Efficient temperature control of highly viscous gear oil
JULABO Case Study - Bühler Motor GmbH
09/18/2026
Precise temperature simulation is crucial for Bühler Motor in Nuremberg, a long-standing JULABO customer, in product development and quality control to ensure the performance and reliability of its products under realistic operating conditions.
This is essential for developing innovative solutions that meet the demanding requirements of various industries.
Bühler Motor's Temperature Control Requirements
The product development team at Bühler Motor aims to test different pump types simultaneously using a suitable gear oil. The engineers need to precisely control the temperature of the gear oil in an open bath over a wide temperature range from -40 to +140 °C. The bath is equipped with inlet and outlet connections that allow the customer to connect several pumps directly and validate their performance under simulated real-world operating conditions.
To avoid unnecessary delays during testing, the customer requires a cooling rate of 4 K/min for the bath, which holds approximately 35 liters of gear oil. In addition, a relatively high heat input of up to 7 kW is expected at an application temperature of -40 °C.
Another challenge lies in the gear oil itself: at the required low temperatures, it becomes extremely viscous – with a consistency similar to thick honey. This makes it impossible to use a conventional process system directly, as its pumps are not designed to handle such high viscosities. Furthermore, the high viscosity of the oil would make it physically impossible to achieve sufficient heat transfer within the required time.
JULABO's Solution Approach
Working closely with the engineers at Bühler Motor GmbH, JULABO designs a customized solution. This solution includes a powerful PRESTO W91 process system, in a combination with a custom-built FlexiRack from the Business Unit Solutions, which develops and manufactures custom solutions tailored to customer needs.
Energy transfer is achieved using a large plate heat exchanger. To ensure the required cooling capacity at an application temperature of -40°C, the process system must maintain the temperature control medium (silicon oil) at approximately -50°C at all times. The PRESTO W91 offers sufficient power reserves to ensure this is possible without any issues, even in the event of unexpected, additional energy losses.
The FlexiRack was custom-built for the project with Bühler Motor and has a unique design. The connections from the application side to the plate heat exchanger are very large, with a cross-section of 50 mm, so that the highly viscous oil can circulate at the necessary speed for energy transfer. In addition, the open bath containing the gear oil is positioned slightly higher during operation, allowing gravity to further support circulation.
The FlexiRack also features a standalone Siemens-based PLC control system, specifically integrated for the customer. This system comprehensively controls the FlexiRack and the PRESTO through continuous monitoring of relevant parameters via various sensors (pump pressures, temperatures, etc.) and ensures maximum process reliability. This allows Bühler Motor’s engineers to take corrective action at any time should undesirable situations arise during the application.
For additional process safety, the bath is installed on-site in an enclosure with a nitrogen or dry air atmosphere. This minimizes humidity and prevents the risk of condensation and resulting ice formation that could damage the plate heat exchanger.
Conclusion
Thanks to the innovative solution combining a process system and FlexiRack, Bühler Motor GmbH can effectively test the performance of its pumps under real-world conditions – despite the exceptional requirements of the process.
The success of this project demonstrates how close collaboration, a goal-oriented approach, and transparent communication can lead to optimal results.
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