- #1
wombat
- 4
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Hi All,
I've come across something that surprised me but I'm sure has a logical explanation...
I have a two small ID tubes that have exactly equal impedance to air flow (for the purposes of the discussion the flow is 2ml/min). I connect them in series with one end of the system exposed to a constant vacuum of 10kPa below atmosphere and the other end open to atmosphere.
[Tube A] [Tube B]
[Atmosphere] ========= + ========= [-10kPa Vacuum]
^
[ Pressure Read Here]
I measure the pressure between the two tubes relative to atmosphere and I don't get -5kPa (ie half of -10kPa), instead I get something less, like -4.8kPa. Why is there an uneven drop in pressure through the two tubes. I assume it's to do with changing density but I can't put it into words.
Thanks in advance,
Wombat
I've come across something that surprised me but I'm sure has a logical explanation...
I have a two small ID tubes that have exactly equal impedance to air flow (for the purposes of the discussion the flow is 2ml/min). I connect them in series with one end of the system exposed to a constant vacuum of 10kPa below atmosphere and the other end open to atmosphere.
[Tube A] [Tube B]
[Atmosphere] ========= + ========= [-10kPa Vacuum]
^
[ Pressure Read Here]
I measure the pressure between the two tubes relative to atmosphere and I don't get -5kPa (ie half of -10kPa), instead I get something less, like -4.8kPa. Why is there an uneven drop in pressure through the two tubes. I assume it's to do with changing density but I can't put it into words.
Thanks in advance,
Wombat