Water desorption behavior of desiccant rotor under microwave irradiation

Microwave heating is expected to be a novel regeneration method of desiccant rotor in desiccant humidity conditioner, because it has advantages of direct and rapid heating of material. In this study, desorption experiments were conducted by using the practical desiccant rotor coated with zeolite in the microwave power ranging from 200 to 800 W and desiccant rotor length of 60–180 mm. As a result, both desorption ratio in a desorption equilibrium and initial desorption rate were found to increase linearly with microwave power. Concerning the effect of rotor length, it was found that initial desorption rate and desorption ratio at 600 s also increased with rotor length. However, experimental desorption ratio in a desorption equilibrium was much lower than estimated value, which was calculated on the basis of change in relative humidity involved by temperature increase of rotor, and the deviation increased with microwave power and rotor length. From the temperature measurement in the rotor, a noticeable temperature distribution was observed in the radial and axial directions of rotor even though water desorption attained an equilibrium state. Consequently, it was indicated that nonuniform heating of the rotor mainly caused decrease in desorption ratio.

Research highlights
► Water desorption of zeolite desiccant rotor was conducted with microwave heating.
► Initial desorption rate and equilibrium ratio rose linearly with microwave power.
► Initial desorption rate and equilibrium ratio increased with rotor length.
► Experimental desorption ratio was much lower than theoretically estimated value.
► A big temperature distribution existed in the radial and axial directions of rotor.