Aktiebolaget Svenska Flaktfabriken

Erik Wrangel

Ove Strindehag

The transfer elements of the rotor of a regenerative heat and humidity exchanger are made of a non-hygroscopic material, such as aluminum, the surface of which is treated to form a hygroscopic layer thereon. This provides the benefits in humidity transfer previously obtained with all-hygroscopic transfer elements such as paper, cardboard or asbestos, without the danger of fire in the use of paper or cardboard or the danger to health in the use of asbestos. Preferably the transfer element is of metal on which a hygroscopic surface layer is formed by oxidizing the surface by pickling and/or heat treatment, and preferably the oxide layer is impregnated with a substance, e.g. lithium chloride, to render it more hygroscopic. Preferably also, the layer is made more porous by acid treatment prior to oxide formation, and acid treatment may be used after the pickling process to arrest the pickling reaction promptly.

Humidity and heat exchanger apparatus, and method for its manufacture

A surface layer is formed on transfer elements of the rotor of a humidity and heat exchanger rotor, the layer not only being hygroscopic to provide the desired humidity transfer, but also serving as a bonding agent or cement for holding the transfer elements together in the desired rotor configuration. A preferred layer uses as a bonding agent a solution of cellulose acetate or nitrate in acetone, and with lithium chloride dissolved therein to produce the hygroscopic effect.

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Jonkoping, Sweden

Erik Wrangel