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Something that bugs me about refrigerators

 
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I don't know when I realized it, but for a long time now I've been troubled by the design of refrigerators.

So you've basically got a pump for moving heat from inside an insulated box to somewhere outside of it. Pretty simple concept. So why is the motor for this doohickey *underneath* the insulated box, where the heat from its operation will rise up into the insulation? Why are the cooling elements on the back of the box in a specially made closet where they get so little airflow? And why is that done indoors?

My question to you, good Permies, is this:

Why aren't modern refrigerators basically insulated closets? The insulation will last your lifetime. The gaskets might occasionally need replacing. The appearance could perfectly match the interior of your home. If you lived outside of the tropics, you could mount the entire mechanics of it on the outside of the wall, outside the house! Then, for half the year, the only real cost is moving the coolant, and nature takes care of the cooling itself. And if the mechanics break, you just replace them, no need to replace the whole insulated box!

I have to believe this would be much better for the environment, and for energy needs.

So how come I've never seen one like this?
 
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Some common misconceptions about the condensing function of refrigeration systems here, but you're still right. A lot of bars and restaurants place the compressors remotely to displace heat. You are more than less speaking of turning a refrigerator into more of a heat pump. Which I agree. I think domestic multi appliance systems could be used to extract heat and coolness. Practicality of such ideas is not so high. Simplicity goes much further. A refrigerator with vents to the coldness of outdoors is common, fridge closets. Porch fridge. For food safety reasons its not manageable nor the most affordable. Even efficient, and modern units will freeze trying to get the few degrees cooler for safe storage. Try to run an air conditioner in cool weather. It literally freezes. Refrigeration and building cooling is about proper design. The technology is currently at its peak. The efficiency of heating and cooling, is mostly based on reuse and recovery of heat dispersal, and exhausted vapors. Cooling, insulation insulation insulation, and finding a safe and stable coolant which takes the least and appropriate energy per application to compress.
 
chad Christopher
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http://en.m.wikipedia.org/wiki/Absorption_refrigerator
http://en.m.wikipedia.org/wiki/Heat_pump_and_refrigeration_cycle

If you have ever had hot water from a water cooler, that's where it came from.
http://www.industrialcontrolsonline.com/training/online/refrigeration-heat-reclaim

Edit, there are better systems, but not any that run on electric. You can obviously move your compressor and condenser, but that's about it.

http://dollarstorecrafter.blogspot.com/2013/06/turn-old-refrigerator-into-ice-chest.html

One more edit/rant. For instance, you can buy a 98.5% efficient gas furnace. But it doesn't mean shit, if your front door is open.
 
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Not a heat pump, but a split system. If it were a heat pump, it would have a reversing valve and metering devices(fixed orifices or txv's)at both coils. and could cool the insulated space or heat it.

I think William partially described a glycol dry cooler running in "free cooling". While it would be somewhat cheaper to operate, the setup cost of the initial system is what turns many people off and the only real time you get realistic savings is if the outdoor ambient temperature is really cold for a significant duration and your cooling demand is very high. I usually only see systems like this at data facilities in northern climates, and manufacturing facilities that require loads of process cooling.

Refrigerators have the compressor low so all the refrigerant oil entrained in the system can drain back down to the crankcase to keep the moving parts lubricated. There is an added safety benefit of the heaviest components of the refrigerator being mounted low, and the added user benefit of keeping the upper space free for food storage without the cabinet being overly tall. I don't foresee any truly revolutionary remaking of the mechanically cooled icebox unless we radically change the refrigeration process itself.
 
pollinator
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Chad, Morgan

I think I read you that putting a refrig outdoors won't work properly, allowing food temps to get too high. You mentioned freeze up, but I don't think I follow. The cold part of the system would be just the same as always, 35-42F., 0F. freezer. The hot side would be what was "out in the cold" outdoors and it doesn't seem that would suffer a freezing problem. If I understand modern refrigs right the cooling element (evaporator I think?) is in the freezer compartment and thus lives at 0F. or below always. Cooling the "temperate" food storage compartment is done with ducts and fans that run occasionally circulating a little air from the freezer compartment. You're saying the evaporator can get too cold if the condenser works too well? It would seem the evaporator already runs at about -10F., maybe even lower. Even is there is a direct correlation between ambient and evaporator temps, I don't see right off the problem with running an exchanger (evaporator) that normally gets to -10 or below, running it say at a temp of -50F or lower. Unless the coolant doesn't change state properly at those temps. I thought a system would have been designed so it's most basic component, coolant, would function over a very wide range. And that's assuming essentially brain dead control systems, bang-bang, either full or full off.

