Afroditi Koutoulaki, PhD at Nikhef, will defend her theses 16 September 2021 at 16.30 at Twente University.
“CO2 evaporative cooling for the ATLAS detector”
The first goal of this thesis was to show that CO2 evaporative cooling can enable the ATLAS detector to meet the stringent thermal and flow requirements in the upcoming upgrade. An experimentally validated thermal model is built to optimize the petal design, and to reliably demonstrate that the design would perform safely at the high luminosity LHC upgrade. The optimized parameters are the fractional radiation length of the petal, minimizing hot spots such as electrical chips, and maximizing the thermal safety margins, such as the distance from the thermal runaway.
To go beyond the current standard practice in thermal engineering, a second goal of this thesis was to extend the validity of prediction models for CO2 evaporation to the micro-channel level as those are useful for high-power density detectors that will be used in the ATLAS experiment in the future. Prediction models exist for micro-channels but the validated database include only studies on temperatures >-10oC and evaporation in channels greater than 0.5mm diameter. Significant effort has taken place over the last years to fill in the gap in this field of research. The goal of the research presented here is to extend the range of application of micro-channel evaporation modeling to below 0.30mm diameter and to temperatures down to -10oC, which is a typical diameter for cooling channels and temperature of interest for the particle physics community.
CO2 evaporative cooling has proven to be a promising method for cooling detectors in HEP. In this thesis, it was demonstrated that the evaporative cooling successfully keeps the petal detector in the ATLAS experiment cold and safe from thermal runaway for the 10 years of operation. CO2 evaporative cooling in micro-channels is also promising for high power-density detectors. In this thesis, it is demonstrated that the prediction models correctly predict the flow regime and pressure drop so far. Poor prediction was seen for the estimation of the heat transfer coefficient using the prediction models. And finally, because it was not possible to validate the prediction models with the measurements in the multiple micro-channels, only qualitative conclusions could be drawn.
“CO2 evaporative cooling for the ATLAS detector” (pdf)
The defense will be broadcasted online (link)
More information on the website of the UT.
Supervisor: prof. dr. ir. H.J.M. ter Brake
Co-supervisors: prof. dr. B. van Eijk en dr. N.P. Hessey
contact: Afroditi Koutoulaki