Numerical investigation of conjugate heat transfer in suddenly expanding channels with high expansion ratios

This study conducts a numerical investigation of steady-state conjugate heat transfer (CHT) in a suddenly expanding channel with high expansion ratios. Utilizing a compact finite difference scheme on non-uniform Cartesian grids for the ψ-v form of the Navier–Stokes (N–S) equations, coupled with a higher-order compact (HOC) scheme for the energy equations in both fluid and solid regions, the research examines two expansion ratios. Heat transfer characteristics are evaluated across a range of parameters, including Reynolds number (35≤Re≤90), conductivity ratio (1≤k≤1000), Prandtl number (0.1≤Pr≤20), and slab thickness (a≤b≤6a). The paper first provides a concise overview of the flow characteristics, followed by a detailed analysis of heat transfer behavior. Results reveal that isotherms remain concentrated near recirculation zones, with a vertical decline in temperature within the solid region. The heat transfer rate increases with higher values of Re, k and Pr, while it decreases with increasing b. Furthermore, higher expansion ratios negatively impact the heat transfer rate, as the flow fully develops at an earlier location. The flow characteristics obtained are in excellent agreement with previously reported data, offering a comprehensive and novel insight into heat transfer dynamics, potentially transforming the understanding in this domain.