In high school physics, the three methods of heat dispersal were
presented as conduction, radiation, and convection?

Is that all there is? Is diffusion a fourth or is it subsumed by
convection?

I could be wrong but:
Conduction seems to be limited to within a solid, or from the surface
of a solid to that part of a liquid or gas in contact with the solid.

ICBWB:
Convection seems to be limited to liquids and gases.

And ICBWB: radiation seems to be limited to from a solid or maybe a
liquid through a gas to another solid or maybe a liquid.

As to convection, it was always described and seems to be limited to
broad currents, such as hot air rising and cold air sinking, but is
that all that happens? In, say, a room with moderate cooling in the
summer or moderate heating in the winter, while in general the hot air
rises, doesn't the random motion of some of the hot air cause it to go
downward and to mix with the cooler air below it? Is this radiation?
Is it still convection? Or is it diffusion and for reasons of
definition, not one of the other three?

In article , mm writes:
In high school physics, the three methods of heat dispersal were
presented as conduction, radiation, and convection?

Is that all there is? Is diffusion a fourth or is it subsumed by
convection?

Diffusion is conduction.

I could be wrong but:
Conduction seems to be limited to within a solid, or from the surface
of a solid to that part of a liquid or gas in contact with the solid.

No, conduction is present in liquids and gases as well, though it is
dominated by convection for significant temperature gradients (and in
the presence of gravity).

ICBWB:
Convection seems to be limited to liquids and gases.

That much is certainly true.

And ICBWB: radiation seems to be limited to from a solid or maybe a
liquid through a gas to another solid or maybe a liquid.

In principle radiation can be present within liquid or solid as well.
In practice, under normal circumstances, its range is so limited there
that it is indistinguishable from conduction.

As to convection, it was always described and seems to be limited to
broad currents, such as hot air rising and cold air sinking, but is
that all that happens? In, say, a room with moderate cooling in the
summer or moderate heating in the winter, while in general the hot air
rises, doesn't the random motion of some of the hot air cause it to go
downward and to mix with the cooler air below it? Is this radiation?
Is it still convection? Or is it diffusion and for reasons of
definition, not one of the other three?

Collective motion of masses of air is convection, random motion of
individual molecules is conduction.

Mati Meron | "When you argue with a fool,
| chances are he is doing just the same"

"mm" wrote in message .
In high school physics, the three methods of heat dispersal were
presented as conduction, radiation, and convection?

Is that all there is? Is diffusion a fourth or is it subsumed by
convection?

Transporter beam in a pinch or properly used, a Deflector Dish.
http://www.ccdump.org/deflectordish.html

HTH,
-zero

In article ,
says...
In high school physics, the three methods of heat dispersal were
presented as conduction, radiation, and convection?

Is that all there is? Is diffusion a fourth or is it subsumed by
convection?

I'd say conduction, rather then convection. Heat is transfered by
the molecules bouncing off each other = conduction.

I could be wrong but:
Conduction seems to be limited to within a solid, or from the surface
of a solid to that part of a liquid or gas in contact with the solid.

No, liquids and gases also conduct. Convection may be dominant
though.

ICBWB:
Convection seems to be limited to liquids and gases.

Sure, something's gotta move for convection. Solids don't move too
well. ;-)

And ICBWB: radiation seems to be limited to from a solid or maybe a
liquid through a gas to another solid or maybe a liquid.

No, radiation occurs with all substances but at moderate
temperatures can be dwarfed by conduction and convection. We see
Jupiter (a "gas giant") by radiation, for instance.

As to convection, it was always described and seems to be limited to
broad currents, such as hot air rising and cold air sinking, but is
that all that happens? In, say, a room with moderate cooling in the
summer or moderate heating in the winter, while in general the hot air
rises, doesn't the random motion of some of the hot air cause it to go
downward and to mix with the cooler air below it? Is this radiation?

Some by radiation, some by conduction, mostly convection though.

Is it still convection? Or is it diffusion and for reasons of
definition, not one of the other three?

Diffusion normally relates to different gases/liquids. If they're
the same I'm not sure how you track the molecules. They'll swap
heat by bumping into each other (conduction).

