Water vapor enters a valve with a mass flow rate of 1 kg/s at a temperature of 260°C and a pressure of 3.5 MPa, and undergoes a throttling process to 2.75 MPa. (T0 = 25°C, P0 = 100 kPa)
a) Determine the total flow exergy rates at the valve inlet and exit, and the rate of exergy destruction (all in kW).
b) Evaluating exergy at $0.08/kW?hr, determine the annual cost associated with the exergy destruction, assuming 8000 hours of annual operation.