The direct contact membrane distillation(DCMD) device is a simple design of MD systems in which both the cold stream and hot stream are kept in direct contact with the membrane. The advantages of DCMD lie in its simple configuration, the need for only small temperature differences and nearly 100% salt rejection. In this study, the DCMC process are performed at middle temperature operation (about 40 °C to 70 °C) of hot inlet stream associated with a constant cold stream inlet temperature(about 25 °C). A concurrent flat-plate device was constructed and carried out to verify the theoretical prediction of pure water productivity on saline water desalination. The purposes of this study are (1) to develop a new semi-empirical expression of the membrane coefficient from the results of the pure water production of the experiment and the mathematical modeling; (2) to study a new design of double-effect direct contact membrane distillation system and develop a two-dimensional mathematical model and propose a general numerical method for solving this complex mathematical model in predicting pure water productivity in membrane distillation systems. The numerical results from the mathematical modeling of the resultant partial differential equations were obtained using the finite difference technique of the fourth-order Runge-Kutta method. The influences of the inlet saline water temperature and volumetric flow rate on the pure water productivity as well as the hydraulic dissipated energy are also delineated.