The main factor that determines the outer diameter of the resistance wire of the tubular heater?
The main factors that determine the outer diameter of the resistance wire in the tubular heater are as follows:
(1) Heat conduction The heat of the resistance wire is transmitted to the sleeve through the magnesium oxide powder, and then to the object to be heated. Generally, the resistance wire coil wound into a coil is regarded as a resistance wire with an outer diameter of d. When wrapped with a thermal conductivity insulator, the heat dissipation is best when its thickness is large.
(2) The insulation distance is different from the insulation resistance between the resistance wire and the bushing at high temperature and low temperature, but if the insulation distance is considered from the insulation resistance itself, the larger the distance, the greater the insulation resistance between the resistance wire and the bushing Big. From the perspective of heat conduction, there is a certain limit. The insulation distance varies with the required temperature of the insulation resistance. However, if high-quality magnesia powder is used as insulation, it can usually be appropriately selected from 1.5 to 3 mm.
(3) The unevenness of the resistance reduction rate is contacted with the magnesium oxide powder around the periphery, and the porosity of the magnesium oxide is reduced by the compression processing after the magnesium oxide powder is filled, and the resistance value of the resistance wire is reduced by 15-25% at this time. about. At this time, attention should be paid to the influence of the outer diameter of the coil in the resistance drop rate. Generally, the larger the outer diameter of the coil, the larger the rate of decrease in resistance, and the unevenness. This non-uniformity should be reduced, because this non-uniformity will directly deviate from the rated power.