Parametric Study of Hybrid Cooling Solution for Thermal Management of Data Centers

2007 ◽  
Author(s):  
Veerendra Mulay ◽  
Saket Karajgikar ◽  
Dereje Agonafer ◽  
Roger Schmidt ◽  
Madhusudan Iyengar
Keyword(s):  
Thermal Management ◽  
Data Center ◽  
Parametric Study ◽  
Heat Load ◽  
Data Centers ◽  
High Heat ◽  
Inlet Temperature ◽  
Air Cooling ◽  
Air Conditioners ◽  
Hybrid Cooling

The power trend for Server systems continues to grow thereby making thermal management of Data centers a very challenging task. Although various configurations exist, the raised floor plenum with Computer Room Air Conditioners (CRACs) providing cold air is a popular operating strategy. The air cooling of data center however, may not address the situation where more energy is expended in cooling infrastructure than the thermal load of data center. Revised power trend projections by ASHRAE TC 9.9 predict heat load as high as 5000W per square feet of compute servers’ equipment footprint by year 2010. These trend charts also indicate that heat load per product footprint has doubled for storage servers during 2000–2004. For the same period, heat load per product footprint for compute servers has tripled. Amongst the systems that are currently available and being shipped, many racks exceed 20kW. Such high heat loads have raised concerns over limits of air cooling of data centers similar to air cooling of microprocessors. A hybrid cooling strategy that incorporates liquid cooling along with air cooling can be very efficient in these situations. A parametric study of such solution is presented in this paper. A representative data center with 40 racks is modeled using commercially available CFD code. The variation in rack inlet temperature due to tile openings, underfloor plenum depths is reported.

Liquid Cooling for Thermal Management of Data Centers

2008 ◽  
Author(s):  
Veerendra Mulay ◽  
Dereje Agonafer ◽  
Roger Schmidt
Keyword(s):  
Thermal Management ◽  
Data Center ◽  
Heat Load ◽  
Data Centers ◽  
High Heat ◽  
Air Cooling ◽  
Liquid Cooling ◽  
Air Conditioners ◽  
Server Systems ◽  
Heat Loads

The power trend for Server systems continues to grow thereby making thermal management of Data centers a very challenging task. Although various configurations exist, the raised floor plenum with Computer Room Air Conditioners (CRACs) providing cold air is a popular operating strategy. The air cooling of data center however, may not address the situation where more energy is expended in cooling infrastructure than the thermal load of data center. Revised power trend projections by ASHRAE TC 9.9 predict heat load as high as 5000W per square feet of compute servers’ equipment footprint by year 2010. These trend charts also indicate that heat load per product footprint has doubled for storage servers during 2000–2004. For the same period, heat load per product footprint for compute servers has tripled. Amongst the systems that are currently available and being shipped, many racks exceed 20kW. Such high heat loads have raised concerns over limits of air cooling of data centers similar to air cooling of microprocessors. Thermal management of such dense data center clusters using liquid cooling is presented.

Optimal Design and Modeling of Server Cabinets With In-Row Coolers and Air Conditioning Units in a Modular Data Center

2019 ◽  
Author(s):  
Uschas Chowdhury ◽  
Walter Hendrix ◽  
Thomas Craft ◽  
Willis James ◽  
Ankit Sutaria ◽  
...  
Keyword(s):  
Thermal Management ◽  
Data Center ◽  
Hot Spots ◽  
Heat Load ◽  
Air Conditioning ◽  
Data Centers ◽  
Inlet Temperature ◽  
Air Cooling ◽  
Outlet Temperature ◽  
Cold Air

Abstract In a data center, electronic equipment such as server and switches dissipate heat and the corresponding cooling systems contribute to typically 25–35% of total energy consumption. The heat load continues to increase as there is a greater need for miniaturization and convergence. In 2014, data centers in the U.S. consumed an estimated 70 billion kWh, representing about 1.8% of total U.S. electricity consumption. Based on current trend estimates, U.S. data centers are projected to consume approximately 73 billion kWh in 2020 [1]. Many research and strategies are adopted to minimize energy cost. The recommended dry bulb temperature for long-term operation and reliability for air cooling is between 18–27°C and the largest allowable inlet temperature range to operate at is between 5°C and 45°C with American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) enabling much broader allowable zones) [2]. But understanding a proper cooling system is very important especially for thermal management of IT equipment with high heat loads such as 1U or 2U multi-core, high-end servers and blade servers which provide more computing per watt. Many problems like high inlet temperature due to the mixing of hot air with cold air, local hot spots, lower system reliability, increased failure, and downtime may occur. Among many other approaches to managing high-density racks, in-row coolers are used in between racks to provide cold air and minimize local hot spots. This paper describes a computational study being performed by applying in-row coolers for different rack power configuration with and without aisle containment. The power, as well as the number of racks, are varied to study the effect of raised inlet temperature for the IT equipment in a Computational Fluid Dynamics (CFD) model developed in 6SigmaRoom with the help of built-in library items. A comparative analysis is also performed for a typical small-sized non-raised facility to investigate the efficacy and limitations of in-row coolers in thermal management of IT equipment with variation in rack heat load and containment. Several other aspects like a parametric study of variable opening areas of duct between racks and in-row coolers, the variation of operating flow rate and failure scenarios are also studied to find proper flow distribution, uniformity of outlet temperature and predict better performance, energy savings and reliability. The results are presented for general guidance for flexible and quick installation and safe operation of in-row coolers to improve thermal efficiency.

