Computational Fluid Dynamics

The best way to design an optimized airflow management program is through the use of a Computational Fluid Dynamics (CFD) study. SubZero Engineering has performed over 300 CFD studies for data centers throughout the US. This level of experience gives our engineers a decided advantage as to the best way to optimize hot and cold air separation.

There is a key difference between physical measurements and field-testing that is not only time and labor intensive but sometimes impossible to fully achieve. In such a situation, CFD simulations provide a feasible alternative for testing various design layouts and configurations in a relatively short time. CFD simulations can predict the air velocities, pressure, and temperature distribution in the entire data center facility. They can be used, for example, to locate areas of recirculation and short-circuiting or to assess airflow patterns around the racks. In addition, CFD simulations can assist in predicting the non-dimensional indices described above for quantifying rack cooling effectiveness and thermal effectiveness. Facilities managers, designers, and consultants can employ these techniques to estimate the performance of a proposed layout before actually building the facility. Likewise, CFD simulations can also provide appropriate insight and guidance in reconfiguring existing facilities toward the same goal of optimizing the facility’s cooling system.

CFD Modeling

Computational fluid dynamics (CFD) analysis can be an effective tool for the optimization and troubleshooting of airflow. As mentioned before, an energy-efficient layout of a data center depends on several factors, including the arrangement and location of various data center components including the positioning of air-conditioning systems and positioning of racks and other components. CFD analysis, which is based on sound laws of physics, can help visualize airflow patterns and resulting temperature distribution in a data center facility. Any mixing and short-circuiting airflow patterns can be visualized through the airflow animations based on CFD analysis instead of intuitive imagination.

Optimization of data center layout and equipment selection through CFD analysis at the design evaluation phase can help in avoiding future problems related to poor airflow distribution and resulting hot spots in the data center facility. CFD analysis can provide a detailed cooling audit report of the facility, including the performance evaluation of individual components, including air-conditioning units, racks, perforated floor tiles, and any other supplementary cooling systems in the facility. Such reports can help in the optimization, selection, and placement of various components in the facility.

For example, such CFD-analysis-based cooling audit reports of air-conditioning systems can predict relative performance of each unit, indicating over- or underperformance with respect to other units on the floor, which can affect the energy efficiency and total cost of ownership long term. Performance of each component can be easily tested against the guidelines in Thermal Guidelines for Data Processing Environments (ASHRAE 2004h) to meet the optimum requirements. CFD analysis can also help in predicting the non-dimensional indices (RCI, RHI, and SHI) described earlier. Testing and evaluation of these indices would require extensive measurements of several entities such as inlet temperatures at each server, and airflow measurements through each perforated floor tile, each server, and through each air-conditioning unit. CFD analysis, if performed at the design evaluation phase, can predict the overall values of these indices not only at the entire facility level but also at the individual component level.