Theoretical and experimental studies of flux enhancement with roughened surface in direct contact membrane distillation desalination

A new design of direct contact membrane distillation (DCMD) using roughened-surface flow channel for enhancement of heat transfer was proposed for increasing the pure water productivity in saline water desalination. The roughened surface was fabricated using siphonic-blasting with aluminum oxide (Al2O3) sand grains and arc spraying for Ni film coating. Experimental study has demonstrated its feasibility and up to 37% of performance enhancement was obtained for the experimental system. A mathematical model considering heat and mass transfer mechanisms has been developed and incorporated with experimental data for evolving a correlation for a heat transfer coefficient correction factor. The correlation is expressed as relative roughness and can be used for predicting the heat transfer coefficient for roughened-surface channels. Considering the tradeoff between the flux enhancements at the expense of energy consumption, an optimized level of roughness can be determined.