Removes ~70% of moisture by dropping discharge air from 250–350°F to within 15–20°F of cooling medium. Required ahead of any dryer.
Sizing
- Approach temp: air-cooled = ambient + 15–20°F; water-cooled = cooling water + 10–15°F.
- Size to compressor full-load CFM; undersize = high inlet temp to dryer = poor dewpoint.
Preventive maintenance
- Air-cooled: clean fin pack quarterly, check fan motor and capacitor.
- Water-cooled: monitor delta-T across cooler, descale annually, check strainer.
- Always pipe to a moisture separator with auto-drain.
Troubleshooting
Hot air leaving aftercooler / dryer overloaded
Likely causes
- Dirty coil or scaled tubes
- Fan/water flow loss
- Ambient or cooling water too warm
Fix
Clean/descale, repair fan or water supply, add additional cooling.