The Experimental Study And Theory Analysis Of N-pentane-Water Direct Contact Heat Transfer With Phase Change

Direct contact heat transfer as a core technology in the new energy-efficient heat exchanger is the focus of energy research.Due to no metal heat transfer surface,direct contact heat transfer holds the advantages of little heat transfer resistance,high heat transfer coefficient,simple structure,little corrosion that traditional heat transfer doesn’t hold.Using direct contact heat transfer technology can reduce the heat transfer temperature difference and increase heat transfer efficiency of heat exchanger.Thus,this work is focus on the real heat transfer temperature difference,the heat transfer mechanism of drobble evaporaztion,the heat transfer performance of heat exchanger.The purpose of this work is to provide a basis study for improving the heat transfer efficiency of direct contact heat exchanger,and provide theoretical guidance for enhancing heat transfer technology.First of all,this paper presents a new experimental method to study the pentane-water direct contact evaporation heat transfer through constructing an unchanged heat transfer area with a closed-circuit experiment device.the speed of water at various points on the pentane-water liquid-liquid direct contact interface are uniform,which can accurately determine the influences of water flow velocity on the heat transfer coefficient and heat transfer temperature difference.By using infrared thermal image,the real temperature of water surface on direct contact heat transfer interface could be measured,the results show that the real heat transfer temperature difference is far less than the traditional algorithm of heat transfer temperature difference.The results reveal that the heat transfer resistance are mainly concentrated in bulk and interface water,which is the mechanism of mixing degree.Secondly,the evaporation heat transfer of n-pentane drobbles in continuous phase of wate in the two-dimensional column is studied by using the method of stroboscopic imaging.to study.The drobbles size distribution at different n-pentane inlet flow rate,water temperature and different height of 2D column is studied by using statistics method.The Sauter mean diameter of n-pentane drobbles,evaporation rate,drobbles rising velocities,n-pentane-water liquid-liquid interface area of drobbles,holdup and heat transfer coefficient are studied at different experimental conditions.Combined with infrared thermal image method to determine the real heat transfer temperature difference to reveal the mechanism of direct contact heat transfer.Finally,a pentane-water direct contact heat exchanger system is set up.the influences of dispersed phase pentane inlet flow rate,water temperature on the volumetric heat transfer coefficient are investigated.The heat transfer mechanism are analyzed in detail based on the influence factors of direct contact heat exchanger heat transfer performance compared with packing heat exchanger.