Tests on heat pipes determine operational limits, external boundary conditions, noncondensable gas effects, startup behavior, and geometric configurations. Experiment consists of design, construction, and testing of an apparatus for measuring wick properties, conventional heat pipes and coplanar heat pipes

Barsch, W. O.

Schoenhals, R. J.

Viskanta, R.

Winter, E. R. F.

English

NASA Technical Reports Server

September 1971
	 Brief 71-10353 
NASA TECH BRIEF 
Marshall Space Flight Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a aubscription basis from the National Technical Information 
Service, Springfield; Virginia 22151. Requests for individual copies or questions relating to the. Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Literature Review and Experimental Investigation of Heat Pipes 
A literature review and experimental investigation 
were conducted on heat pipe theory and design, 
including operating limits, external boundary 
conditions, noncondensable gas effects, startup 
behavior, and geometric configurations. The heat 
pipe is a closed structure containing an evaporator, 
a condenser, a wick, and a working fluid (liquid 
plus vapor). The system transfers thermal energy 
from the evaporator by vaporizing the liquid, trans-
porting and condensing the resulting vapor (with 
concomitant release of its latent heat to the con-
denser), and subsequently returning the condensate 
to the evaporator by capillary action of the wick. 
The work reported took into consideration the 
characteristics of various working fluids and wick 
materials, as well as applications of the heat pipe 
principle for temperature control, heat-flux con-
version, and thermal conductance control. 
The experimental program consisted of three 
parts: (I) The design and construction of an apparatus 
for measuring wick properties; (2) the design, 
construction, and testing of a conventional 
cylindrical heat pipe; and (3) the testing of a coplanar 
heat pipe. In the second phase, wall temperatures 
were measured along the pipe as a function of both 
heat input and pipe orientation. The temperatures 
at the evaporator end were found to be extremely 
sensitive to orientation. 
The tests were conducted in order to determine 
the extent of separation (concentration changes) of 
the fluid components (water and methanol) in a 
two-component heat pipe. Temperature was measured 
under the wicks and in the vapor space for various 
combinations of heat input to the evaporator,
orientation, and methanol mass fraction. It was 
found that stratification affected the temperature 
distribution within the vapor. Temperature profiles 
in the vapor indicated that only a partial separation 
of components had occurred. 
It was generally concluded from this study that, 
while the heat pipe may be advantageous for high-
temperature and space applications, it should not 
be regarded as the ultimate solution to many ordi-
nary heat transfer problems where greater economy, 
performance, and reliability are possible with more 
conventional heat transfer methods. 
Note: 
The following documentation may be obtained 
from:
National Technical Information Service 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.95) 
Reference: 
NASA-CR- 102943 (N71-14065), The Study 
and Classification of Two and Multi-
Component High Thermal Conductance 
Devices 
Patent status: 
No patent action is contemplated by NASA. 
Source: W. 0. Barsch, E. R. F. Winter,

R. J. Schoenhals, and R. Viskanta of

Purdue University
under contract to
Marshall Space Flight Center 
(M FS-2 1074) 
Category 03 
This documefct 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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Literature review and experimental investigation of heat pipes

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