Application of separated heat pipe system in data center cooling.

Investigation on thermal design of a rack with the pulsating heat pipe for cooling CPUs

The data-center cooling strategies have evolved from their original roots based on room air conditioning systems to the current status as a low-grade thermal energy resource. This paper presents an overview of different technologies driving the evolution of data-center cooling systems. Current status, future research trends and opportunities for developing energy-efficient systems utilizing single-phase and two-phase systems are highlighted. These changes are warranted more than ever, as the majority of large-scale data centers continue to be cooled by the conventional air cooling technology.

Current Status and Future Trends in Data-Center Cooling Technologies

Energy consumption analysis of a medium-size primary data center in an academic campus

Heat transfer and airflow characteristics enhancement of compact plate-pin fins heat sinks – a review

Energy consumption in data centers has seen a drastic increase in recent years and approximately 40% of it is spent on cooling facilities. In data centers, server racks are cooled down indirectly by chilled air with an air conditioner. This technique is inefficient because IT equipment is not cool enough whereas the server room is overcooled. Under these circumstances, the authors have proposed liquid cooling systems in which CPUs are cooled down directly and exhaust heat is not radiated into the server room. Three cooling technique for CPUs are developed simultaneously. Two of them involve a single-phase heat exchanger and a two-phase heat exchanger as a cooling jacket. The other is flat heat pipes in order that the heat generated by CPU is cooled after being transported to the outside of the chassis. Condensation section of the heat pipe is cooled down by liquid with liquid manifold, so that there is no air cooling part in our new liquid cooling systems. Performance evaluation tests of the cooling devices have been conducted, which are single-phase heat exchanger, two-phase heat exchanger and two-types of flat heat pipes. Meanwhile, nanofluid technology for heat transfer enhancement and development of plug-in connectors for standardization of the systems are pursued. In addition, Verification tests have been carried out with using commercial servers. As a result, a 44% to 53% reduction in energy consumption of cooling facilities with single-phase cooling system was realized compared with conventional air cooling system.

Thermal management systems for data centers with liquid cooling technique of CPU

The almost half amount of power consumption in data centers which has been increasing drastically in late years is due to air conditioner for cooling down the data centers. The present authors proposed new thermal management systems for data centers aiming for the data centers without air conditioning, and R&D subjects have been conducted under the so called Green IT Project sponsored by NEDO (New Energy and Industrial Technology Development Organization). In this system, three liquid cooling methods for CPUs have been developed simultaneously, which are two types of direct liquid cooling with single-phase or two-phase heat exchanger and an indirect liquid cooling with high performance thin heat pipes. To establish this system, five R&D subjects have been conducted. In this paper, current progress of these subjects such as development of heat transfer components, verification test using real server racks, and nanofluids technology for heat transfer enhancement is reported.Copyright © 2011 by ASME

New Thermal Management Systems for Data Centers

Energy consumption in data center has been drastically increasing in recent years. In data center, server racks are cooled down by air conditioning for the whole room in a roundabout way. This air cooling method is inefficient in cooling and it causes hotspot problem that IT equipments are not cooled down enough, but the room is overcooled. On the other hand, countermeasure against the heat of the IT equipments is also one of the big issues. We therefore proposed new liquid cooling systems which IT equipments themselves are cooled down and exhaust heat is not radiated into the server room. For our liquid cooling systems, three kinds of cooling methods have been developed simultaneously. Two of them are direct cooling methods that the cooling jacket is directly attached to heat source, or CPU in this case. Single-phase heat exchanger or two-phase heat exchanger is used as cooling jackets. The other is indirect cooling methods that the heat generated from CPU is transported to the outside of the chassis through flat heat pipes, and condensation sections of the heat pipes are cooled down by liquid. Verification tests have been conducted by use of real server racks equipped with these cooling techniques while pushing ahead with five R&D subjects which constitute our liquid cooling system, which single-phase heat exchanger, two-phase heat exchanger, high performance flat heat pipes, nanofluids technology, and plug-in connector. As a result, the energy saving effect of 50∼60% comparing with conventional air cooling system was provided in direct cooling technique with single-phase heat exchanger.Copyright © 2011 by ASME

Mayumi Ouchi

Papers

Thermal management systems for data centers with liquid cooling technique of CPU

New Thermal Management Systems for Data Centers

Liquid cooling network systems for energy conservation in data centers

New thermal management systems for data centers