Recycled air refrigerator

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Main Question or Discussion Point

Has anyone heard of any home refrigerator that uses say some sort of duct to flow cold air from the bottom of the compartment back to the top that would otherwise become wasted outside?

I'm aware that commercial refrigerators like those in supermarkets already do this, but are there any vertical refrigerators that make use of this? If not is there any reason why it wouldn't be practical? I would imagine that there would be a huge saving in cooling since the cold air wouldn't just be falling out the bottom especially for those who constantly open the door etc.
 

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  • #2
russ_watters
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There is no cold air outside a refrigerator to be recycled inside. Open commercial refrigerators such as what you see in grocery stores circulate air from top to bottom over an open front face, but the air never leaves the front of the fridge.

Airflow inside a normal refrigerator is self-contained: if the air leaves the refrigerator from the bottom, it is going back to the evaporator, not being ejected to outside.
 
  • #3
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You misunderstand me. When you open the refrigerator door you feel the wave of cold air escaping the fridge. Now instead of letting the cold air become wasted, instead try to capture it again on its way out by some sort of fan mechanism (which will only turn on when the door is opened).

What im trying to do is minimise the cold air wastage when a fridge is opened by convection.
 
  • #4
berkeman
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You misunderstand me. When you open the refrigerator door you feel the wave of cold air escaping the fridge. Now instead of letting the cold air become wasted, instead try to capture it again on its way out by some sort of fan mechanism (which will only turn on when the door is opened).

What im trying to do is minimise the cold air wastage when a fridge is opened by convection.
I misunderstood your question too, but my response was deleted by the PF crash.

A cheaper way to hold the cold air in would be to put clear vertical plastic strips inside the fridge, so even when you opened the door, you would have to reach through the plastic strips to pull things out.
 
  • #5
russ_watters
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You misunderstand me. When you open the refrigerator door you feel the wave of cold air escaping the fridge. Now instead of letting the cold air become wasted, instead try to capture it again on its way out by some sort of fan mechanism (which will only turn on when the door is opened).

What im trying to do is minimise the cold air wastage when a fridge is opened by convection.
Oh, ok. I could see adding some slots at the bottom of the fridge to pull that air back into it, but I'm not sure that would really be all that useful. The amound of "cold" held by the air isn't actually that big of a fraction of the "cold" that is in the fridge. Consider that a gallon of water takes 41 btu to raise its temperature by 5F. But all the air in a fridge (say, 25 cu ft) can be exchanged with room air (35F->70F) and you only lose 16 btu.
 
  • #6
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I could see adding some slots at the bottom of the fridge to pull that air back into it
Yes this was pretty much what I was envisioning.

Consider that a gallon of water takes 41 btu to raise its temperature by 5F. But all the air in a fridge (say, 25 cu ft) can be exchanged with room air (35F->70F) and you only lose 16 btu.

True, a fridge that was full would lose very little since most of the 'cold' would be contained within the food. But most people's fridges aren't completely full at any given time (heck my fridge is 70% airspace there). So frequently opening the fridge door would cause you to lose your 16 btu's each time, I imagine the loss due to radiation of food items would be quite low.

But yeah, i'm not the best with thermodynamics and whatnot (im studying electrical engineering ~ worlds away) so i'm not sure whether the cost of the ducts, fans etc would eventually pay off by saving energy.
 
  • #7
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fridges aren't completely full at any given time (heck my fridge is 70% airspace there)
that is more of a "fix-able waste" than the lost air.
any fridge should be as full as possible while still retaining enough room for the air to move

put milk jugs full of water in it (or even better beer/soda)
the increase in thermal mass would (IMHO) reduce the power usage better than any added fans, vents, and the added control system

dr
 
  • #8
sophiecentaur
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Keep the door closed as much as possible or use a 'chest' style fridge which you access from the top. There's no point in pumping air from the room into the bottom and if you want to just balance the pressure, so cold air doesn't 'fall out', use a physical barrier - like a roller blind, pulled up from the bottom to the level of what you want to access with the door open.
My fridge freezer has a circulation pump which turns off when you open the door to minimise 'cold-loss'.
 
  • #9
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I think that dr dodge has just invented bloke heaven, every time you take some food out of the fridge replace it with beer, every time you buy any food that needs to go into the fridge you have to drink enough beer to make way for it. Anyone who puts this into practice let us know in a month or so exactly how much your divorce cost.
 
  • #10
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my wife drinks beer too

we actually have 3 fridges

1-food
2-beer/soda/wine inside
3-beer/soda/wine outside

highly efficient, less walking for a beer

dr
 

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