NUMERICAL STUDY OF MIXED CONVECTION OF AIR IN THE ENTRANCE REGION OF VERTICAL CONCENTRIC ANNULUS

Abstract

Numerical results of a finite difference scheme are presented for the developing mixed forced – free laminar boundary layer flow in a vertical concentric annulus with a uniformly heated inner cylinder. The effect of a superimposed aiding or opposing free convection on the developing velocity profiles is investigated for a fluid with Pr=0.7 over the ranges of heat flux 50 ≤q≤250 (W/m2), Reynolds number 200≤Re≤1200 , and radius ratio 0.2≤N≤0.9. The effects of heat flux , Reynolds number , and radius ratio on the developing of the axial velocity profiles , temperature profiles , and local Nusselt number along annulus are discussed. Results show that the growth of the thermal boundary layer along the annulus increases as heat flux increases and Reynolds number decreases. Computer program in Fortran language was developed to carry out the necessary calculation.