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.

Thermal Control Strategies for Reliable and Energy-Efficient Data Centers

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Rehan Khalid ◽  
Aaron P. Wemhoff
Keyword(s):  
Data Center ◽  
Energy Efficient ◽  
Cooling System ◽  
System Level ◽  
Component Level ◽  
Simple Method ◽  
Control Schemes ◽  
Data Center Cooling ◽  
Efficient Data ◽  
The Impact

Two self-developed control schemes, ON/OFF and supervisory control and data acquisition (SCADA), were applied on a hybrid evaporative and direct expansion (DX)-based model data center cooling system to assess the impact of controls on reliability and energy efficiency. These control schemes can be applied independently or collectively, thereby saving the energy spent on mechanical refrigeration by using airside economization and/or evaporative cooling. Various combinations of system-level controls and component-level controls are compared to a baseline no-controls case. The results show that reliability is consistently met by employing only sophisticated component-level controls. However, the recommended conditions are met approximately 50% of the simulated time by employing system-level controls only (i.e., SCADA) but with a reduction in data center cooling system power usage effectiveness (PUE) values from 3.76 to 1.42. Moreover, the recommended conditions are met at all averaged times with an even lower cooling system PUE of 1.13 by combining system-level controls only (SCADA and ON/OFF controls). Thus, the study introduces a simple method to compare control schemes for reliable and energy-efficient data center operation. The work also highlights a potential source of capital expenses and operating expenses savings for data center owners by switching from expensive built-in component-based controls to inexpensive, yet effective, system-based controls that can easily be imbedded into existing data center infrastructure systems management.

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

Compact Modeling of Data Center Air Containment Systems

2013 ◽  
Author(s):  
Xuanhang (Simon) Zhang ◽  
James W. VanGilder ◽  
Christopher M. Healey ◽  
Zachary R. Sheffer
Keyword(s):  
Numerical Model ◽  
Data Center ◽  
Compact Model ◽  
Scale Model ◽  
Compact Modeling ◽  
Full Data ◽  
Modeling Tools ◽  
Cfd Models ◽  
Data Center Cooling ◽  
Flow Boundaries

The practice of ducting racks to a dropped ceiling or containing entire cold or hot aisles in data centers is being implemented with more frequency in an attempt to improve reliability and efficiency. While CFD and other numerical modeling tools are widely used to optimize data center cooling, they are not particularly effective at modeling containment systems; the performance of such systems is dominated by small and complex leakage paths (e.g., through, around, and under racks), which are difficult or impossible to include in a practical full-scale model. We propose a compact model which uses a flow network to determine airflow rates inside containment systems while the traditional “parent” numerical model continues to handle predictions in the rest of the facility. The two models are coupled at flow boundaries such as where ducting meets a dropped ceiling and leakage paths cross rack surfaces. The compact-model approach has the opportunity to be much faster and more robust than fully-explicit CFD models since leakage path resistances can be established through experimental measurements. We discuss the characterization of rack leakage paths and demonstrate the use of the compact model in a full data center simulation in which the role of parent numerical model is played by a potential flow model.

Exergy Analysis of Data Center Thermal Management Systems

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Amip J. Shah ◽  
Van P. Carey ◽  
Cullen E. Bash ◽  
Chandrakant D. Patel
Keyword(s):  
Energy Efficiency ◽  
Thermal Management ◽  
Data Center ◽  
Experimental Validation ◽  
Irreversible Process ◽  
Exergy Analysis ◽  
Cooling System ◽  
Available Energy ◽  
Thermal Management System ◽  
Data Center Cooling

The modeling of recirculation patterns in air-cooled data centers is of interest to ensure adequate thermal management of computer racks at increased heat densities. Most metrics that describe recirculation are based exclusively on temperature inside the data center, and therefore fail to provide adequate information regarding the energy efficiency of the thermal infrastructure. This paper addresses this limitation through an exergy analysis of the data center thermal management system. The approach recognizes that the mixing of hot and cold streams in the data center airspace is an irreversible process and must therefore lead to a loss of exergy. Experimental validation in a test data center confirms that such an exergy-based characterization in the cold aisle reflects the same recirculation trends as suggested by traditional temperature-based metrics. Further, by extending the exergy-based model to include irreversibilities from other components of the thermal architecture, it becomes possible to quantify the amount of available energy supplied to the cooling system that is being utilized for thermal management purposes. The energy efficiency of the entire data center cooling system can then be collapsed into the single metric of net exergy loss. When evaluated against a ground state of the external ambience, this metric enables an estimate of how much of the energy emitted into the environment could potentially be harnessed in the form of useful work. Thus, this paper successfully demonstrates that the proposed exergy-based approach can provide a foundation upon which the data center cooling system can be simultaneously evaluated for thermal manageability and energy efficiency.

