Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

Register Log in
  • Congratulations TugboatEng on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Bicycle Fluid Trainer Question

Status
Not open for further replies.
Killroy1999

Killroy1999

Mechanical
Joined
Nov 9, 2013
Messages
6
Location
US
A bicycle fluid trainer works with the bicycle tire turning a rotor in a sealed chamber of oil.

I'm trying to calculate pressure rating of the seals based on the following inputs.

There is some air in the chamber to allow for oil expansion and I know the cold temperature and oil volume, so I can calculate the change in volume of the oil base on the hot temperature which can get up to 250 degrees F in extreme testing on the test stand.

So the air is compressed by the oil expansion and its heating up. I cant use the ideal gas law because air at 250 F is not a ideal gas.

What do I use?

Thanks!
 
Sort by date Sort by votes
I need some help solving for pressure.

Say the initial conditions are:
Temperate= 291 K
Pressure= .1 mPa (atmosphere)
Air Volume= 45 ml

Final conditions:
System heated to 374 K
Oil expands and compresses air volume to 35 ml

What is the pressure?
Thanks

 
Upvote 0 Downvote
Most of us here do not usually provide answers to such problems. It's kind of like doing your homework for you. What would you learn from that. We try to teach you enough about your specific problem so that you can go away and solve it yourself, thereby earning your own money.
 
Upvote 0 Downvote
Well, from your link I see a look up table for Z, but it is dependent on pressure which is what I am trying to solve for.

Also, there is no mansion of humid air, which I think would play a large role.

It does say that the ideal gas law is probably a good approximation below 2 atm, I think I am below 2 atm, so ideal gas law it is?
 
Upvote 0 Downvote
If the final pressure is less than 5 atmospheres I would ignore compressibility.

Calculate the pressure using the reduced gas volume due to the expanded oil volume and also assuming the gas has reached the oil's temperature. Then using the ideal gas equation, calculate the pressure. If both assumed and calculated pressures are nearly equal, the pressure value you assumed was a good one. Leave it at that, or do another iteration.

Your gas is probably in contact with oil, not water, so if anything it has oil vapor in it, not water. Worry about that later. If you have a gas mixed with other vapors, compressibility becomes much more complicated. Hire a chem E if the answer is that critical.
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

A
  • Locked
Compressor regarding question
Replies
3
Views
3K
georgeverghese
georgeverghese
JustSomeRoark
  • Locked
  • Question Question
Question on centrifugal compressor startup sequence
Replies
3
Views
927
LittleInch
LittleInch
Metalmasterscm
  • Locked
  • Question Question
Pressure regulator question
Replies
7
Views
440
Compositepro
Compositepro
pyMorty
  • Locked
  • Question Question
Supercritical fluid reciprocating compression
Replies
4
Views
364
rotw
rotw
kelleyl
  • Locked
  • Question Question
Air Receiver Question
Replies
3
Views
294
zdas04
zdas04

Part and Inventory Search

Sponsor

Back
Top