Who Will Stand This Mighty Destroyer of Pretend Engineers?

You tell 'em Rod. You are one pistol of a debater!

Not many folk here will demand that a poster "prove" he's satisfied.

What medication do they have you on?


Bret Cahill

 

The dialogue which shows that you're either terminally stupid or a two
faced liar or a terminally stupid two faced liar follows.

.. . .

Squirm, bitch.

.. . .

More stupidity.

.. . .

Everyone can see for themselves that you are lying, you pathetic excuse for a bullshit artist.

Got something like a poll to prove it?

"No one lies like the indignant."

-- Nietzsche

You need to read the header of this thread again.


Bret Cahill

 

OK, no flaming on my threads.

You _must_ be respectful to every clueless piece of bat crap here on
newsgroups.


Bret Cahill

 

OK, no flaming on my threads.

You get to wear asbestos threads,

Nope. Illegal.

Pathetic.

.. . .

Hope you get mesothelioma.

Ain't gonna happen. You must inhale asbestos to get mesothelioma and
even then the disease is rare.

Pathetic.


Bret Cahill

 

On Jul 31, 6:15 am, Bret Cahill <BretCah...@aol.com> wrote:

At least someone is on topic.

Commercially available stacked flat plat heat exchangers are far more
efficient.. (no need for a working fluid, greater surface area,

Fins work in fluidization as well

higher
heat transfer coefficient.) .

The heat transfer coefficient is an order of magnitude greater with
particle bed fluidization.

I thought I made that clear.

Bret Cahill

So you've re-invented the fluidized bed?

How does your version compare with, say, a Fischer-Tropsch slurry
reactor?

While you're at it, I'm really curious to see your derivation of the
heat transfer coefficient.

Michael

 

On Aug 2, 4:35 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com>
wrote:

Rod Speed wrote:
Eeyore <rabbitsfriendsandrelati...@hotmail.com> wrote
Rod Speed wrote
John Larkin wrote
Eeyore wrote
John Larkin wrote
Rod Speed wrote
John Fields <jfie...@austininstruments.com> wrote

And you?

I piss on clowns like you from a great height.

You get to like that or lump it, child.

What could you possibly know about great heights?

I'm hard pressed to tell who's the least imaginative insulter.
Cahill or Speed.

Both are amateurs, at technology and at insulting.

You three clowns in spades.

Oh dear that actually made me laugh out loud.

A brainless jerk insults 3 engineers whose products
have sold in the (most likely tens of ) thousands

Just another pathetic excuse for an insult any 2 year old could leave for dead.

Search ebay for "studiomaster" in my case..

Graham

Wow, you used to work for Studiomaster?

Did they get bought out at some point?

Do you have a website of your designs?

Thanks,

Michael

 

[Bret Cahill]

At least someone is on topic.

Commercially available stacked flat plat heat exchangers are far more
efficient.. (no need for a working fluid, greater surface area,

Fins work in fluidization as well

higher
heat transfer coefficient.) .

The heat transfer coefficient is an order of magnitude greater with
particle bed fluidization.

I thought I made that clear.

So you've re-invented the fluidized bed?

How does your version compare with, say, a Fischer-Tropsch slurry
reactor?

It's a heat exchanger, not a reactor.

For example, breakup of catalyst particles isn't an issue here because
the particle bed can be made of hollow metal spheres, metal coated
glass or ceramic bubbles.

While you're at it, I'm really curious to see your derivation of the
heat transfer coefficient.

It's empirical. You can easily run your own tests if you don't trust
the numbers in the literature. Set a cooler of ice water up on a
shelf and siphon the water through an aluminum or copper tube in the
bed and measure the temp. increase.

Unless there's been some recent breakthroughs, the theory still isn't
completely understood.

One theory claims that the particles tunnel through the boundary
layer, contact the surface and then back out to transfer heat with the
gas. They set up the problem with these unconvincing drawings of a
sphere contacting a flat surface. It's a 2 or more step process and
even with millions of contacts/second, it's a dubious theory.

Recently I heard of another more plausible theory that claims the
boundary layer thins or dissipates with fluidization. The effective
density, Reynolds number and turbulence increase so the flow situation
is closer to a liquid than a gas.

