Analysis of enhanced heat transfer characteristics of finned triplex-tube phase change heat storage unit

Phase change heat storage technology plays an important role in using industrial waste heat and solar energy to solve the imbalance between supply and demand between heat energy and users. Due to the limitation of the physical properties of the phase change material, there are still problems such as low heat storage rate and uneven melting during heat storage and melting. In this paper, the effects of different parameters (number of fins, length, thickness, eccentricity and fin arrangement) of adding longitudinal fins on the heat storage performance of triplex−tube phase change heat storage unit were simulated by FLUENT software under the action of natural convection. The results showed that the heat exchange area was increased compared with the ordinary casing heat storage unit, and the time required for all the phase change materials to melt was shortened. Under the same number of fins, the length and thickness of the fins were the main factors affecting the heat storage unit and the average heat storage rate, when the fin length accounted for 50% of the radial length of the phase change material area, the melting speed of the heat storage unit was significantly accelerated and the heat storage and average heat storage rate were higher. Through the optimization design, it was found that the downward offset distance e of the inner tube had a significant effect on the melting process of the phase change material, and the heat storage unit with short eccentric distance took the least heat storage time, compared with the smooth tube heat storage unit, the melting rate of the phase change material was increased by 48.5%, and the heat storage time was extended if the offset distance was too long. Through the arrangement of the outer fins at the bottom of the infill heat storage unit, the melting process of the heat storage unit was accelerated to varying degrees, and the overall heat storage rate was improved compared with the original fin structure. © 2024 Chemical Industry Press Co., Ltd.. All rights reserved.