From Chip to Cooling Tower Data Center Modeling: Influence of Server Inlet Temperature and Temperature Rise Across Cabinet

2011 ◽  
Vol 133 (1) ◽  
Author(s):  
Thomas J. Breen ◽  
Ed J. Walsh ◽  
Jeff Punch ◽  
Amip J. Shah ◽  
Cullen E. Bash
Keyword(s):  
Heat Flow ◽  
Temperature Rise ◽  
Data Center ◽  
Cooling Tower ◽  
Thermal Design ◽  
Inlet Temperature ◽  
Efficient System ◽  
Current Strategy ◽  
Data Center Cooling ◽  
The Impact

To achieve reductions in the power consumption of the data center cooling infrastructure, the current strategy in data center design is to increase the inlet temperature to the rack, while the current strategy for energy-efficient system thermal design is to allow increased temperature rise across the rack. Either strategy, or a combination of both, intuitively provides enhancements in the coefficient of performance of the data center in terms of computing energy usage relative to cooling energy consumption. However, this strategy is currently more of an empirically based approach from practical experience, rather than a result of a good understanding of how the impact of varying temperatures and flow rates at rack level influences each component in the chain from the chip level to the cooling tower. The aim of this paper is to provide a model to represent the physics of this strategy by developing a modeling tool that represents the heat flow from the rack level to the cooling tower for an air cooled data center with chillers. This model presents the performance of a complete data center cooling system infrastructure. After detailing the model, two parametric studies are presented that illustrate the influence of increasing rack inlet air temperature, and temperature rise across the rack, on different components in the data center cooling architecture. By considering the total data center, and each component’s influence on the greater infrastructure, it is possible to identify the components that contribute most to the resulting inefficiencies in the heat flow from chip to cooling tower and thereby identify the components in need of possible redesign. For the data center model considered here it is shown that the strategy of increasing temperature rise across the rack may be a better strategy than increasing inlet temperature to the rack.

Evaluation of a Data Center Recirculation Non-Uniformity Metric Using Computational Fluid Dynamics

2011 ◽  
Author(s):  
Dustin W. Demetriou ◽  
H. Ezzat Khalifa
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Simple Model ◽  
Temperature Rise ◽  
Data Center ◽  
Large Temperature ◽  
Inlet Temperature ◽  
Temperature Pattern ◽  
Cfd Analysis ◽  
Tile Flow

The work presented in this paper is an extension of the companion work by the authors on a simplified thermodynamic model for data center optimization, in which a recirculation non-uniformity metric, θ, was introduced and used in a parametric analysis to highlight the deleterious effect of recirculation non-uniformity at the inlet of racks on the data center cooling infrastructure power consumption. In this work, several studies are done using a commercial computational fluid dynamics (CFD) package to verify many of the assumptions necessary in the development of the simplified model and to understand the degree of recirculation non-uniformity present in typical data center configurations. A number of CFD simulations are used to quantify the ability of the simple model at predicting θ. The results show that the simple model provides a fairly accurate estimate of θ, with a standard deviation in the prediction error of ∼10–15%. The CFD analysis are also to understand the effect of row length and server temperature rise (ΔTs) temperature non-uniformity. The simulations show that reasonable values of θ range from 2–6 for open aisle data centers depending on operating strategy and data center layout. As a means to understand the effect of buoyancy, a data center Archimedes number (Ar), the ratio of buoyancy to inertia forces, is introduced as a function of tile flow rate and server temperature rise. For servers with modest temperature rise (∼ 10.0°C), Ar is ∼0.1; however, for racks with large temperature rise (∼20°C), Ar > 1.0, meaning buoyancy needs to be considered important. Through CFD analysis the significant effect buoyancy has on the inlet rack temperature patterns is highlighted. The Capture Index (ψ), the ratio of cold air ingested by the racks to the required rack flow, is used to investigate its relationship to the ratio of server flow to tile flow (Y), as the inlet rack temperature patterns are changed by increased Ar. The results show that although the rack inlet temperature patterns are extremely different, ψ does not change significantly as a function of Ar. Lastly, the effect of buoyancy on the assumption of linearity of the temperature field is considered for a range of Ar. The results show the emergence of a stratified temperature pattern at the inlet of the racks as Ar increases and buoyancy becomes more important. It is concluded that under these conditions, a δT change in tile temperature does not produce a δT change in temperature everywhere in the field.

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.

Numerical Study for Data Center Cooling Using Active Tiles

2015 ◽  
Author(s):  
Zhihang Song
Keyword(s):  
Data Center ◽  
Data Centers ◽  
Numerical Study ◽  
Thermal Design ◽  
Load Demand ◽  
Design Variables ◽  
Data Center Cooling ◽  
Floor Tiles ◽  
Flow Features ◽  
Computational Fluid Dynamics Cfd

The design of raised floor, hot/cold aisle data centers has become a widely used approach for data center cooling. However, more advanced cooling solution is still needed to achieve better managed airflow distributions and improved energy efficiency. The use of fan assisted floor tiles (i.e., active tiles) is being investigated as an evolution of Data Center cooling solutions to accommodate higher heat load demand. In this study, compact models of fan assisted tiles was imported into a basic hot aisle/cold aisle data center configuration built and analyzed using the computational fluid dynamics (CFD) technique. The significant thermal design aspects under numerical investigation include: fan curve, swirl settings, and under-floor pressure (with and without aisle containment). The flow features affected by the critical design variables are consequently compared and discussed. It might be concluded that appropriately designed fan assisted floor tiles might meet a promise of optimizing the cooling arrangement in data centers.

