July 2, 2017
Cooling towers are used to provide cooled water for air-conditioning, manufacturing, and electric power generation. They were originally invented to recycle water that would otherwise be wasted, and today they save about 98% of the water that’s run through them. Cooling towers have a significant positive effect both on the environment (in the form of saving water and energy) and on the bottom lines of companies that use them.
If you’re considering buying cooling towers, there are three things that you should know about them in order to make the best decision for your individual situation. There are pros and cons to each, so you’ll need to evaluate what matters most to you.
There are two main types of cooling towers: natural draft and mechanical draft. The key practical differences between the two are the lifetime cost and where you can put them.
This type uses natural convection to circulate air inside the tower and cool the water. Warm, moist air rises above dry, cooler air, creating a constant air flow. Because these towers take advantage of natural processes, they’re cheaper to run, but they must be located outdoors.
This type uses mechanical methods to circulate air inside the tower via propeller fans or centrifugal fans. These towers are more flexible than natural draft towers. They can be placed inside a building, and the flow of air can be regulated. The disadvantage of these towers is that they’re more expensive to operate.
Cooling towers can have three different types of air flow configurations: counter-flow, cross-flow, and hyperbolic. Each has its own advantages.
In a counter-flow configuration, the air flows vertically upward, counter to falling water. To achieve this action, the tower uses a pressurized, pipe spray system to spray water onto the top of the fill. This configuration makes for towers with a smaller footprint, with even air distribution through the fill.
In a cross-flow configuration, the water flows vertically down through the fill while the air flows horizontally across the falling water. Because this type utilizes gravity, the air doesn’t need to go through a distribution system. This means a lower initial cost and lower operating costs, but it typically has a larger footprint.
Hyperbolic configurations use a chimney stacking technique that allows the cooler, outside air to push the damp, warmer air inside the tower. Water sprays over fill in the bottom of the tower and is cooled by upward-flowing air. This type requires a minimal amount of resources while efficiently managing large-scale tasks. But they’re not effective for smaller quantities of water.
The fan’s drive type is easily overlooked, but there’s a big difference in the lifetime costs of each, so it’s something to consider. Three types are most commonly used: belt, gear, and direct.
This type has the lowest initial cost, but because belts wear out quickly and new belts have to be adjusted, bearings maintained, pulleys replaced, etc., the maintenance on this type runs the lifetime cost up.
Gear drives require less maintenance than belt drives, but they do need to have oil levels checked and changed. The coupling and shaft extensions will need to be regularly inspected as well.
These drives are very efficient, and they lower vibration and system noise. They don’t require much maintenance at all, so they’re the best buy long term.
The best type of tower will be determined by what you’re using the towers for and your individual situation. If you’re not sure which type of cooling tower you should choose, we’re happy to talk with you. Give us a call at 864.249.0943!
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