Transient Analysis for Contained-Cold-Aisle Data Center

2012 ◽  
Author(s):  
Sami A. Alkharabsheh ◽  
Mahmoud Ibrahim ◽  
Saurabh Shrivastava ◽  
Roger Schmidt ◽  
Bahgat Sammakia
Keyword(s):  
Steady State ◽  
Temperature Distribution ◽  
Data Center ◽  
Transient Analysis ◽  
Operating Conditions ◽  
Cfd Modeling ◽  
Base Case ◽  
Air Temperatures ◽  
Air Supply ◽  
Final Steady State

The objective of this paper is to conduct a transient analysis for a contained-cold-aisle data center using Computational Fluid Dynamics (CFD) modeling. Containing the cold aisle reduces the inherent challenges of predictability and energy consumption of data center cooling systems by separating the hot and cold air streams. Transient analysis is crucial to further show the benefits of this methodology and investigate the potential drawbacks. In this work, we investigate the effect of variable power and flow rate in time on a raised-floor data center with specific geometry. First, a base case numerical model is established. Then, we conduct a transient analysis for the uncontained base case and the three containment configurations. The containment configurations under consideration are ceiling-only, doors-only, and fully-contained cold aisle. We hold a comparison between different geometrical configurations of the containment system under certain transient operating conditions. Computer Room Air Conditioning (CRAC) failure and change in IT-demand are chosen to represent conventional transient scenarios in a data center. The transient analysis shows overshoots of cabinet inlet air temperatures beyond the final steady state, which cannot predicted through a simple steady state analysis. In addition, the uniform temperature distribution inside the cold aisle is affected by the change in air supply and level of containment. The temperature distribution in the cold aisle changes with time. Guidelines can be recommended based on the conclusion of this study.

Transient Thermoelastohydrodynamic Study of Tilting-Pad Journal Bearings Under Dynamic Loading

1998 ◽  
Vol 120 (2) ◽  
pp. 405-409 ◽  
Author(s):  
P. Monmousseau ◽  
M. Fillon ◽  
J. Freˆne
Keyword(s):  
Steady State ◽  
Dynamic Loading ◽  
Dynamic Load ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Maximum Temperature ◽  
Tilting Pad ◽  
Transient Period ◽  
Final Steady State ◽  
Tilting Pad Journal Bearings

Nowadays, tilting-pad journal bearings are submitted to more and more severe operating conditions. The aim of this work is to study the thermal and mechanical behavior of the bearing during the transient period from an initial steady state to a final steady state (periodic). In order to study the behavior of this kind of bearing under dynamic loading (Fdyn) due to a blade loss, a nonlinear analysis, including local thermal effects, realistic boundary conditions, and bearing solid deformations (TEHD analysis) is realized. After a comparison between theoretical results obtained with four models (ISO, ADI, THD, and TEHD) and experimental data under steady-state operating conditions (static load Ws), the evolution of the main characteristics for three different cases of the dynamic load (Fdyn/Ws < 1, Fdyn/Ws = 1 and Fdyn//Ws > 1) is discussed. The influence of the transient period on the minimum film thickness, the maximum pressure, the maximum temperature, and the shaft orbit is presented. The final steady state is obtained a long time after the appearance of a dynamic load.

The Whole-Engine Model for Clearance Evaluation

2009 ◽  
Author(s):  
Alexander N. Arkhipov ◽  
Vladimir V. Karaban ◽  
Igor V. Putchkov ◽  
Guenter Filkorn ◽  
Andreas Kieninger
Keyword(s):  
Steady State ◽  
Transient Analysis ◽  
Operating Experience ◽  
Operating Conditions ◽  
Design Stage ◽  
Fe Model ◽  
Engine Operation ◽  
Engine Model ◽  
Operation Conditions ◽  
3D Effects

