Numerical simulations are performed to investigate the accuracy and reliability of the shell conduction approach available in the Ansys Fluent 19.2 software for heat transfer calculation in cladded miniature heat sinks. The validation process is conducted first to verify the accuracy and reliability of the developed numerical procedure to study convective heat transfer in small-scale heat sinks. Moreover, modified solution verification is developed and performed to evaluate the performance of the shell conduction model in different cladded miniature heat sinks. Laminar water and turbulent liquid sodium (Na) flows and heat transfer within cladded miniature and minichannel heat sinks are investigated respectively. The cladding layer thickness varies between 0.5–1 mm while the cladding layer thermal conductivity covers a range of 4–17 (W/mK).