Wood fired boiler to power air conditioner/chiller

[sawdust]

Electromech, question for you. Pressure being equal on all sides of a vessel, what is to allow the cold return line to flow? The pressure on both sides of the evaporation restriction would be the same, no?

When I get home I have some good links. I really like this discussion thank you. I would like to see a pumped system with a wind turbine and use propane as the refrigerant.

Somewhere on the forum there was a discussion along these line and a reference to the movie Mosquito Coast.

[pyrocasto]

Electromech, welcome to the forum and what an interesting topic you decided to revive. I've wanted to build an absorption cooler running off solar or wood for many years, just never found the DIY examples to do it.

I will do it one day. :D One day.

[electromech]

     Sorry about the late reply.
     After I had posted I noticed the original post dates were 2005.  Sorry to hear that Buzz isn't around anymore.  A real loss when the experienced are gone.
   
      Sawdust: Response to pressure -  That pipe coming out of the top of the cold chamber probably shouldn't be there. I'd been looking at an ammonia setup before making that figure.  This thing would have to be more of a forced pressure setup. 
      The whole idea is to convert heat from a boiler to cold using heat(cold) of evaporation in a closed system without having to use CFCs so anyone can make one.  Wishing I had tools,time and finances to do some real experimentation.  Propane as you suggest (though explosive when mixed with oxygen) may be the best bet. (the stuff is even manufactured with odor thrown in for leak detection)

[electromech]

     I found a commercial site that has some kind of lithium bromide cooler that runs off of waste heat.
     No clue what the cost is or if they would even sell it to just anyone.  Has a nice illustration of how the thing works.

http://www.yazakienergy.com/waterfired.htm

    Maybe the best thing to do would be to just use the heat from a good wood gassifier to either generate steam or cook wood to make charcoal and woodgas (mostly CO) to power an engine hooked up to an alternator/inverter.  Then use the electric from that to power a regular air conditioner or refrigerator.
   Tough call. Any way you go it gets challenging.

[pitotshock]

Interesting old thread that was dug up here. I have toyed with the idea of a wood fired absorbtion cycle, but I think the problem with the standard outdoor wood furnace is that it doesn't maintain a water temperature high enough to sufficiently drive the ammonia out of solution from the water. Those RV fridges use propane/NG flame or electrical heating element to heat the boiler directly and drive the cycle.

Theoretically, whether you use propane or wood to heat the cycle it wouldn't matter, but directly firing the boiler with a wood fire would be a dirty business compared to the clean propane flame. Cycling off the wood flame when the fridge is cold enough is a bit trickier though.

I see DIY construction of an absorption cycle would involve using stainless steel tubing, vessels and pressure gauges as well as ammonia, hydrogen gas and distilled water: tinkering around with chemical quantities and pressures until something gets going in the right direction, probably outside so you don't gas yourself with the ammonia.
As for basing this on a commercial design, they seem to be open with the generic cycle info, but pretty tight on real information on chemical volumes, operating pressures, temperatures and flow rates. Typical way to define a thermodynamic cycle is to determine your operating temperatures required at the absorber, chiller and boiler. Then from your required rate of cooling (i.e. how many "tons" your unit needs) size the flow rates to achieve that cooling. Absorption cooling is a bit more complicated than a standard refridgeration cycle as there are chemical reactions occuring rather than just liquid/gas phase changes.

Payoff would be good for a backwoods cabin - having a woodstove going means the fridge is cooling with no moving parts. Kinda neat.

Have to dig deep into my brain for those university thermodynamics courses, ouch!