Natural convection heat transfer along vertical wavy surfaces with different amplitude-to-wavelength ratios

This study investigates steady, laminar natural convection heat transfer along a vertical isothermal plate incorporating wavy surfaces, employing both experimental and numerical approaches. The wavy surface geometry is modeled using cosine profiles with varying amplitude-to-wavelength ratios of 0.061, 0.083, and 0.167. Computational fluid dynamics (CFD) simulations based on the finite-volume method were conducted, and particle image velocimetry (PIV) technique was utilized to measure the velocity field. The results from the CFD simulations were validated through comparison with experimental measurements, exhibiting qualitative agreement. The findings indicate that the amplitude-to-wavelength ratio critically influences the air velocity distribution and convective heat transfer. Enhance velocity gradients at convex regions modestly improve heat transfer, whereas stagnation at the concave regions significantly impairs natural convection. Increasing the amplitude-to-wavelength ratios further expands stagnant regions, reducing velocity gradients adjacent the wall and weakening convection. Heat flow based on the mean heat transfer coefficient for wavy surface profiles decreases by 6.08 %, 9.56 %, and 25.95 %, compared to a flat plate. However, when the mean heat transfer coefficient was determined based on the projected length of surface profiles, heat flow improves by 0.60 %, 2.42 %, and 13.06 %, respectively.