To improve absorbing performance by lengthening a time of contact between refrigerant vapor and a liquid drop, and increasing to the utmost a concentration of an absorbent on the surface of the liquid drop where the refrigerant vapor comes into contact.

An intermediate tray 34 is provided at a predetermined space below a dray 22 on which an absorbent drops as a liquid drop, and liquid drops sprayed from an absorbent spraying means 21 are caught in the intermediate tray 34. Further, the absorbent is dropped as liquid drops from the intermediate tray 34 and caught in a lower intermediate tray 34, and dropped as liquid drops on a further lower intermediate tray 34. Thus, an effective height for absorption is divided to decrease a height susceptible to gravitational acceleration, a time required for dropping to the lowermost end as a whole is lengthened to increase a time of contact with the refrigerant vapor. After mutual mixing the liquid drops of the absorbent whose concentration at the drop surface is lowered due to the absorption of refrigerant vapor, they are dropped as liquid drops to increase the concentration of the absorbent on the drop surface.

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