heat goes down

[WA1GFZ]

as most know heat rises. I was looking at a new transceiver that will sell for $1600 and see the heat sink fins face down. It set off my POS detector

[KX5JT]

Maybe it was designed in the south of the equator so the heat can.. hmm... nevermind.

[Rob K2CU]

HI Frank!

Apparently the designers took "heat Sink" literally.

[Tom WA3KLR]

Frank,

Get with Obama's program of change.

[WB2YGF]

as most know heat rises. I was looking at a new transceiver that will sell for $1600 and see the heat sink fins face down. It set off my POS detector

If forced air cooling is employed, I don't think it matters as much.

[ka3zlr]

As far as New SSB PHONE/CW MFG'd, that even grabs my interest is the New Elecraft, of course I like alot of what those guys are doing, Second wud be Ten-Tec..

[KA1ZGC]

as most know heat rises.

No, it doesn't.

Hot air rises over cold air. Hot water rises over cold water. The molecular density of a substance is inversely proportional to its temperature, with the exception of ice. Heat itself doesn't rise, hot matter rises over cold matter. Heat itself merely radiates and disperses.

Heat as a form of energy has no concept of gravity. A heat sink with the fins pointed down still draws heat away from the device in question. That's all it needs to do.

[k4kyv]

Actually, "heat" doesn't radiate.  What radiates is infra-red light.  Heat is the effect the radiation has on matter that absorbs the light's energy.  The warmth we feel from the sun is not from "heat" directly radiated from the sun.  Most of it is from the visible light that falls on our skin, or on whatever we perceive as "hot". The light that is not reflected off the surface gives up its energy to the matter that absorbs it, and raises its temperature.

"Radiant heat" or infra-red given off by a heater is exactly the same thing as the visible light given off by a lamp, and has exactly the same effect on temperature of surrounding objects, except that it is invisible to the eye.

Hot air given off by a heated object such as cooling fans on a tube is air in which the temperature has risen due to energy absorbed from the infra-red and visible light emitted by the tube.  Because of its higher temperature, the air feels warm because it, too is now releasing energy, until it reaches the ambient temperature of its surroundings.

[KA1ZGC]

Actually, "heat" doesn't radiate.  What radiates is infra-red light. 

Yep... fair enough.

[N3DRB The Derb]

how cum you guys no so much?   

never ceases to amaze me the amount of knowledge in the brains inside the heads;
on top of teh necks that sit on the shoulders of the people here.

[KA1ZGC]

how cum you guys no so much?   

(Jumps up, raises hand) Ooh! Ooh! I know this one! I know this one!

Because I payed attention when they taught me this stuff in my 5th grade science class.

Can I be excused now? My pimp's here.

[Pete, WA2CWA]

Dog in heat
Packing heat
Police
Throwing some heat
Heat of the night
Final heat
Dead heat

[KA1ZGC]

Dog in heat
Packing heat
Police
Throwing some heat
Heat of the night
Final heat
Dead heat

That's the worst haiku I've ever read.

[WB2YGF]

haiku ?

[Pete, WA2CWA]

haiku ?

Haiku is a poetic form and a type of poetry from the Japanese culture. Haiku combines form, content, and language in a meaningful, yet compact form. Haiku poets write about everyday things. Many themes include nature, feelings, or experiences. Usually they use simple words and grammar. The most common form for Haiku is three short lines. The first line usually contains five (5) syllables, the second line seven (7) syllables, and the third line contains five (5) syllables. Haiku doesn't rhyme. A Haiku must "paint" a mental image in the reader's mind. This is the challenge of Haiku - to put the poem's meaning and imagery in the reader's mind in ONLY 17 syllables over just three (3) lines of poetry!

[W1JS]

This is clearly a hot topic, promoting a heated discussion.

[KA1ZGC]

Well, as long as we're being technically correct (this is the technical forum, after all) and clarifying just about everything under the sun, Pete's description more accurately depicts Senryu.

Having said that, Haiku is merely Senryu which contains a seasonal reference.

For example, Haiku:

Autumn leaves descend
onto Irwin Richardt's grave
then yelp "Okay FINE!"

...with the requisite seasonal reference appearing in the first line.

Senryu, on the other hand, is the same format without a seasonal reference:

Joseph Coors is dead.
Rot in Hell you nazi prick,
your beer tastes like piss*

Minus that one tiny (and seldom asserted) detail, Pete's description was quite accurate, eloquent, and very well-written.

