Of course density changes with temperature. But the specific gravity of a fluid at a specified reference temperature doesn't change when that fluid is at a different temperature.
So, this usage sounds like one of those times when things are used differently than originally intended, as so...
I see that the definition of API gravity is just an equation that uses the specific gravity of a liquid at 60degF with respect to water at 60degF. However, looking at the usage of API gravity in handbooks and other publications, I see mention of the API gravity changing with the temperature of...
I agree with Jim that you probably have some type of experimental scatter. Did the tests have data at more than one pressure drop ratio? If the ratios are well spaced and the Cv is relatively constant between them, the test should be good. Of what order is the discrepancy?
Cv tests run on...
