Theoretical analysis and parametric investigation of an innovative helical air gap membrane desalination system

Abstract

A helical air gap membrane desalination (HAGMD) system is designed in the present study. The condenser is designed as a cylindrical shape with helical fins machined on the outer surface of a hollow copper condenser. A detailed theoretical model, studying heat and mass transfer in the HAGMD module, was developed. The theoretical model for a cylindrical system with fins is developed for the first time and is unique in the MD literature. Experimentation was carried out to examine the behavior of the HAGMD module under diverse design and operating conditions. The effect of cold flow rate, feed flow rate, feed temperature, the height of fins, the number of fins, and the length of the module is determined on the performance of the HAGMD system. Permeate flux and gained output ratio (GOR) were considered as the performance indicators of the system. Results showed that permeate flux increases with cold flow rate, feed temperature, feed flow rate, as well as number of fins, while the increase in height of fins negatively affects the flux. Theoretical model and experimental results are found to be in excellent agreement with only 6.7% of error which shows that the present theoretical model is excellent to predict the performance of any HAGMD system. For similar design parameters, the average flux increased by 135% for the finned HAGMD module, with 35 fins over the one with that only for 1 fin. Maximum experimental distillate flux is found to be 20 kg/m2 hr, and GOR is found to be 0.75.