Experimentally Validated Computational Fluid Dynamics Model for Data Center With Active Tiles

2017 ◽  
Author(s):  
Jayati D. Athavale ◽  
Yogendra Joshi ◽  
Minami Yoda
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Data Center ◽  
Hot Spots ◽  
Cfd Model ◽  
Floor Tiles ◽  
Computational Fluid Dynamics Cfd ◽  
Plenum Pressure

This paper presents an experimentally validated room-level computational fluid dynamics (CFD) model for raised-floor data center configurations employing active tiles. Active tiles are perforated floor tiles with integrated fans, which increase the local volume flowrate by redistributing the cold air supplied by the computer room air conditioning (CRAC) unit to the under-floor plenum. In a previous study [1], experiments were conducted to explore the potential of active tiles for economically and efficiently eliminating hot spots in data center. Our results indicated that active tiles, as the actuators closest to the racks, can significantly and quickly impact the local distribution of cooling resources. They could therefore be used in an appropriate control framework to rapidly mitigate hot spots, and maintain local conditions in an energy-efficient manner. The numerical model of the data center room operates in an under-floor supply and ceiling return cooling configuration and consists of one cold aisle with 12 racks arranged on both sides and three CRAC units sited around the periphery of the room. The commercial computational fluid dynamics (CFD) software package Future Facilities 6SigmaDCX [2], which is specifically designed for data center simulation, is used to develop the model. First, a baseline model using only passive tiles was developed and experimental data were used to verify and calibrate plenum leakage for the room. Then a CFD model incorporating active tiles was developed for two configurations: (a) a single active tile and 9 passive tiles in the cold aisle; and (b) an aisle populated with 10 (i.e., all) active tiles. The active tiles are modeled as a combination of a grill, fan elements and flow blockages to closely mimic the actual active tile used in the experimental studies. The fan curve for the active tile fans is included in the model to account for changes in flow rate through the tiles in response to changes in plenum pressure. The model with active tiles is validated by comparing the flow rate through the floor tiles, relative plenum pressure and rack inlet temperatures for selected racks with the experimental measurements. The predictions from the CFD model are found to be in good agreement with the experimental data, with an average discrepancy between the measured and computed values for total flow rate and rack inlet temperature less than 4% and 1.7 °C, respectively. These validated models were then used to simulate steady state and transient scenarios following cooling failure. This physics-based and experimentally validated room-level model can be used to predict temperature and flow distributions in a data center using active tiles. These predictions can then be used to identify the optimal number and locations of active tiles to mitigate hot spots, without adversely affecting other parts of the data center.

Experimentally Validated Computational Fluid Dynamics Model for Data Center With Active Tiles

2018 ◽  
Vol 140 (1) ◽  
Author(s):  
Jayati Athavale ◽  
Yogendra Joshi ◽  
Minami Yoda
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Data Center ◽  
Hot Spot ◽  
Volume Flow Rate ◽  
Optimal Number ◽  
Inlet Temperature ◽  
Cfd Model ◽  
Level Model

Abstract This paper presents an experimentally validated room-level computational fluid dynamics (CFD) model for raised-floor data center configurations employing active tiles. Active tiles are perforated floor tiles with integrated fans, which increase the local volume flow rate by redistributing the cold air supplied by the computer room air conditioning (CRAC) unit to the under-floor plenum. The numerical model of the data center room consists of one cold aisle with 12 racks arranged on both sides and three CRAC units sited around the periphery of the room. The commercial CFD software package futurefacilities6sigmadcx is used to develop the model for three configurations: (a) an aisle populated with ten (i.e., all) passive tiles; (b) a single active tile and nine passive tiles in the cold aisle; and (c) an aisle populated with all active tiles. The predictions from the CFD model are found to be in good agreement with the experimental data, with an average discrepancy between the measured and computed values for total flow rate and rack inlet temperature less than 4% and 1.7 °C, respectively. The validated models were then used to simulate steady-state and transient scenarios following cooling failure. This physics-based and experimentally validated room-level model can be used for temperature and flow distributions prediction and identifying optimal number and locations of active tiles for hot spot mitigation in data centers.

Experimentally Validated Computational Fluid Dynamics Model for a Data Center With Cold Aisle Containment

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Sami A. Alkharabsheh ◽  
Bahgat G. Sammakia ◽  
Saurabh K. Shrivastava
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Data Center ◽  
Flow Distribution ◽  
Temperature Measurements ◽  
Experimental Measurements ◽  
Air Conditioner ◽  
Cfd Model ◽  
Good Agreement

