Improving Cooling Efficiency Of Servers By Replacing Smaller Chassis Enclosed Fans With Larger Rack-mount Fans

Abstract

As a common practice in the data center industry, chassis fans are used to direct air flow independent from neighboring servers. However, these fans are less efficient compared to larger rack level counterparts and also operate at higher sound levels. In this study, a novel approach is proposed whereby the smaller chassis enclosed fans are replaced with an array of larger fans, installed behind the stacked servers that share air flow. As a baseline study for comparison of the current scenario, a CPU dominated 1.5U Open Compute server, with four 60mm fans installed within the server, is characterized experimentally for its flow impedance, air flow rate, effect on die temperature and power consumption for various compute utilization levels. Larger fans with a square frame size of 80mm are carefully selected and individually characterized for their air moving capacity and power consumption. CFD is used to simulate the system of stacked servers and larger fans to obtain its flow characteristics and operating points. The fan power consumption of the larger fans is determined experimentally at these operating points replicated in an air flow bench. Comparing with the base line experiments, this study predicts a significant decrease in fan power consumption, without conceding the flow rate and the static pressure requirements of the server.