It'd be nice for them to get the theory right. It could save a lot of
time optimizing.

What's really interesting is out of a couple dozen ME books on heat
transfer, particle bed fluidization will get mentioned maybe once in a
foot note. It simply isn't studied in ME. All the work has been in
chemical engineering, starting back in WWII to crack petroleum.

Another example of the desirability of multidiciplinarity.


Bret Cahill

 

On Aug 6, 9:54 am, Bret Cahill <BretCah...@aol.com> wrote:

At least someone is on topic.

Commercially available stacked flat plat heat exchangers are far more
efficient.. (no need for a working fluid, greater surface area,

Fins work in fluidization as well

higher
heat transfer coefficient.) .

The heat transfer coefficient is an order of magnitude greater with
particle bed fluidization.

I thought I made that clear.
So you've re-invented the fluidized bed?
How does your version compare with, say, a Fischer-Tropsch slurry
reactor?

It's a heat exchanger, not a reactor.

For example, breakup of catalyst particles isn't an issue here because
the particle bed can be made of hollow metal spheres, metal coated
glass or ceramic bubbles.

While you're at it, I'm really curious to see your derivation of the
heat transfer coefficient.

It's empirical. You can easily run your own tests if you don't trust
the numbers in the literature. Set a cooler of ice water up on a
shelf and siphon the water through an aluminum or copper tube in the
bed and measure the temp. increase.

Unless there's been some recent breakthroughs, the theory still isn't
completely understood.

One theory claims that the particles tunnel through the boundary
layer, contact the surface and then back out to transfer heat with the
gas. They set up the problem with these unconvincing drawings of a
sphere contacting a flat surface. It's a 2 or more step process and
even with millions of contacts/second, it's a dubious theory.

Recently I heard of another more plausible theory that claims the
boundary layer thins or dissipates with fluidization. The effective
density, Reynolds number and turbulence increase so the flow situation
is closer to a liquid than a gas.

It'd be nice for them to get the theory right. It could save a lot of
time optimizing.

What's really interesting is out of a couple dozen ME books on heat
transfer, particle bed fluidization will get mentioned maybe once in a
foot note. It simply isn't studied in ME. All the work has been in
chemical engineering, starting back in WWII to crack petroleum.

Another example of the desirability of multidiciplinarity.

Bret Cahill

Are you using the heat transfer text by Incropera and De Witt?

Perry's Chemical Engineers' Handbook gives a good overview of heat
transfer and fluidization theory.

Michael

 

[Bret Cahill]

At least someone is on topic.

Commercially available stacked flat plat heat exchangers are far more
efficient.. (no need for a working fluid, greater surface area,

Fins work in fluidization as well

higher
heat transfer coefficient.) .

The heat transfer coefficient is an order of magnitude greater with
particle bed fluidization.

I thought I made that clear.
So you've re-invented the fluidized bed?
How does your version compare with, say, a Fischer-Tropsch slurry
reactor?

It's a heat exchanger, not a reactor.

For example, breakup of catalyst particles isn't an issue here because
the particle bed can be made of hollow metal spheres, metal coated
glass or ceramic bubbles.

While you're at it, I'm really curious to see your derivation of the
heat transfer coefficient.

It's empirical. �You can easily run your own tests if you don't trust
the numbers in the literature. �Set a cooler of ice water up on a
shelf and siphon the water through an aluminum or copper tube in the
bed and measure the temp. increase.

Unless there's been some recent breakthroughs, the theory still isn't
completely understood.

One theory claims that the particles tunnel through the boundary
layer, contact the surface and then back out to transfer heat with the
gas. �They set up the problem with these unconvincing drawings of a
sphere contacting a flat surface. �It's a 2 or more step process and
even with millions of contacts/second, it's a dubious theory.

Recently I heard of another more plausible theory that claims the
boundary layer thins or dissipates with fluidization. �The effective
density, Reynolds number and turbulence increase so the flow situation
is closer to a liquid than a gas.

It'd be nice for them to get the theory right. �It could save a lot of
time optimizing.

