On the application of hot wires and pitot tubes in pipe and channel flows

Abstract

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.

This paper looks mainly at two measuring techniques, namely, the hot-wire anemometer and the pitot tube when utilized in wall-bounded shear flows. Additional heat losses occur from the hot wires in presence of walls that are not accounted for in the calibration process of the wires. Because of this, corrections for erroneous in fluid velocity measured by the hot wire in the wall proximity are to be carried out. Similarly, when the pitot tube is applied to flow measurements, the mean shear gradient and the wall proximity come to play major roles of incorrect readings. Its size is therefore to be chosen such that corrections for the shear gradient and the wall proximity are minimal. The paper outlines, therefore, corrections applied to the pitot tube measured data in both pipe and channel flows. Available corrections are adopted in this paper to both the pipe and the channel flow measured data, yielding pitot tube results that are comparable to those of the hot wire and this was demonstrated by comparing the results corrected to the socalled the logarithmic velocity profile.