Integrated system of mechanical refrigeration and thermosyphon for free cooling of data centers

The number of data centers is increasing rapidly in recent years. Huge amount of energy is consumed by the cooling equipment of data centers for its year round working. Cutting down the energy consumption of cooling equipment becomes an urgent need and free cooling is an ideal way. It is proposed an integrated system of mechanical refrigeration and thermosyphon (ISMT) by combining two independent loops, mechanical refrigeration loop and thermosyphon loop, with a three-fluid heat exchanger. The new ISMT has three modes: mechanical refrigeration, thermosyphon free cooling and dual mode. The experimental results show that it has sufficient cooling capacity of all these three working modes. The EER of the thermosyphon mode reaches 10.7 and 20.8 when the indoor and outdoor temperature difference is 10 °C and 20 °C, respectively, and the AEER of the ISMT is 12.6, which is much higher than traditional air conditioners (TAC). The annual energy consumption in four cities located in different climate zones of China is calculated and compared to TAC in a small data center. The annual energy-saving rate is 5.4%–47.3% when the indoor temperature is set on 27 °C, and it is higher in colder zones for longer working time of thermosyphon free cooling.