Fuel cells producing *liquid* water?

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?



Bob Clark

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

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


His question shows a profound lack of understanding thermodynamics.

He should start with http://en.wikipedia.org/wiki/Latent_heat

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:
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


His question shows a profound lack of understanding thermodynamics.

He should start with http://en.wikipedia.org/wiki/Latent_heat

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

...

Proton Exchange Membrane Fuel Cells.
"Hydrogen from the fuel gas stream is consumed at the anode, yielding
electrons to the anode and producing hydrogen ions which enter the
electrolyte. At the cathode, oxygen combines with electrons from the
cathode and hydrogen ions from the electrolyte to produce water. The
water does not dissolve in the electrolyte and is, instead, rejected
from the back of the cathode into the oxidant gas stream. As the PEFC
operates at about 175°F (80°C), the water is produced as liquid water
and is carried out of the fuel cell by excess oxidant flow."
http://dodfuelcell.cecer.army.mil/proton.html


Bob Clark

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

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

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

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



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.


Bob Clark

Robert Clark wrote:

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


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.

Hydrogen is one-ninth the mass of the water it is in ...
but if you want to bring water to somewhere it isn't,
9 kg of it in a 0.5-kg tank beats
1 kg of liquid hydrogen in a 15-to-40-kg tank,
even if oxygen is free at the destination.

(Very big liquid hydrogen tanks able to contain
tens or hundreds of tonnes of it can have more favorable
containment-to-payload mass ratios. 15.3 is the lowest I've
heard of at car scale, however.)


--- G. R. L. Cowan, former hydrogen fan
Boron: internal combustion, nuclear cachet:
http://www.eagle.ca/~gcowan/Paper_for_11th_CHC.html

Robert Clark wrote:
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



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.


Bob Clark


Why not just dump the water vapor to the atmosphere (global warming
gas! ack! haha) and just load up on liquid water, somewhere else,
later on?

Otherwise, as someone else mentioned, you have to invest in a heavy,
expensive condensing solution (for example, a radiator or heat
exchanger).

Michael