Cooler enclosures add performance, reliability

Enclosure design: Control, electronics, network, and data center enclosures require temperature control techniques for reliable performance. Isolating high-temperature components is an increasingly popular method.
By Brian Mordick April 18, 2012

Equipment enclosures for controls, electronics, network equipment, and data centers require cooling for reliable performance. Processing power, the speed at which crucial networking equipment runs, is steadily increasing to keep up with user application demands. Through technology advances, the size of these electronics is shrinking—resulting in greater board population density and higher power consumption. However, this yields increased heat generation throughout the data center.

Chimney cabinets remove heat from the cabinet or aisle and reduce wasted cold air by 99% with less than 1% of hot air/cold air mingling. Courtesy: Pentair Technical ProductsHigh heat levels can damage networking equipment and potentially eliminate a company’s ability to effectively process, communicate, and store information. Implementing the proper cooling solution will not only protect data centers from costly damage, but also ensure continuous access to company data and communications.

Cooling solutions have become more sophisticated—providing new methods for improving cooling while enhancing overall efficiency to adapt to changing networking equipment and data center designs. Control engineerings, operations engineers, and data center managers can select and implement solutions that adequately address individual cooling requirements by understanding the evolution of modern cooling solutions, along with advantages and disadvantages.

Choosing the appropriate cooling strategy consists of more than simply selecting the right design. Applying the appropriate cooling configuration also requires considering the total-cost-of-ownership (TCO) requirements. Cooling TCO costs are not limited to capital expenses associated with purchasing and implementing cooling equipment. Data center managers must also include operational costs and additional design features that can lead to significant savings.

Diverse cooling configurations

Cabinet configurations are available in a variety of options, ranging from simple and inexpensive to costly and complex. However, the goal of each configuration is the same: help deliver the necessary amount of cool air to each server.

Hot aisle/cold aisle

Hot aisle/cold aisle cooling systems are designed to separate hot exhaust from cold intake air. Cabinets located on both sides of the cold aisle draw cold air through their front intakes, using it to take heat away from the equipment. Hot exhaust exits through cabinet rears and is directed to computer room air conditioner and computer room air handler (CRAC/CRAH) units, which remove the heat and redistribute air to the cold aisles.

Playing a crucial role in airflow management, hot aisle/cold aisle configurations provide numerous benefits. By separating hot and cold air, the energy required to maintain the optimal data center temperature is minimized—allowing facilities to significantly reduce utility costs. However, it is important for managers to understand that hot aisle/cold aisle designs typically can accommodate heat dissipations of only 3 kW to 5 kW. Once rack densities reach 5 kW and above, the system can no longer compensate for the increased heat loads. According to multiple outside studies, most hot aisle/cold aisle solutions use only 40% of the available cooling capacity, while 10% of system racks still experience hot spots—which can result in equipment overheating and system failures.

Chimney cabinet cooling

Chimney cabinet cooling solutions consist of a cabinet with top ductwork, which directs hot exhaust air to an above drop ceiling or ductwork that further directs the airflow to the intakes of the CRAC/CRAH unit. Studies have shown that chimney configurations successfully extract heat loads up to 20 kW. By providing a direct airflow path for hot air, chimney cabinets perform crucial airflow management—removing heat from the cabinet or aisle and reducing wasted cold air by 99% with less than 1% of hot air/cold air mingling.

Numerous outside studies show that the chimney method lowers cooling system costs by at least 25%. Additional cost-saving benefits associated with chimney cabinets include: low capital costs, little to no maintenance, and fewer CRAC/CRAH units required.

Containment systems

Rather than simply separating cold and hot airflow, containment systems erect a barrier to segregated airflows—preventing them from mixing, which reduces energy costs, minimizes hot spots, and improves the data center’s carbon footprint. These systems are designed to enclose the hot or cold aisle through the use of aisle-way doors, roof panels, and internal sealing within the cabinets. Containment systems offer two cooling options: cold aisle containment or hot aisle containment.

Containments systems erect a barrier to segregated hot and cold air, preventing them from mixing, which reduces energy costs, minimizes hot spots, and improves the data center’s carbon footprint. Courtesy: Pentair Technical Products

In a cold aisle containment configuration, the cold air is enclosed within an aisle and hot air is prevented from entering the aisle, ensuring that the equipment will use only cold air for cooling. The cold air can be supplied by perimeter CRAC/CRAH units—typically through a raised floor—or internally through a cooling source located between or above the racks.

According to a 2007 Pacific Gas and Electric Study, containment systems can provide an average of 20% savings in chiller operating costs. This allows them to decrease the energy needed to move cold air by 75%, according to a study completed by Lawrence Berkley National Laboratory.

