## 3 Result and Discussion
### Comparison of the Analysis Methods  
Table 4 lists the fundamental results calculated from the conventional exergy analysis on CCHP system. It is found that the CS possesses the biggest exergy destruction (\(y^{*}_{\rm{CS}}=23.20\%\)) and the lowest exergy efficiency (\(\varepsilon_{\rm{CS}}=80.15\%\)) except for HE3 and HE4. The reason can be given that two phase-transition processes in CS results in high irreversible loss. The second biggest exergy destruction rate is located in C1 with \(y^{*}_{\rm{C1}}=12.93\%\), followed by HE3, C2, T2, T1, and HE2 in sequence (\(y^{*}_{\rm{HE3}}=12.79\%\), \(y^{*}_{\rm{C2}}=11.27\%\), \(y^{*}_{\rm{T2}}=10.34\%\), \(y^{*}_{\rm{T1}}=9.84\%\), \(y^{*}_{\rm{HE2}}=9.14\%\)). The exergy destruction rates within TV2, HE1, TV1, HE4 are rather low, and together, they account for only 10.49% of the system exergy destruction. In addition, it is seen that HE2 and HE3 located in supercritical state have  
Figure 2: The flow chart of the calculation procedure. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Component** & **Parameter** & **Real** & **Unavoidable** & **Ideal** \\ \hline Compressor & \(\eta_{C}\) & 0.85 & 0.95 & 1 \\ Turbine & \(\eta_{T}\) & 0.85 & 0.95 & 1 \\ HE & \(\Delta\tau_{min}\) & 5 K & 1.5 K & 0 \\ CS & \(\Delta\tau_{min}\) & 5 K & 1.5 K & 0 \\ TV & - & Isenthalpic & Isenthalpic & Isentropic \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Values at real, unavoidable and ideal cycles [34; 35; 36]. much more irreversible loss than HE1 and HE4 (\(y^{*}_{\text{HE1}}=2.69\%\), \(y^{*}_{\text{HE4}}=1.03\%\)) within gaseous state. The logical explanation behind this phenomenon can be given in two aspects. The mass flow of cooling water is larger for supercritical CO2 owning to its higher specific heat. Moreover, the properties of supercritical CO2 are more sensitive to temperature, and thus a larger temperature difference will occur to guarantee the set pinch temperature. For instance, the upper terminal temperature difference of HE1 and HE2 are 5 K and 34.15 K, respectively. From the system point, the total fuel energy \(\dot{E}_{F,tot}\) originates from the power supplied to compressors, and \(\dot{E}_{P,tot}\) is the summation of the power produced in turbines and the heating and cooling exergy. The overall system has an exergy efficiency of 56.25%, and therefore 43.20% of the system fuel exergy is destroyed. Using the approach aforesaid, all detailed exergy parts are shown in Table 5. One can notice that the endogenous part is much larger than the exogenous part, implying that the exergy destruction within each component is mainly induced by its own irreversibility. The exogenous part is zero for C2, HE2 and all throttle valves, indicating that for these components the exergy destructions are introduced only by their endogenous irreversibility. The negative exogenous exergy destructions within turbines and HE3 mean that enhancing the irreversible loss in other system components lessens the exergy destruction within these components. It is concluded that the communications of components in the CCHP system based on TC-CCES are not strong but rather complex. One can also see in Table 5 that only turbomachineries and CS possess higher avoidable part than unavoidable part and therefore 48.5% of the system exergy destruction cannot be eliminated in the studied condition. The CS exists the largest magnitude of avoidable part (\(\dot{E}_{\text{D,CS}}^{\text{AV}}=300.21\) kW), followed by compressors and turbines. In addition, the reader should concentrate mainly on \(\dot{E}_{\text{D,k}}^{\text{AV,EN}}\) and \(\dot{E}_{\text{D,k}}^{\text{AV,EX}}\). It is observed that all the components except of HE4 and TV2 have larger \(\dot{E}_{\text{D,k}}^{\text{AV,EN}}\) than \(\dot{E}_{\text{D,k}}^{\text{AV,EX}}\), which demonstrates that the elimination of energy losses in the system depends mainly on improving the performance of components themselves. Very readable foundation is shown by concentrating on \(\dot{E}_{\text{D,HE4}}^{\text{AV,EN}}\).