Steam at 3MPa and 700 degrees C is available at one location in an industrial plant. At another location, steam at 2MPa, 400 degrees C and mass flow rate of 1kg/s is required for use in a process. An engineer suggests that steam at this condition can be provided by allowing the higher pressure steam to expand through a valve to 2MPa and then flow through a heat exchanger where the steam cools at constant pressure to 400 degree C by heat transfer to the surroundings at 20 degree C. Assume To= 20 degrees C.
(a) Determine the total rate of exergy destruction that would result from the implementation of this recommendation.
(b) If energy costs 8 cents per kW h, determine the annual cost of the exergy destruction determined in part a) for 8000 hours of per year operation.
(c) Comment on this suggestion, what are the pros and cons for implementation. What solution would you propose?