I keep reading that you should use things like water bottles and
crumpled newspapers to take up space so less air flows in when you open
a refrigerator door.

I calculate that if you changed the air in an empty 17cu ft refrigerator
for air at 75 F with a dew point of 65 F, cooling it to 35 F with a dew
point of 0 F would mean moving 15 joules, or 1 watt for 15 seconds,or
1/240,000 kwh.

There doesn't seem to be any point in using filler to reduce an
occasional air change. How about thermal mass? Water bottles could
reduce cycle times by increasing thermal mass. A compressor draws more
watts early in the cycle, but don't you get that back when the
compressor turns off?

Can filling a refrigerator really save energy?

On Fri, 25 Jul 2014 16:44:02 -0400, J Burns
wrote:

Can filling a refrigerator really save energy?

No. Not if there is no circulation.

Over pack the unit and cold air is ineffective to some degree.

(12 things you never put in a refrigerator...)

On Friday, July 25, 2014 5:00:15 PM UTC-4, Oren wrote:
On Fri, 25 Jul 2014 16:44:02 -0400, J Burns

wrote:



Can filling a refrigerator really save energy?



No. Not if there is no circulation.



Over pack the unit and cold air is ineffective to some degree.



(12 things you never put in a refrigerator...)

Yeah, I think he's poking at windmills. IDK if his calculations are
right, but certainly there isn't a huge amount of energy lost due to
the exchange of room temp air with chilled air. It costs maybe $100
a year to run a modern fridge. Even if you somehow saved 10% in energy,
which I don't think is possible, who's going to screw around with extra
bottles taking up space or newspaper for $10.

As for the cycle times, just let the fridge do what the fridge does.
I don't see changing the number of cycles a bit making any significant
differenc either.

I did put some big containers of water into my freezers prior to
hurricane Sandy. That is a good idea, because it will increase the
time you can go without power. I made it a full week. The basement
freezer was still almost entirely frozen. The kitchen one, stuff had
melted but was still cold, so I refroze about 90% of it. The basement
one, I did put a big bag of additional ice in it twice during the week.
Biggest thing is, don't open the doors at all.

On Friday, July 25, 2014 5:13:35 PM UTC-4, trader_4 wrote:

And who has a fridge that has a lot of air that can pour out anyway?
Mine the bottom half of the fridge section is composed of 3 drawers,
the air in them isn't coming out easily. The top half is crammed full
of plenty of stuff. If anything I need more space, I don't have any
empty space. I would think most fridges are like that, no?

On 7/25/14, 5:13 PM, trader_4 wrote:
On Friday, July 25, 2014 5:00:15 PM UTC-4, Oren wrote:
On Fri, 25 Jul 2014 16:44:02 -0400, J Burns

wrote:



Can filling a refrigerator really save energy?



No. Not if there is no circulation.



Over pack the unit and cold air is ineffective to some degree.




If your leftovers cool too slowly from inadequate circulation, you could
get spoilage or food poisoning, but the refrigerator wouldn't use more
energy.

My old refrigerator used about 108 kwh a month in summer. At that rate,
I figured it didn't make sense to buy a new one, but a neighbor made me
an offer I couldn't refuse. It uses about 35 kwh a month. I've found a
copy of the EPA sticker for this model. It estimated 38 kwh a month, so
my performance is pretty close.

I found Frigidaire's wiring and specs for repairmen. They say the
compressor in this model should use 140-185 watts in the last third of
the cycle. Mine uses 105 including the fans! The duty cycle is about
what Frigidaire specifies, and it keeps the right temperatures, so I
guess the model was improved after it went into production.

I googled and found the DOE report from the early 80s, saying their
prototypes proved refrigerators could be a lot more efficient. I kept
turning up web sites with the familiar advice to keep a refrigerator
packed. The one that recommended crumpled newspapers in the freezer
appeared to be from Canada's equivalent DOE. (In fact, it was probably
an official-looking mindless environmental organization.)

I also ran into a Popular Mechanics article claiming your house will be
cold if your freezer has a bad door seal. Cancel my subscription!


Yeah, I think he's poking at windmills.

"Tilting at windmills" means attacking imaginary enemies. You don't
think there really are people publishing advice to keep a refrigerator
full? (Of course, if you make a habit of keeping lots of food in there
because it's supposed to save energy, you may end up buying a bigger
refrigerator, and food quality suffers from being in there longer.)

