Enhanced convective heat transfer with Al2O3-water 2 O 3-water nanofluid in a PCM-based thermal energy storage system

Abstract

Heat exchangers play a crucial role in solar thermal applications by facilitating the transfer of heat between different mediums, thereby enhancing the efficiency of energy conversion and storage. Current work deals with experimental investigation of convective heat transfer performance of shell and tube heat exchanger that holds PCM and discharging performance was studied with water and different concentrations of (0.1, 0.3 and 0.6 % by volume) Al2O3-water 2 O 3-water nanofluid as heat transfer fluid followed by their Nusselt number correlations. The blending of Al2O3 2 O 3 with water enhanced their thermal conductivity and in existence of 0.6 % Al2O3, 2 O 3 , thermal conductivity boosted by 18.69% as compared with water. Minor enhancement in viscosity was seen after blending Al2O3 2 O 3 with water which symbolized that nanofluid possesses enhanced heat transfer properties. Pentaerythritol (PE), a solid- solid phase change material (PCM) was selected for current study and was filled inside heat exchanger. Thermogravimetric analysis of PE indicated that PCM is stable till 210 degrees C and subsequently it exhibited constant weight loss. Convective heat transfer performance was studied using a shell and tube heat exchanger where PCM was heated using a heating system at varied heat flux and discharging efficiency was studied using water-based nanofluids. Discharge efficiency was found to be 51.4 % for water at 4 lpm and enhanced to 59.8 and 75.57 % at 6 and 8 lpm respectively with the heat flux of 80 V. Maximum efficiency of 90 % with 0.6 % of Al2O3 2 O 3 at a flow rate of 8 lpm. Nusselt number enhanced by 14.2 % for 0.1 % Al2O3-water 2 O 3-water nanofluid as compared with water. Incorporation of nanoparticles with heat transfer fluid led to an enhancement in heat transfer properties which is quite evidenced by heat recovery efficiency and Nusselt number correlations.