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Efficient and rational use of thermal energy requires the design and development of suitable and cost-effective latent heat storage systems. In this study, a novel curved thermal storage unit is put forward and its thermal behavior has been numerically compared with the traditional rectangular PCM-based thermal storage unit. The solid-liquid interface evolution, liquid flow pattern and temperature distribution are presented. Transient Nu at the heating wall and full melting time are also calculated. The numerical results show the high impact of the enclosure geometry on melting and nature convection. A reduction of 30.6 % in thermal storage time has been achieved by changing the unit from rectangular to curve. Moreover, parametric studies are conducted to assess how thermal performance of the units is affected by the heating wall temperature and PCM thermal conductivity. Correlations encompassing a wide range of parameters are developed in terms of full melting time. Results indicate that proportion of full melting time reduced for the curved unit is almost a constant value and does not vary significantly with these factors. All these may be very helpful for the design of more efficient thermal storage units. [ABSTRACT FROM AUTHOR]

Thermal energy storage plays an important role in correcting the disparity between energy supply and demand as well as improving the energy efficiency. The present work numerically investigates the conjugate heat transfer between PCM and heat transfer fluid within the novel and efficient frustum-shaped thermal storage units. A two-dimensional control volume-based numerical model is developed employing the CFD software Fluent. Five units of equal volume but different dimensions are compared to illustrate impacts of geometry on melting, and the optimal geometric design is determined. Then, the multiple PCMs technology is employed to the optimal unit to further enhance the melting heat transfer. Effects of the multiple PCMs arrangement, multiple PCMs' melting temperature distribution, and type on the melting behavior and heat transfer are investigated. Compared with the frustum-shaped and traditional shell-and-tube unit with a single PCM, predicted results indicate that the five PCMs arrangement in frustum-shaped unit can make the thermal storage time reduced by 21.5 % and 47.5 %, respectively. The great improvement may be of great significance to the optimal design of latent heat storage. [ABSTRACT FROM AUTHOR]