Energy-saving potential analysis of a CO2 two-phase thermosyphon loop system used in data centers

Recently, the rapid development of data centers has led to an increased requirement of cooling systems, resulting in high energy consumption. A two-phase thermosyphon loop (TPTL) system effectively utilizes a natural cold source and reduces energy consumption in data centers. In this study, an experiment was conducted to compare the heat transfer performance of CO2 TPTL with the commonly used R134a and R410A TPTLs. Under their respective optimal filling ratios, CO2 TPTL exhibited the lowest required driving temperature difference, which was 3 degrees C lower than that of R410A TPTL and 5 degrees C lower than that of R134a TPTL. The energy-saving effect of CO2 TPTL was analyzed based on a typical data center case and the climate parameters of different cities in China. In Beijing, the annual average PUE (power usage effectiveness) of the data center using conventional centralized cooling systems, R134a TPTL, R410A TPTL, and CO2 TPTL was 1.43, 1.36, 1.34, and 1.32, respec-tively. The calculation for other cities showed that the energy saving ratios of the CO2 TPTL system in Kunming were the highest. They were 58.6%, 40.7%, and 30.4% higher compared with those of conventional centralized cooling system, R134a TPTL, and R410A TPTL, respectively.