Membrane desalination (MD) is a thermally-driven separation process. The driving force in the MD process is the vapor pressure difference induced by the temperature difference across a hydrophobic membrane as a barrier. MD is a potential route to obtain high-quality fresh water from sea water or brine by using low-grade energy. It is important to estimate and predict the MD performance especially in terms of permeate flux under given conditions. This is very meaningful in MD plications. In this work, the MD performance was studied not only by varying the feed temperature but also by varying the coolant temperature in a lab scale AGMD system. The permeate flux and salt reject ratio were tested under various conditions. The mass transfer coefficient in porous membranes was studied in detail both theoretically and experimentally. A new approach to estimate the permeate flux was proposed based on the study of the mass transfer coefficient in MD systems. The estimation of MD performance in real applications can be much simplified based on this study. (C) 2016 Elsevier B.V. All rights reserved.