On Sat, 08 Jul 2006 20:06:58 -0400, Jeff wrote:



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

Sorry about the late reply - I've been out sailing.

You're making a common mistake. Although the specific heat of water
is 1 calorie per g-deg C, for ice its only about half that, or .5 cal
per g-deg C, or as I stated .5 BTU/lb-deg F. Thus, super cooling ice
add little cooling capacity.


This time I checked a little more carefully among the welter of old
American Customary, CGS old scientific and SI units people have been
applying.
First, agree that ice has half the specific heat capacity of water
and agree that fusion of ice takes 80 cal/gm or 80 X 4.2 J/gm or
80 x 4.2 x 1000 J/kg
so -40 degC to melting point provides 20 cal or 20 X 4.2 J/gm or
20 X 4.2 X 1000 J/kg
and
ice to water provides 80 cal/gm or 80 X 4.2 J/gm or 80 X 4.2 X 1000
J/kg

The ratio in question is ( 80 + 20 ) / 80 = 125%
(NOT 140%)

The extra 25% of cooling effect may qualify as "little" or
"appreciable". You choose! :-)

Regards
Brian Whatcott Altus OK