--
Keith

mm wrote:
In high school physics, the three methods of heat dispersal were
presented as conduction, radiation, and convection?

Is that all there is?

That's about it. At least that's what's still being taught at all
levels, these days.

Is diffusion a fourth or is it subsumed by
convection?

Depends what you actually mean by diffusion. If you're talking about
the ability of a gas to spread out to fill it's container, then yes,
you're talking convection.

I could be wrong but:
Conduction seems to be limited to within a solid, or from the surface
of a solid to that part of a liquid or gas in contact with the solid.

Conduction can occur in any medium. Remember it's just the direct
transfer of heat energy through the media.

ICBWB:
Convection seems to be limited to liquids and gases.

In normal, everyday situations, yes. But geologists talk about
convection in rock in the earth's mantle, albeit very hot rock, but
still technically a solid at the pressures considered.


And ICBWB: radiation seems to be limited to from a solid or maybe a
liquid through a gas to another solid or maybe a liquid.

Well, radiation can be generated in any medium and absorbed by any
medium, regardless of state.

As to convection, it was always described and seems to be limited to
broad currents, such as hot air rising and cold air sinking, but is
that all that happens?

Basically. Convection is the transfer of heat by a moving medium, such
as air.

In, say, a room with moderate cooling in the
summer or moderate heating in the winter, while in general the hot air
rises, doesn't the random motion of some of the hot air cause it to go
downward and to mix with the cooler air below it?

Statistically yes, but on average, warm air will rise and cooler air
will fall. It is thermodynamically possible for the very opposite to
occur, but the probability of that happening is astronomically small.

Is this radiation?

Radiation is light, UV, IR, etc.

Is it still convection?

In your above example, it is practically all convection, since the air
is moving and carrying the heat with it. There could also be some
conduction occuring, as energy is directly transferred through the air
between hot and cold regions,.and perhaps some radiation if sunlight is
shining through a window or there is a light turned on.

Time travel, too. You could go back to before the heat.

For adding heat, don't forget laser beams, microwaves, and spontaneous
combustion :-))




zero wrote:
"mm" wrote in message .
In high school physics, the three methods of heat dispersal were
presented as conduction, radiation, and convection?

Is that all there is? Is diffusion a fourth or is it subsumed by
convection?

Transporter beam in a pinch or properly used, a Deflector Dish.
http://www.ccdump.org/deflectordish.html

HTH,
-zero

mm wrote:
In high school physics, the three methods of heat dispersal were
presented as conduction, radiation, and convection?

Is that all there is? Is diffusion a fourth or is it subsumed by
convection?

That's a tricky question to answer. Partly, I don't understand what you
mean by 'dispersal'. In any case, heat can be transported by material
particles or by nonmaterial processes. That is, energy (heat) can be
convected by the motion of hot particles flowing into colder regions,
transported by infrared radiation, or transported by nonmaterial
diffusion (conduction). Hot particles diffusing into colder regions is
not typically found here on Earth due to bouyancy- hot stuff is less
dense and so there is a bouyancy-driven flow of material which convects
the heat.

I could be wrong but:
Conduction seems to be limited to within a solid, or from the surface
of a solid to that part of a liquid or gas in contact with the solid.

Only when bouyancy effects dominate. In space, for example, conduction
occurs in liquids and gases as well. Or if the liquid is of high
viscosity (if the Nusselt number is small). Thermal greases will
conduct heat rather than convect heat. There's also the Grashof number
and Peclet number. If these numbers are large or small, a particular
heat transfer mechanism occurs. For example, if the Grashof number is
large, there will be large bouyancy effects. If the Grashof number is
small, viscous effects dominate and the thermal energy will instead
diffuse.


ICBWB:
Convection seems to be limited to liquids and gases.

Yes, usually. Again, take away gravity and convection doesn't really
occur. There still are some effects like Marangoni flow (surface
tension-driven convection) that occur. It's an open question for
granular media, IIRC.


And ICBWB: radiation seems to be limited to from a solid or maybe a
liquid through a gas to another solid or maybe a liquid.

