Ansari Abolfazl, Kavousi Saman, Helfer Fernanda, Millar Graeme, Thiel David V
School of Engineering and Built Environment, Griffith University, Brisbane, QLD 4111, Australia.
Independent Researcher, Esteghlal Blvd., Shiraz 71757-43659, Iran.
Membranes (Basel). 2021 Apr 22;11(5):308. doi: 10.3390/membranes11050308.
Direct Contact Membrane Distillation (DCMD) is a promising and feasible technology for water desalination. Most of the models used to simulate DCMD are one-dimensional and/or use a linear function of vapour pressure which relies on experimentally determined parameters. In this study, the model of DCMD using Nusselt correlations was improved by coupling the continuity, momentum, and energy equations to better capture the downstream alteration of flow field properties. A logarithmic function of vapour pressure, which is independent from experiments, was used. This allowed us to analyse DCMD with different membrane properties. The results of our developed model were in good agreement with the DCMD experimental results, with less than 7% deviation. System performance metrics, including water flux, temperature, and concentration polarisation coefficient and thermal efficiency, were analysed by varying inlet feed and permeate temperature, inlet velocity, inlet feed concentration, channel length. In addition, twenty-two commercial membranes were analysed to obtain a real vision on the influence of membrane characteristics on system performance metrics. The results showed that the feed temperature had the most significant effect on water flux and thermal efficiency. The increased feed temperature enhanced the water flux and thermal efficiency; however, it caused more concentration and temperature polarisation. On the other hand, the increased inlet velocity was found to provide increased water flux and reduced temperature and concertation polarisation as well. It was also found that the membrane properties, especially thickness and porosity, can affect the DCMD performance significantly. A two-fold increase of feed temperature increased the water flux and thermal efficiency, 10-fold and 27%, respectively; however, it caused an increase in temperature and concertation polarisation, at 48% and 34%, respectively. By increasing Reynolds number from 80 to 1600, the water flux, CPC, and TPC enhanced by 2.3-fold, 2%, and 21%, respectively. The increased feed concentration from 0 to 250 [g/L] caused a 26% reduction in water flux. To capture the downstream alteration of flow properties, it was shown that the ratio of inlet value to outlet value of system performance metrics decreased significantly throughout the module. Therefore, improvement over the conventional model is undeniable, as the new model can assist in achieving optimal operation conditions.
直接接触式膜蒸馏（DCMD）是一种很有前景且可行的海水淡化技术。大多数用于模拟DCMD的模型都是一维的，并且/或者使用依赖于实验确定参数的蒸气压线性函数。在本研究中，通过将连续性方程、动量方程和能量方程耦合，改进了使用努塞尔特关联式的DCMD模型，以更好地捕捉流场特性的下游变化。使用了一个与实验无关的蒸气压对数函数。这使我们能够分析具有不同膜特性的DCMD。我们开发的模型结果与DCMD实验结果吻合良好，偏差小于7%。通过改变进料入口和渗透物温度、入口流速、进料入口浓度、通道长度，分析了包括水通量、温度、浓差极化系数和热效率在内的系统性能指标。此外，分析了22种商业膜，以切实了解膜特性对系统性能指标的影响。结果表明，进料温度对水通量和热效率影响最为显著。进料温度升高提高了水通量和热效率；然而，它导致了更多的浓差极化和温度极化。另一方面，发现入口流速增加也能提高水通量，并降低温度和浓度极化。还发现膜特性，尤其是厚度和孔隙率，会对DCMD性能产生显著影响。进料温度提高两倍分别使水通量和热效率提高了10倍和27%；然而，它分别使温度极化和浓度极化增加了48%和34%。通过将雷诺数从80增加到1600，水通量、CPC和TPC分别提高了2.3倍、2%和21%。进料浓度从0增加到250 [g/L]导致水通量降低了26%。为了捕捉流动特性的下游变化，结果表明，在整个模块中，系统性能指标的入口值与出口值之比显著降低。因此，对传统模型的改进是不可否认的，因为新模型有助于实现最佳运行条件。
