Abstract
The effect of the input dynamics on the membrane distillation performance is studied employing an experimentally validated model. Alteration of the cold stream flow rate relative to the hot stream flow rate demonstrated a profound impact on the process dynamics, hydrodynamics, and heat-transfer mechanism. The process exhibited a variable dynamic response to fluctuation in feed temperature and flow rate. For example, the fundamental time constant can be from 0.3 min for step changes in the feed flow rate orating at feed temperature of 50 degrees C to 18 min for step changes in the feed temperature operating at a flow rate of 500 L/h. Forcing both flow rates as opposite rectangular waves indicated enhancement of the accumulated gain output ratio (GOR) and the recovery ratio (RR). On an accumulative basis, GOR can improve by 60% and RR by 80%. Furthermore, decreasing the cycling frequencies of both flow rates can further improve the performance. Maximum performance enhancement was achieved when an equal period of oscillation of 5 min is utilized for both streams where GOR approaches 1 and RR 16%.