Simulation of power cycle with energy utilization diagram

The graphical representation named energy utilization diagram (EUD) is a very useful tool for exergy analysis of chemical processes. This technique can be applied to the power cycle, the combination of heat exchangers and power subsystems. The cooperation of EUD with the process simulator was introduced to retrieve the simulation results and thermodynamic properties. The ASPEN Plus simulator was used in this research for constructing the EUD routine by programming in Fortran block and external Fortran files. The Rankine power cycle and an improved Rankine cycle were selected as a case study for verifying this routine. The sensitivity analysis of the Rankine cycle showed that the exergy loss/net generated power ratio (EXL/NGP) decreased with these three conditions: pump discharge pressure increase, turbine discharge pressure decrease and steam temperature increase. The increase of the subcooled temperature in the condenser affected the increase of EXL/NGP. The ratio of EXL/NGP could be reduced by 12.61% compared to the base case after adjusting the operating condition. In addition, the modification of the Rankine cycle to the Kalina cycle could be achieved for the purpose of exergy reduction. The ratio of EXL/NGP could be reduced from 2.04805 in the Rankine cycle (improvement case) to 1.06036 in the Kalina cycle. Thus, the efficiency of the power cycle could be improved significantly.