Heat release performance of direct-contact heat exchanger with erythritol as phase change material

• Direct-contact heat exchanger with a phase change material and heat transfer oil.
• We examined effects of operating conditions on performance of latent heat release.
• We found the optimum conditions to flow heat-transfer-oil uniformly.
• The uniform flow improved the performance of latent heat release.
• Heat release rate increased with the flow rate of the inlet heat-transfer-oil.

This paper describes heat-release performance of a direct-contact heat exchanger using erythritol as a phase change material (PCM) along with a heat-transfer oil (HTO). A vertical cylinder with an inner diameter of 200 mm and a height of 1000 mm was used as a heat-storage unit (HSU). A nozzle with nine holes in diameter of 3.0 mm facing vertically downward was placed at the bottom of HSU. We examined the effects of flow rate of HTO and the height of PCM layer in the HSU, on three characteristic parameters of heat release—temperature effectiveness, heat release rate, and volumetric heat transfer coefficient. Consequently, we determined optimum conditions under which the HTO uniformly flowed in the PCM. When the HTO uniformly flow and the height of PCM was constant, the temperature effectiveness was high and the heat release rate was proportional to the flow rate of HTO. In addition, a high temperature effectiveness over 0.83 was observed even when the height of PCM was 0.2 m. Further, the average volumetric heat transfer coefficient increased with increasing the flow rate of HTO and decreasing the height of PCM. These results revealed that the direct-contact heat exchanger can rapidly, efficiently, and compactly release the latent heat of PCM provided that HTO uniformly flows.