This paper presents the results of an experimentally validated computational fluid dynamics (CFD) model for a data center with fully implemented fan curves on both the servers and the computer room air conditioner (CRAC). Both open and contained cold aisle systems are considered in this study. This work is divided into sections for the baseline system (prior to installing containment) calibration and the fully contained cold aisle system calibration and leakage characterization. In the open system, the fan curve of the CRAC unit is extracted from the manufacturer data, while the fan curve of the load banks is obtained through experimental measurements. The experimental results are found to be in good agreement with the average model predictions. In the fully contained cold aisle system, a detailed containment CFD model is developed based on experimental measurements. The model is validated by comparing the flow rate through the perforated floor tiles and the rack inlet temperatures with the experimental measurements. The CFD results are found to be in good agreement with the experimental data with an average relative error between the measured and computed flow rate of approximately 6.7%. Temperature measurements are used to calibrate the sources of leakage in the containment and rack mounting rails. The temperature measurements and the CFD results agree well with an average difference of less than 1 °C. This study provides important modeling guidelines for data centers. In order to predict the performance of contained cold aisle systems flow distribution, it is crucial that physics based models of fan curves, server internal resistances, detailed rack models, and other design details are all accurate and experimentally verified.

Bubble Breakup and Coalescence Modelling for Subsea Gas Releases Using Computational Fluid Dynamics

2018 ◽  
Author(s):  
Kejia Wu ◽  
Johnathan Green ◽  
Subajan Sivandran
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Gas Release ◽  
Cfd Model ◽  
The Core ◽  
Bubble Breakup ◽  
Characteristic Behaviour ◽  
Computational Fluid Dynamics Cfd

Bubble breakup and coalescence is a phenomenon which occurs within a developing subsea gas plume. A Computational Fluid Dynamics (CFD) model incorporating bubble breakup and coalescence was developed to describe the behaviour of a subsea gas release and the subsequent rising gas plume. The model was assessed for its suitability in capturing the characteristic behaviour of a rising gas plume by comparing the CFD results with experimental data obtained from underwater gas release experiments. The study shows bubble breakup and coalescence plays a key role in determining the shape and the behaviour of a subsea gas release. Without the bubble breakup and coalescence included in the CFD model a narrower plume width and higher rising velocity is observed when compared to the experimental data. With bubble breakup and coalescence included the results obtained from the CFD model more accurately match the experimental data. Breakup and coalescence is a mechanism which redistributes the energy within the core of the gas plume towards the edge of the plume. This has a significant impact on the plume characteristics and is vital to be included in the CFD model to describe the behaviour of the released gas. The study was carried out using air as the released gas. This was done to compare with the available experimental data where air was used as the source. However the CFD model developed is applicable for hydrocarbon subsea gas releases.

scholarly journals Effect of Bench Hood Exhaust Usage on Indoor Air Quality in a Chemical Laboratory

2014 ◽  
Vol 1 ◽  
pp. 14-22
Author(s):  
Ayman A. Shaaban ◽  
Samy M. Morcos ◽  
Essam Eldin Khalil ◽  
Mahmoud A. Fouad
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Air Quality ◽  
Indoor Air Quality ◽  
Mole Fraction ◽  
Indoor Air ◽  
Cfd Model ◽  
Ansys Fluent ◽  
Computational Fluid Dynamics Cfd

Indoor air quality inside chemical laboratories subjected to gaseous contaminants was investigated numerically throughout the current research using Ansys Fluent 13. The lab is 4.8 m (L) * 4.3 m (W) * 2.73 m (H). The model was built and mesh was generated using Gambit 2.2.30 yielding around 1.4 million cells. To ensure the reliability of the Computational Fluid Dynamics (CFD) model validation was done against experimental data of three cases done by Jin et al. [1]. The model could simulate accurately contaminant mole fraction to the order of 10 Indoor air quality inside chemical laboratories subjected to gaseous contaminants was investigated numerically throughout the current research using Ansys Fluent 13. The lab is 4.8 m (L) * 4.3 m (W) * 2.73 m (H). The model was built and mesh was generated using Gambit 2.2.30 yielding around 1.4 million cells. To ensure the reliability of the Computational Fluid Dynamics (CFD) model validation was done against experimental data of three cases done by Jin et al. [1]. The model could simulate accurately contaminant mole fraction to the order of 10.

Effects of Over Fire Air on the Combustion and NOx Emission Characteristics of a 600 MW Opposed Swirling Fired Boiler

2012 ◽  
Vol 512-515 ◽  
pp. 2135-2142 ◽  
Author(s):  
Yu Peng Wu ◽  
Zhi Yong Wen ◽  
Yue Liang Shen ◽  
Qing Yan Fang ◽  
Cheng Zhang ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Empirical Method ◽  
Nox Emission ◽  
Emission Characteristics ◽  
Cfd Model ◽  
Nitrogen Release ◽  
Computational Fluid Dynamics Cfd ◽  
Low Nox Emission

