Air compressors create heat, and lots of it. If this heat is not properly removed, then problems will occur in a compressed air system. Over-temperature shutdowns and failed air dryers are common symptoms of improper cooling. It is important to choose your compressor cooling method wisely and to ensure whatever media you choose is suitable to maintain a good path to remove the heat of compression — and hopefully direct it to where the heat can be used for a useful purpose.
The most common method of cooling compressors uses ambient air, which is passed through or near the air-to-air and air-to-oil heat exchangers within the air compressor. This ambient air needs to be as clean and cool as possible, but not freezing, with the source selected so there is an unrestricted flow of filtered cooling air no less than the amount specified by the compressor manufacturer. The hot air that is produced by the compressor most often passes through ductwork, so as not to mix with the incoming air, this is good practice. Sometimes, in cool locations, a small amount of hot air is mixed with compressor room air to temper the room, to avoid needing to use heaters.
The other method used to cool compressors is some sort of liquid cooling supply, which could be water or a mixture of water and glycol, to ensure the coolant will not freeze when the compressor is located in cooler climates. Again, the medium in this case needs to be as clean and cool as possible. The photograph above shows what happens when an evaporative cooling system runs untreated, the minerals in the cooling water quickly contaminated the compressor cooler tube bundle causing over-temperature shutdown.
In all cases, care needs to be taken to ensure the conditions during the worst case scenario will not cause compressor or associated air dryer shutdown. Each heat exchanger has a CTD (cold temperature difference) that must be considered. For example, a heat exchanger with a 15° F CTD and 100° cooling medium temperature will produce 115° output when it is clean. Higher discharge temperatures will develop if the heat exchanger is clogged with debris. Because most air dryers are rated at 100° F, some sort of design measure will have to be taken to ensure temperature ratings will not be exceeded.
- Have the cooling system designed by a experienced engineering firm
- Make sure the cooling media stays clean
- Design the system to draw the coolest possible media, and capture the heated media so that it can be efficiently removed before mixing with the incoming media
- Do maintenance checks with an IR gun on your compressors and dryers to ensure there are no overheating conditions
- Where possible, use the heat for something useful