Heat Transfer Characteristics of Erythritol Slurry as Heat Medium for Medium and Low Temperature in Cooling Pipe

Abstract

We propose erythritol slurry as a heat transfer medium for unused energy utilization. In this study, heat transfer characteristics of erythritol slurry, with considering solidification and fixation of the solid on the cooling surface, must be understood to prevent any fatal trouble in the practical use. In the experiment, by using double tube heat exchanger, in which slurry flows in the inner tube and cooling water flows in the outer tube, heat transfer coefficient is measured under the condition the solidification is possible to be occur. It was found that the heat transfer coefficient of the erythritol slurry is smaller than the erythritol solution under the turbulent flow condition because of the fixation of the solid. Although enhancement of heat transfer coefficient with the turbulent transition was observed for solid fraction of 5 mass %, it was not observed for 10 and 15 mass %. The heat transfer coefficient increases with flow rate in the same trend with turbulent flow for 10 and 15 mass % even when Reynolds number is low. It was also found that both the heat transfer enhancement by the effect of phase change and the heat transfer suppression by the effect of fixation of the solid are more significant under cooling condition than under heating condition. The heat transfer enhancement by the effect of the phase change increases with the solid fraction until the solid fraction reaches about 10 mass%. It was also found that the heat transfer enhancement is larger than the increase in pressure drop by the effect of the solid particles. From the results, we proposed the model of flow and heat transfer of erythritol slurry in cooling pipe, and supposed supercooling affects the heat transfer characteristics.