Natural convection heat transfer from axially finned cylinders

Convection heat transfer occurs between a surface and a fluid. There are three ways to enhance the heat transfer. These are; to increase the heat transfer coefficient, to enlarge the heat transfer area and to increase the temperature difference between the mediums. It may be impossible to increase the heat transfer coefficient and the temperature difference of the mediums in occasional conditions. The most preferred way to improve the heat transfer is the enlargement of the heat transfer surface area. This method is especially preferred in electrical and heating systems. Those interprets can be made according to the values of Nusselt and Rayleigh numbers in natural convection heat transfer. It is usually accepted as the heat transfer is in laminar boundary layer if Ra108 and is in turbulent boundary layer if Ra109. It is assumed as transition region for natural convection 108 Ra109. The experiments were handled in natural convection region. Natural convection heat transfer are investigated by considering the effects of thermal radiation heat transfer from axially finned cylinders. The experiments were repeated for different angular positions and for various thermal power inputs. Not only the angular position, but also the thermal power input; fin dimensions and the spaces among the fins were taken as variables as well. The measurement were made for the unfinned cylinder for the same angular position and thermal power inputs and comparisons are made. It is observerd from the result of the experiments that the fin increase the heat transfer considerably when compared with the unfinned surface. For example, by flat cylinder with 6 axial fin height of 30 mm it increased approximately 3-fold heat transfer cylinder. Furthermore it appears that the radiation heat transfer is next to be underestimated the importance of heat transfer by convection. Total power ratio of actual radiation heat transfer has a flat cylinder at low power value of 49% was realized that the increased power value is determined to fall to 43,4%.