In order to improve the thermal efficiency of the radiation tube, the most direct way is to increase the length of the radiation tube, improve the flue gas flow time in the radiation tube, so that the flue gas and the radiation tube can fully exchange heat. However, if the radiation tube is too long, it will cause strength, stiffness, manufacturing and installation problems, which will affect the service life of the radiation tube. Later, the structure of burner was continuously improved to make the gas and combustion air fully mix and then fully burn, thus improving the thermal efficiency of the radiation tube.

After 1970s, regenerative combustion technology appeared, and regenerative burner was invented to recover waste heat of flue gas, which greatly reduced the waste of energy. In the early 1990s, regenerative combustion technology was widely used, the reliability of directional valve and control system was also improved, and the thermal efficiency was greatly improved to 70% ~ 90%. Working principle of regenerative combustion technology: combustion air enters burner A through four-way reversing valve through combustion air passage. After heating, the regenerator of burner A mixes with gas and burns in the radiation tube. The high-temperature flue gas generated by combustion flows through the radiation tube and enters burner B. After A set time through the four-way reversing valve and directional valve to change gas combustion air and gas flow, combustion air through A four-way reversing valve by the combustion air path to the burner, B after B in the burner of regenerator heating mixed with gas after burning, burning of the flue gas passes through A burner by flue discharge, at the same time of after A burner heating A burner in the regenerator. Cold air and high temperature smoke thus alternately flow through the heat storage body of A and B burner, and exchange heat through the heat storage body.

The regenerative combustion technology can reduce the flue gas temperature to below 200 ℃, which greatly improves the thermal efficiency of the radiant tube. This process of improving thermal efficiency Outlines the technological development path for the evolution of radiation tubes into supersystems:

The evolutionary route to supersystem -- when a system reaches its limit, it evolves towards a subsystem that becomes a supersystem. Through this evolution, the original system is upgraded to a higher level. One of the evolutionary routes is: single system → double system → multiple system. Follow this route to describe the evolutionary process of improving the heating efficiency of the radiant tube: the system is in the final stages of evolution.