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The Columbus laboratory module for the International Space Station (ISS) uses active thermal control for cooling of avionics and payload in the pressurized compartment. The Active Thermal Control Subsystem (ATCS) is based on a water loop rejecting waste heat to the Medium Temperature Heat Exchanger and Low Temperature Heat Exchanger on Node 2, part of the US Segment of the ISS. Flow and temperature control in the ATCS is achieved by means of the Water Pump Assembly (WPA) and the 3-Way Modulating Valve (WTMO) units. For the flow control the WPA speed is commanded so that a fixed pressure drop is maintained over the plenum with the avionics and payload branches. Adjusting the WTMO internal flow split permit the two active units to perform the CHX and plenum inlet temperature control. The WPA includes a filter and an accumulator to control the pressure in the ATCS and to compensate for leakage and temperature-dependent volume variations.

The stringent mass targets of the Hermes spaceplane require the design of extremely compact plate & fin heat exchangers, hence with a very low fin height, operating at low Reynolds numbers. These parameters, low Re (10-500 range) and low fin height (0.8 mm), have so far been little investigated and never applied to heat exchanger hardware development in Europe. Moreover, almost no relevant test data is available in the public domain, and what exists has been obtained from tests with gases rather than liquids. A programme, involving the design, manufacture and performance testing of a HX representative of the Hermes Interloop Heat Exchanger requirements, has been set up in order to explore manufacturing difficulties associated with such low height fins and to verify by test the fin thermo-hydraulic performance.

A new type of high efficiency and low-noise fan for space applications has been tested. It basically consists of two counter-rotating axial impellers, each driven by a brushless DC motor controlled by variable speed electronics. The underlying concept is the tip speed reduction (compared with a conventional fan type) achievable uniquely with counter-rotating impellers and which translates into reduced noise. Additional new features include electronic circuits for motor torque ripple control and motor phase commutation without rotor position sensors. Preliminary tests showed high efficiency and fairly low noise.