含空气蒸汽在下流水柱表面接触冷凝的压力影响分析

Analysis of pressure influence of steam and air contact condensation on the surface of downstream water column

含不凝气体的蒸汽直接接触冷凝在工业中应用广泛,冷凝参数对设备设计至关重要。数值模拟了蒸汽和空气在下流水柱表面的接触冷凝换热;分析了压力对下流水柱表面温度、空气质量分数的影响,以及凝结热流和凝结传热系数的变化规律。结果发现,下流水柱表面温度、凝结热流和凝结传热系数沿着流动方向下降,下流水柱表面空气质量分数沿着流动方向升高。随着压力增加,下流水柱凝结长度增加,在凝结长度末端,下流水柱表面空气质量分数高达90%以上,凝结热流和凝结传热系数均增加。下流水柱初始温度的升高会降低接触凝结传热系数和凝结热流。将计算结果和Celeta等的实验数据做了比较分析。

The direct contact condensation of steam containing non-condensable gas is widely used in industry,and the condensation parameters are very important to equipment design.The contact condensation heat transfer of steam and air on the surface of the downstream water column is numerically simulated.The influences of pressure on the surface temperature of the downstream water column and on the air mass fraction are analyzed,And the change law of condensation heat flow and condensation heat transfer coefficient is investigated.It is found that the surface temperature,condensation heat flow,and condensation heat transfer coefficient of the downstream water column decrease along the flow direction,and the air mass fraction of the downstream water column surface increases along the flow direction.As the pressure increases,the condensation length of the downstream water column increases.At the end of the condensation length,the surface air mass fraction of the downstream water column is as high as 90%,and both the condensation heat flow and condensation heat transfer coefficient increase.The increase in the initial temperature of the downstream water column will reduce the contact condensation heat transfer coefficient and condensation heat flow.