Heat transfer characteristics of laminar and turbulent wavy channel flow in the presence of a stationary or rotating blade

Due to the widespread use of heat exchangers, it is very important to use methods to increase heat transfer in them. Corrugating channel walls and simultaneously utilizing a blade can be used as a combined passive–active technique to enhance heat transfer in heat exchangers. In this research, heat transfer from uniformly heated walls of a symmetric sinusoidal wavy channel equipped with an adiabatic blade is numerically investigated. The main objective is to study the effects of the channel wall’s geometry (straight or wavy), the blade’s shape (flat or circular), the status (stationary or rotating) of the blade and the flow regime (laminar or turbulent) on the flow characteristics and thermal–hydraulic performance of the channel. Simulations are performed in fully developed steady (or unsteady) and incompressible flow with Reynolds number in the range of 50–10,000. For the turbulent case, the SST k – ω model is exploited that can properly capture the flow behavior in the presence of the blade. For the rotating flat blade, the sliding mesh method is implemented to simulate the motion of the mesh around the blade. The results show that partial corrugation of the walls of a clean channel (without any blades) significantly reduces the total heat transfer in the laminar flow while improves it in the turbulent one. However, in the presence of the blade, the effect of corrugated channel walls on the heat transfer depends strongly on the shape and status of the blade. It is observed that unlike the stationary circular blade, the use of the stationary flat blade in the corrugated channel improves the heat transfer in both the laminar and turbulent flow regimes compared to the straight channel. As the Reynolds number increases, this positive effect increases. In the presence of a stationary flat blade, the use of corrugated walls with low-wavelength/low-amplitude waves in the turbulent flow regime and corrugated walls with high-wavelength/high-amplitude waves in the laminar flow regime is more efficient. The results show that (flat or circular) blade rotation cannot improve the heat transfer rate in the corrugated channel compared to the straight channel.