Supporting downstream treatment
Cooler inlet air generally reduces the load on the dryer and allows some water to be removed earlier. However, an aftercooler alone does not establish a low dew point as complete drying does. Outlet temperature depends on flow rate, heat exchanger fouling and coolant temperature.
Check both sides of the heat exchanger
Dirty fins, insufficient air supply or restricted water circulation impair cooling. For water cooling, check the required flow, temperature difference and water quality against the documentation. Downstream of the cooler, there must be a working water separation and drain; otherwise the liquid passes downstream.
What to check in practice
- Measure the air temperature before and after the cooler and the coolant temperature.
- Check heat exchanger cleanliness and the specified flow rates.
- Check condensate drainage before looking for a fault in the dryer itself.
Example scenario
The dryer receives air at 50 °C instead of the design temperature of 35 °C. It may then be unable to handle the original flow at the required dew point. Before buying a larger dryer, check the aftercooler for fouling and verify its cooling conditions.
What to watch out for
- Assuming every cooler has the same outlet temperature.
- Treating water formation as a cooling fault when it is part of the cooling process.
- Confusing cooling with removing all water vapour.
Can the heat from aftercooling be used?
It can be, provided its temperature level and quantity match the demand. Heat recovery must be assessed for the complete thermal system and must not restrict essential compressor cooling when there is no heat demand.