Cooling Pads Sized to the Fans
- A cooling pad is the inlet of a tunnel house. Area follows fan capacity, not house length.
- A 150 mm pad is commonly sized at about 1.8 m/s through the face. A 100 mm pad takes a lower speed.
- Too little pad raises pressure. The fans then move less air, and the tunnel slows.
Weifang Splendid sets the pad from the fans already on the house, or from the fans in the same quote. The pad wets the air that the tunnel fans pull. A pad without enough area, or a pad that is not fully wet, is an inlet problem. It is not fixed by adding one more fan on the same opening.
Area from the fans
Pad area is fan capacity divided by the speed you allow through the face. For a 150 mm pad the usual design speed is about 350 ft/min, roughly 1.8 m/s. That is about one square foot of pad for every 350 cfm the fans move at the working pressure. A 100 mm pad is sized slower, around 225 ft/min, because the air has less depth to pick up water. Weifang Splendid uses the fan curve at the pressure the house will actually run, not the free-air number on a brochure.
House length does not set the pad. A long house with few fans needs less pad than a short house with a full tunnel bank. Adding fans without adding pad is the common miss. The extra fan raises speed through the same face, pressure goes up, and each fan moves less than the sheet said.
Thickness and a wet face
100 mm and 150 mm are the two thicknesses in normal quotes. The thicker pad gives the air more wetted surface and more resistance. Hot, dry air can use the 150 mm. A milder site, or a house that already runs high pressure, often stays on 100 mm. The choice is confirmed on the fan list and the climate, not by picking the thicker one by default.
Water has to cover the whole face. A dry stripe is a hole. Uncooled air comes through it, and the birds near that bay feel it. The header, the holes, and the pump are part of the pad. A sump that runs dry, or a filter that clogs, shows up as a pale band on the cellulose, not as a fan fault.
| 100 mm | 150 mm | |
|---|---|---|
| Face speed | About 225 ft/min | About 350 ft/min, 1.8 m/s |
| Area rule | More pad for the same fans | About 1 ft² per 350 cfm |
| Use | Milder air, or a house already tight on pressure | Hot, dry air, full tunnel |
What else the inlet needs
The opening behind the pad has to pass what the fans pull. A pad on a small hole, or a winter door left half shut, adds pressure the pad did not create. Dog doors and leaks on the side walls steal air that should have come through the wet face. The pad only cools the air that actually crosses it. Weifang Splendid marks pad length from height and from the fan total, then checks the opening and the doors in the same pass.
What to send
Fan count and size, or the airflow you want down the house, house width and height, and whether the site is hot and dry or hot and humid. Thickness and metres of pad come from that.
FAQ
How is cooling pad area set?
From fan capacity, not house length. About 1.8 m/s through a 150 mm face.
100 mm or 150 mm?
150 mm for hot dry air and a full tunnel. 100 mm when the house is already tight on pressure, or the air is milder.
Why did adding fans not speed the house up?
The pad face was not increased. Pressure rose and each fan moved less.
What should I send?
Fans, house width and height, and whether the site is dry or humid.