3 Analysis of diverse heat recovery steam cycles Text

Page 1

COURSE OF ENERGY CONVERSION A 2015/2016 Prof. G. Valenti 3rd Project Comparison of heat recovery steam cycles Consider a combined cycle with the same simple cycle gas turbine described in the second project. With the aid of the software Turbogas, determine (i) the air mass flow rate supplied to the compressor, (ii) the turbine inlet temperature (TIT) and (iii) the compressor pressure ratio that ensure the most similar performance to those of the gas turbine engine of the second project. Examine the different obtainable performances of the following heat recovery steam cycles: a) one evaporation level b) two evaporation levels c) three evaporation levels with superheating of the high pressure steam Within the software Turbogas, consider the following calculation assumptions:  case a: evaporation pressure equal to the optimised value of the previous project;  case b: LP / HP pressures: 6.3 / 76 bar ;  case c: LP / IP / HP pressures: 3 / 25 / 150 bar, with superheating pressure equal to the IP one; Use the following data for all the considered cases (a,b,c): Condensing pressure: 0.05 bar Tap: 25 C Deareator pressure: 2.0 bar Tsc: 10 C Tpp: 10 C p/peconomizzatore: 10 % Assume the software default values for all the other parameters that have not been specified. It is required to: 1) cases a,b,c :  report in a table the efficiencies of cycle (CV), thermal recovery (rec-th), recovery (rec), second-law (II), as well as the steam cycle net power and the exhaust gas stack temperature;  report in a table and compare the following entropy losses terms (referred to the reversible power of the exhaust gases that do not include the chemical exergy term): efficiency loss of the heat recovery steam generator (HRSG) and at the stack (stack); 2) case c only:  plot…