Computational Study of Hybrid Cooling Solution for Thermal Management of Data Centers

2007 ◽  
Author(s):  
Veerendra Mulay ◽  
Saket Karajgikar ◽  
Dereje Agonafer ◽  
Roger Schmidt ◽  
Madshusudan Iyengar ◽  
...  
Keyword(s):  
Thermal Management ◽  
Data Center ◽  
Heat Load ◽  
Data Centers ◽  
Air Cooling ◽  
Operating Strategy ◽  
Cooling Strategy ◽  
Hybrid Cooling ◽  
The Impact ◽  
Heat Loads

The power trend for server systems continues to grow thereby making thermal management of data centers a very challenging task. Although various configurations exist, the raised floor plenum with Computer Room Air Conditioners (CRACs) providing cold air is a popular operating strategy. In prior work, numerous data center layouts employing raised floor plenum and the impact of design parameters such as plenum depth, ceiling height, cold isle location, tile openings and others on thermal performance of data center were presented. The air cooling of data center however, may not address the situation where more energy is expended in cooling infrastructure than the thermal load of data center. Revised power trend projections by ASHRAE TC 9.9 predict heat loads as high as 5000W per square feet of compute servers’ equipment footprint by year 2010. These trend charts also indicate that heat load per product footprint has doubled for storage servers during 2000–2004. For the same period, heat load per product footprint for compute servers has tripled. Amongst the systems that are currently available and being shipped, many racks exceed 20kW. Such high heat loads have raised concerns over air cooling limits of data centers similar to that of microprocessors. A hybrid cooling strategy that incorporates liquid cooling along with air cooling can be very efficient in such situations. The impact of such an operating strategy on thermal management of data center is discussed in this paper. A representative data center is modeled using commercially available CFD code. The change in rack temperature gradients, recirculation cells and CRAC demand due to use of hybrid cooling is presented in a detailed parametric study. It is shown that the hybrid cooling strategy improves the cooling of data center which may enable full population of rack and better management of system infrastructure.

Perimeter Cooling Unit and Localized Row-Based Cooling Unit Transient Air Flow Effects Modeling and Characterization in Data Centers

2015 ◽  
Author(s):  
Tianyi Gao ◽  
James Geer ◽  
Bahgat G. Sammakia ◽  
Russell Tipton ◽  
Mark Seymour
Keyword(s):  
Thermal Management ◽  
Data Center ◽  
Data Centers ◽  
Cooling System ◽  
Air Flow ◽  
Cooling Systems ◽  
Dynamic Thermal Management ◽  
Hybrid Cooling ◽  
Cooling Unit ◽  
Cooling Air

Cooling power constitutes a large portion of the total electrical power consumption in data centers. Approximately 25%∼40% of the electricity used within a production data center is consumed by the cooling system. Improving the cooling energy efficiency has attracted a great deal of research attention. Many strategies have been proposed for cutting the data center energy costs. One of the effective strategies for increasing the cooling efficiency is using dynamic thermal management. Another effective strategy is placing cooling devices (heat exchangers) closer to the source of heat. This is the basic design principle of many hybrid cooling systems and liquid cooling systems for data centers. Dynamic thermal management of data centers is a huge challenge, due to the fact that data centers are operated under complex dynamic conditions, even during normal operating conditions. In addition, hybrid cooling systems for data centers introduce additional localized cooling devices, such as in row cooling units and overhead coolers, which significantly increase the complexity of dynamic thermal management. Therefore, it is of paramount importance to characterize the dynamic responses of data centers under variations from different cooling units, such as cooling air flow rate variations. In this study, a detailed computational analysis of an in row cooler based hybrid cooled data center is conducted using a commercially available computational fluid dynamics (CFD) code. A representative CFD model for a raised floor data center with cold aisle-hot aisle arrangement fashion is developed. The hybrid cooling system is designed using perimeter CRAH units and localized in row cooling units. The CRAH unit supplies centralized cooling air to the under floor plenum, and the cooling air enters the cold aisle through perforated tiles. The in row cooling unit is located on the raised floor between the server racks. It supplies the cooling air directly to the cold aisle, and intakes hot air from the back of the racks (hot aisle). Therefore, two different cooling air sources are supplied to the cold aisle, but the ways they are delivered to the cold aisle are different. Several modeling cases are designed to study the transient effects of variations in the flow rates of the two cooling air sources. The server power and the cooling air flow variation combination scenarios are also modeled and studied. The detailed impacts of each modeling case on the rack inlet air temperature and cold aisle air flow distribution are studied. The results presented in this work provide an understanding of the effects of air flow variations on the thermal performance of data centers. The results and corresponding analysis is used for improving the running efficiency of this type of raised floor hybrid data centers using CRAH and IRC units.

