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Audi uses the thermal wind tunnel mainly to study the engine cooling system and the heat management. Vehicles are tested under extreme conditions in the tunnel, where temperatures can reach 55 degrees and air speeds can be pushed up to 275 km/h.
In contrast to the aeroacoustic wind tunnel, the air flow in the thermal wind tunnel follows a vertical path. A powerful one megawatt fan operates in the upper storey above the test section, with a heat exchanger immediately behind it which heats the air continuously from +20 to +55 °C.
The test section
The test section is almost eight metres long; thanks to its heated, transparent floor, it offers maximum scope for observation and realistic testing of the vehicle. Unlike the aeroacoustic wind tunnel, the vehicle is supported on rollers. The twin-axle four-wheel roller dynamometer ensures that near-realistic simulation of various test cycles (uphill driving, trailer towing) can be simulated. The roller diameter is two metres and the brake output is 400 kW.
Eliminating hot spots
By using the thermal wind tunnel it is possible to make significant improvements to the thermal management in a vehicle. In order to produce a wide range of models with different engine combinations, it is essential to have sufficient cooling in all driving situations. No hot spots must be created in any part of the engine compartment. And it is also important to provide good cooling for auxiliary equipment.
While it is true that cooling systems are designed basically by computer, testing is still necessary to check that the original requirements are being fulfilled. The development of the engine, condenser, charge air, brakes and the various oil circuits all rely on the thermal wind tunnel.
Air flow through and around the vehicle are closely connected to each other, regardless of whether we are talking about a passenger car, off-road SUV or a sports car. The results obtained in the aeroacoustic wind tunnel have a bearing on tests performed in the two smaller wind tunnels – another benefit of bringing together the organisation of the three facilities on the Audi Wind Tunnel Centre site.