Thermal performance analysis of new bionic “fishbone” fins in a triplex-tube latent heat storage system with single cycle process

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Targeting the low thermal conductivity characteristics of energy storage materials in latent heat thermal energy storage (LHTES) systems, a novel bionic fish bone fin design is proposed in this paper, and the numerical simulation is employed to analyze the thermal performance of a system during single charging and discharging cycle. In assessing the system, consideration is given to the time required to complete a cycle, mean temperature change rate, and charging and discharging efficiency over the course of a cycle. The temperature response of each monitoring point within the system was first analyzed for fishbone fins of different curvatures and found that the 30° and 60° fishbone fins have the fastest heat transfer rates and shortest cycle times, respectively. Subsequently, the effect of fishbone fractal position on the thermal performance of the system was investigated. The results showed that the system achieves the best circulating thermal performance when the fishbone fins are positioned in the middle of the straight fins. An increase in the dimensionless position of the fins from 0.2 to 0.5 produced a reduction in the cycle time of 28.03 % and an increase in the energy transfer efficiency of 38.15 %. Finally, the shortest cyclic cycle and the fastest heat transfer rate were taken as the optimization objectives to optimize and predict the thermal performance of the system through the response surface method. The findings demonstrated that the system exhibited optimal thermal performance when the radian angle of the fishbone fin is 44.43° and the dimensionless position is 0.45. Compared to traditional rectangular straight fins, the optimized structure reduces the cycle time by 52.64 % and increases the average heat transfer rate by 101.58 %.