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Old 10-08-2014, 06:26 PM   #161
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Quote:
Originally Posted by cpaharley2008 View Post
Something does not add up here, a compressor refrigerator is like a heat pump, it cools by pumping the hot air out of the box. As anyone knows, heat pumps are ideal in temperate zones, but poor performers in cold and extreme heat. So explain why a compressor refrigerator will work more efficiently/effectively in -0- weather as well as 100 degree weather than the absorption unit?
The heat exchange does suffer in both scenarios in both units does it not? Basic physics here. So why would one out perform the other?
Jim, I' don't encounter the zero degree scenario like you do, so I can't speak to that. But I am basing my opinion on experience. This July it got up to 105 degrees in my garage, and yet my little compressor based fridge almost froze the beer.

I suppose it isn't that the technology of compressor based fridges is better at heat exchange than absorption is, but that the design of the currently available absorption based fridges is not as robust as their older counterparts. Jon mentioned a 1953 absorption fridge that's still going strong, and I've heard other reports along the same lines.

We may just be dealing with an inferior product, not an inferior concept.
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Old 10-08-2014, 06:29 PM   #162
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Originally Posted by cpaharley2008 View Post
Something does not add up here, a compressor refrigerator is like a heat pump, it cools by pumping the hot air out of the box. As anyone knows, heat pumps are ideal in temperate zones, but poor performers in cold and extreme heat. So explain why a compressor refrigerator will work more efficiently/effectively in -0- weather as well as 100 degree weather than the absorption unit?
The heat exchange does suffer in both scenarios in both units does it not? Basic physics here. So why would one out perform the other?
I think it is simply that compressor driven heat pumps are much more efficient than absorption type; they apply much more energy to the process and run the process much faster transferring heat at a much higher rate.
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Old 10-08-2014, 06:31 PM   #163
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So, remember what this thread was about? I kicked it off, suggesting that people call Dometic with their concerns. Has anyone else done so? I've called three times, and to my surprise I got an email from them a couple of days ago asking about my initial warranty claim (which I also suggest current owners to consider). I'll keep you posted.
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Old 10-08-2014, 06:35 PM   #164
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Originally Posted by cpaharley2008 View Post
Something does not add up here, a compressor refrigerator is like a heat pump, it cools by pumping the hot air out of the box. As anyone knows, heat pumps are ideal in temperate zones, but poor performers in cold and extreme heat. So explain why a compressor refrigerator will work more efficiently/effectively in -0- weather as well as 100 degree weather than the absorption unit?
The heat exchange does suffer in both scenarios in both units does it not? Basic physics here. So why would one out perform the other?
Different refrigerants. Compressor versions can exchange more heat due to pressurization/differential than ammonia versions.
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Old 10-08-2014, 08:42 PM   #165
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, a compressor refrigerator is like a heat pump, it cools by pumping the hot air out of the box.
No, it removes heat from the air. The air stays in the fridge

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Old 10-08-2014, 08:56 PM   #166
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So explain why a compressor refrigerator will work more efficiently/effectively in -0- weather as well as 100 degree weather than the absorption unit?
The heat exchange does suffer in both scenarios in both units does it not? Basic physics here. So why would one out perform the other?
The temperatures at which each cycle can work are limited by the characteristics of the refrigerants, and by the physical process occurring the cycle (absorption versus a phase change of a Freon-like refrigerant), which are different.

In addition, while both systems are challenged by high ambient temperatures, the refrigerant in a compressor-equipped refrigerator is pumped around by the compressor, while the refrigerant in an absorption-based RV refrigerator is moved by another heat-based cycle involving hydrogen (or helium) gas. The absorption unit's pumping action is limited by the temperatures at various points in the cycle, but the compressor works regardless of temperature.

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Mr Escape Artist pointed to residential usage ammonia refrigerators by the Amish. They brand they used to use was Servel, but Lehman Brothers has several other brands. Ammonia refrigeration is not just used in small scale, rv's and residential, it is used in large scale commercial food storage and processing, along with massive concrete construction.
I don't know about the domestic units used by the Amish, but commercial-scale ammonia refrigeration is not quite the same as the system used in an RV appliance. We have an extra circulating gas (that hydrogen or helium) which drives the cycle without needing a motor (done to avoid any need for electrical power), but commercial units normally use an electrically-driven pump.

Also, I don't think that many Amish communities are located in areas where very hot weather is common.
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Old 10-08-2014, 09:11 PM   #167
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When I explained the thermodynamics of cooling/heating to my dad, once I explained the heat was removed from his beer in the fridge and expelled out the coils in the back, his initial comment was "So I really need to keep the back clean!"
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Old 10-08-2014, 09:42 PM   #168
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Originally Posted by Brian B-P View Post
The temperatures at which each cycle can work are limited by the characteristics of the refrigerants, and by the physical process occurring the cycle (absorption versus a phase change of a Freon-like refrigerant), which are different.

In addition, while both systems are challenged by high ambient temperatures, the refrigerant in a compressor-equipped refrigerator is pumped around by the compressor, while the refrigerant in an absorption-based RV refrigerator is moved by another heat-based cycle involving hydrogen (or helium) gas. The absorption unit's pumping action is limited by the temperatures at various points in the cycle, but the compressor works regardless of temperature.


I don't know about the domestic units used by the Amish, but commercial-scale ammonia refrigeration is not quite the same as the system used in an RV appliance. We have an extra circulating gas (that hydrogen or helium) which drives the cycle without needing a motor (done to avoid any need for electrical power), but commercial units normally use an electrically-driven pump.

Also, I don't think that many Amish communities are located in areas where very hot weather is common.


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Old 10-08-2014, 09:53 PM   #169
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Lets get back to the OP's original suggestion that we call Dometic to voice our concerns over the performance of their 8XXX series fridges. I did, have you?
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Old 10-08-2014, 09:59 PM   #170
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Lets get back to the OP's ogional suggestion that we call Dometic to voice our concerns over the performance of their 8XXX series fridges. I did, have you?
You are correct KountryK mea culpa to the OP for adding to thread derailment.

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