CFD simulations were performed to evaluate the performance of a hollow fiber membrane distillation module under laminar, counter-current flow conditions. A conjugate heat transfer model was used to predict thermal boundary layer development, temperature polarization coefficient (TPC), local heat transfer coefficients, and mass fluxes, including the effect of spacers. Results showed that the feed-side heat transfer coefficient (hf) is generally lower than that of the permeate side (hp), influencing overall heat transfer performance. The deviation between membrane surface and bulk fluid temperatures characterized the temperature polarization effect, which initially decreases and then increases along the membrane length. The model also demonstrated the dependence of mass transfer rates on operating conditions. Overall, CFD proved to be an effective tool for predicting key transport phenomena and performance in membrane distillation systems.