A. Pauw

Active CO2 two-phase loops for the AMS-02 tracker

The Alpha Magnetic Spectrometer AMS-02 [1]-[4] is an astro particle physics experiment running on the International Space Station (ISS; see Figure 1) since May 19, 2011. Its missions include the search for antimatter and the identification of the nature of dark matter. The AMS silicon tracker is the only subdetector inside the AMS permanent magnet that can detect the charge of a moving particle to distinguish an anti-particle from particle (see Table 1 for nomenclature).

Investigation of Carbon Dioxide Explosive Boiling in Single Evaporator of a Two-Phase Mechanically-Pumped Thermal Control Loop

We investigated experimentally the start-up characteristics of a mechanically pumped two-phase loop (MPTCL), with CO2 as working fluid, and a single evaporator that consists of a bent inner ring and an outer ring constructed by stainless tubes with hydraulic diameter of 2.6 mm and length of 9 m, along which totally 54 pieces of heating element are distributed. Experiments were performed in the following conditions: mass flow rates of 1.1, 2.1, and 3.3g/s; heat loads ranged from 50 to 300W, with the heat-load ratios of the inner ring to the outer ring 2.2:1, 1:1, and 1:2.2 at the operational temperature of −15°C, respectively. During the start-up cases, we detected a reverse flow accompanying with pressure spike, which can be understood as explosive boiling, and a subsequent temporal dry-out phenomenon at the outlet of the evaporator, as a result of explosive boiling. The back flow together with the pressure spike is helpful to set up a two-phase flow all along the evaporator, though it may have negative effect on the loop, especially, when coincident explosive boiling happens. However, such a pressure spike that depends on initial superheating should be controlled to avoid possible harm to the loop.© 2010 ASME