Steady and transient mixed convection near a vertical uniformly heated surface exposed to horizontal fluid flow

Journal Article · Wed Jan 01 00:00:00 EST 1986 · Numer. Heat Transfer; (United States)

DOI:https://doi.org/10.1080/10407798608552512· OSTI ID:7030710

Rahman, M M; Carey, V P

The numerical solution of flow and heat transfer for steady and transient laminar mixed convection near a vertical uniformly heated surface exposed to a horizontal cross-flow is presented. The transients considered include the simultaneous initiation of flow and heating and the time-varying flow generated by starting or stopping forced convection with the surface heating condition unchanged. The partial differential equations describing the conservation of mass, momentum, and energy were solved in their time-dependent forms by an explicit finite-difference technique. Calculations were performed for fluids with Prandtl numbers of 0.733 and 6.7, nominally air and water. During both steady and transient circumstances, the effects of the horizontal forced flow were dominant near the vertical leading edge, whereas natural convection dictated the flow at large values of the horizontal coordinate. The heat transfer coefficient during mixed convection was significantly higher than that with either forced or free convection alone. During simultaneous starting of flow and heating, the time to reach steady state decreased with increase in cross-flow velocity. For the transients initiated by suddenly imposing a horizontal forced flow on an existing natural convection flow, the local temperature and vertical velocity were found to undershoot before reaching their respective steady-state values. The overshoot in heat transfer coefficient in such situations was significant for fluids with smaller Prandtl number. The transient initiated by stopping the horizontal flow during mixed convection was associated with overshoot in both vertical component of velocity and local fluid temperature.

• Research Organization: Dept. of Mechanical Engineering, Univ. of California, Berkeley, CA
• OSTI ID: 7030710
• Journal Information: Numer. Heat Transfer; (United States), Vol. 10:4
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
AIR
TWO-PHASE FLOW
HEAT TRANSFER
FLOW MODELS
LAMINAR FLOW
STEADY FLOW
WATER
FORCED CONVECTION
HEATING
NATURAL CONVECTION
NUMERICAL SOLUTION
PARTIAL DIFFERENTIAL EQUATIONS
PRANDTL NUMBER
SURFACES
TEMPERATURE EFFECTS
TIME DEPENDENCE
UNSTEADY FLOW
CONVECTION
DIFFERENTIAL EQUATIONS
ENERGY TRANSFER
EQUATIONS
FLUID FLOW
FLUIDS
GASES
HYDROGEN COMPOUNDS
MASS TRANSFER
MATHEMATICAL MODELS
OXYGEN COMPOUNDS
420400* - Engineering- Heat Transfer & Fluid Flow