Computer programs find the direct view factor from one surface segment to another using the Monte carlo technique, and the radioactive-transfer coefficients between surface segments. An advantage of the programs is the great generality of problems treatable and rapidity of solution from problem conception to receipt of results

Mc Williams, J. L.

Scates, J. H.

English

NASA Technical Reports Server

February 1969	 Brief 69-10038 
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. 
Monte Carlo Direct View Factor and Generalized Radiative 
Heat Transfer Programs 
The problem: 
To develop a method to find the view factor from 
a surface segment to another surface segment and to 
find Radiative-Transfer Coefficients between the sur-
face segments. 
The solution: 
A package of computer programs was written: (I) 
to find, using the Monte Carlo technique, the "black 
body" view factor from one surface segment to another 
surface segment defined on a primary surface; and (2) 
to define the primary surfaces (collection of simple 
geometric objects) in three-dimensional space, and 
find the radiative-transfer coefficients from a surface 
segment defined on a primary surface to all other sur-
face segments defined in a real enclosure. 
How it's done: 
The Monte Carlo Direct View Factor Program uses 
the Monte Carlo technique to find the "black body" 
view factor from a surface segment defined on a pri-
mary surface to another surface segment defined on a 
primary surface. The collection -of geometric objects 
(primary surfaces) includes a sphere, cylinder, cone, 
disc, and parallelogram. 
The function of the program is numerical evalua-
tion of the integral: 
A 1 F 1 = AF 1 = ,J'dA1(1) 
Surface I 
.JdA() B (7 1
	
) H (
	 ) 
Surface J 
where R,,
	
are vectors represcnting points on surfaces 
I. J of area A 1 .	 U	 is a blocking factor which 
is unity if	 can "see ­ 'x, and zero otherwise. 
= 1 .	 i -) /i 1 —,where r, 1and
ii denote unit surface normal vectors.
The segment (or node) object numbers are obtained 
from the view factor command. The nodes are located 
in the definition table. From the nodes come the pri-
mary surface object numbers and K values. The pri-
mary surfaces are located in the definition table and 
copied into temporary storage. An error message is 
printed if nodes or primary surfaces are missing. The 
areas of the nodes are calculated and the canonical 
forms are generated for the subroutines: 
1. Reset the interation sums and parameters 
2. N = N+l 
3. Generate random points and 
Two random numbers are obtained from a uniform 
distribution. These numbers are modified so that the 
points generated on the different surface window will 
cover the surfaces evenly. The surface points and nor-
mals are obtained using the subroutines. 
The Generalized Radiative Heat Transfer Program 
finds radiative-transfer coefficients from a surface 
segment defined on a primary surface to all other 
surface segments defined in a real enclosure. The pro-
gram permits radiation heat transfer analysis for en-
closures containing surfaces which have, in general, 
both diffuse and specular reflectivities. 
A geometric configuration is defined by the cus-
tomer, consisting of a set of defining primary surfaces 
and their nodes. A primary surface may be a paral-
lelogram, disc, cylinder, sphere, or cone. Nodes are 
defined as subsurfaces on the primary surfaces. One 
input data case consists of a geometric configura-
tion together with commands for finding Script F's 
between objects within the configuration. Commands 
are executed as they are encountered; when a Script 
F command is encountered, the following operations 
are performed: The node summation areas are cleared 
(continued )verIl) 	 — 
Now
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=19690000038 2020-03-16T17:51:02+00:00Z
to zero. These areas consist of "Script-F" sums for 4.	 Inquiries concerning this program may be directed 
I and 2 wavelength nodes along with force and torque to: 
sums. .The presence of these areas is entirely depend- COSMIC 
entubnthe	 of node being encountered. The .type Computer Center 
counter for the total number of rays considered is set University of Georgia 
to zero. The counter is incremented by I. Athens, Georgia 30601 
Reference: B69-10038 
Notes: 
1. The program is written in FORTRAN IV language Patent status: 
for use on the IBM 360 computer. No patent action is contemplated by NASA. 
2. At most, no more than 100 primary surface tests Source: James H. Scates and Jerry L. McWilliams 
may be made per second. In addition, there is a of The Boeing Company V 
relatively high machine-time cost for high-precis- under contract to 
ion parametric results. Marshall Space Flight Center 
3.	 An advantage is the great generality of problems (MFS-15051) 
treatable and rapidity of solution	 from	 problem 
conception to receipt of results. 	
V V 
H-	
•VV	 V 
Brief 69-10038
V	 . . 	
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Monte Carlo direct view factor and generalized radiative heat transfer programs

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