Keywords
Freeze-drying; Lyophilization; Mathematical model; Multi-dimension; Food drying
Nomenclature
AextAext
external surface area of product contacting to ambience (m2)
AbtmAbtm
surface area of frozen layer contacting the sample tray (m2)
AiAi
effective surface area receiving radiative heat (m2)
AsAs
surface area of sublimation interface (m2)
dpdp
mean pore diameter (m)
eded
dried layer thickness at the product bottom (m)
DADA
effective diffusion coefficient in dried layer (m2/s)
DkDk
Knudsen diffusion coefficient (m2/s)
ΔHΔH
latent heat of sublimation (J/kg)
hbtmhbtm
overall heat transfer coefficient at the frozen bottom of the product (W/m2 K)
hshhsh
heat transfer coefficient at the bottom of the product (W/m2 K)
hR1–4hR1–4
radiative heat transfer coefficient (W/ K)
KccKcc
mass transfer coefficient from product to condenser (m3/s)
m
mass of ice fraction (kg)
MWMW
molecular weight of water (kg/mol)
PcPc
pressure at condenser surface (Pa)
PmeasPmeas
pressure measured by pressure gauge (Pa)
PsPs
pressure at sublimation interface (Pa)
QdryQdry
heat flow through dried layer (W)
QiceQice
heat flow through frozen layer (W)
QradQrad
radiative heat to product (W)
QRadsh
radiative heat to shelf (basket) (W)
QshQsh
heat flow from shelf (basket) to product (W)
QsQs
heat consumption at sublimation interface (W)
R
ideal gas constant (J mol/K)
t
time (s)
TbtmTbtm
temperature of product bottom (K)
TchTch
temperature of chamber wall (K)
TcTc
temperature of condenser (K)
TextText
temperature of product external surface (K)
ThTh
temperature of electric heater (K)
TpTp
temperature of product (during ice sublimation test) (K)
TshTsh
temperature of shelf (basket) (K)
TsTs
temperature at sublimation interface (K)
VffVff
volume of frozen fraction (m3)
Greek letters
ε
porosity (–)
εiεi
emissivity (–)
σ
Stefan–Bolzmann constant (J/s m2 K4)
λdryλdry
thermal conductivity of dried layer (W/m K)
λiceλice
thermal conductivity of frozen layer (W/m K)
η
conversion applied to coefficients obtained from ice sublimation test (–)
τ
tortuosity (–)