## 8 Application Case  
This paragraph aims to complete the analysis by presenting an application case for an ORC energy system using the waste heat deriving from data center cooling as a heat source. For this purpose, modeling is carried out in the DWSIM environment. The system is scrupulously designed through a series of iterative tests, calibrating, if necessary, the heating flows, responsible for the evaporation of the organic fluid, and the cooling flows, responsible for condensation. The model defines the minimum flow rates required to establish the energy cycle. The evaporation and condensation processes of the ORC fluid are delicate, as already known. The critical aspects concern (1) the ability to evaporate the fluid with hot air or liquid at the available temperatures and (2) the ability to condense with available natural resources such as ambient water. Therefore, the limit temperatures depend on the waste heat level of the data centers and water from the distribution circuit or any available well. Within these boundaries, each organic fluid responds as a function of its thermophysical capabilities, i.e., a more or less high maximum evaporation pressure and a more or less low condensation pressure, which imposes the condensation temperature. Preliminary model validation has been performed with literature data [99] referring to ORC systems to harness geothermal sources in Southern Italy. The same subcritical regenerative configuration is recreated in the DWSIM computational environment, using isopentane as the working fluid and maintaining consistent operating conditions. The analysis illustrates that the proposed model well characterizes the ORC performance. As an example, Figure 3 compares literature data and model results in terms of specific work (Figure 3a) and thermal efficiency (Figure 3b) as a function of the evaporation temperature. The percentage differences range between 0.6% and 1.4% for all the investigated conditions and parameters, indicating the accuracy of the proposed ORC model. This validation process serves as a demonstrated robust tool for conducting simulations. Based on the preparatory analyses conducted, it is plausible to consider a data center with an average power density of at least 10 \(\mathrm{kW/m^{2}}\). Two flow streams provide heat to the ORC system. One flow is pertinent to the ultra-low temperature of air (LT-AIR), tasked with cooling the data center rooms, characterized by an outlet temperature of approximately 30 \({}^{\circ}\)C, to pre-heat the ORC organic fluid. The second flow at high temperature (HT-FLOW) is responsible for the evaporation. For this purpose, the investigations consider a scenario involving forced air and another with liquid water. Specifically, the liquid water is assumed to return from the conditioning unit with temperatures ranging between 50 and 80 \({}^{\circ}\)C [12; 31]. On the other hand, the forced air presents an output temperature range of 50-60 \({}^{\circ}\)C [12; 31] (Table 4). In envisioning the system design, ducts leading from the pumped hot water and air blower to the heat exchanger represent a feasible approach (then acting as the heat source for the organic Rankine energy system). The ORC plant is engineered as depicted in Figure 4. It responds to the Rankine scheme, including the pre-heating and evaporation section, the condensation part, the pump for fluid pressurization and circulation, and the