Question: My compressed air dryer is rated at 100° F inlet air temperature. What will happen if the air temperature is lower than this?
Answer: Having the air temperature lower than the dryer rating is a good thing.
Actually, dryers are commonly rated at 100° F inlet temperature, 100 psi and 100° F ambient temperature. You should look up your rating and make sure your system isn’t operating outside of these limits.
Heat and pressure effect the operation of the dryer. If the pressure is lower than the dryer rating, higher velocities develop within the dryer, making it less effective in removing moisture. If the temperature of the air inlet is too hot, there will be too much moisture to process, the amount of water vapor in the air doubles for every 20° increase in temperature — so the dryer may be overwhelmed. And at higher ambient temperatures, it is hard for refrigerated dryers to expel the heat generated by internal water condensation, making the dryer effectively smaller than its nameplate rating.
If the temperatures are lower than rating, then the dryer then has lower moisture loading, this is very much desired, and will go a long way to ensure you have good air quality. And, if you have a cycling refrigerated dryer, or a desiccant dryer with dew point control, the lower moisture loading will actually reduce the energy cost of the dryer operation. Then it will pay to keep your dryer nice and cool.