Absorbtion fridge tinkering

[no one that you know]

I have this old absorbtion fridge from a wrecked truck camper that I
salvaged.
I have not looked yet as to how many btu's it needs to get the proper
boiling point. The fridge works perfect on 120 vac but something is
wrong with the propane side it gets way too cold. When it is sitting in
the direct sun + 25 c it can go as low as minus 30 c inside on propane.
I am pretty sure that is easy to fix (gas valve common problem that
model Dometic) but I dont care about fixing it.
Just making a point that the boiler and ammonia process are working.

My thoughts were to make some sort of exchanger on my wood stove and
pass the heat through the boiler area as a back up fridge just for a fun
project.
I dont need a reliable back up fridge just want some fun here.
The winter months are here and I want bragging rights that my wood stove
is cooling my beer and making ice and keeping my house warm.
about 2 or three weeks from now my stove will be running 24/7 for the
next 6 months.
Anyone heard of this before and NO don't tell me about the icey ball.
Looking for ideas how to transfer and regulate the right amount of heat
to the ammonia boiler. What temp does ammonia boil at?
Is this even possible.
I am kinda hopeing to build some sort of tubbing that would sit on top
of the stove with gravity as a first option. A pump and stats plus some
sort of blow off protection will be considered as well.

 

[Arnold Walker]

I have this old absorbtion fridge from a wrecked truck camper that I
salvaged.
I have not looked yet as to how many btu's it needs to get the proper
boiling point. The fridge works perfect on 120 vac but something is
wrong with the propane side it gets way too cold. When it is sitting in
the direct sun + 25 c it can go as low as minus 30 c inside on propane.
I am pretty sure that is easy to fix (gas valve common problem that
model Dometic) but I dont care about fixing it.
Just making a point that the boiler and ammonia process are working.

My thoughts were to make some sort of exchanger on my wood stove and
pass the heat through the boiler area as a back up fridge just for a fun
project.
I dont need a reliable back up fridge just want some fun here.
The winter months are here and I want bragging rights that my wood stove
is cooling my beer and making ice and keeping my house warm.
about 2 or three weeks from now my stove will be running 24/7 for the
next 6 months.
Anyone heard of this before and NO don't tell me about the icey ball.
Looking for ideas how to transfer and regulate the right amount of heat
to the ammonia boiler. What temp does ammonia boil at?

Having to run by memory off the top of my head.
-28F@0psi.
0F@16psi
32@48psi
60F@93psi
100F@197psi

all for pure ammonia.....temperture on boiling point will rise as you add
water.
Icehouses in times past did just that on whatever fuel was
available.....would not be
surprised if someone used a wood/coal fired boiler. Since many did heat with
steam
instead of a direct flame.(Some of them could cool down to -60F.)

 

[daestrom]

I have this old absorbtion fridge from a wrecked truck camper that I
salvaged.
I have not looked yet as to how many btu's it needs to get the proper
boiling point. The fridge works perfect on 120 vac but something is
wrong with the propane side it gets way too cold. When it is sitting in
the direct sun + 25 c it can go as low as minus 30 c inside on propane.
I am pretty sure that is easy to fix (gas valve common problem that
model Dometic) but I dont care about fixing it.
Just making a point that the boiler and ammonia process are working.

My thoughts were to make some sort of exchanger on my wood stove and
pass the heat through the boiler area as a back up fridge just for a fun
project.
I dont need a reliable back up fridge just want some fun here.
The winter months are here and I want bragging rights that my wood stove
is cooling my beer and making ice and keeping my house warm.
about 2 or three weeks from now my stove will be running 24/7 for the
next 6 months.
Anyone heard of this before and NO don't tell me about the icey ball.
Looking for ideas how to transfer and regulate the right amount of heat
to the ammonia boiler. What temp does ammonia boil at?
Is this even possible.

