Experimental and numerical study of the thermal-frictional behavior of a horizontal heated tube equipped with a vibrating oscillator turbulator

Abstract

This study investigates a novel heat transfer enhancement method named electromagnetic vibration (EMV) method. For the first time a stretched oscillator with geometries of string and strip was placed coaxially inside a heated copper tube and induced to vibrate at the natural frequencies. Longitudinal vibration of the stretched oscillators creates harsh turbulence, radial flow and vortexes inside the heated tube. Tests were conducted for various vibrational frequencies ranging 0 to 1 KHz in different mass flow rates. The experimental results indicated that oscillator with the geometry of strip has the better thermal performance; also the heat transfer coefficient can be increased with increasing vibration frequency from 2.18 to 2.50 folds. For comprehensive analyze at high frequency vibrations, a numerical model was conducted for the vibrating strip geometry to evaluate this new method capability in heat transfer performance enhancement. The numerical study shows that at 1 KHz frequency, heat transfer coefficient and thermal enhancement factor (TEF) can reach up to 32.2 and 14.2 fold compare to the plain tube, respectively. This magnificent increment shows the high potential of the EMV method as a new heat transfer augmentation technique.