Experimental Study On Boiling Heat Transfer Of Nanofluids

In recent years,the volume of the electronic device is becoming smaller and integrated,the heat concentration per unit area is serious,and the resulting heat dissipation problem is becoming more and more serious,how to achieve the efficient transmission of heat to ensure the safe operation of high-power electrical appliances,it has been plagued by the relevant areas of researches.The conclusion of study on the heat transfer enhancement of the vapor-liquid two-phase flow innanofluids is still controversial in the field of heat transfer,and because of its large demand in practical application,it promotes the relevant areas of national researchers to carry out experimental research and theoretical analysis,but most of them are limited to theoretical research,experimental research is relatively small.Therefore,this paper hopes to study the experimental mechanism of boiling heat transfer performance of nanofluids by means of experimental research,pave the way for the realization of more efficient heat transfer.In this paper,it was based on the review of the research and progress of nanofluidsboiling heat transfer at home and abroad,the experimental study on boiling heat transfer of nanofluids is carried out,and the heat transfer mechanism is discussed,which provides a reference for further enhancement of boiling heat transfer.Firstly,the nanofluidswith different compositions were prepared by two-step method,and the influence factors such as thermal conductivity and other physical parameters were analyzed theoretically.Then,the experimental device of boiling heat transfer of nanofluidswas designed and built,and combined with the existing and study of the more mature water boiling heat transfer curve,verify the reliability of the experimental device and repeatability.Then,the experimental scheme and experimental method are introduced,the experimental study on the boiling heat transfer performance of different nanofluids was carried out,the high speed camera was used to visualize the boiling heat transfer process.The changes of bubble in the boiling chamber and the relevant test data were recorded.And the upper wall surface of the heated copper column before and after boiling heat transfer was compared with SEM.The boiling heat transfer performance of different base fluid composition,particle concentration,nanoparticle size and nanoparticle type under different operating pressures was analyzed by the experimental data,bubble images,wall shape and other information.And then analyze the influence of the above factors on the boiling heat transfer performance of nanofluids and its mechanism.The experimental results show that:(1)In the low concentration range,the greater the concentration of nanoparticles,the more favorable the boiling heat transfer performance of nanofluids.The boiling heat transfer performance of the water-alumina nanofluids with the average of nanoparticles is 30 nm and the mass concentration is 0.001%,0.005%and 0.01% respectively.itincreased from left to right.(2)The boiling heat transfer performance of nanofluids is related to the types of nanoparticles,in the case of the same other conditions,the physical properties of nanoparticles,such as thermal conductivity,specific heatcapacity,density,viscosity and so on,will affect the boiling heat transfer performance of nanofluids.The boiling heat transfer performance of water-alumina nanofluids with an average particle size of 30 nm and a mass concentration of 0.005% is better than water-silica.(3)For the base fluid used to prepare the nanofluids,will also affect the boiling heat transfer performance of nanofluids.The average particle size of nanoparticles is 30 nm and the mass concentration is 0.005%.The boiling heat transfer performance of the nanofluids increased with the mass fraction of ethylene glycol in the mixed solution reduced.(4)In the range of experimental,the boiling heat transfer performance of the nanofluids becomingmore better with the smaller the average particle size of the nanoparticles reduced.The boiling heat transfer performance of water-alumina nanofluids with an average concentration of 0.005% and an average particle size of 30 nm is better than that of water-alumina nanofluids with an average particle size of 50 nm.(5)The working pressure of the test system has an important effect on the boiling heat transfer performance of the nanofluids.The experimental results show that the boiling heat transfer performance of nanofluids under low pressure conditions is better than that under high pressure conditions.