There's a difference between thermal radiation and radiative heat
transfer. You seem to be thinking about heat transfer here, not thermal
transport.

snip

--
Andrew Resnick, Ph.D.
Department of Physiology and Biophysics
Case Western Reserve University

mm wrote:

In high school physics, the three methods of heat dispersal were
presented as conduction, radiation, and convection?

Is that all there is? Is diffusion a fourth or is it subsumed by
convection?

It's a part of conduction. Some people also add "phase change" as
a method of heat transfer, eg evaporation from lower soil layers
and condensation above.

As to convection, it was always described and seems to be limited to
broad currents, such as hot air rising and cold air sinking, but is
that all that happens? In, say, a room with moderate cooling in the
summer or moderate heating in the winter, while in general the hot air
rises, doesn't the random motion of some of the hot air cause it to go
downward and to mix with the cooler air below it?

Not much. Then again, room air may fall near an outside wall, slide
across the floor, rise up near an inside wall, then slide across
the ceiling to make a loop.

Is this radiation?

No, but that can also be important. Surfaces with mean absolute temp T (R)
and emissivity 1 have a linearized radiation conductance 4x0.1714x10^8xT^3
Btu/h-F-ft^2, eg U1 (R1) for T = 400 + 70 (F.) = 530 R.

Nick

mm wrote:
In high school physics, the three methods of heat dispersal were
presented as conduction, radiation, and convection?

Is that all there is? Is diffusion a fourth or is it subsumed by
convection?

Ah, you have forgotten the frequently seen fourth form, which is
wrapping the hot thing up in a towel and running with it over to
somewhere else where you drop it off. It can move a lot of heat very
effectively.


I could be wrong but:
Conduction seems to be limited to within a solid, or from the surface
of a solid to that part of a liquid or gas in contact with the solid.

ICBWB:
Convection seems to be limited to liquids and gases.

And ICBWB: radiation seems to be limited to from a solid or maybe a
liquid through a gas to another solid or maybe a liquid.

As to convection, it was always described and seems to be limited to
broad currents, such as hot air rising and cold air sinking, but is
that all that happens? In, say, a room with moderate cooling in the
summer or moderate heating in the winter, while in general the hot air
rises, doesn't the random motion of some of the hot air cause it to go
downward and to mix with the cooler air below it? Is this radiation?
Is it still convection? Or is it diffusion and for reasons of
definition, not one of the other three?

Keith Williams wrote:
In article ,
says...
In high school physics, the three methods of heat dispersal were
presented as conduction, radiation, and convection?

Is that all there is? Is diffusion a fourth or is it subsumed by
convection?

I'd say conduction, rather then convection. Heat is transfered by
the molecules bouncing off each other = conduction.

depends what's diffusing. If it's just the heat, that's conduction. if
it's hot molecules diffusing, that's convection.


I could be wrong but:
Conduction seems to be limited to within a solid, or from the surface
of a solid to that part of a liquid or gas in contact with the solid.

No, liquids and gases also conduct. Convection may be dominant
though.

ICBWB:
Convection seems to be limited to liquids and gases.

Sure, something's gotta move for convection. Solids don't move too
well. ;-)

And ICBWB: radiation seems to be limited to from a solid or maybe a
liquid through a gas to another solid or maybe a liquid.

No, radiation occurs with all substances but at moderate
temperatures can be dwarfed by conduction and convection. We see
Jupiter (a "gas giant") by radiation, for instance.

As to convection, it was always described and seems to be limited to
broad currents, such as hot air rising and cold air sinking, but is
that all that happens? In, say, a room with moderate cooling in the
summer or moderate heating in the winter, while in general the hot air
rises, doesn't the random motion of some of the hot air cause it to go
downward and to mix with the cooler air below it? Is this radiation?

Some by radiation, some by conduction, mostly convection though.

Is it still convection? Or is it diffusion and for reasons of
definition, not one of the other three?

Diffusion normally relates to different gases/liquids. If they're
the same I'm not sure how you track the molecules. They'll swap
heat by bumping into each other (conduction).

