Investigation on thermal performance of nanofluids in a microchannel with fan-shaped cavities and oval pin fins

In this paper, a combined structure of fan-shaped cavities and oval pin fins is designed for the rectangular microchannel heat sink with an aspect ratio of 2. Four structural parameters are investigated, including cavity height (hr), chord length (Ir), rib offset distance (S0) and rib height (Hf). Overall performance factor and total thermal resistance are used to reflect the microchannel performance. In the Reynolds number range of 132-531, the microchannel shows the best hydrothermal performance under hr of 0.05 mm, Ir of 0.2 mm, S0 of 0, and Hf of 0.1 mm. When the Reynolds number is 398, the overall performance factor of the microchannel with optimal parameter combination is 33% higher than that of a rectangular microchannel. Field synergy angle in the microchannel is calculated based on the field synergy principle. According to the KKL (Koo-Kleinstreuer-Li) model, the local thermal conductivity distribution of Al2O3 nanofluids is studied at different nanoparticle diameters. Moreover, the overall performance factors of the heat sink are investigated at several volume fractions of Al2O3 nanofluids. Under the Reynolds number of 132, the Nusselt number of 0.04 vol% nanofluid is 9.5% higher than the deionised water. Based on optimal structural parameters, compared with deionised water, Al2O3 nanofluid with a diameter of 10 nm and volume fraction of 0.04 further improve the overall performance factor of micro-channels by 5.8% and reduce the total thermal resistance by 2.9%.

Automated summary

In this paper, a combined structure of fan-shaped cavities and oval pin fins is designed for a rectangular microchannel heat sink. The effects of different structural parameters on the performance are investigated. The results show that the microchannel exhibits improved hydrothermal performance under the optimal parameter combination.