Rack Level Study of Hybrid Liquid/Air Cooled Servers: The Impact of Flow Distribution and Pumping Configuration on Central Processing Units Temperature

The flow distribution and central processing unit (CPU) temperatures inside a rack of thirty 1 U (single rack unit) Sun Fire V20z servers retrofitted with direct-to-chip liquid cooling and two coolant pumping configuration scenarios (central and distributed) are investigated using the EPANET open source network flow software. The results revealed that the servers in the top of the rack and close to the cooling distribution unit can receive up 30% higher flow rate than the servers in the bottom of the rack, depending on the pumping scenario. This results in a variation in the CPU temperatures depending on the position in the rack. Optimization analysis is carried out and shows that increasing the flow distribution manifold’s dimensions can reduce the flow variation through the servers and increase the total coolant flow rate in the rack by roughly 10%. In addition, activating the small pumps in the direct-to-chip liquid cooling loops inside the servers (distributed pumping) resulted in an increase of 2 °C in the CPU temperatures at the high computational workload

Holistic Study of Thermal Management in Direct Liquid Cooled Data Centres: from the Chip to the Environment

The IT (Information Technology) infrastructure power consumption constitutes a large portion of global electricity consumption and a large proportion of this energy is to maintain an acceptable thermal environment for the IT equipment. Therefore, it is important to understand and improve the thermal and energy management of data centres for lower cost and higher sustainability. Toward this goal, Direct Contact Liquid Cooled (DCLC) servers, where liquid loop heat exchangers are attached to the CPU, were proposed to study the use of chiller-less energy efficient data centre. Thirty Sun Fire V20z servers in a data centre rack have their CPUs water cooled with the remaining components air cooled, together with a rear door heat exchanger to capture this air heat flow. The heat generated by the servers is ultimately transferred to the environment using an Air Handling Unit (AHU). The AHU was fitted with a water spray system to increase the heat transfer capacity. The designed DCLC system was tested and characterised in terms of power consumption and thermal performance. The design successfully provided stable inlet coolant temperature (±1℃) to the IT despite the variation in the IT workload and environmental conditions. Activating the spray reduced the thermal resistance of the AHU heat exchanger (HE) by 50%. However, the power consumption and pressure drop across the HE was increased. The flow distribution and the coolant pumping configurations of centralised (where the coolant is pumped by two central pumps connected in series) and distributed (where small pumps inside the servers are activated) was investigated. The EPANET software was used to analyse the flow and showed that the servers in the top of the rack receive a higher flow rate (by approximately 30%) than the servers in the bottom of the rack. This resulted in a variation in the CPU temperatures of different servers. Optimisation analysis proposed increasing the manifolds size to improve the flow rate and reduce the flow maldistribution. In the distributed pumping case, the CPUs temperature showed to be 2℃ higher compared with the central pumping case for the high IT workload. The rack inlet temperature was tested in the range of the ASHRAE W4 envelope in terms of CPU temperatures, power consumption and computational efficiency. Increasing the coolant inlet temperature resulted in high energy saving in the AHU, while the rack energy consumption increases marginally in idle operation and considerably more in high IT workloads. This results in an improvement in the energy effectiveness of 17% but a deterioration in the computational efficiency of 4%. Finally, a parallel study was carried out to investigate the droplet evaporation over heated surfaces which ultimately be used in studying sprays in the AHU or in direct on chip cooling via evaporation. A novel experimental design was proposed to track the lifetime of any droplet size that span the surface tension to gravitydominated regimes. A theoretical model was also proposed to predict the droplet lifetime based on the initial contact angle, contact radius and the receding contact angle. The model predicted the droplet evaporation over hydrophobic surfaces with good accuracy of an error less than 4% while under estimated the evaporation with hydrophilic surfaces

Energy: A continuing bibliography with indexes, issue 40, January 1984

This bibliography lists 775 reports, articles and other documents introduced into the NASA scientific and technical information system from October 1, 1983 through December 31, 1983

Electromagnetic Radiation

The application of electromagnetic radiation in modern life is one of the most developing technologies. In this timely book, the authors comprehensively treat two integrated aspects of electromagnetic radiation, theory and application. It covers a wide scope of practical topics, including medical treatment, telecommunication systems, and radiation effects. The book sections have clear presentation, some state of the art examples, which makes this book an indispensable reference book for electromagnetic radiation applications

Direct-to-chip liquid cooling for reducing power consumption in a subarctic supercomputer centre

