Of combustible gas combustion furnace heat energy commonly used gas to provide, but the combustible gas in the combustion process of harmful gas will destroy the furnace heat treatment required environment, thus invented the radiant tube make the combustible gas in the combustion of the radiation tube, the heat radiation to the furnace by the radiation tube, won't destroy the environment in the furnace such harmful gas. However, the heating efficiency of the radiant tube is related to the efficiency of heat treatment because it radiates the workpiece through the wall. Therefore, the heating efficiency of the radiant tube is one of the main characteristics of the radiant tube. The earliest radiation tube was invented and used by Germany in the 1930s. Its structure is a single-layer straight tube, which passes through the furnace horizontally or vertically. It wasn't until the early 1950s that the u-shaped radiation tube came out; In order to improve the heating efficiency of radiation tube, W radiation tube was invented on the basis of U radiation tube. With the development of technology, p-type radiation tube, the typical type of radiation tube, appeared. In order to further improve the heating efficiency of the radiation tube, on the basis of various types of radiation tube, the machined radiation tube was invented. This process basically follows two lines of technological evolution:

1) evolution route of geometric shape -- the shapes of subsystems and subsystems and supersystems should coordinate with each other. One of the evolution routes is the evolution of geometric shape: straight line →2D line →3D line → complex line. According to this evolutionary route, the evolutionary process of improving the heating efficiency of radiant tubes is described: the system is in the stage of 2D curve of evolution, and the radiant tubes can be designed as 3D curves to improve the heating efficiency of radiant tubes, for example, the radiant tubes can be designed as bellows.

2) evolution path of surface shape: smooth surface → surface with convex surface → rough surface → surface with active substances. This evolutionary path describes the process of improving the heating efficiency of the radiant tube: the system is in the stage of evolution with a convex surface, and the number of convex surface of the radiant tube can be increased or the surface of the radiant tube can be designed as a rough surface to improve the heating efficiency of the radiant tube.