Making Ice with Vacuum http://www.youtube.com/watch?v=pOYgdQp4euc
Check out the ideal gas law. Thanks, Kel On Sun, 2012-03-18 at 08:10 -0700, Mark Ludlow wrote: > “The steam produced in cavitation is like putting water in a bell jar > and pulling a vacuum. If there is enough vacuum the water will boil, > converting it's temperature into energy for the phase change. > Eventually you end up with a chunk of ice in the bell jar.” > > > > Not so! Not enough latent heat is lost. Sensible heat must be removed > also. In outer space, where there are huge radiative heat losses this > applies. If folks could make ice with simple vacuum pumps, who would > mess with refrigeration? It takes energy to evaporate water, not just > vacuum. > > > > Plus, when a gas is adsorbed onto a sieve, energy is released. It > takes the same energy (and then some) to regenerate the sieves. No > free lunch; no where. > > > > > > From: [email protected] > [mailto:[email protected]] On Behalf Of > [email protected] > Sent: Sunday, March 18, 2012 7:55 AM > To: [email protected] > Subject: Re: [Gasification] On the subject of H2 and O (was N2 > removal) > > > > Hi Greg, > > > > > > Sure. Let's to a simple example so my feeble mind can follow it. > When I drop cold chips in my gasifier there is some moisture content > in the chips...this is liquid water in the wood cells. As the chips > burn down into the hearth they get hot and the water changes to steam. > This phase change absorbs some amount of energy. Then as the steam > goes through the char, some of it does the water gas shift if there is > enough heat. This absorbs even more energy. The remaining steam ends > up as condensate in the cooler. > > > > > > The steam produced in cavitation is like putting water in a bell jar > and pulling a vacuum. If there is enough vacuum the water will boil, > converting it's temperature into energy for the phase change. > Eventually you end up with a chunk of ice in the bell jar. > > > > > > The water gas shift will not happen in the phase change because there > isn't sufficient activation energy availble to make the reaction go. > If it did work that way, there would be hydrogen bubbles coming off > boat propellers. That would make a COOL rooster tail! > > > > > > Gasifiers do not run a low enough pressure to vaporize the water, like > the bell jar. I can get the numbers if you want, but you need to be > in -13psi range. That's way more than we pull. > > > > > > Any clearer or still muddy?? > > > > > > Stephen > > > -----Original Message----- > From: Greg Manning <[email protected]> > To: Discussion of biomass pyrolysis and gasification > <[email protected]> > Sent: Sun, Mar 18, 2012 10:09 am > Subject: Re: [Gasification] On the subject of H2 and O (was N2 > removal) > > Hi Stephen, thanks for the reply. > > OK, I somewhat understand you, BUT, wouldn't water be doing a phase > change in the core of a gasifier as well ? > > What I was getting at, is if steam is produced in cavitation in cold > water, then wouldn't the shift effect also happen within the core > during phase transition (from water as a liquid, to water as a vapor, > when heated by the core) within the same boundaries of effect as water > to steam in the trailing edge of a propeller ? (all of these > situations involve lower that normal pressure zones). > > Aren't contrails produced in water vapor on the wing tips of an > airplane because of this same pressure drop phase shift, causing a > dew-point change? > > The core of most gasifiers runs in a dynamic lower than atmospheric > pressure ( a very low internal barometric pressure) (suction based > units), so the same shifts should apply during phase transition, > shouldn't they ? > > I understand that a pressure fed gasifier would behave differently > (and I've personally observed this) than a suction based one, I'm > speaking about suction based gasifiers. > > Somewhat lost, > Greg > > > On Sun, Mar 18, 2012 at 8:26 AM, <[email protected]> wrote: > > Greg, > > > > The energy doesn't change. The bond energy in the water is constant > > regardless of pressure. > > > > The cavitation issue is different. It is a phase change phenomenon, not a > > chemical change one. > > > > Stephen > > -----Original Message----- > > From: Greg Manning <[email protected]> > > To: Discussion of biomass pyrolysis and gasification > > <[email protected]> > > Sent: Sun, Mar 18, 2012 9:02 am > > Subject: [Gasification] On the subject of H2 and O (was N2 removal) > > > > Greetings List. > > Since we are speaking input air, I thought I might ask a somewhat > > related question. > > Water gas shift. I know there are many that have talked about this, > > and I understand the basics. > > However, here is the question. > > At what negative pressure ( negative in/wc) does the shift move down > > the temperature scale, to the point of being within the 1000 - 1200 c > > area ? > > We all know that propeller cavitation produces steam in water that is > > 10 c (or there abouts), I have to assume (not being a chemist) that > > the same negative pressure effect would also apply to other principals > > when dealing with water. > > -- > > Regards, > > Greg Manning, > > Brandon, Manitoba, Canada > > _______________________________________________ > > Gasification mailing list > > to Send a Message to the list, use the email address > > [email protected] > > to UNSUBSCRIBE or Change your List Settings use the web page > > http://lists.bioenergylists.org/mailman/listinfo/gasification_lists.bioenergylists.org > > for more Gasifiers, News and Information see our web site: > > http://gasifiers.bioenergylists.org/ > > > > > > _______________________________________________ > > Gasification mailing list > > > > to Send a Message to the list, use the email address > > [email protected] > > > > to UNSUBSCRIBE or Change your List Settings use the web page > > http://lists.bioenergylists.org/mailman/listinfo/gasification_lists.bioenergylists.org > > > > for more Gasifiers, News and Information see our web site: > > http://gasifiers.bioenergylists.org/ > > > > > > -- > Regards, > > Greg Manning, > Brandon, Manitoba, Canada > > _______________________________________________ > Gasification mailing list > > to Send a Message to the list, use the email address > [email protected] > > to UNSUBSCRIBE or Change your List Settings use the web page > http://lists.bioenergylists.org/mailman/listinfo/gasification_lists.bioenergylists.org > > for more Gasifiers, News and Information see our web site: > http://gasifiers.bioenergylists.org/ > _______________________________________________ > Gasification mailing list > > to Send a Message to the list, use the email address > [email protected] > > to UNSUBSCRIBE or Change your List Settings use the web page > http://lists.bioenergylists.org/mailman/listinfo/gasification_lists.bioenergylists.org > > for more Gasifiers, News and Information see our web site: > http://gasifiers.bioenergylists.org/ _______________________________________________ Gasification mailing list to Send a Message to the list, use the email address [email protected] to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/gasification_lists.bioenergylists.org for more Gasifiers, News and Information see our web site: http://gasifiers.bioenergylists.org/