--
Keith

Andy Resnick writes:

There's a difference between thermal radiation and radiative heat
transfer.

"Thermal" radiation? What's that?

Richard J Kinch wrote:
Andy Resnick writes:


There's a difference between thermal radiation and radiative heat
transfer.


"Thermal" radiation? What's that?

As commonly used, "thermal radiation" means radiation in the waveband
from about 3 microns to about 20 microns, and represents the peak
wavelength of blackbody radiation for most objects of interest- of
interest to those using the term "thermal radiation".

As a general concept, the electromangtic field carries energy at all
wavelengths.

--
Andrew Resnick, Ph.D.
Department of Physiology and Biophysics
Case Western Reserve University

Ah, you have forgotten the frequently seen fourth form, which is
wrapping the hot thing up in a towel and running with it over to
somewhere else where you drop it off. It can move a lot of heat very
effectively.

Isn't that convection?

Conduction: transfer of heat from one molecule to its neighbor by means
of thermal collisions.

Convection: transfer of heat from one location to another as kinetic
energy of a group of molecules of a fluid. (usually driven by the
effects of gravity on differential densities as in the Archimedes
effect)

Diffustion: *also* transfer of heat from one location to another as
kinetic energy of a group of molecules of a fluid. Distinguished from
convection in that the random thermal motion of the molecules provides
the transport.

Radiation: transfer of heat from location to another by means of
electromagnetic radiation. No medium is required as radiation can
traverse a total vacuum. [The sun sure is hot today, isn't it?] If a
medium is present it must be at least partially transparent to the
particular wavelengths of radiation involved.

Heat can also be transported by converting it to another form
(typically electrical or chemical energy) top be placed within a
material, which itself is transported (or in the case of electricity is
electrically conducted) to another location where the heat can be
released.

HTH

Tom Davidson
Richmond, VA

Andy Resnick writes:

As a general concept, the electromangtic field carries energy at all
wavelengths.

OK, it sounded like you were advocating some 19th century notion of radiant
heat.

"mm" wrote in message
...
In high school physics, the three methods of heat dispersal were
presented as conduction, radiation, and convection?

Is that all there is? Is diffusion a fourth or is it subsumed by
convection?

How about some of the tricks used to achieve near absolute zero
temperatures. I recall they are quite exotic and involve lasers and optical
cavities and the like - but perhaps they all amount to conduction or
radaition?

I could be wrong but:
Conduction seems to be limited to within a solid, or from the surface
of a solid to that part of a liquid or gas in contact with the solid.
CY: I'd think that conduction is possible within gasses,b ut much less
so. Cause they would be more likely to convect.


ICBWB:
Convection seems to be limited to liquids and gases.
CY: Well, if you wanted to be a smartass, you could mention a
semiliquid like sand. But that's not really fair.


And ICBWB: radiation seems to be limited to from a solid or maybe a
liquid through a gas to another solid or maybe a liquid.
CY: Sounds about right. Of course, radiation from the sun is supposed
to be a superhot ball of gas (plasma??)

As to convection, it was always described and seems to be limited to
broad currents, such as hot air rising and cold air sinking, but is
that all that happens? In, say, a room with moderate cooling in the
summer or moderate heating in the winter, while in general the hot air
rises, doesn't the random motion of some of the hot air cause it to go
downward and to mix with the cooler air below it?
CY: yes, that would happen. Some air currents push hot air down.

Is this radiation?
CY: No.

Is it still convection?
CY: Pushing hot air down is still convection.

Or is it diffusion and for reasons of
definition, not one of the other three?
CY: Only three ways I know to transfer heat.

Yes, convection stands there with her high heels, black leather and
whip. She says to the conduction which is tied to the bed.....

Know what you mean, though. Since fluids vary in density with temp,
that convection would be more a factor.

--

Christopher A. Young
You can't shout down a troll.
You have to starve them.
..

"Keith Williams" wrote in message
T...

I could be wrong but:
Conduction seems to be limited to within a solid, or from the
surface
of a solid to that part of a liquid or gas in contact with the
solid.

No, liquids and gases also conduct. Convection may be dominant
though.

