Preston Tube Measurements in Low Reynolds Number Turbulent Pipe Flow

Preston tube measurements were carried out in low Reynolds number, fully developed, turbulent pipe flows to examine the applicability of Patelʹs calibration equations derived at higher Reynolds numbers and to account for other variables that might be relevant at lower Reynolds numbers. There was a large degree of scatter when the data were plotted in terms of the variables adopted by Preston and Patel in their calibration equations. An investigation was carried out into the influence of other variables of likely relevance, but no systematic dependence could be identified. The scatter was therefore treated as a random error, and a third-order polynomial was fitted for the range of the experimental parameters. It deviates somewhat from Patelʹs calibration.