Abstract: Dual fluid molten salt reactor (DFR) using molten fuel salts and liquid metal coolants provides a promising approach for high-power-density nuclear energy systems. This study aims to investigate the coupled heat transfer characteristics between molten fuel salt with volumetric fission heat generation and lead coolant in a DFR core, focusing on the effects of thermal-hydraulic and heat generation parameters on heat removal performance. A conjugate heat transfer model, including the solid separator wall between fuel salt and lead coolant channels, was established and solved using the finite volume method with appropriate turbulence modeling. Grid independence verification and parametric simulations were performed to evaluate the effects of fuel salt inlet temperature and velocity, lead coolant inlet temperature and velocity, volumetric heat generation rate, and radial power distribution. The parameter ranges considered in the simulations include fuel salt inlet temperatures of 903.15-933.15 K, lead coolant inlet temperatures of 783.15-813.15 K, and inlet velocities of 1-4 m/s for both the fuel salt and lead coolant. The effective heat transfer efficiency (η), defined as the ratio of heat removed by the lead coolant to total heat generated in the fuel salt, was adopted as the performance indicator. The radial core region was divided into outer, middle, and inner zones based on a Bessel-function-derived power distribution to analyze zone dependent heat transfer behavior. The results show that NaCl-UCl₃ molten salt exhibits a higher axial temperature rise and greater η than fluoride salts due to its lower specific heat capacity, indicating its suitability for DFR applications. The η increases with increasing fuel salt inlet temperature and lead coolant velocity but decreases with increasing volumetric heat generation rate and lead coolant inlet temperature. Compared with uniform power distribution, the Bessel type non-uniform power distribution improves η by approximately 2%. The influence of fuel salt velocity on η is strongly dependent on radial power zoning. In the outer zone, enhanced convective heat transfer dominates, resulting in a continuous increase in η with increasing velocity. In the middle zone, the competition between enhanced convection and increased thermal losses caused by reduced residence time leads to a non-monotonic variation of η. Under the full-core averaged power condition, thermal losses dominate over convective enhancement, causing η to decrease continuously with increasing fuel salt velocity. These results demonstrate that thermal-hydraulic optimization of DFR cores requires consideration of radial power distribution, residence time effects, and the balance between heat extraction enhancement and thermal losses. The findings provide a reference for the thermal-hydraulic design and optimization of DFR.