## 4 Discussion  
The conducted laboratory tests confirmed that some of the electric power supplied to the module is released in the form of heat and the nature of this relationship is unfavorable. The heat flux released to the environment is the sum of the heat flux corresponding to cooling and the heat dissipated in the TEG module due to its operation. The power supplied and dissipated in the module grows faster than the heat flux; therefore, the higher the heat flux to be transferred, the greater the share of the heat flux generated by the module itself. As a result, above a certain value of electric power (depending on the heat sink used), the heat flux that can be received from the \"skin model\" heating plate is reduced, which is manifested in the refraction of the heat flux characteristics in the EP variant (i.e., for the polymer TEGway heat sink) visible in the graph (Figure 8). It is expected that a similar breakdown will also occur for the remaining heat sinks but for different (higher) current values. For even higher current values, the power dissipated in the module becomes greater than the heat flux through the module so that the direction of heat flow is reversed, i.e., a heating effect can be observed instead of cooling. In this situation, the measurement on the  
Figure 11: Electric power as a function of the ambient temperature for different heat sink elements, in non-isothermal conditions, for I = 0.25 A: error bars correspond to standard deviation; \"\" marks the statistically significant difference for \(p\) = 0.05.  
testing stand becomes impossible because the \"skin model\" does not allow the absorption but only the emission of heat to the environment.  
It should be mentioned that the test stand used in this research has some additional limitations. The \"skin model\" is a flat plate, so it is impossible to include a bending effect that may potentially occur in a real application in clothing. Moreover, the tested object is placed on the measuring plate horizontally, while it would rather be oriented vertically in clothing. Therefore, a reduction in the contact surface and, as a consequence, heat removal by conductivity may occur in such conditions. In addition, the principle of operation of the \"skin model\" is to keep the measuring plate temperature constant by regulating the electric power supplied to it. This means that no change of plate temperature due to the local cooling provided by the thermoelectric module could be observed. All those factors may influence the obtained results in relation to a real application. However, at the same time, the use of the same testing methodology for all the variants selected for the research permitted their reliable comparison and the selection of the most promising one for integration with clothing.  
The best results in terms of the amount of received heat flux were achieved with the use of the TEGway polymer heat sink; however, a gradual reduction in the absorption capabilities of this type of heat sink was observed during the tests. This was most likely due to the successive outflow of the moisture-absorbing substance during the soaking of the element. Therefore, the development of own heat sink seems to be the right direction of research in order to ensure both the efficiency of heat dissipation from the module and the durability of the solution during use. However, due to the intended use of the cooling system in clothing, it would be advantageous if the heat sink did not require additional processing to ensure its intended function (in this case, soaking).  
As a result of the laboratory tests, it is also possible to observe a significant influence of the ambient temperature on the effectiveness of the tested variants in removing heat from the heating plate. As the temperature difference between the heating plate and the surroundings decreased, the heat flux transferred by the module decreased; however, even in isothermal conditions for heat sinks using the evaporation effect, the heat flux was about 1 to 1.5 W.