Optimization of the Adsorber in an Adsorption Solar-Powered Cooling System

2005 ◽  
Author(s):  
Anne Ranes ◽  
Patrick Phelan ◽  
Rafael Pacheco ◽  
Anastasios Frantzis ◽  
Lionel Metchop
Keyword(s):  
Cooling System ◽  
Design Parameters ◽  
Adsorption System ◽  
Bed Porosity ◽  
System A ◽  
Solar Powered ◽  
Experimental Trials ◽  
The Cost ◽  
Fin Thickness ◽  
Parameter Values

The adsorption solar-powered cooling system is one of several types of solar-powered cooling systems currently under development. Increasing the efficiency and decreasing the cost of this system will make it a commercially viable alternative to traditional refrigeration systems. The objective of this project was to optimize the adsorber in the adsorption system. A mathematical model of the refrigerant distribution within a cylindrical adsorber was developed using equations from Chua et al. [1]. The simulation revealed effects of varying design parameters on the theoretical refrigerant mass flow rate, which is directly proportional to the system refrigeration capacity. These results indicated parameter values to be used in designing the adsorber. It was found that decreased particle radius, decreased bed porosity, increased pipe radius, increased adsorber radius, and increased fin thickness all positively affect the performance of the adsorption system. Further simulation and experimental trials are recommended to verify these results.

Coupled Calculations of Data Center Cooling and Power Distribution Systems

2021 ◽  
Author(s):  
Aaron P. Wemhoff ◽  
Faisal Ahmed
Keyword(s):  
Data Center ◽  
Power Distribution ◽  
Distribution System ◽  
Distribution Systems ◽  
Cooling System ◽  
Statistical Significance ◽  
Total System ◽  
Power Distribution System ◽  
Data Center Cooling ◽  
System Power

Abstract Physics-based modeling aids in designing efficient data center power and cooling systems. These systems have traditionally been modeled independently under the assumption that the inherent coupling of effects between the systems has negligible impact. This study tests the assumption through uncertainty quantification of models for a typical 300 kW data center supplied through either an AC-based or DC-based power distribution system. A novel calculation scheme is introduced that couples the calculations of these two systems to estimate the resultant impact on predicted Power Usage Effectiveness (PUE), Computer Room Air Conditioning (CRAC) return temperature, total system power requirement, and system power loss values. A two-sample z-test for comparing means is used to test for statistical significance with 95% confidence. The power distribution component efficiencies are calibrated to available published and experimental data. The predictions for a typical data center with an AC-based system suggest that the coupling of system calculations results in statistically significant differences for the cooling system PUE, the overall PUE, the CRAC return air temperature, and total electrical losses. However, none of the tested metrics are statistically significant for a DC-based system. The predictions also suggest that a DC-based system provides statistically significant lower overall PUE and electrical losses compared to the AC-based system, but only when coupled calculations are used. These results indicate that the coupled calculations impact predicted general energy efficiency metrics and enable statistically significant conclusions when comparing different data center cooling and power distribution strategies.

Reducing the Risk of Natural Ventilation With Flexible Design

Solar Energy ◽  
2006 ◽  
Author(s):  
Lara V. Greden ◽  
Leon R. Glicksman ◽  
Gabriel Lo´pez-Betanzos
Keyword(s):  
Natural Ventilation ◽  
Energy Savings ◽  
Cooling System ◽  
Building Energy ◽  
Design Parameters ◽  
Energy Prices ◽  
Flexible Design ◽  
Local Climate ◽  
Capital Costs ◽  
The Impact

Performance uncertainty is a barrier to implementation of innovative technologies. This research investigates the potential of flexible design — one that enables future change — to improve the economic performance of a naturally ventilated building. The flexible design of the naturally ventilated building enables future installation of a mechanical cooling system by including features such as space for pipes and chillers. The benefits of the flexible design are energy savings, delay of capital costs and capability of mitigating the risk of a failed building (by installing the mechanical cooling system). To evaluate the flexible design, building energy simulation is conducted over a multi-year time period with stochastic outdoor temperature variables. One result is a probability distribution of the time when the maximum allowable indoor temperature under natural ventilation is exceeded, which may be “never.” Probability distributions are also obtained for energy savings and cost savings as compared to a mechanically cooled building. Together, these results allow decision-makers to evaluate the long-term performance risks and opportunities afforded by a flexible implementation strategy for natural ventilation. It is shown that the likelihood of future installation of mechanical cooling is most sensitive to design parameters. The impact of increased climate variability depends on the local climate. The probability of installing the mechanical system also depends on the comfort criteria. The results show that capital costs for cooling equipment are much greater than the present value of 10 years of cooling energy costs. This result motivates consideration of flexible design as opposed to hybrid cooling designs (which have immediate installation of mechanical cooling). Future work will study the impact of uncertain energy prices on investment attractiveness of naturally ventilated buildings. Other applications of the framework presented herein include replacing the building energy model with a model of another climate-dependent system, such as solar photovoltaic arrays.

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