加热面朝下的池式过渡沸腾实验研究

Experimental Study on Pool Transition Boiling with Downward Facing Heated Surface

在常压下,对宽度为2.2、2.6、3.0、3.2、13.0mm水平小间隙内加热面朝下池式沸腾进行了实验研究,得到了各间隙下加热面朝下池式沸腾的沸腾曲线。与常规池式沸腾曲线比较发现,小间隙内加热面朝下池式沸腾换热能力远低于加热面朝上池式沸腾换热。运用原始实验数据分析了壁面过热度ΔTw和水平间隙δ对过渡沸腾换热性能的影响。结果表明:Nu数随ΔTw的增大而减小;整体上Nu数随δ的增大而增大,但在非常小的间隙范围内,Nu数随δ的增大会有局部下降趋势。

Experimental study was conducted to examine the pool boiling occurring on a relative large downward facing surfaces confined space with width of 2.2, 2.6, 3.0, 3.2 and 13.0mm, respectively, at atmospheric pressure using water as the working fluid. The boiling curves of distilled water with downward facing heated surface were obtained. The heat flux on downward facing heated surface is less than one tenth of that on upward facing heated surface. The effects of wall superheat, △Tw, and gap size, δ, on transition boiling were also analyzed. The results show that Nu decreases with the increasing of △Tw under transition boiling condition. And increases generally with the increasing of gap size, δ, though there is a small peek on Nu-δ curve in narrow gap size area.