HEAT-TRANSFER AND FLOW CHARACTERISTICS IN A ROTATING-DISC SYSTEM

An experimental investigation of heat transfer and fluid flow on a hea ted rotating disc in a stagnation flow has been carried out. From the measured results of heat transfer coefficients, the conditions of tran sition from the region in which the stagnation flow is dominant to the region in which the forced convection by the disc rotation is dominan t, and the transition from the forced convection dominant to the natur al convection dominant region are determined. Empirical equations of N usselt numbers for the three regions are also given. Flow visualizatio ns by shadowgraphy and laser induced fluorescence techniques show that circumferential vortices due to buoyancy force appear on a rotating d isc in the natural convection dominant region. The circumferential vor tices are generated in the central region of the disc and move outward s in a radial direction. The radial velocity of the circumferential vo rtices is calculated from the time correlation of the temperature fluc tuation. The calculated results indicate that the circumferential vort ices have constant velocity at the outer region of the disc.