The project investigated the performance and integration of an advanced air‑conditioning unit (ARU) for aircraft cabin use, focusing on cooling capacity, weight efficiency, and noise reduction. In the first laboratory campaign, the ARU achieved a cooling power of more than 2.1 kW at an ambient temperature of 32 °C. When the ambient temperature was raised to 42 °C, the compressor power had to be reduced to avoid overloading, yet a cooling capacity of over 1.8 kW was still attainable. The results confirmed that the design calculations matched the measured performance, validating the underlying thermal model.

To improve weight efficiency, the team replaced the original heat exchangers with lighter, micro‑channel variants. This change reduced the overall system mass by 7.8 kg. A new drainage concept for the water separator was also introduced to eliminate residual water that could foster bacterial growth during idle periods. The upgraded system was then subjected to a second test campaign. During these tests, the dual‑compressor operation showed a reduced fluid flow compared to the sum of the individual compressor flows. Efficiency values at three operating speeds were 83 %, 69 %, and 63 % respectively, indicating a noticeable drop in performance when both compressors ran simultaneously. Thermographic imaging revealed that the evaporator was only partially cooled at full load, with roughly half the surface temperature falling below the expected value, suggesting insufficient refrigerant flow. Airflow measurements across the heat exchanger confirmed that the distribution was adequate but not optimal.

The water separator performed well up to 9 000 rpm but failed at the maximum 11 000 rpm due to increased suction pressure caused by the new heat exchanger geometry. Extending the water outlet downward was identified as a corrective measure. Cooling tests under normal ambient conditions (20–25 °C) yielded a maximum calculated cooling power of 1.14 kW, less than half of the original design target. Even at elevated temperatures, the new configuration only reached 1.75 kW, and this level could not be sustained. The project concluded that the cooling capacity could not be achieved with the current design, and further investigation into refrigerant routing was planned.

Parallel to the thermal studies, sub‑project 3.3.2 addressed active noise suppression. The German Aerospace Center (DLR) developed active counter‑phase techniques that excite the ARU structure to cancel low‑frequency noise. The analysis also highlighted the need for passive acoustic treatments, such as additional damping materials, to tackle higher‑frequency emissions. The combined approach was deemed promising for future implementation.

Sub‑project 3.2.5 focused on optimizing space below the lavatory sink by integrating a water heater and mixer into a single unit. Collaboration with Diehl Aviation Hamburg (DAH) produced CAD models demonstrating significant reductions in pipe length and overall volume. The new arrangement allows the heater, mixer, and controller to share a common housing, freeing up space for other cabin systems. The design was evaluated for compatibility with various lavatory configurations, and functional aspects such as drainage and venting were verified by the partner DAG.

The project was carried out by Diehl Aviation Gilching GmbH, with technical contributions from DLR, Diehl Aviation Hamburg, and DAG. While a specific funding source is not mentioned, the work aligns with industry initiatives to improve aircraft cabin comfort and efficiency. The collaboration enabled rapid identification of design weaknesses, iterative testing, and the development of both active and passive solutions to meet stringent performance and noise criteria.