Experimental Study On Spray Cooling Of Alumina-based Nanofluids

With rapid economic development,high-power chips、high-end servers、large radars are becoming more and more powerful,and these devices generate more and more heat.The existing traditional heat dissipation methods are gradually unable to meet the needs,and nanofluids spray cooling is an emerging,efficient thermal control technology.Research on the spray cooling performance of nanofluids has become a hot spot in the field of experimental heat dissipation.In this paper,the spray cooling performance of alumina-based nanofluids is mainly investigated by the experimental method.First of all,a spray experiment platform is built,which can adjust many experimental parameters.The working fluid can be recycled in this system,and the spray experiment of deionized water is completed on the experimental platform.In the experiment,the different cross-section temperatures of the heat-conducting column were mainly collected,and the heat flux was calculated by Fourier’s law.In high wall temperatures region,deionized water with a large flow rate has a better heat dissipation performance than that with a small flow rate.The experiment also obtained the spray cooling curve under different flow pressures.Increasing the flow rate within a certain wall temperature range can promote heat dissipation,while increasing pressure has limited effect on heat transfer enhancement.For spray experiments,stable alumina-based nanofluids is necessary.The ratio of dispersant to nanoparticles is a key factor for the stable preparation of nanofluids.By experimental means,when the ratio is 1.25,the prepared fluid is relatively stable.On this basis,three kinds of alumina-based nanofluids were prepared and their stability was studied through spectrophotometry.The stability of alumina-based nanofluids of the same mass fraction deteriorates with time.At the same time,the transmittance of the sample supernatant of different mass fractions of alumina-based nanofluids is different,and the transmittance decreases as mass fraction increases.In order to study the difference of spray cooling effect between alumina-based nanofluids and deionized water,three different mass fractions of alumina-based nanofluids(wt 0.1%,wt 0.3%,wt 0.5%)were sprayed at different flow rates.In the low wall temperature region,the alumina-based nanofluids has a better strengthening effect on the cooling and heat dissipation process than the deionized water,and the larger the concentration of the alumina-based nanofluids has a higher heat dissipation heat flux.But in the high wall temperature region,the heat dissipation effect of alumina-water nanofluids is not always better than deionization,the effect of flow rate on the heat exchange process of alumina-based nanofluids is obvious.When the wall temperature is higher than 95 °C,the wall heat exchange process is mainly composed of two modes: nucleation boiling and liquid film evaporation.At medium and low flow rates(35 L/h,40 L/h),the deposition behavior of nanoparticles on the heating wall will weaken the heat dissipation effect.The heat dissipation heat fluxes of three different concentrations of alumina-water nanofluids(wt 0.1%,wt 0.3%,wt 0.5%)show the trend: slowly rise,steady stay,and gradually decrease.However,at high flow rates(45 L/h),the heat flux of alumina-water nanofluids increased with increasing wall temperature.