Surface load is the core parameter in selecting tubular electric heaters, directly affecting service life and operational safety. Industry experience data shows: for clean water heating, 6–8 W/cm² is recommended; for heat transfer oil, 2–4 W/cm²; for still air, 1–3 W/cm²; for oil tank applications, it is recommended to keep it below 0.7 W/cm². A higher surface load will cause excessive tube wall temperature, leading to carbonization, oxidation, or even tube burnout. During design and selection, the heating medium should be confirmed first, then the material and surface load limit should be determined based on the medium type to avoid early failure caused by parameter mismatch.
The heating medium determines the material and surface treatment of the heating tube. For clean water applications, 304 stainless steel or copper is usually selected; for heat transfer oil media, 304 or 321 stainless steel is suitable; for corrosive liquids, 316L stainless steel or titanium is required; for highly corrosive or high-temperature air environments, the material needs further upgrading. Improper material selection will accelerate tube corrosion and shorten the replacement cycle. For special scenarios such as mold heating, the fit clearance between the tube body and the mold hole and the thermal conductivity efficiency should also be considered.
Heating power must be calculated based on medium mass, specific heat capacity, and heating time, with a safety factor of approximately 1.2 introduced. For example, to heat a certain mass of heat transfer oil from initial temperature to the set temperature, the required power can be estimated using the formula P = (m×c×ΔT)/(t×η). During installation, the heating zone must be fully immersed in the medium to avoid dry burning. Voltage specifications can be 220V, 380V, or customized; before wiring, the power distribution capacity, number of phases, and wiring method must be verified. Structural forms include ordinary tubular, flanged, single-head rod, sheathed, and explosion-proof types. The sheathed type is easy to maintain, and explosion-proof applications require products with explosion-proof certification.
Cold insulation resistance is usually required to be no less than 1MΩ, and higher values are recommended for important equipment. Withstand voltage, grounding, and over-temperature/dry-burn protection should be configured according to working conditions. Tubular electric heaters are small in size and high in power; when using intelligent control mode, temperature control accuracy is high, and networked monitoring is possible. Common applications include oil tank and oil box heating (SRY series, flanged type, and sheathed type are more common), shoe-making machinery, chemical machinery, pharmaceutical machinery, electric ovens, centrifuges, battery factories, storage battery factories, garment factory steam furnaces, automated electronic equipment, wave soldering, reflow soldering machinery, washing and drying machinery, and air and medium heating in refrigeration equipment. U-shaped heating tubes are also widely used in similar scenarios, and targeted material selection and structural design should be combined with the specific use environment during design.
