Chapter 8, Problem 8.44CU

Steam is the working fluid in the ideal reheat cycle shown in the following figure together with operational data. If the mass flow rate is 1.3 kg/s, determine the power developed by the cycle, in kW, and the cycle thermal efficiency. 6 p = 140 bar p = 15 bar p = 1 bar State 1 2 3 4 5 6 p (bar) 140 15 15 1 1 140 T (°C) 520.0 201.2 428.9 99.63 99.63 h (kJ/kg) 3377.8 2800.0 3318.5 2675.5 417.46 431.96

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3. A medium size power station is used to produce 30 MW net power for a refinery. The station uses steam as the operating fluid and operates according to the Carnot cycle between the pressure limits of 0.4 bar and 35 bar. Steam enters the boiler as a saturated liquid and leaves it as a dry saturated vapour. (vii) Using the highest and lowest temperature values in the cycle, recalculate the efficiency of the cycle and show that it is equivalent to the result in part (vi). (viii) Calculate the thermal efficiency of the power station if the isentropic efficiency of the steam turbine is 94%. (ix) State main disadvantages of using the Carnot cycle as the basis for a power station. (x) State the name of the cycle that is used in practice in power stations, along with three key benefits over the Carnot cycle.