Performance analysis of tubular membrane distillation modules: An experimental and CFD analysis
Chemical Engineering Research and Design
School of Engineering
This study presents a comprehensive theoretical and experimental analysis on the performance of tubular thermal-driven membrane-based distillation (MD) modules considering the changing nature of thermo-physical properties of feed and permeate streams. Moreover, important parameters such as the contribution of each membrane tube in the water productivity of the module, which has not been explored in previous studies, are analysed and discussed. A three-dimensional Computational Fluid Dynamics (CFD) model was developed considering conductive and convective heat transfers, mass transfer, and phase change processes. The model was validated using the data from an experimental rig that was designed and manufactured for this purpose. The results indicated that membrane tubes in the MD module have various levels of contribution to the water production depending on their position in the module. Compared to the membrane tubes located closer to the centre and perimeter of the module, the membrane tubes located in the middle had higher water productivity. The water productivity was not sensitive to the feed stream mass flow rate as long as the heat transfer coefficient to flow velocity ratio was beyond 1250 Ws/m3°C. For ratios below 1250 Ws/m3°C, the water productivity became extensively sensitive to the mass flow rate. The results also showed that turbulence enhancement at some regions within the module, especially the permeate channels, could noticeably improve the water productivity, and hence has an enormous potential to increase the overall efficiency of the MD modules. The results suggested that operating the tubular MD modules in the transition and turbulent regions is favourable due to its significant contribution to the enhanced water productivity of the system.