Application of Hazen-Williams Formula
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- Опубликовано: 16 окт 2024
- Using a simple example, this videos illustrates the basic steps required to calculate the pressure drop due to friction in a pressurized pipe flowing full of water. The Hazen-Williams formula is one of the most common equations used to calculate friction loss in water distribution networks.
Sir can we apply the same calculation for a vertical pipe.??
Hi, very helpful video, just wondering what is the name of the last equation you have used, the pressure one?
Hello Trisha, I don't think there is a name for the equation. The equation simply converts pressure to pressure head (or vice versa). I hope this helps.
Mr. John,
1) does this formula applicable to water only? or can be used for other fluids? If can be used for other fluids, the unit conversion (k) is remain the same?
2) how do we get the constant roughness coefficient (C) in industry? from the supplier's data sheet?
Thanks.
Hi Zulhanafi,
To answer Part 1), I will reference Computer Applications in Hydraulic Engineering by Bentley:
"The Hazen-Williams equation is most frequently used in the design and analysis of pressure pipe systems. The equation was developed experimentally, and therefore should not be used for fluids other than water (and only within temperatures normally experienced in potable water systems).
For Part 2), C value tables can be found easily online. There may be slight variation from table to table but the values will be close. For example, C for PVC is typically in the region of 140 to 150. New concrete is typically in the region of 120 to 130. Older concrete will be a little rougher and might have a C value closer to 110.
I hope this helps.
John
@@eurekamomentswithjohn6339 thanks john
Hey great video, I just wanted to ask how you would calculated (because I’m in Australia using metric) litres per minute while flowing from having only the nozzle diameter and pressure recorded while flowing?
Hi Benjamin,
I have given both metric and imperial units in the video so you should be able to calculate the pressure loss due to friction in metric. Alternatively, if you have the pressure drop due to friction in a pipe, you can re-arrange the above equation to calculate the velocity in the pipe in m/s. If you have the diameter of the pipe, you can then calculate the area of the pipe (in meters squared). If you multiply velocity by area you will get the flow rate (in cubic meters per second). Cubic meters can then be easily converted to litres per minute (1000 litres in 1 cubic meter and 60 seconds in 1 minute).
In terms of your specific question, I would need more detail. In order to use the Hazen-Williams equation you need more than one pressure reading, you need a pressure drop which is the difference between two readings. It sounds like your example might require the application of Bernoulli's equation (see my videos on Bernoulli's to point you in the right direction).
I hope this helps.
John
Thanks for sharing the formula. However, i read other article that says hazen williams applicable only if the velocity is less than 10ft/sec. In you example, velocity is already at 12.73ft/sec.
Hi brother. Can you please tell me how does this coefficient exactly relate with the head loss. Is it a measure of how rough the surface is? If this is the case, then higher values of this coefficient will indicate lesser head loss, which doesn't seem to make sense. I'd really appreciate a clarification on this.
Hello Muhammad,
The C value relates to the roughness of the material. To give you an example, PVC may have a C value anywhere from 140 to 150. Corrugated steel could have a C value of 60. The higher the C value, the smoother the pipe and therefore the lower the headloss.
I hope the helps.
John
@@eurekamomentswithjohn6339 Thanks a lot for the clarification my friend. Really appreciate it. And keep up the good work.
Thank you and you are welcome.
What is the thump rule for velocity to be taken for external water supply for pressurized line & gravity line
Sorry, I don't understand the question.
thank you for your illustration .but how can we decide if the pipe is totally filled with water or not. especially that such calculations and measures are done in the designing phase of the the project.i mean we do not have any pipe yet ,every thing is on paper
The Hazen Williams equation is appropriate for full pipe pressurized flow. If you are designing a water distribution system, the system will be under pressure.
Thank you a lot for comment.
Very useful indeed.
But I have a question please:
To calculate the head losses we will need to know the geographic high difference between the source of water( the location of the pump ) and the destination of our water network (for instance a tank).
my question is :what if we have a point in our path that its height is lower than the height of the pump ?do we consider this low point as a zero point or what?
Thank you for your time and consideration sir.
@@muhsinalhameed6408 So I would use Bernoulli's equation to compare the location of the pump and the tank. See my video on the use of Bernoulli's equation.
@@eurekamomentswithjohn6339
Thank you
I will watch this video recommended by you Mr.
what happens to the Second in velocity? I get it that the ft gets cancelled but i think the 's' still remains?
Hi Surya,
Remember that the unit conversion constant "k" is built to allow the units to work out. Without "k" the units would not work. But you must be consistent with the units you use in this equation. Everything must be in feet and seconds. No inches allowed.
I hope this helps.
John
@@eurekamomentswithjohn6339 thanks John.
You are welcome Surya.
Very informative, thank you.
Very welcome
could you share your source for this equation?
Hi Rose,
This equation or a manipulation of it can be found in any hydraulics text book. Variations include S (called the friction slope) replacing HL/L (or as I wrote it, Hf/L). Other versions may replace V with Q/A. All of these are legitimate and are simply preferences. I hope this helps.
John
This is Great! THanks a lot!!
You are welcome Markoleous.
How did this 62.4 come?
Hi Divesh,
62.4 pounds per cubic foot is the specific weight of water at standard conditions.
@@eurekamomentswithjohn6339 ok!! Thanks
Pl put this calculation in metric system
You have all the information in the video to do this calculation in metric yourself. Seize the day!
How to get pressure
Sorry Sujeet, I am not sure what your question is. Could you please provide more detail?
Sir please give one example in hazen Williams equation use to and get dia and pressure like this Q=72
And dia=150
Head lose=?
Pressure?
Please describe and detail
I'm not doing this problem it's may be hydraulic calculation hydrant in Fire fighting problem
So Sujeet, if you want the headloss due to friction in a pipe, you calculate Hf in the equation in the video above. If you have the pressure at point A (say 100 psi) and you want the pressure at Point B downstream (assuming no change in elevation), then the pressure downstream is simply 100 psi - 3.03 psi = 96.97 psi (ignoring any minor losses from valves etc.).
If you want to calculate a pipe diameter (D), you must replace V with Q/A in the Hazen Williams equation. Now replace A with the area of a circle (a function of D) and R = D/4 for a full pipe. Assuming you know the allowable pressure drop due to friction and you have all the other parameters, there is only one unknown to solve for i.e. the diameter (D). I hope this helps.
P.S. If you have changes in elevation, you will have to apply Bernoulli's equation (see my videos on Bernoulli's).