A computer model was developed to perform a thermodynamic analysis of the transcritical carbon dioxide cycle with two-stage compression and intercooling. In typical two-stage compression with intercooling applications, the intercooler serves the purpose to cool the fluid to the lowest possible temperature before it enters the 2nd-stage compressor. Ideally, the fluid temperature at the inlet to the 2nd-stage compressor is the same as the fluid temperature at the inlet to the 1st-stage compressor. In this case, the minimum compression work and thus, the highest system efficiency, is achieved by using the same pressure ratio across both compressors. However, this is not the case for the transcritical carbon dioxide cycle. Due to the supercritical heat rejection of the transcritical cycle and the slopes of the isotherms in the supercritical region, the highest system efficiency may be achieved at pressure ratios of the 1st and 2nd-stage compressors that are significantly different from each other depending on operating conditions. This paper presents the results of the system analysis of the transcritical carbon dioxide cycle with two-stage compression and intercooling and identifies the pressure ratios that provide maximum system efficiency.
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