What's really interesting is out of a couple dozen ME books on heat
transfer, particle bed fluidization will get mentioned maybe once in a
foot note. �It simply isn't studied in ME. �All the work has been in
chemical engineering, starting back in WWII to crack petroleum.

Another example of the desirability of multidiciplinarity.

Bret Cahill

Are you using the heat transfer text by Incropera and De Witt?

Perry's Chemical Engineers' Handbook gives a good overview of heat
transfer and fluidization theory.

What's the HX mechanism?

Does the boundary layer stay intact with the particles passing through
the layer?

Or does the boundary layer breakdown?

What's really interesting is out of a couple dozen ME books on heat
transfer, particle bed fluidization will get mentioned maybe once in a
foot note. It simply isn't studied in ME. All the work has been in
chemical engineering, starting back in WWII to crack petroleum.

Another example of the desirability of multidiciplinarity.


Bret Cahill

 

On Aug 6, 10:58 am, Bret Cahill <BretCah...@aol.com> wrote:

Are you using the heat transfer text by Incropera and De Witt?

Perry's Chemical Engineers' Handbook gives a good overview of heat
transfer and fluidization theory.

What's the HX mechanism?

Beats me... what HX mechanism?

Does the boundary layer stay intact with the particles passing through
the layer?

Or does the boundary layer breakdown?

What's the Reynolds number? Above 2100 or so you have turbulent flow,
and the best you can do is use correlations.

You're a Mech E, huh? Where/when did you graduate?

Michael

 

[James Beck]

In article <baafdda5-d144-4fc9-afc6-e79914840e93
@v39g2000pro.googlegroups.com>, mrdarrett@gmail.com says...

On Aug 6, 12:03 pm, Bret Cahill <BretCah...@aol.com> wrote:

You're a Mech E, huh?

Like I said, they never mention fluidization in ME. I studied it very
little formally. I read up on it later trying to eliminate film
cooling in gas turbines and to increase HX in Stirling.

Bret Cahill


Oh, HX = Heat Transfer?

Stirling... good luck. Entire companies have tried, and apparently
failed, to commercialize that. Keeping the working gas from escaping
from the seals is apparently... difficult.

Michael

Another one of those technologies that does not scale up well.

Just make a gigantic version of the drinking bird. Heat its' ass and
have the beak dip in a river.

http://www.magic.org/store/product_info.php?products_id=1369

 

[Bret Cahill]

Perry's Chemical Engineers' Handbook gives a good overview of heat
transfer and fluidization theory.

What's the HX mechanism?

Beats me... what HX mechanism?

What's their theory on why fluidization works?

Glass microspheres look remarkably like a boiling liquid but looks can
be deceiving.

Does the boundary layer stay intact with the particles passing through
the layer?

Or does the boundary layer breakdown?

What's the Reynolds number? �Above 2100 or so you have turbulent flow,

I can't say. With particle-gas, the "density" is of course much
higher but the "viscosity" increases as well. The HX improves with
smaller particle size down to 10 microns where it starts to go back
down.

With liquid-particle the HX will max out at 0.5 - 1 cm dia because
smaller particles just increase the "viscosity."

and the best you can do is use correlations.

It's not my job to figger it out.

You're a Mech E, huh? ďż˝

Like I said, they never mention fluidization in ME. I studied it very
little formally. I read up on it later trying to eliminate film
cooling in gas turbines and to increase HX in Stirling.


Bret Cahill

 

On Aug 6, 12:03 pm, Bret Cahill <BretCah...@aol.com> wrote:

You're a Mech E, huh?

Like I said, they never mention fluidization in ME. I studied it very
little formally. I read up on it later trying to eliminate film
cooling in gas turbines and to increase HX in Stirling.

Bret Cahill

Oh, HX = Heat Transfer?

Stirling... good luck. Entire companies have tried, and apparently
failed, to commercialize that. Keeping the working gas from escaping
from the seals is apparently... difficult.

Michael

 

[Bret Cahill]

You're a Mech E, huh?

Like I said, they never mention fluidization in ME. �I studied it very
little formally. �I read up on it later trying to eliminate film
cooling in gas turbines and to increase HX in Stirling.

