Flow and heat transfer characteristics of nanofluids in a liquid-cooled CPU heat radiator

Highlights: • Nanofluids as liquid-cooled CPU cooler heat exchanger working fluid. • To explore comprehensive performance of the nanofluid in the heat absorbing box. • Nanofluids make the CPU surface temperature decreased 4–18 °C to deionized water. - Abstract: The convective heat transfer coefficient and flow resistance coefficient of Cu-water and A1₂O₃-water nanofluids with a mass fraction of 0.1–0.5% was measured experimentally in a liquid-cooled central processing unit (CPU) heat radiator in the Reynolds number range of 400–2000. The results show that the cooling performance of a CPU heat radiator was enhanced significantly by applying the Cu-water and A1₂O₃-water nanofluids, and the surface temperature of the CPU chip decreased 4–18 °C compared with the deionized water. The convective heat transfer coefficient of nanofluids with a mass fraction of 0.1–0.4% was significantly higher than deionized water, and the convective heat transfer coefficient of Cu-water nanofluids was about 1.1–2 times the heat transfer coefficient of the DI water. The convective heat transfer coefficient of nanofluids with a mass fraction of 0.5% and 0.4% are close. Compared with deionized water, the flow resistance coefficient of the Cu-water and A1₂O₃-water nanofluids both increased to a certain degree; however, the increasing rate slowly lowered as the Reynolds number increased. Finally, a correlation which concerns the convective heat transfer coefficient and flow resistance coefficient was proposed for low concentration nanofluids in the CPU heat radiator. The proposed correlation and its calculated value agrees well with the experimental results.