Analysis of Temperature Oscillations in Parallel Evaporators of a Carbon Dioxide Two-Phase Loop

The tracker thermal control system (TTCS) is an active-pumped two-phase carbon dioxide cooling loop, which is developed for the Alpha Magnetic Spectrometer (AMS) tracker front-end electronics. The evaporators in parallel, gathering waste heat from, and providing stable and uniform thermal boundary condition to the electronics, are the key components of the loop. Any abnormities to the parallel evaporators is unacceptable. In this paper, we observed self-sustained temperature oscillations at the outlet of the evaporators when the cooling loop is operated at low temperature with the pump rotation speed lower than 3,300 rpm. Analysis shows that the oscillation could be of density-wave origin, and the flow rate redistribution between the two parallel evaporators may result in the self-sustained temperature oscillations.