Pool Boiling Heat Transfer Characteristics Of H-BN Nanofluid

With the development of industrialization,energy consumption has been increased dramatically,and the problem of energy shortage has become increasingly prominent.Increasing energy efficiency and energy conversion efficiency is an effective measure to mitigate current energy shortages.Due to the high heat transfer efficiency,boiling heat transfer has been used widely in nuclear power,solar energy,low temperature industry and other fields.In recent years,the electronic circuit integration has developed rapidly and the power of electronic components has increased in a large scale.As a result,the problem of electronic chip cooling becomes a widespread concern.Boiling heat transfer has lots of advantages,such as small space occupation,high heat efficiency and so on,which provide a method to deal with the problem of the highly integrated cooling system.This paper aims to study and analyze the boiling heat transfer performance and the effect of micro-nanostructures on the boiling heat transfer performance of nanofluids,thus providing experimental basis for further intensified on heat transfer.The details of the work and conclusions are as follows:(1)In this paper,a pool boiling experiment system was designed and constructed,and the experiment of h-BN nanofluids boiling heat transfer was carried out on smooth surface,microchannels structure,nano-structure surface and micro-nanomete composite structure respectively.(2)In the study of boiling heat transfer characteristics of smooth surfaces,single bubble motion,such as nucleation,growth and detachment,was observed and recorded by high speed photographers,and the bubble kinetic analysis was carried out.It showed that the diameter of the bubble increases first in the process of growth,then stayed stable,and finally reduced,while the height kept the tendency of growth,and fell sharply after the departure of the bubble.In addition,the behavior of lateral and longitudinal cohesion between adjacent bubbles was also analyzed.(3)The prepared h-BN nanofluids and GO nanofluids showed excellent dispersion,and their physical parameters,such as thermal conductivity,viscosity and surface tension had been measured.The results showed that adding the h-BN nanoparticle led to an increase in thermal conductivity and viscosity,but a decrease in surface tension.(4)The critical heat flux of boiling heat transfer was obviously improved in both of the h-BN nanofluids and GO nanofluids.Compared with deionized water,the critical heat flux density of h-BN nanofluids with a 0.1wt% concentration was enhanced by 69%,reaching 1801.61 kW/m2,while that of the GO nanofluids with a 0.001wt% concentration was enhanced by 53.8%,reaching 1636.15 kW/m2.(5)Microlayer evaporation on the heat transfer surface resulted in an increase in the local concentration of nanoparticles and a dynamic equilibrium process of deposition,deposition and deposition of nanoparticles,effectively inhibiting the formation of gas film and increasing the critical heat flux.(6)The boiling heat transfer performance of nanofluids was enhanced by the micro-channel structure of the heat transfer surface,and The HTCmax and CHF were increased by 516.1% and 87.1% respectively,reaching to 3370.77 k W/m2? 481.7 kW/(m2·K)respectively.Due to The deposition of nanoparticles on the micro-channel structure surface,the effect of capillary wicking action was enhanced and the transition from super hydrophobic property to super hydrophilic was found.However,the boiling heat transfer performance of nanofluids deteriorates.This was because the nanoparticle deposition blocked the nanoscale pores of the heat transfer surface,and the gas barrier formed in the pores,thus reducing the boiling heat transfer performance.