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繁體中文Under Canopy Tube Ventilation in Greenhouses
11/04/2026Under-canopy tube ventilation delivers air through perforated tubes positioned beneath the crop. The fan supplies the tube, and the openings distribute air into the growing area. The tube therefore forms part of the air distribution system rather than acting as a simple extension of the fan outlet.
ebm-papst describes this greenhouse arrangement alongside horizontal circulation. The two approaches serve different air paths and can form part of a combined climate concept. The correct choice depends on how the greenhouse prepares and distributes air around the crop.
Establish where the supplied air comes from
A tube system may receive air from a preparation area or another defined source in the greenhouse design. The fan moves that air; separate equipment provides any specified heating, cooling, moisture treatment or enrichment.
Before selecting the fan, describe the intended air condition and supply route. Fan capacity cannot establish whether the air itself is appropriate for the crop. That decision belongs to the greenhouse climate design and operating strategy.
Select the fan and tube as a system
Tube length, diameter and opening pattern influence resistance and distribution. The fan must supply the required flow against that resistance. A free air rating is therefore not sufficient for choosing a tube ventilation fan.
Changing the tube or its perforations can change the operating point and the airflow delivered along its length. A replacement fan should be checked against the installed tube specification, especially if the original distribution arrangement has been modified.
Check delivery along the full crop row
Strong airflow near the fan does not demonstrate adequate delivery at the far end. Assess representative positions along the tube and across the served growing area. Tube damage, blocked holes, poor connections or unintended leakage can create uneven delivery.
Installation also needs to account for routine greenhouse operations. Tubes should remain in their intended position and avoid damage during cultivation and cleaning. Where flexible tubes are used, their operating shape is part of the distribution behavior and should be checked under the intended conditions.
Choose the pressure capability and control range
The ebm-papst greenhouse application describes pressure-capable centrifugal or axial fan solutions for tube ventilation. This does not mean that every axial fan will suit a long perforated tube. The actual fan curve and permitted operating range must match the required duty.
Variable speed can adjust delivery when the complete system is designed for it. At reduced speed, verify that the tube still distributes air acceptably. The lowest electrical speed setting is not automatically the lowest useful ventilation setting.
Prepare a tube ventilation enquiry
For APAC FAN support, supply tube length and diameter, perforation information, required airflow and pressure, and details of the air preparation arrangement. Existing fan labels and photographs are useful for replacement projects. Include your email or WhatsApp number so the proposed fan can be reviewed against the actual distribution system.
