Air Coolant Circuits in the Columbus Pressurized Modules

The pressurized modules use water and air coolant circuits to remove the dissipated heat from the sources and to transport it to the heat sink. The advantage of the water loops is to provide a high heat removal capability at low power consumption well suited for high specific heat loads i.e. assemblies with high dissipation and small volume. Air coolant circuits offer a higher flexibility to account for different shapes of the equipments and for changes in the configuration of the loop. Thus they are better suited for assemblies with lower dissipation and do not impose as much design restrictions on assemblies as water loops. But they have a higher specific power demand compared to water loops. In the Columbus pressurized modules avionics air loops and cabin air loops are installed. Both of them belong to the Environmental and Life Support Subsystem (ECLSS). Though they use the same fluid and to a wide extent also the same or at least very similar components the two air loops are different. The subject of this paper is to describe the latest status of the air loop designs and their control concepts. Differences on component level are identified and explained on the background of the differences in the loop concept. Test results gained from the development tests performed in this early phase are presented to demonstrate the suitability of the concepts for the tasks the air loops have to fulfil. They also provide an insight into the critical areas and possibilities to overcome these problems.