Exergy analysis and optimization of combined brayton and rankine cycles

This thesis deals with the concept of energy and how energy has changed throughout the historical process, and in which direction and development it has shown. The two subheadings of energy sources, renewable and non-renewable energy sources, have been examined and firstly renewable energy sources have been investigated. These sources are solar, wind, hydraulic, geothermal, biomass and wave energies. These types of energy are sustainable and do not harm the environment in themselves. Then, coal, oil, natural gas and nuclear energies, which are exhaustible and often harmful to the environment, have been investigated. The usage of all these energy sources in the world and in Turkey, their geographical distributions and their features have been shown, and the concept of exergy and the important points of exergy, the types of exergy, kinetic and potential exergy, physical exergy, chemical exergy, exergy with heat, exergy with work, exergy with mass and destruction of exergy have been examined for combined cycles. As the pump pressure of the Rankine cycle increases from 400 kPa to 7600 kPa, the exergy efficiency increases from 76% to 85%, and as the compression pressure of the Brayton cycle increases from 400 kPa to 2200 kPa, the exergy efficiency increases from 72% to 79%. When these operating conditions, where the two cycles will operate at their optimum, are applied together, the exergy efficiency of the entire system exceeds 86%. When the operating conditions, where the Brayton and Rankine cycles are at their maximum efficiency, are applied together, the optimum operating conditions of the system are obtained. Keywords: Brayton, Rankine, energy, exergy, optimization