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One of the fundamentals of operating an efficient Data Center is to eliminate the mixing of hot and cold air that can lead to significant Computer Room Air Conditioner/Computer Room Air Handler (CRAC/CRAH) inefficiencies. That’s where containment comes in.

There are many containment solutions available in the data center market—all designed to apply cold air to the IT equipment inlets and direct hot exhaust air back to CRAC/CRAH units without mixing with cooler air.

Personally, I was never a fan of chimney containment until Denis Blouin, my friend and Belden’s Product Line Manager for rack and enclosure solutions, introduced me to the concept. Due to its simplicity and the efficiencies that can be achieved when properly deployed, chimneys have now become one of my favorite containment methods. Let’s start by looking at passive chimneys.

The Passive Approach

As in all chimney containment systems, a passive chimney connects to the ceiling plenum to provide a direct pathway for hot exhaust air to return to the CRAC/CRAH units. Passive chimneys do not use any intelligence or active components to move air from the hot aisle side of the cabinet to the CRAC/CRAH return—hence the term “passive.”

Instead, these systems use the natural convection of hot air rising and the CRAC/CRAH return fans then draw the air back to the cooling coils. Passive chimney containment works very well for cabinets with densities ranging between 3 and 8 kilowatts when CRAC/CRAH units are properly placed within the data center to provide even airflow.

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More to Consider

There is more to a good passive chimney containment solution than the chimney itself. To provide highly effective cold and hot air separation, the cabinet must also provide plenty of ventilation for the IT equipment fans to easily draw in cold air. For example, Belden’s passive Adaptive Enclosure Heat Containment (AEHC) system features a vented cold aisle cabinet door that provides 78% perforation or the option to not use a cold aisle door at all.

Blanking panels installed in open vertical and horizontal spaces on the cold aisle side of the cabinet are also critical to keeping cold air from bypassing the equipment and mixing with the exhausted hot air of the cabinet. The cabinets should also feature solid rear doors and a solid top with cable entries or other openings that use rubber grommeting material or brushes to ensure as much separation as possible and prevent hot exhaust from flowing out into the data center.

Give Them a Try

In the right data center environment, passive chimneys are an excellent solution for improving data center energy efficiency and resolving heat issues. They can even be deployed in new and existing data centers or used for spot applications.

And if your data center does not have a finished ceiling, taller chimneys can be installed between 18 and 24 inches from the ceiling slab on both the cabinet and CRAC/CRAH units. While not quite as efficient as a closed system using the ceiling plenum or duct work, adequate separation can still be achieved due to the rising of hot air.

In my next blog, I’ll take a closer look at active chimney containment and how it can provide the proper balance between cold aisle temperature, IT equipment fan speed and hot air return temperature in higher density environments.