Effect of uncertainties in fluid properties on mixed convection laminar flow and heat transfer in a uniformly heated smooth tube

Numerical analysis was carried out on the effect of uncertainties in fluid properties on developing mired convection flow and heat transfer with variable viscosity in a uniformly heated smooth horizontal tube. The results indicate that the effect of fluid property uncertainties is greater on the apparent friction factors than it is on the Nusselt numbers, and the uncertainties in the friction factors and Nusselt numbers increase with increasing entrance effects, variable viscosity, and free convection effects. Overall, the maximum uncertainties in the predicted friction factors and Nusselt numbers were around 8% and 5%, respectively, for a 10% uncertainty in the fluid properties. Furthermore, these uncertainties in the friction factors and Nusselt numbers were found to increase approximately linearly with increasing fluid property uncertainties.