Characteristics of air-cooled package air conditioners with refrigeration pump for data centers

Yuji Kohata, Yosuke Udagawa, Keisuke Sekiguchi, Masahide Yanagi, Kiyoshi Saito, Keisuke Ohno, Yasuhiro Naito, Tsuneo Uekusa

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

    1 Citation (Scopus)


    In recent years, the amount of energy consumed by data centers has tended to increase. Therefore, power savings are strongly suggested. Data centers must be cooled year-round due to the extremely large amount of heat emitted from the IT devices. Therefore, to decrease year-round energy consumption, it is important to use low-temperature outdoor air during cool seasons such as mid-to-late fall and early spring and cold seasons like winter. Thus, we investigated cooling systems that use low-temperature outdoor air, and we developed a package air conditioner (A/C) that has cooling functions that use outdoor air. The new A/C combines a compression cycle and a cycle that stops the compressor and circulates coolant with a pump; it operates by switching to a compression cycle when the outdoor temperature is high and switching to a pump cycle when the outdoor temperature is low. Specifically, the pump cycle is the system of taking the low-temperature outdoor air into a coolant cycle from the heat exchanger in the outdoor unit (indirect outdoor-air cooling method) and transporting cold energy into the room with a pump. The A/C reduces the energy consumption in low outdoor temperatures by operating in favor of the efficient pump cycle. In this report, in order to verify the characteristics of the A/C, we built a simulation mathematical model. In addition, we verified the validity of the mathematical model compared to the measured value of the prototype. We show the effects of refrigerant circulation and outdoor-air temperature as an example of the verification simulation using a mathematical model. We calculated the annual energy consumption of the package A/Cs with refrigeration pumps based on the outdoor-air temperature data and the operating efficiency of the outdoor-air temperature. Specifically, the A/C that we developed reduced energy consumption by 50% in New York and 53% in Chicago, compared to the energy consumption of conventional computer-room A/Cs.

    Original languageEnglish
    Title of host publicationASHRAE Transactions
    PublisherAmer. Soc. Heating, Ref. Air-Conditoning Eng. Inc.
    Number of pages10
    ISBN (Print)9781936504961
    Publication statusPublished - 2015
    Event2015 ASHRAE Winter Conference - Chicago, United States
    Duration: 2015 Jan 242015 Jan 28


    Other2015 ASHRAE Winter Conference
    CountryUnited States

    ASJC Scopus subject areas

    • Mechanical Engineering
    • Building and Construction

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  • Cite this

    Kohata, Y., Udagawa, Y., Sekiguchi, K., Yanagi, M., Saito, K., Ohno, K., Naito, Y., & Uekusa, T. (2015). Characteristics of air-cooled package air conditioners with refrigeration pump for data centers. In ASHRAE Transactions (Vol. 121, pp. 430-439). Amer. Soc. Heating, Ref. Air-Conditoning Eng. Inc..