Net-Zero Water (NZW) Reuse Desiccant Assisted Evaporative Cooling System for Data Centers

2019 ◽  
Author(s):  
David Okposio ◽  
A. G. Agwu Nnanna ◽  
Harvey Abramowitz
Keyword(s):  
Surface Area ◽  
Data Center ◽  
Data Centers ◽  
Waste Heat ◽  
Cooling System ◽  
Evaporative Cooling ◽  
Water Flow Rate ◽  
Peltier Effect ◽  
Water Recovery ◽  
Data Center Cooling

Abstract The cooling effect of evaporative cooling systems is well documented in literature. Evaporative cooling however introduces humidity into the cooled space, which is unsuitable for data centers. Desiccants (liquid, solid or composites) adsorb moisture from the cooled air to control humidity and is regenerated using waste heat from the data center. This work is an experimental and theoretical investigation of the use of desiccant assisted evaporative cooling for data center cooling according to ASHRAE thermal guideline TC 9.9 . The thickness of the cooling pads is varied with specific surface area, velocity of air through the pad measured, the product of the air velocity and surface area yields the volumetric flowrate of the air, the water flow rate varied as well. The configuration is such that the rotary desiccant wheel (impregnated with silica gel) comes after the evaporative cooler. A novel water recovery system using the Peltier effect is proposed to recover moisture from the return air stream thereby optimizing the water consumption of evaporative cooling technology and providing suitable air quality for data center cooling.

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.

Failure Resistant Data Center Cooling Control Through Model-Based Thermal Zone Mapping

2012 ◽  
Author(s):  
Rongliang Zhou ◽  
Zhikui Wang ◽  
Cullen E. Bash ◽  
Tahir Cader ◽  
Alan McReynolds
Keyword(s):  
Data Center ◽  
Data Centers ◽  
Cooling System ◽  
Cooling Power ◽  
Cooling Efficiency ◽  
Model Based ◽  
Thermal Zone ◽  
Cooling Control ◽  
Data Center Cooling ◽  
Thermal Status

Due to the tremendous cooling costs, data center cooling efficiency improvement has been actively pursued for years. In addition to cooling efficiency, the reliability of the cooling system is also essential for guaranteed uptime. In traditional data center cooling system design with N+1 or higher redundancy, all the computer room air conditioning (CRAC) units are either constantly online or cycled according to a predefined schedule. Both cooling system configurations, however, have their respective drawbacks. Data centers are usually over provisioned when all CRAC units are online all the time, and hence the cooling efficiency is low. On the other hand, although cooling efficiency can be improved by cycling CRAC units and turning off the backups, it is difficult to schedule the cycling such that sufficient cooling provisioning is guaranteed and gross over provisioning is avoided. In this paper, we aim to maintain the data center cooling redundancy while achieving high cooling efficiency. Using model-based thermal zone mapping, we first partition data centers to achieve the desired level of cooling influence redundancy. We then design a distributed controller for each of the CRAC units to regulate the thermal status within its zone of influence. The distributed controllers coordinate with each other to achieve the desired data center thermal status using the least cooling power. When CRAC units or their associated controllers fail, racks in the affected thermal zones are still within the control “radius” of other decentralized cooling controllers through predefined thermal zone overlap, and hence their thermal status is properly managed by the active CRAC units and controllers. Using this failure resistant data center cooling control approach, both cooling efficiency and robustness are achieved simultaneously. A higher flexibility in cooling system maintenance is also expected, since the distributed control system can automatically adapt to the new cooling facility configuration incurred by maintenance.

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.

Numerical Study to Analyze the Effects of Hot/Cold Aisle Configurations on Heat Transfer Phenomenon in a Data Center

2013 ◽  
Author(s):  
Kamran Nazir ◽  
Naveed Durrani ◽  
Imran Akhtar ◽  
M. Saif Ullah Khalid
Keyword(s):  
Heat Transfer ◽  
Data Center ◽  
Data Centers ◽  
Cooling System ◽  
Numerical Study ◽  
High Energy ◽  
Research Area ◽  
Transfer Phenomenon ◽  
Heat Transfer Phenomenon ◽  
Active Research

Due to high energy demands of data centers and the energy crisis throughout the world, efficient heat transfer in a data center is an active research area. Until now major emphasis lies upon study of air flow rate and temperature profiles for different rack configurations and tile layouts. In current work, we consider different hot aisle (HA) and cold aisle (CA) configurations to study heat transfer phenomenon inside a data center. In raised floor data centers when rows of racks are parallel to each other, in a conventional cooling system, there are equal number of hot and cold aisles for odd number of rows of racks. For even number of rows of racks, whatever configuration of hot/cold aisles is adopted, number of cold aisles is either one greater or one less than number of hot aisles i.e. two cases are possible case A: n(CA) = n(HA) + 1 and case B: n(CA) = n(HA) − 1 where n(CA), n(HA) denotes number of cold and hot aisles respectively. We perform numerical simulations for two (case1) and four (case 2) racks data center. The assumption of constant pressure below plenum reduces the problem domain to above plenum area only. In order to see which configuration provides higher heat transfer across servers, we measure heat transfer across servers on the basis of temperature differences across racks, and in order to validate them, we find mass flow rates on rack outlet. On the basis of results obtained, we conclude that for even numbered rows of rack data center, using more cold aisles than hot aisles provide higher heat transfer across servers. These results provide guidance on the design and layout of a data center.

