Membrane distillation is a thermally driven mass transfer in which a porous hydrophobic membrane separates two liquid phases and a temperature difference is maintained as the driving force. In this study, the technique of direct contact membrane distillation (DCMD) process, where the liquid phases are in direct contact with both sides of the membrane, has been investigated for the case of pure water production. Parametric sensitivity analysis and temperature polarization factor are used to study the sensitivity of the mass flux to the different parameters associated with DCMD for water production, and the effect of these parameters on the thermal efficiency of the DCMD process has been investigated. The results obtained show that the mass flux of pure water production is highly sensitive to the feed bulk temperature, and at low flow rates of hot and cold fluids, to the heat transfer coefficients. Results also show that increasing membrane thickness decreases the mass flux of pure water and decreases temperature polarization effect. In addition, results show that temperature polarization effect becomes significant as feed bulk temperature increases.