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hi, i want to know about the barometric leg which we kept for condensor by providing 34ft ht. i know that 34ft of water is equal to 760 mmhg. but i want to know that why we provide 34ft ht and why 1 atm is equal to 760mmhg.how can it measured?
please gie me reply.
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Baromtric Leg
Started by virat_chem05, Dec 15 2005 01:51 AM
6 replies to this topic
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#2
gvdlans
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Posted 15 December 2005 - 03:15 AM
Maybe this helps:
Hydrostatic pressure = density x liquid height x gravitational constant
Therefore, a column of 34 feet (=10.4 m) of water (density is 1000 kg/m3) exerts a pressure of 1000 x 10.4 x 9.8 = 101920 N/m2 (~1 atm)
A column of 760 mm (=0.76 m) of Mercury (Hg, density is 13500 kg/m3) exerts a pressure of 13500 x 0.76 x 9.8 = 100548 N/m3 (~1 atm)
Hydrostatic pressure = density x liquid height x gravitational constant
Therefore, a column of 34 feet (=10.4 m) of water (density is 1000 kg/m3) exerts a pressure of 1000 x 10.4 x 9.8 = 101920 N/m2 (~1 atm)
A column of 760 mm (=0.76 m) of Mercury (Hg, density is 13500 kg/m3) exerts a pressure of 13500 x 0.76 x 9.8 = 100548 N/m3 (~1 atm)
#3
Guest_virat_*
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Posted 16 December 2005 - 11:33 PM
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thanks for the ans. but i want to say that in industry , i found that to creat vaccum where they use ejector, after that they put condensor and they provide it at 34-36 ft . u mean to say that if they provide less hight, no condensate will come out? plz explain me.......
thanks for the ans. but i want to say that in industry , i found that to creat vaccum where they use ejector, after that they put condensor and they provide it at 34-36 ft . u mean to say that if they provide less hight, no condensate will come out? plz explain me.......
#4
gvdlans
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Posted 17 December 2005 - 05:33 AM
Virat,
I have no idea what you are trying to ask. Please spend some more time asking your question in proper English.
I have no idea what you are trying to ask. Please spend some more time asking your question in proper English.
#5
nareshakurathi
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Posted 24 December 2005 - 03:02 AM
i understand u r question . where they r providing 36 ft rather that 34 because for safety to maintain that liquid pool in any condition .if the seal brokens then u r entire vacuum system will be disturbed,ok.putting 36 ft will not provide any harm to u r system i think u got it
#6
aliadnan
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Posted 24 December 2005 - 11:38 AM
Hi
I have a question regarding height of condensor. If we are dealing with vacuum in the condensor then the height of condensor plays a role? If yes then why? Can anyone explain it to me clearly in simple words.
I have a question regarding height of condensor. If we are dealing with vacuum in the condensor then the height of condensor plays a role? If yes then why? Can anyone explain it to me clearly in simple words.
#7
mbeychok
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Posted 24 December 2005 - 05:07 PM
Aliadnan:
If you want the condensed liquid to flow out of the condensor by gravity alone (i.e., no pump), then you need to have the condenser elevated so that the liquid drain pipe has enough hydrostatic head to overcome the difference between vacuum within the condenser and the external atmospheric pressure.
If you have a complete vacuum in the condenser (i.e., 0 psia or 0 Pascals absolute or 0 bara) and the condensed liquid is water, then you need at least 34 feet of water hydrostatic head. If the condensed liquid was mercury, then you need at least 760 mm of liquid mercury hydrostatic head. Etc., Etc., .....
This is what gvdlans tried to tell you in his response earlier in this thread.
If you use a pump to remove the condensed liquid directly from the condenser and the pump is specified correctly, then you do not need a barometric leg.
If you want the condensed liquid to flow out of the condensor by gravity alone (i.e., no pump), then you need to have the condenser elevated so that the liquid drain pipe has enough hydrostatic head to overcome the difference between vacuum within the condenser and the external atmospheric pressure.
If you have a complete vacuum in the condenser (i.e., 0 psia or 0 Pascals absolute or 0 bara) and the condensed liquid is water, then you need at least 34 feet of water hydrostatic head. If the condensed liquid was mercury, then you need at least 760 mm of liquid mercury hydrostatic head. Etc., Etc., .....
This is what gvdlans tried to tell you in his response earlier in this thread.
If you use a pump to remove the condensed liquid directly from the condenser and the pump is specified correctly, then you do not need a barometric leg.
