Computer program obtains the real-gas isentropic flow functions and thermodynamic properties of gases for which the equation of state is known. The program uses FORTRAN 4 subroutines which were designed for calculations of nitrogen and helium. These subroutines are easily modified for calculations of other gases

Johnson, R. C.

English

NASA Technical Reports Server

July 1969	 .	 Brief 69-10222 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Computer Program for High Pressure Real Gas Effects 
.
This program has potential widespread use in 
industries concerned with real gas effects. 
The problem: 
A need existed to calculate the mass-flow rate of 
helium and nitrogen at pressures greater than 100 x 
10 newtons per square meter. 
The solution: 
A computer program which will obtain the real-gas 
isentropic flow functions and thermodynamic proper-
ties of gases for which the equation of state is known. 
How it's done: 
The program uses FORTRAN IV subroutines which 
were designed for calculations of nitrogen and helium. 
These subroutines can be easily modified for calcula-
tions of other gases. 
The program was used to calculate a critical flow 
factor that permits the isentropic mass-flow rate of 
nitrogen and helium through critical flow nozzles to 
be calculated from plenum conditions. In addition, 
the results include the nozzle throat velocity, the 
compressibility factor, the entropy, the enthalpy, 
the specific heat at constant pressure, the specific-
heat ratio, and the ratios of throat to plenum pressure, 
density and temperature. These results are tabulated
as functions of the plenum pressure and temperature. 
The calculations cover a temperature range from near 
condensation to 400K and a pressure range from 0 to 
300 x 10 newtons per square meter (approximately 
300 atm). 
The program permits three different sets of indepen-
dent variables. In addition to the plenum pressure and 
temperature, the other independent variable is either 
the nozzle exit pressure, the nozzle exit Mach number, 
or the nozzle exit temperature. 
Notes: 
I. This program is written in FORTRAN IV for use 
on the IBM 7094. 
2. Inquiries should be made to: 
COSMIC 
Computer Center 
University of Georgia 
Athens, Georgia 30601 
Reference: B69-10222 
Patent status: 
No patent action is contemplated by NASA. 
Source: Robert C. Johnson 
Lewis Research Center 
(LEW- 10820) 
Category 06 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
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Computer program for high pressure real gas effects

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