Investigation On Flow And Heat Transfer Performance Of Nanofluids In A Submerged Impinging Jet

With the high local heat transfer capacity, jet impingement cooling technique is considered as one of the most powerful cooling solutions for high-heat-flux removal. Although many investigations have been carried out in the area of jet impingement heat transfer over years, the applications in high-density electronic components are limited because of the low thermal conductivity of jet working fluids. The improvement of the thermal properties of jet working fluid may become a trick of augmenting heat transfer performances for the impinging jet system. An effective way of improving the thermal conductivity of fluids is to suspend nanometer solid particles in the carrier fluids, namely nanofluids. The purpose of this paper is to introduce the nanofluids into jet impingement cooling system as the working fluid. It is expected to improve jet impingement performance by the way of improving the thermal conductivity of fluids. The main research contents are the following.Firstly, nanofluids are prepared and the suspension stability is tested. In this paper, Cu-water nanofluids are prepared by classical two-phase method, in which Cu particles are directly joined into distilled water. In order to obtain the stabilized suspension, mixture is consumingly whisked and vibrated in an ultrasonic vibrator. With this method, several sampled nanofluids with different volume fraction have been prepared. The results of suspension stability tests show that the nanofluids prepared by this method have favorable decentralization property.Secondly, the heat transfer performance and flow features of nanofluids in jet impingement are studied. An experimental system has been build up to investigate the heat transfer coefficient and the pressure drop of nanofluids in a submerged impinging jet. The effects of such factors as Reynolds number, the distance between the jet outlet and the impingement surface, oblique angle, the volume fraction and dimensions of the suspended nanoparticles are discussed in detail. The experimental results show that the suspended nanoparticles remarkably increase the heat transfer coefficient of the base fluid. In addition, the pressure drop experiments indicate that nanofluids with smack particle volume fraction will not cause significant augmentation in pump power and it is suitable for practical application.Thirdly, considering both the effects of the suspended nanoparticles and the condition of impinging jet, a new type of the heat transfer correlation for nanofluids in a confined and submerged impinging jet has been proposed The good coincidence between the experimental data and the calculated values show that the correlation correctly describes the energy transport and can be used to predict the impinging jet heat transfer coefficient with nanofluids.