Avionics Cooling primer...

[quizzical1]

Hi All,

Can anyone suggest the best place(s) online to learn passive (radiant) vs active (liquid) cooling and possibly theory / equations for determining when to use one vs the other?

TIA

Q~

 

[3DDave]

Care to narrow that down? Spacecraft, Aircraft, Missiles? Cooling what part of the system?

 

[WKTaylor]

These might help...

ARINC 728* AVIONICS REFRIGERATION COOLING SYSTEM (ARCS)

SAE
AIR64 ELECTRICAL AND ELECTRONIC EQUIPMENT COOLING IN COMMERCIAL TRANSPORTS
AIR1277 COOLING OF MILITARY AVIONIC EQUIPMENT
AIR1811 LIQUID COOLING SYSTEMS
AIR1957 HEAT SINKS FOR AIRBORNE VEHICLES
AIR5744 AIRCRAFT THERMAL MANAGEMENT SYSTEM ENGINEERING
ARP85 AIR CONDITIONING SYSTEMS FOR SUBSONIC AIRPLANES
ARP89 AIRCRAFT COMPARTMENT AUTOMATIC TEMPERATURE CONTROL SYSTEMS
ARP147 ENVIRONMENTAL CONTROL SYSTEMS TERMINOLOGY
ARP217 TESTING OF AIRPLANE INSTALLED ENVIRONMENTAL CONTROL SYSTEMS (ECS)
ARP292 ENVIRONMENTAL CONTROL SYSTEMS FOR HELICOPTERS
ARP987 THE CONTROL OF EXCESS HUMIDITY IN AVIONICS COOLING
PT-46 VEHICLE THERMAL MANAGEMENT
PT-167 THERMAL MANAGEMENT IN AUTOMOTIVE APPLICATIONS
PT-177 AIRCRAFT THERMAL MANAGEMENT: SYSTEMS ARCHITECTURES
PT-178 AIRCRAFT THERMAL MANAGEMENT: INTEGRATED ENERGY SYSTEMS ANALYSIS
SAE/TP 2010-01-1812 INTEGRATED ELECTRICAL AND THERMAL MANAGEMENT SUB-SYSTEM OPTIMIZATION


Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[quizzical1]

Thanks, WKTaylor!

3DDave - electronics cooling for aircraft and spacecraft. Is there any info that can help determine when to use passive vs liquid cooling?

 

[IRstuff]

The determination is based on requirements and the environment. For example, spacecraft use passive, radiative, cooling, period, because they can't get heat out any other way. Aircraft can make use of convection and radiation, but need to be wary of thermal signature.

Liquid cooling does not apply at the interface of either with its environment, although liquid cooling, or heat pipes, could move heat around within the craft.

I don't get where you might think liquid cooling might be used otherwise.

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[rb1957]

we done two projects where we've used coolant and (external) radiators ... just like old liquid cooled engines.

As helpful as Will's links are certain to be in giving you information about cooling, I doubt they answer your question (as I read it) ... "when should I use passive cooling as opposed to liquid cooling ?".

First, aircraft and spacecraft are two very different things. Spacecraft are, for the most part, swimming in a huge heat sink; often the question is "how do we stay hot ?". Admittedly there are also environments (like the Shuttle bay, or other things in low earth orbit) that go from +100degC to -100degC and back every 90 minutes. Airplanes are obviously very different. So please don't say "electronics cooling for aircraft and spacecraft" ... unless you're after design approaches for those two different situations. In which case, I'd ask ... "is this for work ?"

another day in paradise, or is paradise one day closer ?

 

[Sparweb]

Spacecraft are, for the most part, swimming in a huge heat sink; often the question is "how do we stay hot ?"

Nitpick: Zero convective or conductive cooling possible with the external environment means that managing heat is difficult in BOTH ways. The sun facing side can get very hot, depending on its black-body emissivity/absorptivity. Vice-versa for the side facing away getting very cold, and the thermal expansion can be a stress condition. Since many satellites are designed to interact with the Earth, and parked in LEO, they get a 90-minute rotation cycle "on the rotisserie" that they must endure. Sats in GEO get the cycle once a day.

SpaceX made all of those Starlinks shiny on purpose.

http://www.sparweb.ca

 

[rb1957]

thx for "man-splaining" that, Steve ... (smile).

also another reason why satellites are spin stabilised.

another day in paradise, or is paradise one day closer ?

 

[IRstuff]

satellites are spin stabilised.

In what sense? All the earth observation satellites that I've looked at are nadir pointing, and therefore do a single 360 spin per orbit, over 90-ish minutes, but they don't move otherwise, unless for station keeping.

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[rb1957]

many satellites are/were spin stabilised instead of 3 axis thrusters ... which could be "station keeping".

I can remember seeing satellites being spun up in the shuttle bay prior to launch.

it's also a nice place to put your solar cells ... on the side of your cylindrical satellite.

another day in paradise, or is paradise one day closer ?

 

[IRstuff]

That might have just been for getting off the shuttle. Any satellite with any EM source/receiver would not be spin stabilized; antennas would get a useful duty cycle of something like 10%, and any sensing satellite would be fubar. Landsat8, for example, continually observes the Earth over 80% of of its orbit and cannot maintain its georeferencing if it were spinning at all.

Every satellite that has any hope of georeferencing uses one or more star trackers, which typically only have 10-Hz frame rates and don't tolerate more than 0.1 deg/s rotation rates if they are to maintain their stated measurement accuracies.

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[rb1957]

spin stabilized was mainly used in early satellites. modern designs tend to 3 axis thrusters.

actually earth pointing (antennas, sensors) is easy in a spin stabilised satellite, with a stationary central core or earth-side face.

another day in paradise, or is paradise one day closer ?

 

[IRstuff]

Not a question of easy, but imaging satellites do not spin, since the image rotation would be a pain and would result in serious degradation of image quality. All extant Landsat satellites are push-broom imagers, which would result in gibberish if they were spun at all.

<edit>
Looks like spin stabilization is a peculiarity unique to RF satellites, and I would guess, only a small subset. Skylink satellites are RF only, but not spin-stabilized, since they're like pizza boxes. If they were to spin, that would drive astronomers even more over the edge than they are now, since the satellite reflections would wind up blinking, when viewed from a specific spot on Earth.

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