Any physicists out there?

[RogerS]

I've just put in a new central heating system and was idly wondering what the volume of the system was. As I was letting the air out after pressure testing, the thought occured to me that maybe there was a formula that would tell me that if it took X seconds to drop from A bar down to B bar and the temperature was Y degrees, then the volume is Z? Boyles' law? Charles Law?

 

[gasmansteve]

Hi RogerS
Blimey thinking back to me college days the combined Boyles/Charles law (for gases) was (If memory serves :wink: )
P1V1/T1=P2V2/T2
where P1 =Old pressure (Absolute I think)
V1 = Old volume
T1 = guess what .....Old temperature
P2 = new pressure etc etc
V2 =......
T2 = .....
This gives you the new volume for a new pressure or temperature but no mention of time in seconds not sure how you could factor time into it.
Not sure if that helps much??.
Cheers
Steve

 

[Steve Maskery]

Can't help you Roger, but Coles' Law is white cabbage carrot, and mayo, if that helps.

Well someone had to say it.
S

 

[RogerS]

Hi RogerS
Blimey thinking back to me college days the combined Boyles/Charles law (for gases) was (If memory serves :wink: )
P1V1/T1=P2V2/T2
where P1 =Old pressure (Absolute I think)
V1 = Old volume
T1 = guess what .....Old temperature
P2 = new pressure etc etc
V2 =......
T2 = .....
This gives you the new volume for a new pressure or temperature but no mention of time in seconds not sure how you could factor time into it.
Not sure if that helps much??.
Cheers
Steve

Hi Steve

Thanks for the suggestion. The tricky thing is factoring time in, as you say. I'm sure there must be a formula somewhere!

 

[dickm]

I'm not a physicist (though I've been married to one for 45 years) but I think the missing bit concerns Stokes law, which is to do with flow of fluids. Basically, the time to lose pressure will depend to some extent on the nature of the orifice through which the fluid is flowing out. And it will also be affected by temperature, but I can't give you the formula.