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Computational Fluid Dynamics Modeling and Validating Experiments of Airflow in a Data Center
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.ORCID iD: 0000-0002-7355-5950
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.ORCID iD: 0000-0001-8235-9639
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.ORCID iD: 0000-0002-1033-0244
2018 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, no 3, article id 644Article in journal (Refereed) Published
Abstract [en]

The worldwide demand on data storage continues to increase and both the number and the size of data centers are expanding rapidly. Energy efficiency is an important factor to consider in data centers since the total energy consumption is huge. The servers must be cooled and the performance of the cooling system depends on the flow field of the air. Computational Fluid Dynamics (CFD) can provide detailed information about the airflow in both existing data centers and proposed data center configurations before they are built. However, the simulations must be carried out with quality and trust. The k–ɛ model is the most common choice to model the turbulent airflow in data centers. The aim of this study is to examine the performance of more advanced turbulence models, not previously investigated for CFD modeling of data centers. The considered turbulence models are the k–ɛ model, the Reynolds Stress Model (RSM) and Detached Eddy Simulations (DES). The commercial code ANSYS CFX 16.0 is used to perform the simulations and experimental values are used for validation. It is clarified that the flow field for the different turbulence models deviate at locations that are not in the close proximity of the main components in the data center. The k–ɛ model fails to predict low velocity regions. RSM and DES produce very similar results and, based on the solution times, it is recommended to use RSM to model the turbulent airflow data centers.

Place, publisher, year, edition, pages
MDPI AG , 2018. Vol. 11, no 3, article id 644
Keywords [en]
data center; airflow; computational fluid dynamics (CFD); turbulence models
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
URN: urn:nbn:se:ltu:diva-67958DOI: 10.3390/en11030644ISI: 000428304300172OAI: oai:DiVA.org:ltu-67958DiVA, id: diva2:1191242
Note

Validerad;2018;Nivå 2;2018-03-19 (andbra)

Available from: 2018-03-16 Created: 2018-03-16 Last updated: 2018-11-07Bibliographically approved
In thesis
1. A Numerical and Experimental Study of Airflow in Data Centers
Open this publication in new window or tab >>A Numerical and Experimental Study of Airflow in Data Centers
2018 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Airflow management is crucial for the performance of cooling systems in data centers. The amount of energy consumed by data centers is huge and a large amount is related to the cooling. In attempts to develop energy efficient data centers, numerical methods are important for several reasons. Experimental procedures are more expensive and time consuming but when done carefully, experiments provide trustful results that can be used to validate simulations and give additional insights. Numerical methods in their turn have the advantage that they can be applied to proposed designs of data centers before they are built and not only to already existing data centers.

In this study, Computational Fluid Dynamics (CFD) is used to study the airflow in data centers. The aim is to use an experimentally validated CFD model to investigate the effects of using different designs in data centers with respect to the performance of the cooling systems. Important parameters such as quality of the computational grid, boundary conditions and choice of turbulence model must be carefully considered in order for the results from simulations to be reliable.

In Paper A, a hard floor configuration where the cold air is supplied directly into the data center is compared to a raised floor configuration where the cold air is supplied into an under-floor space instead and enters the data center through perforated tiles in the floor. In Paper B, the performance of different turbulence models are investigated and velocity measurements are used to validate the CFD model. In Paper C, the performance of different cooling systems is further investigated by using an experimentally validated CFD model. The effects of using partial aisle containment in the design of data centers are evaluated for both hard and raised floor configurations.

Results show that the flow fields in data centers are very complex with large velocity gradients. The k − ε model fails to predict low velocity regions. Reynolds Stress Model (RSM) and Detached Eddy Simulation (DES) produce very similar results and based on solution times, it is recommended to use RSM to model the turbulent airflow in data centers. Based on a combination of performance metrics where both intake temperatures for the server racks and airflow patterns are considered, the airflow management is significantly improved in raised floor configurations. Using side covers to partially enclose the aisles performs better than using top covers or open aisles.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2018
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-67781 (URN)978-91-7790-062-7 (ISBN)978-91-7790-063-4 (ISBN)
Presentation
2018-04-25, E632, Luleå tekniska universitet, Luleå, 10:00
Opponent
Supervisors
Available from: 2018-03-01 Created: 2018-02-27 Last updated: 2018-11-07Bibliographically approved

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Ljung, Anna-LenaLundström, Staffan

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