If it's an old propane RV fridge, it doesn't have pure ammonia inside. It's
a mix of ammonia, water, and hydrogen gas. These things have to be level to
allow the right circulation in the tubing.

The 'boiler' side has to get pretty hot, more than 212 IIRC. So circulating
something between the wood stove and the fridge's boiler may take some
doing.

As far as it getting too cold, the propane burners usually have some sort of
thermostat valve that turns off the gas when it gets cold enough, leaving
just a pilot. Maybe that thermostat/valve is foobar. It would most likely
be different than the electric.

Good Luck,

daestrom

 

[no one that you know]

If it's an old propane RV fridge, it doesn't have pure ammonia inside. It's
a mix of ammonia, water, and hydrogen gas. These things have to be level to
allow the right circulation in the tubing.

That is what is inside and they still use this mix on todays RV fridges.
Yes of course it is level and so is my wood stove.

The 'boiler' side has to get pretty hot, more than 212 IIRC. So circulating
something between the wood stove and the fridge's boiler may take some
doing.

So I am looking at steam (212 is boiling point) collected heat at the
stove and then condensated at the fridge boiler....sounds scary.
Not sure but I thought the boiler in the fridge caused the 3 gases to
seperate??? One would think that at the high presures that these get up
too that maybe the ammonia boils first at less than 212 (we dont want
steam inside the tubing of the fridge right) creating the flow bringing
the hydrogen up with it then seperated. The hydrogen being lighter goes
through the evaporater by itself collecting heat....I think but am not
sure that the water is just to help remix the ammonia and hydrogen
before the next boiling process.

As far as it getting too cold, the propane burners usually have some sort of
thermostat valve that turns off the gas when it gets cold enough, leaving
just a pilot. Maybe that thermostat/valve is foobar. It would most likely
be different than the electric.

Yes I know the gas valve has a problem....looked it up and was common on
this model. It just needs cleaning out the propane gunk....propane is a
nice clean burning fuel but the stink they add to it for saftey does
gunk up regulaters and such. I have no intention of fixing it.....I got
the fridge for free.......I am just wonering what temps the boiler gets
up too under the insulation. The sticker say the heater draws 1.2 amps @
120 vac and the input BTU is 1000.
So what I need to do is draw 1000 btu from my wood stove and put that
heat
in the same place where the elctric heater is now.
That part I understand but I have no concept of how to grab and move
1000 btu from my stove to the fridge in the right place....lets say I
use water with an open system (for saftey and a little humidity in the
house)
How many gallon's litres or whatever of water do I have to move per
minute to simulate the 1000 btu heater?

 

[daestrom]

That is what is inside and they still use this mix on todays RV fridges.
Yes of course it is level and so is my wood stove.

So I am looking at steam (212 is boiling point) collected heat at the
stove and then condensated at the fridge boiler....sounds scary.
Not sure but I thought the boiler in the fridge caused the 3 gases to
seperate??? One would think that at the high presures that these get up
too that maybe the ammonia boils first at less than 212 (we dont want
steam inside the tubing of the fridge right) creating the flow bringing
the hydrogen up with it then seperated. The hydrogen being lighter goes
through the evaporater by itself collecting heat....I think but am not
sure that the water is just to help remix the ammonia and hydrogen
before the next boiling process.

The 'boiler' is right where the flame/heater is. It heats up the
water/ammonia mixture enough to drive off the ammonia as a gas. This gas
rises and is condensed in the tubing above the 'boiler' on the outside/back
of the unit. The liquid ammonia then runs down the tubing, into the unit
where it mixes with H2 gas (usually there is a small crimp or restriction to
hold back a little liquid ammonia in the condenser). Because of the mixture
with H2 (and Dalton's law of partial pressures), the ammonia now boils
again, absorbing heat from the interior. The ammonia vapor is remixed with
water (the water that came from the boiler and is nearly ammonia-free).
This all happens outside the box in another coil (mixing water with ammonia
gives off heat, and the water must be cooled some so it can absorb the
ammonia). Two coils outside giving off some heat, one coil on the inside
absorbing heat, and one small tube/chamber heated by the flame/heater.

