• Support PF! Buy your school textbooks, materials and every day products Here!

Vacuum pressure

  • Thread starter nastaynas
  • Start date
  • #1
2
0
This is NOT a "problem", it's a rather a question.
Let's say I've got a vacuum chamber, and I suck the air out of it using a vacuum pump that is capable of doing -200 Kpa. Let's also say that there is a valve on this chamber. After a full vacuum has reached, I open this valve WHILE the pump is still running (thus creating a suction at the valve opening). What would be this pressure of suction? Is it -100 Kpa (100 Kpa which is atmospheric pressure, subtract 200 Kpa which is pump capability) OR is it just 0 Kpa since we are at vacuum?
 

Answers and Replies

  • #2
Delphi51
Homework Helper
3,407
10
Initially the differential across the inlet valve will be 1 atmosphere (100 KPa).
Then the pressure in the chamber will rise so the differential will be less than 100 KPa. The amount will depend on the rate of flow in (how large the inlet valve opening is) and the rate of pumping out. The -200 KPa rating just means the pump can achieve a near vacuum when exhausting from a closed chamber to a 2 atmosphere destination - it says nothing about how much gas can be exhausted per second.
 
  • #3
2
0
I see. Makes sense.
So let's say the inlet valve of 1/4" and the pump is also hooked up to a 1/4" outlet: does this mean that rate is the same thus the pressure difference remains constant?

What if the inlet valve is hooked up to a hose which leads to a bucket of oil (thus sucking the oil into the chamber)?
What would happen to the pressure inside?
 

Related Threads for: Vacuum pressure

  • Last Post
Replies
3
Views
3K
Replies
4
Views
3K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
1
Views
979
  • Last Post
2
Replies
26
Views
821
  • Last Post
Replies
9
Views
4K
  • Last Post
Replies
2
Views
3K
Top