## 4 Results and Discussion
### Combined ORC-Dual Evaporator VCR Cycle Results  
Figure 13 indicates effect of temperature of first evaporator on \(\mathrm{COP_{sys}}\), \(\mathrm{\eta_{lex,sys}}\), and \(\mathrm{\dot{m}_{total}}\). \(\mathrm{COP_{sys}}\) increases as temperature of first evaporator increases according to Figure 13a. When \(\mathrm{T_{evap,1}}\) rises, pressure and enthalpy at the exit of first evaporator increases. This condition causes an increase of enthalpy at compressor inlet and compressor power decreases. For this reason, \(\mathrm{COP_{VCR}}\) and thereby \(\mathrm{COP_{sys}}\) increases. Figure 13b shows that there is not a significant change in exergy efficiency of the combined system. Exergy transferred with heat in first evaporator decreases with increase in its temperature. This situation tries to decrease \(\mathrm{\eta_{lex,VCR}}\) according to Equation (12). However, decrease in compressor power tries to increase \(\mathrm{\eta_{lex,VCR}}\) with respect to same equation. Consequently, \(\mathrm{\eta_{lex,VCR}}\) and therefore \(\mathrm{\eta_{lex,sys}}\) almost remain the same. Increase in \(\mathrm{T_{evap,1}}\) causes decrease in \(\mathrm{\dot{m}_{total}}\) as represented in Figure 13c. Due to the fact that compressor power decreases with rise in temperature of first evaporator, turbine power declines too. \(\mathrm{\dot{m}_{ORC}}\) decreases in connection with decrease in turbine power. As a result, total mass flow rate of combined system decreases as well. Figure 12: Second law efficiency (**a**) and degree of thermodynamic perfection (**b**) for each component in combined ORC-single evaporator VCR cycle. Figure 13: Effect of \(\mathrm{T_{evap,1}}\) on \(\mathrm{COP_{sys}}\) (**a**), \(\mathrm{\eta_{ex,sys}}\) (**b**), and \(\mathrm{\dot{m}_{total}}\) (**c**) in combined ORC-dual evaporator VCR cycle. Figure 14: Impact of \(\rm T_{evap,2}\) on \(\rm COP_{sys}\) (**a**), \(\rm\eta_{ex,sys}\) (**b**), and \(\rm rh_{total}\) (**c**) in combined ORC-dual evaporator VCR cycle. Figure 14 clarifies how system performance is impacted with temperature of second evaporator. Increase of T\({}_{\text{evap,2}}\) from 0 \({}^{\circ}\)C to 10 \({}^{\circ}\)C does not cause an important change in COP\({}_{\text{sys}}\) as can be detected from Figure 14a. As T\({}_{\text{evap,2}}\) rises, pressure and enthalpy at the exit of second evaporator increases. It is normally expected to affect this condition inlet pressure to the compressor. Hence, the third expansion valve, which is basically an evaporator pressure regulator, ensures that fluid has the same pressure with fluid flowing from the other branch at the inlet of mixing chamber. For this reason, pressure at the inlet of compressor does not change. On the other hand, enthalpy at the inlet of compressor is not importantly effected by increase of T\({}_{\text{evap,2}}\) since mass flow rate flowing through first evaporator is twice higher than that of second evaporator, thus an increase of h\({}_{10}\) has a greater effect than h\({}_{7}\) on h\({}_{1}\) according to energy equation for mixing chamber given in Table 6. For these reasons, compressor power does not change significantly with increase in T\({}_{\text{evap,2}}\). As a result, both COP\({}_{\text{VCR}}\) and COP\({}_{\text{sys}}\) almost remain unchanged. Figure 14b represents that \(\eta_{\text{lex,sys}}\) declines with increasing T\({}_{\text{evap,2}}\). Because of the fact that compressor power is not considerably effected by increase in T\({}_{\text{evap,2}}\), the most important parameter that influences \(\eta_{\text{lex,VCR}}\) is the exergy transferred by heat in second evaporator according to Equation (12). Increase in T\({}_{\text{evap,2}}\) causes reduction in E\({}_{\text{Q,evap,2}}\). So, \(\eta_{\text{lex,VCR}}\) and, thus, \(\eta_{\text{lex,sys}}\) decline. Effect of T\({}_{\text{evap,2}}\) on \(\dot{\text{n}}_{\text{total}}\) is depicted in Figure 14c. It can be seen that \(\dot{\text{n}}_{\text{total}}\) is not impacted by increase of T\({}_{\text{evap,2}}\).