1: Steam at 100°C is passed into a condenser at a rate of 500 kg/h and leaves as water at 60°C. If the condenser is supplied with cooling water which enters at 20°C and leaves at 40°C, calculate:
a) how much heat per hour is extracted from the steam.
b) how much cooling water is needed per hour.
2: A cupola furnace is charged with 100 kg of aluminium to be used for casting small components. The melting point of aluminium is 657°C, its specific heat capacity is 924 J/kg °C and its latent heat of fusion is 322 kJ/kg.
Calculate the total heat energy which must be supplied to melt the aluminium if its initial temperature is 20°C.
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(a) Heat extracted from steam = Q = m s t
M = 500 Kg = 500000 grams
s = specific heat of steam = 0.48 calorie per gram per degree Celsius= 2.00928 joules per gram per degree Celsius
t = 100 -60 = 40 degree Celsius
M = 500000 2.00928 40 = 4.01856 107 Joules
(b) cooling water needed per hour ;
M = 4.01856 107 ...
Heat transfer with regard to steam and aluminum is investigated.