When fluid flows in pipe, there are several ways how to measure its flow. Ultrasonic is the one of technology that can measure fluid flow inside pipe. The measurement principle using ultrasonic doesn’t affects fluid flow because it is non-contact measurement. The other ways to measure fluid flow are contact measurement. This kind of measurement will affect the fluid flow.
Contact measurement of fluid flows usually use the principle that convert from flow to different pressure. Venturi tube, orifice, and pitot tube are the example of fluid flow measurement using conversion flow to different pressure.
Venturi meter is pipe narrow constriction. Fluid flows from pipe whose diameter is bigger, then enter the pipe whose diameter is smaller. Based on continuity law, flow rate will be same but the velocity will be different.
Q1=Q2
A1.v1 = A2 . v2
As we can see at the simple equation above, if area of pipe is smaller, velocity will increase. How to measure flow?
Based on Bernoulli principle, pressure in small diameter pipe is different wit big diameter. This difference is used to determine fluid flow inside pipe. By using Bernoulli principle the difference of pressure can be converted to different velocity between big pipe and small pipe. This velocity difference is then used to determine flow rate (volume rate). Moreover, it also can be used to determine flow rate (mass rate) by using relation between density and volume of the fluid.
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