Thin cleans better, allows longer OCI than thick!

[Gokhan]

It's like radioactive decay. Only fractions are relevant. For small NOACK, the exponential time constant is approximately equal to 1 hr / NOACK. In other words, NOACK is the inverse of the exponential time constant with the units of 1/hr. Both the time constant and NOACK characterize the oil, just like the time constant, which is related to the half life by a factor of ln 2, characterizes the radioactive material.

 

[Shannow]

Was going to summarise the thread from the originally linked hydroprocessed oil qualities, and what they are claimed to prove with regard to the thread title...and onwards and upwards...

But decided against it...utter waste of time


The Units of NOACK is the time waster..."look over there, a bunny" that distracts us from the whole trainwreck.

 

[CR94]

Originally Posted By: SR5
Evaporate Loss (Noack) is the weight loss % after 1 hour at 250 C. ...
To me that makes the units of Noack kg per second or something similar like grams per hour. But Mass per Time in some form.
Suppose hypothetically it's an extreme "dumbbell" blend, such that all the volatile stuff comes out within the first 20 minutes. If you bake it another 2 hours or 9 hours, nothing happens. Is it a rate of x% per 9 hours? Methinks not. It's just a percentage, exactly as is customarily reported, so no time units.

 

[Gokhan]

Fractional evaporation = 1 - exp(-t*NOACK), with t expressed in hours.

For x
So, if t * NOACK
Now, API doesn't allow NOACK > 0.15 1/hr. Therefore, everything makes sense for all API-allowed NOACK values and t < 1 hr, for which the approximation holds very well.

Therefore, for all API-allowed NOACK values, NOACK represents a characteristic time constant of the oil.

 

[Shannow]

Originally Posted By: Gokhan
Fractional evaporation = 1 - exp(-t*NOACK), with t expressed in hours.

For x
So, if t * NOACK
Now, API doesn't allow NOACK > 0.15 1/hr. Therefore, everything makes sense for all API-allowed NOACK values and t < 1 hr, for which the approximation holds very well.

Therefore, for all API-allowed NOACK values, NOACK represents a characteristic time constant of the oil.


What ???

Suggest adding a link here...

 

[Tom NJ]

Noack only measures the lighter components that will volatilize in one hour, which includes some antioxidants. Extrapolating that rate is absurd; if the test was run for a second hour the results would be dramatically different.

 

[Garak]

Originally Posted By: Gokhan
NOACK has the units of 1/time, even though Garak objected to it, saying it should be dimensionless. That's because 2 hours is arbitrary -- plenty of time for gathering reliable, repeatable data. It could be 1 hour, 1 min, or even 1 second. It's the rate of evaporation.

I'm still disputing that. It's testing methodology, and not a rate. Unless the rate is linear, or at least of some known curve, a time component is useless. As it stands, it's no different than blood pressure testing, which takes a specific amount of time, and then tossing in a time component into the reading, after the fact.

 

[ZeeOSix]

Maybe almost oils burn off most of what's going to burn off after 60 minutes at 250 C. Otherwise, wouldn't you think the Noack test duration would have been made longer if the burn-off rate was still cruising along pretty good after 60 minutes.

https://en.wikipedia.org/wiki/Noack_volatility_test

 

[SR5]

Originally Posted By: Tom NJ
Noack .... if the test was run for a second hour the results would be dramatically different.

Thanks Tom

 

[SR5]

All up I think we are reading too much into this Noack test, it's a standardize engineering test, with pass and fail marks, probably based on real word experience of what a reasonable oil should be, and used as a quality control test.

To say it offers insight into the chemical structure of the base oils is pushing it too far.

To say it's units (whatever they are) relate to other parameters (like pressure, CCS, stress or whatever) and can be mathematically combined with other units to explain some microstructural behavior at the molecular level, is just pushing it way too far and very much out of context.

 

[CR94]

Originally Posted By: Garak
... Unless the rate is linear, or at least of some known curve, a time component is useless. ...
Agree. I gather Gokhan assumes the rate with respect to time is a typical exponential decay curve (like radioactive decay, for example). Why isn't clear.

 

[ZeeOSix]

Originally Posted By: SR5
Originally Posted By: Tom NJ
Noack .... if the test was run for a second hour the results would be dramatically different.

Thanks Tom


Anyone have any official test data that shows that? Could be that 90+% of what's going to vaporize at 250C is burned off in the first 60 minutes.

 

[Shannow]

Originally Posted By: ZeeOSix
Anyone have any official test data that shows that? Could be that 90+% of what's going to vaporize at 250C is burned off in the first 60 minutes.


Here's the standard
https://pentasflora.com/wp-content/uploads/2014/02/D5800-NOACK-Volatility.pdf

And a Selby paper on the development of the revised method
https://www.savantgroup.com/media/SAE-Pa...rement-1993.pdf

No "boil off curves" that I can find anywhere, but the Selby paper shows some before and after GC...with a bell curved distribution on the dino oils, and a peaky distribution on the synthetics (multiple viscosity pure basestocks to get the required behaviour.)

 

[Tom NJ]

Originally Posted By: ZeeOSix
Originally Posted By: SR5
Originally Posted By: Tom NJ
Noack .... if the test was run for a second hour the results would be dramatically different.

Thanks Tom


Anyone have any official test data that shows that? Could be that 90+% of what's going to vaporize at 250C is burned off in the first 60 minutes.


What I meant is that the rate in the second hour would be dramatically different than the rate in the first hour.

 

[ZeeOSix]

Interesting papers, thanks for the links Shannow. Tom NJ, I agree with your last comment.

 

[Y_K]

Originally Posted By: Tom NJ
Noack only measures the lighter components that will volatilize in one hour, which includes some antioxidants. Extrapolating that rate is absurd; if the test was run for a second hour the results would be dramatically different.


One of the most elegant ways to remind that little knowledge is dangerous. Thank you

 

[Gokhan]

Originally Posted By: Tom NJ
Noack only measures the lighter components that will volatilize in one hour, which includes some antioxidants. Extrapolating that rate is absurd; if the test was run for a second hour the results would be dramatically different.

Did you understand my calculation?

Was I extrapolating? On the contrary I was interpolating for very small time [exp(-t/T) ~ 1 -t/T for t/T
Of course, different things in the oil will evaporate at different rates. However, for better oils, where NOACK is low, the approximation to relate NOACK to a characteristic time constant should hold.

 

[Shannow]

should hold...is a pretty unscientific term.

It's already been demonstrated that your index doesn't even work for the supersyn PAO, "pure" basestocks, so it would appear that "should" actually means "doesn't really"

 

[nap]

Looks to me that in addition to reading issues (with the API standards), Gokhan also has difficulties with comprehending the differences between a cumulative value, an instantaneous value and the rate of change of a value....

Or maybe Shannow is right and Gokhan just pretends it as he sees fit to supporting his allegations.....

 

[Gokhan]

Originally Posted By: nap
Looks to me that in addition to reading issues (with the API standards), Gokhan also has difficulties with comprehending the differences between a cumulative value, an instantaneous value and the rate of change of a value....

Or maybe Shannow is right and Gokhan just pretends it as he sees fit to supporting his allegations.....

What degree do you and Shannow hold? I have a PhD in science, in addition to bachelors in engineering.

Can you even write down an equation relating these quantities to each other?

I have written it and related the rate of evaporation to NOACK if NOACK is small. I have no idea what you're talking about.

Enough with the trolling! You've been trolling me ever since I corrected your uninformed post about 0W-20 and TEOST 33C.