I. Core premise: Clarify the operating condition boundary (basis for model selection)
Before model selection, it is essential to pinpoint three key operating condition parameters to avoid adaptation deviations:
1. Higher operating temperature: It is necessary to specify the peak temperature of the actual operating conditions (such as 350℃, 400℃). The rated temperature tolerance of the fan should have a safety margin of more than 50℃ higher than the peak temperature (for example, selecting a fan with a rated temperature of above 400℃ for a 350℃ operating condition);
2. Circulating system resistance: The total resistance includes that of the heater (heating tube arrangement, fin density) and the air duct (elbows, valves, pipe length), with a 10-20% margin reserved for air pressure;
3. Medium characteristics: Whether it is clean air; whether it contains dust, corrosive gases (such as sulfur and chlorine); whether it is flammable and explosive (such as chemical process gas); these directly determine the material and explosion-proof grade.
II. Selection of fan type: Priority given to "high-temperature dedicated centrifugal fan"
1. Type selection logic
| Fan type | Applicable scenarios | Not applicable scenarios | Core strengths |
| High-temperature centrifugal fan | Closed cycle, long duct, high resistance, requiring uniform heat exchange | Large space direct blowing, low resistance scenario | High wind pressure (compatible with heater resistance), stable airflow, and mature temperature resistance design |
| High-temperature axial flow fan | Large space, rapid circulation, low resistance scenario | Long air duct, high resistance, scenarios requiring precise temperature control | Large air volume, small size, and low energy consumption |
| Centrifugal fan without volute | Compact space, low noise requirements | High resistance and high wind pressure demand | Simple structure, good heat dissipation, and convenient maintenance |
2. Key conclusions:
• Most air circulation heaters (such as industrial ovens, pipeline heating, and reaction vessel tracing) need to overcome the resistance of heating tubes/air ducts, and it is preferable to choose "high-temperature dedicated centrifugal fans";
• For large spaces (such as large drying rooms) and low-resistance air ducts, a "high-temperature axial flow fan" can be selected, but it is necessary to ensure that the wind pressure can push the airflow over the heating elements (to avoid local overheating);
• It is recommended to use a variable frequency drive (VFD) motor: At high temperatures, air density decreases, and air volume will decrease as temperature rises. The VFD can dynamically adjust the speed, stabilize heat transfer efficiency, and save more than 30% energy.
III. Material selection for core components: temperature resistance + creep resistance are key
Under high temperature conditions, ordinary carbon steel and rubber will deform and age, necessitating the targeted selection of materials:
- Impeller material (core load-bearing component)
| Operating temperature | Recommended materials | alternative materials | Banned materials |
| 300-400℃ | 304 stainless steel (temperature resistance up to 450℃, corrosion resistance) | 316 stainless steel (temperature resistance up to 500℃, acid and alkali resistance) | Cast aluminum, ordinary Q235 carbon steel (with severe hot deformation) |
| 400-550℃ | 316L stainless steel (creep-resistant) | Inconel alloy (temperature resistance up to 600℃+, high strength) | 304 stainless steel (lacking strength at high temperatures) |
| corrosive medium | Hastelloy alloy (acid and alkali resistant, high temperature resistant) | Titanium alloy (extreme corrosion scenarios) | Ordinary stainless steel (susceptible to pitting corrosion) |
• Requirement: The impeller needs to undergo high-precision dynamic balancing (above G2.5 level). The thermal expansion and contraction of materials at high temperatures can amplify the imbalance, resulting in excessive vibration and noise.
2. Material of housing and spindle
• Casing: 304/316 stainless steel (for clean air), high-temperature modified carbon steel (Q235B + high-temperature paint, only for clean scenarios at 300-350℃), requiring the design of an "expansion compensation structure" (such as flexible connections, expansion joints) to avoid deformation and seizure at high temperatures;
• Main shaft: made of chromium-molybdenum steel (35CrMo) and stainless steel (1Cr18Ni9Ti), ensuring creep resistance at high temperatures (to prevent shaft diameter deformation after prolonged operation).
3. Sealing and lubrication: Eliminate the risk of failure
• Sealing method: Do not use ordinary rubber sealing rings (which will deteriorate and fail above 300℃). Preferably choose:
￮ Labyrinth seal (contact-free, maintenance-free, suitable for clean air);
￮ Graphite packing seal (for dusty/mildly corrosive environments, requiring regular replenishment of graphite packing);
￮ Metal bellows mechanical seal (high sealing requirements, such as flammable and explosive media).
• Lubrication method:
￮ Temperature ≤ 400℃: Select "high-temperature synthetic lubricant" (such as polytetrafluoroethylene-based, molybdenum disulfide-based, with temperature resistance of 350-400℃), and the bearing housing needs to be equipped with cooling fins;
￮ Temperature > 400℃: "Oil-free lubrication" (graphite bearings, ceramic bearings) to avoid carbonization and failure of lubricating oil;
Bearing installation: The "extended shaft design" is adopted to position the bearing housing away from the high-temperature airflow area (at a distance of ≥300mm from the air outlet), reducing heat conduction.
IV. Performance parameter matching: air volume + air pressure + temperature correction
1. Air volume calculation (core: ensuring uniform heat transfer and avoiding local overheating)
The air volume of the air circulation heater needs to meet the requirement of "rapid heat diffusion", with the formula reference as follows:
Q = P / (c·ρ·ΔT)
• Q: Required air volume (m³/h); P: Heater power (kW); c: Specific heat capacity of air (approximately 1.01 kJ/kg·℃); ρ: Air density at operating temperature (kg/m³, approximately 0.61 kg/m³ at 300℃, approximately 0.52 kg/m³ at 400℃); ΔT: Allowable temperature rise (℃, for example, if the temperature of air in the circulation system rises from 300℃ to 350℃, ΔT=50℃).
