Characterization and mitigation of cooling fan installation penalties in 1U enterprise class servers

Almost all enterprise class 1U servers utilize active air cooling to maintain component temperatures. Despite a trend toward more efficient server components, the use of active cooling is still prevalent. Since the fans are a significant contributor to the power draw as well as the heat load, it is important to be able to optimize in situ fan performance. Typically, an enterprise class 1U enclosure will be cooled by a number of fans arranged in parallel. In such installations, the use of fan curves from flow bench tests and 1-D flow impedance models are typically not sufficient to accurately predict the fan power draw, local flow distribution or even the net air flow through the enclosure. This is primarily due to installation-driven fan performance degradation. In this paper, installation effects in a typical 1U enclosure are experimentally investigated and quantified. In addition, mitigation strategies for reducing the impact of installation effects within the original fan tray space claim are presented. Employing these strategies, an optimized fan installation that measurably reduces server power requirements is demonstrated.