Spend a few decades in talk.bizarre and you'll feel inclined to point out the difference, too. Knowing the difference was sort of a rite of passage.

Right... as you were, Gentlemen!

--Thom
*This Senryu was originally posted to talk.bizarre when Joe Coors finally died. I honestly don't remember who posted it, only laughing my ass off when I read it. Those of you offended by it would do well to look into how the man spent his spare time.

[WA1GFZ]

Fins down are almost as useless as horizontal fins

[KD3CN]

-warning- this is boring talk about heat transfer.

Heat sinks predominantly use two of the heat transfer types, conduction and convection.  Heat is directly conducted into the aluminum heat sink through physical contact with the device.  Aluminum has a very good coefficient for conductive heat transfer (a low resistance), so heat is effectively transferred from the device into the solid aluminum heat sink.  Conductive heat transfer from the aluminum to the air surrounding it is very poor, due to the poor heat conduction coefficient of air (think of a series circuit, a low resistance to heat conduction thru the aluminum heat sink, and a high resistance in the air surrounding it).  However, convective heat transfer occurs when the air in contact with the aluminum is warmed, and then moved away (and replaced) by colder air due to either forced air circulation or the normal circulation(rising) of warm air.  Convective heat transfer depends on the mixing of the air in contact with the surface.   The air in contact with the surface of the aluminum is heated, absorbing its heat, and is continuously replaced by colder air.  This convective heat transfer is not as effective as conduction, and that’s why there are fins on heat sinks, because more surface area is required to transfer the heat.  The upward flow of air that occurs when air is heated increases the convective heat transfer from the fins of a heat sink, and that’s why heat sinks work better with vertical fins vs. horizontal.
A warm heat sink certainly looses heat via radiation, but that is very minimal compared to the heat transfer described above.

Frank is right, upside-down heat sinks don’t make sense, because you want the best air flow possible, and with no fan the only force is that of rising warm air.

73, Karl

[KB3DKS]

as most know heat rises. I was looking at a new transceiver that will sell for $1600 and see the heat sink fins face down. It set off my POS detector

  Maybe the idea was having an easy way to mount the, at extra cost of course,  'optional' fan after the naive user overheated the rig when running AM into a high SWR.

Bill, KB3DKS in 1 Land

[WA1GFZ]

I don't see how cost is an issue

[Ed/KB1HYS]

Mebbe twas the only way it'd fit into the chassis? 

I have noticed in the past that some very good electrical engineers don't know a lot about the mechanical side of the house...  though they may think differently.

Or its just, build-it-fast, build-it-cheap, sell-a-lot, then go-out-of-business-business plan 

[WA1GFZ]

How could it not fit in a chassis if everything is flipped fins up.
Actually vertical fins gives the best heat transfer. Fins up is second best for moving heat. Fins up does tend to make all the components the same temperature so good when you have a number of devices in parallel. Trapped air flow hurts efficiency.  I guess during space travel it doesn't matter.

[KD3CN]

Perhaps this is when hot air doesn't rise and convectively remove heat!

I guess during space travel it doesn't matter.

[KA1ZGC]

How could it not fit in a chassis if everything is flipped fins up.
Actually vertical fins gives the best heat transfer. Fins up is second best for moving heat. Fins up does tend to make all the components the same temperature so good when you have a number of devices in parallel. Trapped air flow hurts efficiency.  I guess during space travel it doesn't matter.

Sure, but the fins themselves are still vertical. They're just on the bottom of the unit instead of the back.

The convective airflow that a heatsink needs still happens. It's not as effective as vertical fins protruding from the rear of the unit, but it still happens. The heat sink doesn't stop being a heat sink just because it's on the bottom of the unit. If it's sufficiently overbuilt, it shouldn't be a problem.

In fact, you've got far more surface area on the bottom of any radio than you have on the back, unless the fins on the back are themselves the same length as the chassis (certain Motorola radios come to mind). Surface area is the key to heat transfer, that's the whole idea behind having the fins.

So now I wonder what the surface area comparison would be between the heatsink they're using (a pic or link would sure come in handy right about now) and a heatsink mounted on the rear of the unit? How large would a rear-mounted heatsink have to be to have the same surface area as the heatsink they're using?