Pedal-Powered (Vacuum) Zeolite Refrigerator

[Vee24]

Hello All,

My question is about this video: http://www.youtube.com/watch?v=wpEG0ATylzo which seems simple enough to make, but very vague.

It seems that vacuuming the air out will cause the water in the refrigerator to boil as the guy says. At this point you close the vacuum and open the line to the Zeolite.

1. Should the tube from the vacuum go only into the fridge, or into the water?
   
2. After exposing the Zeolite to the vacuumed water, how long until the water becomes ice?
   
3. The guy says the hotter it is, the more cold you can produce, what needs heat inside the fridge or the zeolite container?
   
   

I know this doesn't exactly fit any categories here at fieldlines, but I'm sure there is someone here with enough understanding to explain this to me. I have searched the web and wasn't able to come up with a clearer understanding of how the connections are made.

Thanks for all of your help.

[spinningmagnets]

Very interesting. Here's a related video:

http://www.youtube.com/watch?v=8oCjj8iDB9I&feature=related

The Zeolite is an absorbent. According to the link I'm adding, water has molecules at various temps all at the same time, and we "feel" the average. By boiling off the hotter molecules at room temp by introducing a partial vacuum, only the colder ones are left? Perhaps the Zeolite absorbs the hotter vapor so it can't re-absorb back into the water? Conversion from liquid-to-gas absorbs much heat on its way out as it leaves water-pot.

A recent post linked to a vortex tube. Since air (or water vapor?) has various temps mixed together, the vortex tube uses centrifugal separation of the two. Ambient air goes into the middle and spins, hot air comes out one end, and cold air comes out the other. Odd stuff, I am assured by others that by cascading them, sub-zero temps can be achieved.

Perhaps we've found a truly useful job for a VAWT? driving a vacuum pump that results in ice-block formation?

I've heard mountain climbers have a hard time cooking, as high altitudes cause the water to boil away at a fairly low temp, almost impossible to achieve 200F for reasonably fast cooking of dehydrated foods. Low temps means long cooking time, and fuel weight/bulk is precious for climbers

Same physics with pressure cooker. Hard beans can only boil at 212F, so must cook a long time. By using pressure-cooker, temps can be raised to 300-400F, will cook much faster and with less fuel.

Salt-water has a much lower freeze temp than fresh water, so perhaps a salt-water vacuum experiment is in order...

[wdyasq]

If one were to do a bit of research  ... they would find a lot of information. I know I did when I looked at that process 30 years or so ago. I think the Internet allows easier research. Requesting a library get a book on loan and waiting 3 weeks to find data you already know makes a slow Internet connection seem blazingly fast.

IIRC, the French made some refrigerators for blood/drugs using water/Zeolite. Modified by alcohol or alcohol/ether it might get to a lower temperature.

BTW - you can put the zeolite in one end of a tube - or chamber, water in second part of chamber. Heat the zeolite end- driving the small amount of water out as steam, heat water, drive all air out with steam. Seal the end and the condensing steam will create a vacuum better than most refrigeration service vacuum pumps. There are lots of little tricks associated with pinching the tube and sealing it but the process is not magic.

Ron

[Vee24]

Spinningmagnets, your comments were very helpful so that I can begin to gain an elementary understanding of what's going on here. It's a simple machine, simple enough for me to make. I wonder if more vacuum or more Zeolite would make a larger  block of ice? I imagine the size of the Zeolite container should equal the size of the block of ice I want to make. If more vacuum is the answer, I'll just pedal more.

I'm not opposed to research, but this is a totally new concept to me and I needed a basic understanding to start with, and you've given me plenty to think about.

Thanks.

[spinningmagnets]

Several physical properties at play, I'm not an authority on everything thats happening. Ever heard about how boiling hot water freezes faster than cold? Proven many times, I didn't understand it.

The reason fish can breathe water is water has a propensity to absorb air, dissolved air in it acts as an insulator. If you boil water, air is removed, but you must prevent air from re-absorbing. Set boiled water outside in snow next to cold (airey) water, boiled hot water freezes faster.

Perhaps vacuum pump was doing three things, boiling off hotter molecules (leaving cold behind), Causing conversion from liquid to gas will absorb heat during phase conversion, and also removing dissolved air in water.  

This was attached to a conversation on how to make ice blocks for food preservation using primitive methods and no electricity. Ice is a good insulator too (Eskimos in Igloos?) so freezing medium should stay liquid and not form ice. Commercially, freshwater ice-blocks made in aluminum forms sitting in salt-water bath.

