A scaled-down development sample of a new radiator fan, shown here as a 3D-printed model.

The Ideal (Air) Flow

A family-owned business develops a test bed for optimizing fans with the support of Steinbeis experts

Since 1999, Hägele, a medium-sized enterprise based in Schorndorf east of Stuttgart, has been developing, producing and selling radiator cooling fans for “off-highway machines” – i.e. commercial off-road vehicles used (among other things) in farming, construction, and the railroad industry. To test, adapt, and optimize its fans, the company developed a test bed with the support of FLOWTRANS, a Steinbeis Transfer Center.

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The cooling fans produced by Hägele offer a unique feature in the form of a sophisticated mechanical system that allows fan blades to be rotated mechanically, pneumatically, or hydraulically in such a way that adjustments can be made to the flow of air through the cooler unit. In addition, the airflow can be completely reversed to make it easier to clean the cooler. This provided inspiration for the brand name of its fans: CLEANFIX®.

Although the family business sees itself as a component supplier, it is increasingly supporting customers worldwide by offering system expertise in the development of complete energy-efficient, low-noise cooling modules. This made it necessary to use a test bed to determine precise airflow characteristics and the efficiency of its fans. Not only would this test bed need to measure fans in the current product range, which perform at up to 100 kilowatts, but it would also have to work with much smaller models, which are needed to provide inexpensive and quick help for new developments. It was also important that the test bed can be used to measure the air resistance of cooling assemblies provided by customers, because the data this produces would be required to work out the fan specification and to eventually dimension and select the optimal fan.

The birth of a test bed

This is where Steinbeis entrepreneur Professor Dr.-Ing. Thomas Carolus and his Steinbeis Transfer Center FLOWTRANS came on board, providing support in the design of the testing unit, dimensioning, the selection of measuring instruments, and commissioning and sign-offs. Working in close cooperation with Hägele, a suction-side chamber test bed was developed in compliance with international standards (such as ISO 5801 and ANSI/AMCA 210-16). The testing facility is suitable for use with axial-flow fans with impeller diameters of 300 to 900 millimeters.

Measuring 14 meters in length, the test bed comprises a nozzle bank for recording air volume flows, the air supply system (which in turn consists of a 30-kilowatt controllable auxiliary blower and a manually adjustable louvered throttle), and a large chamber to which the test object is flanged. The pressure chamber measures increasing pressure exerted on the fan and pressure losses in the chiller assembly expressed as static pressure. During testing, the fans are rotated using an adjustable drive unit with interchangeable torque measurement shafts. This makes it possible to determine fan efficiency.

Most of the sensors fitted on the test bed are easy to access from the control room, and this allows calibrations to be made with little effort before each series of measurements. Special software was developed with a user-friendly screen to allow accurate measurements to be taken. These are then plotted in real time and archived.

The new fan test bed developed with the Steinbeis experts from Netphen, Germany has put Hägele in a much better position to work together with customers in adapting CLEANFIX® fans to specific applications, not only ensuring that testing matches objectives, but also allowing new fans to be designed more efficiently in the future. Also in the future, the firm will also be able to offer third-party companies “fan measurement as a service.”


Prof. Dr.-Ing. Thomas Carolus (author)
Steinbeis Entrepreneur
Steinbeis Transfer Center FLOWTRANS (Netphen)

Daniel Arnold (author)
Hägele GmbH (Schorndorf)