Parametric study on melting process of a shell-and-tube latent thermal energy storage under fluctuating thermal conditions

Abstract

The intermittent and fluctuating nature of thermal sources such as solar, geothermal, industrial processes and waste heat from internal combustion engines is one of the most challenging research areas and currently limits the implementation of heat recovery systems such as Organic Rankine Cycle (ORC) technology. Latent Thermal Energy Storage (LTES) using Phase Change Material (PCM) is a promising solution to mitigate fluctuations of thermal sources and maintaining the heat recovery systems under designed conditions. However, the melting process significantly affects the energy storage performance, as well as the design and optimisation of the LTES system under fluctuating thermal conditions. In this study, the melting process of a shell-and-tube LTES unit, under a sinusoidal heat source, is numerically investigated in order to consider the effects of period and amplitude. Then, the effects of PCM thermal conductivity, with and without nanoparticles, were simulated and the heat transfer coefficient of sinusoidal heat source on the melting process is separately analysed under the sinusoidal heat source condition. The parametric study of thermal conductivity and heat transfer coefficient is conducted to evaluate whether these parameters affect the period and amplitude of sinusoidal heat sources on the melting process of LTES. The results indicate an overall trend of the total melting time and heat storage capacity of LTES decreasing whilst there is an increase of period and amplitude of the fluctuating heat source.