Working with the Capture Index

Working with Capture Index The cooling simulation tool enables you to simulate the effect of potential changes to the cooling conditions. You can view the data center temperature map in a 2D floor layout with various views. In the Cooling overlay of the data center floor layout, you can see a color-coded overview the Capture Index (CI). You can use this view to get an overview of the reasons why the tile airflow may not be the same across the room. You can simulate where to place equipment without overheating the room or creating hotspots by following the color-coded indications, for example position new devices and move or delete existing devices without exceeding recommended exhaust air captured by the cooling units. Subsequently, you can use the plenum overlays to drill down into looking at specific pressure or velocity issues in the plenum. Each rack in a well-formed hot aisle/cold aisle layout shows a color-coded capture index (CI) percentage. The CI value identifies inlet air which is supplied by what fraction of the equipment's exhaust airflow is captured by the InRow® cooling units included in that row pair or by the CRAC or CRACs in the room through the perforated tiles. Select the Cooling tab in the floor layout. Add CRACs, InRow® cooling units and perforated tiles as needed by dragging them from the Genomes pane into the layout. Review or modify the cooling settings of the added equipment or the room as needed by right-clicking the item, and selecting Properties, and using the settings in the Cooling page. Simulate failure of one or more cooling units by selecting one or more cooling units in the floor layout, right-clicking, and deselecting Activate. Simulate cooling performance changes of one or more racks by selecting one or more racks in the floor layout, right-clicking and selecting Cooling>Normal: 160 CFM/kW, Blade: 105 CFM/kW or another value*, if available. Tip To select more than one cooling unit, hold down the Ctrl key and select the items, or drag a box around the items you want to select. *Value defined in the Rack's cooling properties page. 102237281_360038496673.png 102237570_500x132_360038496673.png

Troubleshooting why Capture Index values do not display The cooling simulation updates based on the equipment placement. If your configuration is invalid, the tool tip will inform you of the problem. If the cooling calculations do not run, verify your configuration is not invalid due to one of the following: The distance between the racks is insufficient (at least 2 feet). Hot air blows from one rack into the front of another rack. To make the cooling configuration valid, use the room layout icons and drag the row border to make the aisle wider. The row layout is not well designed. The equipment is placed in pairs directly across from each other but is misaligned by 10 cm or more. To make the cooling configuration valid, drag the equipment closer to each other. There is a piece of equipment placed in the aisle between the rows. To make the cooling configuration valid, move the equipment out of the aisle.

About the Capture Index (CI) colors Each rack in a valid equipment cluster for which cooling can be calculated shows a capture index (CI) value and is colored based on cooling performance: red ("bad"), yellow ("marginal"), or green ("good"). Most configurations are valid. However, cooling cannot be predicted for some configurations such as when racks are not arranged in alternating cold and hot aisles. In this case, no CI value or color is shown for any rack in the immediate vicinity of the invalid configuration. For valid clusters, the actual CI value shown and associated color is based on the larger of the two hot and cold aisle CI metrics for the rack. The CI color coding is related to the cooler supply and maximum target temperature as shown in the figure below. This color coding ensures better airflow management is enforced as the difference between cooler supply and maximum target temperatures approach zero. For example, if the cooler supply temperature and maximum target temperature are both 20°C then ΔT=0 and CI must be 100% for a rack to achieve a "green" rating. If the cooler supply temperature is much lower than the maximum target temperature, there is a large "operating margin" and more tolerance for less ideal airflow management. Capture Index (CI) color 102237268_360038495153.png

About Capture Index prediction models Capture Index Cooling-Performance Metric Unlike temperature-based metrics, Capture Index (CI) is solely a function of airflow. There are two kinds of CI: Cold Aisle CI: the fraction of air ingested by the rack which originates from local cooling resources (e.g. perforated floor tiles or local coolers) Hot Aisle CI: the fraction of air exhausted by a rack which is captured by local extracts (e.g. local coolers or return vents) CI measures effectiveness of supplying cooling air to rack inlets or scavenging heated air from rack exhausts on a 0% (bad) to 100% (good) scale. CI is defined in terms of local cooling resources (airflow from tiles, local coolers, local extract vents, etc.) and it measures the robustness and scalability of a grouping of equipment. Example Cold Aisle The Cold Aisle Capture Index of the top-middle rack is 84%. In other words, 84% of the airflow drawn in by that rack originated from the perforated floor tiles. The remaining 16% of inlet air comes from other sources including the room ambient and recirculation from the subject rack and others. Hot Aisle The Hot Aisle Capture Index of the bottom-right rack is 66%. In other words, 66% of the exhaust airflow from this rack is captured by the local coolers while the additional 34% escapes, heating the room ambient and, potentially, entering rack inlets. 102237282_360038495213.jpg