Over the past few months, we’ve provided data center cooling tips that eliminate hotspots and reduce energy usage, protecting your equipment and bottom line. By controlling data center temperatures and airflow, you reduce power usage – often the highest monthly data center expense.

In case you missed these helpful guidelines, you can read them here:

  1. Basic, low-cost thermal improvements: ways to close physical gaps to cut costs and gain easy energy-efficiency wins
  2. Improvements at the aisle level: solutions to contain and separate hot and cold air

This blog is the last of our three-part series, discussing data center cooling at the rack level. As technology continues to tax data centers through applications like virtualization and cloud computing, power rack density requirements are rising – which leads to thermal management challenges.

Improving data center cooling at the rack-level can be challenging, but it also has the greatest potential impact.

With hot racks, the hot air generated inside the rack may leak out and impact a different rack, slowing down the entire cooling process. Chimney containment manages this problem by mounting a metal chimney on the top rear of a rack, efficiently capturing and redirecting heat exhausted from rack equipment to a CRAC unit via ductwork or an air return layer.

This containment method completely removes hot air from the occupied space inside your data center, allowing the entire room to feel cooler. This can also lower operating costs, so you’re not paying to over-cool the space to keep temperatures comfortable.

Chimney containment is also very versatile; you can install chimneys on a one-to-one basis (one chimney per rack) or as a system (one chimney per several racks). Chimneys can be removed, added or moved as data center density grows or shrinks.

The only decision you have to make: passive or active chimney containment? 

Thermal Management Techniques to Improve Energy EfficiencyOption 1: Passive Chimney Containment

Using the natural convection of hot air rising, a passive chimney containment system allows CRAC return fans to draw exhausted hot air to cooling coils. This prevents hot air from mixing with cold air that enters the front of the cabinets, ensuring that the hottest air gets back to the CRAC unit and that the cold air remains cold.

Passive chimney containment works best in lower-density racks (between three and eight kilowatts). Make sure that you’ve implemented the suggestions for basic thermal management improvement before investing in passive chimney containment. For example, if you haven’t installed blanking panels to keep cold air from bypassing equipment and mixing with hot exhaust air, then you won’t gain the maximum efficiency possible.

Option 2: Active Chimney Containment

Active chimney containment works similarly to passive chimney containment, but it incorporates components to actively move air from the hot aisle to the CRAC return.Active chimney containment incorporates components to actively move air from the hot aisle to the CRAC return.Depending on the type of active chimney selected, different active components move the air. Belden’s active Adaptive Enclosure Heat Containment (AEHC) system uses variable frequency drive (VFD) fans and a control unit that adjusts fan speed based on rear-cabinet air pressure vs. temperature. This allows the controller to detect a change in pressure when new equipment is added to a rack, automatically increasing fan speed.

Why measure pressure over temperature? When individual servers increase their output to keep cool during high demand, the rest of the rack may sit idle. In these types of situations, the average temperature in the rack may not increase, but the rack experiences an increase in air pressure. By responding to the demand created within the rack, heat rejection always matches the load.

Remember: No matter what you do, your containment system won’t work unless you first complete basics steps to close the gaps in your data center.

To hear more about improving data center cooling, watch this free webinar: Thermal Management Techniques to Improve Energy Efficiency.

Through CFD modeling, Belden can show you how rack-level chimney containment will impact your data center environment. Belden also offers a variety of data center solutions for chimney containment that help you reduce costs, improve uptime and minimize energy usage.

Are there topics you would like us to discuss in future posts? Let us know in the comments section below!