Natural Convection in the Annulus Between Horizontal Circular Cylinders With Three Axial Spacers

Abstract

Conjugate natural convection heat transfer in an annuius between horizontal isothermal circular cylinders with three equally spaced axial spacers has been studied theoretically and experimentally. A thin-fin approximation was used to model the thermal boundary condition of the spacers in the two-dimensional finite difference numerical computations. Rayleigh number, Prandtl number, diameter ratio, and location and thermal conductivity of the spacers were varied parametrically to determine the variation in flow patterns, temperature distribution and heat transfer. Spacers of low conductivity can decrease the natural convection heat transfer by as much as 20 percent below that for a simple unobstructed annuius. However, radial conduction through spacers of high conductivity overwhelms the natural convection heat transfer between the cylinders. Two diameter ratios were tested experimentally in a Mach-Zehnder interferometer using air at atmospheric pressure with stainless steel spacers between copper cylinders. The numerical and experimental temperature distributions and local convective heattransfer coefficients show good agreement.

Systems study of the feasibility of high-level nuclear waste fractionation for thermal stress control in a geologic repository: appendices

“…The significant length in the Rayleigh number is the gap width. Other references included Eckert and Drake (1972), Goldstein (1973 and1976b), and Kwon, Kuehn and Lee (1982). These references include thorough bibliographies.…”