Specific Heat Capacity measurement 2

[will123123]

I need to get values of the specific heat capacity from a couple of gearbox oil samples at a range of temperatures (100-160°C). Initial measurements have been made using a modulated DSC, but the scatter in the results is excessive - this method is known to suffer from errors of at least 10%. Can anyone suggest a method with much improved accuracy.

Thank you

 

[btrueblood]

Standard calorimetry (i.e. bulk calorimetry) may be more what you are looking for? Although, DSC is supposedly much more accurate than 10%. Is it possible the scatter is due to real physical differences in the samples, e.g. due to breakdown of the oil?

 

[Compositepro]

At 160C vaporization of the sample is likely to be a problem. Are you using a pressurized cell?

 

[will123123]

Yes - sealed pans are being used during the tests. The results look good during a single test, ie. a consistent rise in SHC with temperature and there is no anomaly at the higher temperatures. Therefore I believe it is unlikely there is breakdown of the oil. The problem is scatter from one test to the next and I do not believe this is due to sampling errors (ie incomplete mixing of the oil).

 

[TVP]

There are three ASTM standards for determination of specific heat, two of which use a form of DSC:

ASTM D2766 - 95(2009) Standard Test Method for Specific Heat of Liquids and Solids

http://www.astm.org/Standards/D2766.htm

ASTM E1269 - 11 Standard Test Method for Determining Specific Heat Capacity by Differential Scanning Calorimetry

http://www.astm.org/Standards/E1269.htm

ASTM E2716 - 09 Standard Test Method for Determining Specific Heat Capacity by Sinusoidal Modulated Temperature Differential Scanning Calorimetry

http://www.astm.org/Standards/E2716.htm

 

[EdStainless]

When we did DSC on volatile samples we used an Ar pressurized cell.
Repeatability was a fraction of 1%.

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