Effect of warm water cooling for an isolated hybrid liquid cooled server

Data center cooling strategies have changed overtime due to increases in power densities and server cooling power requirement. Traditionally, most data centers adopt air cooling where the computer room air conditioner (CRAC) units pump volumes of chilled air to cool information technology (IT) equipment and dispose the heat to the ambient. With demand for energy-efficient and cost-effective data centers growing, alternative methods to both provide electrical power and cooling systems are the subject of active investigation. As data centers increase in size and current air-cooling systems reach their limitations, cooling technology will inevitably evolve towards air-liquid (hybrid) or liquid cooling systems. For this work, novel server level cooling is achieved through a combination of warm water and recirculated air (hybrid cooling) in a 2OU (OpenU) web server. Several experiments were conducted to characterize the thermal performance and energy consumption. This study highlights the impact of various inlet supply water temperatures within the ASHRAE TC 9.9 liquid cooling classes (W4), ranging from 27.5°C to 45°C, in terms of server power, component temperatures and cooling power consumption.