Improving the Data Center Servers Cooling Efficiency via Liquid Cooling-based Heat Pipes

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.

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Characterization of an Isolated Hybrid Cooled Server With Failure Scenarios Using Warm Water Cooling

ASME 2017 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems ◽

10.1115/ipack2017-74028 ◽

2017 ◽

Cited By ~ 1

Author(s):

Uschas Chowdhury ◽

Manasa Sahini ◽

Ashwin Siddarth ◽

Dereje Agonafer ◽

Steve Branton

Keyword(s):

Energy Consumption ◽

Data Centers ◽

Cooling System ◽

Warm Water ◽

Alternative Methods ◽

Inlet Temperature ◽

Cooling Efficiency ◽

Water Cooling ◽

Liquid Cooling ◽

Total Energy Consumption

Modern day data centers are operated at high power for increased power density, maintenance, and cooling which covers almost 2 percent (70 billion kilowatt-hours) of the total energy consumption in the US. IT components and cooling system occupy the major portion of this energy consumption. Although data centers are designed to perform efficiently, cooling the high-density components is still a challenge. So, alternative methods to improve the cooling efficiency has become the drive to reduce the cooling cost. As liquid cooling is more efficient for high specific heat capacity, density, and thermal conductivity, hybrid cooling can offer the advantage of liquid cooling of high heat generating components in the traditional air-cooled servers. In this experiment, a 1U server is equipped with cold plate to cool the CPUs while the rest of the components are cooled by fans. In this study, predictive fan and pump failure analysis are performed which also helps to explore the options for redundancy and to reduce the cooling cost by improving cooling efficiency. Redundancy requires the knowledge of planned and unplanned system failures. As the main heat generating components are cooled by liquid, warm water cooling can be employed to observe the effects of raised inlet conditions in a hybrid cooled server with failure scenarios. The ASHRAE guidance class W4 for liquid cooling is chosen for our experiment to operate in a range from 25°C – 45°C. The experiments are conducted separately for the pump and fan failure scenarios. Computational load of idle, 10%, 30%, 50%, 70% and 98% are applied while powering only one pump and the miniature dry cooler fans are controlled externally to maintain constant inlet temperature of the coolant. As the rest of components such as DIMMs & PCH are cooled by air, maximum utilization for memory is applied while reducing the number fans in each case for fan failure scenario. The components temperatures and power consumption are recorded in each case for performance analysis.

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Hybrid cooled data center using above ambient liquid cooling

2010 12th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems ◽

10.1109/itherm.2010.5501426 ◽

2010 ◽

Cited By ~ 7

Author(s):

Brandon A Rubenstein ◽

Roy Zeighami ◽

Robert Lankston ◽

Eric Peterson

Keyword(s):

Data Center ◽

Liquid Cooling

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New Thermal Management Systems for Data Centers

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4006478 ◽

2012 ◽

Vol 4 (3) ◽

Cited By ~ 6

Author(s):

Mayumi Ouchi ◽

Yoshiyuki Abe ◽

Masato Fukagaya ◽

Takashi Kitagawa ◽

Haruhiko Ohta ◽

...

Keyword(s):

Heat Exchanger ◽

Single Phase ◽

Data Centers ◽

Cooling System ◽

Heat Pipes ◽

Air Cooling ◽

Liquid Cooling ◽

Two Phase ◽

Cooling Jacket ◽

Cooling Methods

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.

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Introducing Energy Efficiency Metrics for Server and Data Centers

Volume 4: Energy Systems Analysis, Thermodynamics and Sustainability; Combustion Science and Engineering; Nanoengineering for Energy, Parts A and B ◽

10.1115/imece2011-64704 ◽

2011 ◽

Author(s):

Abdlmonem H. Beitelmal ◽

Drazen Fabris

Keyword(s):

Energy Efficiency ◽

Data Center ◽

Data Centers ◽

Cooling Efficiency ◽

Idle Power ◽

Relevant Variables ◽

The Cost ◽

Evaluation Of Data

New servers and data center metrics are introduced to facilitate proper evaluation of data centers power and cooling efficiency. These metrics will be used to help reduce the cost of operation and to provision data centers cooling resources. The most relevant variables for these metrics are identified and they are: the total facility power, the servers’ idle power, the average servers’ utilization, the cooling resources power and the total IT equipment power. These metrics can be used to characterize and classify servers and data centers performance and energy efficiency regardless of their size and location.

