The difference between air and water aftercoolers

Aftercoolers are among the most effective heat exchange systems available, although finding the right type of aftercooler for your air compressor can be challenging. There are many variables to consider, including cooling efficiency, operating costs, and the amount of space available in your workspace. One type of air cooled aftercooler may be even more appropriate than the other, depending on your industry. If you’re having trouble finding the right aftercooler for you, we’re here to help. This guide describes the difference between air and water aftercoolers and the advantages and disadvantages of each. 

Aftercoolers

Air-cooled aftercoolers use blown air and a series of coils to lower the temperature of the compressed air and remove moisture. Compressed air moves through the aftercooler coils and a motor-driven fan forces air over the coils to displace heat. As the air cools, the water vapor condenses and collects in the drain valve. A belt guard air aftercooler is a special type of aftercooler that mounts directly to the compressor belt guard. Instead of using its fan, it uses air that comes out of the compressor belt system to cool the compressed air. This is especially useful if space is an issue. Without a large fan of its own, the belt guard unit is small and thin, taking up hardly any additional space near the belt guard. An advantage of air aftercoolers is the amount of cooling they can provide. While water aftercoolers generally cool compressed air to 10F – 15F, air aftercoolers can cool to 15F – 20 F depending on the size and materials used. 

Additionally, air aftercoolers generally require less maintenance than water aftercoolers. Sometimes problems can arise in water coolers due to thermal or chemical contamination of the cooling fluid. Pollution is not a problem for air coolers and air quality has minimal effect on their efficiency. However, if you are concerned about noise, know that aftercoolers tend to be louder than water-cooled units, especially larger units with industrial fans. And while there are low-noise units available, they tend to sacrifice energy efficiency for noise reduction. Another area to consider is protection from cold weather. Because water vapor condenses into a high pour point liquid, it could freeze before draining the valve. To avoid problems, consider an aftercooler with special weather protection features if the unit is located in a cold area. 

Water coolers

Water-cooled aftercoolers, on the other hand, use water to cool the compressed air. The shell-and-tube / aftercooler heat exchanger is the most common. In this system, hot air flows through the aftercooler tubes and cold water flows around the tubes in the opposite direction. As the compressed air cools, the water vapor liquefies and moisture collects in the aftercooler drain valve. Because water has little seasonal temperature fluctuation and is relatively resistant to changes in temperature, it effectively extracts heat from compressed air without heating. Very little electricity is required in the aftercooler process, reducing electrically generated heat while lowering your electricity bill. The most significant advantage of water aftercoolers is their heat and pressure capabilities. While most air aftercoolers can handle up to 350 F compressed air and up to 250 psi pressure, water-cooled units can be exposed to operating temperatures up to 450 F and pressures up to 435 psi. If your operation runs at a higher temperature, aftercoolers are an excellent choice. However, water aftercoolers also have some drawbacks. A large volume of water is needed to reduce the temperature of the compressed air effectively. 

Typical industrial plants can use about 10 million gallons of cooling water per year. By comparison, facilities like steel mills or paper mills can use up to 550 million gallons of water per year. So even though you can save on electricity, your water bill is likely to be higher. In addition, the resistance of water to changes in temperature can sometimes be counterproductive. Although the circumstance is rare, if the water becomes too hot or too cold, it can take a long time to return to its functional temperature. 

The benefits of having an aftercooler for your air compressor

Adding an aftercooler to your air compressor protects the compressor and protects many other areas of your operation from the damaging effects of excess heat and humidity. Hot air contains a lot of moisture, which leads to rust, scale build-up, and even freezing problems over time. By reducing the amount of water vapor in the compressed air, the aftercooler keeps equipment running smoothly. The heat released by air compressors can also damage sealing materials and reduce lubrication effectiveness over time. A compressed air aftercooler helps prevent this by cooling the pipes before the heat reaches the sealant. An aftercooler can even save you other equipment costs like venturi air blowers do. Because the aftercooler treats the air before it reaches the dryer, it reduces the amount of stress on the dryer. This allows you to choose a smaller drying unit, saving you money and space. Hot compressed air hoses and pipes can also be a safety concern. Workers can accidentally get burned if they brush against a hot air hose, and high-temperature compressed airlines can even pose a fire hazard if a flammable object gets too close. By rapidly cooling the air with an aftercooler, you greatly reduce that risk.