Pool Boiling Heat Transfer Characteristics Of Micro-nano Composite Structures Based On Graphene

With the development of technology,both energy conservation and high performance equipment heat dissipation require much higher heat transfer enhancement technologies.Thanks to the development of micro/nano technology,a variety of micro-nano structures have been prepared and used to strengthen the pool boiling heat transfer.Graphene is the most thin known materials,and has high thermal conductivity and minimal thermal resistance.That makes it an ideal material for thermal conduction.This paper mainly studied the preparation of graphene oxide/nickel and graphene oxide/silver/nickel composite material,and their effects on pool boiling heat transfer.In the experiment,we put graphene oxide and silver nanoparticles into the electroplating solution.The diameter of silver nanoparticles is 20 nm,while that of the graphene oxide nanoparticles is about 0.5-3?m,and the thickness is 0.9-1.2nm.The compound electro-brush plate was taken to prepare nicel?graphene oxide/nickel and graphene oxide/silver/nickel composite on copper,and the surface contact Angle and roughness were tested before and after the treatment of stearic acid.According to the test results of scaning electron microscope and surface contourgraph equipment,in the electrodepositing process,graphene oxide broke the development of nickel,and contributed to the generation of new crystal nucleus.Different from the surface coated with nickel,graphene oxide/nickel and graphene oxide/silver/nickel surfaces have microporous structures and high roughness.This is because that the growth direction of nickel is different on graphene oxide and nickel.There are two types of heating surface in the experiments,a series of surface was treated with stearic acid,the other kind was not processed.In general,the surface treated with stearic acid have better heat transfer performance.The critical heat flux density of graphene oxide/nickel and graphene oxide/silver/nickel surface are 82.1% and 61.2% higher than that of nickel surface.After treated with stearic acid,they are 97.7% and 70.7%.As for heat transfer coefficient,those of graphene oxide/nickel and graphene oxide/silver/nickel surface are 40.7% and 63.1% higher than that of nickel surface.After treated with stearic acid,they are 133.7% and 78.3%.In general,the performance of hydrophilic surface is better than that of hydrophobic surface,but the heat transfer performance of hydrophobic surface is better in our experiment.That is because the roughness was reduced,and the thickness of porous structure was reduced after dealt with stearic acid.