Role of Airflow Modeling
Data centers are facilities that house computer servers, data storage systems, and telecommunications equipment. To ensure that these computer systems operate reliably, they must be adequately cooled: The airflow requirement of each server rack must be met, in order to maintain the rack inlet air temperatures within acceptable range.
The airflow distribution and rack inlet temperatures are controlled by complex fluid dynamics processes and depend on a large number of parameters, which often interact in a counter-intuitive manner. These parameters include the layouts of perforated tiles, CRAC units, supply and exhaust ducts, supplemental cooling units, and server racks; the open area of perforated tiles; the heat loads and airflow demands of the racks; and, obstructions under and above the raised floor.
Often data center floor layouts are designed using empirical guidelines based on limited measurements. These guidelines do not consider the complex fluid dynamics processes that control the airflow and temperature distribution. Consequently, the layouts do not produce the expected flow rates and rack inlet temperatures, and must be modified. However, because modifications in one region of the floor influence airflow and temperatures throughout the floor, considerable trial and error is involved in identifying adjustments that will yield the desired changes in the rack inlet temperatures. This design practice is time consuming and expensive, and often the resulting arrangement is not optimum. Computational Fluid Dynamics (CFD) modeling or airflow modeling offers a more scientific and comprehensive design approach.
Computational simulation can be used for a quick setup of any proposed layout, any desired placement of CRAC units and perforated tiles, and any imagined failure scenario. The “computational” trial-and-error process is preferable for two reasons. First, performing a simulation is much faster and more economical than building an actual layout. Second, the computed results provide not only the flow rate distribution through perforated tiles and rack inlet temperatures but also the underlying velocity, pressure, and temperature fields and thus explain the physics behind the results. This understanding is useful in guiding the computational trial-and-error process in the optimum direction.
The TileFlow Approach
TileFlow constructs a computer model of the data center and uses the technique of Computational Fluid Dynamics (CFD) to calculate the airflow pattern and pressure/temperature distributions. TileFlow is a reliable, quick, and cost-effective tool for:
- Designing efficient data centers
- Evaluating options for positioning new equipment
- Examining “what if” scenarios
- Streamlining installation and commissioning
- Preventing heat related outages of computer equipment
- Making cost-effective investments in cooling-related hardware
Distinguishing Features
- First CFD product dedicated to data centers
- Comprehensive, flexible, and robust
- Unparalleled ease of use
- Unmatched solution speed
- Unlimited technical support
- Modest computing resources
- Extensively validated
Hardware Requirements
- Operating System. TileFlow runs under Microsoft Windows operating system.
- Graphics Card. A discrete graphics card with 512 MB of memory (1 GB or larger preferred) and OpenGL support.
- Memory. RAM of 2 GB is adequate for most data centers. For very large data centers, you will need additional RAM and a 64-bit operating system. Please contact us to discuss this further.
- Processor. The processor speed determines the solution time. The faster the processor, the better.
Vent Summary
Vent summary presents the details of all the vents in the model. Depending on the parent object, the vents are grouped in six categories: Under-floor, Above-floor, Hot boxes, Spot coolers, Associated with upflow CRAC units, and Partitions. For each vent, the information presented include the parent object, the coordinates of the reference corner, type of vent (inlet/outlet/opening), and, if relevant, air flow rate, flow direction, and temperature.
Supply-Air Temperature Control
Supply-air temperature control can generally be modeled by specifying the set point temperature as the supply temperature, which is assumed independent of the return temperature. Under certain conditions, the control system may not be able to maintain the supply temperature at the set point, forcing the supply temperature to become higher than the set point and dependent on the return temperature. This comprehensive, more complete supply-air temperature control is now available for CRAC units and spot coolers.
Flow Tilt for CRAC Units
You can now specify flow tilt for openings on the front and rear faces of downflow CRAC units and for the vertical faces of the supply/top plenums of upflow CRAC units.
Positions of the Billboards
TileFlow now reports the orientations and positions of the billboards. This information is presented in a dialog box and gets updated as billboards are added or removed.
Add to Report Dialog Box
The Page Name dropdown now lists the pages in the report, making it easier to add content to existing pages.
Enhanced Report
The report now contains a fourth section, Transient, which contains selected results of the transient simulation.
Scheduler
The Scheduler has been modified to perform transient calculations. The files must have steady-state results calculated using TileFlow v7.0.
Improved Place a Vent Utility
When you click the toolbar button Place a Vent or use the command Partitions/Containments > Place a Vent, TileFlow now presents a dialog box outlining the next set of actions, including how to select another face on the highlighted object.
Select Vent Parent
Currently, if a vent covers the entire face of a 3D object or an entire partition, it is difficult to select the parent object; a mouse click selects the vent. The usual workaround is to hide the vent. TileFlow v7.0 removes this difficulty by adding a new command, Select Vent Parent, to the context menu for vents. You can now invoke the Properties dialog box for the parent object. If you want to move the parent object, use the arrow keys or press and hold the space bar and use the mouse. The new command and ways of moving the parent object are especially useful in the plan view or xy end view.
Customize Length Scales for Velocity Arrows
TileFlow now allows you to change the vector scales. By default, TileFlow automatically scales the velocity vectors to represent the largest vector by a reasonable length and minimize the overlap between the arrows, and the results plots are always satisfactory. However, the default scale varies from model to model, making comparison of velocity plots for different simulations difficult. The new version removes this difficulty.
Improved Import of Rack Data from Excel File
The facility for importing rack data from Excel file has been improved and simplified. The data needed has been divided into two groups — essential and optional, and the import will be successful as long as the file contains the essential data. TileFlow will assign reasonable default values for the missing optional data, which can be changed by the user. Further, checks have been added for improperly defined racks.
Locking Under-Floor Obstructions
You can now lock under-floor obstructions. This action will prevent their movement, but other attributes can still be edited.
Improved Numerical Scheme
The accuracy and robustness of the numerical scheme have been substantially improved.
Expanded Databases
The databases in TileFlow 7.0 have been expanded.
The results given by TileFlow have been extensively validated by comparing them with measurements in a number of data centers, and shown to be accurate.
In a CFD simulation, TileFlow takes as input the physical details of the data center (such as, its size and shape, and the locations and characteristics of the cooling units, servers/racks, perforated tiles, and obstructions) and uses an efficient, customized solver to produce detailed information about the airflow pattern and temperature distribution. The simulation-based approach is predictive in nature. It is ideally suited for studying the effect of proposed changes (e.g., addition, removal, and rearrangement of racks and servers, and “what if” scenarios) and for designing new data centers. Note that the proposed changes are made in a computer representation of the data center—not in the physical data center itself. Thus, the data center is not disturbed while the implications of various changes are being studied.
In addition to the CFD technique, TileFlow can also use measured temperatures (gathered using sensors) to calculate the temperature distribution in a computer room. In this sensor-based approach, it takes as input the geometry of the data-center layout and the sensor positions and temperatures. This approach is suitable if the objective is to just monitor the environmental conditions and trigger alarms/notifications.
TileFlow features an intuitive and easy-to-use graphical user interface, an efficient and accurate solution technique, and a variety of postprocessing tools for comprehensive reporting of the simulation results.
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