Re: Calculating specific gravity of superheated steam

Question: Calcula


Kevin,

You're not going to like my answer, but get yourself to a library; 
preferably a chemistry library, but your engineering library and the main 
library should have what we need as well.  If you've never looked at a CRC 
handbook before, you'll be amazed what kinds of information they have.  
Specifically, you're looking for:


     "CRC handbook of chemistry and physics", By the Chemical Rubber
         Company.  Cleveland, Ohio, CRC Press., 1998-1999 75th edition.
         Library of Congress #: QD65 .H35

They also publish smaller handbooks of Applied Engineering Science, 
Antibiotic Compounds, Engineering and Medicine and Biology, Flowering, 
Laser Science, Mathematics, just to name a few.  The Chemistry and Physics 
one will certainly have what you're looking for.  CRC puts out a new 
edition just about every year (I have the 66th edition from 1986), but very 
little data changes from year to year.  It is full of just the kind of 
information you want, including definitions, tables of data, conversion 
factors, etc., and every other kind of typically useless information you'd 
typically never think you'd need (including the typical pH of foods, 
structures of organic compounds, alloy composition, you name it).

According to my CRC handbook specific gravity is defined as "the ratio  of 
the mass of a body to the mass of an equal volume of water at 4C or other 
specified temperature.  Dimensions, unity."  So it seems to me that what 
you need is the vapor pressure of water as a function of temperature and 
pressure; the CRC handbook has this data over a wide range of conditions.  
(Since I don't know your operational pressure range I figured it would be 
easier for you to look it up than for me to guess exactly what you'd need).

The CRC handbook also has an almost limitless array of conversions factors 
where you'll find the answer to the second part of your question.  (For 
example, 1 cubic foot/hour = 0.4719474 L/min).

If all else fails, call the manufacturer of the valve and ask them about 
it.  Surely they'd have the answer.

Best of luck,
Dr. Jim Kranz