The modern business environment has transformed energy efficiency from a luxury sought after by ‘green’ companies to a necessity for all operations that seek energy and cost savings without harming productivity. Mark Madden reports.

Budget constraints demand that ways be found to do more with less.

Sophisticated, sensitive electronics and drives are the backbone of many industrial applications, and such equipment is often placed in enclosures to protect it from rugged environments.

According to the Rocky Mountain Institute, a non-profit efficiency-focused research organisation in industrial settings, there are abundant opportunities to save 60% of the energy and costs in areas such as heating and cooling.

This article discusses tips for cooling enclosures that can reduce energy consumption and save money.

How much cooling?
It is important to determine the right amount of cooling to prevent energy being wasted by cooling components more than is necessary, or even by cooling components that may not require it.

The most ‘energy efficient’ cooling strategy is one that isn’t needed in the first place.

To figure out the appropriate climate control solution for a given application, three factors should be determined: enclosure size, the heat created by installed equipment, and enclosure location.

It’s then possible to do some calculations manually or with computer software. For this article the former is used.

The first step in selecting the right climate control solution is to consider the factors in Figures 1 and 2 to see what product types are applicable in a given situation.

The enclosure’s surface area (size), the ambient (surrounding) temperature and the amount of (installed) heat in the enclosure should be taken into account.

What does surface area have to do with climate control? Heat flows in one direction: from hot to cold. This is why coffee cools after a few minutes as it sits on a table. The room is cooler than the coffee, so the heat ‘leaves’ the cup and is diffused throughout the room.

In the case of climate control, it must be determined whether surrounding heat will move into the enclosure or heat from the enclosure will be dissipated. The surface of the enclosure is where this interaction takes place and, as in the coffee cup, heat will flow from the sides, top and bottom.

It’s easy to calculate the total surface area. However, the heat dissipation may not be even. For example, if the rear of a warm enclosure is placed against a wall, then the wall will heat up in that spot, creating less of a temperature difference between the wall and the enclosure. This will slow or prevent heat flow out of the enclosure.

Because of this, it was decided by an international convention (DIN 57 660 part 50 and VDE 660 part 500) to modify the surface area of an enclosure to take this into account (Figure 3).

Once the surface area of an existing system is found it’s possible to calculate ‘contained’ heat by using the temperature difference between the interior and the surrounding environment.

When configuring a new system, total heat loss from installed components can be calculated using information usually included on their data sheets.

Climate control types
If there’s a need for climate control after the amount of enclosure heat is determined (Figure 4), then selection of the correct solution can begin in earnest.

There are several common types to suit different requirements, including filter fans, air-to-air heat exchangers, air-conditioners and air-to-water heat exchangers. Each has distinct strengths and benefits.

From an energy-efficiency standpoint, filter fans and air-to-air heat exchangers use less energy but require an ambient temperature lower than the enclosed temperature to be effective.

If cooling to temperatures below ambient conditions is necessary, an air-conditioner or air-to-water heat exchanger is necessary.

Proper selection of a climate control device is an important starting point for maximising the energy efficiency of an application. Other factors, such as placement on the enclosure and in relation to the internal and external surroundings, and general maintenance, can also lead to a substantial increase in efficiency.

Mounting components
When mounting any components on or in enclosures, it is important to leave enough space for climate control to work effectively (Figure 5).

In the examples shown there are cables, books, spare parts and other objects blocking the airflow around enclosure components. The risk of heat-related failures or shorter lifespan is drastically increased.

Figure 6 shows how cables and other obstructions can be removed to provide adequate airflow in an enclosure.

Another common problem that can hamper efficiency is climate control that doesn’t have enough room to ‘breathe’.

Generally speaking, components should be at least 200mm from incoming air generated by climate control products. Component fans should not blow against cooling unit fans, as this may cause a short circuit.

Outside the enclosure, it is best to keep 200-400mm between surrounding objects and the climate control device to allow adequate airflow.

The correct installation of climate control on the enclosure is crucial for effective operation. Unless otherwise required by an application, it is usually recommended that filter fans be placed at the bottom of an enclosure and the corresponding exhaust filter at the top of the opposite side.

This way, the fan can draw in the cooler air near the floor and cross-ventilation is created in the enclosure for increased heat removal.

Air-conditioners and heat exchangers can be mounted on the walls or roof of an enclosure and should be installed according to the manufacturer’s instructions for best results.

