چكيده به لاتين
Abstract:
The aim of this dissertation is to analyse the effect of radiation on turbulent mixed convection in a vertical duct with variable thermophysical properties. The Reynolds number based on duct width is and the Grashof number based on duct width and hot and cold wall temprature diffrence is . The turbulent Reynolds number is . Both right and left walls have constant temprature, where back and front walls are insulated. Right wall is the hot wall and flow near that is aiding where left wall is cold and flow near that is opposing due to bouyancy effects. The open source OpenFoam CFD toolbox employed to solve the three dimensional Navier- Stocks and energy equation. RANS based model is employed to model the turbulence. All the walls are active in radiation and the fluid is considered gray, absorbing and scattering. The Radiative transfer equation is solved by disceret ordinate method. The fluid’s dynamic viscosity and thermal conductivity varies by temperaturebased on power law. The density is based on perfect gas equation of state.
The effect of four radiative parameters, namely, wall emissivity, optical thickness, scatteing albedo, conduction-to-radiation parameter, the effect of variable thermophysical properties and the effect of Boussinesq and nonBoussinesq approximation on the flow and thermal fields, Nusselt number and friction factor are studied. The results show that with rise in radiation effects by increasing and and decreaing and , due to reduction in buoyancy effects, the velocity and temperature profiles become flattened. Also, results show that when the thermophysical properties are variable with temperature, the Nusselt number and friction factor on aiding side decreased and on opposing side increased. By Non-Boussinesq approximation, the Nusselt number and friction factor, both, increased on opposing side and decreased on aiding side.
Keywords: Effect of adiation om mixed convection, Verticl duct, Discerete Ordinate Method, Variable Thermophysical properties, Boussinesq and Non-Boussinesq approximation
