Longitudinal Finned Tube Study Of The Natural Convective Heat Transfer

The finned pipe has been used widely in the heat transfer equipment, such as heating radiator. The research on the heat transfer characteristics of finned tube has not only highly theoretic value, but also very important usage value.Some numerical simulation on the heat transfer characteristics of finned tube has been done. According to the numerical simulation, the velocity contours and temperature fields around finned tubes in a variety of geometries are presented respectively. The results show that the closed finned tube is much more excellent than the opening finned tube on gross heat, heat of unit volume and metal thermal intensity with the same geometric parameters. Then the closed finned tube with both uniform wall temperature and uniform heat flux boundary conditions are emphasized in this study. The changing rules of natural convection coefficient, metal thermal intensity, gross heat, heat of unit volume and heat of unit area as the change of height and angle of fin are presented. The criterion equation of closed finned tube is derived from the results of numerical computation. It is also found that the heat transfer performance with uniform wall temperature boundary condition is better than that with uniform heat flux boundary condition under the same terms (fin height, angle and wall mean temperature).The experiment table on heat transfer of finned tube is established to test the validity of numerical simulation. The heat and temperature distribution of tube and the air around tube are measured. The result of experiment has been compared with that of numerical simulation; and has verified the correctness of numerical simulation.At last the functions of gross heat, heat of unit volume and heat of unit area are established. The relations between fin height and included angle can be obtained when the parameters have extreme point with the fixed height and angle. At the same time, the relation functions are fitted.The above research will be helpful to the design of the heat exchanger of finned tube, and will surely be significant for the manufacture and usage of them.