Oil-water stratified flow, a fundamental pattern in multiphase pipe flow, is commonly encountered in offshore petroleum production and transportation. Although hydraulic characteristics of this flow regime have been extensively studied, accurate prediction of its heat transfer behavior under non-isothermal conditions remains a challenge. In this study, we develop a three-dimensional heat transfer model for oil-water stratified flow by integrating the energy conservation equation with established flow models and coupling it with momentum conservation. Turbulence is resolved using a low-Reynolds-number k-ε model. The phase interface is captured via a minimum energy model, and the irregular physical domain is transformed into a regular rectangular region using bipolar coordinates to simplify grid generation and numerical solution. The model was validated against experimental measurements of average outlet temperatures for both phases, showing relative errors within 5%. Results further reveal how water cut influences the axial temperature distribution and highlight three-dimensional temperature profiles during non-isothermal flow. This model provides theoretical insights and practical tools for optimizing thermal management and ensuring safety in offshore petroleum pipeline operations.