A theoretical analysis is presented for the phase change process occurring in a cylindrical annulus in which rectangular, uniformly spaced axial fins, spanning the annulus, are attached to the inner isothermal tube, while the outer tube is kept adiabatic. The model assumes conduction to be the only mode of heat transfer. The governing equations are solved by finite-difference methods. The time-wise evolution of the interface profile, phase-change fraction and energy stored/discharged and the effect of all the nine prescribable parameters are presented here. Based on the analysis a working formula VF = 1.1275 (Fo Ste Tf)0.624 (N)0.028 (L)-1.385(W)-0.049 is suggested for engineering design purposes. © 1986.

P. V. Padmanabhan

Energy Storage

AXIAL FINS

AXIALLY FINNED ANNULUS

Extended Surfaces

LATENT HEAT THERMAL ENERGY STORAGE (LHTES)

Phase change process

Heat transfer

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IIT Madras

Outward phase change in a cylindrical annulus with axial fins on the inner tube

International Journal of Heat and Mass Transfer

Thermal energy storage is important to counter balance demand and supply of energy and maintain balance in the system and boost the use of intermittent renewable energy source. Phase change material-based thermal energy storage has massive potential to substitute large-scale energy demand and assist both economic and environmental benefits. This paper reviews functional principle, thermophysical properties and other material characteristics of different phase change materials for thermal energy storage system. Long-term stability of phase change material and its interaction with storage container have been discussed. Various heat transfer and thermal conductivity enhancement technique to enhance latent thermal energy storage system have been discussed. The paper also examines the schematics of some of the proposed & tested systems and describes the results of prototype setup for thermal load management and application in water heating system and buildings. The paper also summarizes energy and exergy analysis of some thermal energy storage systems. © 2017 Elsevier Ltd

Journal of Energy Storage

Review of latent heat thermal energy storage for improved material stability and effective load management

This paper presents the effectiveness of finned multi-tube latent heat thermal energy storage system (LHTES) for medium temperature (∼200 °C) solar thermal power plant in reducing the fluctuations in heat transfer fluid (HTF) temperature caused due to the intermittent solar radiation. Commercially available phase change material (PCM) of melting temperature 168.7 °C is used as the storage material in the shell of LHTES, whereas a thermic oil based HTF passes through the tubes. Majority of the available PCMs have very low thermal conductivity (∼0.2–0.5 W/m.K), which drastically affects the thermal performance of the thermal storage system. Hence, in this study, thermal conductivity enhancer (TCE) in the form of fin is used to enhance heat transfer in the PCM. The fluid flow and heat transfer behaviour latent heat thermal energy storage system in the LHTES is studied by using a numerical model coupled with the enthalpy technique to account for the phase change process in the PCM. The developed numerical model, which is validated with the lab-scale experimental setup, is used to investigate the effect of number of fin, fin thickness and fin height on the HTF temperature at the outlet of the storage system. It is found that the number of fins and fin thickness significantly affect the thermal performance of the storage system, whereas the enhancement in heat transfer for high thermal conductivity material fin is marginal. Further, optimization of LHTES is performed for a defined objective function to identify the best configuration. © 2018 Elsevier Ltd

Journal	International Journal of Heat and Mass Transfer
ISSN	00179310
Open Access	No