NaCl溶液静态闪蒸瞬态传热特性的实验研究

Experimental study on heat transfer characteristics of aqueous NaCl solution in static flash evaporation

对NaCl溶液静态闪蒸过程的瞬态传热特性进行实验研究。实验中NaCl溶液质量分数为0~0.26,初始液膜高度为0.1~0.4 m,初始过热度为1.5~40℃。结果表明:在不同的闪蒸时期,过热度大小对瞬态传热系数的影响不同。闪蒸的前期瞬态传热系数随着过热度的增加而减小;在闪蒸后期开始阶段,瞬态传热系数随着过热度的增加而增大;在闪蒸后期末尾阶段,过热度对瞬态传热系数影响不明显。瞬态传热系数的峰值随着初始液膜高度和浓度的增大而减小。在实验范围内给出瞬态传热系数的实验关联式,与实验值吻合良好。在闪蒸过程中,瞬态传热系数的大小显著影响沸腾形态的变化规律。

Experimental studies on heat transfer characteristics of aqueous NaC1 solution in static flash evaporation were carried out, with the mass fraction of aqueous NaCl solution varying between 0 and 0. 26, initial height of water film varying between 0. 1 to 0. 4 m, and superheat varying from 1.5 to 40 ℃. Results showed that at different stages of flash evaporation the effects of superheat on instantaneous heat transfer coefficient were different. At the early stage, instantaneous heat transfer coefficient decreased with the superheat. At the beginning of the late stage, instantaneous heat transfer coefficient increased with the superheat. At the end of flash evaporation instantaneous heat transfer coefficient was nearly irrelevant to superheat. Results showed that the maximum instantaneous heat transfer coefficient value decreased with the increases of the initial height and initial concentration of water film. A fitting formula for instantaneous heat transfer coefficient of NaCl solution was proposed, and it was in good agreement with experimental results in the experimental range. The boiling states were significantly affected by the transient heat transfer coefficient in static flash evaporation.