An experimental study of flash evaporation from liquid pools
An experimental study of flash evaporation from liquid pools
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DOI：
10.1016/0011-9164(87)90130-5
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发表时间：
1987-11
期刊：
影响因子：
9.9
通讯作者：
S. Gopalakrishna;V. Purushothaman;N. Lior
中科院分区：
文献类型：
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作者：
S. Gopalakrishna;V. Purushothaman;N. Lior
这项研究的目的是在实验的基础上加深对池中闪蒸的理解，并建立无量纲形式的水蒸气释放总量和水蒸气产生率(两者都是无量纲形式)与控制该过程的主要无量纲参数：雅各布数(JAP)、普朗特数(Pr)、无量纲静水头(Δp/H)和盐浓度(C)的经验关联式。这项工作是在海水淡化厂和开式循环海洋热能转换所特有的参数范围内完成的。实验使用淡水和盐水(3.5%氯化钠浓度)，初始温度为25°C-80°C，闪蒸温差为0.5°C-10°C，水池深度分别为6.5“(165 Mm)、12”(305 Mm)和18“(457 Mm)。闪蒸质量随无因次参数变化的预测精度在7.5%以内。采用了新的时间尺度τ=(σ/Δp)2/α1(其中σ=表面张力，α1=液体的热扩散系数，Δp=液体与汽相空间的压差)。使用该时间刻度的闪蒸速率的表达式显示出±68%的离散度。闪蒸质量的渐近值随Jakob数增大而增大，随熔池深度略有增大，随液体Prandtl数增大而减小。比较结果表明与实验值吻合很好，但低估了从其他实验获得的数据。
The objective of this study is, based on experiments, to improve the understanding of flash evaporation from pools, and to develop empirical correlations of the total quantity of vapor released and the rate of vapor generation (both in non-dimensional form) as a function of the primary nondimensional parameters which govern the process: the Jakob number (Jap), Prandtl number (Pr), a dimensionless hydrostatic head (Δp/H), and the salt concentration (C). The work was done in the range of parameters characteristic to desalination plants and to open-cycle ocean-thermal energy conversion. Experiments were performed with fresh water and with saline water (3.5% NaCl concentration), for initial temperatures from 25°C – 80°C, flash-down temperature differences from 0.5°C – 10°C, and pool depths of 6.5″ (165 mm), 12″ (305 mm) and 18″ (457 mm). The prediction of flashed mass as a function of the nondimensional parameters is accurate to within 7.5%. A new time scale τ = (σ/Δp)2/α1, (where σ = surface tension, α1= thermal diffusivity of the liquid, and Δp = pressure difference between the liquid and the vapor space) was employed. The expressions for the rate of flashed steam using this time scale show a scatter of ± 68%. The asymptotic value of the flashed mass increases with Jakob number, increases slightly with pool depth, and decreases with increasing liquid Prandtl number. The comparisons show very good agreement with the experimental values, but underpredict the data obtained from other experiments.