Necessary conditions for fan selection

2025-08-08

Fan selection requires a comprehensive judgment based on usage scenarios, medium characteristics, performance requirements, etc., with the key being matching core parameters such as 'airflow' and 'pressure,' while also considering operational condition compatibility.

Here are specific steps and key points:

I. Clarify Core Requirements: First, focus on the two major parameters of 'airflow' and 'pressure'

This is the foundation of selection, which needs to be calculated or determined based on actual scenarios:

- Airflow (Q): The volume of gas that needs to be transported per unit time (e.g., m3/h, m3/min).

Example: Workshop ventilation requires calculation based on workshop volume and air change rate (Airflow = Workshop Volume × Air Change Rate); boiler draft requires determination based on the amount of air needed for fuel combustion.

- Pressure (P): The resistance that needs to be overcome when conveying gas (e.g., Pa, kPa).

Including pipeline resistance (local resistance from bends, valves, etc. + along-the-length resistance of the pipe) and equipment resistance (such as filters, heat exchangers, etc.), which need to be estimated through resistance calculation formulas or empirical data.

II. Combine Medium Characteristics: Exclude incompatible types

The nature of the gas medium directly affects the type of fan selected, requiring special attention to:

Medium cleanliness:

- Clean air (such as office ventilation): Can choose centrifugal fans, axial fans, low cost.

- Containing dust/particles (such as mine dust removal, cement transportation): Select wear-resistant type fans (such as centrifugal fans with wear-resistant impellers), avoid axial fans (impellers prone to dust accumulation and jamming).

- Containing corrosive gases (such as chemical waste gas): Select corrosion-resistant types (such as fiberglass material fans, stainless steel components).

Medium temperature:

- Normal temperature (≤80℃): Ordinary fans can be used.

- High temperature (such as boiler flue gas, hot air conveyance, 80-400℃): Select high-temperature resistant fans (such as impellers made of high-temperature alloys, motors equipped with cooling systems).

Medium flammability and explosiveness:

- Such as methane, gas, etc.: Must select explosion-proof fans (explosion-proof treatment of motor, switch, etc., meeting explosion-proof standards).

III. Based on Scene Characteristics: Match Fan Types

Different fans have different 'airflow-pressure' characteristics, which need to be matched with the 'airflow-pressure requirements' of the scene:

- Axial fans: Suitable for 'high airflow, low pressure' scenarios (pressure usually ≤5kPa, airflow can reach tens of thousands of m3/h).

Example: Overall workshop ventilation, cooling tower ventilation, subway tunnel ventilation (need to quickly transport large amounts of air, small resistance).

Centrifugal fans:

- Single-stage centrifugal fan: Suitable for 'medium airflow, medium pressure' (pressure 5-15kPa), such as boiler supply fans, kitchen exhaust, small factory ventilation.

- Multi-stage centrifugal fan: Suitable for 'low airflow, high pressure' (pressure ≥10kPa, even exceeding 100kPa), such as long-distance pipeline conveyance, chemical high-pressure gas conveyance, mining underground high-pressure ventilation.

Other special types:

- Roots blower: High pressure (up to 200kPa and above), stable flow, suitable for 'constant flow' scenarios (such as sewage treatment aeration, pneumatic conveying), but noise is relatively high.

- Mixed-flow fan: Between axial and centrifugal, moderate airflow and pressure, suitable for medium-pressure ventilation with limited space (such as building vertical shaft ventilation).

Optimize selection details: balancing efficiency and practicality

- Efficiency first: choose the model with the highest efficiency at 'design conditions (airflow, air pressure)' (efficiency curves are marked in the fan samples), avoiding 'overkill' (selecting a larger model, actual operation deviates from design conditions, low efficiency, high energy consumption).

Installation and maintenance:

- Limited space: select compact models (such as axial flow fans, small centrifugal fans); if installation within ducts is required, duct-mounted centrifugal fans can be chosen.

- Maintenance convenience: prioritize models with easily removable parts (such as modular design for impellers, bearings), especially in complex medium scenarios (such as dusty, corrosive media, requiring frequent maintenance).

- Noise requirements: for noise-sensitive environments (such as residential areas, offices), prioritize low-noise fans (such as selecting low-speed models for axial flow fans, adding silencers to centrifugal fans).