Effect of fin waviness and spacing on the lateral vortex structure and laminar heat transfer in wavy-plate-fin cores

Laminar forced convection in air (Pr=0.7) in two-dimensional wavy-plate-fin channels with sinusoidal wall corrugations is numerically simulated. Constant property, periodically developed flow in uniform wall temperature plate channels is considered. Velocity and temperature fields, isothermal Fanning friction factor, and Colburn factor are presented for different flow rates (10⩽Re⩽1000), wall-corrugation severity (0.125⩽γ⩽0.5), and fin spacing (0.1⩽ε⩽3.0). Lateral vortices or re-circulation cells develop in the wavy-wall troughs as the axial flow gets separated downstream of the wall-corrugation peaks and re-attaches upstream of the subsequent wall peak, and their strength and coverage is a function of Re, γ, and ε. As the plate separation ε decreases, however, viscous forces dominate and dampen the swirl; with very large ε, the impact of wall waviness diminishes and the core fluid flows largely undisturbed. The surface waviness-induced periodic disruption and thinning of boundary layers along with lateral swirl mixing produce high local heat fluxes near the wall peak regions. The overall heat transfer coefficient increases many fold compared to that in flat-plate channels with relatively small increases in the concomitant pressure drop penalty. The optimum (j/f) enhancement is obtained in the swirl flow regime (Re>100) with γ>0 and 1.0⩽ε⩽1.2.