Computer program calculates the real fluid properties of normal or parahydrogen using a library of single function calls without initial estimates. Accurate transport and thermodynamic properties of molecular hydrogen are needed for advanced propulsion systems

Goldberg, F. N.

Haferd, A. M.

English

NASA Technical Reports Server

September 1968	 Brief 68-10361 
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. 
Real Fluid Properties of Normal and Parahydrogen 
The problem: 
In numerically calculating the real fluid properties 
of normal and parahydrogen, phase boundaries must 
be defined precisely to provide mathematical con-
sistency; good initial estimates must be made; func-
tional definition of properties must remain mathe-
matically and physically consistent; all the saturation 
functions should be available as analytical represen-
tations of region boundaries; and, in the vicinity of 
the critical region, the density calculation must be 
stabilized. 
The solution: 
A computer program, which calculates the real fluid 
properties of normal or parahydrogen, using a library 
of single function calls without initial estimates. 
How it's done: 
All property evaluations involving equations of 
state are preceded by a region-finding process to 
determine which equation of state applies. 
While the region is directly specified by inputting 
temperature and density, indirect methods are used 
for region determination when only the combinations 
of pressure and density or of pressure and temperature 
are input. The region-finding process provides the 
additional information required to initiate iterations 
and to specify boundary values. 
The evaluation of pressure is a direct substitution of 
the values of density and temperature in the appro-
priate state equation. Temperature and density pro-
cedures involve a method of successive approxima-
tions in which a sequence of trial values is generated 
by a Newton-type iteration. 
To eliminate the stability problems of the density 
calculation in the vicinity of the critical region, twc 
sets of density values are fit empirically for isotherms
in the temperature range between 32.5° and 35°K. 
The variation of density with pressure in this region 
is then described by an interpolation formula. A 
modified Benedict—Webb—Rubin equation of state is 
used to calculate the values of pressure with the use 
of liquid or vapor coefficients. The result of this 
technique is a distortion of the vapor—liquid dome. 
Given pressure and temperature, density is cal-
culated, followed by enthalpy, entropy, specific heat, 
and viscosity; or temperature and density are cal-
culated for a given value of pressure with enthalpy or 
entropy. 
When only one parameter can be measured and a 
given phase value of the fluid is to be assumed, pro-
cedures are included to calculate saturated or ideal 
values of pressure and density as functions of tempera-
ture. 
The library of property functions is used primarily 
for parahydrogen composition, however an option for 
normal hydrogen composition in the vapor region is 
included in the procedures for enthalpy, entropy, 
specific heat, and transport properties. 
Notes: 
I. This program is written in Fortran IV for use on 
the IBM 7094 computer. 
2. Performance analysis of advanced propulsion 
systems, which use molecular hydrogen as both 
propellant and coolant, requires accurate know!-
edge of transport and thermodynamic properties 
in both the liquid and the vapor phase. 
3. Inquiries concerning this program may be made to: 
COSMIC 
Computer Center 
University of Georgia 
Athens, Georgia 30601 
Reference: B68-10361
(continued overleul) 
Ank
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.
https://ntrs.nasa.gov/search.jsp?R=19680000361 2020-03-12T05:53:29+00:00Z
Patent status: 
No patent action is contemplated by NASA. 
Source: Frederic N. Goldberg and Angela M. Haferd 
Lewis Research Center 
(LEW- 10458) 
Brief 68-10361	 Category 06


Real fluid properties of normal and parahydrogen

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