Raised Floor Hybrid Cooled Data Center: Effect on Rack Inlet Air Temperatures When In Row Cooling Units are Installed Between the Racks

2015 ◽  
Author(s):  
Tianyi Gao ◽  
James Geer ◽  
Russell Tipton ◽  
Bruce Murray ◽  
Bahgat G. Sammakia ◽  
...  
Keyword(s):  
Flow Rate ◽  
Data Center ◽  
Heat Load ◽  
Data Centers ◽  
Cooling System ◽  
Air Flow ◽  
Inlet Temperature ◽  
Air Flow Rate ◽  
Air Temperatures ◽  
Cooling Unit

The heat dissipated by high performance IT equipment such as servers and switches in data centers is increasing rapidly, which makes the thermal management even more challenging. IT equipment is typically designed to operate at a rack inlet air temperature ranging between 10 °C and 35 °C. The newest published environmental standards for operating IT equipment proposed by ASHARE specify a long term recommended dry bulb IT air inlet temperature range as 18°C to 27°C. In terms of the short term specification, the largest allowable inlet temperature range to operate at is between 5°C and 45°C. Failure in maintaining these specifications will lead to significantly detrimental impacts to the performance and reliability of these electronic devices. Thus, understanding the cooling system is of paramount importance for the design and operation of data centers. In this paper, a hybrid cooling system is numerically modeled and investigated. The numerical modeling is conducted using a commercial computational fluid dynamics (CFD) code. The hybrid cooling strategy is specified by mounting the in row cooling units between the server racks to assist the raised floor air cooling. The effect of several input variables, including rack heat load and heat density, rack air flow rate, in row cooling unit operating cooling fluid flow rate and temperature, in row coil effectiveness, centralized cooling unit supply air flow rate, non-uniformity in rack heat load, and raised floor height are studied parametrically. Their detailed effects on the rack inlet air temperatures and the in row cooler performance are presented. The modeling results and corresponding analyses are used to develop general installation and operation guidance for the in row cooler strategy of a data center.

Energy-Efficient Air Cooling of Data Centers at 2000 W/ft2

2009 ◽  
Author(s):  
Magnus K. Herrlin ◽  
Michael K. Patterson
Keyword(s):  
Energy Efficiency ◽  
Data Center ◽  
Energy Efficient ◽  
Data Centers ◽  
High Heat ◽  
High Density ◽  
Cfd Modeling ◽  
Air Cooling ◽  
Capital Costs ◽  
Design Considerations

Increased Information and Communications Technology (ICT) capability and improved energy-efficiency of today’s server platforms have created opportunities for the data center operator. However, these platforms also test the ability of many data center cooling systems. New design considerations are necessary to effectively cool high-density data centers. Challenges exist in both capital costs and operational costs in the thermal management of ICT equipment. This paper details how air cooling can be used to address both challenges to provide a low Total Cost of Ownership (TCO) and a highly energy-efficient design at high heat densities. We consider trends in heat generation from servers and how the resulting densities can be effectively cooled. A number of key factors are reviewed and appropriate design considerations developed to air cool 2000 W/ft2 (21,500 W/m2). Although there are requirements for greater engineering, such data centers can be built with current technology, hardware, and best practices. The density limitations are shown primarily from an airflow management and cooling system controls perspective. Computational Fluid Dynamics (CFD) modeling is discussed as a key part of the analysis allowing high-density designs to be successfully implemented. Well-engineered airflow management systems and control systems designed to minimize airflow by preventing mixing of cold and hot airflows allow high heat densities. Energy efficiency is gained by treating the whole equipment room as part of the airflow management strategy, making use of the extended environmental ranges now recommended and implementing air-side air economizers.

