Performance evaluation of cascaded storage system with multiple phase change materials

An experimental and numerical study on phase change material melting rate enhancement for a horizontal semi-circular shell and tube thermal energy storage system

Latent heat storage has high storage density with a smaller temperature swing. However many practical problems are encountered. A common problem in latent heat thermal storage is the poor conductivity of the phase change materials (PCMs). To increase the heat transfer rate and to reduce the charging time, extended surfaces such as fins are used. In the present work experiments are conducted to study the performance of latent heat thermal energy storage system (LHTS) to store heat energy in PCM (Paraffin) filled spherical capsules provided with following fin configurations: a) Internal hollow cylindrical fins, b) Internal solid cylindrical fins and c) No fins. Paraffin with a melting point of 610C was used in the investigation because it is appropriate for thermal storage applications. Water is used as heat transfer fluid (HTF) to transfer heat from source to TES tank. Time-based variations of the temperature distribution for HTF and PCM have been studied for different configurations of spherical capsules, different flow rates & inlet temperature of HTF. It is observed that when HTF inlet temperature is varied from 65°C to 70°C the charging time is reduced by 25% for without fins, 28% for internal hollow cylindrical fins and 23% for internal solid cylindrical fins. When flow rate is varied from 4 lpm to 6 lpm for same HTF inlet temperature of 70°C charging time is reduced by minimum percentage. The performance parameters such as instantaneous heat stored, cumulative heat stored and system efficiency are also studied.

Experimental and numerical characterization of natural convection in a vertical shell-and-tube latent thermal energy storage system

Numerical study and multilayer perceptron-based prediction of melting process in the latent heat thermal energy storage system with a finned elliptical inner cylinder

Review of passive PCM latent heat thermal energy storage systems towards buildings’ energy efficiency

While solar thermal power plants are increasingly gaining attention and have demonstrated their applications, extending electricity generation after the sunset using phase change material (PCM) still remains a grand challenge. Most of the organic PCMs are known to possess high energy density per unit volume, but low thermal conductivity, that necessitates the use of thermal conductivity enhancers (TCEs) to augment heat transfer within PCM. In this paper, thermal performance and optimization of shell and tube heat exchanger-based latent heat thermal energy storage system (LHTES) using fins as TCE for medium temperature (<300 °C) organic Rankine cycle (ORC)-based solar thermal plant are presented. A commercial grade organic PCM, A164 with melting temperature of 168.7 °C is filled in the shell side and heat transfer fluid (HTF), Hytherm 600 flows through the tubes. A three-dimensional numerical model using enthalpy technique is developed to study the solidification of PCM, with and without fin. Further, the effect of geometrical parameters of fin, such as fin thickness, fin height, and number of fin on the thermal performance of LHTES, is studied. It is found that fin thickness and number of fin play significant role on the solidification process of PCM. Finally, the optimum design of the fin geometry is determined by maximizing the combined objective of HTF outlet temperature and solid fraction of PCM at the end of the discharging period. The latent heat thermal storage system with 24 fins, each of 1 mm thickness and 7 mm height, is found to be the optimum design for the given set of operating parameters.

Nanostructures assisted melting of phase change materials in various cavities

Numerical analysis of latent heat thermal energy storage using encapsulated phase change material for solar thermal power plant

A novel correlation for the direct determination of the discharging time of plate-based latent heat thermal energy storage systems

Latent heat thermal energy storage (LHTES) systems are essential for efficient thermal energy storage. However, these devices are often constrained by long charging and short discharging periods. This study presents a novel triplex‐tube LHTES design incorporating a copper helical coil positioned between two concentric stainless‐steel shells. Stearic acid was used as the phase change material and water as the HTF, with two separate flow paths provided for charging and discharging. During charging, HTF is circulated through the outer shell at a higher mass flow rate to increase energy input and accelerate the charging process. During discharging, HTF flows through the inner helical copper coil at a reduced mass flow rate, increasing its residence time by 97.54%. This enhances the uniformity index and extends the discharge duration by 26.8% compared to a conventional concentric triplex‐tube design. Additionally, the discharge efficiency increases to 87.5% due to a 31.4% rise in heat‐transfer area and higher thermal conductivity of copper compared to stainless steel.

Purpose This study aims to address the low thermal conductivity and suboptimal performance of phase change materials (PCMs) by examining the impact of geometric adjustments on their melting rate. Design/methodology/approach A two-dimensional numerical model was created to investigate the effect of different positions and angular inclinations of the inside heating surface (IHS) on the melting rate of PCM within a latent heat thermal energy storage system. The model analysed the IHS at the centre and below the centre at various positions (10, 20, 30 and 40 mm) and inclinations (0°, 15°, 30°, 45°, 60°, 75° and 90°). Findings The 90° inclination (vertical) significantly reduced the melting time by 75% compared to the 0° inclination (horizontal). The best melting performance was recorded with the IHS positioned 20 mm below the centre. At a 30° inclination, the maximum reduction in melting time was observed with the IHS at 30 and 40 mm placements. The system demonstrated the highest energy storage capacity of 307.72 kJ/kg at a 75° inclination with the IHS positioned 10 mm laterally, and the lowest capacity of 255.02 kJ/kg at a 0° inclination with the IHS at a 30 mm lateral position. Practical implications To address the deficient part of PCM like low thermal conductivity and below level performance characteristics, a structural (geometrical) adjustment was developed to study the effect on the melting rate of PCM without any cost addition. Using the computational model, an optimised thermal energy storage system is developed that can play a pivotal role in improving the applicability of thermal energy storage systems. Originality/value This research is novel in simultaneously investigating the numerical characteristics of PCM melting behaviour with different lateral positions and angular orientations of the IHS. A unique design modification was introduced, using a 2D numerical model and simulations to explore the effects under isothermal conditions.

Enhancing heat transfer during the charging process of latent heat thermal energy storage (LHTES) systems remains a critical challenge due to the low thermal conductivity of phase change materials. This study presents an experimental and numerical investigation of a finned LHTES unit employing paraffin RT82 enhanced with 0–10 vol.% Al 2 O 3 nanoparticles. Longitudinal fins and multiple heating configurations were examined to elucidate their effects on conduction‐ and convection‐dominated heat transfer during melting. A transient enthalpy–porosity model was developed and validated against experimental data, with temperature deviations remaining within 3%. Dual‐sided heating provided the most uniform thermal distribution, achieving complete melting within 4 h at an HTF inlet temperature of 90°C and a mass flow rate of 37.5 kg/min. The dispersion of Al 2 O 3 nanoparticles increased the effective thermal conductivity of the PCM to 0.265 W/m·K at 10 vol.%, accelerating heat diffusion and reducing charging time, particularly under external and dual‐sided heating. Axial temperature measurements revealed reduced thermal gradients due to the combined effects of fin‐assisted conduction and nano‐enhanced heat transport. Under transient HTF inlet conditions, optimal thermal response occurred at a flow rate of 29.4 kg/min, reflecting a balance between convective transport and residence time. A nearly constant HTF inlet–outlet temperature difference during melting indicated stable latent heat absorption. The analysis is limited to charging behavior under controlled conditions. Uncertainty analysis confirmed high measurement reliability, with onset and peak melting temperatures of 70.13°C ± 0.15°C and 82.18°C ± 0.05°C, respectively.

Performance study of a novel funnel shaped shell and tube latent heat thermal energy storage system

Thermal performance of cascaded latent heat thermal energy storage units constructed based on solid-liquid interface information

A numerical study on the effect of the number and arrangement of tubes on the melting performance of phase change material in a multi-tube latent thermal energy storage system