Fluid mechanics - u tube manometer

The other equation, ΔP=g*ρmercury*Δh, does not take into account the density difference and may not provide accurate results. In summary, to find the pressure after the obstacle, you can use the equation ΔP=g*Δρ*Δh, where Δh is the height difference measured by the u tube manometer, Δρ is the density difference between the solution and the mercury, and g is the acceleration due to gravity.
  • #1
Dell
590
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dont have a picture to show,

a solution is pumped through a pipe with an obstacle in it, to find the difference in the pressure on either side of the obstacle, a u tube manometer with mercury is fitted to it and a height difference of 19cm is measured. what is the pressure after the obstacle if the solution is pumped in at pressure P1?

given

Δh=0.19m
ρsolution=1070kg/m3
ρmercury=13520kg/m3

now in my lecture notes i have 2 equations, one being
ΔP=g*Δρ*Δh
and the other being
ΔP=g*ρmercury*Δh

so P2=ΔP+P1 (P2<P1)

which one do i need to use, since ρsolution<<ρmercury i get similar results but which is correct?
 
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  • #2
The correct equation to use is ΔP=g*Δρ*Δh. This equation takes into account the density difference between the solution and the mercury, which is necessary in this situation.
 

1. What is a u tube manometer and how does it work?

A u tube manometer is a device used to measure fluid pressure. It consists of a U-shaped tube filled with a liquid, usually water or mercury, and connected to the fluid system being measured. The difference in height of the liquid in the two arms of the tube indicates the difference in pressure between the two points.

2. What are the units of measurement for a u tube manometer?

The units of measurement for a u tube manometer are typically in inches or millimeters of the liquid column. However, they can also be converted to other units of pressure, such as psi or kPa, depending on the specific application.

3. How is a u tube manometer different from other types of pressure measuring devices?

A u tube manometer is a simple and inexpensive device compared to other types of pressure measuring devices. It does not require any external power source and can measure both positive and negative pressures. However, it is limited in its measurement range and accuracy compared to more advanced instruments.

4. What are the applications of u tube manometers?

U tube manometers are commonly used in industries such as HVAC, chemical processing, and fluid mechanics laboratories to measure pressure in pipes, vessels, and other systems. They are also used in medical settings to measure blood pressure.

5. How do you read and interpret the measurements on a u tube manometer?

To read a u tube manometer, you must first determine the reference or zero point, which is where the liquid levels are equal in both arms of the tube. The difference in height between the liquid levels in the two arms indicates the pressure difference. The liquid level in the arm connected to the higher pressure source will be higher, and the difference between the two levels can be used to calculate the pressure difference.

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