In article .com,
says...

Keith Williams wrote:
In article ,
says...
In high school physics, the three methods of heat dispersal were
presented as conduction, radiation, and convection?

Is that all there is? Is diffusion a fourth or is it subsumed by
convection?

I'd say conduction, rather then convection. Heat is transfered by
the molecules bouncing off each other = conduction.

depends what's diffusing. If it's just the heat, that's conduction. if
it's hot molecules diffusing, that's convection.

I disagree. How do you track which molecule is which? Convection
would only allow hotter molecules to rise (and colder sink).
Diffusion would allow the reverse too. As such, diffusion may be a
fourth mechanism but it's not likely to be significant as the
molecules transfer heat by conduction to each other.

--
Keith

"Stormin Mormon" wrote in message
...
I could be wrong but:
Conduction seems to be limited to within a solid, or from the surface
of a solid to that part of a liquid or gas in contact with the solid.
CY: I'd think that conduction is possible within gasses,b ut much less
so. Cause they would be more likely to convect.

Take a look at sealed double glazing.... The gap between the panes is
choosen so that it's as large as possible (to mimimise conduction losses)
but not so big that it allows convection losses.

It's worth noting that convection is only an issue because conduction occurs
between the gas and glass. If there was no such conduction it wouldn't
matter if the gas had convective flow.

mm wrote:

In high school physics, the three methods of heat dispersal were
presented as conduction, radiation, and convection?

Is that all there is? Is diffusion a fourth or is it subsumed by
convection?

http://en.wikipedia.org/wiki/Heat#Heat_transfer_mechanisms

wrote:
Ah, you have forgotten the frequently seen fourth form, which is
wrapping the hot thing up in a towel and running with it over to
somewhere else where you drop it off. It can move a lot of heat very
effectively.

Isn't that convection?

Twice arrested, never convected.

z wrote:

Ah, you have forgotten the frequently seen fourth form, which is
wrapping the hot thing up in a towel and running with it over to
somewhere else where you drop it off. It can move a lot of heat very
effectively.

Very good! That's non-convective mixing or mass-transport (to give it
some important sounding names).

Edward Green wrote:
z wrote:

Ah, you have forgotten the frequently seen fourth form, which is
wrapping the hot thing up in a towel and running with it over to
somewhere else where you drop it off. It can move a lot of heat very
effectively.

Very good! That's non-convective mixing or mass-transport (to give it
some important sounding names).

Now that you mention it, it is, isn't it? (beam)

Edward Green wrote:
z wrote:

Ah, you have forgotten the frequently seen fourth form, which is
wrapping the hot thing up in a towel and running with it over to
somewhere else where you drop it off. It can move a lot of heat very
effectively.

Very good! That's non-convective mixing or mass-transport (to give it
some important sounding names).

Actually, reminds me of the early days of networking, when one of the
fastest protocols was still sneakernet. I.e., copy a floppy full and
run it over to the other machine, thereby transferring 1.4 meg
relatively quickly.

z wrote:
Edward Green wrote:
z wrote:

Ah, you have forgotten the frequently seen fourth form, which is
wrapping the hot thing up in a towel and running with it over to
somewhere else where you drop it off. It can move a lot of heat very
effectively.

Very good! That's non-convective mixing or mass-transport (to give it
some important sounding names).

Actually, reminds me of the early days of networking, when one of the
fastest protocols was still sneakernet. I.e., copy a floppy full and
run it over to the other machine, thereby transferring 1.4 meg
relatively quickly.

Yes. And what do you mean 'early days'?

I am working for a very large company where, in my area, there are
still two non-communicating networks, and occasionally data is
transferred by sneaker net. Of course, this is going to be fixed any
day now...

On Thu, 17 Aug 2006 12:43:58 -0400, Keith Williams
wrote:


As to convection, it was always described and seems to be limited to
broad currents, such as hot air rising and cold air sinking, but is
that all that happens? In, say, a room with moderate cooling in the
summer or moderate heating in the winter, while in general the hot air
rises, doesn't the random motion of some of the hot air cause it to go
downward and to mix with the cooler air below it? Is this radiation?

