## 3 Results  
Figure 9 shows graphs of the average temperature in cooled places (under modules) and in uncooled places (next to modules) on both the chest and the shoulder blades. The greatest difference in the measured skin temperature between the cooled and uncooled places, amounting to 2.66 \({}^{\circ}\)C, was recorded on the back around the 24 th minute of the test. For the chest, the largest difference of 2.34 \({}^{\circ}\)C was recorded around the 44 th minute of the study and a difference of 2.25 \({}^{\circ}\)C around its 13 th minute. Qualitatively, the cooling effect was maintained throughout the entire study period. At the end of the study, the measured temperatures on the chest and the shoulder blades were approximately 1 \({}^{\circ}\)C lower than at the beginning. The measured temperature in the cooled place on the chest remained at a relatively similar level from about the 10 th minute of the test, ranging from 31.2 \({}^{\circ}\)C to 32.0 \({}^{\circ}\)C, which is close to the thermally neutral state and confirms that the system operated as intended. The statistical analysis showed that in the case of the chest, the temperature difference between the cooled and the uncooled place was statistically significant only in the 20 th minute of the test. For the back, statistically significant differences occurred at the 10 th, 15 th, 20 th and 25 th minutes of the test.  
\begin{table}
\begin{tabular}{c c} \hline
**Rating** & **Sensation** \\ \hline \(-3\) & cold \\ \(-2\) & cool \\ \(-1\) & slightly cool \\ \(0\) & neutral \\ \(1\) & slightly warm \\ \(2\) & warm \\ \(3\) & hot \\ \hline \end{tabular}
\end{table}
Table 2: Scale for the rating of overall thermal comfort [30].  
Figure 8: Research procedure phases.  
It is noteworthy that the local skin temperatures measured in places not directly cooled, i.e., next to the module, increased in the initial phase (up to approx. 25 min), but then they decreased. This is a very positive result, indicating that although thermoelectric modules collect heat from the human body locally, a cooling effect is also observed in other places.  
When the PCS was active, the average rating of the thermal sensations oscillated around the value of 0, mostly between \(-1\) and 1, corresponding to \"slightly cool\", \"neutral\", and \"slightly warm\" (Figure 10). The ratings given after the breaks (i.e., in the 25 th and the 45 th minute of the test) indicate an increased feeling of cooling and, thus, an improvement in thermal comfort. At these moments, the average ratings were the lowest obtained during the entire study.  
Figure 9: Measured local skin temperatures in cooled and uncooled places: (a) absolute; (b) normalized. \(\times\) indicates statistically significant differences at a significance level <0.05.  
The average resistance of the TEMs was determined to be 5.2 \(\Omega\). A single TEM current was therefore 0.54 A at maximum in the regulation phase, when the output power was 1.5 W per module, and 0.30 A in the standby phase. The respective voltage values were 2.9 V and 1.7 V, respectively. The input power from the powerbank was 11.40 W and 3.69 W, respectively. As mentioned in Section 2.1.2, the phase durations were equal, so the average power consumption was 7.55 W.