The evaluation of the blading clearance at the design stage is important for heavy duty gas turbine efficiency. The minimum clearance value at base load is limited by the pinch point clearance during startup and/or shutdown. Therefore, transient analysis is necessary for different operating conditions. 3D transient analysis of a whole engine is labor-intensive; however 2D axisymmetric analysis does not allow consideration of different 3D effects (e.g. twisting, bending, ovality, rotor alignment). In order to overcome these cost and time limitations, the combination of 2D, axisymmetric, whole-engine model results and the scaled deflections caused by different 3D effects is used for the axial and radial clearance engineering assessment during engine operation. The basic rotor and stator closures are taken from the transient analysis using a 2D finite element (FE) model composed of axisymmetric solid and plane stress elements. To take into account 3D effects of airfoil twisting and bending, the 3D FE displacements of the blade are included in the clearance evaluation process. The relative displacements of airfoil tip and reference point at the blade or vane hub are taken from 3D steady-state FE analyses. Then the steady-state displacements of the airfoils are scaled for transient conditions using the proposed technique. Different 3D rotor / stator effects (cold-build clearances and their tolerances, rotor position with respect to stator after assembly, casing bending, deformations of compressor and turbine vane carrier inducing of casing ovalization, exhaust gas housing movements, movements of the rotor in bearings and CVC and TVC support, etc.) are also included as a contributor to the clearances. The results of the calculations are analyzed and compared with good agreements to the clearances measured in engine testing under real operation conditions. The proposed methodology allows assessing the operating clearances between the stator and rotor during the design phase. Optimization of the running clearance is one key measure to upgrade and improve the engine performance during operating experience.

Stack-Up Forces for Normal and Abnormal Operating Conditions in a Railroad Roller Bearing Assembly

1998 ◽  
Vol 120 (4) ◽  
pp. 707-713
Author(s):  
H. Wang ◽  
T. F. Conry ◽  
C. Cusano
Keyword(s):  
Steady State ◽  
Temperature Distribution ◽  
Operating Temperature ◽  
Roller Bearing ◽  
Operating Conditions ◽  
Transient Temperature ◽  
Surface Geometry ◽  
Tapered Roller Bearing ◽  
Transient Temperature Distribution ◽  
Abnormal Operating Conditions

Stack-up force distributions are obtained for normal and abnormal operating conditions in a class F (6 1/2 × 12) railroad tapered roller bearing-axle assembly for various friction coefficients, press-fits and cap screw preloads. Three conditions that affect the stack-up force distribution are considered: a steady-state normal-operating temperature distribution, a steady-state temperature distribution resulting from a stuck brake or a jammed outboard roller, and a transient temperature distribution due to multiple jammed outboard rollers. The steady-state normal or abnormal operating temperature have insignificant effects for nominal values of interference, friction and cap screw preload. However, the effect of the transient temperature due to multiple jammed outboard rollers on the stack-up system is detrimental due to localized high temperature gradients near the outboard cone area and a distortion of the original surface geometry of the cone.

Design Analysis and Performance Evaluation of a Data Center With Indirect Evaporative Cooling

2017 ◽  
Author(s):  
Fatemeh Tavakkoli ◽  
Siavash Ebrahimi ◽  
Xiaogang Sun ◽  
Yan Cui ◽  
Ali Heydari
Keyword(s):  
Data Center ◽  
Evaporative Cooling ◽  
Water System ◽  
Operating Conditions ◽  
Air Cooling ◽  
Capital Costs ◽  
Air Supply ◽  
Chilled Water ◽  
Indirect Evaporative Cooling ◽  
Chilled Water System

With the rapid growth of data centers worldwide and the global shift towards energy sustainability, deploying new cooling technologies has an utmost importance. Conventional cooling systems such as chilled water system, usually have high capital costs and relatively low energy efficiency, leading to a high PUE and TCO values. Indirect evaporative cooling is a promising technology, which offers air cooling with high efficiency, hygiene air quality, and lower total cost. This paper details the design of a proof-of-concept data center with indirect evaporative cooling, which will be eventually deployed at megawatt-scale Baidu datacenters. BIN data analysis and CFD simulation are performed to optimize the physical design and operating conditions. CFD analysis of the data center room is established to optimize rack placement, air flow management, and cold aisle hot aisle configuration. A comprehensive TCO analysis is established, which shows a total savings of 9% using IDEC technology compared to chilled water system for cooling. In addition, TCO analysis indicates small to negligible effect of air supply temperature. Hence, air supply to the cold aisle is set to 27 °C to improve cooling performance. Finally, ROI sensitivity analysis is performed to measure the sensitivity of ROI on power usage effectiveness of the IDEC unit.

scholarly journals Steady-state and transient heat transfer through fins of complex geometry

2014 ◽  
Vol 35 (2) ◽  
pp. 117-133 ◽  
Author(s):  
Dawid Taler ◽  
Jan Taler
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Temperature Distribution ◽  
Transient Analysis ◽  
Complex Geometry ◽  
Transient Temperature ◽  
Heat Flow Rate ◽  
Approximate Methods ◽  
Fin Efficiency ◽  
Transient Temperature Distribution

