## 2 Methodology
### Experimental Bench  
The logical model developed was tested in an experimental bench before being deployed in an ammonia refrigeration system. The main purpose was to identify patterns of variations of condensation head pressure and its relationship with other variables, allowing for the modulation of the mass flow rate of air in the evaporative condenser (EC). The experimental bench consisted of a refrigeration system of vapor compression that uses R-22 as a refrigerant working fluid operating in the laboratory. R-22 was choose as the refrigerant fluid due to its lower toxicity in comparison to R-717, together with its low corrosion potential to the evaporative condenser tubes, which are made of copper. A schematic configuration of that bench is shown in Figure 1. It consisted of a unit of an air conditioner with a capacity of 2.2 kW. The unit was composed of a hermetic alternative compressor model, with demanded power of 0.186 kW, a capillary tube, one evaporator with forced ventilation, an evaporative condenser on a reduced scale of one-fourth in comparison with a commercially produced model [18], one VFD model CFW10 easydrive, and one programmable logic controller (PLC) where logical control modeling was implemented. It is worth mentioning that this was previously used in the study of [PERSON] and [PERSON] [18]. Figure 1: Schematic representation of the experimental bench. The measurement data of some variables of the refrigeration system were directly connected with the PLC, which provides the read and storage of the quantities in a database created for this purpose. These data were collected continuously with a defined time interval between readings. The measurement points and the respective information collected are shown in Figure 1. Point 1 represents the location where the condensation pressure (\(P\) in bar) and R-22 temperature (\(T\) in \({}^{\circ}\)C) measurements are made at the inlet of EC, while Point 2 depicts the pressure (\(P\) in bar) measurement of R-22 leaving the EC. Points 3 and 4 represent R-22 at the inlet and outlet airflow rates of the EC, respectively, where the velocity (\(V\) in m/s), dry bulb temperature (\(T_{\text{DB}}\) in \({}^{\circ}\)C), and relative humidity (\(U\)R in %) measurements are realized. At Point 5, the volumetric flow rate (\(Q\) in m\({}^{3}\)/s) of the water is measured, while at Point 6, the sump temperature (\(T\) in \({}^{\circ}\)C) is acquired. Temperature measurements of the water and R-22 were performed by PT-100 sensors with an uncertainty of \(\pm\)0.1 \({}^{\circ}\)C. The dry bulb temperature (\(T_{\text{DB}}\)) and wet bulb temperature (\(T_{\text{WB}}\)) of the airflow rate at the inlet and outlet EC were measured by an HT-270 thermoyrometer with an uncertainty of \(\pm\)0.8 \({}^{\circ}\)C for temperature and 4.0% of the measured value for relative humidity. The air velocity was measured by an anemometer with an uncertainty of \(\pm\)0.1 m/s. The uncertainty of the R-22 pressure measurements was 0.067 bar. Concerning the energy consumption, one analyzer of energy with an uncertainty of \(\pm\)1.0% of the measured value was considered. The same measurement equipment used to collect information in the experimental bench of R-22 refrigeration system were employed for measurements of the ammonia industrial refrigeration unit. In this study, we did not analyze the relation between the inlet temperature of the air in the EC and the performance of the refrigeration unit. Initially, experiments were performed by changing the mass flow rates of the air through the EC and systematically varying the frequency driver of the fan with 5 Hz steps in the range of 10 Hz \(\leq\)\(f\)\(\leq\) 50 Hz. When the frequency changed for a new value, this magnitude was kept constant until the refrigeration system reached a stable condition; in such way the measurements were calculated with a higher accuracy. It is worth mentioning that only the frequency was kept constant during this time interval, with the remaining variables free to vary.