Ventilation Fans: Matched to Operating Point & System Resistance

Axial Fans for In-Line Airflow & Compact Installation

Axial fans move air generally parallel to the fan shaft. Their straight-through geometry makes them attractive where installation length and duct alignment matter. YONGFAN’s axial range includes several different constructions rather than one universal axial fan:

DTF Series Axial-Flow Tube Exhaust Fan is the broad in-duct family. Published performance covers 1,886–114,829 m³/h and 115–2,266 Pa, with impeller diameters from Ø350 to Ø1600 mm. Relevant configurations include normal ventilation, smoke-exhaust and explosion-proof variants. Fire-rated DTF configurations are documented for 280 °C / 30 min smoke-exhaust duty.

DTXF Series Low-Noise Tube Axial Exhaust Fan is the lower-noise route when the basic in-line axial architecture is correct but acoustic performance is more demanding. Its published range is 2,472–114,829 m³/h and 132–2,166 Pa. The supplied material states that DTXF is approximately 6–12 dB(A) quieter than standard DTF at comparable duty, and it uses compatible flange geometry for replacement applications.

T35-11 / BT35-11 Bifurcated Axial Fan solves a different operating problem. The motor sits in a separate bypass section rather than directly in the handled airstream. The documented range is 552–58,343 m³/h and 32–420 Pa, with five factory-set blade angles from 15° to 35°. Standard T35-11 construction is documented for airstream temperatures up to approximately 80 °C. BT35-11 adds explosion-protected construction.

WEX / BWEX External-Rotor Wall Fan is the compact wall or terminal solution. Published nominal diameters run from Ø250 to Ø1000 mm. Its external-rotor motor gives the fan a very short axial depth, making it useful at wall openings, ceiling apertures and duct terminations. BWEX is the explosion-proof variant.

Mixed-Flow Fans When Axial Geometry Needs More Pressure

Mixed-flow fans are useful when the installation benefits from an in-line body but the pressure requirement is higher than a conventional low-pressure axial arrangement can comfortably provide.

The main YONGFAN family is SWF Series Mixed-Flow Tube Fan. SWF covers 1,430–144,260 m³/h and 125–1,314 Pa, with impeller diameters from Ø300 to Ø1500 mm. The supplied product data divides the family into I, II and III configurations for different pressure and speed duties.

The important buyer advantage is geometry. SWF keeps a compact tube-style installation while extending pressure capability into duties that may otherwise push the design toward a larger centrifugal arrangement.

The CDZ Series Mixed-Flow Duct Fan provides another in-line route, with 2,176–33,158 m³/h, 97–701 Pa and impeller diameters from Ø355 to Ø800 mm. Its motor is positioned outside the handled airstream, which makes it relevant where the air condition makes a motor-in-stream arrangement undesirable.

HL3-2A belongs in this mixed-flow group for ducted basement and car-park exhaust applications. It is paired in the supplied product documentation with PYHL-14A, a jet-induction fan used where the ventilation strategy reduces or removes large exhaust duct networks.

Centrifugal Fans for Higher-Resistance Duct Systems

A centrifugal fan turns the airflow through an impeller and casing, giving the designer more pressure capability for systems with significant resistance.

YONGFAN’s principal general-purpose family is the 4-72 Series Centrifugal Fan. Published performance covers 1,131–46,988 m³/h and 372–3,200 Pa, with documented impeller diameters from Ø280 to Ø800 mm in the listed range. The source data identifies approximately 75–87% efficiency near preferred operating points and supports direct drive on smaller units and belt drive on larger configurations. That makes 4-72 relevant to HVAC air handling, industrial process ventilation and other applications where the fan must overcome more system resistance than a low-pressure axial arrangement.

The SJG Series Cabinet-Type Centrifugal Ventilation Fan serves a different installation need. It covers 380–15,070 m³/h and 65–820 Pa static pressure. The forward-curved centrifugal wheel sits inside a cabinet while the motor remains outside the handled airstream. The discharge can be adjusted in 10° increments up to −90°, which helps route ducts through constrained plant rooms and service spaces.

SJG is therefore not simply a smaller 4-72. It is a cabinet-style solution for building exhaust, kitchens, laboratories, car parks and mildly challenging air conditions where serviceability and duct routing matter.

Roof Fans for Direct Roof-Level Exhaust

Roof fans remove air directly through the building envelope and eliminate the need to route every exhaust stream to a remote plant-room fan. The DWT Series Roof Ventilation Fan combines two roof-fan architectures:

DWT-I is the centrifugal version. DWT-II is the axial version.

The combined documented range is 1,560–50,000 m³/h with 11–407 Pa static pressure. The source lists centrifugal diameters from Ø300 to Ø900 mm, axial sizes No.3–10, IP54 motor protection and 220 V or 380 V / 50 Hz supply depending on size.

The choice between DWT-I and DWT-II follows the pressure requirement. The axial route favors high airflow at lower resistance; the centrifugal route is the stronger fit when the roof exhaust path needs more pressure capability. Weather cap, roof curb, discharge direction, maintenance access and water ingress control should be resolved at the same time as the airflow selection.

Tunnel & Jet Fans for Thrust-Based Ventilation

Tunnel ventilation should not be selected from a conventional duct-fan table alone. The SDS / SDS(R) Tunnel Jet Fan family is designed for longitudinal ventilation, where the fan transfers momentum to the tunnel air and generates thrust rather than serving a closed duct network.

The supplied SDS data covers approximately 7.9–71.8 m³/s airflow, 191–3,046 N static thrust, impeller diameters from approximately Ø630 to Ø1600 mm, and motor power from 4 to 90 kW.

SDS is the unidirectional version. SDS(R) uses a reversible blade arrangement for bidirectional ventilation and emergency smoke-control strategies. The source states that reversal from forward to reverse at rated speed occurs within 30 seconds. The reversible model produces approximately 4–6% lower thrust than the corresponding unidirectional version.

Optional 1D and 2D silencers are documented, with approximately 9–14 dB(A) sound reduction compared with the bare fan arrangement. Fan quantity is not selected only from nominal thrust. Tunnel length, cross section, traffic, vehicle emissions, CO/NOx limits, natural airflow, installation spacing and emergency fire strategy all affect the installed effective thrust.

PYHL-14A is also a jet-induction product, but its role should be distinguished from SDS. PYHL-14A is documented within underground car-park and similar ductless induction applications. SDS/SDS(R) is the dedicated tunnel longitudinal-ventilation family.

Explosion-Proof Fans for Classified Hazardous Areas

Explosion-proof selection begins with the site classification, not the fan airflow. YONGFAN’s ventilation portfolio includes explosion-protected versions of several architectures:

BT35-11 is the explosion-proof version of the T35-11 bifurcated axial fan. BWEX is the explosion-proof version of the compact WEX external-rotor wall fan.

DFBZ / BDFBZ is the dedicated explosion-proof bifurcated family documented for Zone 1/2 applications under GB 3836. Its performance range is 552–58,343 m³/h and 32–420 Pa, with factory-set blade angles from 15° to 35°. The product uses a non-sparking, non-magnetic, non-ferrous impeller and keeps the explosion-proof motor outside the main hazardous airstream.

Relevant DTF configurations also include ExdbIIBT4 / ExdbIICT4 options in the supplied documentation.

An explosion-proof fan should never be selected merely because “Ex” appears in the model name. The project must define the hazardous zone, gas or dust group, required temperature class, motor protection, electrical entry and local certification requirement.