Abstract
Salt hydrates have been used as phase change materials (PCMs) for various types of Thermal Energy Storage (TES) especially for cold storage. In this project, a novel composite phase change material (PCM) consisted of mixed solution of inorganic salt and organic salt was developed and characterized. Firstly, the PCM solutions containing sodium formate, potassium chloride and water with various weight percentage were evaluated to understand their solidification temperature, melting temperature, the supercooling degree and the latent heat. Then a PCM with mass fractions at weight percentages of 22%/12%/66% with better performance was selected for further study to restrain the supercooling. Different gelling agents and nucleate agents were employed in this PCM. The results show that the addition of 0.6 wt% xanthan gum can effectively prevent the phase separation and leakage, while 0.6 wt% of nano-TiO2 is the best nucleating agent since the supercooling can be reduced to 2.6 °C, which is 67.9% lower than that of the original PCM without any nucleating agent. Finally, the novel PCM was tested for frozen food storage application, in which the food temperature could be maintained below -18 °C for over 10 hours in the insulated box. This indicated the suitability of developed PCM for frozen food storage and transportation.
Highlights
As energy saving has become increasingly important in recent years, cold storage technology as a potentia solution for energy saving and energy load shifting has received significant attentions
Two clear turning points are observed for all tested samples, and the first one indicates the existence of the supercooling phenomenon in the discharging process
Based on the optimal SPW solution, the effects of various additives on the thermal performance including the solidification and melting processes and supercooling were comparatively examined. 0.6wt% xanthan gum and 0.6wt% nanoTiO2 were found to be the ideal candidates for minimizing the supercooling, phase separation and leakage and improving the thermal stability of Phase change materials (PCMs) in solidification and melting processes
Summary
As energy saving has become increasingly important in recent years, cold storage technology as a potentia solution for energy saving and energy load shifting has received significant attentions. Most of previous researches focused on medium and high temperature PCM, and most of them cannot be used for cold storage for applications like frozen food transportation because the melting temperatures of most binary eutectic water-salt solutions are not far from 0 ◦C. For low-temperature cold chain logistics applications below −23 ◦C, Jin et al (2021) developed a new composite phase-change cooling material consisting of sodium acetate (HCOONa), ammonium chloride (NH4Cl) and water, which can be used in a homemade insulation tank to keep frozen meatballs below −23 ◦C for more than 20 h, which can meet the requirements of short-distance cold chain transportation. The energy storage performance of the optimized SPW gel composite was tested as phase change cold storage material in insulated box for frozen food storage and transportation. The layout of the PCM in the insulated box has been optimized to achieve the best insulation effect
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