The electric resistance of the electric heating wire is selected according to the set power. The larger the power, the smaller the total resistance.
The electrical resistivity of the heating wire has an appropriate range. If the electrical resistivity is too small or too small, a short or very long, very thin or very thick heating wire is required, so that it is difficult to manufacture and use the electric heater of the size and power. . An important parameter of the heating wire is the surface power. The resistivity is too large, and the surface power is large after a certain current is applied. Therefore, for small power appliances, small diameter and small current are used, but the magnitude of the current is determined by the size of the resistor. The length and diameter of the heating wire are calculated.
The use of electric heating in large industrial electric furnaces is to increase the surface area and ensure that the surface power does not exceed the standard. At the same time, in order to ensure high power, there must be a large enough current, so that the length and cross-sectional area and shape of each electric heating belt are comprehensively considered. Therefore, the electric heating wire (belt) used in the electric heater requires a lot of power factors when designing an electric heater.
The allowable surface power of such a material, the cross-sectional area of the heating wire (belt), the length of the heating wire, the shape of the heating wire (straight, spiral, broken line, winding, etc.).
Some special electric heaters, such as electric blankets, require a large heat dissipation area and a low unit power. If ordinary nickel-chromium and iron-chromium-aluminum electric heating wires are used, a hot wire with a small cross section is required, which cannot be made at all. . Therefore, the electric blanket is made of manganese copper wire, and the resistivity of the manganese copper wire is much smaller than that of the iron chromium aluminum, so that there is sufficient length.
Electric heater features
1. Small volume and high power: The heater mainly uses clustered tubular electric heating elements.
2. Fast thermal response, high temperature control accuracy and high comprehensive thermal efficiency.
3, high heating temperature: the maximum operating temperature of the heater design can reach 850 °C.
4. The medium outlet temperature is uniform and the temperature control precision is high.
5, wide application range, adaptability: The heater can be applied to explosion-proof or ordinary occasions, the explosion-proof grade can reach dIIB grade and C grade, the pressure can reach 20MPa.
6. Long life and high reliability: The heater is made of special electrothermal material, with low surface power load and multiple protections, which greatly increases the safety and life of the electric heater.
7. Fully automatic control: According to the requirements, the heater circuit design can easily realize the automatic control of the parameters such as outlet temperature, flow rate and pressure, and can be networked with the computer.
8. The energy saving effect is remarkable, and the heat generated by the electric energy is transmitted to the heating medium almost 100%.