P-134, HEAT TRANSFER PROBLEMS

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78-03153A001900040001-9
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 2
• Document Creation Date: December 23, 2016
• Document Release Date: November 21, 2013
• Sequence Number: 1
• Publication Date: March 2, 1955
• Content Type: MEMO

Declassified in Part - Sanitized Copy Approved for Release 2013/11/21: CIA-RDP78-03153A001900040001-9
SECIP
2 March 1955
MEMORANDUM FOR: THE RECORD
SUBJECT : P-1341 Heat Transfer Problems
1. This project was established for the purpose of analyzing
the problem of heat failure of components in concealed electronic
equipment.
2. The adequate dissipation of heat from electronic equipment
is a general problem in the electronic industry. Equipment cooling
is uswoly accomplished by providing holes or slots in equipment
cases to allow for natural convection heat transfer. Small fans for
forced convection cooling are also employed. The problem of cooling
becomes of critical importance in the case of equipment required to
perform in aircraft at high altitudes. Cooling is difficult because
the low pressure air has a low heat capacity. The usual solution
is to pressurize the equipment and provide a heat exthanger with
forced convection on both the hot side and the cold side or to place
the equipment in a pressurized cabin and to cool it via natural or
forced convection. The electronic component manufacturers have also
eased the cooling problem by providing components capable of opera-
tion at relatively high temperatures. In general, most conventional
electronic equipment will cool satisfactorily by natural convection
if it is not overly confined.
3. However, use of electronic equipment for Agency interests
in the field often necessitates concealment and consequently
confinement of radio transmitters, amplifiers, tape recorders, and
other electronic gear. This problem may be attacked in the four
following ways. The first two are essentially preventive methods
aimed at keeping the heat that has to be dissipated to a minimum and
the remaining two methods attempt to dissipate the heat so as to
avoid heat failure of the device.
a. The circuit design of equipment that is to be confined
should be such so as to require aminimum power dissipation
as heat. Excess power output from a concealed transmitter
should be avoided as it requires the dissipation of extra heat.
Some circuit designs require more heat dissipation than otherR
to achieve similar results. As an example, the use of a
resistor to reduce an alternating current voltage requires
considerably more heat dissipation than a transformer.
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Declassified in Part - Sanitized Copy Approved for Release 2013/11/21: CIA-RDP78-03153A001900040001-9
Declassified in Part- Sanitized Copy Approved forRelease2013/11/21 : CIA-RDP78-03153A001900040001-9
Memo for Record 2 March 1955
Subj: P-134, Heat Transfer Problems
b. The circuit design of the equipment should incorporate
efficient low heat dissipating cazponents and components of
adequate size (adequate power rating) should. be used through-
out. As an example, the use of a design incorporating
transistors instead of tubes would require the dissipation
of considerably less beat.
c. Physical arrangement of components within the black
box should be such so as to allow adequate local cooling of
components avoiding hot spots. As an example, selenium
rectifiers should be placed in a vertical position in an
"open" section of the box so that they maarproperly convection
cool. Centers of high heat disiipation should be evally
spaced so as to provide for better heat equilibrium and avoid
very hot areas.
d. Installation of the electronic equipment should provide
for a degree of cooling necessary to avoid breakdown of the
equipment. Theoretical and practical studies are being planned
to develop techniques that will help in the cooling of concealed
electronic equipment.
One outstanding case of beat failure of electronic
equipment has been recorded. This involved using a resistor
to drop the power to a confined wall transmitter from 220V
to by. The resistor failed after a few hours of operation.
A variation of the beat failure problem is the poor
security that results from a concealed hot transmitter or
other electronic gear. The heat emitted from the wall may
be felt directly or:may have effects Which, over a period of
time, will betray the location of the equipment. These effects
include discoloration of wall paper, paint, etc.
To alleviate this difficulty, more emphasis should be
placed on a. and b. in the design of the equipment.
4. In general, it appears that there is no overall cure-all
for the problem of heat in electronic equipment. It does appear
however that by diligent application of the above listed techniques
the problem can be handled satisfactorily
Distribution:
P-134
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Declassified in Part - Sanitized Copy Approved for Release 2013/11/21: CIA-RDP78-03153A00-1900040001.-9
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