Maintaining energy efficient enclosure climate control

How to design, install and operate for energy efficiency.

By Eric Corzine, Product Manager – Climate Control, Rittal Corporation

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Finding ways to do more with less has transformed energy efficiency from a “green business” luxury to an operational necessity. All operations seek ways to increase energy and cost savings without hurting productivity.

Enclosures, housing the sophisticated, sensitive electronics and drives, protect them from the rugged environments and ambient conditions they are deployed in. It is imperative that these enclosures be cooled to ensure proper performance and avoid heat-related downtime.

Creating effective and energy-efficient climate control solutions for industrial applications consists of three key phases—design, installation, and operation.

The design phase

Does this application require cooling, and if so, how much? It is important to determine the correct amount of cooling to prevent energy from being wasted by cooling components to lower-than-needed temperatures or even by cooling components that might not need it at all. The necessary climate control solution for any application begins with three questions: how big is the enclosure? How much heat will be created by the installed equipment, and finally, where is the enclosure going to be located?

Selecting the right climate control solution

If the ambient temperature is less than the enclosure temperature, will NEMA 12 protection be required? If no, a louvered grill or roof vent may suffice. A filter fan or air-air heat exchanger should be installed if NEMA 12 protection is needed.

If the ambient temperature is higher than the enclosure temperature, more robust cooling methods may be employed. If chilled water is available at the site, an air-water heat exchanger will cool the components. Without chilled water, an air conditioning system and/or a chiller system plus an air-water heat exchanger should be considered. The following flowchart illustrates what products may be applicable to a given situation.

Determining the surface area of the enclosure

The surface area of the enclosure is where the heat will move into the enclosure or be dissipated. Since heat moves from hot to cold, the surface area determines the heat flow. Although you could determine the area using high school geometry, a formula takes into account the positioning of the enclosure, whether it is against a wall, free standing or among a suite of enclosures.

Calculate “Contained Heat”

With the surface area determined, you can calculate “contained heat.” For an existing, completed system, the temperature difference can be gauged by using the difference between the interior of the enclosure (Ti) and the surrounding exterior environment (Ta). When configuring a new system, those values can be found by totaling the heat loss from all installed components utilizing the information found on each data sheet.

Heat Calculation for a Previously Completed System

Qe = Qv – A × k × ΔT

Where:

  • Qv is the amount of heat from the components inside the enclosure
  • A is the effective surface area from the calculation above
  • k is 5.5 w/m2 Celsius (sheet steel, different numbers for different materials)
  • ΔT is the temperature difference Ta-Ti in Celsius

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After this calculation is completed and Qe, the amount of heat contained inside of the enclosure is determined, now the selection of the climate control solution can begin. Among the common solutions: filter fans, air-to-water heat exchangers, air conditioners or air-to-air heat exchangers, each has benefits and strengths based on its application. From an energy efficient standpoint, filter fans and air-to-air heat exchangers will use less energy, but require an ambient temperature below that of the desired internal temperature to be effective. If cooling to temperatures below the ambient air is needed, an air conditioner or air-to-water heat exchanger must be used.

The design phase, including the proper selection of a climate control device, maximizes the energy efficiency of an application. Correct installation and operation complete the steps for using less energy.

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