Advanced computational fluid dynamic simulations of boiling CO2 for tracker cooling of the compact muon solenoid at CERN

Project: Research-related funding


CERN is the world’s largest high energy particle physics laboratory, which is based in Geneva Switzerland. In order to probe the fundamental behaviour of the universe, CERN’s engineers are required to achieve some of the world most extreme technical requirements and to produce vast accelerator systems such as the Large Hadron Collider (LHC). One of the main experiments within the LHC complex is the Compact Muon Solenoid (CMS) – a 14,000 tonne detector capable of resolving the one billion proton-proton interactions which are produced each second in its core.

The University of Bath and CMS have recently signed an affiliation agreement in order to make use of Bath’s state-of-the-art facilities and internationally renowned research team to tackle some of the extreme technical challenges at CERN. In this regard, Bath is initiating a PhD project focused on the £76 million CMS tracker upgrade, which is due to be installed in 2024.

The proximity of the detector to the collisions means that it receives the highest intensity radiation, and therefore effective cooling is required. The cooling channels need to be small (1-2 mm diameter) and lightweight (0.1-0.15 mm wall thickness) to minimise radiation shadowing, as well as highly reliable to minimise the need of maintenance. Two-phase CO2 cooling will be used in the next generation of the tracker, which will be operated at 163 bar and -35°C. These conditions have been selected in order to maximise the CO2 heat absorption by exploiting the latent heat of the liquid-to-gas phase change. As a result, an improved understanding of the behaviour of the two-phase CO2 is required; in particular the impact of pressure losses and temperature changes due to shear flow in the cooling pipes need to be investigated. In this project, Computational Fluid Dynamics (CFD) will be employed to reveal new fundamental insights into this behaviour and thereby define new guidelines for future design. These new insights will then be used to generate new design tools for the cooling systems at CMS and CERN.
Short titleFull PhD studenship
Effective start/end date4/11/19 → …