Conversely, hot aisle containment solutions are designed to contain hot airflow and direct it back to the cooling units, via overhead ductwork or with in-row cooling for localized air conditioning. Hot aisle containment systems can significantly increase cooling unit efficiency because the hot air is ducted directly to the CRAC/CRAH unit. Segregation is quickly becoming an ideal option for high-density data centers on grade that duct the hot aisle air above and out the cooling units, while using in-row cooling near the heat source improves overall air handling efficiency.

In-row cooling

Dedicated cooling units placed between cabinets allow in-row cooling to capture exhaust air and neutralize it before it mixes with cold air. In-row cooling offers a stand-alone cooling system for some small rooms that can replace CRAC units, providing high-density cooling capacity. Additionally, in-row cooling can be used with hot aisle/cold aisle configurations, adding to existing cooling solutions to accommodate growth.

In-row coolers provide inherent scalability, seamlessly allowing users to adjust cooling to accommodate any data center’s growing networking needs or evolving designs. Courtesy: Pentair Technical Products

In-row cooling solutions offer a simple way to achieve reliable, high-powered cooling for specific rows. Units provide inherent scalability, which allows users to seamlessly adjust cooling to fit any data center’s growing networking needs or evolving design requirements.

Designed to deliver cool air only where it is needed most throughout the data center, in-row cooling increases cooling efficiency dramatically. By significantly decreasing the amount of wasted energy, in-row cooling solutions can result in an estimated 82% utility savings.

Total cost of ownership

Data center managers must balance selecting the proper cooling configuration with the total cost of ownership associated with each solution.

Installation versus operation

Understanding the difference between installation cost factors and operational cost factors is important when selecting the appropriate cooling strategy. For example, legacy configurations are simple to install and can be done with very little capital costs; however, the energy needed to run these systems may result in excessive utility expenses. They can also be unreliable, creating hotspots and leading to potential equipment malfunctions—ultimately leading to more labor costs.

Systems that have high capital costs may still experience lower operation cost, ultimately saving a substantial amount of excess expenses. For instance, containment systems can be expensive to implement, but due to low-to-moderate operating costs and high reliability, containment systems can be a cost-effective solution for sophisticated cooling requirements.

Thousands of dollars in savings per year

Understanding the difference between installation cost factors and operational cost factors can be a huge deciding factor in selecting the appropriate cooling strategy. Courtesy: Pentair Technical ProductsDepending on the company’s cooling strategy, businesses can experience significant annual savings. Characteristics of the cabinets can affect server performance, which ultimately impacts operational costs. Each server manufacturer has specific guidelines concerning the amount of open space required on cabinet front doors. To provide servers with enough cold airflow to dissipate the heat generated and ensure that the cold air is not restricted from entering the installed equipment, doors must have at least 50% open space.

Increasing heat dissipation from a cabinet can be also be achieved by the proper placement of fans. Fans on the rear doors can be used in conjunction with server fans to increase the airflow in specific areas and assist in eliminating hot exhaust air from the cabinet. In random layout data centers, the best way to remove heat from the top of a cabinet is to install a perforated top or a top-mount fan. However, in more efficient hot aisle/cold aisle layouts, the use of top-mount fans can actually impede heat dissipation and overall server thermal performance by drawing cold air away from the server and mixing the cold air with hot exhaust air, wasting the energy originally used to create the cold air.

Additional cooling solutions can be implemented to improve efficiency, providing businesses with significant savings annually. Courtesy: Pentair Technical ProductsFinally, accessories can be used to assist with cabinet airflow. Companies can implement blanking panels or floor brushes to achieve additional data center efficiency in hot aisle/cold aisle configurations, providing an easy solution with a large fiscal impact. Blanking panels are used to fill empty cabinets and rack space and solid walls are installed to prevent cold air from rushing through cabinets, bypassing equipment and mixing with hot exhaust. Using blanking panels ensures cold air will only pass through equipment to dissipate, providing an easy-to-install and highly effective method for directing cold air, potentially offering tens of thousands of dollars in savings annually. Floor brushes, on the other hand, act as a plenum for distributing cold air to network equipment and provide cable distribution. Rather than using simple cutouts, floor brushes, which act as an airflow block, prevent cold air from leaking through cable entryways into the hot exhaust air.

More networking, more savings

To meet the communication needs of any business, technology will continue to evolve by providing networking equipment with capabilities that enable faster data transmissions, and larger memories and storage capacities. More powerful data centers require organizations to implement solutions that deliver superior protection for networking equipment and remain energy efficient, saving thousands of dollars every year in utility costs.

– Brian Mordick is senior product manager – cabinets, Pentair Technical Products’ Hoffman Brand. Edited by Mark T. Hoske, content manager, CFE Media, Control Engineering, Consulting-Specifying Engineer, and Plant Engineering