Researchers at the Manisa Celal Bayar University in Turkey have proposed using a skived-type aluminum heat sink (HS) to cool insulated gate bipolar transistor (IGBT) arrays in solar PV inverters.
In the study “Evaluation of the thermal performance of vapor chambers integrated skived fin heat sink for PV-inverter cooling under multi-heat source condition,” which was recently published in Case Studies in Thermal Engineering, the scientists explained that IGBT modules are responsible for around 55% of failures in semiconductor devices due to the heat they generate. “IGBT modules in the inverter are considered as heat sources with high heat flux (16.29 W/cm2),” they specified.
Compared to traditional HSs, the skive-type HS offers a higher fin height to gap ratio, which defines the ratio between the height of the fins and the distance between them. In the proposed system configuration, the vapor chambers (VCs) are integrated into the skived HS with a high aspect ratio of 20, which reportedly reduces heat dissipation resistance. In conventional HSs, the aspect ratio is commonly up to 10.
The VCs utilize water as the working fluid and are made with a sealed copper envelope and a sintered copper wick structure.
“The working fluid vaporizes by the application of heat on the evaporator side of the VC,” the academics further explained. “The vaporized fluid fills the vapor core and condenses over the top plate. The wick structure draws the condensate back to the evaporator section through capillary forces. The closed-loop evaporation and condensation process results in very high thermal conductivity values.”
To analyze the cooling performance of the new HS, the research team considered parameters such as the fin spacing, thickness, and aspect ratio. It also used isotropic and orthotropic thermal conductivity models to conduct a series of numerical simulations.
The analysis showed that, thanks to the presence of the VCs, the maximum temperature of the IGBT module can be lowered by about 6.63 C for an inlet air velocity of 7.5 m/s.
The researchers also found that the VCs help reduce maximum surface temperature with base plate thickness. The critical aspect ratio (height/spacing) value for the skived HS is obtained as 20, and there is no significant effect on the temperature drop by increasing aspect ratio after 20,” they added.
Specific information about potential production costs or cost increases compared to conventional cooling for PV inverters was not provided in the research work.
“It can be concluded that the skived HS with VC assistance promises better cooling potential for high-power electronics equipment compared to conventional HSs,” the academics concluded. “In addition, the optimization of the skived type HS under natural convection conditions can be realized in future works.”
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