Bret Cahill

Oh, HX = Heat Transfer?

That's the happin' field. What gets me is the average 1 star chef
knows more about HX than most engineers, at least in a qualitative
sense.

Stirling... good luck. �Entire companies have tried,

Hundreds maybe thousands.

and apparently
failed, to commercialize that. ďż˝

San Diego Gas & Electric recently ordered 16,000 25 kW dishs from
Stirling Energy, eventually more for a total of 48,000 for a 1 GW
plant, the biggest solar thermal in the world.

After 200 years Stirling may finally become a production engine.

Even gas turbines only took 80 years.

Keeping the working gas from escaping
from the seals is apparently... difficult.

They pump it back into the cylinder. If the generator is inside of
the housing then exterior dynamic seals or glands are eliminated, i.
e., Sunpower.

There are only two low parasitical loss strategies to increase HX in a
Stirling:

1. Increase pressure to 50 - 200 bar 750 - 3,000 psi to increase
density to increase Reynolds to increase Nusselt to increase the HX
coefficient. This is the most popular strategy in Stirling today.

2. Another is to increase surface area. By a lot.

The best way to do this is with slightly flexing heat exchanger
_inside_ of the cylinder. Coils of rectangular thin tubing in the
heater side compress flat which accomplishes the same thing as the
conventional displacer, forcing the gas through a regenerator and on
to the cold side.

On the addition-of-heat stroke the heater coils expand separating
slightly to allow the gas to flow in and be heated. A thermofluid is
pumped through the coils.

This could be open cycle air -- valves on the cold side -- as this
heater will be effective even at atmospheric pressures.

It could easily be designed to keep the stresses and strains below any
fatigue limit at operating temp. by increasing the cylinder size.

Everything deflects to a certain extent which is how statically
indeterminate structures are evaluated. That's where I got that idea.


Bret Cahill

 

Bret Cahill wrote:
....

There are only two low parasitical loss strategies to increase HX in a
Stirling:

1. Increase pressure to 50 - 200 bar 750 - 3,000 psi to increase
density to increase Reynolds to increase Nusselt to increase the HX
coefficient. This is the most popular strategy in Stirling today.

Interesting. How thick must the (stainless steel) wall of the gas
pressure vessel be, to support a MAWP of 3,000 psi?

Let's say the outer wall of the pressure vessel is exposed to
concentrated sunlight at 400 C. At steady state, what will be the
temperature of the inner wall?

Michael

 

[Bret Cahill]

1. �Increase pressure to 50 - 200 bar 750 - 3,000 psi to increase
density to increase Reynolds to increase Nusselt to increase the HX
coefficient. ďż˝ This is the most popular strategy in Stirling today.

Interesting. �How thick must the (stainless steel) wall of the gas
pressure vessel be, to support a MAWP of 3,000 psi?

The top [hot side] of a beta cylinder is spherical to reduce stresses.

Let's say the outer wall of the pressure vessel is exposed to
concentrated sunlight at 400 C. ďż˝

More like 1,000 C. They use an aperture and maybe heat pipes.

At steady state, what will be the
temperature of the inner wall?

They're getting over 30% efficiency, better than anything else that
affordable.

It's a derivative of a Swedish sub engine.


Bret Cahill

 

On Aug 6, 11:09 am, mrdarr...@gmail.com wrote:

On Aug 6, 10:58 am, Bret Cahill <BretCah...@aol.com> wrote:

Are you using the heat transfer text by Incropera and De Witt?

Perry's Chemical Engineers' Handbook gives a good overview of heat
transfer and fluidization theory.

What's the HX mechanism?

Beats me... what HX mechanism?

Does the boundary layer stay intact with the particles passing through
the layer?

Or does the boundary layer breakdown?

What's the Reynolds number? Above 2100 or so you have turbulent flow,
and the best you can do is use correlations.

My bad... for cylindrical boundary layers, if the Reynolds is 40 to
5000 you form a Karman vortex trail (street?).
http://en.wikipedia.org/wiki/Von_K%C3%A1rm%C3%A1n_vortex_street

See also D'alembert's paradox
http://en.wikipedia.org/wiki/D'Alembert's_paradox

Michael