J Burns wrote in :


I calculate that if you changed the air in an empty 17cu ft refrigerator
for air at 75 F with a dew point of 65 F, cooling it to 35 F with a dew
point of 0 F would mean moving 15 joules, or 1 watt for 15 seconds,or
1/240,000 kwh.


Check your calcs. They're wrong.

On 7/25/2014 4:44 PM, J Burns wrote:
I keep reading that you should use things like water bottles and
crumpled newspapers to take up space so less air flows in when you open
a refrigerator door.

I calculate that if you changed the air in an empty 17cu ft refrigerator
for air at 75 F with a dew point of 65 F, cooling it to 35 F with a dew
point of 0 F would mean moving 15 joules, or 1 watt for 15 seconds,or
1/240,000 kwh.

There doesn't seem to be any point in using filler to reduce an
occasional air change. How about thermal mass? Water bottles could
reduce cycle times by increasing thermal mass. A compressor draws more
watts early in the cycle, but don't you get that back when the
compressor turns off?

Can filling a refrigerator really save energy?

Doubt it.
The heat capacity of anything you put in is bound to be greater than
air. I think water has over 1,000 times the heat capacity of air.
That means putting things in and cooling them down will probably use
more energy than that gained by the air volume loss.

OTOH, things that you normally cool down before using like bottled water
might best be stored in the refrigerator to take advantage of
maintaining cooling during a power failure.

On Saturday, July 26, 2014 8:26:45 AM UTC-4, Frank wrote:
On 7/25/2014 4:44 PM, J Burns wrote:

I keep reading that you should use things like water bottles and

crumpled newspapers to take up space so less air flows in when you open

a refrigerator door.



I calculate that if you changed the air in an empty 17cu ft refrigerator

for air at 75 F with a dew point of 65 F, cooling it to 35 F with a dew

point of 0 F would mean moving 15 joules, or 1 watt for 15 seconds,or

1/240,000 kwh.



There doesn't seem to be any point in using filler to reduce an

occasional air change. How about thermal mass? Water bottles could

reduce cycle times by increasing thermal mass. A compressor draws more

watts early in the cycle, but don't you get that back when the

compressor turns off?



Can filling a refrigerator really save energy?



Doubt it.

The heat capacity of anything you put in is bound to be greater than

air. I think water has over 1,000 times the heat capacity of air.

That means putting things in and cooling them down will probably use

more energy than that gained by the air volume loss.



The concept is that you only have to cool the water once. The air
you have to cool every time you open the door and the cold air
pours out and room temp air goes in.

On 7/26/2014 8:26 AM, Frank wrote:

Doubt it.
The heat capacity of anything you put in is bound to be greater than
air. I think water has over 1,000 times the heat capacity of air.
That means putting things in and cooling them down will probably use
more energy than that gained by the air volume loss.

OTOH, things that you normally cool down before using like bottled water
might best be stored in the refrigerator to take advantage of
maintaining cooling during a power failure.

You have a valid point about stuffing for the sake of stuffing, but if
you have a case of juice or beer, better to put it in to fill the space
rather than put a bottle at a time. You'll be using the same amount of
energy to get it down to temperature anyway, but get less air loss each
time the door is opened.

On Saturday, July 26, 2014 9:46:03 AM UTC-4, Ed Pawlowski wrote:
On 7/26/2014 8:26 AM, Frank wrote:



Doubt it.

The heat capacity of anything you put in is bound to be greater than

air. I think water has over 1,000 times the heat capacity of air.

That means putting things in and cooling them down will probably use

more energy than that gained by the air volume loss.



OTOH, things that you normally cool down before using like bottled water

might best be stored in the refrigerator to take advantage of

maintaining cooling during a power failure.



You have a valid point about stuffing for the sake of stuffing, but if

you have a case of juice or beer, better to put it in to fill the space

rather than put a bottle at a time. You'll be using the same amount of

energy to get it down to temperature anyway, but get less air loss each

time the door is opened.

Even if it's not something that you need to cool anyway, once it's cooled
it can stay cooled for years. The air that would be there instead can
get changed out for warm air every time the door is open. Not that I
think it's worth worrying about. My fridge uses less than $100 a year
in electricity. I can't imagine this fussing around saving more than
a couple bucks a year, it's just not worth it. And who has free space
in their fridge to begin with? I don't have to add anything, it's
already full.

