Effects of Temperature-Dependent Viscosity Variations and Boundary Conditions on Fully Developed Laminar Forced Convection in a Semicircular Duct

Abstract

Fully developed laminar flows in a semicircular duct with temperature-dependent viscosity variations in the flow cross section are analyzed, where the viscosity-temperature behavior is described 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 (μw/μb), and this is correlated using the classical power-law relationship. However, results indicate that the power-law exponents are significantly different from traditional values for circular tube. They are found to be functions of the flow geometry, boundary condition, and direction of heat transfer (heating or cooling).

Effects of temperature-dependent viscosity variation on entropy generation, heat and fluid flow through a porous-saturated duct of rectangular cross-section

“…For example, the viscosity of glycerin has a threefold decrease in magnitude for a 10 o C rise in temperature [12]. This trend is not only observed in such viscous liquids but also in other liquids such as water; where the viscosity of the water decreases by about 240 percent when temperature increases from 10 o C to 50 o C, as reported by Ling and Dybbs [13].…”

Heatline and Energy-Flux-Vector Visualization of Natural Convection in a Porous Cavity Occupied by a Fluid with Temperature-Dependent Viscosity

“…Arrhenius model proposes an exponential form of viscosity-temperature behavior to provide a good representation for most common fluids as reported by [19,20]. It is applied here for flow of an incompressible gas or liquid.…”

Heatline Visualization of Natural Convection in a Porous Cavity Occupied by a Fluid With Temperature-Dependent Viscosity

“…1, similar to that of [10][11][12]. Following recommendations by [13], the Arrhenius model for viscosity-temperature relation is applied here for flow of an incompressible fluid. The viscosity of a gas usually increases with temperature and the viscosity of a liquid does the reverse.…”