Direct contact membrane distillation (DCMD) module was operated with three flat sheet commercial membranes (PTFE/PP 1.0, PTFE/PP 0.45, and PTFE/PE 0.45) under various operating conditions. High flux was observed when the PTFE/PP 1.0 membrane was used and there was no membrane wetting when the feed concentration was up to 3.0 M as NaCl. In order to understand the relationship between membrane characteristics and operating conditions, the heat and mass transfer models were employed. Instrumental analyses (SEM, porosimetry and contact angle analysis) were carried out for the membrane characteristics and thermo-hydrodynamic parameters were calculated under given experimental conditions. High flux of PTFE/PP 1.0 membrane was thermodynamically possible because the flow in the feed side was not fully developed in the water channel of the module. The membrane characteristics, such as pore-size of active layer and porosity and thickness of support layer were also attributed to a high flux of PTFE/PP 1.0 membrane. (C) 2014 Elsevier B.V. All rights reserved.