Responding to the message of <00b301bfed4f$06d0a6c0$2c2b2fd1@temp.klis.com>
from bellcom@klis.com:
>
>
> There must be an easy was to determine how much ice should be added to a =
> known quantity fish to chill it to a determined temperature knowing how =
> much fish one has and what the temperature is before adding ice. Anybody =
> out there know what it is and is willing to share it?
>
>Simple enough essentially a heat balance
1st assumption all heat losses due soley to exchange
units I will use english
terms: Specific heat Cp Btu/lb F for water = 1 for fish depends on fat range
is 0.7 to 0.85 specific heat of ice = 0.5
latent heat of fusion HL = 144 Btu/lb
Mi mass of ice thawed = MW mass of liquid water warmed
Mf = mass of fish
Ti = initial ice temperature Tfi = initial fish temperature F TFF = final
fish temperature
assme all ice thaws and then warms as water to the tempeature that the fish
cools to so calculate ice melt heat (latent) plus ice warming heat (Ti to 32
which is sensible) the water warm heat (32 to final temperature Tff)
equation:
Ice latent heat+ ice sensible heat + water sansible heat = fish sensible heat
change
(Mi * HL) +Mi *Cpi (32 - Ti)+ Mw Cpw * (Tff-32) = Mf*Cpf(Tfi-Tff)
since assume Mi = Mw then Mi =Mf*Cpf(Tfi-Tff) Divided
by(Hl+Cpi(32-Ti)+Cpw(Tff-32))
simple algebra
errors involved
not all ice metls and some heat loss to container and air
Better use excess ice as get more bang for your buck from fusion heat also
using exact amount woud end up taking very long Over cing speeds the rate
Dr Ted Labuza tplabuza@tc.umn.edu
Prof. of Food Science Dept. of Food Science & Nutrition 136 ABLMS U of Minn St
Paul, MN 55108 Voice 612-624-9701 Fax 612-625-5272 home fax 651-483-3302
cellemail 6126697885@mobile.att.net
http://fscn.che.umn.edu/Ted_Labuza/tpl.html
"SURFING THE WAVES OF CYBERSPACE"
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|ˇˇ|
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|__| "The attitude of an engineer must be different than
| that of a mathematician. The engineer is concerned with
---|---- truth, not mere consistency." Biot
/ \
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\ /\ / \/ \ /\/
"Before I came here I was confused about this subject. Having listened to your
lecture I am still confused But on a higher level."- E. Fermi
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