Experimental Investigation For The Effect Of Rough Tructures On Pool Boiling Heat Transfer

As a widely-used technology in industry, boiling heat transferoccupies a very important position in the area of metallurgy, chemicalindustry, power and energy. Especially after the proposition of the MooreLaw, the problem of the cooling of electronic chips is becoming more andmore imminent. Because of its small footprint and high heat transferefficiency, boiling heat transfer has attracted the attention of the scholarsall over the world. This paper focus on the influence of rough surface onpool boiling heat transfer, conducted the correspond experiments andanalysis, provided strong bases for the further improvement of heattransfer.Firstly this paper designed and built the pool boiling heat transferexperiment system, and carried out the experiments on irregular fractal surfaces and regular wave-shaped surfaces.In the study of the characterization of fractal surfaces, we used twomethods, including the power spectrum function method and the structurefunction method. Through comparisons, we found the relations betweenthe machining and the fractal parameters of surface profiles and came intothe conclusion that for the machined surfaces involved in this paper, thepower spectrum function is more accurate.The results of the boiling experiment on irregular fractal surfacesshowed that the heat transfer coefficient of the heated surfaces did notgrow with the Ra, it is more accurate to explain the boiling phenomenonwith fractal parameters. On CHF research, the critical wavelength ofTaylor instability did not only suffer the influence of physical parametersof the fluids, but also suffer the influence of the surface geographystructure. For the wave-shaped surfaces adopted in this experiment, theshorter the surface structure wavelength, the shorter the critical wavelength,and the higher the critical heat flux. The experiments also showed thatrough surfaces can increase the boiling heat transfer coefficient and thecritical heat flux at the same time. The mechanism of the increase of CHFis not only caused by the growth of the heated area, but also caused by thechanges of the critical wavelength of the boiling surface.