Monel has been found to be ideal material for matrix of regenerators operating in temperature range of 325 K to 50 K. Two best shapes are as spheres or as wire mesh. For given size of regenerator, spherical shots are preferable for low-temperature operation. At high temperatures, mesh would be superior by virtue of its lower flow resistance

Browning, C. W.

English

NASA Technical Reports Server

March 1974	 B73-10462 
NASA TECH BRIEF 
Goddard 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 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. 
Monel-Shot and Screen Regenerators 
Regenerators are thermal-energy storage devices used 
to transfer energy to and from the working fluid of 
several devices. They are frequently used in cryogenic 
engines or refrigerators. A high-temperature fluid flows 
through the regenerator and gives up a major portion of 
its heat. The fluid emerges from the regenerator at a 
substantially lower temperature. When the flow direc-
tion is reversed, the fluid passes through the re-
generator to pick up heat and then reemerges at the 
high temperature. 
A certain amount of heat loss occurs during this 
cycle. The loss, however, can be reduced by choosing a 
regenerator-matrix material with a high energy-storage 
capacity and by shaping and sizing the material for 
efficiency. 
Monel has been found to be an ideal material for the 
matrix of regenerators operating in the temperature 
range of 325 K to 50 K. The two best shapes are as 
spheres or as wire mesh; each shape has its own 
advantages. 
With packed spheres, the void fraction is lower 
(about 0.38). Thus, a greater mass of matrix material 
can be packed in the same volume. This increases the 
heat transfer and increases the pressure drop per unit 
length of regenerator. Screens have a comparatively 
low resistance to flow, but their void fraction is 
higher. The reduced flow resistance decreases the 
pressure drop through the matrix, which decreases the 
driving force on the fluid and this decreases heat loss.
For a given size of regenerator, spherical shot are 
preferable for low-temperature operation. At low tem-
peratures, the specific heat of metals is low, and the 
increased mass of matrix material is necessary to get a 
large enough total-heat capout. At high temperatures, 
the mesh would be superior by virtue of its lower flow 
resistance. 
Notes: 
1. A detailed study has been made of the design, devel-
opment, and fabrication of a miniature Vuffleumier 
Cryogenic using Monel regenerators. 
2. Requests for further information may be directed to: 
Technology Utilization Officer 
Goddard Space Flight Center 
Code 207.1 
Greenbelt, Maryland 20771 
Reference: T5P73.10462 
Patent status: 
NASA has decided not to apply for a patent. 
Source: Calvin W. Browning of
The Garrett Corp.
under contract to
Goddard Space Flight Center 
(GSC-1 1593) 
S Category 03,06 
This document was prepared under the sponsorship 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 
Goverrmient nor any person acting on behalf of the United States 	 will be free from privately owned rights.
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Monel-shot and screen regenerators

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