An instrument for determining the velocity of a fluid is known as a pitot tube. This instrument is used in many applications, including measuring the air speed velocity of planes and determining the fluid velocity in process pipe lines.
A schematic of a pitot tube used to measure the flow rate in process pipelines is shown in Figure.
As the fluid impacts the pitot tube the pressure at point Pt increases relative to point Ps (please note that this is static pressure as there is no flow in the pitot tube).
The larger the pressure differential between Pt and Ps the faster the fluid flow. After calibrating the pitot tube the pressure differential can be used to estimate the fluid velocity.
A pitot tube, with carbon tetrachloride as the operate used to measure the flow rate of n-heptane through a 6.0 inch diameter pipeline.
At the desired flow rate h1 = 9.8 inches while h2 = 3.1 inches.
a) Determine the pressure differential (in kPa) for this flow rate.
b) If the volumetric flow rate of n-heptane is determined to be 12 gal/sec determine:
i. The mass flow rate (in lbm/sec).
ii. The molar flow rate (in lb-mol/sec).
iii. The average velocity (in ft/sec).