(341y) Investigation of the Effect of Design Parameters and Operational Conditions on a Hollow Fiber Vacuum Membrane Distillation Module

Membrane-based technologies are among the most promising methods of water desalination. Among different membrane-based separation schemes, membrane distillation (MD) is emerging as one of the technologies with a potential for commercialization. Although there have been several studies and efforts in this area, MD still suffers from low permeate flux as well as high specific energy consumption. Among the different operational configurations, vacuum membrane distillation (VMD) has a very high potential of being designed and optimized to overcome some of the existing limitations. Here, we present our simulation results for a hollow fiber VMD module. We constructed a three-dimensional model and accounted for the heat, mass, and momentum transfer phenomena within the module. The effects of system and operational parameters on the total permeate flux of the system were studied. The modeling results showed that the diffusive flux through the membrane plays an insignificant role in the rate of water production. In contrast, convective flux accounts for nearly all the mass transport through the system. As a result, module design with enhanced convection through the membrane can result in a high-performance module. We estimate that modules with permeate flux as high as 300 liter/m² per hour can be realized by tuning the design parameter. Among different parameters, increasing the inner radius of the hollow fiber and reducing the thickness of the membrane have the most pronounced effect on the permeate flux. The operating conditions such as outlet pressure and feed temperature were also seen to have a significant effect on the permeate flux.