STUDY OF HEAT TRANSFER CHARACTERISTICS OF A DOUBLY CONNECTED NON-CIRCULAR DUCT

Abstract

Non circular ducts make the heat exchanger compact and improve its performance and efficiency. It is therefore necessary to have the knowledge of their flow and heat transfer characteristics for an efficient design of a heat exchanger. The cross-section of the non-circular annular passage, which is investigated analytically, is bounded both externally and internally by rectangular tube. Analytical investigation is confined to thermally and hydrodynamically fully developed laminar, steady flow of an incompressible viscous fluid. The thermal boundary condition of second kind i.e. insulated outer tube and constant heat flux at the inner . wall have been considered. A finite element solution algorithm has been developed for obtaining numerical solutions to the governing equations for momentum and energy transfer. Results are obtained for aspect ratios 0.2 to 0.8. Velocity and temperature profiles have been presented and discussed. Isovels and isotherms are also plotted. The frictional factors are determined in the form of product of frictional factor and Reynolds number for aspect ratios 0.2 to 0.8. Variation of Nusselt number with aspect ratios have been presented and discussed. The values of the product of friction factor and Reynolds number (f. Re) for above configuration is found considerably less than those of circular annulus having same 'aspect