Exercise 1 Working fluid properties

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ENERGY CONVERSION A 2016-17 1 Exercises Working fluid properties Exercise 1 Compare two power plants, both based on the saturated Rankine cycle. Th ese plants differ by the working fluid as follows. (A) Water (B) Organic fluid Enthalpy of evaporation 2014 kJ/kg Molar mass 200 kg/kmol Specific heat of steam 2.6 kJ/kg K Critical temperature 370°C Critical pressure 50 bar Liquid density 800 kg/m3 Specific heat of liquid 1.5 kJ/kg K Both cycles operate between a maximum temperature of 170°C and a minimum temperature of 40°C. Moreover, they exploit a heat source with a constant – but not infinite – heat capacity and at a maximum temperature of 225°C. Please, indicate: (i) which is the cycle with the highest thermodynamic efficiency; (ii) which is the turbine working with the highest volume ratio; (iii) which plant with the largest power production; Do not employ preheaters or a recuperator. Moreover, complete the exercise considering first ideal equipment and, subsequently, real equipment. Exercise 2 Sketch qualitatively on the T-s diagram the following isobaric lines and saturation dome:  pressure = 1 bar  pressure = 80 bar  pressure = 300 bar in the range 0-1000°C and for the fluid CO2 (critical pressure and temperature: 73 bar, 31°C). Exercise 3 A saturated cycle operates between 150°C and 40°C. The working fluid is characterized by:  critical temperature = 600 K  critical pressure = 50 bar  molecular weight = 150  ratio cp/R = 40 (supposed constant in the range of considered temperature) Please: (i) determine with the inevitable approximations of the corresponding state principle: a. the pressures in which the cycle operates; b. the enthalpy expansion of the turbine; (ii) sketch the plant layout and illustrate qualitatively the cycle on the T-s diagram; (iii)…