In order to cool 1 ton of water at 20°C in an insulated tank, a person pours 80 kg of ice at 25°C into the water. Determine
(a) The final equilibrium temperature in the tank and
(b) The exergy destroyed during this process. The melting temperature and the heat of fusion of ice at atmospheric pressure are 0°C and 333.7 kJ/kg, respectively. Take T0 = 20°C.