Another way of boosting climate control performance lies in the planning stages. Keeping enclosures far enough from any heat sources prevents excessive heating and possible damage (Figure 7).

Proper sizing and efficient deployment are easy ways of getting the greatest returns from industrial climate control products, but maximizing efficiency doesn’t stop there. Maintaining the units over the course of their service life will keep performance levels up and energy use down.

Filter fans and air-conditioners
Maintaining filter fans is relatively simple, as it’s usually possible to determine with a glance whether the filter is dirty and needs replacing.

This may sound rudimentary, but it’s important for effective fan operation. Regular maintenance is required for air-conditioners as well, although the areas of concern may not be quite as apparent.

To understand the required general maintenance, we need to take a simplified look at how air-conditioners work.

There are two sides to an air-conditioner: the hot one on the outside of the unit and the cold one on the inside. There are copper coils on both sides: the condenser coil externally and the evaporator coil internally.

Refrigerant moves back and forth inside these copper coils and transfers heat from the inside of the enclosure to the outside. To circulate air treated by the coils, fans blow across them, making it problematic if they become blocked or clogged with contaminants. Airflow is reduced and the unit becomes less efficient – working harder, using more energy and producing less cooling output (Figures 8 and 9).

To prevent the condenser coil from becoming clogged, the coil itself can be treated with a protective substance such as Rittal’s RiNano coating. This prevents dirt, oil and other contaminants from sticking to it.

Otherwise, a filter can be installed to catch environmental particulates before they reach the coil. If a filter is used, appropriate cleaning and replacement frequency will depend on the operating environment.

There are three common filer types and each is designed for a certain environment. Metal filters excel in oily environments, lint filters (as the name implies) are intended for settings with an abundance of lint in the air, and foam filters are effective in exceptionally dusty environments.

As with most devices, air-conditioners and filter fans may need general maintenance to ensure consistently high levels of performance and efficiency.

Air-to-water heat exchangers
Air-to-water heat exchangers can be used in harsher environments than filter fans and, like air-conditioners, can cool components in an enclosure to temperatures below ambient conditions.

Such heat exchangers operate in conjunction with a chilled water supply. The chilled water runs though a coil in the heat exchanger and an internal fan blows air across the coil. Heat is transferred from inside the enclosure to the water, which carries it away to the chiller where the water is cooled and recirculated.

Air-to-water heat exchangers require very little energy to operate and are considered to be a low-maintenance, highly efficient climate control solution.

Many factories have a chilled water supply for cooling industrial processes such as metal and plastic forming.

Industrial chiller systems are generally large and are and vital to plant operations. These systems are intrinsically efficient due to economy of scale. Generally speaking, the larger a system is, the more efficient it is.

To get the most effective and efficient cooling from a chilled water system, the piping system should be insulated and not run through extremely hot areas. It is also important to install the chiller in a place that doesn’t expose it to excessive heat from ovens or furnaces.

Air-conditioners and the cooling coefficient
To precisely specify an air-conditioner for an application it is necessary to consider the amount of heat to be removed from the enclosure and how much energy is needed.

For residential air-conditioning systems, this determination is made using the seasonal energy efficiency ratio, or SEER, rating. Unlike the units found in residential settings, industrial air-conditioners typically operate 24 hours a day all year.

In the case of industrial air-conditioners, a similar measure of efficiency is the cooling coefficient – a ratio calculated by dividing the amount of cooling capacity by the amount of power consumption.

This calculation is made at a particular internal and ambient temperature (typically 95°F for both). The rating changes at different temperatures, allowing users to compare similar equipment from different manufacturers.

Conclusion
Creating effective and energy-efficient climate control for industrial applications consists of three main phases: design, installation and operation.

During the design phase, the overall panel layout, heat calculations and climate control selection should be completed. When laying out the panel, care should be taken to ensure adequate airflow in the enclosure.

The amount of cooling needed and the enclosure environment are crucial factors in selecting the type and size of the cooling solution.

The design phase will develop a large portion of the installation plan simply by virtue of its results. Attention to detail is crucial at this stage and care must be taken to properly install components and climate control products in accordance with the design plan.

Checking enclosure seals and other possible trouble spots that could jeopardise the success of the application is recommended at this point.

Once operational, climate control devices and other components should be monitored for performance. Regular maintenance should be performed to extend the life of integrated parts and keep energy efficiency as close to desired levels as possible.