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University of Minnesota Extension

Selecting fans and determining airflow for grain bins

Here, we cover:

  • How to pick the best fans for crop drying, cooling or storage facilities, including an online fan selection tool.
  • Crop-specific airflow recommendations and expected static pressure.
  • How to determine airflow delivered by existing fans.

By using fans, you can force air with the proper temperature and relative humidity through a crop to help preserve quality after harvest. That's because the air helps maintain the moisture, temperature and oxygen content of a crop at levels that prevent harmful bacteria and fungi growth and excessive shrinkage.

We primarily discuss grains and oilseeds, but also mention hay, potatoes and other types of produce

Airflow requirements


Airflow resistance: Crops

When air is forced through a bulk crop, it must travel through narrow paths between individual particles. For packaged crops, air must travel through or between individual containers.

Friction along air paths creates resistance to airflow. Fans must develop enough pressure to overcome this resistance and move air through the crop.


Airflow resistance: Bins and buildings


Fan performance


Airflow provided by existing fans

Knowing the airflow provided by a fan allows you to estimate the time it will take to dry or cool a crop. This in turn, helps you determine whether you need to take steps to prevent unacceptable quality loss before the completing the task.


How to select fans


Online fan selection tool

The fan selection procedure we just described is not too difficult, but there’s an easier way to select fans for grain bins.

You can use the University of Minnesota Fan Selection for Grain Bins (FANS) web-based program available from the Department of Bioproducts and Biosystems Engineering at the University of Minnesota.

The program is very user-friendly and guides you through the fan selection process by asking simple questions about your grain drying or storage bin. The program allows you to select fans from a list of more than 200 commercially available models and see if the selected models provide the desired airflow.

William F. Wilcke, emeritus Extension engineer and R. Vance Morey, emeritus agricultural engineer, College of Food, Agricultural and Natural Resource Sciences

Reviewed in 2018

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