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Research on Intelligent Air Conditioning System of Data Center

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.602-605.928 ◽

2014 ◽

Vol 602-605 ◽

pp. 928-932

Author(s):

Min Li ◽

Yun Wang ◽

Zheng Qian Feng ◽

Wang Li

Keyword(s):

Heat Exchange ◽

Energy Saving ◽

Data Center ◽

Air Conditioning ◽

Data Centers ◽

Cooling Efficiency ◽

Exchange System ◽

Air Conditioning System ◽

Running Time ◽

Heat Exchange System

By studying the energy-saving technologies of air-conditioning system in data centers, we designed a intelligent air conditioning system, improved the cooling efficiency of air conditioning system through a reasonable set of hot and cold aisles, reduced the running time of HVAC by using the intelligent heat exchange system, an provided a reference for energy saving research of air conditioning system of data centers.

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DATA CENTER COOLING EFFICIENCY

Maintaining Mission Critical Systems in a 24/7 Environment ◽

10.1002/9781118041642.ch12 ◽

2011 ◽

pp. 297-316

Keyword(s):

Data Center ◽

Cooling Efficiency ◽

Data Center Cooling

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Optimization of Data Center Cooling Efficiency Using Reduced Order Flow Modeling Within a Flow Network Modeling Approach

Volume 8B: Heat Transfer and Thermal Engineering ◽

10.1115/imece2014-39558 ◽

2014 ◽

Cited By ~ 1

Author(s):

K. Fouladi ◽

A. P. Wemhoff ◽

L. Silva-Llanca ◽

A. Ortega

Keyword(s):

Thermal Efficiency ◽

Data Center ◽

Data Centers ◽

Network Models ◽

Cooling Efficiency ◽

Exergy Destruction ◽

Cfd Simulations ◽

Flow Network ◽

Reduced Order ◽

Efficiency Optimization

Much of the energy use by data centers is attributed to the energy needed to cool the data centers. Thus, improving the cooling efficiency and thermal management of data centers can translate to direct and significant economic benefits. However, data centers are complex systems containing a significant number of components or sub-systems (e.g., servers, fans, pumps, and heat exchangers) that must be considered in any synergistic data center thermal efficiency optimization effort. The Villanova Thermodynamic Analysis of Systems (VTAS) is a flow network tool for performance prediction and design optimization of data centers. VTAS models the thermodynamics, fluid mechanics, and heat transfer inherent to an entire data center system, including contributions by individual servers, the data center airspace, and the HVAC components. VTAS can be employed to identify the optimal cooling strategy among various alternatives by computing the exergy destruction of the overall data center system and the various components in the system for each alternative. Exergy or “available energy” has been used to identify components and wasteful practices that contribute significantly in cooling inefficiency of data centers including room air recirculation — premature mixing of hot and cold air streams in a data center. Flow network models are inadequate in accurately predicting the magnitude of airflow exergy destruction due to simplifying assumptions and the three-dimensional nature of the flow pattern in the room. On the other hand, CFD simulations are time consuming, making them impractical for iterative-based design optimization approaches. In this paper we demonstrate a hybrid strategy, in which a proper orthogonal decomposition (POD) based airflow modeling approach developed from CFD simulation data is implemented in VTAS for predicting the room airflow exergy destruction. The reduced order POD tool in VTAS provides higher accuracy than 1-D flow network models and is computationally more efficient than 3-D CFD simulations. The present VTAS – POD tool has been applied to a data center cell to illustrate the use of exergy destruction minimization as an objective function for data center thermal efficiency optimization.

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