Data Center Economizer Cooling with Tower Water; Demonstration of a Dual Heat Exchanger Rack Cooling Device

A prototype computer equipment rack-level cooling device with two heat exchangers was demonstrated to illustrate an energy efficient cooling capability. This unique device was designed and constructed by APC by Schneider Electric to operate with higher-temperature cooling water, so that it can support many more hours of free cooling compared to traditional systems that utilize chilled water. The cooling system contained two separate air-to-water heat exchangers, rather than one usually found in similar devices that operate using chilled water. In this design, one heat exchanger was configured to use higher temperature water produced by a cooling tower alone. The other coil was configured and controlled to allow chilled water flow, should supplemental cooling be required. The device also contained three fans, which were used to pull warm air from the computer equipment exhaust area through the two heat exchangers and return the cooled air to the air intake area of the computer equipment. A model of the heat exchangers’ performance was developed and used with an industry standard energy-efficiency metric to explore the device’s capabilities and efficiency The device effectively cooled the warm air from the exhaust of the computer equipment and had favorable energy use efficiency and capability when compared to other similar equipment.

In this analysis, the concept of using two heat exchangers in the intended configuration is more energy efficient, compared to typical designs using a single heat exchanger. The high cooling performance of this device is able to meet cooling requirements while using higher-temperature water, thereby reducing energy needed for compressor-based cooling. Results suggest that the development of a production version be continued using the design concepts of this prototype.