Experimental Investigation of the Effect of Forced Vibration on Natural Convection Heat Transfer in a Concentric Vertical Cylinder

Natural convection heat transfer under forced vibration has been the subject of a large number of studies due to the lower thermal conductivity of conventional fluids for instance ethylene glycol, water, engine oil, etc. The observations were implemented to obtain an improvement in the coefficient of heat transfer resulting from mechanical vibrations induced to a vertical cylinder. This work includes a practical investigation of natural convection heat transfer in a concentric vertical cylinder and the effect of forced vibration on heat transfer augmentation. The brass body of cylindrical shape was located inside the center line to heat vertical cylinders of internal and external diameter 16 cm and 30 cm, respectively. Constant heat flux is supplied to the test model, ranging from 35 to 75 W/m2. The vibration frequency was varied for the values of 90, 110, 140, and 180 Hz and the vibration amplitude length was kept constant at 0.6 amps. The findings reveal that the local heat transfer coefficient is clearly affected by the amount of heat input and axial distance of the cylinder, indicating a positive relationship with the first and an inverse relation with the latter, while an obvious increase is observed in the local Nusselt number along the cylinder axis from bottom to top.