Suppressing the Supercooling Effect of Erythritol by Bubbling for Latent Heat Storage

Erythritol, a phase change material (PCM) pertinent to the medium temperature range latent heat storage applications, has the advantages of large storage density, non-toxicity, and high chemical compatibility, but it also suffers from serious supercooling upon cool-down to release the stored heat. In this work, the bubbling method was attempted as an economic and easy way to suppress the supercooling effect of erythritol. At a flow rate of 300 mL/min, N2 bubbles of the size of about 4.4 mm in diameter were continuously introduced into molten erythritol under various subcooling temperatures of ΔTsub = 30, 40, 50, 60, and 95 °C. At the same flow rate, slightly larger bubbles of about 6 mm in diameter were also tested as a contrast case at a single subcooling temperature of ΔTsub = 30°C. The presence of the bubbles was clearly exhibited to successfully facilitate crystallization process of erythritol. It was shown that when ΔTsub = 40, 50, 60, and 95 °C, the introduction of N2 bubbles can reduce the nucleation temperatures Tn by 7.0, 8.2, 10.0 and 5.7°C, respectively, and shorten the crystallization time tc by 19.7%, 14.8%, 13.8%, and 6.4%, respectively. At the lowest subcooling of ΔTsub = 30 °C, erythritol cannot crystallize without the presence of bubbles. The size of the bubbles was found to have negligible effect as the complete crystallization time remains almost the same with the two bubble sizes.