To improve wettability of a heat transfer tube or a heat transfer plate by shortening an interval for dropping a liquid droplet on the tube or the plate, and water-repellent treating a surface of a scattering tube for reducing a size of the droplet in a falling liquid film type heat exchanger used as an absorber or an evaporator of an absorption chilled and hot water generator.
A scattering tube 10 is formed in a tray type, and a liquid flowing through the tube 10 is dropped from a plurality of holes opened at its lower side area. When the falling liquid film type heat exchanger is, for example, an absorber, the liquid dropped from the tube 10 is absorption liquid (e.g. lithium bromide aqueous solution). In this case, a surface of the tube 10 is water-repellent treated by a method of covering the surface of the tube 10 with a poor water wettability material. Meanwhile, a plurality of heat transfer tubes 12 are disposed under the tube 10. The tubes 12 are narrowed at a dropping interval of the droplets D dropped from the water-repellent treated tube 10 to uniformly fall the droplets D to the surface of the each tube 12, thereby improving its wettability.