Management and predictions of operational changes and growth in mission critical facilities
The main challenge in understanding the cooling performance in a legacy data center is the invisible transport medium (air). This emphasizes the need for smart and meticulous measurement techniques. However, the nature of measurements is finite (e.g. top, middle and bottom) and the variation between often non-linear, therefore to capture the gradients between measured points a validated CFD simulation is needed. In this paper a brief description of an experimental characterization of a new data center lab is discussed. Airflow and temperature measurements are utilized to understand the facility's performance at different operational stages, until reaching the designed capacity. Since the facility houses a wide range of different IT equipment (servers, switches, storage and blades), it is important to understand the airflow demand of each. To do that, each type of IT was tested separately and flow characteristics were obtained (i.e. free delivery, critical pressure and flow curves). In the second part, all the characterization data is integrated via compact models into a full CFD simulation. The measured points are used for validation and the full field of air temperature and flow is resolved. Both the measurements and simulation data will now be used to answer important design, deployment and operational change questions.
Experimental and Numerical Characterization of a Raised Floor Data Center Using Rapid Operational Flow Curves Model
As the number of data centers is exponentially growing globally, pragmatic characterization schemes are considered to be a necessity for measuring and modeling the load capacity and flow pattern of the facility. This paper contains experimental and numerical characterization of a new data center laboratory using practical measurements methods, including tiles and CRAH flow measurements. Then a full physics based CFD model is built to simulate/predict the measured data. A rapid flow curve method is used showing high accuracy and low computational expense.Detailed descriptions of the data center structure, dimensions, layout (Appendix, A-1) and flow devices are given. Also, modeling parameters are mentioned in details to provide a baseline for any investigative parametric or sensitivity studies. Four experimental room level flow constraint scenarios are applied at which measurements were taken, (Appendix, A-2). The model is then built and calibrated then used to predict measurements.Measurements of the cooling unit were performed using hot wire anemometry with a traverse duct installed at the top of the CRAH. The tiles measurements were carried out using a flow hood with back pressure compensation. A detailed CFD model is constructed to predict the four experimental cases. For modeling the interdependency between the flow and pressure in flow devices flow curve approach is used. This is a rapid modeling technique that relies on experimentally measured (for IT) or approximated (for CRAH) flow curves. Applying the operational flow curves boundary conditions at the vents of the flow device results in a very accurate simulation model. It is also shown that the flow curves can be used to predict the real-time flow rate of servers at known RPM. This greatly simplifies flow rate measurements of IT in the data center.Copyright © 2015 by ASME
Hybrid Cooling Technology for Large-Scale Computing Systems: From Back to the Future
A technical perspective of hybrid cooling methodology, comprised of pumped water cooling with incorporated convection air cooling, for densely packaged high performance computing systems is presented in this paper. The technology has been implemented in the Fujitsu high-end server GS8900 (released in 1999), and proposed with technical innovations for future large-scale computing systems. Design strategies of cooling systems, including water cooling modules, water flow and distribution units as well as air convection architectures, are reviewed, together with advantages and performance of the technology analyzed. Low temperature chilled water is utilized in these systems, where the system board is assembled with a liquid cooling unit on each one for cooling of major processor and supporting chips. Memory modules, other devices and components on the system board, as well as power supply units in the rack, are cooled by ambient air convection. Besides of the high cooling capability, attention is given especially to advantages of the technology with tremendously lowered power consumption, enhanced system reliability and increased packaging density, improvements in cooling efficiency and easy of serviceability are emphasized as well.Copyright © 2011 by ASME