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re: most efficient refrigerator
28 jan 2004
daestrom wrote:
>> >and we open the door 1 minute 4x per day, and each time
>> >16.6'x3'x5'/2sqrt(2.5'(70-36)) cfm of 70 f air at 50% rh
>> >flows through the fridge,
>>
>> totaling 4591 ft^3, about 344 pounds of air with w = 0.00787 pounds
>> of water vapor per pound of air...
>that number is suspect.
some suggest it's too low.
>the formula is for the natural convection of a vertical surface.
i was thinking about a thermal chimney with lots of cold thermal mass
and mass surface and conductance, and no airflow resistance inside.
>the 'full' unit has several surfaces, some vertical, some horizontal and
>several obstructions to simple convection flow. if you pack it like mine,
>there are complete shelves with only a top and bottom surface, no exposed
>sides except the front face.
sounds very organized. i'm thinking upright fridge vs freezer, btw.
wire vs glass shelves would facilitate airflow...
>and although the empty unit has less overall surface inside it,
>there is no obstructions to natural flow.
sure.
>the 'empty' unit probably doesn't have constant flow for the whole 'minute'.
>the large 'slug' of cold air originally in the unit would spill out on to
>the floor, much higher initial flow rate than formula. the air going in to
>replace it would *begin* to flow iaw your formula after some time.
yes indeedy. "some time."
>doubt you get anywhere near stable flow conditions in just a minute,
>or even two or three.
the airflow might exceed the formula i used during this time. we need cfd.
>too complex to calculate with simple steady-state convection flow formulae.
>best answer would be to run some experiments with a watt-hour meter. some
>right before grocery-shopping day, some a day after.
sounds good. the extra day would allow the food to reach the fridge temp.
i am seldom so pleased with our collective search for truth via the net.
nick
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