Análise numérica da transferência de calor em escoamentos de fluidos viscoplásticos através de tubos sob a condição de gradiente de temperatura na parede

Abstract

Heat transfer in the entrance region of a tube in laminar axial flow of viscoplastic materials is analyzed. The material is assumed to behave as a Generalized Newtonian liquid, with a Herschel-Bulkley viscosity function. The governing equations are solved numerically via a finite element method. This problem was investigated previously by Soares et al. [1]. The authors considered the classical thermal boundary conditions, namely, uniform wall heat flux and uniform wall temperature. The goal of the present work is to impose a gradient of temperature along the wall as the thermal boundary condition. The effect of Reynolds, Peclet and rheological parameters (yield-stress and power-law exponent) on the Nusselt number is investigated. As expected, the values of Nusselt number tend to the classical one obtained for the case of uniform wall temperature when the gradient of temperature on the wall approaches to zero. When the gradient is increased, the Nusselt number tends to the values obtained for the case of uniform wall heat flux.