Effect of the diameter of riser and downcomer on an CO2 thermosyphon loop used in data center

Abstract

As the two-phase thermosyphon loop (TPTL) system is well accepted for data center cooling, its structural design becomes an important problem to be solved. Among the different structural parameters of a TPTL, the diameter of riser and downcomer is the most critical one affecting the operating performance of the TPTL. In the present study, an experiment was conducted to analyze the effect of the diameter of riser and downcomer on an CO2-based TPTL. With the same evaporator and condenser, three diameters of 6 mm, 9 mm and 12 mm were tested. In addition, a steady-state calculation model was established to further investigate the effect of more different diameters. The model, which was verified by the experimental data, can provide more operating parameters inside the TPTL. The results showed that the diameter of riser and downcomer had a great effect on the working state and maximum heat transfer capacity of the CO2 TPTL. With the diameter changed from 6 mm to 12 mm, the maximum heat transfer capacity of the CO2 TPTL increased from 1500 W to 5400 W. However, the influence of the diameter on the required driving temperature difference was not that obvious.