Development of membrane distillation powered by engine exhaust for water desalination

To address water shortage in arid areas and make use of waste heat, an experimental investigation is presented for a novel system of air gap membrane distillation unit driven by an engine exhaust heat source for the development of an on-board car water desalination. The design of the gas-to-water heat exchanger is presented and optimized. The system’s performance, governed by the achieved feed water temperature and measured by the output vapor mass flux, is evaluated with time under varying operational parameters, including engine load, engine speed, and feed water flow rate, with the analysis of production cost for economic viability. Experimental results revealed that higher engine loads and speeds lead to rapid temperature increase of the feed water, enhancing the efficiency of the membrane distillation process and increasing the permeate flux. Notably, a maximum permeate flux of 45 kg/m²h was achieved after 40 minutes of operation. A minimum production cost of 3.2 $/m³ is estimated at an engine load of 35 N.m. With production costs ranging from 3.2 to 5.8 $/m³, the proposed system emerges as a highly competitive option when compared with other membrane distillation systems driven by waste heat in literature. This study underscores the potential of utilizing waste heat from car engines for cost-effective and sustainable water desalination, paving the way for further development and implementation of the system as a mobile desalination unit for different applications.