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NFPA Exam CWBSP Topic 2 Question 7 Discussion

Actual exam question for NFPA's CWBSP exam
Question #: 7
Topic #: 2
[All CWBSP Questions]

To what exponent is the pipe diameter raised when calculating friction loss through a pipe with the Hazen-Williams formula?

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Suggested Answer: D

You can see in the above equation that if Q is raised to the power of 1.85 in the above equation, this has the effect if the flow is doubled and all other factors remain constant, the friction loss would increase by almost four times. If the flow were to triple, the friction loss would almost be nine times greater. You can also see that the pipe diameter D is raised to the power of 4.87 and is in the denominator on the right-hand side of the equation. Therefore any increase in the pipe size will reduce the friction loss if all other factors remain the same. If the diameters double, the friction loss will be reduced by almost a factor of 1/32 likewise, if the pipe diameter is tripled, The friction loss would be reduced to about 1/243 of its original value.

https://canutesoft.com/hydraulic-calculation-for-fire-protection-engineers/the-hazen-williams-formula-for-use-in-fire-sprinkler-systems#:~:text=You%20can%20also%20see%20that,other%20factors%20remain%20the%20same.


Contribute your Thoughts:

Dominic
2 days ago
Wait, isn't it 4.52? I remember that from my fluid dynamics class, but I could be wrong...
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Lilli
7 days ago
I'm pretty sure it's 1.85, that's the classic Hazen-Williams exponent we all know and love.
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Isadora
10 days ago
I think it's raised to the power of 4.87.
upvoted 0 times
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