A computational study of heat transfer in a laminar oscillating confined slot jet impinging on an isothermal surface at low Reynolds numbers

Abstract

Heat transfer in a laminar confined oscillating slot jet is numerically investigated. A uniform inlet velocity profile oscillating with an angle φ, having the following sinusoidal shape: φ= φmax*sin(2πft). φ is in radians, φmax is the maximum jet angle, and f is the oscillation frequency. The height-to-jet-width ratio (H/w) was fixed to 5 and the fluids Prandtl number which is one of the dimensionless governing groups is 0.74. The other dimensionless groups characterizing this problem, which are, Strouhals number, St, and Reynolds number, Re, where varied. Re was in the range 100<Re<400, and St was in the range 0.05<St<0.75. Both St and Re numbers are based on the jet hydraulic diameter (2w). Defining φmax is explained later in this paper. For Re=250 and St=0.5, a dim heat transfer enhancement was noticed in the stagnation region, when compared to the steady case. A similar enhancement was observed for Re=400 at St=0.75. At Re=100 no improvements were observed, where the flow showed a high vulnerability to severe oscillations, that drastically reduced heat removal ability. Jet flapping could be triggered at Re=400. But the flapping mode was most stable for St=0.75, in which case, heat transfer enhancement was detected.