Performance analysis of the direct contact membrane distillation using sonication effect

Direct contact membrane distillation (DCMD) for desalination often suffers from membrane fouling, scaling, low permeate water flux and pore wetting. This study focuses on the integration of sonication with DCMD to mitigate these problems by enhancing mass flux and reducing temperature polarization. A computational fluid dynamic model has been developed for the evaluation of temperature polarization through sonication enhanced DCMD. The computational domain consists of two channels, i.e., feed and permeate. It has a length of 20 mm, with a height of 1 mm for each channel, and a membrane thickness of 130 µm. Laminar flow at a low Reynolds number is considered (Re 10), with feed and permeate flowing in a counter-flow arrangement at the same inlet velocity but different temperatures. The employed numerical model is unsteady non-isothermal governed by Navier–Stokes equations which are conjugated thermally with the polymeric membrane. The model is subjected to different sonication frequencies and amplitudes. It employs dynamic mesh in conjunction with temporal sound application with a very small-time step to solve the governing equations associated with the sonication effect. A sensitivity study based on the effect of different parameters on the performance of the direct contact membrane distillation is conducted. The parameters studied include the effect of sonication wave (amplitude and frequency), feed flow rate and feed temperature on temperature polarization coefficient (TPC) and mass flux. Results show that sonication definitely can ameliorate the DCMD performance seen as a gain in both TPC and mass flux.