Hydroelectric turbine.. net head question.

  • Thread starter Thread starter imatreyu
  • Start date Start date
  • Tags Tags
    Head Net Turbine
Click For Summary

Discussion Overview

The discussion revolves around understanding the concept of net head in the context of hydroelectric turbines, specifically how to calculate it given the pressures at different points in the penstock. The scope includes theoretical considerations and practical implications related to hydroelectric systems.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant seeks clarification on how to determine net head, expressing confusion about the definitions of gross and net head as well as the role of pressure differences.
  • Another participant explains that net head is calculated by subtracting head losses due to friction and turbulence from gross head, noting that additional information about the penstock is necessary for accurate calculations.
  • A different participant proposes a theoretical approach by assuming no losses in the penstock and questions how pressure would be incorporated in this simplified scenario.
  • Another reply emphasizes the importance of consulting the turbine manufacturer for calculations related to potential power output, linking head to pressure through a specific equation.

Areas of Agreement / Disagreement

Participants generally agree on the definitions of gross and net head, but there are differing views on how to approach the calculation of net head, particularly regarding assumptions about losses in the penstock. The discussion remains unresolved regarding the best method to incorporate pressure into the calculations.

Contextual Notes

Participants mention the need for additional information about the penstock's characteristics and potential losses, which are not fully addressed in the discussion. There is also an acknowledgment of the complexity involved in calculating net head accurately.

imatreyu
Messages
79
Reaction score
0
Sorry, not so much of a problem, more. . I need to understand.


Homework Statement


Finding the net head.

This website (http://www.oregon.gov/ENERGY/RENEW/Hydro/Hydro_index.shtml ), says that the gross or "static" head is the vertical distance between the top of penstock and the point at which the water is discharged from the turbine. It then says "Net head is gross head minus the pressure or head losses due to friction and turbulence in the penstock." I am confused about this statement. How do I go about finding net or "dynamic" head?? If I know the pressure at the top of the penstock, and the pressure at the bottom, how do I apply this information?

Homework Equations


I'm not sure if any of these are relevant. . .

P2-P1 = -y (Z2- Z1)
(The pressure difference between two altitudese. . )

dp= -y dz
(Change in pressure as it is related to change in weight. . .)

y= (density) (g)


The Attempt at a Solution


I'm very confused. . . I just need to understand the method of determining net head.

Thank you in advance!
 
Last edited by a moderator:
Physics news on Phys.org
Quoting from the article, "Net head is gross head minus the pressure or head losses due to friction and turbulence in the penstock. These head losses depend on the type, diameter, and length of the penstock piping, and the number of bends or elbows. So you need a lot more information to calculate it, and even then you'd have to probably get that info on losses from the manufacturer and some tables, or from experimental tests.
 
Well I'm trying to accomplish my project in a theoretical sense. . .


So I guess, assuming no losses due to the penstock (impossible, but I'm trying to simplify it for myself), how would the pressure be factored into the situation?
 
Again, you'll have to consult the turbine manufacturer, who can calculate the potential power delivered by the turbine, based on head (vertical height of water from top of penstock to turbine) and flow rate. The term head is converted to pressure using p =water density (in pounds per cubic foot) times height (in feet), but the given equation factors that in.
 
Thank you!

You really cleared it up for me.
 

Similar threads

Understanding pipe ''head loss''
  • · Replies 2 ·
Replies
2
Views
3K
Calculating Compressor and Turbine Work in an Air Standard Gas-Turbine Cycle
  • · Replies 1 ·
Replies
1
Views
2K
Thermodynamics: Pressure and temperature from turbine
  • · Replies 3 ·
Replies
3
Views
5K
Hydroelectric Power: How Much Water for a 30m Head?
  • · Replies 1 ·
Replies
1
Views
4K
I have attached the problem.I know I need to apply the energy
  • · Replies 1 ·
Replies
1
Views
1K
How to calculate head loss in a pipe with sudden diameter expansion?
  • · Replies 33 ·
2
Replies
33
Views
5K
A 10m long, sloping pipe has an entrance of 100mm
  • · Replies 1 ·
Replies
1
Views
2K
Thermodynamics turbocharger question
  • · Replies 1 ·
Replies
1
Views
3K
Calculate velocity in fluid mechanics question
  • · Replies 1 ·
Replies
1
Views
3K
Concept subsea PHES system, /advice with calculations
  • · Replies 8 ·
Replies
8
Views
2K