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DIY Refrigeration

09/23/2010 7:44 PM

I am looking for a way to do a DIY demo for refrigeration using some 'simple' apparatus. Enough to cool about 30F from ambient would be great.

There is always an ammonia cycle and the 'Einstein Cycle', but i haven't found a convenient way to do either at home with any ease (and safety).

Suggestions?

No, this is not to cool my beer or the house, but they would always look to be good 'expansions on the topic' for another time. This is not a school project, just a backyard builder kind of guy.

Links to other web sites or other folks DIY work is apprecaited.

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#1

Re: DIY Refrigeration

09/23/2010 7:47 PM

A mix of ice and salt and a little water; makes a pretty good method of cooling/freezing.

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#2

Re: DIY Refrigeration

09/23/2010 8:53 PM

If you are trying to avoid mechanical parts (compressor) and can weld steel, an ammonia/water absorption system might be the way to go. I think the Einstein cycle is a version of this. RV fridges do it with hydrogen added on the evaporator side to nearly equalize the pressure throughout.

Don't reenact The Mosquito Coast, though....

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#3

Re: DIY Refrigeration

09/23/2010 9:13 PM

Vortex cooling is great. You need a supply of compressed air. It exhausts hot air out the other end.

Another simple device uses the 'peltier' effect. Pretty simple, you need electricity, DC will do. Igloo cooler has them.

I don't know if a 'swamp cooler' will drop thirty degrees, that's a lot for evaporating water.

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#10
In reply to #3

Re: DIY Refrigeration

09/25/2010 5:58 AM

Ranque-Hilsch vortex tube

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#4

Re: DIY Refrigeration

09/24/2010 10:44 AM

For 'event cooling' the salt and ice is great (Lots of ice cream is made this way), but I was really looking for a continuous refrigeration device.

I like the ammonia cycle, just don't know how to get started on making it myself. Pointers?

The Einstein cycle is pretty interesting, like the ammonia cycle it doesn't require pumps I understand but it is a butane/water cycle from what I read. (Ammonia cycle is really ammonia/water as well I think).

Thanks for the feedback.

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#5
In reply to #4

Re: DIY Refrigeration

09/24/2010 3:30 PM

The textbook Modern Industrial Refrigeration shows several absorption refrigeration schematics, but they are not detailed fabrication drawings. For the continuous type, like an RV fridge which is rather complex, some of the features are unclear. There is also a kerosene-fueled intermittent type that burns for about half an hour, then refrigerates for while (a few hours maybe?), and then by virtue of good insulation holds a decent temperature overnight. It is quite a bit simpler and could likely be a great DIY project. Please keep us posted if you give it a try. I don't remember where, but I think I have seen similar schematics on line.

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#6
In reply to #5

Re: DIY Refrigeration

09/24/2010 6:16 PM

My mom told me about having a Kerosene refrigerator back in the 1920's on a farm in west Texas, before electricity was available. My dad told me those were basically ammonia cycle refrigerators. (His specialty was HVAC in the 1950-80's)

From what I can tell that is like the LP or natural gas ones we can buy today (and cost a lot compared to electrical ones).

It wasn't to long ago I remember the natural gas company promoting natural gas air conditioning, that has to be based on a similar heat cycle.

... On the vortex cooling, yes Hilch-Vortex tubes (I think that is their 'real name' if my memory is right) are great by they do take a lot of compressed air to work. I remember seeing an article in the book "The Scientific American Book of Projects for the Amateur Scientist' edited by C.L.Stong. Great project, but to much energy for my needs this time!

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#7
In reply to #6

Re: DIY Refrigeration

09/24/2010 11:24 PM

there is a firm who use evacuated tube as a heat source to make airconditioning.

The old Kero Fridge idea I would presume where the kero flame made the heat, I remember when I was a kid that the frigde would freeze if the flame got to hot.

Concentrated solar collector would be another way of powering such a system, the sunnier and hotter day the better the thing would cool. I think pumps and fans would still be needed to move air and move the fluid.

Google sun powered airconditioning and see what comes up.

There are schematics I have seen showing how the system works in regards to gas or kero fridges.

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#8

Re: DIY Refrigeration

09/24/2010 11:39 PM

As mentioned above, the peltier system is simple and efficient. Basically a thermocouple run backwards. If current flows one direction, it cools. In the other direction, it heats.

You need DC to make it work, but 12v "panels" of junctions are readily available.

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#9

Re: DIY Refrigeration

09/25/2010 3:56 AM

Einstein never got his fridge to work-the simple principle behind kero/gas etc is ammonia/water adsorption-us rednecks used a blast of compressed gas or whatever to cool instantly our beer cans- before refrigeration was invented by an Australian in 1854- we used the evaporation latent heat to cool our goodies- still works!.

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#11

Re: DIY Refrigeration

09/25/2010 6:10 AM

'No, this is not to cool my beer or the house, but they would always look to be good 'expansions on the topic' for another time. This is not a school project, just a backyard builder kind of guy.'

THEN WHAT IS IT FOR?

I always an leery about those who don't say what it is they are actually trying to do.

I read your profile and would guess that it is to cool the other side of a sterling engine trying to extract more nrg using solar heat?

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#16
In reply to #11

Re: DIY Refrigeration

09/27/2010 10:35 AM

It is just a backyard project. When/if I get it to work, I'll probably carry it down to the local maker group for a bit of 'show and tell'. Mainly to say I got it done to myself.

Yes, not all persons who say it is a backyard builder kind of project have 'alterior motives'. ... I can dream of it being 'safe and cheap' so I can cool my house for free, but that is a pipe dream and I know it. With it working it would more likely be made up for a traveling exhibit I could take to the local 'science museum' or high schools so it could be used as a prop in an educational setting. Again, all that is being a pipe dream until after it works. ... Thanks for asking.

