Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

Register Log in
  • Congratulations 3DDave on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Volume correction due to temperature rise? 3

Status
Not open for further replies.
slickstyles5

slickstyles5

Aerospace
Jun 23, 2008
111
Hi Guys,

I'll explain in detail... What I am doing is providing oil to an engine and then I want to measure the oil consumption. Prior to the test I will determine the volume1 and temperature1 (density1). After the test, I will determine the volume2 and temperature2 (density2). The problem is that the temperature at the beginning of the test is not the same as the temperature at the end of the test.

Can I use a simple relationship such as?

Actual Volume after test at initial temperature1 = Volume2 * (Density2/Density1)?

Basically I am converting my volume measured after the test to provide the volume at the initial density prior to the test so I can measure the actual consumption. I can't wait until the oil temperature to decrease, as this would cause too many delays.

Would this work?

Reference:
Thanks

Gabriel
 
Replies continue below

Recommended for you

Sort by date Sort by votes
Look up Charles Law, and also be sure to check if pressure is constant, then you may remove it from the equation.

Also, if it's possible, you can always use the weight which is independent of temperature. But you have to be able to weigh it all.

Charlie
 
Upvote 0 Downvote
Sure it would work. At least, as well as the data you have (every measurement is, after all, another error source) and the validity of the temperature/density correlation you use to your particular oil, and the particular thermal expansion characteristics of your engine.

Hint - you could calibrate the whole thing as a unit, with a fixed, known initial volume of oil, and vary the temperature...

 
Upvote 0 Downvote
Doesn't Charles Law describe the behaviour of gases?

I've been playing with the equation that the OP proposed, and since Volume * density =mass, then dividing that mass at T2 by the density at T1 seems to give you a volume at T1. I like it.

The change in density will be really small for the heat gain in an engine, but if that is the kind of precision your application requires, I'd say that your approach has a lot of merit.

David
 
Upvote 0 Downvote
I was looking for those values earlier in the year for a hydraulic project I was working on. You can usually find the bulk modulus (inverse of compressibility) reasonably easily for hydraulic oils at 60[°]F and atmospheric pressure. Finding values for a rate of change with temperature proved impossible for my project. Maybe there are other sources, but I couldn't find them.

David
 
Upvote 0 Downvote
Wow you guys are great ...

FACS - Yes charle's law is for gases and pressure is constant as my reservoir has a breather (therfore atmospheric pressure).

btrueblood - I like your hint and that is very logical, but would cost us more money to do as we would have to buy a heater. It would be the perfect method though!

zdas04 - I agree that the change will be very small. It's oil and the density (or specific weight) will vary between 58 and 60 lb/ft^3.

BigInch - I will check it out ... The coefficient of thermal expansion of my oil seems to be 0.00045 (avg. between -40 and +300 degF). Now I am unsure what to do with this number, but I will look it up.

Thanks a lot guys!!
 
Upvote 0 Downvote
BigInch - I will stick to my original method, because we are actually losing volume as well because the engine is consumming oil, so the thermal expansion method will not work as wanted.
 
Upvote 0 Downvote
providing the composition doesn't change (only temperature) the proposed rule should be true, i.e. at each temperature the oil has a certain density which you can measure, if the composition changes (with the same initial and final products) then it is still true at measured points, if composition is constant you could try to correlate densities or volumes with temperatures (with a linear or second order polinomial correlation) and in that case perhaps avoid measuring densities...
 
Upvote 0 Downvote
A crazy idea from an old Sructural -

Run the engine up to operating temperature. Drain the oil. Load up your set volume.

Run engine back to opearting and then drain. Compare weigths/volumes

Will this work??
 
Upvote 0 Downvote
FACS - The simple answer is time is money, and it's a production facility that can't afford to wait around for 30 minutes or more...

1gibson - That's another possibility, but more costly for us.

With this, I'll stick to the original equation, and that will work well!!
 
Upvote 0 Downvote
I know Charles Law is for gasses, but if oil has a linear thermal expansion, wouldn't the formula be straight forward?

Just a thought.

I'm sure I saw a paper that taught this Law to students using oil. I could be wrong.

Charlie
 
Upvote 0 Downvote
??? If you know the volume at Temp2, convert that back to the T1 reference and subtract. That gives the volume used at the ref Temp1.

[α]= linear coefficient of thermal expansion 1/F[&deg]

Change in volume = original vol x 3[α] /F[&deg] * (T2-T1)F[&deg]



"I am sure it can be done. I've seen it on the internet." BigInch's favorite client.

"Being GREEN isn't easy." Kermit[frog]
 
Upvote 0 Downvote
BigInch - ??? If you know the volume at Temp2, convert that back to the T1 reference and subtract. That gives the volume used at the ref Temp1.

That's exactly what I will be doing, very simple!! :)
 
Upvote 0 Downvote
Why not weigh it? Then you know how much mass you've lost regardless of what volume it wants to occupy.
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

V
  • Locked
  • Question
Pipe misalignment correction 1
Replies
3
Views
2K
shvet
shvet
jonjose123
  • Question
Settlement of Oil Pipeline due to Leakage of Water Pipeline.
Replies
9
Views
4K
Snickster
Snickster
bizkitgto
  • Question
When would piping need to be replaced due to an overpressure event where the Yield Stress was exceeded?
Replies
15
Views
10K
GD2
GD2
J
  • Question
High Temperature Gasket Torque 2
Replies
8
Views
8K
TugboatEng
TugboatEng
FlashPurp
  • Question
A333 Gr 6 Minimum Temperature 1
Replies
12
Views
8K
MickMc
MickMc

Part and Inventory Search

Sponsor

Back
Top Bottom