Is it normal for the tubular heater turning red when it works?
The metal tubular heating element is protected by a metal tube shell; the inner spring-shaped alloy resistance wire is led out through the conductive metal lead rods connected at both ends, and the heat conduction and insulation medium magnesium oxide is filled between it and the shell protection tube. The density is equivalent to that of granite, the thermal conductivity is equivalent to that of steel, and the insulation performance is equivalent to that of natural mica.
When the lead rods at both ends are energized, due to the electrical effect of the resistance wire, the heat is conducted and radiated outwards by the resistance wire-magnesium oxide dielectric layer-shell protection tube-air and shell protection tube contacts. Mainly conduct heat, supplemented by radiant heat.
In the case of normal temperature and still air, when the heat generation of the tubular heater is relatively large and the conductive area is relatively small, when the surface power density of the heating area of the metal shell armored tube is >2.8W/cm2, the conversion from conduction to radiant heat is compared Obviously, that is, the redness phenomenon commonly known as the electric heating tube. At this time, the surface temperature of the shell armor tube is> 500 degrees, and the surface color is dark red, and with the increase of temperature, the color is dark red, orange red, orange yellow, and torch white changes. The tubular heater configured with the best material can run stably below orange red, which is the temperature resistance performance of the 800-850 degree shell protection tube.
The tubular heater is a power-type resistor, and heating effect is inevitable; when the surface power density of the heating area of the tubular heater shell protection tube is too large, redness is inevitable. When the design target heat has a positive effect, as long as the redness is helpful to the situation control requirements and meets the overall system thread transfer, it is an optimized design and redness is normal. When the design target heat is a negative effect, the load is generally adjusted by designing low surface load components or accompanied by water-cooling, air-cooling, and heat dissipation devices. If this happens, it is abnormal if the heat is still red. In addition, the surface load of the tubular heating element is uneven, and it is also abnormal to produce local overheating and redness.
Where, whether the redness of the tubular heater is normal depends on the entire target design process. Taking customer needs as the starting point and target definition as the criterion, on this basis, the function of the design component is established, the component detailed tasks are determined, the design concept is formed, the plan is generated, and then further analysis and optimization are performed to complete the experiment, achieve the goal, and then meet the market.