Abstract Various methods for steady-state and transient analysis of temperature distribution and efficiency of continuous-plate fins are presented. For a constant heat transfer coefficient over the fin surface, the plate fin can be divided into imaginary rectangular or hexangular fins. At first approximate methods for determining the steady-state fin efficiency like the method of equivalent circular fin and the sector method are discussed. When the fin geometry is complex, thus transient temperature distribution and fin efficiency can be determined using numerical methods. A numerical method for transient analysis of fins with complex geometry is developed. Transient temperature distributions in continuous fins attached to oval tubes is computed using the finite volume - finite element methods. The developed method can be used in the transient analysis of compact heat exchangers to calculate correctly the heat flow rate transferred from the finned tubes to the fluid.

Transient Thermoelastohydrodynamic Study of Tilting-Pad Journal Bearings Under Dynamic Loading

1997 ◽  
Author(s):  
Pascal Monmousseau ◽  
Michel Fillon ◽  
Jean Frêne
Keyword(s):  
Steady State ◽  
Dynamic Loading ◽  
Dynamic Load ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Maximum Temperature ◽  
Tilting Pad ◽  
Transient Period ◽  
Final Steady State ◽  
Tilting Pad Journal Bearings

Nowadays, the tilting-pad journal bearings are submitted to more and more severe operating conditions. The aim of this work is to study the thermal and mechanical behavior of the bearing during the transient period from an initial steady-state to a final steady-state (periodic). In order to study the behavior of this kind of bearing under dynamic loading (Fdyn) due to a blade loss, a nonlinear analysis, including local thermal effects, realistic boundary conditions and bearing solid deformations (TEHD analysis) is realized. After a comparison between theoretical results obtained with four models (ISO, ADI, THD and TEHD) and experimental data under steady-state operating conditions (static load Ws), the evolution of the main characteristics for three different cases of the dynamic load (Fdyn/Ws<1, Fdyn/Ws=1 and Fdyn/Ws>1) is discussed. The influence of the transient period on the minimum film thickness, the maximum pressure, the maximum temperature and the shaft orbit is presented. The final steady-state is obtained a long time after the appearance of a dynamic load.

Predictive Model Development and Validation for Raised Floor Plenum Data Center

2020 ◽  
Vol 142 (2) ◽  
Author(s):  
Yogesh Fulpagare ◽  
Atul Bhargav ◽  
Yogendra Joshi
Keyword(s):  
Data Center ◽  
Data Centers ◽  
Model Development ◽  
Operating Conditions ◽  
System Level ◽  
Predictive Tool ◽  
Air Temperatures ◽  
Computational Fluid Dynamics Cfd ◽  
The Cost ◽  
Development And Validation

Abstract With the explosion in digital traffic, the number of data centers as well as demands on each data center, continue to increase. Concomitantly, the cost (and environmental impact) of energy expended in the thermal management of these data centers is of concern to operators in particular, and society in general. In the absence of physics-based control algorithms, computer room air conditioning (CRAC) units are typically operated through conservatively predetermined set points, resulting in suboptimal energy consumption. For a more optimal control algorithm, predictive capabilities are needed. In this paper, we develop a data-informed, experimentally validated and computationally inexpensive system level predictive tool that can forecast data center behavior for a broad range of operating conditions. We have tested this model on experiments as well as on (experimentally) validated transient computational fluid dynamics (CFD) simulations for two different data center design configurations. The validated model can accurately forecast temperatures and air flows in a data center (including the rack air temperatures) for 10–15 min into the future. Once integrated with control aspects, we expect that this model can form an important building block in a future intelligent, increasingly automated data center environment management systems.

scholarly journals Influence of Bypass on Thermo-Hydraulics of VVER 440 Fuel Assembly

2017 ◽  
Vol 67 (1) ◽  
pp. 69-76
Author(s):  
Jakub Jakubec ◽  
Juraj Paulech ◽  
Vladimír Kutiš ◽  
Gabriel Gálik
Keyword(s):  
Steady State ◽  
Temperature Distribution ◽  
Pressure Drop ◽  
Fuel Assembly ◽  
Nuclear Reactor ◽  
Software Tool ◽  
Operating Conditions ◽  
Coolant Flow ◽  
Cfd Modelling ◽  
Ansys Cfx

AbstractThe paper deals with CFD modelling and simulation of coolant flow within the nuclear reactor VVER 440 fuel assembly. The influence of coolant flow in bypass on the temperature distribution at the outlet of the fuel assembly and pressure drop was investigated. Only steady-state analyses were performed. Boundary conditions are based on operating conditions. ANSYS CFX is chosen as the main CFD software tool, where all analyses are performed.

