The varying effect of natural convection on shear stress rate on cylindrical surfaces

In a dynamic weighing gas mass flow measurement, the gas mass flow rate is continuously determined by weighing a gas mass loss from a gas cylinder as a function of time. In this measurement method, the temperature difference between the wall of the gas cylinder and ambient air cannot be avoided. Due to natural convection flow, a shear stress appears on the wall of the cylinder. Because of the dynamic nature of the method, the shear stress rate varies as a function of time during the measurement period. In this paper, the magnitude and effect of the variable shear stress was studied theoretically and experimentally. Obtained results showed good agreement between the theory and experiments.