ELECTRICAL ANALOG FOR RADIATION HEAT TRANSISTER

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP89B00487R000400730009-3
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 6
• Document Creation Date: December 22, 2016
• Document Release Date: June 18, 2012
• Sequence Number: 9
• Publication Date: March 2, 1960
• Content Type: MISC

Declassified in Part - Sanitized Copy Approved for Release 2012/06/18: CIA-RDP89B00487R000400730009-3
IN jai?NTIdN REPORT
SUBMITTED BY
DESCRIPTIVE TITLE E/eG-rrc
D406
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Briefly, What Problem Were You Working On?
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Ho~:.,Does the Invention Work in Solving This Prablem?
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.Circumstances Surrounding.the Invention. Notebooks for reference
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-= Declassified in Part - Sanitized Copy Approved for Release 2012/06/18: CIA-RDP89B00487R000400730009-3
 Declassified in Part - Sanitized Copy Approved for Release 2012/06/18: CIA-RDP89B00487R000400730009-3
INTER-OFFICE CORRESPONDENCE
NORWALK,. CONN.
March 2, 19 60
SUBJECT: Invention Disclosure
FILE NO-: Ref: Docket #406
STAT
Electrical Analog For Radiation Heat Transfer
THE. PERKIN-ELMER CORPORATION
.be used by itself or with others of its kind.
When engineers learned that entirely different physical systems could
be described mathematically by a common set of equations, they realized that one
system could be used to simulate the other. Very often it is much easier to con-
struct and test the simulated system instead of the real system of interest.
In problems of heat transfer, this technique has been quite helpful.
By letting electrical. voltage be the analog of temperature and electrical current
be the analog of heat flux, one can construct an electrical system in which the
flow of electricity simulates the flow of heat in the analogous physical system.
One serious limitation, however, has hindered the full utilization of.
this technique. The electrical systems which had been developed before now could
.simulate heat. transfer by convection and by conduction but not by radiation.*
The device being disclosed here has been developed to fill this gap.
It normally would be used as part of a larger analog system but could conceivably
The heart of the simulator is a resistor which is made to conduct
electrical current in a manner analogous to thermal radiation. The novel feature
is the manner by'which the conductivity of this resistor is controlled.
Principle of Operation
The net radiated heat flux between two bodies is:
k (T14- T24)
.where k is a'constant and T and T2 are the temperatures of bodies #1 and #2,
respectively. The current lowing between two electrical points through a
resistor R is:
In special cases, radiation transfer could be
limited a p licat~
RECEI
MAR. 3 19` (
PATENT DE _- PT.,
approximated, but this had
(1
THE PER~tiid-ELMER CORP.
.. .. .. FG-20M-2/67-ET
Declassified in Part - Sanitized Copy Approved for Release 2012/06/18: CIA-RDP89B00487R000400730009-3 ; ,.:; ;
 Declassified in Part - Sanitized Copy Approved for Release 2012/06/18 : CIA-RDP89B00487R000400730009-3
March.2, 1960
where V. and V. are the voltages at points #1 and #2, respectively... Equation (1
may be made.to.look like,equation (2 by the identity
then equation (2 would be completely analogous to equation (l,and we have an
electrical analog for thermal radiation.
In this simulator, the resistor, R, is a photoconductive resistor
element which is. placed inside a light-tight box and is arranged so as to be
-.illuminated by a small incandescent electric light. The lamp is powered by an
amplifier which is,in turn,controlled by the voltage at points #1 and #2. This is
illustrated in figure 1.
Consider first a simplified case. The voltage VL at the lamp is the
sum of V1 -~ V2. If the lamp filament has.a constant resistance re, then power to
the 'lamp ;,(and. hence from it) is..
(5
The conduction of the photoconductive resistor is linearly proportional
to the energy (in.c.ertain wave lengths, incident on it. Thus
1 = kl (V + V )2,.-! V;'
,where kl is a constant. Equation (6 shows a dependence on V1 and V2 which
is. similar to the dependence of 1/R upon T1 and T2-in equation (4.
Although equations (6 and (4 are not exactly of the same form, the'
observed dependence of 1/R upon V1 and V2 more . nearly. matches equation (4
.instead of equation (6, and, thus, one obtains the desired effect. Many additional.
.:effects cause this to be soi, At higher input voltages, the emission spectrum
of the lamp moves more towards the region of the photoconductor spectral sensitivity,
in which turn,'makes the observed,exponent inn equation approximately 3 instead of 2
as - was obtained by the simplified analysis.
Declassified in Part - Sanitized Copy Approved for Release 2012/06/18: CIA-RDP89B00487R000400730009-3
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 Declassified in Part - Sanitized Copy Approved for Release 2012/06/18 CIA-RDP89B00487R000400730009-3
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March 2, 1960
Second, the lamp resistance increas t hi h
es
a g er temperatures, but this
effect. is relatively small.
Third, by using an amplifier of the type shown in figure 2, the output
voltage VL can.be made to be proportional to V1 + V2 when V1 is nearly equal to.
2
V2, but proportiorAto the larger of V1 or V2 when one'is much less than the
relationThese three effects make the photoconductor behave according to the
2 + V 2
k (V
, (V
+
V2)
1
1 2
Controlling current with a photoconducting resistor in order
to simulate physical processes by analogy.
Controlling the photoconductor by varying both intensity and
spectral distribution of incident light.
3. Using the nonlinear characteristics of the amplifier in figure 2
to improve sca ay..y the accuracy of the lamp excitation system.
Two devices the= form were constructed at P ki E1
"
a good approximation,.and the analogy is complete.,
Conclusions
The novel features of this device are:
&
for us
simulator used to study heat transfer problemsinvolvi
ngnheatetransferebyn a
radiation. They operated in an entirely satisfactory manner. In the particular
,problem studied, the coefficient k in equation (l,varied slightly with temperature,
and we found that this effect. could Al 211 1,e n4.....1 ,..._-2 L-- _- _ -
STAT
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 Declassified in Part - Sanitized Copy Approved for Release 2012/06/18: CIA-RDP89B00487R000400730009-3
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n Part - Sanitized Copy Approved for Release 2012/06/18: CIA-RDP89B00487R000400730009-3
Declassified in Part - Sanitized Copy Approved for Release 2012/06/18: CIA-RDP89B00487R000400730009-3 ,>: