High energy costs for your air supply? Save money with a precise air flow regulation for your aeration tanks? With deltafit you’ll get ready-for-use unit for your supply pipes.

principle

Principle of the integrating pitot tube

Integrating pitot tubes are used for the flow measurement of gaseous or liquid fluids such as combustion air, compressed air, natural gas, steam, water etc. in pipes and channels. Pitot tubes have several tappings with and against the direction of flow. At the tapings against the direction of flow a dynamic positive pressure pdyn1 stagnation pressure develops, at the openings in direction of flow a dynamic negative pressure pdyn2 is developing. Within the pitot tube the pressures of the tappings are averaged and measured outside of the pitot tube.

From the measure dp one can calculate the flowrate in the pipe.

dp = p1 − p2
p1 = pstat + pdyn1
P2 = pstat + pdyn2
dp = pdyn1 − pdyn2

calculation basics of dp measurement

the basic formula of dp flow measurement is deduced from the law of the conservation of energy. From the dp one can calculate the massflow in the pipe:
Berechnungsformel Massenstrom with:

– mass flow
K – calibration contstant of dp element (K-Number)
d – inside diameter of pipe
– expansion coefficient
dp – measured differential pressure
ρ – density of fluid

Die dimensionslose Kalibrierkonstante K wird von den unterschiedlichen Herstellern für ihre integrierenden Staudrucksonden ermittelt und dem Benutzer mitgeteilt. Ein typischer Wert liegt zwischen 0,62 und 0,68.

Die Expansionszahl ε korrigiert die Dichteänderung des Fluids durch den Druckverlust an der integrierenden Staudrucksonde. Für inkompressible Fluide (Flüssigkeiten) ist ε=1; bei kompressiblen Fluiden wird ε kleiner 1, bleibt aber typischerweise im Bereich [0,97< ε < 1]. Die Dichte ρ des Fluids ist die Dichte unmittelbar vor der integrierenden Staudrucksonde.