ISSN Online: 2377-424X
International Heat Transfer Conference 12
Influences of buoyancy and thermal boundary conditions on convective heat transfer in a tube with naturally-induced flow
摘要
A study is reported of turbulent heat transfer to air which is induced naturally through a vertical heated tube
by the action of buoyancy. Measurements of local heat transfer coefficient were made for conditions of uniform
wall temperature and also uniform heating using a specially designed, computer-controlled power supply and data
acquisition system. The effectiveness of heat transfer proved to be much lower than it would have been for
conditions of forced convection at the flow rates achieved. This was because the flow was buoyancy-influenced as
well as buoyancy-driven and, as a result, turbulence production was impaired. The results correlated satisfactorily when presented in terms of dimensionless parameters of the kind used for free convection heat transfer from vertical surfaces, (that is Nusselt number and Grashof number based on distance from the start of heating), provided that the fluid temperature used in the heat transfer coefficient was the local bulk temperature.