Performance Analysis of an Irreversible Regenerative Brayton Cycle Based on Ecological Optimization Criterion

Abstract

An ecological optimization along with a detailed parametric analysis of an irreversible regenerative Brayton cycle with finite heat capacity of external reservoirs have been carried out. The external irreversibilities due to finite temperature difference and internal irreversibilities due to fluid friction losses in compressor / turbine, regenerative heat loss, pressure loss are included in the analysis. Ecological function is thermodynamically optimized which is defined as the power output minus the product of environment temperature and entropy generation rate. A detailed analysis shows that the ecological function and corresponding power output / thermal efficiency can be maximized with judicious selection of parameters such as efficiency of turbine and compressor, effectiveness of various heat exchangers, heat source inlet temperature, pressure drop recovery coefficients and heat capacitance rate of the working fluid. It is found that the regenerative effectiveness is more prominent for maximum ecological function and corresponding thermal efficiency while cold side effectiveness is dominant factor for corresponding power output. It is also found that the effect of turbine efficiency (ηt) is more than the compressor efficiency (ηc) on the thermodynamic performance of an irreversible regenerative Brayton heat engine cycle. The model analyzed in this paper gives lower values of various performance parameters as expected and replicates the results of an irreversible regenerative Brayton cycle model discussed in the literature at pressure recovery coefficients of α1=α2=1.