Experimental investigation and application analysis on an integrated system of free cooling and heat recovery for data centers.

• A new data center cooling system integrating heat recovery with free cooling is proposed. • The system can work selectively in four different modes according to conditions and demands. • Stable performance of each mode and dynamic performance in mode switching are obtained. • Annual power consumption and heat recovery analysis are conducted in five cities. Rapid growth of data centers has caused a huge increase in energy consumption. Utilizing natural cold resources and harvesting waste heat are two promising ways to reduce the total power consumption of data centers. This paper proposes an integrated system of free cooling and heat recovery. The system has four working modes: mechanical cooling, mechanical heat recovery, pump free cooling and pump heat recovery. Experimental results show that pump free cooling mode can achieve an energy efficiency ratio of 7.99 when outdoor temperature is 2 °C, and different modes can be switched smoothly. The applicability of this system has been evaluated in five different cities in China. The results show that annual average energy efficiency ratio can reach 6.18 and free cooling time can take up as high as 72.9% during operation in Xining. The system can harvest the most heat in Harbin, 7930.96 kW∙ h per year, while the least in Guangdong, 645.31 kW∙ h per year. This means that this new system has relatively great application prospects in northern cold cities of China, while is moderately limited in southern cities. [ABSTRACT FROM AUTHOR]