Visualization of impinging jet on the heated disc and evaluation of heat transfer coefficient distribution

Abstract

In this study, the effect of the vertical direction and nozzle diameter d_N on heat transfer on the heated disc in cylindrical flow channel was investigated. When the heated disc was installed vertically downward (+g), for d_N = 10mm the Nusselt number Nu had a maximum value at the center of the disc due to impinging jet flow while for d_N = 180 mm the Nu had a maximum value at the edge of the disc due to natural convection. The average Nusselt number Nu_av along the radial direction on the disc decreased drastically with Richardson number Ri. The validation of the Nusselt number ζ had a minimum value of about 0.5 at 100 < Ri < 10000. On the other hand, when the heated disc was installed vertically upward (-g), the Nu became almost uniform along the radial direction on the heated disc for d_N > 50 mm. The Nu_av was two times higher than that for +g condition while the ζ had about 0.2 at (-Ri) > 100000.