Experimental Study on Effect of Vibration on Natural Convective Heat Transfer from a Horizontal Fine Wire

An experimental study has been made to determine the effect of vibration on the rate of heat transfer in natural convection from a horizontal fine wire to various fluids (air, water and ethylene glycol). Frequencies from 0 to 20 c/sec amplitudes from 0.5 to 35 mm and diameters of wire from 0.031 to 0.203 mm were employed. The effect of vibrating motion may be considered in terms of a vibrating Reynolds number Re, based on the mean velocity of a wire. Nusselt number may be predicted by the general experimental formula Nu=0.57Re1/2 where, Re is an equivalent vibrating Reynolds number defined by Re=3.20 (GrPr)1/3+RePr2/3 and Pr is Prandtl number and Gr is Grashof number. Also, three modes in heat transfer were decided by the criterion that the coefficient of heat transfer deviates 5% from the one in pure natural and forced convection. The boundaries of three modes may be controlled on the relative magnitudes of vibrating Reynolds and Grashof number and expressed by a dimensionless parameter X.