Abstract
Forecasting data center cooling demand remains a primary thermal management challenge in an increasingly larger global energy-consuming industry. This paper proposes a dynamic modeling approach to evaluate two different strategies for delivering cold air into a data center room. The common cooling method provides air through perforated floor tiles by means of a centralized distribution system, hindering flow management at the aisle level. We propose an idealized system such that five overhead heat exchangers are located above the aisle and handle the entire server cooling demand. In one case, the overhead heat exchangers force the airflow downwards into the aisle (Overhead Downward Flow (ODF)); in the other case, the flow is forced to move upwards (Overhead Upward Flow (OUF)). A complete fluid dynamic, heat transfer, and thermodynamic analysis is proposed to model the system’s thermal performance under both steady state and transient conditions. Inside the servers and heat exchangers, the flow and heat transfer processes are modeled using a set of differential equations solved in MATLAB™ 2017a. This solution is coupled with ANSYS-Fluent™ 18, which computes the three-dimensional velocity, temperature, and turbulence on the Airside. The two approaches proposed (ODF and OUF) are evaluated and compared by estimating their cooling effectiveness and the local Entropy Generation. The latter allows identifying the zones within the room responsible for increasing the inefficiencies (irreversibilities) of the system. Both approaches demonstrated similar performance, with a small advantage shown by OUF. The results of this investigation demonstrated a promising approach of data center on-demand cooling scenarios.
Highlights
Data center thermal management is generally accomplished by providing cold air from a raised floor into the server aisle
The heat transfer within the servers and heat exchangers was modeled as described by Equations (6)–(18) via a finite difference scheme solved in MATLABTM
The results indicate that higher inefficiencies existed in diverging flows (ODF), which is attributed to a larger pressure drop
Summary
Data center thermal management is generally accomplished by providing cold air from a raised floor into the server aisle. The cooling is aided by the strategic placing of heat exchanger arrangements: overhead, in-row, rear-door. Limited academic work exists on each system, where most of the available information is provided by the equipment suppliers in catalogs and manuals. The majority of the authors center their efforts on cases where centralized CRAH units provide the cold air. The air is ducted and distributed to the data center room aisles [1,2,3,4]. This approach, Entropy 2019, 21, 98; doi:10.3390/e21010098 www.mdpi.com/journal/entropy
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