Heat pipe can reverse itself with gas reservoir acting as evaporator, leading to rapid recovery from liquid in reservoir. Single layer of fine-mesh screen is included inside reservoir to assure uniform liquid distribution over hottest parts of internal surface until liquid is completely removed

Marcus, B. D.

English

NASA Technical Reports Server

November 1974
	
B74-10216 
NASA TECH BRIEF 
Ames Research Center	 LA 
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 subscription 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. 
Heat Pipe with Hot Gas Reservoir 
The problem: 
To remove condensed vapor from the gas reservoir 
of a heat pipe which is controlled by a condensable 
gas. 
Gas	 Saddle
Thermal Mass 
Feed 
Tube
Fill 
	
Condenser	 Tube 
Evaporator 
Adiabatic Section
The solution: 
Use a heat pipe of hair-pin design with its reservoir 
thermally coupled to an external evaporator. 
How it's done: 
As shown in the diagram, the reservoir is external 
to the evaporator, but because both the reservoir and 
the evaporator are set in an aluminum saddle-like 
base, the reservoir operates at a temperature slightly 
greater than the evaporator. Thus, the heat pipe can 
reverse itself with the gas reservoir acting as the 
evaporator, leading to rapid recovery from liquid in 
in the reservoir. Additionally, there is. included a 
single layer of fine-mesh screen inside the reservoir 
to assure uniform liquid distribution over the hottest 
parts of the internal surface until the liquid is com-
pletely removed; the screen is not in contact with the 
primary wick of the heat pipe itself. 
The heat pipe has a single zone condenser with 
very low radial wick resistance. The wick structure 
consists of inner circumferential grooves cut into the 
stainless steel tube and an axial, homogeneous metal-
felt wick located across the diameter. For better con-
trol of the mass transfer between the reservoir and 
condenser, the feed tube is capped and 0.8-mm di-
ameter holes are drilled in the last 6-mm length of 
the tube; the holes are large enough to prevent for-
mation of significant capillary head because of liquid 
"bridging." 
Notes: 
1. The following documentation may be obtained 
from: 
National Technical Information Service 
Springfield, Virginia 22151 
Single copy price $3.00 
(or microfiche $0.95) 
Reference: NASA CR-i 14530 (N73-15957), 
Theory and Design of Variable Conductance 
Heat Pipes. 
2. No additional documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94035 
Reference: B74-10216 
Patent status: 
Inquiries concerning rights for the commercial use 
of this invention should be addressed to: 
NASA Patent Counsel 
Mail Code 200-1 1A 
Ames Research Center 
Moffett Field, California 94035 
Source: Bruce D. Marcus of

TRW Systems Group, TRW, Inc.

under contract to

Ames Research Center

(ARC-10847) 
w	 Category 03 
This document was prepared under thesponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States	 will be free from privately owned rights.
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Heat pipe with hot gas reservoir

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