Evaporative CO2 heat transfer measurements for cooling systems of particle physics detectors

A major challenge in particle physics detectors is to transport the heat developed in their electronics to the outside world. Particle detectors require a minimum of material in order not to disturb accurate measurements of particle trajectories. CO2 has superior behavior in small diameter - low material - tubes, although detailed experimental data are lacking. Understanding the behavior of evaporative CO2 cooling in small diameter tubing is therefore of large interest for future detector cooling developments. At the Dutch Institute for Subatomic Physics, Nikhef, we are developing an automated CO2 test set-up able to scan the full phase space of mass fluxes, heat fluxes, vapor quality and temperature. A wide range of tube diameters (0.5 to 4mm) will be explored and data will be compared to the available models. In this paper we will present the test setup and the first measurements of heat transfer, pressure drop, and dry-out behavior at room temperature. Lower evaporation temperatures down to -50°C will be explored in a later stage after an upgrade of the research plant