## 2 Design Aspects
#### 2.1.5 Cooling Cycle: Absorption  
The proposed chiller simulated here is the single-effect LiBr-H\({}_{2}\)O absorption chiller YAZAKI WFC-SC10 (Yazaki Energy Systems Inc., Plano, TX, USA) with a nominal coefficient of performance (COP) of 0.70 and nominal cooling capacity \(\dot{Q}_{e}\) of 35 kW. The technical specifications of the chiller are listed in Table 3[34]. For the analysis of facilities, we will always assume a maximum demand capable of being satisfied by this chiller to cover the cooling load (in our case the maximum demand will be 25 kW). The simulation program required data from the chiller catalog that describes the chiller's operating map in order to determine the operating variables. The absorption machines are usually characterized by two basic parameters:  
* COP nominal. COP\({}_{\text{nom}}\). (0.7 for Yazaki WFC-10, Yazaki Energy Systems Inc., Plano, TX, USA)
* \(\dot{Q}_{e}\) Nominal evaporator power \(\dot{Q}_{e,nom}\). (35 kW for Yazaki WFC-10, Yazaki Energy Systems Inc., Plano, TX, USA)  
From these, the nominal generator power \(\dot{Q}_{g,nom}\) is immediately available by simply dividing the nominal cooling power \(\dot{Q}_{e,nom}\) by the nominal coefficient of performance COP\({}_{\text{nom}}\). The TRNSYS model also requires entering the target temperature to be obtained at the outlet of the evaporator \(T_{e,set}\), as well as the temperatures and flows entering the three external circuits: evaporator \(T_{ei}\), condenser \(T_{ci}\) and generator \(T_{gi}\). In this way, the model can determine the load regime in which the chiller works. Under these conditions, two situations can occur: if there is sufficient output power available on the evaporator, the set temperature will be reached. If not, the lowest possible value will be reached with the available power. The instant heat \(\dot{Q}_{remove}\) that should be removed from the incoming flow of the child as well as the load fraction \(f_{Load}\) are determined by Equations (6) and (7). \[\dot{Q}_{remove}=\dot{m}_{e}C_{p,e}(T_{ei}-T_{e,set}) \tag{6}\] \begin{table}
\begin{tabular}{c c c} \hline \hline
**Characteristics** & **Value** & **Units** \\ \hline Cooling tower capacity & 105 & kW \\ \hline Wet temperature & 25 & \({}^{\circ}\)C \\ \hline Cooling water temperature & 35-30 & \({}^{\circ}\)C \\ \hline Airflow rate & 16 & m\({}^{3}\)/h \\ \hline Electrical power & 0.75 & kW \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Technical characteristics of the FXT-26 cooling tower [32]. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Characteristic** & **Unit** & **Value** \\ \hline Cooling capacity & kW & 35 \\ \hline Chilled water outlet /inlet temp. & \({}^{\circ}\)C & 7/12.5 \\ \hline Cooling water outlet /inlet temp. & \({}^{\circ}\)C & 35/31 \\ \hline Heating water outlet /inlet temp. & \({}^{\circ}\)C & 88/83 \\ \hline Chilled water flowrate & m\({}^{3}\)/h & 11 \\ \hline Cooling water flow rate & m\({}^{3}\)/h & 36.7 \\ \hline Heating water flow rate & m\({}^{3}\)/h & 17.3 \\ \hline Electric power consumption & kW & 0.21 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Specifications of the YAZAKI WFC-SC10 absorption chiller [34]. \[f_{Load}=\frac{\dot{Q}_{remove}}{\dot{Q}_{e,nom}} \tag{7}\]  
With the load fraction and the temperatures indicated above (set, evaporator, condenser, and generator) it is possible to access the configuration file, whose structure will be commented on later, and which has been made from the chiller operation curves offered by the manufacturer for a set of operation points, establishing two basic parameters:  
* Fraction capacity \(f_{capacity}\): is the ratio of the evaporator's output power to the nominal power of the chiller. With the manufacturer's data for each of the established operating points, the quotient between the output power it has in each of these conditions and the nominal power of the evaporator is evaluated.