3D printed triply periodic minimal surfaces as spacers for enhanced heat and mass transfer in membrane distillation

Abstract

3D printing is utilized to create different feed channel spacer designs aimed at enhancing the spacer performance specifically for membrane distillation (MD) application. The novelty is the use of mathematically developed triply periodic minimal surface (TPMS) as feed spacers. Five different TPMS based spacer designs were evaluated and benchmarked against the conventionally used net type spacer. The best performing TPMS spacer topology exhibited 60% higher water flux and 63% higher overall film heat transfer coefficient than the commercial spacer. The TPMS spacer designs also had a significant advantage over the commercial spacer when treating feed with high fouling potential such as brine solution. The advantages of TPMS spacers were the high throughput combined with sustained flux performance over increasing TDS concentrations ranging from 75,000 ppm to 100,000 ppm. The best performing TPMS spacer design was identified to have the highest surface area to volume ratio along with a design structure that caused relatively higher turbulence by disrupting the feed flow. Particle deposition tests were done using microspheres to visualize the impact of TPMS spacer design on dead zone formation. Pearson correlation coefficient showed that particle deposition is strongly correlated to the spacer voidage and its membrane contact area.