Exercise 1 Working fluid properties

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ENERGY CONVERSION A 2019-20 1 Exercises Working fluid properties Exercise 1 Compare two power plants based on the saturated Rankine cycle but operating with different working fluid. The cycles operate between a maximum temperature of 170 °C and a minimum of 40 °C. Moreo- ver, they exploit a heat source with a constant heat capacity and at a maximum temperature of 225 °C. (A) Water (B) Organic fluid Evaporation enthalpy at 170 °C 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 Excluding the use of preheaters or recuperators, please, determine numerically: i. which is the cycle with the highest thermodynamic efficiency; ii. which is the turbine working with the highest volume ratio; iii. which is the plant with the largest power production. 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 kg/kmol  ratio cp/R : 40 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 process flow diagram and illustrate qualitatively the cycle on the T-s diagram; iii. calculate the volume ratio. Exercise 4 Consider a binary cycle made of two cascade saturated cycles, the first operating with an hypothetical liquid metal…