## 2 Materials and Methods
### Experimental Tests
A hollow sleeve was placed in the place where the sensor was located during the cooling tests. The diameter of this sleeve was the same as the diameter of the cylindrical probe (20 mm), so the size of the area from which the water was drained corresponded to the area of the cylindrical probe that was used in the cooling tests. Water entering the sleeve during cooling was collected by a rubber hose which was connected to a measuring cylinder (Figure 8). The volume of water hitting the cooled surface during the measurement (\(V\)) was read from the graduated scale of the measuring cylinder. The time at which water was drained into the measuring cylinder (\(\tau_{w}\)) was also measured. Water volume measurements were repeated six times for each type of cooling system and each set of cooling parameters. The example results of the measurements conducted for the AAS system at a pressure of 0.2 MPa are presented in Figures 9 and 10. Based on the collected data, the average water flux density falling on the cooled surface was determined using Equation (1):  
\[g_{w}=\frac{\sum_{w=1}^{w=6}\frac{1}{\pi R^{2}}\Big{(}\frac{V}{\tau_{w}}\Big{)}} {6} \tag{1}\]  
where  
\(R\)--cylinder radius, m;  
\(V\)--volume of the water collected in the measuring cylinder, m\({}^{3}\);  
\(\tau_{w}\)--time of collection of the water in the measuring cylinder, s.  
The average values of the water flux density for all three cooling systems are summarized in Table 2. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Type of Cooling** & **Pressure, MPa** & **Total Cooling Time, s** &
\begin{tabular}{c} **Initial Temperature of** \\ **the Sensor, \({}^{\circ}\)C** \\ \end{tabular} \\ \hline JET & 0.05 & 70 & 895 \\  & 0.1 & 80 & 895 \\  & 0.2 & 80 & 895 \\ \hline WS & 0.05 & 80 & 893 \\  & 0.1 & 80 & 896 \\  & 0.2 & 65 & 891 \\ \hline AAS & 0.05 & 80 & 903 \\  & 0.1 & 80 & 898 \\  & 0.2 & 80 & 900 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Cooling parameters adopted for numerical calculations. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Type of Cooling** & **Pressure, MPa** & \begin{tabular}{c} **Average Water Flux** \\ **Density, m\({}^{3}\)/(m\({}^{2}\)-s)** \\ \end{tabular} & \begin{tabular}{c} **Accuracy of the Water Flux** \\ **Density Measurement \(\Delta g_{w}\)** \\ **m\({}^{3}\)/(m\({}^{2}\)-s)** \\ \end{tabular} & \
\begin{tabular}{c} **Relative Error of the Water** \\ **Flux Density Measurement** \\ **s\({}^{3}\)/(m\({}^{2}\)-s)** \\ \end{tabular} \\ \hline JET & 0.05 & 62.27\(\cdot 10^{-3}\) & 5.43\(\cdot 10^{-3}\) & 7.95 \\  & 0.1 & 95.86\(\cdot 10^{-3}\) & 8.67\(\cdot 10^{-3}\) & 9.04 \\  & 0.2 & 143.31\(\cdot 10^{-3}\) & 17.05\(\cdot 10^{-3}\) & 11.90 \\ \hline WS & 0.05 & 35.26\(\cdot 10^{-3}\) & 1.89\(\cdot 10^{-3}\) & 5.36 \\  & 0.1 & 43.72\(\cdot 10^{-3}\) & 2.43\(\cdot 10^{-3}\) & 5.56 \\  & 0.2 & 44.38\(\cdot 10^{-3}\) & 2.83\(\cdot 10^{-3}\) & 6.38 \\ \hline \hline \end{tabular}
\begin{tabular}{c c c} AAS & 0.05 & 21.38\(\cdot 10^{-3}\) & 1.30\(\cdot 10^{-3}\) & 6.08 \\  & 0.1 & 28.24\(\cdot 10^{-3}\) & 1.63\(\cdot 10^{-3}\) & 5.77 \\  & 0.2 & 22.47\(\cdot 10^{-3}\) & 1.36\(\cdot 10^{-3}\) & 6.05 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The accuracy of water flux density measurements. Figure 8: System for measuring the amount of water. Figure 7: Scheme of the system for measuring the amount of water: 1—nozzle, 2—hollow sleeve, 3—rubber hose, 4—feeder, 5—cooling chamber, 6—measuring cylinder. Figure 9: The volume of water collected in a measuring cylinder at times (\(\tau_{w}\)) during the six measurements, AAS, \(p\) = 0.2 MPa. The accuracy of the water flux density measurement may have been affected by the occurrence of the measurement errors results from the experimental procedure. The error in measuring the water flux density may have been related to the accuracy of the measurement of the volume of water collected in the measuring cylinder, the accuracy of the surface area of the sleeve used to collect the water, and the accuracy of the time measurements.