Moisture Content
Content of moisture in products like wood - wet and dry basis
Moisture content is the amount of water present in a moist sample of a product like wood, soil or similar. Moisture content can be be expressed on wet or dry basis.
Moisture Content on Dry Basis
Moisture content on dry basis is the mass of water to the mass of dry solid:
MCd = mh2o / md (1)
where
MCd = moisture content on dry basis
mh2o = mass of water (kg, lb)
md = mass of dry solid (kg, lb)
Moisture content on dry basis is commonly used in the timber industry. Note that it is common to multiply values with 100%.
Water Content on Wet Basis
Water content on wet basis is the mass of water to the mass of water and mass of solid:
MCw = mh2o / mw
= mh2o / mh2o + md (2)
where
MCw = moisture content on wet basis
mh2o = mass of water (kg, lb)
mw = total mass of moist - or wet - sample - mass of solid and mass of water (kg,lb)
Example - Water Content in Birch on Wet Basis
The density of air-dried seasoned dry Birch is 705 kg/m3 with 20% (0.2) water content. The amount of water per unit volume can be calculated by transforming (2) to
mh2o = mw MCw
= (705 kg/m3) (0.2)
= 141 kg/m3
The amount of solids can be calculated as
md = (705 kg/m3) (1 - 0.2)
= 564 kg/m3
Example - Moisture Content in Birch on Dry Basis
The density of air-dried seasoned dry Birch is 705 kg/m3 with 20% (0.2) moisture content. Equation (1) can be modified to
MCd = mh2o / (m - mh2o) (1b)
where
m = mass water and solid (kg, lb)
This equation can be transformed to
mh2o = MCd m / (1 + MCd ) (1c)
The moisture content per unit volume can be calculated as
mh2o = (0.2) (705 kg/m3) / (1 + (0.2))
= 117.5 kg/m3
The amount of solids can be calculated as
md = m - mh2o
= (705 kg/m3) - (117.5 kg/m3)
= 587.5 kg/m3
Moisture and Water Content Calculator
mass (kg, lb)
moisture/water content (%)
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