YARQT (yet another refrigeration question thread)

[HomeBrewerDude]

Is an empty refrigerator require more/less/or same amount of energy to maintain a temperature than a frig full of beer?

my dad and I had were discussing this... i say it takes more energy to keep a full frig cold than an empty frig.

And just to be clear. I am talking about energy required for maintaining a temperature, not the initial cooling down period.

 

[CTho9305]

An empty fridge and a full fridge are the same once the contents have cooled. all that matters is how much energy gets through the fridge's insulation into the inside, raising the temperature.

HOWEVER... when I think about it more, i think that the full fridge will be running less frequently for longer periods whereas the empty one will run frequently for short periods of time.

when the full fridge exceeds the threshold temperature (it will take longer, since the food has the ability to store some heat), it will take more work to cool it back down (pull the heat back out of the food). with the empty fridge, there is no "inertia" for the temperature - it is easy to raise (as heat comes in) and easy to cool the air again. Over time they should end up using the same amount of energy though.

 

[MajesticMoose]

The full fridge requires less energy once it has cooled all of it's contents. Liquids and solids accept temperature far less readily than air does, so they don't warm up quite as readily as the air in the empty fridge

 

[Woodie]

Da mooseman is correct. Full fridge maintains its temperature better. (BTW, same is true for a thermos: a half-full thermos of coffee will cool much quicker than a full thermos.)

In any case, a fridge full of beer is obviously the preferred situation.

 

[CTho9305]

I still disagree. Think about when you need to spend energy. Heat energy comes into the fridge through the walls/etc at a rate that is UNRELATED to what is inside it, right? Its not like the walls get thicker when you put food in. So, the fridge gains energy at some rate. If you have food in there, it will gain energy at the same rate, but the temperature might not rise as fast. However, once it has reached whatever temperature is requiered to turn the fridge compressor back on, it will take longer to cool back down.

As I said before, if you open the door, the air gets to room temperature, so the food will help cool it down faster, but the overall energy spent should still be the same for an empty and full fridge.

 

[Electric Amish]

Originally posted by: CTho9305
I still disagree. Think about when you need to spend energy. Heat energy comes into the fridge through the walls/etc at a rate that is UNRELATED to what is inside it, right? Its not like the walls get thicker when you put food in. So, the fridge gains energy at some rate. If you have food in there, it will gain energy at the same rate, but the temperature might not rise as fast. However, once it has reached whatever temperature is requiered to turn the fridge compressor back on, it will take longer to cool back down.

As I said before, if you open the door, the air gets to room temperature, so the food will help cool it down faster, but the overall energy spent should still be the same for an empty and full fridge.

I disagree with your disagreement....

When the fridge has matter in it and that matter is cooled to the temp of the fridge it will take more energy to raise the temperature to a point where the compressor needs to turn on again because there is more cold matter in the fridge to absorb the energy.

amish

 

[amnesiac]

Ask anyone who deals in refridgerators and they will tell you that if you leave a fridge unattended for a long time, it's best to keep it full with a few gallon water jugs, because they are retain the temperature much longer than air.

It's simple physics and if you want to disagree, do this - leave the fridge completely empty for a month. Then, fill it with stuff for a month. Compare the energy bill. I'm right, you're wrong.

 

[CTho9305]

The only benefit I see to having stuff in the fridge is to make the compressor run for longer periods, then have longer breaks than with an empty fridge, thus reducing wear and tear.

 

[notfred]

A full fridge will heat up slower, as everyone has said. However, it'll also cool down slower when the compressor does eventually come back on, making the overall amount of energy used the same.

 

[kylebisme]

i compleatly agree with notfred.

btw, amnesiac 2.0, the reason you put jugs of wated in isnt to save power its to keep it working the way it is inteneded too. as CTho9305 said, empty the frige will run in many short cycles, that is not what it was designed to do and is hard on the equpment.

 

[Shalmanese]

Both the fridges will consume (approximately) the same amount of energy. Energy can only be transferred via 3 different methods:

1. Conduction: Proportional to the temperature differential which is the same for both fridges
2. Convection: Same deal
3. Radiation: it is possible that water/alcohol is a better absorber or emmitter or radiation that air but I am willing to bet that this will consume a negligible amount of electricity.

Pardoxically, even though the fridge full of beer is COLDER, it looses MORE energy that the empty fridge when allowed to cool down. The fridge is colder not because it is loosing energy slower, but because there is more mass so the temperature drop for a given amount of energy is less. Heat transfer is proportional to temperature differential. If a fridge has twice the temp differential from its surroundings, it will loose energy twice as fast, however, if it also has twice as much mass (if the same material), it will loose temperature at exactly the same rate as the warmer, lighter fridge. Since the fridge full of beer is COLDER than the empty fridge, it will loose more ENERGY.

 

[Mattnum25]

the answer is trivial: the refrigerator full of beer will require more energy to keep cool, because CTho will keep raiding the damned thing. Seriously though, the empty fridge WILL use more energy from the utility company, due to the shorter on-off cycling as the air changes temperature more rapidly and then cools more rapidly - as opposed to long on-off clycles with the full fridge, longer cycles being of course more efficient. It will, however, REMOVE the same total amount of heat energy in a month either way, as this is a function of the fridge itself and its surroundings, and is independent of the unit's contents...although if you wanted to get really technical, this assumes the fridge is in a large enough room with enough airflow that time for the air around the coils to cool down is irrelevant...frankly, those calculations aren't worth my time, so I'm sticking by my guns on my first explanation. =o)

--edited for clarity and parallelism--

 

[olds]

Mattnum25 = ?
MATTHEW:25
01 Then shall the kingdom of heaven be likened unto ten
virgins, which took their lamps, and went forth to meet the
bridegroom.

 

[CTho9305]

Originally posted by: oldsmoboat
Mattnum25 = ?
MATTHEW:25
01 Then shall the kingdom of heaven be likened unto ten
virgins, which took their lamps, and went forth to meet the
bridegroom.

mattnum25 is his name because everything good was taken on AOL Instant Messenger

He does make a good point about the extra energy usage beyond wear and tear involved in starting and stopping the compressor, but the way I understand it, the question originally was worded in a way such that those kinds of variables could be disregarded '\-

 

[Cyberian]

In any case, a fridge full of beer is obviously the preferred situation.

Obviously!!

 

[FrustratedUser]

Since an empty fridge is empty you can turn it off ----> uses less energy.

 

[Mattnum25]

Originally posted by: oldsmoboat
Mattnum25 = ?
MATTHEW:25
01 Then shall the kingdom of heaven be likened unto ten
virgins, which took their lamps, and went forth to meet the
bridegroom.

lol, that makes a way more interesting explanation then the truth, which is what ctho gave you...although it's actually from way back when I was forced to use AOL as an ISP due to lack of local numbers in my area for anyone else...I haven't seen reason to change the AIM name even though I haven't made use of AOL as an ISP in years (thankfully).

 

[HomeBrewerDude]

Thank you for all the replies!

Its been a while since i first posted the thread and there is considerably less beer in the 'hypothetical' full fridge.

I will let my dad know the consensus seems to be that the empty fridge will be less efficient because it uses more energy (electricity) to remove the same amount of heat.

Thanks and CHEERS!

 

[jiffylube1024]

Originally posted by: FrustratedUser
Since an empty fridge is empty you can turn it off ----> uses less energy.

LOL. Smart reply too!