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#17
In reply to #16

Re: DIY Refrigeration

09/27/2010 1:19 PM

I like your idea and the fact that you want to share knowledge. If I had more time on my hands and enough resources I probably be doing some what of the same. At best all I can do at this time is volunteer to assist in skills challenge events, associated with the HVAC industry. I have seen many a young person that hated math, chemistry and physics until they found a practical real world use for them.

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#19
In reply to #17

Re: DIY Refrigeration

07/29/2012 12:11 AM

My son went to college at Olin College of Engineering in the Boston MA area. They way of teaching is just what he needed. ... They gave great high-achieving students problems to solve. Sometimes they get solved, but the idea is they work on them long enough to understand they need more knowledge. Then the profs (sometime team teaching) come in and teach the theory it takes to solve the problem at hand.

Sometimes the 'team teachers' mix, say Physics and History (and easy combo in my experience) or Math and mech.engr, ... or whatever it takes. The big deal is the theory and math are NOT ignored or bypassed, just delayed till it became a 'teachable moment'.

Yes there were dry times in education, but the trick of making someone WANT to learn is the power they have managed to develop.

... sorry, just my random thoughts.

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#12

Re: DIY Refrigeration

09/25/2010 7:09 AM

It depends on what you have available for resources. If you have a lake or ocean handy, you can make a simple heat exchanger. If compressed gas is available, a joule cooler is fun and instructive. A neat evaporative cooler can be had by putting a fluid in a permeable container, like an unfired clay pot or a tightly woven straw basket.

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#13

Re: DIY Refrigeration

09/26/2010 1:38 AM

Since nobody has mentioned it yet, I will just chime in with the cold-air system. This uses air as the working fluid, and was the first refrigeration system used commercially, and for cooling perishable cargoes aboard ship. Air is compressed, then sent to a heat exchanger to dump the heat of compression; a water separator is provided here as well if ambient air is used. From the heat exchanger, it goes to an expander which recovers part of the work of compression (minus the enthalpy removed by the heat exchanger). From there, the now very cold air goes to the space to be refrigerated; either it is allowed to go directly into the space, or in closed-cycle systems it runs through a large heat exchanger. As soon as efficient phase-change (reverse Rankine cycle) refrigerators were available using safe refrigerants (the much-persecuted freons), these machines disappeared because their COPs are very low, but they still have valid applications in special circumstances. An attempt was made to revive this cycle for automotive air conditioning in the 1970s under the name ROVAC; here the compressor and expander were ingeniously combined in a single vane pump/expander unit. More recently, Yours Truly studied this cycle for a chiller/icemaker for use on fishing boats at sea, to keep the catch fresh. It made good sense in that application, taking up little space and requiring essentially no additional maintenance (open cycle system). I suspect it would make sense for air conditioning and refrigeration on small submarines, also, as the inventory of hazardous fluids on board naval submarines is starting to get scary.

Older refrigeration texts have detailed information on this cycle and its implementation; modern texts mention it only as a thermodynamic curiosity. I found the following on The Internet Archive: http://www.archive.org/details/icemakingmachine00ledorich . It's a translation of a text by Ledoux specializing in this kind of machine à froid.

For your purpose, it makes sense because it requires only simple, off-the-shelf hardware. Two compressors (I was going to use two truck air-brake compressors, with the different expansion ratios catered for by altering valve timing), a heat exchanger (air to seawater, in my fishing boat application; a hopper of cold water for a backyard demo) and some pipe. Pressure level is about 200 psi and the amount of air held at that pressure at any one time is kept very small, for safety.

Now I'm working on a manual cooler, driven by a hand-pump with a built-in expander, for a small cheese-making vat. That is proving difficult as at least two stages of compression are needed to balance the handle strokes and make the peak force low enough for somebody other than Ahnold to operate the thing.

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#14

Re: DIY Refrigeration

09/27/2010 1:29 AM

Hi, what are you trying to demonstrate. Is it a simple practical?

Are you demonstrating the refrigeration cycle for practicals?

Wrt the Einstein Refrigeration, are you talking about the Einsten-Szilard Device? I came across the patent. The device was never commercialized. I believe that it did work. Scientific American ran an article on this a few years back. Not sure why the unit never took off commercially. I believe the invention came from Leo Szilard. The motive of this invention was to improve on the safety of the designs at the time.

Why use an old, small refrigerator? That's what I have done. Similar Application.

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#15

Re: DIY Refrigeration

09/27/2010 10:21 AM

If you wish to keep it simple, than keep it small.

-You can use the ammonia adsorption system; the good news is almost no moving parts other than the thermostat. They can last for a very long time. The bad news is the toxicity of the working fluid, and the skills required to assemble it.

-The electronic peltier method is simple, but has very limited capacity.

-The common mechanical refrigeration is just that; very common. There are lots of new, used and discarded parts out there. Also there is enough equipment and information out there that you could use as a template for your own design. Other than knowledge all you need is the technical skills required for the assembly.

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#18

Re: DIY Refrigeration

12/01/2010 10:12 AM

Hello servant74,

Our work began with "Ammonia" and Einsteins use of it in absorption refrigeration.

Changing from Ammonia to Co2 in the Das Valve provides massive cooling (Dry-Ice up) at point of exhaust, and the simpliest way of cold gas return is by venturi.

Placing a cabinet above the exhaust and venturying the not quite as cold gas back into the system shall provide the chiller you seek.

The DaS valve is made entirely using metal water pipe and tennis balls, however low pressure systems may use plastic piping.

Cheers

Peter

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