Question

3. Steam at 20 bar and 640 °C is available at one location in an industrial plant. At another location, steam at 15 bar and 360 °C is required for use in a certain process. An engineer suggests that steam at this condition can be provided by allowing the higher-pressure steam to expand through a valve to 15 bar and then cool to 360 °C through a heat exchanger with heat transfer to the surroundings, which are at 25 °GC Evaluate this suggestion by determining the associated exergy destruction rate per mass flow rate of steam (kJ/kg) for the valve and heat exchanger. Discuss Evaluating exergy at 8 cents per kWh and assuming continuous operation at steady state, determine the total annual cost, in S, of the exergy destruction for a mass flow rate of 1 kg/s. a. b.

Answer 1

Coutaut nereae e, Ca) (b). Gust, 阜0.08 Itulhr. perday- (0.8) x(39.33) yzy 5.525 25 66.66