## 3 Results and Discussion
### Comparison of Average Values of HTC and HF on the Cooled Surface  
The assessment of the amount of energy dissipating from the \(A_{1}\) and \(A_{2}\) surfaces presented in Figures 19-22 was made based on the results of HTC and HF variations. On the presented boiling curves, the first phase of boiling, which is the film-boiling regime, is not observed. The reason for the absence of film-boiling is the high velocity of the liquid falling on the cooled surface and the small distance between the nozzle and the cooled surface. The high velocities of the liquid can prevent the formation of a vapor film which insulates the surface from the liquid. On the boiling curves, only two phases of boiling are observed. In the initial stage of the cooling, a transition boiling occurs. In this phase, a rapid increase in HTC and HF is observed, which continues until the maximum values are reached. After reaching the maximum values, HTC and HF decrease, which is caused by the occurrence of disappearing in time process of nucleate boiling. When the surface temperature drops below 100 \({}^{\circ}\)C, forced single-phase convection occurs on the cooled surface. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{1}{c}{**No.**} & \multicolumn{1}{c}{**Type of Cooling**} & \multicolumn{1}{c}{**Pressure, MPa**} & \multicolumn{1}{c}{
\begin{tabular}{c} **Average Error of Temperature** \\ **Calculations, K** \\ \end{tabular} } \\ \hline
1 & & 0.05 & 0.1 \\
2 & JET & 0.1 & 0.5 \\
3 & & 0.2 & 0.9 \\ \hline
4 & & 0.05 & 0.3 \\
5 & WS & 0.1 & 0.6 \\
6 & & 0.2 & 0.4 \\ \hline
7 & & 0.05 & 0.9 \\
8 & AAS & 0.1 & 0.5 \\
9 & & 0.2 & 0.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The accuracy of the numerical calculations. Figure 18: Comparison of the temperature changes between the measured and calculated temperatures, JET, \(p=0.1\) MPa. For each considered cooling system, the increase in the pressure of the supplied medium caused higher values of HTC and HF. The increase in water pressure caused an increase in the cooling water flux density and the cooling intensity. Such a dependence, for the cooling systems analyzed in this paper, was confirmed by many studies that are presented in the literature [47, 48]. [PERSON] and [PERSON] [49] indicated that the increase in droplet velocity results in a significant increase in the heat transfer coefficient during spray-cooling. The analysis of the literature showed that the work on comparing different cooling systems by describing the variability in heat transfer was carried out to a limited extent. In the paper of [PERSON] and [PERSON] [12], the results of the study of the variation in the heat transfer coefficient for different cooling systems related to a surface of which the temperature was above the Leidenfrost temperature are presented. The highest HTC  
Figure 19: Comparison of the change in average HTC values from the surface temperature (**A**) and time (**B**) during cooling using three systems of cooling, \(A_{1}\). Figure 20: Comparison of the change in average HF values from the surface temperature (**A**) and time (**B**) during cooling using three systems of cooling, \(A_{1}\). values were obtained for AAS cooling. However, in the literature, there is a lack of results comparing the magnitude of the energy dissipating in the entire boiling range. In the presented paper, the results of the investigations performed for the three cooling systems in which the hot plate was cooled from the initial temperature of 900 \({}^{\circ}\)C to 60 \({}^{\circ}\)C are presented. The assumptions of the experimental conditions were identical for all experiments, which include the water pressure and distance between the nozzle and the cooled surface. The results of the average HTC and HF variation in \(A_{1}\) surface versus temperature and time are shown in Figures 19 and 20, respectively. The comparison of the results of the calculations indicates that the highest values of HTC were obtained for the WS cooling system for water pressure \(p=0.2\) MPa.