A computational fluid dynamics (CFD) model of a 600 MW opposed swirling coal-fired utility boiler has been established. The chemical percolation devolatilization (CPD) model, instead of an empirical method, has been adapted to predict the nitrogen release during the devolatilization. The current CFD model has been validated by comparing the simulated results with the experimental data obtained from the boiler for case study. The validated CFD model is then applied to study the effects of ratio of over fire air (OFA) on the combustion and nitrogen oxides (NOx) emission characteristics. It is found that, with increasing the ratio of OFA, the carbon content in fly ash increases linearly, and the NOx emission reduces largely. The OFA ratio of 30% is optimal for both high burnout of pulverized coal and low NOx emission. The present study provides helpful information for understanding and optimizing the combustion of the studied boiler

Validation of a Computationally Efficient Computational Fluid Dynamics (CFD) Model for Industrial Bubble Column Bioreactors

2014 ◽  
Vol 53 (37) ◽  
pp. 14526-14543 ◽  
Author(s):  
Dale D. McClure ◽  
Hannah Norris ◽  
John M. Kavanagh ◽  
David F. Fletcher ◽  
Geoffrey W. Barton
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Bubble Column ◽  
Cfd Model ◽  
Computationally Efficient ◽  
Computational Fluid Dynamics Cfd

scholarly journals Journal Bearing: An Integrated CFD-Analytical Approach for the Estimation of the Trajectory and Equilibrium Position

2020 ◽  
Vol 10 (23) ◽  
pp. 8573
Author(s):  
Franco Concli
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pressure Distribution ◽  
Equilibrium Position ◽  
Analytical Approach ◽  
Journal Bearing ◽  
Cfd Model ◽  
Cavitation Model ◽  
Computational Fluid Dynamics Cfd ◽  
The Mathematical Model

For decades, journal bearings have been designed based on the half-Sommerfeld equations. The semi-analytical solution of the conservation equations for mass and momentum leads to the pressure distribution along the journal. However, this approach admits negative values for the pressure, phenomenon without experimental evidence. To overcome this, negative values of the pressure are artificially substituted with the vaporization pressure. This hypothesis leads to reasonable results, even if for a deeper understanding of the physics behind the lubrication and the supporting effects, cavitation should be considered and included in the mathematical model. In a previous paper, the author has already shown the capability of computational fluid dynamics to accurately reproduce the experimental evidences including the Kunz cavitation model in the calculations. The computational fluid dynamics (CFD) results were compared in terms of pressure distribution with experimental data coming from different configurations. The CFD model was coupled with an analytical approach in order to calculate the equilibrium position and the trajectory of the journal. Specifically, the approach was used to study a bearing that was designed to operate within tight tolerances and speeds up to almost 30,000 rpm for operation in a gearbox.

An Improved Computational Fluid Dynamics (CFD) Model for Erosion Prediction in Oil and Gas Industry Applications

2014 ◽  
Author(s):  
Deval Pandya ◽  
Brian Dennis ◽  
Ronnie Russell
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Surface Velocity ◽  
Particle Model ◽  
Model Parameters ◽  
Cfd Model ◽  
Erosion Model ◽  
Erosion Prediction ◽  
Erosion Models ◽  
Computational Fluid Dynamics Cfd

In recent years, the study of flow-induced erosion phenomena has gained interest as erosion has a direct influence on the life, reliability and safety of equipment. Particularly significant erosion can occur inside the drilling tool components caused by the low particle loading (<10%) in the drilling fluid. Due to the difficulty and cost of conducting experiments, significant efforts have been invested in numerical predictive tools to understand and mitigate erosion within drilling tools. Computational fluid dynamics (CFD) is becoming a powerful tool to predict complex flow-erosion and a cost-effective method to re-design drilling equipment for mitigating erosion. Existing CFD-based erosion models predict erosion regions fairly accurately, but these models have poor reliability when it comes to quantitative predictions. In many cases, the error can be greater than an order of magnitude. The present study focuses on development of an improved CFD-erosion model for predicting the qualitative as well as the quantitative aspects of erosion. A finite-volume based CFD-erosion model was developed using a commercially available CFD code. The CFD model involves fluid flow and turbulence modeling, particle tracking, and application of existing empirical erosion models. All parameters like surface velocity, particle concentration, particle volume fraction, etc., used in empirical erosion equations are obtained through CFD analysis. CFD modeling parameters like numerical schemes, turbulence models, near-wall treatments, grid strategy and discrete particle model parameters were investigated in detail to develop guidelines for erosion prediction. As part of this effort, the effect of computed results showed good qualitative and quantitative agreement for the benchmark case of flow through an elbow at different flow rates and particle sizes. This paper proposes a new/modified erosion model. The combination of an improved CFD methodology and a new erosion model provides a novel computational approach that accurately predicts the location and magnitude of erosion. Reliable predictive methodology can help improve designs of downhole equipment to mitigate erosion risk as well as provide guidance on repair and maintenance intervals. This will eventually lead to improvement in the reliability and safety of downhole tool operation.

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