In this paper, the coupling effect of dimple depth and fluid properties on convective heat transfer of kerosene flowing in a small-scale rectangular duct with circular dimples is studied numerically. The numerical simulation is based on Reynolds average method with a shear stress transport (SST) k - ω turbulence model and a 10-components surrogate model of kerosene. Turbulent flow and heat transfer properties in different depths of circular dimples are obtained. The results show that the three-dimensional vortices are generated by dimples and the vortices alter local turbulent flowing significantly, leading to both enhanced and reduced convective heat transfer to the wall at different locations. It is also found that the averaged Nusselt number on different dimpled walls first increases in the raising of dimple depths and then decreases after dimple depths reach a certain value. The obtained flow field shows that the heat transfer enhancement on the dimpled wall is caused by vortices with horse-shoe and tornado structures. When dimple depth further increases, the vortical structure changes to asymmetric horn spiral form, which causes heat transfer reduction. Similar to the variation of Nusselt number, the friction factor through dimpled duct also increases firstly with the dimple depth and then decreases.