# Finite Time Thermodynamic Analysis of Modified Brayton Cycle

## Abstract

It is well known that reheating in gas turbine engines limits the extent to which an isothermal heat addition is approached. With respect to a simple heat addition, when a compressible gas with subsonic velocity flows through a frictionless constant area duct with heat addition, the temperature of the gas increases along the duct. Also with respect to simple area change, when a compressible fluid/gas with subsonic velocity flows through a frictionless adiabatic duct with decreasing area, the temperature of the gas decreases along the duct. The idealized isothermal process consists of a compressible gas with subsonic velocity flowing through a frictionless converging duct, such that while heated all along the duct, any infinitesimal decrease in temperature due to simple area change is exactly compensated by the simple heat addition. It is noted that, since temperature of the gas is constant during the isothermal heat addition, the kinetic energy of the gas and hence the Mach number must increase in order to satisfy the conservation of energy. The appropriate application of the idealized isothermal process is to gas turbine engines operating with air. It is equally desirable that the Brayton cycle is modified by the isothermal heat addition process.

### References

- Göktun, S. and Yavuz, H. (1999). Thermal efficiency of a regenerative Brayton cycle with isothermal heat addition.
*Energy Conv. Mangt*,**40**, 1259–1266.CrossRefGoogle Scholar - Ibrahim, O.M., Klein, S.A. and Mitchell, J.W. (1991). Optimum heat power cycles for specified boundary conditions.
*J. Engg. Gas Turbines Power*,**113**, 514–521.CrossRefGoogle Scholar - Kaushik, S.C. (1999). State-of-the-art on finite time thermodynamics. Internal Report CES, IIT Delhi, India.Google Scholar
- Kaushik, S.C., Singh, N. and Kumar, S. (1999a). Thermodynamic evaluation of a modified steam regenerative Brayton heat engine for solar thermal power generation.
*Solar Energy Society of India*,**9**, 63–75.Google Scholar - Kaushik, S.C., Kumar, P. and Khaliq, A. (1999b). Analysis of a endoreversible Rankine Cycle Cooling System.
*Energy Opportunities*,**xiv(1&2)**, 20–29.Google Scholar - Kaushik, S.C. and Tyagi, S.K. (2002). Finite time thermodynamic analysis of a nonisentropic regenerative Brayton heat engine.
*Int. J. Solar Energy*,**22**, 141–151.Google Scholar - Kaushik, S.C., Tyagi, S.K. and Singhal, M.K. (2003). Parametric study of an irreversible regenerative Brayton heat engine with isothermal heat addition.
*Energy Convers Mgmt*,**44**, 2013–2025.CrossRefGoogle Scholar - Kumar, S. (2000). Finite time thermodynamic analysis and second law evaluation of thermal energy conversion systems. Ph.D. Thesis, C.C.S. University, Meerut India.Google Scholar
- Redcenco, V., Vargas, J.V.C. and Bejan, A. (1998). Theoretical optimization of a gas turbine power plant with pressure drop irreversibilities.
*J. Energy Res. Tech*,**129**, 233–240.CrossRefGoogle Scholar - Tyagi, S.K., Kaushik, S.C. and Tyagi, B.K. (2000). Thermodynamic analysis of a regenerative Brayton cycle with isothermal heat addition, NREC-2000, 419–424, Nov. 30-Dec. 2, 2000, IIT Bombay, India.Google Scholar
- Tyagi, S.K., Kaushik, S.C. and Salhotra, R. (2002). Ecological optimization and parametric study of irreversible Ericsson and Stirling heat engines.
*Journal of Phys D: Appl. Phys*,**35**, 2668–2675.ADSCrossRefGoogle Scholar - Tyagi, S.K., Chen, J. and Kaushik, S.C. (2007). Effects of the intercooling on the performance of an irreversible regenerative modified Brayton cycle.
*Int. Journal of Power and Energy Systems*,**27**, 56–64.CrossRefGoogle Scholar - Tyagi, S.K. (2009). Effects of intercooling on the performance of a realistic regenerative Brayton heat engine cycle
*. Int. Journal of Sustainable Energy*,**28**, 231–245.ADSCrossRefGoogle Scholar - Vecchiarelli, J., Kawall, J.G. and Wallace, J.S. (1997). Analysis of a concept for increasing the efficiency of a Brayton cycle via isothermal heat addition.
*Int. Journal of Energy Research*,**21**, 113–127.CrossRefGoogle Scholar - Wang, W., Chen, L., Sun, F. and Wu, C. (2003). Performance analysis of and irreversible variable temperature heat reservoir closed intercooled regenerated Brayton cycle.
*Energy Convers Mgmt*,**44**, 2713–2732.CrossRefGoogle Scholar - Wu, C. and Kiang, R.L. (1990). Work and power optimization of a finite time Brayton cycle.
*Int. J. Ambient Energy*,**11**, 129–136.CrossRefGoogle Scholar - Wu, C. and Kiang, R.L. (1991). Power performance of a nonisentropic Brayton cycle.
*J. Engg. Gas Turbines Power*,**113**, 501–504.CrossRefGoogle Scholar