## 3 Important Parameters
### Absorption Cooling System  
The mathematical model for determining the thermal powers to be transferred in the main components of the absorption cooling system, was a first-law thermodynamic model, which was based on the Equations (11) to (30) (see Figure 2 for a subscripts reference). \[T_{1}=T_{12}-10\ ^{\circ}\mathrm{C}=T_{8} \tag{11}\]  
\[T_{2}=T_{14}+10\ ^{\circ}\mathrm{C} \tag{12}\]  
\[P_{2}=P_{sat@T2}=P_{6}=P_{7}=P_{8}=P_{9}=P_{1} \tag{13}\]  
\[T_{4}=T_{15}-10\ ^{\circ}\mathrm{C} \tag{14}\]  
\[P_{4}=P_{sat@T4}=P_{5}=P_{10}=P_{3} \tag{15}\]  
\[T_{5}=T_{18}+10\ ^{\circ}\mathrm{C} \tag{16}\]  
\[X_{5}=f(T_{5},\ P_{5}) \tag{17}\]  
\[h_{5}=h_{f@T5}\ y\ P_{5} \tag{18}\]  
\[v_{5}=v_{f@T5}\ y\ P_{5} \tag{19}\]  
\[\dot{W}_{p}=v_{5}(P_{6}=P_{5}) \tag{20}\]  
\[T_{2}=T_{14}+10\ ^{\circ}\mathrm{C} \tag{12}\]0  
\[T_{2}=T_{14}+10\ ^{\circ}\mathrm{C} \tag{12}\]1  
\[T_{2}=T_{14}+10\ ^{\circ}\mathrm{C} \tag{12}\]2\[T_{2}=T_{14}+10\ ^{\circ}\mathrm{C} \tag{12}\]3  
\[T_{2}=T_{14}+10\ ^{\circ}\mathrm{C} \tag{12}\]4  
\[T_{2}=T_{14}+10\ ^{\circ}\mathrm{C} \tag{12}\]5  
\[T_{2}=T_{14}+10\ ^{\circ}\mathrm{C} \tag{12}\]6  
\[T_{2}=T_{14}+10\ ^{\circ}\mathrm{C} \tag{12}\]7  
\[T_{2}=T_{14}+10\ ^{\circ}\mathrm{C} \tag{12}\]8  
\[T_{2}=T_{14}+10\ ^{\circ}\mathrm{C} \tag{12}\]9  
The external coefficient of performance (\(COP_{ext}\)) for the absorption cooling system can be determined using Equation (31):  
\[P_{2}=P_{sat@T2}=P_{6}=P_{7}=P_{8}=P_{9}=P_{1} \tag{13}\]0  
In Equation (31), \(\dot{Q}_{e,ext}\) represents the cooling power transferred from the water flowing in the evaporator and it is determined, as it is established by Equation (32). \[P_{2}=P_{sat@T2}=P_{6}=P_{7}=P_{8}=P_{9}=P_{1} \tag{13}\]1  
\(\dot{Q}_{g,ext}\) is the thermal power supplied by the heating water in the generator and is calculated, as Equation (33) indicates. \[P_{2}=P_{sat@T2}=P_{6}=P_{7}=P_{8}=P_{9}=P_{1} \tag{13}\]2  
Finally, the term \(\sum\dot{W}_{p,ext}\) involves the power required to operate the pumps in each external system, such as the solar or the auxiliary heating system, auxiliary cooling system, and the system of the water to be chilled. This term is determined considering three different types of pressure drop inside the plate heat exchangers: friction (\(\Delta P_{f}\)), gravity (\(\Delta P_{gra}\)), and flow distribution in the PHE channels (\(\Delta P_{N}\)). These terms are calculated, as shown below. \[P_{2}=P_{sat@T2}=P_{6}=P_{7}=P_{8}=P_{9}=P_{1} \tag{13}\]3  
where:  
\[P_{2}=P_{sat@T2}=P_{6}=P_{7}=P_{8}=P_{9}=P_{1} \tag{13}\]4  
\[P_{2}=P_{sat@T2}=P_{6}=P_{7}=P_{8}=P_{9}=P_{1} \tag{13}\]5  
\[P_{2}=P_{sat@T2}=P_{6}=P_{7}=P_{8}=P_{9}=P_{1} \tag{13}\]6  
An important criterion in the assessment of any ACS is the \"flow ratio\" (FR) which is a dimensionless measure of the rate of refrigerant produced relative to the mass flow rate of concentrated solution pumped from the absorber to the generator, this parameter is determined as indicated by Equation (38). \[P_{2}=P_{sat@T2}=P_{6}=P_{7}=P_{8}=P_{9}=P_{1} \tag{13}\]7The exergy efficiency for the absorption cooling system was determined from the Equation (39):  
\[P_{2}=P_{sat@T2}=P_{6}=P_{7}=P_{8}=P_{9}=P_{1} \tag{13}\]8  
The exergy rates in the evaporator \(\dot{X}_{e}\) and generator \(\dot{X}_{g}\) are determined from a general balance of exergy applied to the mass flow rates of water in both components. The general balance of exergy in steady-state conditions, disregarding the changes of potential and kinetic exergies, as well as mechanical work interactions, is presented in Equation (40). \[P_{2}=P_{sat@T2}=P_{6}=P_{7}=P_{8}=P_{9}=P_{1} \tag{13}\]9  
The term \(I\) in Equation (40) is the irreversibility, and it is calculated, as is indicated by Equation (41):  
\[T_{4}=T_{15}-10\ ^{\circ}\mathrm{C} \tag{14}\]0  
where \(S_{gen}\) represents the entropy generated during the heat transfer process, and can be obtained from an entropy balance applied to the system of interest.