Material moisture

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The material moisture (also solid moisture ) indicates the amount of free water contained in a solid .

General

The uptake of water is referred to as absorption or adsorption and the release as desorption . The two processes always occur simultaneously, the totality of the process is called sorption . Each material has very characteristic properties in this regard; so-called sorption isotherms are used to represent these .

Types of binding of the water in the solid

The water can be bound in the solid in different ways :

The chemically bound water is generally not of interest for the material moisture, as it does not count as free water . If chemically bound water is expelled from the material, this is associated with the destruction of the material.

Chemically bound water or the water resulting from the oxidation of hydrogen atoms is of interest if the material is used for combustion and the resulting water vapor affects the calorific value .

Humidity values

If the anhydrous mass is used as a reference value, the humidity can be more than 100% (for example in the case of wood moisture ), if the moist mass is used as a reference value, the humidity is less than 100%. This can lead to confusion when making comparisons.

The material moisture can be represented by various parameters. The most important are listed below:

Moisture content or water content
is the ratio of the mass of the water contained in the substance to the mass of the anhydrous substance

Formula:

Moisture content or water content
is the ratio of the mass of the water contained in the substance to the total mass of the substance

Formula:

Volume-related moisture content
is the ratio of the volume of the water contained in the substance to the volume of the anhydrous substance

Formula:

Volume-related moisture content
is the ratio of the volume of the water contained in the substance to the total volume of the substance

Formula:

Dry matter content
is the ratio of dry matter to total weight

Formula:

Absolute dryness

With

Measurement method

The material moisture can be determined with many moisture measuring methods. The most important are listed below:

Direct measurement methods:

Indirect measurement methods:

See also

swell

  • Klaus Kupfer: Material moisture measurement - basics, measuring methods, applications, standards. Renningen-Malmsheim: expert-Verlag, 1997, ISBN 3-8169-1359-8 , ( contact & study 513).

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