--- Barry Gershenfeld <barry_g@zmicro.com> wrote:
> >A fridge that takes only 0.1 kWh a day
> 
> The author states that when you open the door on a
> vertical refrigerator, 
> you lose all the cold air.
> 
> And my question is, what is the significance of this
> volume of air?  It 
> seems that the heat content of air is quite a bit
> lower than the heat 
> content of the objects inside.

You are quite right. Letting in some warm air does not
waste huge amounts of energy. But the food starts
cooling the warm air, so the longer the door is open,
the more energy is lost.

> years.   A manual once 
> stated that the fridge would work more efficiently
> if you kept it full of 
> stuff.  That got me thinking.

That might have more to do with the way thermostats
are designed. Since compressors don't have
proportional cooling, and there's no perfect location
for the temperature sensor, it basically all works
better if there's a good mass of food inside so the
variable duty cycle of operation becomes smooth
temperature control.

I've designed a couple of electronic thermostats for
refrigerators, and you have minimum on and off times
running a higher priority than temperature, so an
empty fridge will have large temperature swings.

Cheerful regards,

Bob

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