I suspect I know the answer to this, but hoping someone may know something I don't here.

Is there a way I can determine the specific heat capacity at constant pressure (Cp) of an oil if I know the density, temperature and viscosity?

The oil I am interested in: http://www.bakerprecision.com/neo/75w90rhd.htm

The company is only small and hasn't got a value of Cp as far as I can tell, I have contacted them. They are unlikely to have tested it in my experience of dealing with them.

As far as I know this could only be done by experimental correlation, and there is no universal equation.

Is there any theory you know that can estimate the value of Cp of an oil from basic properties without experimentation?

I know: Dentity, viscosity and surface tension at room temperature. Plus viscosity at various other temperatures.


There is no practical way to do this.

It is possible to estimate specific heats from first principles using computer simulation and quantum mechanics. There are also some semi-empirical "laws" which apply to particular situations, such as materials whose elements have large atomic numbers, (bigger than iron, and therefore irrelevant for lubricating oil) or at very low (cryogenic) temperatures. None of those is applicable to gear oil.

Measuring specific heat is not difficult - you could do it yourself with a "kitchen table" experiment. Put a known mass (or volume) of oil in a thermally insulated container (e.g. a thermos flask), apply a known amount of heat (for example using an electrical resistor immersed in the oil), and measure the temperature change.

  • $\begingroup$ This is what I suspected. Thanks for your feedback. $\endgroup$ – Petrichor Mar 21 '19 at 10:20

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.