Experimental Study of the Effect Geometrical Shape and Vertical Vibrations on Forced Convection Heat Transfer Coefficient from Circumferentially Triangle-Cross Section Finned Cylinder

Abstract

The aim of this work is to perform an experimental study for the effect of forced vertical vibrations on forced convection heat transfer coefficient, by the use of a circumferential finned cylinder made of Aluminum. The cylinder was heated under the condition of a constant heat flux which is generated by applying an alternating voltage on a fixed resistor mounted inside the interior space of the cylinder which was located horizontally or inclined in multiple angles of (0°, 30°, 45°). In this experimental study, the circumferential finned cylinder prototype of inner diameter (16 mm), and outer diameter including the fin of (48 mm)was used, and the effect of the frequency at a range of (2-16 Hz) and the vibration amplitude range of (0 - 2.2mm) have been studied with heat flux rates (500,1000,1500 W/m2) on heat transfer coefficient. From the results of this study, it was found that the relation between the heat transfer coefficient and amplitude of vibration is incrementally for angles (0°, 30°, 45°). And reaches a maximum ratio of (12.85%) with respect to the frequency equals zero. The increment of inclination angle reduces the values of forced convection heat transfer coefficient, because the fins work as path lines that help to increase the movement of convection currents in the case of horizontal prototype, but in case of inclined cylinder, the fins work as obstructions for the convection currents, thus reducing the ranges of forced convection vibrational heat transfer coefficient. Generally, the heat transfer coefficient increases as Reynolds number increases. The experimental results were compared with results of reference [9] and found that the effect of Geometrical shape on heat transfer coefficient of the cylinder used in this research less than that for reference [9] because the total surface area for the sample used in reference[9] was larger than that for the sample used in the current study .