Some by radiation, some by conduction, mostly convection though.

Is it still convection? Or is it diffusion and for reasons of
definition, not one of the other three?

Diffusion normally relates to different gases/liquids. If they're
the same I'm not sure how you track the molecules.

Can't they tie little transmitters to them, like they do with wild
animals?

I guess not.

They'll swap
heat by bumping into each other (conduction).

I guessed radiation and convection and you and most of you said it's
conduction, the only one I iddn't guess. Oh, well.

Thanks to you and everyone (except the trekkies )

I didn't answer right away because I read alt.home.repair and it has
so much traffic, I missed the whole thread for 2 days (until I
remembered to go looking for it.)

--
Keith

In article .com,
"Edward Green" wrote:
z wrote:
Edward Green wrote:
z wrote:

Ah, you have forgotten the frequently seen fourth form, which is
wrapping the hot thing up in a towel and running with it over to
somewhere else where you drop it off. It can move a lot of heat very
effectively.

Very good! That's non-convective mixing or mass-transport (to give it
some important sounding names).

Actually, reminds me of the early days of networking, when one of the
fastest protocols was still sneakernet. I.e., copy a floppy full and
run it over to the other machine, thereby transferring 1.4 meg
relatively quickly.

Yes. And what do you mean 'early days'?

Not very early. Tranferring bits on a _floppy_ is like
moving the Atlantic Ocean into the Pacific with a teaspoon.


I am working for a very large company where, in my area, there are
still two non-communicating networks, and occasionally data is
transferred by sneaker net. Of course, this is going to be fixed any
day now...

These days, with those cigarette lighters, it's not too difficult.
You don't need three muscled males, a skid, and 10000 magtapes to
do it.

/BAH

wrote:

Not very early. Tranferring bits on a _floppy_ is like
moving the Atlantic Ocean into the Pacific with a teaspoon.

Sometimes all you need to move is a cup.

In article ,
says...
In article .com,
"Edward Green" wrote:
z wrote:
Edward Green wrote:
z wrote:

Ah, you have forgotten the frequently seen fourth form, which is
wrapping the hot thing up in a towel and running with it over to
somewhere else where you drop it off. It can move a lot of heat very
effectively.

Very good! That's non-convective mixing or mass-transport (to give it
some important sounding names).

Actually, reminds me of the early days of networking, when one of the
fastest protocols was still sneakernet. I.e., copy a floppy full and
run it over to the other machine, thereby transferring 1.4 meg
relatively quickly.

Yes. And what do you mean 'early days'?

Not very early. Tranferring bits on a _floppy_ is like
moving the Atlantic Ocean into the Pacific with a teaspoon.


I am working for a very large company where, in my area, there are
still two non-communicating networks, and occasionally data is
transferred by sneaker net. Of course, this is going to be fixed any
day now...

These days, with those cigarette lighters, it's not too difficult.
You don't need three muscled males, a skid, and 10000 magtapes to
do it.

Think about the bandwidth of a 747 full of magtapes! ;-)

--
Keith

On Sun, 20 Aug 2006 11:33:38 -0400, krw wrote:

Think about the bandwidth of a 747 full of magtapes! ;-)

AIUI, that is exactly the mechanism used to propagate usenet posts
across the Atlantic in the early days of Demon Internet.

--
Posted via a free Usenet account from http://www.teranews.com

In article ,
krw wrote:
In article ,
says...
In article .com,
"Edward Green" wrote:
z wrote:
Edward Green wrote:
z wrote:

Ah, you have forgotten the frequently seen fourth form, which is
wrapping the hot thing up in a towel and running with it over to
somewhere else where you drop it off. It can move a lot of heat very
effectively.

Very good! That's non-convective mixing or mass-transport (to give it
some important sounding names).

Actually, reminds me of the early days of networking, when one of the
fastest protocols was still sneakernet. I.e., copy a floppy full and
run it over to the other machine, thereby transferring 1.4 meg
relatively quickly.

Yes. And what do you mean 'early days'?

