What is the K value for a pipe transition between two different diameters?

In summary: The K-factor for each length of straight pipe is f (L/D). Call one K-factor K-3 for the 3-cm. pipe and the other K5 for the 5-cm. pipe.Now, according to the relation##\frac{K_a}{K_b}=(\frac{d_a}{d_b})^4##If you make Ka = K3, then Kb becomes K5. Putting the value of the K-factor for the 5-cm. straight pipe into the relation will give you the equivalent K-factor as if the 5-cm. pipe was actually 3-cm. pipe.
  • #1
ipocoyo
8
0

Homework Statement



Screen_Shot_2016_06_16_at_8_30_06_pm.png

Homework Equations


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The Attempt at a Solution


Usually we are given a table, but how do we calculate the loss coefficient between 2 different pipes with different diameters? In this case, between the 5 and the 3 cm^2 pipes?
 
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  • #2
ipocoyo said:

Homework Statement



Screen_Shot_2016_06_16_at_8_30_06_pm.png

Homework Equations


N/A

The Attempt at a Solution


Usually we are given a table, but how do we calculate the loss coefficient between 2 different pipes with different diameters? In this case, between the 5 and the 3 cm^2 pipes?
The K-factors for a given diameter of pipe are proportional to the fourth power of that diameter, as described in this article:

http://www.pipeflowcalculations.com/pipe-valve-fitting-flow/flow-in-valves-fittings.php

The usual method is to express the K-factors or equivalents for the system in terms of one common pipe size.
 
  • #3
You should be able to look up the equation for the loss coefficient for the transition between two pipes of different diameter. Do you not have a textbook?
 
  • #4
  • #5
Chestermiller said:
You should be able to look up the equation for the loss coefficient for the transition between two pipes of different diameter. Do you not have a textbook?

My textbook just says to refer to appendix for K values. It doesn't say anything between the transition of 2 different pipes with different diameters.
 
  • #6
ipocoyo said:
So the answer between the transition of two pipes is (0.03/0/05)^4 ?

The K-factor for each length of straight pipe is f (L/D). Call one K-factor K-3 for the 3-cm. pipe and the other K5 for the 5-cm. pipe.

Now, according to the relation

##\frac{K_a}{K_b}=(\frac{d_a}{d_b})^4##

If you make Ka = K3, then Kb becomes K5. Putting the value of the K-factor for the 5-cm. straight pipe into the relation will give you the equivalent K-factor as if the 5-cm. pipe was actually 3-cm. pipe.
 
  • #7
ipocoyo said:
My textbook just says to refer to appendix for K values. It doesn't say anything between the transition of 2 different pipes with different diameters.
What geometries does it give K values for?
 

FAQ: What is the K value for a pipe transition between two different diameters?

What is the loss coefficient K in a pipe?

The loss coefficient K in a pipe is a dimensionless value that represents the amount of energy loss in a fluid flow system due to friction and other factors. It is used to calculate the pressure drop in a pipe and is an important parameter in fluid dynamics and pipe design.

How is the loss coefficient K calculated?

The loss coefficient K is calculated using a variety of methods, such as empirical equations, experimental data, and computational fluid dynamics (CFD) simulations. The most common method is to use the Darcy-Weisbach equation, which takes into account the pipe geometry, fluid properties, and flow rate to determine the value of K.

What factors affect the loss coefficient K in a pipe?

The loss coefficient K is affected by several factors, including the roughness of the pipe wall, the diameter and length of the pipe, the viscosity of the fluid, and the velocity of the flow. Other factors such as fittings, bends, and valves in the pipe also contribute to the overall value of K.

Why is the loss coefficient K important?

The loss coefficient K is important because it allows engineers to accurately predict the pressure drop and flow rate in a pipe system. This is crucial for designing efficient and cost-effective piping systems in industries such as oil and gas, water treatment, and HVAC. It also helps in troubleshooting and optimizing existing pipe systems.

Can the loss coefficient K be reduced?

Yes, the loss coefficient K can be reduced by minimizing the factors that contribute to it, such as using smoother pipes, reducing the number of fittings and bends, and selecting a lower viscosity fluid. CFD simulations can also help in optimizing pipe designs to minimize the value of K and improve the efficiency of the system.

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