# 2K-Method 3K-Method – Local Pressure Drop

## 2K Method – 3K Method

The K-value represents the multiple velocity heads that will be lost by the fluid passing through the fitting. The equation for calculation of pressure loss of the hydraulic element is, therefore: Therefore the equation for calculation of pressure loss of the entire hydraulic system is: The K-value can be characterized for various flow regimes (i.e., according to the Reynolds number), and this causes it to be more accurate than the equivalent length method.

There are several other methods for calculating pressure loss for fittings, and these methods are more sophisticated and also more accurate:

## Summary:

• Head loss of the hydraulic system is divided into two main categories:
• Major Head Loss – due to friction in straight pipes
• Minor Head Loss – due to components as valves, bends…
• A special form of Darcy’s equation can be used to calculate minor losses.
• The minor losses are roughly proportional to the square of the flow rate, and therefore they can be easily integrated into the Darcy-Weisbach equation through resistance coefficient K.
• As a local pressure loss, fluid acceleration in a heated channel can also be considered.

There are the following methods:

• Equivalent length method
• K-method (resistance coeff. method)
• 2K-method
• 3K-method

## Why is head loss very important?

As can be seen from the picture, the head loss is formed key characteristic of any hydraulic system. In systems in which some certain flowrate must be maintained (e.g.,, to provide sufficient cooling or heat transfer from a reactor core), the equilibrium of the head loss and the head added by a pump determine the flow rate through the system.

References:
Reactor Physics and Thermal Hydraulics:
1. J. R. Lamarsh, Introduction to Nuclear Reactor Theory, 2nd ed., Addison-Wesley, Reading, MA (1983).
2. J. R. Lamarsh, A. J. Baratta, Introduction to Nuclear Engineering, 3d ed., Prentice-Hall, 2001, ISBN: 0-201-82498-1.
3. W. M. Stacey, Nuclear Reactor Physics, John Wiley & Sons, 2001, ISBN: 0- 471-39127-1.
4. Glasstone, Sesonske. Nuclear Reactor Engineering: Reactor Systems Engineering, Springer; 4th edition, 1994, ISBN: 978-0412985317
5. Todreas Neil E., Kazimi Mujid S. Nuclear Systems Volume I: Thermal Hydraulic Fundamentals, Second Edition. CRC Press; 2 edition, 2012, ISBN: 978-0415802871
6. Zohuri B., McDaniel P. Thermodynamics in Nuclear Power Plant Systems. Springer; 2015, ISBN: 978-3-319-13419-2
7. Moran Michal J., Shapiro Howard N. Fundamentals of Engineering Thermodynamics, Fifth Edition, John Wiley & Sons, 2006, ISBN: 978-0-470-03037-0
8. Kleinstreuer C. Modern Fluid Dynamics. Springer, 2010, ISBN 978-1-4020-8670-0.
9. U.S. Department of Energy, THERMODYNAMICS, HEAT TRANSFER, AND FLUID FLOW. DOE Fundamentals Handbook, Volume 1, 2 and 3. June 1992.
10. White Frank M., Fluid Mechanics, McGraw-Hill Education, 7th edition, February, 2010, ISBN: 978-0077422417

Minor Loss