A Rack-Level Cooling Redundancy Metric for Data Center Applications

2011 ◽  
Author(s):  
James W. VanGilder ◽  
Christopher M. Healey
Keyword(s):  
Power Systems ◽  
Data Center ◽  
Inlet Temperature ◽  
Cooling Systems ◽  
Cooling Performance ◽  
System Failures ◽  
Important Measure ◽  
Data Center Cooling ◽  
General Data ◽  
Local Nature

Redundancy is an important measure of an operation’s ability to withstand planned or unplanned system failures. While this concept is commonly used in power systems, redundancy can be extended to data center cooling systems, as well. We propose a rack-based redundancy metric for cooling performance that is similar in nomenclature to metrics for power systems, but also captures the local nature of data center cooling. This paper will explain how to compute this metric for general data center layouts and show how cooling redundancy can influence design choices when used in combination with typical measures of cooling coverage: inlet temperature and Capture Index.

Data Center Trends Toward Higher Ambient Inlet Temperatures and the Impact on Server Performance

2013 ◽  
Author(s):  
Aparna Vallury ◽  
Jason Matteson
Keyword(s):  
Best Practices ◽  
Data Center ◽  
Design Guidelines ◽  
Thermal Design ◽  
Ambient Conditions ◽  
Performance Impact ◽  
Worst Case ◽  
Inlet Conditions ◽  
It Efficiency ◽  
The Impact

With the extension of the 2011 ASHRAE Thermal Design Guidelines to incorporate a broader Class A3 and A4 specification, the server industry is trying to adapt to the changing landscape of industry best practices and initiatives, and adopt the new ASHRAE Class A3 and A4 environments. In order to accommodate the high ambient inlet conditions while meeting the IT efficiency initiatives in the industry, certain design considerations must occur and it becomes very important to understand the implication of adhering to Class A3 and A4 environments on the performance of the servers. This paper describes a study that was conducted to understand the impact on performance of different servers under various workloads and inlet ambient conditions specifically adhering to class A3 specification only. The results from the study are presented in this paper which shows that no performance impact was observed in a 35°C environment, and bounded by 2% running worst case applications at 40°C and 0% when running lighter loads.

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.

Energy Modeling of Air-Cooled Data Centers: Part II—The Effect of Recirculation on the Energy Optimization of Open-Aisle, Air-Cooled Data Centers

2011 ◽  
Author(s):  
Dustin W. Demetriou ◽  
H. Ezzat Khalifa
Keyword(s):  
Power Consumption ◽  
Temperature Rise ◽  
Data Center ◽  
Data Centers ◽  
Energy Savings ◽  
Optimal Operation ◽  
Effect Of Temperature ◽  
Total Energy Consumption ◽  
Air Supply ◽  
Data Center Cooling

The work presented in this paper describes a simplified thermodynamic model that can be used for exploring optimization possibilities in air-cooled data centers. The model has been used to identify optimal, energy-efficient designs, operating scenarios, and operating parameters such as flow rates and air supply temperature. The model is used to parametrically evaluate the total energy consumption of the data center cooling infrastructure, by considering changes in the server temperature rise. The results of this parametric analysis highlight the important features that need to be considered when optimizing the operation of air-cooled data centers, especially the trade-off between low air supply temperature and increased air flow rate. The analysis is used to elucidate the deleterious effect of temperature non-uniformity at the inlet of the racks on the data center cooling infrastructure power consumption. A recirculation non-uniformity metric, θ, is introduced, which is the ratio of the maximum recirculation of any server to the average recirculation of all servers. The analysis of open-aisle data centers shows that as the recirculation non-uniformity at the inlet of the racks increases, optimal operation tends toward lower recirculation and higher power consumption; stressing the importance of providing as uniform conditions to the racks as possible. Cooling infrastructure energy savings greater than 40% are possible for a data center with uniform recirculation (θ = 0) compared to a data center with a typical recirculation non-uniformity (θ = 4). It is also revealed that servers with a modest temperature rise (∼10°C) have a wider latitude for cooling optimization than those with a high temperature rise (≥20°C).

scholarly journals Effect Of The Water Inlet Temperature And Flow Rate On The Energy And Exergy Performance of A Forced Draft Counter Wet Cooling Tower

2021 ◽  
Author(s):  
Fadhil Abdulrazzaq Kareem ◽  
Doaa Zaid Khalaf ◽  
Mustafa J. Al-Dulaimi ◽  
Yasser Abdul Lateef
Keyword(s):  
Water Temperature ◽  
Water Flow ◽  
Flow Rate ◽  
Thermal Efficiency ◽  
Cooling Tower ◽  
Water Flow Rate ◽  
Second Law Of Thermodynamics ◽  
Inlet Temperature ◽  
Forced Draft ◽  
The Impact

Abstract Cooling towers, wherein water and air are contacted directly with each other, are specialized heat exchangers. These open-topped, tall, cubical or cylindrical shaped are responsible for reducing the temperature of the water that generated from the industrial or HVAC systems. The performance of the forced draft wet cooling tower is investigated experimentally. The performance analysis is based on the first and second law of thermodynamics. The impact of the inlet water temperature and water inlet flow rate is investigated. The inlet water temperature is varied from 28 °C to 42 °C for the water flow rates of (0.03, 0.05 and 0.075 kg/sec). The results reveal that the cooling capacity, cooling range, thermal efficiency and the total exergy destruction increase according to the increase in the inlet water temperature and the water flow rate. The maximum cooling range is found to be 14.8 °C with the maximum thermal efficiency of 74 %. On other hand, the exergy efficiency decreases with the increasing of the inlet water temperature and the water flow rate within a range of 11.9 % to 57.8 %.

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