In the case of an open heating coil with the beginning of the welding process the transfer of heat to the pipe is in the form of heat radiation and convection air currents caused by the different levels of temperature in the contact zone. Although air, like PEX, is a poor conductor of heat, but the distances between the coupling and pipe less than 0,1 mm the heat transfer plates occurs almost instantly.
This can be easily traced in the experiment: if you put his finger to a distance of about 1 mm to the heat source, for example, included a plate, not touching her at the same time, the relativity of the term “air – a poor conductor of heat” becomes apparent. Of course, this expression is correct in comparison with substances such as steel and water. Yet relatively little difference between these substances, especially between the liquid PEX to air (Table 2), becomes apparent only when compared to the heat.