Not very early. Tranferring bits on a _floppy_ is like
moving the Atlantic Ocean into the Pacific with a teaspoon.


I am working for a very large company where, in my area, there are
still two non-communicating networks, and occasionally data is
transferred by sneaker net. Of course, this is going to be fixed any
day now...

These days, with those cigarette lighters, it's not too difficult.
You don't need three muscled males, a skid, and 10000 magtapes to
do it.

Think about the bandwidth of a 747 full of magtapes! ;-)

I can't. How long would it to cut those tapes? On our system
probably two years. On a system dedicated for tape copying...
a couple months?

I would certainly have to increase the number of muscled males.

/BAH

In article ,
Ben Newsam wrote:
On Sun, 20 Aug 2006 11:33:38 -0400, krw wrote:

Think about the bandwidth of a 747 full of magtapes! ;-)

AIUI, that is exactly the mechanism used to propagate usenet posts
across the Atlantic in the early days of Demon Internet.

Nah. It would take about 1 magtape to transport the bits.
There were only about hundred monkeys typing at newsgroups
while they were developing and testing to see which methods
worked best.

/BAH


/BAH

In article ,
krw wrote:
In article ,
says...
In article .com,
"Edward Green" wrote:
z wrote:
Edward Green wrote:
z wrote:

Ah, you have forgotten the frequently seen fourth form, which is
wrapping the hot thing up in a towel and running with it over to
somewhere else where you drop it off. It can move a lot of heat very
effectively.

Very good! That's non-convective mixing or mass-transport (to give it
some important sounding names).

Actually, reminds me of the early days of networking, when one of the
fastest protocols was still sneakernet. I.e., copy a floppy full and
run it over to the other machine, thereby transferring 1.4 meg
relatively quickly.

Yes. And what do you mean 'early days'?

Not very early. Tranferring bits on a _floppy_ is like
moving the Atlantic Ocean into the Pacific with a teaspoon.


I am working for a very large company where, in my area, there are
still two non-communicating networks, and occasionally data is
transferred by sneaker net. Of course, this is going to be fixed any
day now...

These days, with those cigarette lighters, it's not too difficult.
You don't need three muscled males, a skid, and 10000 magtapes to
do it.

Think about the bandwidth of a 747 full of magtapes! ;-)

Dagnurbbit. Now you've got me hooked. Is this the capacity
of one of those cigarette lighters? ...and people long
for the good ol' days; not me.

/BAH

In article ,
says...
In article ,
krw wrote:
In article ,
says...
In article .com,
"Edward Green" wrote:
z wrote:
Edward Green wrote:
z wrote:

Ah, you have forgotten the frequently seen fourth form, which is
wrapping the hot thing up in a towel and running with it over to
somewhere else where you drop it off. It can move a lot of heat very
effectively.

Very good! That's non-convective mixing or mass-transport (to give it
some important sounding names).

Actually, reminds me of the early days of networking, when one of the
fastest protocols was still sneakernet. I.e., copy a floppy full and
run it over to the other machine, thereby transferring 1.4 meg
relatively quickly.

Yes. And what do you mean 'early days'?

Not very early. Tranferring bits on a _floppy_ is like
moving the Atlantic Ocean into the Pacific with a teaspoon.


I am working for a very large company where, in my area, there are
still two non-communicating networks, and occasionally data is
transferred by sneaker net. Of course, this is going to be fixed any
day now...

These days, with those cigarette lighters, it's not too difficult.
You don't need three muscled males, a skid, and 10000 magtapes to
do it.

Think about the bandwidth of a 747 full of magtapes! ;-)

I can't. How long would it to cut those tapes? On our system
probably two years. On a system dedicated for tape copying...
a couple months?

More systems. Bandwidth is a matter of cost; it's latency that's
forever.


I would certainly have to increase the number of muscled males.

You would think of that. ;-)

--
Keith

On Mon, 21 Aug 06 09:11:39 GMT, wrote:

In article ,
Ben Newsam wrote:
On Sun, 20 Aug 2006 11:33:38 -0400, krw wrote:

Think about the bandwidth of a 747 full of magtapes! ;-)

AIUI, that is exactly the mechanism used to propagate usenet posts
across the Atlantic in the early days of Demon Internet.