But I think you misunderstood my point about 212F. I think the 'boiler',
right where the flame/heater is has to get quit a bit *hotter* than 212F.
So just atmospheric steam from an open loop may not do the trick. Well, it
may work a little bit, but not as well as it should. For experimenting, you
could try it. Run a simple copper tube from a boiling kettle into the base
of the 'boiler' or 'chimney' where the propane flame is. You'll need
something to collect the condensate as it trips off, or else it'll be messy.

Yes I know the gas valve has a problem....looked it up and was common on
this model. It just needs cleaning out the propane gunk....propane is a
nice clean burning fuel but the stink they add to it for saftey does
gunk up regulaters and such. I have no intention of fixing it.....I got
the fridge for free.......I am just wonering what temps the boiler gets
up too under the insulation. The sticker say the heater draws 1.2 amps @
120 vac and the input BTU is 1000.
So what I need to do is draw 1000 btu from my wood stove and put that
heat
in the same place where the elctric heater is now.
That part I understand but I have no concept of how to grab and move
1000 btu from my stove to the fridge in the right place....lets say I
use water with an open system (for saftey and a little humidity in the
house)
How many gallon's litres or whatever of water do I have to move per
minute to simulate the 1000 btu heater?

You need to look again. 1000 BTU is an amount of energy, not power. It may
say 1000 BTU/hour or something like that. But 120VAC times 1.2 amps is 144
watts and that would be about 491 BTU/hour. That's not an awful lot of
steam. A pint of water (call it 1 lbm) takes about 970 BTU to change from
212F water to 212F steam. So if 212F is *hot* enough for the ammonia/water
mixture to work at all, you would only need about a pint an hour. Figuring
in losses and wasted steam flowing up the 'chimney', call it a quart an
hour. (and for 'ballpark', back-of-the-envelope calculations, that's about
1 litre an hour).

If the 212F steam isn't hot enough, you could run the tubing from the kettle
outlet back and forth once or twice across the wood-stove to superheat the
steam to a higher temperature, still at 0 psi. Insulating the tubing would
reduce losses and prevent burns, but obviously it would have to be some
high-temperature stuff, not foam tubing.

daestrom
P.S. FWIW, the pressure in these things usually runs about 300 psi. So
when they spring a leak, you know it right away. The tubing is steel both
for strength and because ammonia and copper don't like each other very well.

 

[no one that you know]

Why would you want to mess with steam? Would be safer and probably
easier to run an antifreeze solution under pressure so the boiling point
is well above the 212 degrees you need.

Pete C.

The thing of ot is I dont think it needs 212 at the fridge boiler.

 

[no one that you know]

I put a probe in there today.....the temps are near 300 F at the top of
the boiler. No can do I guess (

 

[no one that you know]

I put a probe in there today.....the temps are near 300 F at the top of
the boiler. No can do I guess (

Today I put a probe on my wood stove and it runs near 300 F.
Now I am looking for ideas to use oil or some kind of fluid to transfer
the heat to the fridge boiler.
This will be left unattended so it's gotta be full proof.
I suppose once we get the minus forty and I stuff the stove the temps
will be as high as 5 or 6 hundred at times on the wood stove top.
I am thinking of a cooling system similar to a car cooling system
system. When the coolant (in this case the heated oil)gets to proper
temp a t-stat opens allowing the fluid to flow through a rad probably
downstairs where there is no heat (small circ pump) (two birds with one
stone) This rad would prevent the oil in the coil on top of the stove
from overheating like the rad does in a car to keep the engine at
pre-set temp's. Now to get the proper temp at the boiler I could maybe
use an electrical sensor at the boiler to open and close a valve
allowing some of the heated oil to pass by the boiler tube keeping it at
near 275-300 F.
Come on guys what's at your local hardware store any ideas?