Fabrication of expansion joint, vibration isolator device with sufficient cross sectional area for high thermal conductivity is discussed. Device consists of multiple layers of metal foil which may be designed to meet specific applications. Thermodynamic properties of the device and illustration of construction are provided

Elliott, D. H.

Wallace, S. D.

English

NASA Technical Reports Server

October 1972	 B72-10612 
NASA TECH BRIEF 
Marshall Space Flight Center 
NASA Tech Briefs announce now 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. 
Flexible Thermal Device 
Stacked Foil Elements - Shape Of	 Face Sheets: Thin Sheet Metal 
Device Optional - Designed To Suit
	
Same Material As Foil-Required 
Space Available And Spring	 To Fasten Foil Together And 
Constant Required	 Provide Mechanical Interface 
Ends Compressed To 
j Dimension Less ThanStacked Foil Thickness
To Insure Optimum
Heat Transfer 
so
The problem: 
Existing expansion-joint/vibration ,
 isolator methods 
such as wound coils, standard springs, nonmetallic vibra-
tion isolators, and slip joints are ineffective heat transfer 
devices because they lack sufficient cross-sectional area, 
do not meet minimum length requirements, have low 
thermal conductivity, or have discontinuous heat paths. 
The solution: 
Fabricate a device that consists of multiple layers of 
metal foil that have been tailored to meet a specific 
requirement. 
How it's done: 
The device consists of multiple layers of metal foil that 
have been tailored to meet a specific requirement. At the 
heat input and output ends of the device, the foil layers 
are compressed to a dimension less than their nominal 
stacked thickness and held in this position either by 
welding or mechanical fasteners. This compression re-
moves air from between foil layers, removes surface 
irregularities in individual foil elements, and thus insures 
optimum heat transfer. Given the geometrical envelope 
available and the quantity of heat to be transferred, the 
number, thickness, and material of the foil elements may 
be determined to achieve the desired flexibility. For 
example, given a quantity of heat (Q) to transfer within a 
specified temperature drop (AT) the following relation-
ship holds Q = KAT/L where K is the thermal con-
ductivity of the foil material, A is the cross sectional area 
of the stacked foil layers, and L is the average length of a 
single foil element' For optimum heat transfer and 
availability in foil form, a material such as aluminum with 
its high thermal conductivity is usually desirable. The 
length and cross sectional area may now be determined to 
satisfy envelope and heat transfer requirements. 
Having the required geometry, the desired flexibility 
(spring constant) may be achieved by selecting the proper 
number and thickness of individual elements. The thick-
ness of each element need not be the same. In fact, it may 
(continued overleaf) 
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https://ntrs.nasa.gov/search.jsp?R=19720000611 2020-03-17T03:36:40+00:00Z
be desirable from operational considerations to have one 
or more elements made from thin gauge sheet stock. The 
sheet stock element may be designed to flex through the 
desired travel at a stress lower than its yield strength to 
assure elastic recovery to its original configuration. The 
device may also be used as a low spring constant vibration 
isolator and as a suppression device for vibration induced 
noise. 
Notes: 
1. Information concerning this innovation may be of 
interest to machine and structural designers.
2. Requests for further information may be directed to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Code A&PS-TU 
Marshall Space Flight Center, Alabama 35812 
Reference: 1372-10612 
Patent status: 
NASA has decided not to apply for a patent. 
Source: S. D. Wallace, and D. H. Elliott of 
McDonnell Douglas Corp. 
under contract to
Marshall Space Flight Center 
(MFS-2 1630) 
B72-10612	 Category 04


Flexible thermal device

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