3 replies to this topic

[curious engineer]

What is the difference of API and SG_60/API60 in the mass density unit of Hysys?

[djack77494]

curious,
Your question is difficult to understand and is certainly not tied to Hysys in any way. The definition of specific gravity (sometimes called relative density) is the density of the fluid of interest divided by the density of water. Generally both are defined to be at a standard temperature such as 60F. Denity expressed in degrees API is related to specific gravity by the equation:

Sp.Gr. = 141.5 / [131.5 + degreesAPI]

The degrees API by convention implies a fluid temperature of 60F.

You may note that a fluid of 10 degreesAPI has a specific gravity of 1.000 (same as water). Higher degreesAPI = lower density. Good references for these definitions can be had easily using your search engine (i.e. google).

[curious engineer]

Thank you djack.

In mass density in hysys there are many units available such as kg/m3, API, etc. The unit API in hysys also means API 60 (measured at 60F) however there is also a unit "SG_60/API60". This unit when converted to API 60 have different numberical value. Im wondering, what does the unit "SG_60/API60" means.

[joerd]

It has to do (I think) with the following solution (108997) from AspenTech's knowledgebase:

What do the units for Density/Specific Gravity in HYSYS mean?
Solution:

SG_H2O60api and SG_H2O60nbs are the ratios of the density of the liquid stream to the density of water measured at 60F.