Hollow rotating shaft operates like a heat pipe, with a small, sealed-in inventory of fluid that transfers heat by vaporizing at the hot end and condensing at the cold end. This heat pipe utilizes large centrifugal forces for pumping the condensate, and rotation to enforce liquid-vapor separation

Gray, V. H.

English

NASA Technical Reports Server

December 1969	 Brief 69-10684 
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. 
A Rotating, Noncapillary Heat Pipe 
Heat Out
	 Heat In 
LL 
Liquid
N 
Vapor 
Shaft
• Condensate
Return 
Condenser	 Evaporator 
Schematic Diagram of Rotating Heat Pipe 
The problem: 
To utilize rotational accelerations for transferring 
heat very rapidly and efficiently. 
The solution: 
A hollow shaft that operates like a heat pipe, with a 
small, sealed-in inventory of fluid that transfers heat 
by vaporizing at the hot end and condensing at the 
cold end. Whereas present heat pipes use capillaries 
to pump the condensed fluid back to the evaporator 
end, this rotating heat pipe pumps with centrifugal 
forces. Consequently, the rotating heat pipe over-
comes the limitations of capillary heat pipes, specifi-
cally, their relatively low levels of heat flux and their 
poor performance when pumping against gravity. 
These shortcomings result from the very low pressure
heads that can be generated in capillaries by liquid 
surface-tension forces. The rotating heat pipe, how-
ever, makes use of large centrifugal forces for pump-
ing the condensate, and also utilizes rotation to 
forcibly separate vapor from liquid in the evaporator 
and the condenser regions. These capabilities improve 
the overall thermal efficiency. 
Now it's done: 
The hollow shaft has a slight internal taper from one 
end to the other. The heated end (evaporator) has the 
larger inside diameter, and the cooled end (condenser) 
is slightly smaller in inside diameter. The liquid in-
ventory rotates with the heat pipe and collects as an 
annulus at the larger end. Heat transferred through 
the wall evaporates or boils some of the liquid, gene-
(continued overleaf) 
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Aeronautics and Space Administration. Neither the United States	 information contained in this document, or warrants that such use 
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rating vapor that flows toward the center of rotation 
and axially toward the cooled end of the heat pipe. 
Here, the vapor condenses on the cooled walls and the 
liquid condensate is centrifuged back to the evapora-
tor end along the diverging inside walls. Heat is 
thereby transferred from end to end by virtue of the 
heat of vaporization with very small overall tempera-
ture drop. Heat fluxes are attainable in order of 
magnitude greater than in comparable capillary heat 
pipes. 
Notes: 
I. The principles of the rotating heat pipe can be ap-
plied to a variety of shapes other than hollow shafts, 
such as hollow discs, toroids and cylinders with 
concave ends. 
2. Applications abound for both internal heating and 
cooling of rotating parts: for example, cooling of 
high speed drills and saws; cooling of brakes, tires, 
bearings, gears, and rollers; heating of immersed 
elements and circulating blades; abstracting heat 
from reactors, furnaces and combustion chambers; 
cooling of motor rotors, gas-turbine blades, air-
conditioners, etc.
3. This device is relatively insensitive to gravity and 
random accelerati'ons, and thus can be applied on 
earth, in space, or in vehicles and machines where 
motion and orientation may vary. 
4. Requests for further documentation may be directed 
to:
Technology Utiliiation Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B69-10684 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code GP, 
Washington, D.C. 20546.
Source: Vernon H. Gray

Lewis Research Center

(LEW-10298) 
Brief 69-10684	 Category 05


A rotating, noncapillary heat pipe

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