Experimental Demonstration and Flow Network Model Verification of Induced CRAH Bypass for Cooling Optimization of Enclosed-Aisle Data Centers

Hamza Salih Erden*, Mustafa Koz, Mehmet T. Yildirim, H. Ezzat Khalifa

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)


Aisle containment separates hot and cold aisles in air-cooled data centers to prevent hot air recirculation into cold aisle and decrease temperature nonuniformity among the servers. Uniform server inlet temperatures allow the cooling system to operate more efficiently at a higher evaporator temperature. Lower cooling power consumption can be achieved by optimizing the combined power consumption of the chillers and the computer room air handlers (CRAHs) fans. CRAH bypass (BP) is proposed, in which additional fans at the tiles induce a fraction of tile flow from the room into the plenum through low-resistance ports or leakage paths, thus decreasing the airflow passing through the high pressure resistance of the CRAH heat exchangers and filters and associated fan power usage. A further advantage of the proposed induced CRAH BP is the elimination of leakage as a result of reversing the room-plenum pressure difference. However, in order to keep the enclosed-aisle temperature below acceptable limits (typically ≤27 °C), the chiller needs to operate at a lower, less efficient temperature. This paper presents the experimental verification of a flow network model (FNM) in a data center test cell demonstrating the proposed induced CRAH BP concept. Exercise of the verified FNM in conjunction with a thermodynamic model of the cooling infrastructure (TDM) confirms that there is an optimum BP fraction that minimizes the combined chiller and CRAH fan power consumption.

Original languageEnglish
Article number8017446
Pages (from-to)1795-1803
Number of pages9
JournalIEEE Transactions on Components, Packaging and Manufacturing Technology
Issue number11
Publication statusPublished - Nov 2017

Bibliographical note

Publisher Copyright:
© 2011-2012 IEEE.


Manuscript received March 5, 2017; revised June 18, 2017; accepted July 13, 2017. Date of publication August 29, 2017; date of current version October 26, 2017. This work was supported in part by the New York State Energy Research and Development Authority under Award 41202. Recommended for publication by Associate Editor Y. Joshi upon evaluation of reviewers’ comments. (Corresponding author: Hamza Salih Erden.) H. S. Erden is with the Applied Informatics Department, Istanbul Technical University, Istanbul 34469, Turkey (e-mail: [email protected]).

FundersFunder number
New York State Energy Research and Development Authority41202


    • computer room air handlers (CRAH) bypass (BP)
    • Containment
    • data center
    • experiment
    • flow network modeling (FNM)
    • optimization


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