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This research aimed to examine the effect of the thermal conductivity model of hydrophobic membranes on performance modelling of direct contact membrane distillation systems. The parallel, series, and two types of Maxwell models were studied. Simultaneously, an iterative numerical model was developed to choose the most appropriate model by analysing the mass flux (Jw) and the heat transfer rate (Q-P). Comparison with the experimental results, showing that Maxwell Type II was the most appropriate for modelling the thermal conductivity of the membrane. Also, based on the chosen model of membrane thermal conductivity, the direct contact membrane distillation performance (the global heat transfer coefficient, temperature polarization coefficient, energy efficiency, and gain output ratio) was studied. It was found that the membrane thermal conductivity model with a higher value of membrane thermal conductivity (km) resulted in an underestimation of the predicted mass flux, temperature polarization coefficient, and energy efficiency. In contrast, the total heat transfer coefficient and predicted heat rate were overestimated. The gain output ratio values seemed not to be affected by this choice with only 8% deviation among the four models. [ABSTRACT FROM AUTHOR]