# Orifice Pressure and Flow drop

• JJ1989
In summary: L = (Vs2/2g)×{1-(As/Al)}2hL = (Vs2/2g)×{1-(As/Al)}2hL = (Vs2/2g)×{1-(As/Al)}2hL = (Vs2/2g)×{1-(As/Al)}2hL = (Vs2/2g)×{1-(As/Al)}2hL = (Vs2/2g)×{1-(As/Al)}2hL = (Vs2/2g)×{1-(As/Al)}2In
JJ1989
0http://math.stackexchange.com/questions/946493/solve-for-pressure-drop-across-and-orifice#
I'm running 1/2" pipe but the only way to connect a 9/16" flow switch is with a 1/4" adapter. I'd have to go from 1/2" down to 1/4" to the 9/16" flow switch down to 1/4" back to 1/2".

I was wondering if this would cause a large pressure drop but I used this online calculator and was wondering if anyone could verify these numbers:

Calculation output

Flow medium: Water 20 °C / liquid

Volume flow: 2 l/min

Weight density: 998.206 kg/m³

Dynamic Viscosity: 1001.61 10-6 kg/ms

Element of pipe: Orifice sharp-edged

Dimensions of element: Diameter of pipe D1: .5 in.

Diameter of pipe D2: .25 in.

Velocity of flow: 0.86 ft./s

Reynolds number: 3330

Velocity of flow 2: 3.45 ft./s

Reynolds number 2: 6661

Flow: turbulent

Absolute roughness:

Pipe friction number:

Resistance coefficient: 30.68

Resist.coeff.branching pipe: -

Press.drop branch.pipe: -

Pressure drop: 22.14 lbw./sq.ft.

0.15 psi

I've also looked at a flow rate calculator and was wondering if the down size in the piping would affect the flow rate substantially? I'm really trying to stay at 2L/min.

Last edited by a moderator:
JJ1989 said:
0http://math.stackexchange.com/questions/946493/solve-for-pressure-drop-across-and-orifice#
I'm running 1/2" pipe but the only way to connect a 9/16" flow switch is with a 1/4" adapter. I'd have to go from 1/2" down to 1/4" to the 9/16" flow switch down to 1/4" back to 1/2".

I was wondering if this would cause a large pressure drop but I used this online calculator and was wondering if anyone could verify these numbers:

Calculation output

Flow medium: Water 20 °C / liquid

Volume flow: 2 l/min

Weight density: 998.206 kg/m³

Dynamic Viscosity: 1001.61 10-6 kg/ms

Element of pipe: Orifice sharp-edged

Dimensions of element: Diameter of pipe D1: .5 in.

Diameter of pipe D2: .25 in.

Velocity of flow: 0.86 ft./s

Reynolds number: 3330

Velocity of flow 2: 3.45 ft./s

Reynolds number 2: 6661

Flow: turbulent

Absolute roughness:

Pipe friction number:

Resistance coefficient: 30.68

Resist.coeff.branching pipe: -

Press.drop branch.pipe: -

Pressure drop: 22.14 lbw./sq.ft.

0.15 psi

I've also looked at a flow rate calculator and was wondering if the down size in the piping would affect the flow rate substantially? I'm really trying to stay at 2L/min.
Head Loss due to sudden contraction or sudden expansion in area of flow is given by the formula,
hL = (Vs2/2g)×{1-(As/Al)}2
where the subscripts 's' and 'l' denote the flow properties at the smaller area region and the larger area region respectively.
Substitute the values in this equation and you can determine how much extra pressure difference needs to be created to maintain the same flow as the case when there was no variation in area of flow.

Last edited by a moderator:

## 1. What is an orifice plate and how does it measure pressure and flow drop?

An orifice plate is a thin, flat plate with a precisely measured hole in the center. It is installed in a pipe or duct to measure the pressure and flow rate of a fluid passing through it. As the fluid flows through the orifice, it creates a pressure drop and this drop is related to the flow rate of the fluid according to the Bernoulli's equation.

## 2. What factors affect the pressure and flow drop in an orifice?

The pressure and flow drop in an orifice is affected by the size and shape of the orifice, the fluid properties such as density and viscosity, and the velocity of the fluid passing through it. Other factors that can influence the pressure and flow drop include the presence of obstructions or turbulence in the flow, and the distance between the orifice and the upstream and downstream pipes.

## 3. How is the flow rate calculated from the pressure and flow drop in an orifice?

The flow rate is calculated using the Bernoulli's equation, which relates the pressure drop to the velocity of the fluid. By measuring the pressure drop across the orifice and knowing the other factors such as the orifice size and the fluid properties, the flow rate can be determined using the Bernoulli's equation.

## 4. What are some common applications of orifice plates in industries?

Orifice plates are commonly used in industries such as oil and gas, chemical, and water treatment to measure the flow rate and pressure of fluids in pipelines. They are also used for controlling and regulating the flow of fluids, and for detecting leaks and blockages in pipelines.

## 5. What are some limitations of using orifice plates for measuring pressure and flow drop?

Some limitations of using orifice plates include the pressure recovery, which is the loss of pressure after the fluid passes through the orifice. This can lead to inaccurate measurements. Orifice plates also have a limited range of measurement and are not suitable for measuring high flow rates. Additionally, they can be affected by changes in the fluid properties, such as temperature and viscosity, which can impact the accuracy of the measurements.

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