Temperature polarization analysis and interfacial heat transfer mechanism of membrane distillation based on direct micro-thermocouple measurement

Membrane distillation (MD) is a promising technology for treating hypersaline wastewater, but its performance is limited by temperature polarization (TP), particularly in direct contact membrane distillation (DCMD). In this study, the nonlinear interactions governing the temperature polarization coefficient (TPC) and interfacial heat transfer mechanisms were quantitatively elucidated using response surface methodology and thermal-electrical network model. Key variables, including inlet temperature difference ( ΔT ), feed velocity, and salinity, were experimentally optimized to maximize the TPC. Three-dimensional response analysis identified flow dynamics as the dominant factor, with significant nonlinear coupling between ΔT and salinity. The derived optimization model achieved a maximum TPC of 0.935 under the optimal conditions (ΔT = 38.95 °C, flow rate = 900 mL/min) with a 1.4% prediction error. To gain insights into heat transfer mechanisms, an equivalent thermal-electrical network model was employed to quantitatively resolve interfacial heat transfer pathways, revealing that latent energy transport constitutes 57% of transmembrane flux versus 43% conductive loss via the membrane matrix. Critically, convective heat transfer dominated thermal transport within hot/cold boundary layers (67–70%), as opposed to 30–33% contributed by mass transfer-induced heat exchange. The findings clarified the nonlinear interactions of temperature polarization and heat transfer dynamics in DCMD, offering reliable strategies for MD operation under minimized temperature polarization effects. Copyright © 2026. Published by Elsevier B.V.