Vapor Pressure Of Mineral Oil

I'm surprised if data are not available.

This could make an excellent project for a student or class with access to a vacuum pump, compound pressure gauge, thermometer, Bunsen burner, and various glassware.

Have you looked at a MSDS for mineral oil?

[PDF] MSDS for Mineral oil - ScienceLab

<0.1kPa (@20°C)

It's a start, maybe, but only one temperature--not a whole range.

Thank You Mikerho,

No I wanted to try to find some basic data before contacting anyone, so to have at least a little amount of data.

I was needing it's behavior in a vacuum, to be sure it will not be boiling off in a vacuum of 400 to 500 Pa.

The next thing was viscosity, at temps like dry ice temps or even colder. How thick does it get.

Thanks everyone.

Joe

Hi NSS,

The thing you need to be looking at here is temperature. VP is dependent on temp.

What temps are you looking at?

Temps are a good thing here COLD!!!!!

Average ground temp say 60 deg F

and down!

Like as low as -60 to -70 deg C

I know this will help the anti boiling in a vacuum from happening, but i wonder hat happens to the viscosity too.

Joe

Geez! Where is this application (-94ºF)? Viscosity will almost certainly be more of an issue than VP

WHAT is the application!!???!

Please tell us, in detail, what you are trying to do!

Oh, and do tell what you mean by anti-boiling (yeah, one word, hyphenated)

Thinking in terms of absolute pressure (where 0 psia, bara, etc. represents a volume of space with no matter within it) instead of vacuum/gauge pressure will help you better understand the physics of what is going on in your system.

I Thank everyone here for all the assistance so far,

Applicaton?

It is again for one of our high altitude balloon projects.

We have been doing these flights for 25+ years now, Like this one,

http://www.youtube.com/watch?v=HJ0IT4ZwtSo

And we are working on long duration methods, and planned on using the oi as both a cooling medium for the electronics, as well as a ballast that we can dump some s needed through like a solenoid valve.

So we are looking at both vacuum and temperature issues.

Here is the sounding of temps at what altitue nd pressures,

PRESS HGT(MSL) TEMP DEW PT WND DIR WND SPD HPA M C C DEG M/S E = Estimated Surface Height 982. 272. 15.2 14.7 44.2 4.5 975. 328. 15.0 14.4 45.7 5.9 950. 548. 14.2 13.6 47.4 8.5 925. 775. 17.5 13.5 39.5 5.1 900. 1010. 17.9 11.5 7.0 2.1 850. 1497. 15.3 5.9 269.3 2.0 800. 2008. 12.4 -1.0 249.3 3.6 750. 2546. 9.1 -5.7 247.0 4.2 700. 3113. 5.0 -7.9 261.4 4.1 650. 3712. 0.7 -9.5 271.0 5.7 600. 4350. -3.8 -12.3 269.2 8.4 550. 5030. -8.7 -15.6 269.1 9.4 500. 5762. -13.5 -19.5 267.8 8.0 450. 6556. -18.6 -26.5 280.4 7.7 400. 7422. -25.1 -34.0 295.4 10.0 350. 8377. -32.8 -41.1 291.0 13.0 300. 9443. -41.1 -47.0 290.1 15.1 250. 10656. -50.3 -53.4 289.2 16.6 200. 12078. -60.4 -60.6 269.3 24.7 150. 13845. -63.0 -67.7 279.1 28.5 100. 16390. -59.1 -84.7 261.3 15.2 50. 20680. -61.2 -93.9 91.6 1.8 20. 26469. -53.1 -273.1 74.9 3.8

Wow that got ll corrupted, oh well it was nice rows and coloums.

Joe

I see six columns of data:

1st column = abs pressure in mbar?

2nd column = height (MSL=?)

3rd column = Temp., ºC?

4th column = Dew Point, ºC?

5th column = Wind Direction? (This really is not pertinent to our discussion)

6th column = Wind speed (what are units?)?

Please clarify and confirm.

PRESS HPA
HGT(MSL) METERS
TEMP C
DEW PT C
WND DIR DEG

WND SPD M/S

Why allcaps?

