ANALYSIS OF HEAT AND FLUID FLOW IN CONCENTRIC ANNULAR SQUARE DUCTS

Abstract: A numerical study is conducted on the heat and fluid flow characteristics in an annulus between two concentric square ducts. Inner and outer walls are assumed to be isothermal, but at different temperatures. The flow through the annular duct is assumed to be laminar, steady, and both hydrodynamically and thermally fully developed with constant physical properties. For the Cartesian coordinate system, the governing equations are discretized by using the control volume method and are solved by the ADI method. The upwind scheme and the central difference scheme were employed to represent the convection and diffusion terms, respectively. The Stone’s method was employed to solve the pressure-correction equation based on the SIMPLE Algorithm. Solutions were obtained for air (Pr=0.7). The velocity and temperature fields, the friction coefficients and Nusselt numbers are presented depending on the dimension ratio, a/b. With the increasing dimension ratio, it has been shown that the convective heat transfer is remarkably enhanced at the inner wall, while it becoming worse at the outer wall. The present results are compared with those for an annulus between two concentric cylinders and, finally, it is disclosed that the present or forme