On the Polish version of this page I tried to explain what is radiative heat transfer and why it plays a significant role at flame temperatures. Essential picture is below. I hope it is self-explanatory.
Below is a link to video showing the flame in a hot environment. I have observed similar situation in my tests, but I don’t have a nice video. It is a pellet boiler made by the user of forums muratordom.pl and info-ogrzewanie.pl with the nickname zorzk7. Its design is based on rocket stoves. The vertical channel is somewhat oversized in relation to the power and therefore it is hot only in the lower part, which we observe from the top. In order to improve the purity of combustion, the constructor tested various turbulators and the movie presents the final shape. It is possible to have doubts about the significant escape of heat by radiation sent to the viewer, but the appearance of the flame and the lack of smell (according to the description by constructor) indicate good quality of combustion. I recommend watching the video in slow motion 0.25 (available in the settings menu in the bottom right corner). The flame “dissolves” in the ambient air and the residues of fuel, even if stretched out strongly by turbulence, are burned “hot”, without cooling down. In the last heating season the constructor increased the gas flow and completely got rid of the flame in the afterburner, which can be seen in the user’s videos on YouTube (I’ve put it on the FLOX page). This movie nicely illustrates the situation of a flame that “does not freeze”.