Numerical Simulation of Laminar Mixed Convection of Air Flow Through Uniformly Heated Vertical Tubes

Abstract

This paper discusses laminar mixed convection of air flow through vertical tubes. Calculations were performed by solving the Navier-Stokes and energy equations for a number of heating lengths. The Reynolds number based on the fluid bulk velocity and diameter of the tube is Re = 500 and Grashof number based on wall heat flux is Gr = 106. The numerical results have been obtained using a finite-volume code which solves the governing equations in axi-symmetric coordinate system. The pressure field is obtained with the SIMPLE algorithm. The HYBRID scheme is used for the convective terms. The computer code was validated by comparing its predictions with the reported analytical, numerical and experimental results. For various heating lengths the values of Nusselt number and friction coefficient are presented and the effects of heating length on these parameters are studied. It was found that for the buoyancy-aided convection, the velocity in the vicinity of the wall increases while decreases in the core region. These result in an enhancement of wall heat transfer coefficient.

Combined Convection Heat Transfer to Thermally Developing Air Flow inside a Circular Inclined Cylinder

“…The mixed convection heat transfer correlation constants C, m, Cq and mq for the above relations, for the five inclination angles are presented in the equation form in table (1). Fig.…”

“…Instances of these processes are nuclear reactor engineering and in heating or cooling of heat exchangers for viscous liquids, heat exchangers for gas flows, electronic cooling, compact heat exchangers, and the cooling of rotating parts such as rotor blades of gas turbine also the pipe lines used for transporting oil. Raisee and Shahraeeni [1], (2007), made numerical simulation on vertical tubes that uniformly heated with laminar mixed convection air flow. For a bit of heating lengths, the Navier-Stokes and energy equations were solved using a finite-volume code which solves the governing equations in axisymmetric coordinate system, with Reynolds number Re=500 which depends on the fluid bulk velocity and diameter of the pipe, and Grashof number Gr=10 6 which depends on wall heat flux.it was resolved that the velocity near the wall increases for the buoyancy-aided convection, and decreases in the center area.…”