Improvement of spacer performance in membrane distillation via an adaptive mesh lattice Boltzmann model

An adaptive mesh hybrid lattice Boltzmann method is developed to model fluid and heat transfer through geometries of complex three-dimensional shape and a wide range of length scales. The model is first validated against analytical solutions and independent numerical methods. It is then applied to the problem of membrane distillation where pure, cold water is produced from hot, dirty water by passing water vapour through a membrane. Spacer components are critical to enhance the temperature difference across the membrane and thereby increase the pure water production. We uncover a new, high performing spacer geometry which comes from the family of Triply Periodic Minimal Surfaces and represents a significant departure from known spacer geometries for membrane distillation. Through our hybrid lattice Boltzmann model we are able to show the new spacer yields large temperature drops at a wide range of flow rates and at comparatively low energy cost. Our numerical method is able to efficiently and accurately model complex geometries by adaptive meshing while also avoiding the need for time-consuming manual CAD pre-processing. • Adaptive mesh refinement, hybrid lattice Boltzmann method. • Fluid flow and heat transport are modelled. • New spacer geometries based on Triply Periodic Minimal Surfaces are uncovered. • New spacers show significantly better performance.