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Old 08-22-2012, 09:38 PM   #61
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Originally Posted by dunnnc

The can at the bottom is the accumulator tank and just stores the liquid ammonia. If the fan is doing it's job, the can should be cool. The ammonia is pulled from the tank and boiled in the stack.
My burner is directly under the can, must be a different design than the larger units. The refrigerator is in a pop up so it's one of the very small units. The top is where the line leads down and seems to be the return. Moving air down there would not be good for the flame and I doubt the ammonia would get hot enough to move up to the top of the tubes to condense and pull the heat out of the refrigerator. It's most likely just designed this way for the compact size.
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Old 08-22-2012, 09:42 PM   #62
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Originally Posted by xf021209 View Post
My burner is directly under the can, must be a different design than the larger units. The refrigerator is in a pop up so it's one of the very small units. The top is where the line leads down and seems to be the return. Moving air down there would not be good for the flame and I doubt the ammonia would get hot enough to move up to the top of the tubes to condense and pull the heat out of the refrigerator. It's most likely just designed this way for the compact size.
How about some pictures? I take it is is not like the diagram or pictures I posted.
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Old 08-22-2012, 10:15 PM   #63
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Quote:
Originally Posted by dunnnc

How about some pictures? I take it is is not like the diagram or pictures I posted.
No it looks much more compact, but has to use a similar principle, and I know it's an ammonia unit. I'd be happy to post pictures except my cousin purchased the pop up from me, and he lives in Ohio. I'm in Texas :-) I've seen the bigger replacement units that look much more like the diagram. After rebuilding the pop up, using it for a few years, and finally selling it, I'm in the process of rebuilding a FR Salem (FEMA Trailer) now. I'm still trying to decide on using a conventional small office style refrigerator (inexpensive, reliable, will need ice blocks during travel time) or going with an RV unit (very expensive, not as reliable, no need for ice blocks!). Since I stay in parks most of the time, I'm leaning towards conventional. I already have a nice black office fridge that would work well. I could pickup a small black freezer for around $200.00. Freeze a couple of milk jugs and cool the fridge before travel. Once at the camp ground, put the milk jugs in the freezer in case there's food left after camping (rarely) for the drive home. I could do similar to what the original question here was - since the condenser is on the back of the fridge, just like with an RC fridge, a small muffin exhaust fan may not be a bad idea to keep the heat from collecting inside the trailer and to cool the fridge faster. One thing that really surprises me is how such a small low cost device improves the efficiency of RV fridges...and why isn't the fan included?
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Old 08-24-2012, 08:30 PM   #64
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Quote:
Originally Posted by dunnnc

The can at the bottom is the accumulator tank and just stores the liquid ammonia. If the fan is doing it's job, the can should be cool. The ammonia is pulled from the tank and boiled in the stack.
When i first jury rigged my fan it was pulling air directly over that tank and was barely warm to the touch...my fridge warmed up overnight and spoiled everything in it. Removed the fan and with in a few hours it cooled back down. I don't understand the thermodynamics of how heating ammonia can cause a cooling effect but I do understand your thoughts on how the fridge works by looking at the drawing. I say you need to be careful with exactly what your cooling back there only from personal experience.
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Old 08-24-2012, 08:48 PM   #65
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Originally Posted by M109Rrider View Post
When i first jury rigged my fan it was pulling air directly over that tank and was barely warm to the touch...my fridge warmed up overnight and spoiled everything in it. Removed the fan and with in a few hours it cooled back down. I don't understand the thermodynamics of how heating ammonia can cause a cooling effect but I do understand your thoughts on how the fridge works by looking at the drawing. I say you need to be careful with exactly what your cooling back there only from personal experience.
All I can say is where my fan is has worked great and the accumulator is always cool and never hot whereas before it was warm/hot to touch before installing the fan. The burner portion is to the right of the accumulator tank on my unit and is completely enclosed.
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Old 08-24-2012, 09:10 PM   #66
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OK. Is the one in this pic (with bar code sticker) a different tank? This isn't my picture but looks similar to mine. I had my fan wedged right above it in the coils when I had problem

P.s. my wife was really pi$$ed when I did that..lol!!

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Old 08-25-2012, 12:29 PM   #67
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Quote:
Originally Posted by M109Rrider View Post
When i first jury rigged my fan it was pulling air directly over that tank and was barely warm to the touch...my fridge warmed up overnight and spoiled everything in it. Removed the fan and with in a few hours it cooled back down. I don't understand the thermodynamics of how heating ammonia can cause a cooling effect but I do understand your thoughts on how the fridge works by looking at the drawing. I say you need to be careful with exactly what your cooling back there only from personal experience.
Yep. You right.

But:
We don't really need to understand the detailed thermodynamics of the
ammonia cycle though. It's pretty clear that the ammonia gas - boiled
from the storage pot - is what produces the cooling effect. Knowing
that, it's easy to understand anything that reduces the amount of
ammonia gas available - like a leak, less heat in the boiler, etc - will
reduce the amount of cooling. Now think about boiling a cold liquid
vs boiling a hot liquid. Clearly more heat input is required for the
former. With a fixed amount of heat available - from propane or
AC - less ammonia will be boiled if the liquid is cool, compared to if
the liquid was hot. Less ammonia gas; less cooling effect.

And the wifey do get POed, finding spoiled food........


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Old 08-25-2012, 01:53 PM   #68
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Originally Posted by dnaraG_1M View Post
...We don't really need to understand the detailed thermodynamics of the
ammonia cycle though...Now think about boiling a cold liquid
vs boiling a hot liquid. Clearly more heat input is required for the
former. With a fixed amount of heat available - from propane or
AC - less ammonia will be boiled if the liquid is cool, compared to if
the liquid was hot. Less ammonia gas; less cooling effect...
Why do the frigs work so much better in cold weather (say 45°)then? The whole outside of the unit is colder and inside the camper is about 72°?

Just asking!
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Old 08-25-2012, 01:56 PM   #69
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Quote:
Originally Posted by dunnnc

Why do the frigs work so much better in cold weather (say 45°)then? The whole outside of the unit is colder and inside the camper is about 72°?

Just asking!
Good question
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Old 08-25-2012, 02:02 PM   #70
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It works on the principle of "Magic"

See link more complicated reason.

Heat of Vaporization - ChemWiki
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