Increased Measurement Accuracy of Average Velocity for Turbulent Flows in Channels of Ventilation Systems

Abstract

The turbulent gas-air flow in cylindrical channels of industrial ventilation systems is considered. The incompressible viscous fluid model has been adopted to describe the flow. It is shown that the measurement accuracy of the average velocity is determined by the sensor location in the flow section of the channel. The velocity distribution in the channels is represented by power dependence. The experimental data of the exponent in the velocity distribution along the radius of the circular cylindrical pipe are used. The approximation of the experimental exponent by analytical dependence was performed, which allows determining the radius of the average velocity depending on the Reynolds number. The recommendations for increasing the accuracy of measuring the average speed in the circular cylindrical channel are formulated. The empirical dependence was used to determine the radius of maximum velocity in the ring-shaped cylindrical channel. This dependence allowed us to establish algorithmic expressions for the two radii of the average velocity in the ring-shaped channel. It is shown that the radii of the average velocity practically do not depend on the Reynolds number and essentially depend on the dimensionless form parameter determined by the ratio of the radii for the inner and outer surfaces of the channel. It is recommended that of the two radii of the average velocity in the ring-shaped cylindrical channel, the greater one will be used, where, due to the smaller radial velocity gradient, the sensor installation error for the measurement accuracy is less pronounced.