Thermal and Fluid Transport

Form of energy expressed as Watts W

Amount of thermal energy per unit area that a body or substance gives off or absorbs expressed in Kelvins K

Heat travels in the direction of decreasing temperature

• Heat quantity that flows through a cube with 1m edge length in 1h by temp. difference of 1K (W/mK)

• Higher density leads to higher conductivity

• Conductivity is higher parallel than perpendicular to fiber grain

• Thermal conductivity of air is the lowest —> water —> brick —> concrete —> wood

• The higher the moisture content the higher the thermal conductivity

• Heat quantity that is needed to increase the temperature of 1kg of a material by 1K

• 4x so viel für Wasser als für Holz

• Higher MC —> Higher specific heat capacity; no influence of density

• Rate at which heat spreads through a material from its hot end to its cold end

• a=thermal conductivity/ (specific heat capacity * density)

• Higher moisture content —> lower a

• Higher density —> lower a

• a_w = length change / (original length * temp diff)

• Materials increase or shrink with temperature

• Length after increase:

• Thermal expansion tangential > radial > parallel

• Act as thermal insulator because it has higher density —> E modulus is higer

• The higher the temperatrue the lower the E modulus

• The higher the moisture content the steeper the curve down

Adsoption —> Diffusion —> Desoption in pits + bound water diffusion

• Between Hemicellulose and Lignin

• Temperature humidity regulaization in rooms

• Wood releases heat if water is bound —> releases water if heated