Investigation of CRAH bypass for air-cooled data centers using computational fluid dynamics

Vahid Ebrahimpour, Hamza Salih Erden

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

5 Citations (Scopus)


Computer room air handling (CRAH) bypass (BP) method utilizes fan-equipped perforated tiles to force or induce room air through relatively lower flow resistance than that in CRAH units, as CRAH fans operate at lower speed. Increasing the BP airflow rate reduces the total fan power and increases the chiller power since the CRAH unit needs to provide colder air when a certain fraction of warm room air is allowed to mix with cold CRAH airflow. Simplified airflow network and thermodynamic modeling tools addressed this optimization problem and indicated cooling energy savings potential via CRAH BP method for enclosed aisle (EA) data centers. These tools assume uniform air temperature at the server inlets, even though recent experimental and computational studies indicate temperature non-uniformities at higher fractions of BP flow. This study addresses energy implications of the uniform temperature assumption of the reduced order modeling tools on the cooling energy saving potential of EA data centers by using computational fluid dynamics (CFD) modeling. Moreover, existing literature does not thoroughly investigate the application of CRAH BP in the open aisle (OA) data centers, which requires CFD models to resolve complex airflow patterns due to recirculation of hot air into the cold aisle and leakage of cold air into the hot aisle. This study utilizes CFD to investigate both induced and forced CRAH BP methods in a representative quadrant of a 1MW data center with and without aisle containment.

Original languageEnglish
Title of host publication2018 IEEE International Telecommunications Energy Conference, INTELEC 2018 - Proceedings
PublisherInstitute of Electrical and Electronics Engineers Inc.
ISBN (Electronic)9781538653708
Publication statusPublished - 2 Jul 2018
Event2018 IEEE International Telecommunications Energy Conference, INTELEC 2018 - Torino, Italy
Duration: 7 Oct 201811 Oct 2018

Publication series

NameINTELEC, International Telecommunications Energy Conference (Proceedings)
ISSN (Print)0275-0473


Conference2018 IEEE International Telecommunications Energy Conference, INTELEC 2018

Bibliographical note

Publisher Copyright:
© 2018 IEEE.


This research is supported by the Scientific and Technological Research Council of Turkey (TÜBİTAK) through Award Number 118M238.

FundersFunder number
Türkiye Bilimsel ve Teknolojik Araştirma Kurumu


    • Air-cooled data centers
    • Computational fluid dynamics
    • CRAH bypass method


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