Airflow Management on the Efficiency Index of a Container Data Center Having Overhead Air Supply

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Cheng-Hao Wang ◽  
Yeng-Yung Tsui ◽  
Chi-Chuan Wang
Keyword(s):  
Temperature Distribution ◽  
Flow Rate ◽  
Data Center ◽  
Hot Spot ◽  
Efficiency Index ◽  
Test Results ◽  
Air Flow Rate ◽  
Hot Air ◽  
Air Supply ◽  
Small Container

Effect of airflow managements on the efficiency index of a small container data center having overhead air supply is reported in this study. Seventeen arrangements and configurations regarding the airflow and blockage arrangements are experimentally examined and compared. Test results indicate an appreciable hot air recirculation occurring for rack arrangement without any blockage, and the hot spot occurs at the second rack alongside the cold aisle. The hot spot had moved to the first rack when the blockage plate is installed on the rack top. Rack locations relative to air handler casts a negligible effect on the efficiency index, and it is comparatively more effective by sealing the trailing of the cold aisle. A smaller cold-aisle spacing helps to lower the temperature distribution, and an additional opening of the supplied vent will not help in removal of hot spot. Shutting off the grille in the center of cold aisle is also unable to fix the hot air recirculation and may even incur hot air reversal. The hot air reversal can be removed by adding additional blockage plate at the flow reversal section. Higher supplied air flow rate also improves the efficiency index considerably.

Data Center Housing the World’s 3rd Fastest Supercomputer: Above Floor Thermal Measurements Compared to CFD Analysis

2007 ◽  
Author(s):  
Roger Schmidt ◽  
Madhusudan Iyengar ◽  
Joe Caricari
Keyword(s):  
Data Center ◽  
High Performance ◽  
Data Centers ◽  
Floor Tile ◽  
Heat Fluxes ◽  
Electronic Equipment ◽  
Cfd Modeling ◽  
Peak Performance ◽  
Cfd Analysis ◽  
Air Temperatures

With the ever increasing heat dissipated by IT equipment housed in data centers it is becoming more important to project the changes that can occur in the data center as the newer higher powered hardware is installed. The computational fluid dynamics (CFD) software that is available has improved over the years and some CFD software specific to data center thermal analysis has been developed. This has improved the timeliness of providing some quick analysis of the effects of new hardware into the data center. But it is critically important that this software provide a good report to the user of the effects of adding this new hardware. And it is the purpose of this paper to examine a large cluster installation and compare the CFD analysis with environmental measurements obtained from the same site. This paper shows measurements and CFD analysis of high powered racks as high as 27 kW clustered such that heat fluxes in some regions of the data center exceeded 700 Watts/ft2 (7535 W/m2). This paper describes the thermal profile of a high performance computing cluster located in an IBM data center and a comparison of that cluster modeled with CFD software. The high performance Advanced Simulation and Computing (ASC) cluster, developed and manufactured by IBM, is code named ASC Purple. It is the World’s 3rd fastest supercomputer [1], operating at a peak performance of 77.8 TFlop/s. ASC Purple, which employs IBM pSeries p575, Model 9118, contains more than 12,000 processors, 50 terabytes of memory, and 2 petabytes of globally accessible disk space. The cluster was first tested in the IBM development lab in Poughkeepsie, NY and then shipped to Lawrence Livermore National Labs in Livermore, California where it was installed to support our national security mission. Detailed measurements were taken in both data centers of electronic equipment power usage, perforated floor tile airflow, cable cutout airflow, computer room air conditioning (CRAC) airflow, and electronic equipment inlet air temperatures and were report in Schmidt [2], but only the IBM Poughkeepsie results will be reported here along with a comparison to CFD modeling results. In some areas of the Poughkeepsie data center there were regions that did exceed the equipment inlet air temperature specifications by a significant amount. These areas will be highlighted and reasons given on why these areas failed to meet the criteria. The modeling results by region showed trends that compared somewhat favorably but some rack thermal profiles deviated quite significantly from measurements.

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