Comparative performance assessment of direct contact membrane distillation with and without localized heating

In the present study, a comprehensive investigation of direct contact membrane distillation with and without localized heating using an effectiveness-number of transfer units (ε-NTU) approach is presented. In addition, the effect of various operating parameters on DCMD performance has been studied. It can be inferred from the analysis that feed solution temperature, membrane porosity, pore diameter and thickness of membrane are the prime influential parameters in determining DCMD performance in terms of distillate flux, gain output ratio (GOR), specific energy consumption (SEC) and overall efficiency. An 80 % increase in feed temperature has resulted increase in permeate flux from 3.1 kg/m²-h to 23.3 kg/m²-h in without localized heating case and from 15.8 kg/m²-h to 73.2 kg/m²-h with localized heating configuration. However, the inclusion of localized heating has increased the distillate flux 2.13 times at 90 °C feed temperature. Furthermore, by increasing the membrane porosity by 50 %, the distillate flux is enhanced from 3.1 kg/m²-h to 11.37 kg/m²-h and from 15.8 kg/m²-h to 57.64 kg/m²-h in the cases of no localized heating and with localized heating respectively. Additionally, the results of the mathematical model suggest a design and operating framework for optimum DCMD performance to minimize temperature and concentration polarization.