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.