Testing technique permits accurate measurement of temperature-dependent thermal conductivity, by virtue of the small temperature differential required across a specimen. The permissible mean insulation temperature ranges from cryogenic to 10 degrees F for the insulation under test

Hale, D. V.

English

NASA Technical Reports Server

August 1969	 Brief 69-10283 
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. 
Automated Measurement of Thermal Conductivity 
Specimen Insulation 
Fig. 1. Longitudinal Section of the Cylindrical Calorimeter 
The problem: 
Development of methods of applying efficient 
thermal-insulating material and predicting its per-
formance. 
The solution: 
A newly developed testing technique permits ac-
curate measurement of temperature-dependent ther-
mal conductivity, by virtue of the small temperature 
differential required across a specimen. 
How it's done: 
The central portion of a 3-inch-diameter fiberglass 
cylinder, 38.5 inches long and having a wall thickness 
of 0.63 inch (Fig. 1), is wound with a heating filament—
the main test heater—that is surrounded by four elec-
trically automated guard heaters that reduce longi-
tudinal temperature gradients to less than 0.050F/foot.
The design permits the derivation of data with a driv-
ing temperature differential of 10°F or less. 
The insulation under test is wrapped circumferen-
tially about the cylinder and diagonally jointed to end 
caps of the same material so that edges of the insula-
tion are eliminated. The temperature differential is 
maintained across the insulation by the heaters inside 
and by a surrounding heated or cooled environmental 
shroud. The resultant thermal system closely approxi-
mates an infinite tube. The insulation-backside pres-
sure is recorded for each specimen with an ion gauge 
installed in the calorimeter's cylinder. The effects of 
gaps of various dimensions in the insulation are evalu-
ated by circumferential slitting of the insulation and 
by forcing of the cut edges apart to various degrees. 
The permissible mean insulation temperature 
ranges from cryogenic to the upper limit for the in-
A
m(continued overleaf) 
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 
Government nor any person acting on behalf of the United States	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19690000283 2020-03-16T17:46:56+00:00Z
sulation under test. The heat flux, per square foot of 
heated area, ranges from about 1 mw to I watt at 
pressures between 10 torr and I atm. The cost of 
preparation of each specimen is about $400; of each 
test, about $200 per datum point. The test operation is 
fully automated, requiring attendance for only from 
3 to 5 hours per 24-hour day. The device has been used 
espeèially for comparing the efficiencies of various 
insulants, and different methods of applying and 
jointing them. 
Notes: 
I. This calorimeter may be of interest to heating and 
electrical engineers, chemists, and biologists. 
2. Documentation is available from: 
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Price $3.00 
Reference: TSP69- 10283
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: D. V. Hale of

Lockheed Missiles and Space Company

under contract to

Marshall Space Flight Center

(M FS-20454)
. 
. 
. 
Brief 69-10283 Category 03


Automated measurement of thermal conductivity

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server