## 2 Modelling, Analysis and Optimization of a System
### Description of the Sinem GPP as a Case Study
The geofluid (85 \({}^{\circ}\)C and 590 kPa) collected at the output of the preheaters is pumped to the re-injection wells (GM4 and GM14) together with the condensed geofluid. As seen in Figure 2a and Table 1, the _n_-pentane heated in VAP 1 on level I is sent to turbine TURB 1 with 137.4 \({}^{\circ}\)C and 1261 kPa pressure as superheated steam (at point 12), to rotate the turbine. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Line, j**} & \multirow{2}{*}{**Fluid Type**} & **Temperature** & **Pressure** & **Mass Flow Rate** & **Energy Rate** \\  & & **T\({}_{\text{j}}\) (\({}^{\circ}\)C)** & **P\({}_{\text{j}}\) (kPa)** & **m\({}_{\text{j}}\) (kg/s)** & **E\({}_{\text{xj}}\) (kW)** \\ \hline
1 & Geofluid & 164 & 1040 & 445 & 52,693 \\
1\({}^{\prime}\) & Geofluid-steam & 165 & 1040 & 5.83 & 699 \\
1\({}^{\prime}\) & NCG & 165 & 1040 & 2.50 & 380 \\
2 & Geofluid & 136 & 730 & 445 & 36,010 \\
3 & Geofluid & 110 & 690 & 445 & 22,589 \\
4 & Geofluid & 110 & 690 & 22,250 & 11,295 \\
5 & Geofluid & 110 & 690 & 222.50 & 11,295 \\
6 & Geofluid & 89 & 590 & 222.50 & 7021 \\
7 & Geofluid & 81 & 570 & 222.50 & 5616 \\
8 & Geofluid & 85 & 590 & 445 & 12,447 \\
9 & Geofluid & 107 & 690 & 0.83 & 40 \\
10\({}^{\prime}\) & Geofluid-steam & 107 & 690 & 5.25 & 253 \\
10\({}^{\prime}\) & NCG & 107 & 690 & 2.25 & 257 \\
11 & _n_-pentane & 105 & 1261 & 160 & 4776 \\
12 & _n_-pentane & 137.4 & 1261 & 160 & 20,142 \\
13 & _n_-pentane & 82 & 150 & 160 & 7237 \\
14 & _n_-pentane & 60 & 150 & 160 & 6193 \\
15 & _n_-pentane & 31 & 150 & 160 & 123 \\
16 & _n_-pentane & 37 & 1261 & 160 & 520 \\
17 & _n_-pentane & 55 & 1261 & 160 & 1141 \\
18 & _n_-pentane & 106 & 687 & 169 & 5018 \\
19 & _n_-pentane & 109 & 687 & 169 & 16,512 \\
20 & _n_-pentane & 69 & 119 & 169 & 5713 \\
21 & _n_-pentane & 33 & 119 & 169 & 157 \\
22 & _n_-pentane & 39 & 687 & 169 & 431 \\ a & Air & 18 & 101 & 2000 & 0 \\ b & Air & 19 & 106 & 2000 & 8048 \\ c & Air & 18 & 101 & 2000 & 0 \\ d & Air & 19 & 106 & 2000 & 8048 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Thermodynamic properties collected and exergy rate calculated for each line number in real operating conditions of the Sinem GPP (on 14 April 2013). The \(n\)-pentane with 82 \({}^{\circ}\)C and 150 kPa emerging from TURB 1 is then sent to the recuperator RECUP (at point 13). If the \(n\)-pentane emerging from the turbine still carries high energy, this high energy is stored in RECUP and later is used to transfer to \(n\)-pentane coming from the pump PU 1. The \(n\)-pentane coming from RECUP enters the air-cooled condenser CON 1 at lower temperature of 60 \({}^{\circ}\)C (at point 14). The air-cooled condenser CON 1 lowers the temperature of the \(n\)-pentane to 31 \({}^{\circ}\)C and 150 kPa (at point 15) to produce liquid, and this passes to pump PU 1. The \(n\)-pentane is pumped at 1261 kPa pressure from PU 1 to the recuperator RECUP (at point 16) and regains the previously stored heat in RECUP to increase the temperature. Thus the efficiency of the heat exchangers PREHE 1 and VAP 1 acting as evaporators is increased. The \(n\)-pentane heated by RECUP is sent to the pre-heater PREHE 1 (at point 17) and from there to the vaporizer VAP 1 again (at point 11). Thus the organic Rankine cycle returns to the start and this continues repeatedly. To increase the efficiency of the GPP, this works in coordination with another ORC (level II). As shown in Figure 2b and Table 1, the \(n\)-pentane heated in VAP 2 on level II has 109 \({}^{\circ}\)C and 687 kPa pressure (at point 19) and is sent to rotate the turbine TURB 2 as superheated steam. Later, different to level I, the \(n\)-pentane is sent to the air-cooled condenser CON 2 at 69 \({}^{\circ}\)C temperature (at point 20). From the air-cooled condenser CON 2, the \(n\)-pentane is sent to the pump PU 2 at 33 \({}^{\circ}\)C and 119 kPa (at point 21) as liquid. In pump PU 2, the \(n\)-pentane pressure has risen to 687 kPa and is pumped to pre-heater PREHE 2 (at point 22).