Numerical Investigation of Forced Convection Flow of IManofluids in Rotating U-Shaped Smooth and Ribbed Channels

摘要

The impact of the nanopanicles and ribs on the thermal performance of the rotating U-type cooling channel are investigated for turbulent forced convection flow of nanofluids. The nanofluids are provided by the inclusion of the nanoparticles of TiO_2 and Al_2O_3 in water as the base fluid, namely, water/Al_2O_3 and water/TiO_2 nanofluids mixtures. The simulations are performed for three-dimensional turbulent flow and heat transfer using an RNG κ-ε turbulence model for Reynolds number range of 5000 to 20,000. To show the effectiveness of the ribs and nanofluids, three criteria are employed: heat transfer enhancement, pressure drop or power consumed, and the thermal performance factor. It is found that the contribution of turbulence promotion in heat transfer enhancement of the ribbed channel is more effective than that of enlarging the heat surface area. The results show that using ribs at the lowest Reynolds number and utilizing nanofluids at the highest one provide high heat transfer rate and thermal performance. At the middle Reynolds numbers, the effects of these two methods on heat transfer enhancement are relatively close to each other. In this case, if the pumping power is the main concern, using nanofluids is recommended due to providing a smaller pressure drop penalty.