Standard Unit Abbreviations:

hundredths Pascals (I'm assuming) = hPa, not HPA

meters = m, not M

seconds = s, not S

You neet to work on your written engineering communication skills.

Am looking at the data and will get back to you.

Sorry about the all caps,

Hey copy paste from the National weather service sounding from this morning, and thats what ya get.

Hi NSS,

Sorry it took so long to get back to you. The data you sent:

After analyzing the data you sent, you have a 20 to 982 hPa (737 to 15 mmHg) absolute pressure range. These correspond to a 15.2 to -53.1ºC temperature range.

Have you ever heard of poly(dimethylsiloxanes)? These are silicon-based oils that were developed by Dow-Corning. They are (relatively) inert, colorless, nonflammable, and come in a variety of different average MW compositions to fit various applications.

I found a particular formulation from Sigma-Aldrich:

Poly(dimethylsiloxane):

Dow Corning Corp. XIAMETER^® PMX-200 silicone fluid, viscosity 1.0 cSt (25 °C)

Properties:

From your data, this compound would remain a liquid at the temperatures that would be encountered.

For VP data, you could almost certainly get the info by contacting Dow.

I'm also going to send this by PM in case you have already unsuscribed from this thread.

The DOW product sounds interesting. I wonder how it is as an insulator?

Reason asking is Not only am I planning as using it as a ballast, where i can drop some as needed to maintain the flight, (too many details to go into here) But also as a thermal buffer and heat absorber.

While yes it may get to -70 deg C during the flight but we actually have problems on high power payloads with overheating! There is no AIR o pull heat way from heat generating components.

So not only was it going to be a ballast but all the electronics will be submerged in the "OIL" to act as a coolant.

Hi Joe,

I believe that it is a pretty good electrical insulator and a decent thermal conductor/absorber.

As far as releasing some to lighten the load, this is a very low-toxicity compound.

I would really be interested in your evaluation (how well it would fit your application) after talking with Dow about your particular application.

Let me know what you find out!

Mike

I started looking for that tuff and found one site with it, and the "Pour POint" might be a problem?

• Flash Point Open Cup > 326 Deg C
• Flash Point, Closed Cup > 100 Deg C
• Hydrophobic
• Kinetic / Kinematic Viscosity = 100 Centistokes
• Pour Point = -65 Deg C
• Refractive Index = 1.403
• Service Temperature High = 200 Deg C
• Service Temperature Low = -40 Deg C
• Specific Gravity @ 25C = 0.96
• Surface Tension = 20.9 mN/M
• Thermal Conductivity = 0.155 Watts per meter K

But of course I wonder how much lower the pour point drops under the vacuum ya know?

Joe

But of course I wonder how much lower the pour point drops under the vacuum ya know?

Pour point deals with viscosity, and pressure has very little effect on viscosity.

The answer - negligible.

Question: What is a typical duration of a balloon flight?

Typical with no attempts of extending flight time is about 2 hours going up, and 45 minutes or so going down.

It rises at about 750 to 1000 feet per minute, and when the sealed balloon can not expand any more, it pops and then starts an extreme fast decent at the first part of the fall, With the lack of air the parachute has little to no resistance, and some speeds even come close to becoming super sonic even. Not until it gets to around 40K feet does it start to slow own. And finally when near the ground the fall speed is about 1000 to 2000 feet per minute.

If a special balloon is used where it when full and can not expand anymore can vent out some of the lifting gas to become neutral buyoyant and stay there we can get up to 24 hours of flight time if we launch right at sundown. It will rise and fly till the next sundown, where it then looses the solar energy and looses on average about 10% of it's lifting capability, so it will then come down, but if we drop about 10% of the total system's weight, then we can get another 24 hours of flight time.

Joe

Check out this publication: An Outgassing Data Compilation of Spacecraft Materials. It's published by NASA/Goddard.

Over the years, they have tested virtually every material that has gone into space, for free. I sent them hunderds of samples back in the 70's/80's.

William Campbell was my contact then. He may be dead by now.

Anyway it's GSFC/NASA. They were in Greenbelt maryland.

Redfred may have a newer contact or info.

Sorry if this is old news.