## 4 Results and Discussion
### Heat Recovery
#### 4.2.2 Heat Recovery for 20 \({}^{\circ}\)C Coolant Temperature  
The consumed and recovered energy measurement values of drilling process performed by setting the heat recovery system to 20 degrees are given in Table 7. The total consumed energy and recovered energy values found using these values are shown graphically in Figure 13.  
Table 8 presents the variance analysis results of the S/N ratios for heat recovery in the drilling process at a coolant temperature of 20 \({}^{\circ}\)C. The analysis was conducted with a precision level of 94.04%. The values in the '\(p\)' column highlight the influence of each parameter on heat recovery. From the data in the Table, it is evident that the emulsion rate has the most significant impact on heat recovery, with a \(p\)-value of 0.071.  
Figure 14 illustrates the S/N analysis results for heat recovery. The graph identifies the optimal levels of parameters based on the highest signal-to-noise ratio. For a temperature setting of 20 \({}^{\circ}\)C, the optimal values are as follows: an emulsion ratio of 7.5%, a feed rate of 0.04 mm/rev, and a spindle speed of 663 rpm. Moreover, analyzing the range between the maximum and minimum S/N ratios for each parameter highlights the most influential factor, with the emulsion ratio emerging as the dominant parameter. This observation aligns well with the findings obtained from the variance analysis.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline
**Source** & **DF** & **Seq SS** & **Adj SS** & **Adj MS** & **F** & **\(p\)** \\ \hline Emulsion Ratio & 2 & 167.312 & 167.312 & 83.6560 & 13.17 & 0.071 \\ Feed rate & 2 & 0.342 & 0.342 & 0.1708 & 0.03 & 0.974 \\ Spindle Speed & 2 & 32.711 & 32.711 & 16.3557 & 2.57 & 0.280 \\ Residual Error & 2 & 12.704 & 12.704 & 6.3520 & & & \\ Total & 8 & 213.069 & & & & & \\ \hline \end{tabular}
\end{table}
Table 8: Analysis of variance for S/N ratios.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline
**Source** & **DF** & **Seq SS** & **Adj SS** & **Adj MS** & **F** & **\(p\)** \\ \hline Emulsion Ratio & 2 & 167.312 & 167.312 & 83.6560 & 13.17 & 0.071 \\ Feed rate & 2 & 0.342 & 0.342 & 0.1708 & 0.03 & 0.974 \\ Spindle Speed & 2 & 32.711 & 32.711 & 16.3557 & 2.57 & 0.280 \\ Residual Error & 2 & 12.704 & 12.704 & 6.3520 & & & \\ Total & 8 & 213.069 & & & & & \\ \hline \end{tabular}
\end{table}
Table 9: Heat recovery for 20 \({}^{\circ}\)C coolant temperature.  
Figure 14: Energy recovery S/N analysis graph.  
Figure 13: Consumed total energy and recovered energy for 20 \({}^{\circ}\)C coolant temperatures.  
The developed system has significant advantages. One of the biggest advantages of the system is that it increases energy efficiency by recovering waste heat and makes this energy usable in useful areas such as workshop heating or hot water production. Experimental data show that the energy consumption of the system is low and the recovered energy is more than the energy consumed by the system. For example, in the results presented in this study, it was observed that the coefficients of performance (COPs) indicating the energy efficiency of the system are quite high. In addition, keeping the coolant at a constant and appropriate temperature extends the life of the cutting tool and increases the processing quality. This provides cost savings by reducing coolant consumption and tool change frequency. In addition, the economic feasibility of the system was analyzed and it was determined that the amortization period was quite short. Thanks to these features, the developed system does not remain only an academic innovation but also has high potential in commercial terms. In this context, a patent was obtained to protect the innovative structure of the system and to commercialize it (Patent No: 201922131). Therefore, this system offers an effective solution for sustainable production both environmentally and economically and also attracts attention with its industrial applicability and market potential.