scholarly journals A Calculation Model for Typical Data Center Cooling System

2019 ◽  
Vol 1304 ◽  
pp. 012022
Author(s):  
Jianwen Huang ◽  
Cheng Chen ◽  
Guiyang Guo ◽  
Zhang Zhang ◽  
Zhen Li
Keyword(s):  
Data Center ◽  
Cooling System ◽  
Calculation Model ◽  
Typical Data ◽  
Data Center Cooling

scholarly journals Thermal Performance Evaluation of a Data Center Cooling System under Fault Conditions

Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2996 ◽  
Author(s):  
Jinkyun Cho ◽  
Beungyong Park ◽  
Yongdae Jeong
Keyword(s):  
Water Supply ◽  
Thermal Performance ◽  
Data Center ◽  
Temperature Increase ◽  
Data Centers ◽  
Cooling System ◽  
Backup System ◽  
Air Supply ◽  
Chilled Water ◽  
Rapid Temperature

If a data center experiences a system outage or fault conditions, it becomes difficult to provide a stable and continuous information technology (IT) service. Therefore, it is critical to design and implement a backup system so that stability can be maintained even in emergency (unforeseen) situations. In this study, an actual 20 MW data center project was analyzed to evaluate the thermal performance of an IT server room during a cooling system outage under six fault conditions. In addition, a method of organizing and systematically managing operational stability and energy efficiency verification was identified for data center construction in accordance with the commissioning process. Up to a chilled water supply temperature of 17 °C and a computer room air handling unit air supply temperature of 24 °C, the temperature of the air flowing into the IT server room fell into the allowable range specified by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers standard (18–27 °C). It was possible to perform allowable operations for approximately 320 s after cooling system outage. Starting at a chilled water supply temperature of 18 °C and an air supply temperature of 25 °C, a rapid temperature increase occurred, which is a serious cause of IT equipment failure. Due to the use of cold aisle containment and designs with relatively high chilled water and air supply temperatures, there is a high possibility that a rapid temperature increase inside an IT server room will occur during a cooling system outage. Thus, the backup system must be activated within 300 s. It is essential to understand the operational characteristics of data centers and design optimal cooling systems to ensure the reliability of high-density data centers. In particular, it is necessary to consider these physical results and to perform an integrated review of the time required for emergency cooling equipment to operate as well as the backup system availability time.

Applicability Research on Evaporative Cooling Technology in Hunan Province

2014 ◽  
Vol 1070-1072 ◽  
pp. 1679-1683
Author(s):  
Qin Ouyang ◽  
Guang Xiao Kou ◽  
Min Ouyang
Keyword(s):  
Energy Consumption ◽  
Air Conditioning ◽  
Waste Heat ◽  
Cooling System ◽  
Evaporative Cooling ◽  
Hunan Province ◽  
Design Parameters ◽  
Climate Conditions ◽  
Energy Saving Potential ◽  
Evaporative Cooling System

According to the climate conditions of Hunan province and the design parameters related to air conditioning, the energy consumption and the related characteristics of the liquid desiccant evaporative cooling system (LDECS) are compared with primary return air conditioning system. The results show that energy consumption of LDECS can be decreased by 11.78% compared to the primary return air system. LDECS has a certain degree of energy saving potential in Hunan province, especially when waste heat is available.

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.

Airflow Uniformity Through Perforated Tiles in a Raised-Floor Data Center

2005 ◽  
Author(s):  
James W. VanGilder ◽  
Roger R. Schmidt
Keyword(s):  
Data Center ◽  
Cooling System ◽  
Design Parameters ◽  
Airflow Rate ◽  
Simple Estimate ◽  
Cfd Models ◽  
System A ◽  
Data Center Cooling ◽  
Floor Plans ◽  
The Impact

The maximum equipment power density (e.g. in power/rack or power/area) that may be deployed in a typical raised-floor data center is limited by perforated tile airflow. In the design of a data center cooling system, a simple estimate of mean airflow per perforated tile is typically made based on the number of CRAC’s and number of perforated tiles (and possibly a leakage airflow estimate). However, in practice, many perforated tiles may deliver substantially more or less than the mean, resulting in, at best, inefficiencies and, at worst, equipment failure due to inadequate cooling. Consequently, the data center designer needs to estimate the magnitude of variations in perforated tile airflow prior to construction or renovation. In this paper, over 240 CFD models are analyzed to determine the impact of data-center design parameters on perforated tile airflow uniformity. The CFD models are based on actual data center floor plans and the CFD model is verified by comparison to experimental test data. Perforated tile type and the presence of plenum obstructions have the greatest potential influence on airflow uniformity. Floor plan, plenum depth, and airflow leakage rate have modest effect on uniformity and total airflow rate (or average plenum pressure) has virtually no effect. Good uniformity may be realized by using more restrictive (e.g. 25%-open) perforated tiles, minimizing obstructions and leakage airflow, using deeper plenums, and using rectangular floor plans with standard hot aisle/cold aisle arrangements.

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