Study On Heat Transfer Performance Of Special-shaped Fins Coupled With Phase Change Materials For Thermal Management Of Photovoltaic Cell

Due to the problem that the thermoelectric efficiency of the traditional solar photovoltaic（PV）cell system decreases with the increase of the working temperature of the PV panel wall,the coupling of metal fins and phase change materials（PCM）utilizes the high thermal conductivity of metal fins to make up for the defect of low thermal conductivity of PCM,which can improve the natural convection and effectively improve the thermal inhomogeneity of the PV wall temperature.However,the current metal fin structure used for phase change material system of solar photovoltaic cells is relatively single,and new fin structures with more efficient heat transfer are still relatively scarce.Therefore,the purpose of this study is to explore the geometry of metal fins with better heat transfer performance coupled with phase change materials for better thermal management of photovoltaic cells and to improve the photovoltaic conversion efficiency of solar photovoltaic cells.This study investigates the use of Cantor fractal fins coupled with PCM for thermal management of photovoltaic cells with different fractal levels at the same surface area and volume constraints by visualization experimental means.The experimental results show that the Cantor fractal fins form more quasi-secondary heat sources and enhance the convection and melting between the PCM.The transient molten liquid phase fraction increases with the number of fractal stages and the PV surface temperature decreases with the number of fractal stages.The optimal number of enhanced heat transfer fractal stages is 3,which results in a maximum temperature reduction of 10°C on the PV wall surface and a maximum increase of 15%in the total melting time compared to the finless condition.The performance of the horizontally aligned direction of fins under the same volume constraint is better than the vertically aligned direction,and increasing the number of fins is more advantageous.Further,numerical simulations are used to optimize the flat fin-coupled partitioned cavity structure,series of T-shaped fins and segmented fins.The results show that the single partitioned,finned and partitioned coupled finned structures all effectively enhance the heat transfer and natural convection of the system.The best structure is the partitioned coupled flat fins,which create two smaller natural convection zones and reduce the convection path,and the fins provide a secondary heat source for the PCM farther away from the heat flow wall.The overall performance of the system decreases with decreasing cavity inclination.The total heat transfer area of T-shaped structure fins and segmented structure fins are equal.The findings show that the T-shaped fins outperform the common rectangular fins,and the maximum photoelectric conversion efficiency is almost twice as high as that of the rectangular fin structure.The excellent fin structures are all characterized by being closer to the lower part of the cavity or the lower right phase change material.The segmented fins are mainly divided into two-segmented fins and four-segmented fins.In the two-segmented fin structure,the best structural parameter is the segmented fin horizontal length L₁of 10 mm,and in the four-segmented fin structure,the optimum angleβbetween two adjacent segmented fins is 150°.The best structural combination is a dichotomous cavity coupled with a quadratic fin.The segmented fins are closer to the lower right side of the cavity away from the heat source,where more quasi-secondary heat sources are formed,effectively improving the natural convection within the phase change material and improving the heat transfer performance.This study evaluates the effects of Cantor fractal,series T-shaped and segmented fin structures on the performance of PV cell systems in terms of melting rate,melting time,electrical energy efficiency and PV panel surface temperature.It provides a more feasible theoretical basis for the practical application of Cantor fractal,series T-shaped,segmented fins and partitioned cavity structures to the thermal management of PV cells.