ISSN Online: 2377-424X
International Heat Transfer Conference 12
Turbulent, buoyancy-influenced flow and heat transfer in a vertical annulus
摘要
Measurements are reported of local heat transfer coefficients and profiles of velocity and turbulence
quantities in the case of water flowing upwards and downwards through a vertical passage of annular cross-section having a uniformly heated inner surface and an adiabatic outer surface. By operating at suitably reduced flow rates, influences of buoyancy could be produced which modified the effectiveness of heat transfer. Systematic
enhancement occurred with increase of buoyancy influence in the case of downward flow, where buoyancy opposed
the motion. Impairment of heat transfer followed by recovery and enhancement occurred in the case of upward
flow, where buoyancy aided the motion. These trends are consistent with those found in earlier studies using
uniformly heated circular tubes and can be explained in terms of the influence of buoyancy on turbulence. The
measurements of velocity and turbulence made in the course of the present study provide direct confirmation of this
explanation of the observed heat transfer behaviour. The work reported here formed part of a programme of generic
studies of thermal convection initiated by the UK nuclear industry with a view to providing data for validating CFD
codes which are used for simulating buoyancy-influenced flows.