The nature of vertical natural convection flows resulting from the combined buoyancy effects of thermal and mass diffusion

Natural convection flows in a vertical, open tube resulting from combined buoyancy effects of thermal and mass diffusion

Unsteady free convection flow past an infinite vertical plate with constant suction and mass transfer

Cocurrent turbulent mixed convection heat and mass transfer in falling film of water inside a vertical heated tube

Publisher Summary This chapter discusses laminar and transition flows, external and free boundary flows, and boundary layer regimes. It presents general equations of the natural convection flow and introduces approximations in terms of their physical significance to yield the conventional equations of analysis. The boundary layer simplifications for two-dimensional vertical flows are also discussed followed by the equations for vertical axisymmetric flows. For steady laminar boundary layers arising from the temperature induced buoyancy, known solutions for the vertical and axisymmetric flows are reviewed, including plumes. The combined mass transport and thermally induced buoyancy is treated, consideration is given to laminar transients. The chapter also reviews how laminar flows become unstable and how disturbances amplify to lead the flow toward transition. Vertical flows adjacent to surfaces and in plumes are considered. The nature of transition and turbulent flow are treated. The general question of instability in buoyancy induced flows is also treated. The question of separation in natural convection flow is reviewed and distinctions are drawn relative to the forced flow separation.

Natural Convection Flows and Stability

The laminar boundary-layer equations are solved asymptotically for simultaneous mass and energy transfer in a variable property binary gas mixture when one component is rapidly transferred toward the surface. Flow is past a surface of arbitrary geometry, and both forced and free convection are studied. Advantage is taken of a mole fraction formulation of the boundary-layer equations, which considerably simplifies the final results. General results are obtained for energy and mass transfer rates when physical properties are arbitrary functions of both temperature and composition. By considering two sets of property variations, representing extremes between which many actual variations lie, it is shown that in many forced convection problems the rates of energy and mass transfer can be expressed in a particularly simple form. The results also show that property variations are generally more important for free convection than for forced convection.

O. T. Hanna

Papers

Simultaneous energy and mass transfer in the laminar boundary layer with large mass transfer rates toward the surface

Modification of the high Schmidt number solution for laminar boundary layer mass transfer