Dominant roles of eccentricity, fin design, and nanoparticles in performance enhancement of latent thermal energy storage unit

Abstract In this paper, numerical and experimental investigations of thermal performance enhancement of horizontal longitudinal shell and tube latent heat thermal energy storage unit (LHTESU) via eccentricity (e), fin design optimization, and nanoparticles in the phase change material (PCM) of stearic acid are presented. An enthalpy-porosity-based two-dimensional, transient numerical methodology is used after validating against the experimental results and the literature. Five different eccentric positions, e = 0.14, 0.28, 0.42, 0.56, and 0.63 are investigated by modifying the design of Y-finned tube. The eccentricity and fin design modifications improved natural convection effects as compared to concentric Y-finned tube. Thermal performances of LHTESU are analyzed on the basis of melting time, heat storage capacity, heat storage rate, and performance enhancement ratio. Based on the performance analysis, an optimum eccentric configuration of LHTESU is proposed. For optimized eccentric unit (e=0.42), a reduction of 34.14% in melting time along with 30.7% improvement in thermal energy storage rate is achieved as compared to concentric (e=0) LHTESU. The effect of temperature of the tube on PCM's melting time and heat transfer is also analyzed and two important correlations are proposed. The thermal performance of the optimized eccentric unit is further enhanced by adding nanoparticles of A l 2 O 3 and C u O ranging from 0.5% to 10% by volume in the pure PCM. The nano-enhanced PCM with 1% of A l 2 O 3 further improves melting and energy storage rates of optimum LHTESU by 10%.