For Nafion™ dryers, the initial rate of water absorption roughly doubles for each 10°C increase in operating temperature. An elevated operating temperature will increase the initial rate of water removal, and the dryer will come to a final equilibrium dew point faster. However, the ultimate dew point achievable is dependent on the operating temperature – and the lower, the better, which is what we have observed.
Nafion™ is mostly an inert fluorocarbon polymer. Scattered through the fluorocarbon matrix are ionic channels consisting of sulfonic acid groups (hence the name ionomer). These ionic channels extend from the internal surface of the tubing to the external surface. The sulfonic acid groups very readily bind water in a reversible reaction as water-of-hydration. Once bound to the sulfonic acid groups at the internal surface of the tubing, water molecules very quickly pass along the ionic channel to the external surface of the tubing, where the water perevaporates (assuming the water vapor pressure at the external surface is lower than at the internal surface). This binding of water as water-of-hydration follows First Order reaction kinetics, so the rate of reaction is proportional to temperature.