Modern Drying Technology

Recommended Notation

• Alternative symbols are given in brackets
• Vectors are denoted by bold symbols, a single bar, an arrow or an index (e.g., index: i)
• Tensors are denoted by bold symbols, a double bar or a double index (e.g., index: i, j)
• Multiple subscripts should be separated by colon (e.g., : density of dry particle)

A surface area m−2 a w water activity – B nucleation rate kg−1 m−1 s−1 b breakage function m−3 C (K) constant or coefficient various c specific heat capacity J kg−1K−1 D equipment diameter m D (δ) diffusion coefficient m2 s−1 d diameter or size of solids m E energy J F mass flux function – volumetric flow rate m−3s−1 f relative (normalized) drying rate – f multidimensional number density – G shear function or modulus Pa G growth rate kg s−1 g acceleration due to gravity m s−2 H height m H enthalpy J H Heaviside step function – h specific enthalpy (dry basis) J kg−1 h (α) heat-transfer coefficient W m−2 K−1 molar enthalpy J mol−1 specific enthalpy of evaporation J kg−1 I total number of intervals – J numerical flux function – J Jacobian matrix various mass flux, drying rate kg m−2 s−1 K dilatation function or bulk modulus Pa k (β) mass transfer coefficient m s−1 L length m M (m) mass kg (M, M N) molecular mass kg kmol−1 mass flow rate kg s−1 mass flux, drying rate kg m−2 s−1 volumetric rate of evaporation kg m−3 s−1 N number – N molar amount mol molar flow rate mol s−1 n molar density, molar concentration mol m−3 n number density m−3 n outward normal unit vector molar flux mol m−2 s−1 P power W P total pressure kg m−1 s−2 p partial pressure/vapor pressure of component kg m−1 s−2 heat flow rate W heat flux W m−2 R equipment radius m R individual gas constant J kg−1 K−1 universal gas constant J kmol−1 K−1 r radial coordinate m r pore (throat) radius m S saturation – S selection function s−1 s boundary-layer thickness m T temperature K,°C t time s u velocity, usually in z -direction m s−1 u displacement m V volume, averaging volume m3 volumetric flow rate m3 s−1 v specific volume m3 kg−1 v general velocity, velocity in x -direction m s−1 W weight force N mass flow rate kg s−1 w velocity, usually in y -direction m s−1 X solids moisture content (dry basis) – x mass fraction in liquid phase – x particle volume in population balances m3 x general Eulerian coordinate, coordinate (usually lateral) m x 0 general Lagrangian coordinate m molar fraction in liquid phase – Y gas moisture content (dry basis) – y spatial coordinate (usually lateral) m y (ω) mass fraction in gas phase – molar fraction in gas phase – z spatial coordinate (usually axial) m Operators gradient operator divergence operator Δ difference operator Greek letters α (h) heat-transfer coefficient W m−2 K−1 β (k) mass-transfer coefficient m s−1 β aggregation kernel s−1 δ Dirac-delta distribution δ (D) diffusion coefficient m2 s−1 voidage – emissivity – small-scale parameter for periodic media – strain – η efficiency – θ angle, angular coordinate rad κ thermal diffusivity m2 s−1 λ thermal...