Augmenting the distillate water flux of sweeping gas membrane distillation using turbulators: A numerical investigation

Abstract

The enhancement of distillate water obtained from sweeping gas membrane distillation (SGMD) is rarely discussed in published works compared with other membrane distillation (MD) configurations, although it has the lowest thermal losses and does not need vacuum sealing. The present study aims at augmenting the distillate flux of SGMD modules by adding wires (turbulators) that work as turbulence promoters in the sweeping gas channel. A mathematical model was developed to simulate the transport processes of the distillate flux, considering the basic conservation equations for a hydrophobic polytetrafluoroethylene membrane layer, and the feed and air channels. Deviations of less than 10% were reported using experimental data of a pilot-scale module. The results showed that applying turbulators can reduce the vapor concentration polarization at the membrane–gas interface, leading to a considerable enhancement in the distillate flux. The effect of turbulators arranged in inline and staggered schemes with different diameters and membrane–turbulator gaps was numerically investigated. At feed temperatures of 60 °C and 40 °C, the SGMD module using turbulators produced distillate flux of 13.85 kg h−1 m−2 and 4.97 kg h−1 m−2, providing 34.3% and 39% increases over the cases without turbulators, respectively. This increases the potential use of low-carbon technologies to heat the SGMD feed.