Improving the performance of air gap membrane distillation process using a developed tubular condenser compared to a flat plate condenser

Condensation has a considerable effect on the performance of air gap membrane distillation (AGMD) process. In this study, a novel module arrangement was successfully introduced with the aim of improving the condensation phenomena and consequently enhancing the efficiency. In this newly designed AGMD arrangement, the common flat coolant plate was replaced with several horizontal copper tubes that has been named tubular condenser. Coolant fluid was streamed inside the tubes and condensation occurred outside the tubes. To measure the performance of this new module, two types of polytetrafluoroethylen (PTFE) commercial flat sheet membranes supported by polypropylene (PP) non woven layer with different pore sizes were employed. To measure water permeation flux, laboratory prepared brackish water was introduced into the system at different temperatures, which were 40, 50, 60, 70 and 80 degrees C. The average flux produced by the system at 80 degrees C for a flat plate condenser with an equivalent air gap was 11.7 kg/(m(2).h); it increased up to 19.45 kg/(m(2).h) using a simple tubular condenser. To improve more, tubular condenser was developed using zigzag copper ribbons, enhancing the water permeation flux to 30.08 kg/(m(2).h). To realize the performance of developed tubular module, the effect of membrane pore size and air gap width as well as ribbons arrangement were studied.