On 7/26/14, 7:58 AM, Zaky Waky wrote:
J Burns wrote in :


I calculate that if you changed the air in an empty 17cu ft refrigerator
for air at 75 F with a dew point of 65 F, cooling it to 35 F with a dew
point of 0 F would mean moving 15 joules, or 1 watt for 15 seconds,or
1/240,000 kwh.


Check your calcs. They're wrong.

I was seeing if you were awake. Why don't you tell the class the correct
answer?

On 7/26/2014 9:46 AM, Ed Pawlowski wrote:
On 7/26/2014 8:26 AM, Frank wrote:

Doubt it.
The heat capacity of anything you put in is bound to be greater than
air. I think water has over 1,000 times the heat capacity of air.
That means putting things in and cooling them down will probably use
more energy than that gained by the air volume loss.

OTOH, things that you normally cool down before using like bottled water
might best be stored in the refrigerator to take advantage of
maintaining cooling during a power failure.

You have a valid point about stuffing for the sake of stuffing, but if
you have a case of juice or beer, better to put it in to fill the space
rather than put a bottle at a time. You'll be using the same amount of
energy to get it down to temperature anyway, but get less air loss each
time the door is opened.


I've used this excuse when the wife asks me, "Why is there so much beer
in the refrigerator?"

Stuff refrigerator with breaded mix, and
bake at 350 for an hour and a half. Baste
refrigerator lightly with butter butter and
oil, and serve when golden brown.

Serves four to six.

--
..
Christopher A. Young
Learn about Jesus
www.lds.org
..

Well, I think it's true that the more cold air that spills out of an open refrigerator, the more warm air comes in to replace it, and you pay to cool that warm air.

But, even though I haven't read every post in this thread, something I haven't seen mentioned is the word "momentum" and any reference to the driving force that would cause that air to gain momentum and spill out of the fridge.

Air is actually a lot heavier and denser than most of us realize. It's only because our bodies are also pressurized to the same pressure that surrounds us that we don't feel the force of the air pressure acting on us. In fact, for most of recorded history, people believe air didn't weigh anything at all. In fact, it's both the mass of the air and the tiny density difference between warm air and cold air that determines the rate at which cold air would spill out of a fridge. The calculation at the beginning of this thread presume ALL of the cold air spills out to be replaced by warm air each time the fridge door is opened and I don't believe that to be true. In order for air to spill out of an open fridge, it has to move, and it takes time for that to happen given the small difference in density which is the only thing causing the cold air to gain momentum.

That is, cold air isn't going to pour out of a fridge like cold water would. The small difference in density is going to result in the cold air spilling out much more slowly than cold water would (for example). I suspect the difference would be similar to what would happen if you had a fridge full of cold water submerged in a warm swimming pool. Opening the door would result in some cold water spilling out, but nowhere near as much as would spill out if that fridge weren't submerged in warm water. The important difference being the fact that the driving force imparting momentum to the cold water is very much reduced.

On Friday, July 25, 2014 4:44:02 PM UTC-4, J Burns wrote:
I keep reading that you should use things like water bottles and

crumpled newspapers to take up space so less air flows in when you open

a refrigerator door.



I calculate that if you changed the air in an empty 17cu ft refrigerator

for air at 75 F with a dew point of 65 F, cooling it to 35 F with a dew

point of 0 F would mean moving 15 joules, or 1 watt for 15 seconds,or

1/240,000 kwh.



There doesn't seem to be any point in using filler to reduce an

occasional air change. How about thermal mass? Water bottles could

reduce cycle times by increasing thermal mass. A compressor draws more

watts early in the cycle, but don't you get that back when the

compressor turns off?



Can filling a refrigerator really save energy?

When I managed an apartment building, one of my elderly tenants complained that her refrigerator wasn't keeping things cold enough although it was going on frequently. I called the repairman and went to inspect the refrigerator with him. He opened her refrigerator and, seeing only a quart of milk and a stick of butter, said that the problem was that she didn't have enough in it to keep the interior cold. He suggested that she keep a gallon of water in there, which solved the problem. Sort of like a thermal flywheel.

You should always keep the beer in the fridge. It's better cold and you never know when you might want another cold one.




You have a valid point about stuffing for the sake of stuffing, but if

you have a case of juice or beer, better to put it in to fill the space

rather than put a bottle at a time. You'll be using the same amount of

energy to get it down to temperature anyway, but get less air loss each

time the door is opened.