Nah. It would take about 1 magtape to transport the bits.
There were only about hundred monkeys typing at newsgroups
while they were developing and testing to see which methods
worked best.

Er... yes. I sort of assumed that the 747 "full" was mere hyperbole
and ignored it!

--
Posted via a free Usenet account from http://www.teranews.com

In article ,
says...
In article ,
krw wrote:
In article ,
says...
In article .com,
"Edward Green" wrote:
z wrote:
Edward Green wrote:
z wrote:

Ah, you have forgotten the frequently seen fourth form, which is
wrapping the hot thing up in a towel and running with it over to
somewhere else where you drop it off. It can move a lot of heat very
effectively.

Very good! That's non-convective mixing or mass-transport (to give it
some important sounding names).

Actually, reminds me of the early days of networking, when one of the
fastest protocols was still sneakernet. I.e., copy a floppy full and
run it over to the other machine, thereby transferring 1.4 meg
relatively quickly.

Yes. And what do you mean 'early days'?

Not very early. Tranferring bits on a _floppy_ is like
moving the Atlantic Ocean into the Pacific with a teaspoon.


I am working for a very large company where, in my area, there are
still two non-communicating networks, and occasionally data is
transferred by sneaker net. Of course, this is going to be fixed any
day now...

These days, with those cigarette lighters, it's not too difficult.
You don't need three muscled males, a skid, and 10000 magtapes to
do it.

Think about the bandwidth of a 747 full of magtapes! ;-)

Dagnurbbit. Now you've got me hooked. Is this the capacity
of one of those cigarette lighters?

Cigarette lighters?

...and people long for the good ol' days; not me.

Nope. I'm happy floppies went the way of the dodo.

--
Keith

mm wrote:
....

As to convection, it was always described and seems to be limited to
broad currents, such as hot air rising and cold air sinking, ...

That's _natural_ convection, there's also _forced_ convection.
Difference is whether there is an external causative factor for the
fluid motion (fan, say) or only the thermal gradient.

mm wrote:
In high school physics, the three methods of heat dispersal were
presented as conduction, radiation, and convection?

Is that all there is? Is diffusion a fourth or is it subsumed by
convection?

Also, conniption, I believe.

In article ,
Keith Williams wrote:
In article ,
says...
In article ,
krw wrote:
In article ,
says...
In article .com,
"Edward Green" wrote:
z wrote:
Edward Green wrote:
z wrote:

Ah, you have forgotten the frequently seen fourth form, which is
wrapping the hot thing up in a towel and running with it over to
somewhere else where you drop it off. It can move a lot of heat
very
effectively.

Very good! That's non-convective mixing or mass-transport (to give
it
some important sounding names).

Actually, reminds me of the early days of networking, when one of the
fastest protocols was still sneakernet. I.e., copy a floppy full and
run it over to the other machine, thereby transferring 1.4 meg
relatively quickly.

Yes. And what do you mean 'early days'?

Not very early. Tranferring bits on a _floppy_ is like
moving the Atlantic Ocean into the Pacific with a teaspoon.


I am working for a very large company where, in my area, there are
still two non-communicating networks, and occasionally data is
transferred by sneaker net. Of course, this is going to be fixed any
day now...

These days, with those cigarette lighters, it's not too difficult.
You don't need three muscled males, a skid, and 10000 magtapes to
do it.

Think about the bandwidth of a 747 full of magtapes! ;-)

I can't. How long would it to cut those tapes? On our system
probably two years. On a system dedicated for tape copying...
a couple months?

More systems. Bandwidth is a matter of cost; it's latency that's
forever.

Most couldn't afford more systems. IIRC, those lovely TU7x
tape subsystems cost $70K..that doesn't sound quite right.


I would certainly have to increase the number of muscled males.

You would think of that. ;-)

Magtapes hurt. Those inner edges were too sharp for me to
carry them on my arms like I did DECtapes. Males were
good for hauling cartons of cards, too.

/BAH