## 5 Result and Discussion
### Exergy Destruction Rate
When \(T_{\rm g1}\) is 593.15-623.15 K, \(I_{\rm Hout}\) decreases considerably and then \(I_{\rm L\rm c}\) becomes the largest given the improvement of \(\eta_{\rm g}\). When \(T_{\rm g1}\) is 523.15-613.15 K, \(I_{\rm He}\) is the third largest. When \(T_{\rm g1}\) is 618.15-623.15 K, \(I_{\rm He}\) decreases rapidly to 4.8%, and \(I_{\rm H\rm H}\) becomes the third largest because the optimal HTL evaporation temperature reaches the upper limit. When \(T_{\rm g1}\) is 588.15-623.15 K, \(I_{\rm L\rm pre}\) is the second smallest; the \(I_{\rm P}\) is the smallest. In Figure 17, when toluene is used for HTL no sudden changes are observed because the optimal HTL evaporation temperature does not reach the upper limit. Given the improvement of \(\eta_{\rm g}\), \(I_{\rm Hout}\) decreases with the increase in \(T_{\rm g1}\). Considering that the optimal HTL evaporation temperature increases with \(T_{\rm g1}\), \(I_{\rm He}\) decreases with the increase in \(T_{\rm g1}\). Furthermore, \(I_{\rm L\rm c}\), \(I_{\rm ce}\), and \(I_{\rm H\rm H}\) increase with \(T_{\rm g1}\) due to the decrease in \(I_{\rm Hout}\) and \(I_{\rm He}\). Given that the HTL condensation temperature is unchanged and the power consumed by the pump is small, the relative variations in \(I_{\rm L\rm pre}\), \(I_{\rm L\rm t}\), and \(I_{\rm P}\) are less than 0.5% between the maximal and minimal values. Considering the low \(\eta_{\rm g}\), \(I_{\rm Hout}\) is the largest exergy destruction rate, and it is followed by \(I_{\rm L\rm c}\) and \(I_{\rm He}\). \(I_{\rm P}\), \(I_{\rm L\rm pre}\), and \(I_{\rm H\rm H}\) are less than the other components with \(T_{\rm g1}\) of 523.15-623.15 K.  
Figure 15: Effects of \(T_{\rm g1}\) on exergy destruction rate for the cyclohexane system. The variations in the exergy destruction rate with \(T_{\rm g1}\) are different for various HTL working fluids. \(I_{\rm Hout}\) and \(I_{\rm LC}\) are the top two in most cases, but \(I_{\rm He}\) and \(I_{\rm ce}\) are also important. Given the limit of acid dew point temperature, \(I_{\rm Hout}\) is inevitable for the cyclopentane system; an increase in \(T_{\rm g1}\) will improve \(\eta_{\rm g}\) for the cyclohexane, benzene, and toluene systems. Moreover, when cyclopentane is used, and \(T_{\rm g1}\) is 623.15 K, \(I_{\rm Hout}\) is decreased to 7.8%. Considering the isothermal phase characteristic of pure fluids (When pure working fluid evaporates or condenses at constant pressure, the evaporation or condensation temperature is also constant), significant irreversibilities are observed in the HTL evaporator and LTL condenser [3; 52; 53], thus leading to large \(I_{\rm LC}\) and \(I_{\rm He}\). The use of zeotropic mixtures with non-isothermal phase change characteristics will cause improved temperature matches between the ICE exhaust gas and HTL, LTL, and cooling water [3; 43] and then decrease \(I_{\rm LC}\) and \(I_{\rm He}\). When \(T_{\rm g1}\) is high (higher than or equal to 537.15 K for the cyclopentane and cyclohexane systems, 593.15 K for the benzene system, and 598.15 K for the toluene system), \(I_{\rm Lpre}\) is the second smallest exergy destruction rate. \(I_{\rm p}\) is the minimal exergy destruction rate.