Have fun, and best of luck!

[Vee24]

I found a very good explanation just in case you're wondering Spinningmagnets:

In fact, when you do this, (vacuum the air) the water will boil and freeze at

the same time.

The reason is that at room temperature, water molecules are constantly

going into the air as vapor and moving back into the liquid water.  When

you heat water, you are making the vapor that comes off the water have a

higher pressure.  When the pressure gets as high as the pressure of the

surrounding air, bubbles of vapor can form inside the liquid and push

against the air.    When this happens, the liquid boils.  If you remove the

air and water vapor in a vacuum chamber, water vapor can't go back into the

liquid.  In fact, the vapor going off from the liquid will have enough

pressure to actually make bubbles in the liquid.

That's why water will boil in a vacuum chamber.  I also told you it will

freeze at the same time.  Why is this?  It turns out that water molecules

like to be next to each other in the liquid.  It takes energy to move them

into the vapor.  When water molecules are moving back and forth between the

liquid and vapor, the energy that is taken from the liquid to put molecules

into the vapor is replaced by the energy returned when molecules move from

the vapor into the liquid.  In the vacuum chamber, though, the vapor is

taken away, so none of the energy is returned to the water.  As the water

loses energy, it gets colder and finally freezes.

Richard Barrans Jr., Ph.D.

The site is from the Department of Energy and kids can write in to ask questions.

http://www.newton.dep.anl.gov/askasci/chem99/chem99558.htm

Now I know as much as the seven year old that asked the question. lol

[spinningmagnets]

This is very interesting to me. I've been googling a bit. Even though dissolved air in water acts like insulation, boiled water (with no dissolved air in it) requires more BTU's than cold water to freeze. Non-boiled water takes longer to freeze, but less BTU's than hot water.

Now I am thinking I could boil water with solar device, seal it to prevent re-absorbsion of air. Let it cool to ambient night-time temps to reduce BTU's required to get to Ice temps. Pour into an aluminum form and set form in a 20F degree salt-water bath.

So whats the cheapest/easiest way to get salt-water to 20F with no electricity?

I was just reading about pouring acetone or methanol into water, they "boil" at a much lower temp and with less vacuum than water. Kalinda refrigeration cycle (closed loop, ammonia poisons food) mixes water and ammonia. Ammonia boils out at fairly low temps, then exposure to water causes the air-cooled ammonia vapor to strongly be re-absorbed, causing sudden strong chilling.

A VAWT or water-wheel can pump water to fill a very tall vertical pipe. If the top is sealed and if you open a valve at the bottom, the water draining out will draw a pretty good vacuum at the top. A 1/4" stainless hydraulic tube can connect the vacuum to the salt-water chamber. Acetone or methanol (ammonia?) boiling away could chill the saltwater to a very low temp.

If Acetone, Methanol, or Ammonia react badly with saltwater, then the chilling substance can be in tubes set in the cold bath, instead of poured directly into the salt-water. Draw a vacuum on the chilling substance to create a liquid-to-gas phase change instead of a vacuum on the the salt-water bath.

Whichever substance works best (methanol can be made, acetone or ammonia must be bought) it could be captured and condensed back into a liquid for re-use.

[spinningmagnets]

Here's more video of note:

http://www.youtube.com/watch?v=w-JFoOQv4B0&feature=related

British lab video makes ice from applying vacuum to room temp water

http://www.youtube.com/watch?v=8oCjj8iDB9I&feature=related

Vacuum takes 19C/66F water to frozen 0C/32F

Another video shows a classroom taking 90C/194F water and applying vacuum, water boils and ends up at 60C/140F.

So now it sounds like if summer night-time temps are 30C/60F or lower, we could make ice with a vacuum alone, without having to add any extra process such as a Vortex tube or closed-loop acetone evaporator.

[Vee24]

This is becoming clear to me, the video about an Edwards pump shows just how simple it is. My plan is to do it as simply as possible. I have plans to buy a campsite and the cabins will need ice boxes, this solves that problem.

I found this site http://www.dream-models.com/eco/vacuumpump.html that shows how to build a vacuum pump from a refrigerator compressor. An old fridge will be recycled to use as the vacuum chamber, now the compressor can be recycled too. This project is getting cheaper all the time. I have never seen the inside of a compressor, I'm hoping there is a wheel I can attach a fan belt to so it can be powered by a bike.

[southpaw]

HI VEE24

Fridge compressors are sealed units and can't be converted from electric drive to

mechanical. You might be better to try an air conditioning compressor from a car.

Remove the clutch/pulley assembly and install a sprocket and Bob's your uncle.

