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Research Papers

New Thermal Management Systems for Data Centers

[+] Author and Article Information
Mayumi Ouchi

 National Institute of Advanced Industrial Science and Technology, Central 2, Umezono 1-1-1, Tsukuba, Ibaraki 305-8568, Japanmayumi.ouchi@aist.go.jp

Yoshiyuki Abe

 National Institute of Advanced Industrial Science and Technology, Central 2, Umezono 1-1-1, Tsukuba, Ibaraki 305-8568, Japany.abe@aist.go.jp

Masato Fukagaya

 SOHKi Co., Ltd., Ote-machi, Minato-ku, Nagoya, Aichi 455-0046, Japanfukagaya@sohki.jp

Takashi Kitagawa

 Kawamura Electric, Inc., 3-86 Akatsuki-cho, Seto, Aichi 489-0071, Japanta-kitagawa@kawamura.co.jp

Haruhiko Ohta

Department of Aeronautics and Astronautics,  Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japanohta@aero.kyushu-u.ac.jp

Yasuhisa Shinmoto

Department of Aeronautics and Astronautics,  Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japanshinmoto@aero.kyushu-u.ac.jp

Masahide Sato

Department of Advanced Interdisciplinary Science,  Utsunomiya University, 7-1-2 Yoto, Utsunomiya, Tochigi 321-8585, Japanmasa@chem,utsunomiya-u.ac.jp

Ken-ichi Iimura

Department of Advanced Interdisciplinary Science,  Utsunomiya University, 7-1-2 Yoto, Utsunomiya, Tochigi 321-8585, Japanemlak@cc.utsunomiya-u.ac.jp

J. Thermal Sci. Eng. Appl 4(3), 031005 (Jul 16, 2012) (10 pages) doi:10.1115/1.4006478 History: Received June 12, 2011; Accepted March 14, 2012; Published July 16, 2012; Online July 16, 2012

Energy consumption in data centers has seen a drastic increase in recent years. In data centers, server racks are cooled down in an indirect way by air-conditioning systems installed to cool the entire server room. This air cooling method is inefficient as information technology (IT) equipment is insufficiently cooled down, whereas the room is overcooled. The development of countermeasures for heat generated by IT equipment is one of the urgent tasks to be accomplished. We, therefore, proposed new liquid cooling systems in which IT equipment is cooled down directly and exhaust heat is not radiated into the server room. Three cooling methods have been developed simultaneously. Two of them involve direct cooling; a cooling jacket is directly attached to the heat source (or CPU in this case) and a single-phase heat exchanger or a two-phase heat exchanger is used as the cooling jacket. The other method involves indirect cooling; heat generated by CPU is transported to the outside of the chassis through flat heat pipes and the condensation sections of the heat pipes are cooled down by coolant with liquid manifold. Verification tests have been conducted by using commercial server racks to which these cooling methods are applied while investigating five R&D components that constitute our liquid cooling systems: the single-phase heat exchanger, the two-phase heat exchanger, high performance flat heat pipes, nanofluid technology, and the plug-in connector. As a result, a 44–53% reduction in energy consumption of cooling facilities with the single-phase cooling system and a 42–50% reduction with the flat heat pipe cooling system were realized compared with conventional air cooling system.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Comparison of cooling systems: Conventional air cooling by CRACs and new liquid cooling system

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Figure 2

Experimental apparatus to determine thermal performance of the single-phase heat exchanger

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Figure 3

Heater temperature, Tcore , as a function of heat input for the single-phase heat exchanger when coolant temperature is 15 °C

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Figure 4

Thermal resistance, R, as a function of heat input for the single-phase heat exchanger when coolant temperature is 15 °C

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Figure 5

Heater temperature, Tcore , as a function of heat input for the single-phase heat exchanger when flow rate is 0.5 l/min

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Figure 6

Thermal resistance, R, as a function of heat input for the single-phase heat exchanger when flow rate is 0.5 l/min

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Figure 7

Schematic diagram of the two-phase heat exchanger

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Figure 8

Heating surface temperature of the two-phase heat exchanger using FC-72 as coolant

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Figure 9

Thermal resistance as a function of heat input for the two-phase heat exchanger when pressure is 0.15 MPa and inlet coolant temperature is 35 °C

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Figure 10

Pressure drop of the two-phase heat exchanger

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Figure 11

Appearances of two types of flat heat pipes. (a) Thin heat pipe made by flattening out tube-type copper heat pipe. Its size is 1.5 mm thick, 15 mm wide, and 200 mm long. (b) Plate-type heat pipe made by diffusion bonding of two copper plates. Its size is 2 mm thick, 30 mm wide, and 200 mm long.

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Figure 12

Comparison of thermal performances of thin heat pipes (1.5 mm × 15 mm × 200 mm) using three working fluids

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Figure 13

Thermal performance of plate-type heat pipe (2 mm × 30 mm × 200 mm)

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Figure 14

SEM images of Ag nanofluids

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Figure 15

Surface tension behavior of four PVP capped Ag nanofluids containing 5 wt. % 1-butanol aqueous solution

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Figure 16

Prototype plug-in connector for the heat spreader and the single-phase heat exchanger (a) before insertion, (b) after insertion

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Figure 17

Prototype server racks for verification tests of the single-phase cooling system and the thin heat pipe cooling systems. (a)–(c) Mount single-phase cooling system and (d) mounts flat heat pipe cooling systems.

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Figure 18

Cooling unit for CPUs in server with the single-phase heat exchanger

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Figure 19

Cooling unit for CPUs in server with thin heat pipes and the heat exchanger

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Figure 20

Cooling unit for CPUs in server with plate-type heat pipes and the heat exchanger

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