【摘要】 两相流载气蒸发是在蒸发器的垂直加热管中引入一种惰性气体,使液体的蒸发在气液两相界面上进行的过程.本文研究了载气蒸发的流型区域和传热规律,对载气蒸发的特性进行了机理分析,并以叠加模型关联了实验数据,获得了准数方程式.更多还原

【Abstract】 When the liquid is introduced into a vertical tube and heated to its boiling point, convective boiling occurs. If an inert gas is introduced at the bottom of the tube, it can be observed that the boiling vapor nuclei are not formed on the heating pipe wall and the evaporation of liquid takes place at the gas-liquid interphase instead. Such an operation is called Gas Carrying Evaporation(GCE).In this paper studied by visual observation and with an electric conductivity probe, the flow pattern transition was measured as a function of carrying gas flow rate, liquid rate and operating pressure and an empirical flow regime diagram was obtained. Moreover, the effects of various operating parameters on heat transfer in GCE were studied and the mechanism of the enhancement of heat transfer in GCE was analyzed.The following conclusions can be drawn from this study. In GCE,the heat transfer coefficient is higher than that obtained either in convective boiling or in gas-liquid two phase flow. It can be considered that there is a quick diffusion of liquid vapor at the initial instant with the result of lowering the gas-liquid interfacial temperature and enhancement of the heat transfer. The heat transfer in GCE may be considered as an overall effect of boiling, convective transfer and the enhancement by quick mass diffusion and can be correlated with dimensionless groups. The heating wall temperature will be lowered in GCE, so it can be applied to evaporation of heat-sensitive materials and to the evaporation of solutions which will form scales on the heating surface.更多还原