Detailed analysis of the effect of the turbine and compressor isentropic efficiency on the thermal and exergy efficiency of a Brayton cycle
| Autor: | Antun Galović, Zdravko Virag, Marija Živić |
|---|---|
| Rok vydání: | 2014 |
| Předmět: |
Overall pressure ratio
Exergy Thermal efficiency Isentropic process Renewable Energy Sustainability and the Environment lcsh:Mechanical engineering and machinery Nuclear engineering Thermodynamics Brayton cycle net work per cycle Thermodynamic cycle exergy efficiency thermal efficiency Exergy efficiency Environmental science lcsh:TJ1-1570 Gas compressor |
| Zdroj: | Thermal Science, Vol 18, Iss 3, Pp 843-852 (2014) |
| ISSN: | 2334-7163 0354-9836 |
| DOI: | 10.2298/tsci1403843z |
| Popis: | Energy and exergy analysis of a Brayton cycle with an ideal gas is given. The irreversibility of the adiabatic processes in turbine and compressor is taken into account through their isentropic efficiencies. The net work per cycle, the thermal efficiency and the two exergy efficiencies are expressed as functions of the four dimensionless variables: the isentropic efficiencies of turbine and compressor, the pressure ratio, and the temperature ratio. It is shown that the maximal values of the net work per cycle, the thermal and the exergy efficiency are achieved when the isentropic efficiencies and temperature ratio are as high as possible, while the different values of pressure ratio that maximize the net work per cycle, the thermal and the exergy efficiencies exist. These pressure ratios increase with the increase of the temperature ratio and the isentropic efficiency of compressor and turbine. The increase of the turbine isentropic efficiency has a greater impact on the increase of the net work per cycle and the thermal efficiency of a Brayton cycle than the same increase of compressor isentropic efficiency. Finally, two goal functions are proposed for thermodynamic optimization of a Brayton cycle for given values of the temperature ratio and the compressor and turbine isentropic efficiencies. The first maximizes the sum of the net work per cycle and thermal efficiency while the second the net work per cycle and exergy efficiency. In both cases the optimal pressure ratio is closer to the pressure ratio that maximizes the net work per cycle. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|