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首页> 外文期刊>Arabian Journal for Science and Engineering >The Effect of Spacer Orientations on Temperature Polarization in a Direct Contact Membrane Distillation Process Using 3‑d CFD Modeling
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The Effect of Spacer Orientations on Temperature Polarization in a Direct Contact Membrane Distillation Process Using 3‑d CFD Modeling

机译：3d CFD模型在直接接触膜蒸馏过程中间隔物取向对温度极化的影响

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摘要

Membrane distillation is an emerging technology that uses hydrophobic membranes to separate nonvolatile solids from liquids. The vapor pressure gradient between the feed and the permeate sides drives the process. Low-grade thermal energy is used to heat feed water and create a pressure gradient. A large vapor pressure gradient across the membrane surfaces results in high permeation rates. The feed spacer is an important element of the membrane module that forms channels for feed and permeate flow. A good feed spacer design helps improve permeation. In this paper, 3-d CFD simulations are carried out for spacer-filled channels, and the effect of inlet velocity, filament orientation and spacing on heat transfer is studied. Temperature polarization is used as the parameter for heat transfer performance evaluation. Shear stress and temperature polarization index have been calculated for different spacer orientations in a direct contact membrane distillation process. The results show a major influence of the studied parameters on temperature polarization and shear stress. A comparison of 2-d and 3-d analyses reveals that the average shear stress in the two approaches is nearly the same, but the standard deviation of shear stress is lower for the 2-d case. Similarly, the average value and the standard deviation of temperature polarization index are lower than those obtained in the 3-d analysis. The findings also show that for staggered axial filaments, the temperature polarization index distribution is more uniform suggesting that such orientations are more suitable for enhancing heat transfer in a membrane distillation process.
机译：膜蒸馏是一种新兴技术，它使用疏水膜从液体中分离出非挥发性固体。进料侧和渗透侧之间的蒸气压梯度驱动该过程。低等级的热能用于加热给水并产生压力梯度。跨膜表面的大蒸气压梯度导致高渗透率。进料隔片是膜模块的重要组成部分，它形成了进料和渗透流的通道。良好的进料垫片设计有助于改善渗透性。在本文中，对间隔物填充的通道进行了3-d CFD仿真，并研究了入口速度，细丝取向和间距对传热的影响。温度极化用作传热性能评估的参数。在直接接触膜蒸馏过程中，已针对不同的间隔物取向计算了剪切应力和温度极化指数。结果表明，所研究参数对温度极化和切应力的主要影响。 2-d和3-d分析的比较表明，两种方法的平均剪切应力几乎相同，但是对于2-d情况，剪切应力的标准偏差较低。类似地，温度极化指数的平均值和标准偏差低于在3-d分析中获得的平均值和标准偏差。研究结果还表明，对于交错的轴向长丝，温度极化指数分布更均匀，这表明这种取向更适合于增强膜蒸馏过程中的传热。

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