预热-蒸发一体式降膜蒸发器三维参数分布

Three dimensional parameter distribution of preheating evapora-tion integrated falling film evaporator

中文关键词: 水平管降膜蒸发器  分布参数方法  海水淡化  传热系数

英文关键词: Horizontal tube falling film evaporator  Distributed parameter method  Seawater desalination  Heat transfer coefficient

中文摘要:

      针对欠饱和海水在蒸发器内预热、蒸发的过程，建立了分布参数模型，研究了管内蒸汽提前凝完对蒸发器内热力参数空间分布的影响。结果表明：预热区域的平均管外传热系数约为蒸发区域的80%；受管内蒸汽未达到出口前全部凝结的影响，蒸发器出口处的海水沸点升高（BPE）为入口处的38.83%，二次蒸汽流速平均值沿管长方向最大减小了14.8%，管外传热温差沿管长方向减小了6%；管间二次蒸汽压力增大使管外传热温差沿管列方向减小了12.2%；沿着管长方向，管内蒸汽逐渐凝结，该过程导致管外传热系数、海水盐度及BPE、二次蒸汽流速、海水饱和温度以及管外传热温差沿管排方向的梯度在管长节点较大处具有较小的值。

英文摘要:

      A distributed parameter model was established for the preheating and evaporation process of under-saturated seawater in the evaporator, and the effect of early condensation of steam in the tube on the spatial distribution of thermal parameters in the evaporator was studied. The results show that the average heat transfer coefficient outside the tube in the preheating area is about 80% of that in the evaporation area; Affected by the fact that the steam inside the tube has not fully condensed before reaching the outlet, the boiling point increase (BPE) of seawater at the evaporator outlet is 38.83% of that at the inlet. The average secondary steam flow rate decreases by a maximum of 14.8% along the length of the tube, and the temperature difference in heat transfer outside the tube decreases by 6% along the length of the tube; The increase in secondary steam pressure between pipes reduces the temperature difference of heat transfer outside the pipes by 12.2% along the direction of the pipe array; Along the length direction of the pipe, the steam inside the pipe gradually condenses, result-ing in smaller values for the heat transfer coefficient outside the pipe, seawater salinity and BPE, secondary steam flow rate, seawater saturation temperature, and the gradient of the heat transfer temperature difference outside the pipe along the direction of the pipe row at larger nodes in the pipe length.