Reduction of data centre power consumption is a timely challenge. Waste heat reuse is another focus area when developing energy efficient and sustainable data centres. And these two issues are interconnected through liquid cooling of server racks and/or direct-to-chip liquid cooling. Both of these solutions make it possible to transfer a significant proportion of the waste heat energy back to profitable use. Nevertheless, the heat reusing opportunity is not the only benefit direct-to-chip liquid cooling may offer. Another benefit is the notable reduction of power consumption related to cooling fans associated with server blades and rack-level cooling systems. To evaluate this benefit, we performed power consumption and performance measurements in a subarctic supercomputer centre hosting a cluster of 632 blade nodes. Our study concentrated on a 47-node subset that we analysed when the servers were executing the LINPACK benchmark. Our conclusion is that direct-to-chip liquid cooling can reduce the total power consumption, in this case, up to 14.4% depending on the inlet air temperature.Peer reviewe

Research and Technology Objectives and Plans Summary (RTOPS)

This publication represents the NASA research and technology program for FY-93. It is a compilation of the Summary portions of each of the RTOP's (Research and Technology Objectives and Plans) used for management review and control of research currently in progress throughout NASA. The RTOP Summary is designed to facilitate communication and coordination among concerned technical personnel in government, in industry, and in universities. The first section containing citations and abstracts of the RTOP's is followed by four indexes: Subject, Technical Monitor, Responsible NASA Organization, and RTOP Number

A Report by the Climate Change Science Program and the Subcommittee on Global Change Research

This strategic plan has been prepared by the 13 federal agencies participating in the CCSP, with coordination by the CCSP staff under the leadership of Dr. Richard H. Moss. This strategic plan responds to the President's direction that climate change research activities be accelerated to provide the best possible scientific information to support public discussion and decision-making on climate-related issues.The plan also responds to Section 104 of the Global Change Research Act of 1990, which mandates the development and periodic updating of a long-term national global change research plan coordinated through the National Science and Technology Council.This is the first comprehensive update of a strategic plan for U.S. global change and climate change research since the original plan for the U.S. Global Change Research Program was adopted at the inception of the program in 1989

Research and Technology Objectives and Plans Summary (RTOPS)

The NASA research and technology program for FY 1990 is presented. The summary portions is compiled of each of the RTOPs (Research and Technology Objectives and Plans) used for management review and control of research currently in progress throughout NASA. The RTOP summary is designed to facilitate communication and coordination among concerned technical personnel in government, industry, and universities. The first section containing citations and abstracts of the RTOPs is followed by four indices: Subject; Technical Monitor; Responsible NASA Organization; and RTOP number

Annual Report of the University, 1992-1993, Volumes 1-4

SIGNIFICANT DEVELOPMENTS Preparation, approval by President Peck, delivery to NMCHE of UNM\u27s response to House Memorials 38 and 25 (on minorities and women). Development and packaging of a presentation on minorities at UNM to Hispanic community people and organizations. Renewal of faculty instructional workload report and other information for use by President Peck and others in the President\u27s Council in testimony to the legislature on accountability by faculty. Significant workload and contributions to WICHE\u27s Diversity Project: - responses to long questionnaire - projected demographics - substitution for O. Forbes on planning for diversity Reprogramming of obsolete computer program of the University of Southern California\u27s Faculty Planning Model. Work remains incomplete. Support and staff work for University Planning Council, Faculty Senate Long Range Planning Committee, Senate President, Senate Budget Committee, Student Learning Outcomes Assessment Committee, Admissions and Registration Committee, Staff Council; Graduate Petition and grade Review Subcommittee Service to NMCHE\u27s Outcomes Assessment Advisory Group; NMCHE\u27s review group on diversity plans Service on Albuquerque Business/Education Compact Conducted several special data analyses to provide user outcome information for the Center for Academic Program Support (CAPS). Wrote reports to summarize analyses. Served in an advisory capacity to VP Zuniga Forbes for the two surveys (Campus Climate for Diversity, ACT Student Opinion Survey) and helped to draw the sample for the ACT survey. Conducted secondary analyses and prepared report of all analyses of the Freshman Survey (CIRP) for VP Zuniga Forbes. Gave presentation of CIRP findings to the Regents Subcommittee on Student Affairs. Conducted secondary analyses and prepared report of all analyses of the Campus Climate for Diversity Survey for VP Zuniga Forbes