Severe energy and environmental crises hinder sustainable development and realization of carbon peaking and carbon neutrality; therefore

more energy-efficient cooling systems must be developed for data centers. In this study

an indirect–direct evaporative cooling chiller coupled with a heat-pipe backplane air-conditioning system was designed

with four operating modes throughout the year. In Nanjing

the water supply and return temperatures of the chiller were designed to be 10 °C and 16 ℃

respectively. A mathematical model of each component was established; it was found that free cooling was used 59.9% of the year

and completely free cooling was used 42.6% of the year. When the supply and return temperatures increased

the free-cooling time increased. In addition

we explored the factors influencing heat-pipe backplane performance. The temperatures of the supply and return water had a great impact – the cooling capacity decreased as the temperature increased. The height difference between the CDU and the backplane had little effect once the power requirements of the refrigerant cycle were met. The diameter of the copper tube in the heat exchanger was reduced from 7 mm to 5 mm

and the cooling capacity and air-supply volume were improved.