• Example: For a 100kW heater operating at 300℃ with a temperature difference (ΔT) of 50℃, the heat flow rate (Q) is approximately 32.5m³/h (calculated as Q ≈ 100/(1.01×0.61×50)). For practical selection, a 10% margin should be added, resulting in an approximate flow rate of 36m³/h.
2. Wind pressure matching
• It is necessary to overcome the "heater resistance (heating tube/fin) + air duct resistance (elbows, valves, pipeline along the way)". It is recommended to use air duct resistance calculation software (such as Fluent) or the resistance curve provided by the manufacturer for verification;
• Due to the decrease in air density at high temperatures, the actual wind pressure of the fan will be lower than that under standard conditions (20℃). It is necessary to correct the wind pressure based on the "operating density": Poperating = Pstandard × (ρoperating / ρstandard) (ρstandard ≈ 1.2kg/m³);
• Reserve a 15-20% margin for air pressure to cope with resistance fluctuations under high temperatures (such as dust accumulation in heating tubes and deformation of air ducts).
3. Motor selection: high temperature rating + heat dissipation design
• Motor insulation level: At least choose "Class F (temperature resistance 155℃)", preferably "Class H (temperature resistance 180℃)", to avoid motor burnout caused by high ambient temperature;
• Cooling method:
￮ Temperature ≤ 350℃: Equipped with an independent cooling fan (forced air cooling) to prevent direct contact of the motor housing with high-temperature airflow;
￮ Temperature > 350℃: Use "flameproof motor + external cooling jacket", or choose "water-cooled motor" (for extreme high temperature scenarios);
• Protection level: IP54 and above (dustproof, splash-proof, suitable for ind
V. Safety protection and additional functions (mandatory configuration)
1. Temperature monitoring and protection:
￮ Bearing temperature sensor (PT100): real-time monitoring of bearing temperature, alarm or shutdown in case of overtemperature (e.g. >85℃);
￮ Air outlet temperature sensor: It is linked to the heater and fan to prevent material failure caused by overtemperature;
2. Overload and explosion-proof protection:
￮ Equipped with standard thermal relays and overload protectors to prevent fan stalling and sudden load changes that could cause motor burnout;
If the medium is flammable and explosive gas (such as in the chemical, oil, and gas industries), choose an "explosion-proof fan" (Ex d IIB T4/T5 grade, suitable for high-temperature scenarios), and the motor and electrical components must comply with the GB 3836 explosion-proof standard;
3. Noise reduction and shock absorption:
The high-temperature fan operates at a relatively high speed (typically 2900r/min), so a low-noise impeller (rearward-facing plate-type impeller) is selected, and a muffler is added;
Install shock absorbers (such as rubber shock absorbers or spring shock absorbers) on the base to reduce the transmission of vibration to the equipment body.
VI. Key points for installation and maintenance (to extend service life)
1. Installation specifications:
The distance between the fan and the heater should be ≥500mm to avoid the impeller directly blowing against the heating tube (to prevent local overheating);
￮ Air duct design: Reduce 90° bends, shorten the length of the duct, and avoid sudden diameter changes (to reduce local resistance);
￮ Connection method: Flexible connections (such as high-temperature canvas, stainless steel bellows) are used at the inlet and outlet of the fan to absorb thermal expansion and deformation.
2. Maintenance cycle:
￮ Lubricating oil: Replace every 3-6 months (shortened to 2-3 months under high-temperature conditions), with the replacement amount indicated according to the scale on the bearing housing;
￮ Impeller cleaning: Check once every 6-12 months, and clean the accumulated dust and corrosion layer (to avoid damaging the dynamic balance);
Seals: Check the wear condition of graphite packing and labyrinth seals every 12 months, and replenish or replace them in a timely manner;
￮ Vibration detection: Regularly use a vibration meter to detect the vibration speed of the fan (normal if ≤4.5mm/s). If the speed exceeds the standard, perform dynamic balancing again.
VII. Model Selection and Pitfalls Avoidance: 3 Key Misconceptions
1. Modifying a regular fan into a high-temperature fan: By merely replacing the impeller material while neglecting bearing lubrication and the high-temperature rating of the motor, the fan will fail within 1-3 months;
2. The air volume/pressure has not been corrected for high temperature: The selection is based on standard condition parameters, resulting in insufficient air volume under actual working conditions, leading to local overheating and burnout of the heater;
3. Incorrect sealing method: Using labyrinth seals in environments containing dust or corrosive media, or rubber seals at high temperatures, can lead to leakage and sealing failure.
VIII. Recommended Brands and Model Selection Process
1. Professional high-temperature fan brands (recommended by scenarios)
• Domestic: Shangfeng Gaoke (industrial high-temperature centrifugal fan), Yilida (variable frequency high-temperature fan), Jinyida (explosion-proof high-temperature fan);
• Abroad: Glenro, EBMPAPST (industrial high-temperature axial flow fan), Neuplan.
2. Model selection process (efficiently connecting with manufacturers)
1. Clarify operating conditions: higher temperature, medium type, heater power, air duct size → 2. Calculate air volume/air pressure (or provide parameters to the manufacturer) → 3. Determine fan type (centrifugal/axial flow) → 4. Match materials (impeller/casing/seal) → 5. Confirm motor grade (insulation/heat dissipation/explosion-proof) → 6. Request the manufacturer to provide a "high-temperature operating condition performance curve" → 7. Verify installation space and maintenance feasibility.
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Post time: Jan-07-2026
