MIXED CONVECTIVE AND RADIATIVE HEAT TRANSFER IN A HORIZONTAL CONCENTRIC AND ECCENTRIC CYLINDRICAL ANNULI

A numerical investigation has been performed to study the effect of eccentricity on unsteady state, laminar aiding mixed convection in a horizontal concentric and eccentric cylindrical annulus. The outer cylinder was kept at constant temperaturewhile inner heated with heat flux. involved solution transient momentum (Navier-Stokes) energy equation using finite difference method (FDM), where body fitted coordinate system (BFC) wasused generate grid mesh for computational plane. governing equations were transformed vorticity-stream function formula as temperature stream equation.A computer program (Fortran 90) built calculate bulk Nusselt number (Nub) after reaching steady state condition fluid Prandtl fixed 0.7 (air) radius ratio ( =2.6), Rayleigh (Ra=200), Reynolds (Re=50) both annulus different ratios (ε=0, 0.25, 0.50, 0.75) angular positions (φo=0o, 45o , 90o 135o 180o ).The results show reasonable representation relation between (ε, φo). Generally, Nub decreased increase (ε Also, that best thermal performance angularposition (φo=0o ) (ε=0.25), while maximum reduction rate transfer position (φo=180o) (ε=0.75).Comparison result previous work shows good agreement.