Dry Ice Box?
On Sun, 02 Jul 2006 08:31:58 -0400, Jeff wrote:
Chris wrote:
For water, the heat of fusion is about 80 times specific heat...
So -70 C ice would have almost twice the cooling effect
as the same amount of barely frozen ice, right?
Wrong. You should look up the Heat Capacity of cold ice. Its only
0.5 BTU/lb-degree at freezing, but it goes down so that by -50 F its
only 0.4.
Since the Heat of Fusion is 144 BTU/lb, sub-cooling even 100 degrees
only adds a small amount of cooling capacity.
Hardly 'hadly effective'.
No, its hardly effective.
This is in error: using old CGS units
heat for fusion of ice is 80 cal/gm specific heat cap near 0degC is
1 cal/gm
Supercool to -40 deg C and its worth roughly another 40% of cooling
power cf. ice at freezing.
Brian Whatcott Altus OK
|