Plus, most (all?) modern consumer refrigs have auto defrost which would add some heat..

What am I missing here? Curious.

Thanks


Rufus
 
Morgan Barker
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Refrigeration is a balancing act where equipment is designed to operate in a pretty narrow band of conditions. A/C units that need to run during the winter, have extra devices installed to cope with operating in low temperatures. They have a heating band mounted around the body of the compressor to keep the oil warm. the pressure is monitored on the high side with a pressure switch that cycles the condenser fan off to allow head pressure to rise to the optimal level. There is an additional capacitor to hard start the cold compressor. The condenser coil is shrouded from the wind so as to block out that dynamic variable. A refrigerator has none of these because the designers figure they will be set up and run their entire service life between 65-75degF and any additional components would be unnecessary and only raise the unit cost.
One of the most likely scenarios of a fridge running outside in low temperatures is a noticeably shorter compressor life and less cooling capacity. The refrigerant reentering the cold space is too cold and is less likely to fully evaporate. If it isn't fully evaporating, it is unable to absorb heat from the space, hence your warmer fridge.
 
Rufus Laggren
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> set up to run ... between 65-75F....

> extra components...

OK. Makes sense. I thought the existing regulating controls could handle it - iow, didn't know the cycle was so sensitive to ambient temps. It sounds like it's almost uncontrolled (except by the existing environment) and very dependent on its specialized conditions. Thanks for the details.

Rufus
 
Morgan Barker
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Well, refrigerators are simplified to a ridiculous degree BECAUSE their operating environment and cooling load is so predictable and unchanging. Air conditioners have to run in a much broader range of environments and have more complex components to deal with it. Could you hack a fridge to run in low ambient conditions? Sure. But it would take some trial and error and a lot of luck to get it to be happy.
I think the best we could do for improving efficiency is to change from an upright/front access unit to a bunker/chest configuration with top access to keep all that cold air from spilling out when you open it. Maybe clad the outside with a layer of foam board to slow external heat gains from all the non critical sides. And keep the fan and back/bottom coils clean! Those dust bunnies really hinder airflow which raises head pressure which makes the compressor draw more amps.
 
Rufus Laggren
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> improving efficiency... bunker/chest

The relatively newer format w/three stacked drawers looks like easier to deal w/from the functional standpoint. I haven't looked at them close because any "new" idea gets priced high when it comes out - not my territory. But the bottom freezer fridges I've seen have sides and back on the drawer and it acts as a self contained chest that keeps the cold air mostly in even though you pull it out. The drawer cavity does fill w/room air when you pull out the drawer but then the room air gets expelled again when you close it. Not perfect but a big boost in ease of use compared w/digging down _deep_ under piles of food to get what you want on the bottom. When doing that the open time can increase a lot.

Re: working range of environment: Don't the reefers on long haul trailers deal w/a pretty wide range of temps? I suspect they use cold plate systems and I don't know how frequently you could go in/out w/out messing up their design parms. But that might be a source of the systems needed to make a better fridge. Also, most commercial systems (like super markets) are splits, right? Condenser and evaporator some distance apart - the condenser outside on the roof or in the back room, the evaporator in the cold compartment. Those must have some pretty good controls, too.

We were talking standard domestic refrigerators because they're common as dirt. But there are other systems out there in huge quantities that could possibly be repurposed if a person could meld their own usage patterns w/a more or less permanent installation.

Rufus
 
William Bronson
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I am sad now! I was going to bring winter air into a insulated box enclosing the coils on my freezer, but it sounds like that will be counter productive...
 
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William Jack wrote:I don't know when I realized it, but for a long time now I've been troubled by the design of refrigerators.

So you've basically got a pump for moving heat from inside an insulated box to somewhere outside of it. Pretty simple concept. So why is the motor for this doohickey *underneath* the insulated box, where the heat from its operation will rise up into the insulation?




The old refrigerators used to have their compressors at the top. They were called Monitor Top Refrigerators. They blew the vented heat directly out the top, and were mostly used commercially. The older compressors used highly toxic/flammable substances, but were absurdly reliable. Toxic/flammable refrigerant meant that home use waited for nontoxic/nonflammable freon in the 30s. Small bottom-mounted motors with large passive radiators took the noise away from ear level, and made them quiet enough for the home.

Original appliances had cords running to the ceiling to plug into light bulb sockets, since early electrification was only for lighting. Standardized power outlets eventually put electricity at floor level. More about old lighting electrical systems here.
 
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