3203 -- Prediction of Condensation and Frosting Limits in Rotary Wheels for Heat Recovery in Buildings

Rotary heat exchangers in air handling systems, particul arly those with hygroscopic rotors, can be operated at essential lower outdoor temperature than static heat exchangers without any need for defrosting. The reason for rotary heat exchangerstarting to frost at lower outdoor temperatures than static heat exchangers is proved to be the moisture transfer in the rotor. The supply air temperature limit presented here for frosting as well as excess water is calculated by a numerical method. The frosting-defrosting process is also discussed.