## 8 Application Case
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Section and Stream** & **Parameter** & **Notes** \\ \hline \multirow{3}{*}{Heat source} & \multicolumn{2}{c}{30 \({}^{\circ}\)C (pre-heating)} \\  & Temperature & 50–60 \({}^{\circ}\)C (Air) \\  & & 50–80 \({}^{\circ}\)C (Water) \\  & Mover & Blower \\  & \(\Delta\)T pinch-point & \(\sim\)10 \({}^{\circ}\)C \\  & Mass flow rates & Calibrated through tests \\ \hline Condensing water & Temperature & 10 \({}^{\circ}\)C \\  & Mass flow rate & Calibrated through tests \\  & Mover & Pump \\ \hline ORC fluid & Pentane and isopentane & \\  & Mass flow rate & 1 kg/s \\  & Max pressure & Calibrated through tests \\  & Min pressure & Calibrated through tests \\ \hline Models & \multicolumn{2}{c}{Soave–Redlich–Kwong Advanced (air)} \\  & Peng–Robinson 1978 Advanced (ORC fluid) & \\  & Steam Tables IAPWS-IF97 (water) & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Calculation settings. Figure 3: Validation of the proposed numerical model. Comparison with literature data in terms of specific work (**a**) and cycle efficiency (**b**). expander dedicated to energy generation while reducing and bringing the pressure back to the initial level. The heat provision is attributed to the chain of heat exchanger PRE-HEAT/ECO/EVA/SUP-HEAT, where the pre-heating of the ORC fluid and its evaporation occurs, while the cooling and condensation processes take place in the chain DE-SH/COND/L-COOL. Ambient water is used for condensation. Table 4 includes the calculation setting of the ORC system. As previously mentioned, primary heat source temperatures range between 50 and 80 \({}^{\circ}\)C when using water and between 50 \({}^{\circ}\)C and 60 \({}^{\circ}\)C when using air. An additional air mass flow rate at 30 \({}^{\circ}\)C is for pre-heating purposes. The condensing water is at an underground temperature of 10 \({}^{\circ}\)C. The ORC system operates with a 1 kg/s mass flow rate, and iterative tests define the upper and lower pressure limits. This procedure also applies to the air-evaporating and water-condensing mass flow rates. Given the broad range of ORC working fluids suitable for low temperatures, the selection narrows significantly under imposed temperature limits, such as the evaporation temperature, which needs to align with the thermal resource, and the condensation temperature, which needs to be compatible with the cold-water resource. With these constraints, the focus has shifted towards pentane and isopentane as working fluids. The selection of these fluids is guided by insights from the reference literature, highlighting their suitability for efficient low-grade waste heat recovery [1; 100; 101] and low environmental impact [74; 102]. The corresponding zero ozone depletion potential (ODP) and low global warming potential (GWP) represent fundamental factors in promoting the transition toward clean data centers. Based on the previous configurations, simulations are conducted in the DWSIM computational environment. The focus is on calculating a comprehensive set of thermodynamic parameters, including pressure, temperature, mass density, enthalpy, entropy, and the fractions of liquid and vapor, as well as energy parameters such as input and output power. Figure 5 displays the results for the ORC system using pentane as the working fluid, whereas Figure 6 pertains to isopentane. Each figure consists of the thermodynamic cycle (a), a chart presenting pressures, pressure ratios, and system efficiency (b), a chart reporting evaporation and condensation temperatures and net energy (c), the mass ratios between the heat source and the ORC fluids, and the condensation water and the ORC fluids (d). Figure 4: System layout simulated in DWSIM environment. For pentane, the evaporation temperatures achieved are 45.8 \({}^{\circ}\)C and 74.2 \({}^{\circ}\)C, corresponding to hot liquid water temperatures of 50 and 80 \({}^{\circ}\)C, respectively.