Experimental Investigation On The Heat Transfer Characteristic Of Mixtures At Porous Structured Surface

The self-wetting fluid with special interfacial tension characteristics,i.e.,the highcarbon alcohol aqueous solution,can significantly enhance the critical heat flux of the pool boiling.The study of nuclear state boiling mainly relies on the understandings toward the gasification core and boiling heat transfer mechanism.However,the boiling phenomenon is a complex unsteady,trans-scale and multi-physics coupling heat and mass transfer problem,with the mechanism that has not been fully revealed.Currently,the problems of one-sidedness and limitations are existed in studies on boiling heat transfer model.Meanwhile,it is difficult to perform visualization study on the internal flow,especially the separation of porous media internal bubbles by virtue of the traditional visualization means.Summary and innovation are also lacked in the boiling experiment of high-carbon alcohol aqueous solution in porous media that the surface tension changes along with the change of temperature.In this paper,the wall temperature is obtained based on the linear temperature distribution model of one-dimensional heat conduction direction,besides,a set of wall temperature measurement,bubble visualization and steady flow steady current heating test sands are also set up.On the basis of the above,the experimental observation of boiling heat transfer between the deionized water and the high-carbon alcohol aqueous solution is also realized in different sizes,micro channels that composed of different layers of copper balls,and porous structure composed of different PPI(number of pores per unit inch)foamed copper.The main contents include the establishment of boiling experiment system,reasonable determination of heating conditions,temperature measurement check,measurement of physical properties and experimental postprocessing.In the experiment,an open type pool boiling experiment system was adopted,and high-carbon alcohol fluids with different mass fractions were used as working medium,to study the effect of the diameter,layer number,stacking mode of copper beads,the PPI and thickness of copper foam and the mass fraction of the alcohol solution on the nuclear state pool boiling heat transfer characteristics of working medium in the porous structure.The results were compared with the situation of deionized water.Limited by the heater's rated power,the wall superheat could not reach or approach the responding regions of critical heat flux.Visualization study that conducted on foamed copper with the different sizes,layers of copper balls accumulation and different PPI through the image acquisition system was mainly manifested in the observation of bubble behavior and the boiling curve in the nuclear state boiling area.