes conduction after the stearic acid has liquefied. Conduction serves as the main mechanism of heat transfer during the discharging. The HTF temperature considerably enhances the stearic acid melting rate. The energy storage while charging and discharging is 248.03 kJ/kg and 211.81 kJ/kg, 254.50 kJ/kg, and 218.35 kJ/kg at 80 o C and 85 o C hot HTF temperatures. As the HTF temperature increases from 80 o C to 85 o C, the charging efficiency and higher temperature increase by 8.03% and 6.76%, and the melting time drops by 18.19% during the melting process, but in the discharging of stearic acid, discharging efficiency and lower temperature increases by 6.92% and 7.06%, and discharging time decreases by 25%.