Experimental analysis of a novel helical air gap membrane distillation system

Abstract

Membrane distillation presents one of the feasible solutions to fresh water problems. The present study aims to develop an innovative helical air gap membrane distillation (HAGMD) system and to analyze its behavior under different operating conditions. In this design the condenser is made up of a cylindrical copper tube with continuous helical fins over it, that increases the total available condensation area by almost 45% and enhances the overall heat transfer throughout the module. The presence of fins in the gap also reduces the total air gap width by almost 64% and therefore improves the flux production. A detailed experimental analysis is carried out for a better understanding of the underlying phenomenon. The effect of feed water temperature, feed flow rate, cold flow rate, coolant temperature and feed salinity on the performance of HAGMD is investigated experimentally. The analysis shows that the finned condenser results in very high flux. The maximum flux obtained from the system was 20 kg/m2 hr with feed of 5 g/liter salinity and a diving force temperature difference of 45 °C. HIGHLIGHTS Helical air gap membrane distillation system is developed.; Condenser is modified with provision of helical fins on its outer surface.; Enhanced condenser surface area results in higher flux.; At higher flux production rate, module acts as a conductive helical gap MD system.; A high value of flux of 20 kg/m2 hr is achieved.;

Keywords

• air gap membrane distillation
• cold flow rate
• cylindrical module
• flux
• helical fins