[Vee24]

Thanks for the info Southpaw.

[spinningmagnets]

The whole "vacuum ice making" and "Vortex tube" are new to me, and the more read, the more odd they seem. Sometimes called the Ranque-Hilsch tube.

The numbers have already been crunched, and if you are using electricity, the amount of watts needed to make a certain amount of BTU transfer is cheaper when you use a conventional freezer to make ice, but...

This article sounds certain that if you use compressed air that is allowed to cool to 65F, when it is run through a Vortex tube, its not hard to get +140F from one end and -10F from the other.

Thats a lot better than I hoped for, and a pump that produces a vacuum from one side could produce pressure on the other. A vac tank and a pressure tank could store the two pressure states, applying vacuum could take 65F water down to 32F, and the cold vortex exhaust could take it down more to guarantee a solid freeze.

http://www.visi.com/~darus/hilsch/#fig237

http://en.wikipedia.org/wiki/Vortex_tube

[Vee24]

The Vortex Tube sounds promising Spinningmagnets. It may even play a role in what I'm thinking of now.

Now that I know how to make ice for my cabins, I'm wondering what I'd have to do to keep the water hot instead of allowing it to freeze? Zeolite takes out the vapor which allows it to freeze, but what would happen if I had a vacuum fridge without Zeolite? Would opening the door take the vapor out and it would freeze anyway, or would it remain hot? Even if opening the door causes freezing, a heat exchanger could take heat out of the boiling water without opening the door. I would think that without the Zeolite the vapor would fall back into the water and it would remain hot. If so, I have a very simple solution to hot water heating in the cabins.

[spinningmagnets]

The way I'm understanding it (still learning) in a set volume of 60F water, There are some molecules at 30F and others at 90F, and we "feel" the average. Weird stuff.

When I said the hotter water boiled off when a vacuum was applied to it, remember that "boiling" can occur at a low temp in a lower pressure (vacuum). The exhaust of the vacuum pump on this zeolite fridge might have vaporised water molecules that had temps from 90F to 40F (I'm guessing) so the average temps of what we "feel" in the exhaust might be 50F-ish. Not hot by any measure.

and once the water vapor molcules hit the exhaust normal pressure of atmosphere, I suspect they would immediately condense back into liquid. I'm sure the zeolite performs a valuable service, and it is cheap, but the videos show ice being produced without any.

Concerning the vortex tube (I haven't built one, this is just a guess) there is a greater range of temps in the split exhaust than the vacuum-on-water experiment.

This is curious, and I'm going to guess that since its stated that colder temps are achieved by choking the exhaust (also good for conserving compressed air) I believe there is some compression heating occurring in the swirl chamber.

Any heat energy that is concentrated by compression will like wise leave less energy in the colder half of that set volume of air. I was quite suprised by the articles stating that although well-engineered units have better performance, it is commonly possible to produce -10F and +140F from +65F compressed air.

I am skeptical, but very interested. If you take 65F water, and begin to draw out BTU's, the water temp change will occur at a fairly steady rate compared to the BTU shifting rate. Then once the water reaches 32F, it requires a lot of BTU's to produce the phase change to ice. Gas-to-liquid, and liquid-to-solid phase changes in either direction take a lot of heat energy being shifted. So, ice and water can both exist at 32F.

I am convinced that drawing a vacuum can chill 65F water down to near freezing, but consistent production of solid block ice is something that I'm certain will need a little something extra.

If this works, the vortex tube "might" be able to take 1/2 gallon of 32F "vacuumed" water and convert it to solid ice. But if you are hoping to heat up 55 gallons of 55F water for campers to take a 80F bath, the vortex tube will most likely fall way short.

For hot water, there are many great solar ideas over at ww.builditsolar.com

[Vee24]

Yeah, the vacuum thing was all lower temps because the air pressure was lowered. I guess I'd have to experiment to find out just how hot I can bring water to. Good point, the video didn't use Zeolite at all. So opening the door would cause the "boiled" water to freeze.

The cabins are all under huge trees, so my only solution so far was to run a line from a sunny spot where a solar panel could be. The place is so beautiful that I didn't want to clutter the place with solar panels in the few sunny places. So I thought this might be a better solution, and one I think is worth trying out.

Even if I can't acheive block ice, maybe I could try salt, acetone, or methanol as you suggested earlier.

You sound like you're in the engineering field, are you?

[spinningmagnets]

Not an engineer, just an old mechanic and truck driver who reads too much. I'm glad you brought this link to my attention. Have fun.