Numerical investigation on integrated system of mechanical refrigeration and thermosyphon for free cooling of data centers

• A simulation model of an ISMT is built and validated by experimental data.
• The performance and effect of some design parameters are studied for the three modes.
• Two loops in refrigeration mode affect each other through fluid temperature of THE.
• Applicable outdoor temperature range for dual mode exists which is lower than 19 °C.
• Applicable indoor air flow rate range for dual mode exists which is higher than 0.5 m3 s−1.

The cooling energy consumption of data centers is increasing rapidly and free cooling attracts growing concern. To achieve the independent running of free cooling system all the year round, integrated system of mechanical refrigeration and thermosyphon (ISMT) is an ideal method. In this study, a distributed-parameter simulation model of an ISMT is built and validated by experimental data. The simulation results show that for thermosyphon mode, the cooling capacity increases with increasing air flow rate, temperature difference and pipe diameter, while decreases with increasing pipe length. For refrigeration mode, decreasing outdoor air temperature or increasing indoor air flow rate will improve the cooling capacity and reduce the input power of the compressor. For dual mode, applicable outdoor temperature range and indoor air flow rate range exist and the cooling capacity drops below that of refrigeration mode beyond these ranges. The critical values are 19 °C and 0.5 m3 s−1, respectively.