Experimental studies of turbulent pulsating flow and heat transfer in a serpentine channel with winglike turbulators

Particle Image Velocimetry and Infrared Thermography measurements are applied to explore the effect of quasi-triangular pulsatile flow inlet on active thermal-fluidic performance in a serpentine channel with innovative winglike turbulators. The novel turbulators are mounted in-line on two sidewalls of the channel with the attack angle (alpha), thickness to chord line ratio (t/C), and pitch to the channel hydraulic diameter ratio (Pi/DH) respectively fixed at 20 degrees, 0.2, and 0.7. The Strouhal number (St) varies from 0 to 0.67 at a fixed Reynolds number (Re) of 10,000. Relative to the steady-state case (St = 0), the flow pulsation not only strengthens the Fujiwhara co-rotating vortices but also eliminates the corner vortex streams, leading to the overall Nusselt number ((Nu) over bar /Nu(o)) enhancement by 13%. Moreover, both the (Nu) over bar /Nu(o) and friction factor (f/f(o)) reveal the tilde-like trends with St, resulting in the highest (Nu) over bar /Nu(o) of 5.2 and thermal performance factor of 1.39 at St = 0.67, which are higher than the previous best results for 10 <= (f) over bar /f(o) <= 100 in the (Nu) over bar /Nu(o)-(f) over bar /f(o) diagram. Finally, by combing the present data with our previous steady state results, composite correlations of (Nu) over bar /Nuo and (f) over bar /f(o) versus Re, alpha, t/C, Pi/D-H, and St are proposed.