an interesting article on absorption chillers

[mobile_bob]

Thanks Mark for your comments, here are my concerns or rather questions

i don't see how or rather why you would need more ammonia in a salt/ammonia system than you would with a water/ammonia system
it is the return of the ammonia to the absorption material that sets the amount of btu's of the system?

i would concur that combusting the ammonia might not be a good idea, however i have reference to a diesel engine being fueled with ammonia,  but,, i see no reason to use it as a fuel, and would take precautions to keep any leaks from being ingested.

water transfer of the cold seems like a more than reasonable approach for air conditioning, but not sure how effective it would be for
refrigeration much less a freezer application, perhaps you can address that one for me?

as for certification for its use, i figured it most appropriate to hire someone such as yourself to charge the system, not at all sure i would
want to mess with that.

as for a water based system driven by exhaust heat of an engine, that i have issues with, in that water once the ammonia is driven off
if continued to be heated will pressurize the system to dangerous levels, however
a salt based system will just run as hot as the exhaust after the ammonia is driven off without further pressurization, as far as i can tell
that seems to be a safer system. All i would have to have is a thermostatically controlled exhaust diverter to allow the exhaust to bypass
the absorption unit so that the refrigeration cycle could begin, and then divert back again when the cycle is complete with the ammonia all being reabsorbed by the salt.

maybe i am missing something here? which is likely i certainly am no expert on absorption chillers or cooling.

go ahead and write up your plan, and we will see what we can do to get it posted here on the board

thanks
bob g

[Mark]

Hi Bob,

I was assuming that you would be cooling a medium to store the cold and slowly release and not use the ammonia to slowly feed back to the absorbant.

For refrigeration in its easiest form one could make ice to release over a period that could be monitored for the next firing needed.  If your condenser coil is liquid cooled as well as the absorbant then your complete cycle time wouldnt be much slower than a pump system.

Your concern about the overpressure of water is over come by using a medium to transfer heat as in the design of the Faraday systems of the 1930's.  They used Trichloromonofluoromethane for the heat transfer and not direct heating of any absorbant directly.

The addition of Hydrogen to the system will also drop total system pressure to work at or below 200 PSI, which is about 250 PSI lower than our current R134a systems.  See Electrolux air cooled systems of 1935.

I feel that the system could be moved outside of the building structure, affording a higher level of safety.  Less refrigerant in a recirculatory system with an absorbant medium would put the cold in place for storage with a safer compound rather than large amounts of ammonia sitting in suspension over the cold box suspended in hydrogen or pooled up in the freezer box.

I would also consider, would a valid company come to your house to fill a homemade unit with a potentially deadly gas.  Are you going to pull the permits on this system?  Have it engineered?  Inspectors check system?  Install required "safety items"?  Subject to annual inspections?  Install fire code compliant items?  BATFE inspections?  Keep product records?  Aquire zoning rulings?

Maybe these wont be an issue in the Midwest but in Washington these are!  As owner of a repair service would you allow for the liability of charging a homemade system with any type of .... that could be life threatening?  Would an insurance company cover such an action?  I would be the one who would hate to find out first hand!

On a positive note I think your system has alot of potential and would work favorably.  I look forward to your final system.  I have always liked hvac systems and have alot of reference material on hand and would be honored to help with any system you move forward with.

  I think that their could be safer ways of skinning this cat.  I would like to be able to say that I atleast pointed out some options.  I know you have the skill to design a sound system, but in an open forum, I'd hate to see someone not qualified get hurt. 

Just looking out for you, Mark

[mobile_bob]

first of all i would not build such a system to be placed within a dwelling that was habitated by man or beast
however i would have no such problem placing it in a detached engine room.

my thinking was a refrigerator or bulk freezer compartment above the engine drive, basically for bulk cold storage
of food, or even for makeing ice for other uses elsewhere.

as for homebuilt, i have little doubt that one could build to as high a standard as any commercial product, and could
certainly pressure test to whatever level one saw fit.

and for the right amount of money i can find just about anyone that will do just about anything, so getting the unit charged
buy a refer guy is not likely to be a problem.

then there is this, ammonia is but one absorption refrigerant, there ought to be other compounds that could be used in a heat driven
system?  seems like i have read of others. Even if not as efficient if the heat source is a waste product anyway, why not use a less
efficient compound?

i don't know if i would ever build such a system, but there is a certain appeal to useing the waste heat for something productive
and i cannot think of a better use for it, at least after making domestic hot water or space heating. of course in the summer the need
for one is less and none for the other, but ice is nice at that time of year.

as you know i already have the sanden compressor and it will be used to drive the refer box via a cold plate, so my need for an absorption
system would be more of an experiment rather than i have to have it to function.

Good points though, thanks for the input

bob g

[Mark]

Bob,

One of the interresting ice box conversions upon the introduction of freon type systems was the Calcium Chloride [CaCl] ice systems.  The absorption drive was put in place outside the house structure in a small housing.  Most access doors for ice boxes were designed for north wall of structure.  The Calcium Chloride was cooled to below freezing [melt point at 0 degree F] and pumped through a cooling plate inside the ice box door.  This sytem allowed the direct use inside the structure without any of the ammonia entering the dwelling.  Safe but effective.

Mark

[Dail R H]

   Some good info ----------- Crosbey Ice Ball