Energy Simulations of Data Centers With Hybrid Liquid/Air Cooling and Waste Heat Re-Use

2016 ◽  
Author(s):  
Seungho Mok ◽  
Yogendra K. Joshi ◽  
Satish Kumar ◽  
Ronald R. Hutchins
Keyword(s):  
Data Center ◽  
Computational Models ◽  
Data Centers ◽  
Waste Heat ◽  
Cooling System ◽  
Cooling Water ◽  
Maximum Load ◽  
Air Cooling ◽  
Direct Expansion ◽  
Hybrid Cooling

This study focuses on developing computational models for hybrid or liquid cooled data centers that may reutilize waste heat. A data center with 17 fully populated racks with IBM LS20 blade servers, which consumes 408 kW at the maximum load, is considered. The hybrid cooling system uses a liquid to remove the heat produced by high power components, while the remaining low power components are cooled by air. The paper presents three hybrid cooling scenarios. For the first two cases, air is cooled by direct expansion (DX) cooling system with air-side economizer. Unlike the cooling air, two different approaches for cooling water are investigated: air-cooled chiller and ground water through liquid-to-liquid heat exchanger. Waste heat re-use for pre-heating building water in co-located facilities is also investigated for the second scenario. In addition to the hybrid cooling models, a fully liquid cooling system is modeled as the third scenario for comparison with hybrid cooling systems. By linking the computational models, power usage effectiveness (PUE) for all scenarios can be calculated for selected geographical locations and data center parameters. The paper also presents detailed analyses of the cooling components considered and comparisons of the PUE results.

Dynamic Analysis of Hybrid Cooling Data Centers Subjects to the Failure of CRAC Units

2013 ◽  
Author(s):  
Tianyi Gao ◽  
Emad Samadiani ◽  
Roger Schmidt ◽  
Bahgat Sammakia
Keyword(s):  
Data Center ◽  
Heat Exchangers ◽  
Data Centers ◽  
Cooling System ◽  
Normal Operation ◽  
Air Cooling ◽  
Rear Door ◽  
Hybrid Cooling ◽  
Air Cooling System ◽  
The Impact

Thermal management of high power data centers poses challenges due to the high operational cost which is made worse due to the many inefficiencies that arise in them. Additional challenges arise due to the dynamic behaviors that occur during normal operation, and also during emergencies such as power outages or failure of some or all of the cooling equipment. Water and hybrid air plus water cooled data centers are an alternate cooling solution combining liquid cooling systems, such as rear door heat exchangers located within the racks themselves, in addition to the traditional raised floor cold aisle air cooling system. Such a solution may be used when some of the equipment in a data center is upgraded to higher end and higher power equipment which may not be manageable with the existing air cooling system. For a data center with a hybrid cooling system, the cold air supply and the cold water supply should increase in case of an emergency, such as a CRAC (Computer Room Air Conditioner) units’ failure. In this paper, a detailed computational study is conducted to investigate the dynamic response of the impact of a CRAC failure on both water side and air side in a representative hybrid cooling room. The room studied is an air cooled data center using the common cold aisle approach, with rear door heat exchangers installed on all of the racks. CRAC failure is investigated in a hybrid cooling room. The variation and fluctuation in an average rack inlet temperature, and inlet temperatures at different detail locations are presented in plots, showing the dynamic performance of a hybrid cooling data center subjected to the different CRAC failure scenarios. Different response time studies are also presented in this paper.

Study of CFD-Based Raised-Floor Data Center Cooling With Parametric CRAC Turbofan Blower Airflow Patterns

2021 ◽  
Author(s):  
Zhihang Song ◽  
Wan Chen
Keyword(s):  
Thermal Management ◽  
Data Center ◽  
Data Centers ◽  
Air Cooling ◽  
Flow Conditions ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Data Center Cooling ◽  
Computational Fluid Dynamics Cfd ◽  
Tile Flow

Abstract Commonly encountered thermal management challenges of today’s rapidly changing power density, raised-floor hot/cold aisle data centers include typically uncontrollable tile flow non-uniformity along the above-floor cold aisle. For example, the operational cooling provision intensity near the Computer Room Airflow Conditioner (CRAC) unit can be far less than that on the other side (far away from the CRAC unit). This undesired trend leads to an unbalanced aisle-level air cooling and subsequent inefficient power consumption. In this study, the CRAC turbofan blower flow boundary conditions were thoroughly investigated. Computational Fluid Dynamics (CFD) based simulations were employed to describe and evaluate the differently configured CRAC turbofan blower flow conditions (i.e., normal, angled, and sheared CRAC flow patterns) as well as their impacts upon the air cooling performance. This work indicates that the considered turbofan blower boundary condition, together with their underlying transportation mechanism within the plenum, might contribute an essential influence to the flow structure adjacent to the tile perforations. In particular, it was found that the sheared CRAC turbofan blower airflow pattern is capable of giving rise to favorable tile flow straightening manners. This finding further promotes an improvement of the consequently obtained aisle-level air cooling effectiveness and efficiencies, contributing to more advanced data center thermal management in the future.

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