Pressure loss on gas pipe (BS 6891 pipe sizing)

[Windy]

Hi,
I'm doing my ACS and have an issue with pressure loss calculations!!
sample question : "what would the pressure loss per meter be on copper tube of 15mm feeding a 12kw (gross) gas hotplate"
I can't for the life of me get the correct answer.....
I nett the hotplate 10.81kw divide that by 9.7 to get 1.11M3/h I then use the pipe length table which shows 15mm 1.3M3/h is maximum length of 12meters.
That means (i think) in 12meters of 15mm copper the loss is 1mb, so if i divide 1 by 12 it gives me 0.0833mb drop per meter ??
but the answer is 0.1042mb

I look forward to your help.....

 

[Harvest Fields]

Hold on. You say you have given the answer at the end??? I haven’t checked it though. So it could be wrong. You having us on here?

 

[ShaunCorbs]

12 kw gross

10.90 kw net

15mm at 10 m with 1 mbar drop 1.1 m3/h

1.1 divided by 10 = 0.11 mbar drop

 

[Windy]

Not having you on, Harvest...
got the question from an online site.....

 

[ShaunCorbs]

Hi,
I'm doing my ACS and have an issue with pressure loss calculations!!
sample question : "what would the pressure loss per meter be on copper tube of 15mm feeding a 12kw (gross) gas hotplate"
I can't for the life of me get the correct answer...
I nett the hotplate 10.81kw divide that by 9.7 to get 1.11M3/h I then use the pipe length table which shows 15mm 1.3M3/h is maximum length of 12meters.
That means (i think) in 12meters of 15mm copper the loss is 1mb, so if i divide 1 by 12 it gives me 0.0833mb drop per meter ??
but the answer is 0.1042mb

I look forward to your help...

you need to divide 1.3 by 12 not 1 = 0.1083 m bar

 

[Windy]

you need to divide 1.3 by 12 not 1 = 0.1083 m bar

where does the 1.3 come from?

 

[ShaunCorbs]

where does the 1.3 come from?

1.3 m3/h at a max length of 12m

So you have 12 m of copper and at the end of it you can pass / pull off 1.3m3/h with your 1 mbar pressure loss

Eg the capacity of the pipe at 12m

 

[Windy]

1.3 m3/h at a max length of 12m

So you have 12 m of copper and at the end of it you can pass / pull off 1.3m3/h with your 1 mbar pressure loss

Eg the capacity of the pipe at 12m

I thought the maximum lengths on the table were equivalent to 1mb drop?

 

[ShaunCorbs]

I thought the maximum lengths on the table were equivalent to 1mb drop?

this will confuse you now 😀

To estimate pressure loss across a pipe leg

(mbar) = (328785 ÷ dia + 7558) x m3/h x m3/h ÷ dia ÷ dia ÷ dia ÷ dia ÷ dia x Length

so

328785 divided by the dia of the pipe (15mm) plus 7558 = 29477

29477 x 1.3 x 1.3 = 49816.13

49816.13 divided by the dia of the tube 5 times then times by the length

49816.13 ÷ dia ÷ dia ÷ dia ÷ dia ÷ dia x 1 = 0.065 mbar per m of 15mm

 

[ShaunCorbs]

this one might be better

 

[Harvest Fields]

this one might be better

Has the site changed shaun? Been having trouble opening attachments like this.

 

[ShaunCorbs]

Has the site changed shaun? Been having trouble opening attachments like this.

No computer normally opens them fine phones can be a bit hit and miss

 

[Windy]

i can't open those.....
but we have a lot of different answer.... 😀

 

[Windy]

if i do the question on my Anton app it comes out at 0.1042
exactly as the question states!! I'm glad its not just me but won't help me for the exam 🙁

 

[ShaunCorbs]

It’s all aprox especially when your working by the m

 

[Windy]

It’s all aprox especially when your working by the m

i get that BUT the answers are 0.1414 0.2296 0.1042 0.0719 so you could choose at least 2 of those answers and maybe even 3 and be aprox (as you say) and fail 🙁 its annoying

 

[ShaunCorbs]

Go back to your tutor and ask them to do a lesson on it

 

[Harvest Fields]

Go back to your tutor and ask them to do a lesson on it

I posted that first then deleted it. 😛😛😛

 

[Windy]

Go back to your tutor and ask them to do a lesson on it

yeah i will.... thanks all hope i haven't be a pain

 

[Riley]

Not at all