3. Ice at -50 oF is to be melted in a continuous flow process with saturated ste

Question

3. Ice at -50 oF is to be melted in a continuous flow process with saturated steam at 1 bar. Find the minimum quantity of steam required per pound of ice. The heat capacity of ice is 0.45 Btu/lbm oF.

The minimum steam requirement is achieved when the condensed steam emerges at the melting temperature of water. If the streams do not mix, we can take separate references states for the steam/condensate and ice/melt water streams. Please Please show any and all steps that helped you arrive at your answer!:)

Explanation / Answer

ice needs to be brought from -50 deg.F to 32 deg.F, hence sensible heat = mass*specific heat* temperature difference= 1(assumed) * 0.45*(32+50)= 36.9 btu

heat of fusion of ice = 144 btu/lb, hence heat to be supplied for 1 lb of ice = 144

total heat to be added = 144+36.9= 180.9 btu

latent heat of water at 1 bar= 970.4 btu/lb (100 deg.c =212deg.F

heat from fusion = m*970.4

from 212 deg.F to 0 deg,c, it is sesnsible heat = m* 0.327*100

total heat = m*970.4 +32.7m = 1003,1m

hence 1003.1 m= 180.9

m= 180.9/1003.1 lb steam/lb ice =0.18 lb steam/lb ice

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