Theoretical And Experimental Investigation On Heat Transfer Enhancement Of Nanofluids

Nanofluid is a new class of heat transfer fluid which containing suspended metallic or non-metallic nanoparticles in traditional fluid. Nanofluids have potential used in many industrial sectors,such as energy,chemical industry,electrical power and microelectronics cooling,etc.In the paper,the preparation and the stability of ZrO₂-water,CaCO₃-water nanofluids and the study of transport properties of nanofluids were studied. The heat transfer and flow behavior were measured in the experimental system and compared with simulation results to ansysis the mechanism of the heat transfer of nanofluids.The nanoparticles and base fluids were directly mixed by ultrasonic bath,dispersant and controlling pH. With this metrod, several sampled nanofluids with different fraction have been prepared. Some factors of affecting the stability and evenness of nanofluids, such as the property of fluids, the dimension and the property of nanoparticle , interaction force for particle were discussed.Falling ball viscometer is applied to measure the apparent viscosity of nanofluids in this paper. The viscosities of some nanofluids are given. Some factors of affecting the apparent viscosity of the nanofluids, such as the volume fraction, the shape, the dimension and the property of nanoparticle, are discussed.Brown motion, the surface of the nanoparticle and nanoparticles aggregation affect the thermal conductivity of nanofluids.Convective heat transfer coefficient of two nanofluids were measured according to Re=3000¹7000.The experimental results show that the suspended nanoparticles remarkably increase the convective heat transfer coefficient and enhance the ability of the heat transfer.The heat transfer feature of nanofluids remarkably increases with the volume fraction, the property of nanoparticle and flow behavior.Mixture method is applied to simulate the flow and convective heat transfer of nanofluids in this paper. Some factors of affecting the heat transfer of nanofluids, such as temperature,velocity, turbulent kinetic energy and Nu were dicussed.The simulative results show that the convective heat transfer of nanofluids remarkably increases at the entrance of the tube. Some factors of affecting the heat transfer of nanofluids, such as, the dimension ,movement and the property of nanoparticle were discussed.