Fuel cells producing *liquid* water?

Robert Clark wrote:


Batteries would not give you *liquid* water while carrying 1/8th the
weight of the water in fuel. That's an important part of my
application.

Are you building a space vehicle?

Robert Clark wrote:

Don Lancaster wrote:

You have to recognize that converting water vapor to liquid consumes
energy and has to be charged against the fuel cell efficiency budget.

Batteries are almost certainly more cost effective.

http://www.tinaja.com/glib/energfun.pdf

Batteries would not give you *liquid* water while carrying 1/8th the
weight of the water in fuel. That's an important part of my
application.

You specifically need/want the water ?

I liked the liquid N2 idea for the condensor btw. Dry Ice would be another
possible and easier to handle.

Graham

Converting vapor to liquid releases energy. Power source for
thunderstorms and hurricanes.


Don Lancaster wrote:
Robert Clark wrote:
Eeyore wrote:

Robert Clark wrote:


For my application I need a hydrogen/oxygen fuel cell to produce the
H2O in liquid form. But in addition to the electrical energy, the
reaction releases a significant proportion of the energy as heat.
Enough heat in fact to turn the H2O released into steam. I know on
space missions they use fuel cells to produce liquid water but I assume
they use the cryogenic fuels onboard to liquify the water.
Is there a way to insure the water released is in liquid form for the
H2 and O2 at room temperature?

Cool the water vapour.

Graham


A heat exchanger (radiator) might do it. Or quickly exapnding it into
a larger volume.
For my application I want the system to be lightweight.

Bob Clark

You have to recognize that converting water vapor to liquid consumes
energy and has to be charged against the fuel cell efficiency budget.

Batteries are almost certainly more cost effective.

http://www.tinaja.com/glib/energfun.pdf


--
Many thanks,

Don Lancaster voice phone: (928)428-4073
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
rss: http://www.tinaja.com/whtnu.xml email:

Please visit my GURU's LAIR web site at http://www.tinaja.com

dangerdoc wrote:
Converting vapor to liquid releases energy. Power source for
thunderstorms and hurricanes.


Don Lancaster wrote:

Robert Clark wrote:

Eeyore wrote:


Robert Clark wrote:



For my application I need a hydrogen/oxygen fuel cell to produce the
H2O in liquid form. But in addition to the electrical energy, the
reaction releases a significant proportion of the energy as heat.
Enough heat in fact to turn the H2O released into steam. I know on
space missions they use fuel cells to produce liquid water but I assume
they use the cryogenic fuels onboard to liquify the water.
Is there a way to insure the water released is in liquid form for the
H2 and O2 at room temperature?

Cool the water vapour.

Graham


A heat exchanger (radiator) might do it. Or quickly exapnding it into
a larger volume.
For my application I want the system to be lightweight.

Bob Clark


You have to recognize that converting water vapor to liquid consumes
energy and has to be charged against the fuel cell efficiency budget.

Batteries are almost certainly more cost effective.

http://www.tinaja.com/glib/energfun.pdf


--
Many thanks,

Don Lancaster voice phone: (928)428-4073
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
rss: http://www.tinaja.com/whtnu.xml email:

Please visit my GURU's LAIR web site at http://www.tinaja.com



What I thought I said is not what you think I meant.

If the latent energy is "thrown away" such as through a radiator, it has
to be charged against the fuel cell efficiency.

http://www.tinaja.com/glib/energfun.pdf


--
Many thanks,

Don Lancaster voice phone: (928)428-4073
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
rss: http://www.tinaja.com/whtnu.xml email:

Please visit my GURU's LAIR web site at http://www.tinaja.com

Don Lancaster wrote:

You have to recognize that converting water vapor to liquid consumes
energy and has to be charged against the fuel cell efficiency budget.


Wow, you got that completely backwards.

Water vapor gives up energy when it condenses to liquid. You could
harvest additional energy from the steam as it cools back to room
temperature.

Dave

Batteries are almost certainly more cost effective.

http://www.tinaja.com/glib/energfun.pdf


--
Many thanks,

Don Lancaster voice phone: (928)428-4073
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
rss: http://www.tinaja.com/whtnu.xml email:

Please visit my GURU's LAIR web site at http://www.tinaja.com

dave e wrote:
Don Lancaster wrote:


You have to recognize that converting water vapor to liquid consumes
energy and has to be charged against the fuel cell efficiency budget.



Wow, you got that completely backwards.


Not really.

Some of the extracted fuel cell energy is in the form of latent heat
that created the gaseous state.

If you cool to liquid water by removing heat and throwing it away in a
radiator or whatever, that energy is gone and not available for the
useful intended application.

Thus, the fuel cell efficiency goes DOWN unless you do something useful
with the latent heat extraction. The low delta-T and Carnot guarantees
useful extraction will be inefficient and enormously difficult.

But the whole project makes no sense whatsoever.


--
Many thanks,

Don Lancaster voice phone: (928)428-4073
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
rss: http://www.tinaja.com/whtnu.xml email:

Please visit my GURU's LAIR web site at http://www.tinaja.com

On 16 Aug 2006 11:02:25 -0700, "Robert Clark"
wrote:

Eeyore wrote:
Robert Clark wrote:

For my application I need a hydrogen/oxygen fuel cell to produce the
H2O in liquid form. But in addition to the electrical energy, the
reaction releases a significant proportion of the energy as heat.
Enough heat in fact to turn the H2O released into steam. I know on
space missions they use fuel cells to produce liquid water but I assume
they use the cryogenic fuels onboard to liquify the water.
Is there a way to insure the water released is in liquid form for the
H2 and O2 at room temperature?

Cool the water vapour.

Graham

A heat exchanger (radiator) might do it. Or quickly exapnding it into
a larger volume.
For my application I want the system to be lightweight.

Bleed liquid nitrogen to the atmosphere close to the outlet. Slowly!
Be careful, or you will get to very low temperatures indeed.

Recently, I was doing some work with a little heated/cooled stage for
samples for a spectrometer. Someone left the nitrogen leaking away for
a few minutes, and the temperature control software stopped working.
We waited for a quater of an hour, and the software started working
again with the thermocouple reporting minus 60C.

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

Robert Clark wrote:
For my application I need a hydrogen/oxygen fuel cell to produce the
H2O in liquid form. But in addition to the electrical energy, the
reaction releases a significant proportion of the energy as heat.
Enough heat in fact to turn the H2O released into steam. I know on
space missions they use fuel cells to produce liquid water but I assume
they use the cryogenic fuels onboard to liquify the water.
Is there a way to insure the water released is in liquid form for the
H2 and O2 at room temperature?

Try using the cell's output to power a refrigerator to cool it.

Less facetiously, you might try condensing the water in a radiator.
The heat has to go *somewhere*.

Tom Davidson
Richmond, VA

tadchem wrote:

Try using the cell's output to power a refrigerator to cool it.

I'm *so* glad that was a joke ! You nearly had me going there. ;~)

Graham