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Thermo question

by chopper
Tags: thermo
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chopper
#1
Mar27-06, 09:48 PM
P: 1
I need a kick start for the following question. We're studying open/closed systems at the moment.

"450kg of ice at -18 degrees C is to be removed from a freezer using a jet of steam. How much dry steam at 100 degrees C is required if the final temp of the effluent is 5 degrees C?"

This is what I've sussed out so far.. because mass is being added to the system (the mass of the steam) I assume this is an open system problem. I haven't been given any information regarding enthalpy of either the ice or the steam so I'm assuming it's a simple matter of working out how much energy I need to bring the ice up to 5 degrees and introducing that energy into the freezer in the form of steam that will be giving up energy as it cools down to 5 degrees.

Can anyone point me in the right direction?

Cheers
Chopper
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Andrew Mason
#2
Mar29-06, 07:48 AM
Sci Advisor
HW Helper
P: 6,654
Quote Quote by chopper
I need a kick start for the following question. We're studying open/closed systems at the moment.

"450kg of ice at -18 degrees C is to be removed from a freezer using a jet of steam. How much dry steam at 100 degrees C is required if the final temp of the effluent is 5 degrees C?"

This is what I've sussed out so far.. because mass is being added to the system (the mass of the steam) I assume this is an open system problem. I haven't been given any information regarding enthalpy of either the ice or the steam so I'm assuming it's a simple matter of working out how much energy I need to bring the ice up to 5 degrees and introducing that energy into the freezer in the form of steam that will be giving up energy as it cools down to 5 degrees.
It should be a simple matter of algebra. Just set up the expression for heat h needed to raise the temperature of 450 kg of ice to 5 degrees and the heat lost by a mass m of stream. Equate the two and solve for m.

AM


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