A review of phase change heat transfer in shape-stabilized phase change materials (ss-PCMs) based on porous supports for thermal energy storage

Latent heat thermal energy storage (LHTES) uses phase change materials (PCMs) to store and release heat, and can effectively address the mismatch between energy supply and demand. However, it suffers from low thermal conductivity and the leakage problem. One of the solutions is integrating porous supports and PCMs to fabricate shape-stabilized phase change materials (ss-PCMs). The phase change heat transfer in porous ss-PCMs is of fundamental importance for determining thermal-fluidic behaviours and evaluating LHTES system performance. This paper reviews the recent experimental and numerical investigations on phase change heat transfer in porous ss-PCMs. Materials, methods, apparatuses and significant outcomes are included in the section of experimental studies and it is found that paraffin and metal foam are the most used PCM and porous support respectively in the current researches. Numerical advances are reviewed from the aspect of different simulation methods. Compared to representative elementary volume (REV)-scale simulation, the pore-scale simulation can provide extra flow and heat transfer characteristics in pores, exhibiting great potential for the simulation of mesoporous, microporous and hierarchical porous materials. Moreover, there exists a research gap between phase change heat transfer and material preparation. Finally, this review outlooks the future research topics of phase change heat transfer in porous ss-PCMs

Thermal performance of novel indirect passive solar dryer

An experimental investigation was conducted to study the performance of a novel indirect type free convection solar dryer. The novel and a conventional indirect passive solar dryer were built. Solar irradiation and temperature of different locations were recorded. The air at the drying chamber entrance, lower space, and upper space temperatures besides the thermal efficiency of the novel dryer were 68, 39, 49 and 85%, respectively, higher than the conventional one

Effect of convection heat transfer on thermal energy storage unit

Latent heat storage represents a promising technique to achieve net zero energy buildings. This work investigates the behaviour of phase change material (PCM) inside a rectangular enclosure, which represents the geometry of a latent heat storage system. The left side of the unit is exposed to a constant temperature (Th), while the other three walls are exposed to convection heat transfer boundary condition [h= 5, 10, and 15 W/(m2 K)] and different ambient temperatures (T∞ = 297◦ and 307◦K). The ambient temperatures were selected to be at/above the melting temperature of the studied PCM (coconut oil). To study the melting process of the PCM, the continuity, Navier-Stokes and energy equation were used. The Navier-Stokes equations were modified using the Carman-Kozeny relation. The finite element method was utilized to produce numerical results. The results are presented in terms of flow and thermal fields, Nusselt number (Nu), and the melt fraction (MF) of the PCM. The results show that, when T∞ = Tm, the melting rate of the PCM slows down with increasing the convection heat transfer coefficient. While the melting rate accelerates with increasing the convection heat transfer coefficient when T∞ > Tm

Closed Solar Air Heater System Integrated with PCM (RT42 and RT50) in a Thermal Storage-Finned Heat Exchanger Unit

Utilizing thermal storage integrated into a solar air heater SAH is a promising solution to enhance the thermal performance of solar air heaters. The present work experimentally investigated the thermal impact of an absorber-finned heat exchanger-thermal storage unit integrated inside a solar air heater. The experiments were conducted under the conditions of Tikrit-Iraq in December 2021 and January 2022. RT42 and RT50 were used as PCMs in two separate solar air heaters. Each PCM filled the thermal storage of SAH. A finned heat exchanger, in which air was forced through, was immersed in the thermal storage. Two arrangements were tested. In the first arrangement, the two SAHs were separated from each other. In the second arrangement, the two SAHs were connected in series, first the RT42 SAH and then the RT50 SAH. The results showed that the highest recorded temperature was for RT50, i.e., 59 °C, in the separation arrangement. Also, the solar air heater with RT50 in the series arrangement continued to heat the forced air until 5 AM the next day