Numerical predictions of llaminar fully developed forced convection in a semi-cricular duct with temperature-dependent viscosity variations

摘要

Fully developed laminar flows in a semi-circular duct with temperature-dependent viscosity variations in the flow cross-section are analyzed, where the viscosity-temperature behavior is desicribed by the Arrhenius model. Both the T and H1 boundary conditions are considered, as they represent the most fundamental heating/cooling conditions encountered in practical compact heat exchanger applications. Numerical solutions for the flow velocity and the temperature fields have been obtained by finite-difference technique. The friction factor and Nusselt number results display a strong dependence on the viscosity ratio (mu _w/ mu _b), and this is correlated using the classical power-law relationship. Howevr, results indicate that the power-law exponents are significantly different from traditional values for circular tube. They are found to functions of the flow geomtry, boundary condition, and direction of heat transfer (heating or cooling).