Managing Airflow at the Row Level
Data center containment best practices that don’t bust your budget — Part 2
To put it simply, row-level airflow management refers to improving cold aisle and hot aisle separation. It’s typically done once you’ve made improvements at the rack level (e.g. blanking panels) and raised floor level (e.g. brush grommets). When we talk to data center operators about improving airflow efficiency at the row, they’ll jump ahead to containment a little too quickly. The fact is, there are several areas in the row that can be addressed without engaging in a full-blown containment initiative.
But before we jump into cost-effective row-level suggestions, we should point out that the goal of any airflow management initiative should be to improve the intake air temperatures to IT equipment. More specifically, to reduce the highest intake air temperatures so that all intake temperatures are as low and even as possible. Doing this enables you to make changes to the controls of the cooling infrastructure, such as increasing temperature set points; lowering fan speeds; or, in many cases, turning cooling units completely off. Making these changes are key to achieving many of the benefits of airflow management: improved efficiency, increased capacity, and reduced operating costs. While we’re limiting this article to row-level best practices, airflow should be managed at all levels in the data center — rack, row, raised floor and room — to fully capitalize on all these benefits. Want some rack-level tips that won’t bust your budget? Click here.
Block Open Spaces Underneath Cabinets
You might not think it, but the small space between the bottom of an IT rack and the raised floor/slab can significantly impact airflow management as well as the intake temperatures of IT equipment. Usually a ½-inch to 2 inches in size, this space allows IT equipment exhaust air to travel under the rack and ultimately back into the IT equipment air inlets. This process — exhaust air recirculation — can cause several problems for the data center: increased intake temperatures, hot spots, and a likelihood of IT equipment failure in the long term. These problems will, in turn, require running more cooling units, higher fan speeds, and lower cooling unit temperature set points to overcome the mixing. But blocking off these open spaces with under-rack panels is an easy and cost-effective way to reduce your IT equipment inlet temperatures.
Seal Spaces in Your Cabinet Rows
When we visit a data center, all too often we see efficiency losses due to large gaps between cabinets (either due to a building column or a cabinet that’s been removed) that haven’t been sealed off. Sealing these gaps is important for a couple of reasons. Just as with gaps underneath racks, exhaust air recirculation can occur. Second, a large volume of conditioned supply air can be lost. Bypass airflow occurs when any amount of supply air bypasses IT equipment and returns to the cooling unit unutilized. Like exhaust air entering the cold aisle, bypass airflow requires more cooling units to be running or higher fan speeds in order to overcome the loss of conditioned airflow volume. Blocking off any open space between cabinets, whether it’s just a couple of inches or a few feet, with rack gap panels or sealing foam will dramatically impact IT equipment intake temperatures at a reasonable cost.
Even if you’re missing a cabinet at the end of an aisle, causing uneven aisle lengths, there are still innovative ways to reduce bypass airflow. An adjustable mounting post, for example, provides a structural support surface to shore up uneven rows by enabling the attachment of rack gap panels and aisle-end doors.
Contain Hot or Cold Aisle Ends with Doors
You don’t have to engage in a full-blown containment project to reap the benefits of aisle-end doors. Cabinets at the ends of rows are the most vulnerable to increased IT equipment intake temperatures because of the large potential for hot exhaust air to wrap around the ends of rows. Whether applied to hot or cold aisles, aisle-end doors will still yield huge benefits by eliminating exhaust air recirculation in this area.
There are many door solutions available in a wide range of price points, but their real cost savings benefit is your ability to avoid the cost of full containment. Whether containment is something you’re doing in phases or simply a budgetary decision, aisle-end doors are an effective solution that can be applied in singularity and still be extremely effective in reducing IT equipment intake temperatures.
Contain the Tops of Cabinets
Containing cabinet tops on either the hot or cold aisles is the next step in containment, typically deployed in situations of high cabinet densities or when the highest possible efficiency is desired. In cold aisles, this involves some form of partitions, baffles, or roofing over the aisle to contain conditioned supply air. In hot aisles, a configuration of baffles or duct work runs from the hot aisle to the returns of the cooling units.
As with doors, there’s a wide range of solutions and prices. Unlike doors, the styles of options can vary greatly. In most cases, full containment (full roof over cold aisles or complete ductwork from the tops of hot aisles to cooling unit returns) is unnecessary. In our experience, angled baffles for cold aisles or vertical baffles for hot aisles get the job done and are cost-effective.
For many airflow management improvements, especially aisle containment, it’s long been necessary to hire a third-party crew for installation. Thankfully, this is now no longer required. Magnetic attachments can be used for solutions that address all the best practices we’ve discussed: under rack panels, rack gap panels for gaps within rows, aisle-end doors, and rack-top baffles. Eliminating the need for outside install support allows for a quicker return on investment (ROI) from your airflow management improvements.
Secondly, due to their magnetic attachments, these airflow management solutions are modular in nature. They can be uninstalled and reinstalled at will, rather than being a fixed installation. Data centers are dynamic environments that should be reconfigured when they change. Having the flexibility to reconfigure airflow management solutions as your data center evolves is not only convenient but can also save on removal and reinstallation costs down the road.
Match Cooling Capacity with IT Load
Airflow management alone doesn’t reduce your cooling energy costs. What it does do is improve IT equipment intake temperatures, enabling you to make changes to the cooling infrastructure. If you’ve implemented our airflow management best practices correctly, you should now have an excess of conditioned supply air in your cold aisles because there’s no longer any mixing of exhaust air with conditioned air, and vice versa. Your next step needs to be matching the cooling required by the IT load with what’s being supplied by the cooling units. Matching can come in the form of raising set points, lowering fan speeds, or turning cooling units off altogether. This is an iterative process that should be done in incremental steps with constant evaluation of IT equipment intake temperatures. We’ll discuss this process (room-level airflow management) in our next article.
Row-Level Airflow Management Isn’t All About Containment
There are many holes and gaps in the row that need to be sealed if you want to manage airflow effectively. In situations where cabinet densities are high enough, or the highest possible efficiency is desired, hot or cold aisle containment is necessary. But that doesn’t mean full containment is your only option. Partial containment in the form of only aisle-end doors is an extremely effective strategy to reduce IT equipment intake temperatures.
Furthermore, when top-of-rack containment is necessary, modular baffles are cost-effective and just as impactful as a full roof or duct work in cold or hot aisles, respectively. Lastly, stay abreast of innovative solutions for row-level airflow management solutions that utilize magnetic attachments. They’ll give you the biggest cost saving opportunities by reducing or eliminating installation costs altogether.