## 5 Experimental Tests Results, and Discussion
### Effect of Fan Speed  
The inlet air flow rate of the fans, attached to the top and bottom channel (see Figure 3), is also one of the important parameters which affect the cooling effect. For the beginning, the applied current is kept constant at 4 A, and fan speed varies at different values. The graph of various fan speeds is plotted in Figure 9.  
It can be observed from Table 5 that the cooling effect is not significant as the fan speed increases. The temperature is almost constant at the maximum fan speed. Furthermore, the temperature distribution inside the closed room did not show any significant change in the temperature. The reason behind high temperature is that as the airflow rate increases, it is not getting enough time to contact the cold surface, so to improve the cooling effect of the system, an appropriate inlet airflow is required, which can be measured by the trial-and-error method. It was observed that 58% temperature rose when the airflow rate increased from 2.35 m/s to 3.55 m/s. However, for the bulk mean temperature, it can be observed from the graph that there is no significant effect at different inlet airspeeds. It is clear from Figure 10 that the bulk mean temperature is almost similar at the different fan speeds. Initially, the temperature rises, and after that, it falls and remains constant for the rest of the time. Figure 8: Temperature distribution by copper tube fin heat exchanger inside the closed room at various input current to the TEC module. Figure 10: Bulk mean temperature at various inlet air flow rate. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Time (s)** & **2.35 m/s** & **2.55 m/s** & **3.55 m/s** \\ \hline
5000 & 13.4 \({}^{\circ}\)C & 15.6 \({}^{\circ}\)C & 19.3 \({}^{\circ}\)C \\
10,000 & 11.3 \({}^{\circ}\)C & 15.4 \({}^{\circ}\)C & 19.5 \({}^{\circ}\)C \\
15,000 & 10.7 \({}^{\circ}\)C & 14.9 \({}^{\circ}\)C & 19.6 \({}^{\circ}\)C \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Temperature values at various inlet air flow rate. Figure 9: Effect of various inlet air flow rate on the final cooling temperature. The overall heat removal rate from the hot side of the cold plate is plotted in Figure 11.  
It can be observed from the graph that the heat removal rate increases with increases in the fan speed. Furthermore, as the fan speed increase from 2.25 to 3.55 m/s the heat removal rate from the hot side of the cold plate is increases from 230 to 283 W at 5000 s, which shows 20% increment in the heat removal rate with an increase in the fan speed. Figure 12 shows the heat removal rate from the cold side of the cold plate as a function of the time. It also follows the same pattern from the hot side of the cold plate. The heat removal rate increases with an increase in the fan speed. The heat generated by the cold plate is removed rapidly as the fan speed increase. At the beginning of the experiment, the heat removal rate increases as time goes; however, after a certain time, it will remain constant. Moreover, the heat removal rate increases from 127 to 179 W as the fan speed increases at 5000 s, indicating an increment of 33% on the heat removal rate from the cold side. Furthermore, to investigate the system's performance, the COP graph is plotted, and from the graph, it can be observed that the graph follows the same pattern as shown in the above graphs for the heat removal rate. The COP of the system is plotted as a function of time in Figure 13. The COP is calculated using Equation (10) mentioned in the mathematical model section. It is observed that the COP of the system increases from 1.23 to 1.74 as the fan speed is increased from 2.25 to 3.55 m/s. The COP of the system largely depends upon the heat removal rate and cooling effect generated by TEC modules, so as the heat removal rate increases, the cooling effect generated by the TEC module also increases, improving the performance of the system. As the fan speed increases from 2.25 to 3.55 m/s, the COP shows an approximately 34% increase in the system performance.