LINK TO THE ORIGINAL PAGE  CACHED IMAGE 22/11/2007  SAFE FOOD PACKAGING PORTAL 
QSPRMS WEBSERVER
THE CURRENT APPLICATION IS CONNECTED WITH THE EU/FP6/MIGRESIVE PROJECT


NOTATIONS 
The optimized finite volume discretization scheme is decribed here. Additionnaly, an introduction to finite volume methods can be found in Wikipedia.
NAME  DESCRIPTION 

_F or layer 0

food or food simulant 
_Pi

layer i of plastics or polymer (layer 1 is in contact with F) 
_FP 
ratio in F and in P 
M

migrant or diffusant 
0

initial 
INPUTS 
NAME  PHYSICAL PROPERTY / UNITS / MAIN ASSUMPTION / SAFE VALUE 

l_Pi  thickness of the layer i [ SI unit = m)]  ONE
SINGLE SIDE CONTACT No safe value (must be measured) 
L_FP  Overall volume dilution factor [SI unit: m³/m³)]  NO SIDE EFFECT (1D TRANSPORT) = volume F / volume of P Be avare that a mass dilution factor is used for monolayers but it not practical here for computation. No safe value (must be measured) >>3D»1D approximations 
rho_  density [SI unit: (kg/m³)  since ratios of density are used, other units are also possible]
 NB: k_ and rho ARE USED AS k_/rho_ If your concentrations are expressed in mass/mass (usual case), you must assign realistic densities to achieve accurate results.. No safe value (must be measured) 
k_F k_Pi 
phenomenological coefficient (Henry like coefficient such that the partition coefficient between i and j is
K_ij = kj /ki [SI unit: (kgM/kgj)/(kgM/kgi)]
DESORPTION EQUILIBRIUM OBEYS TO
HENRY's LAW This formulation converts concentrations into dimensionless partial pressures, pi=ki·Ci, which are continuous between materials. The equilibrium condition corresponds to uniform pi values. Safe choice = k_Pi>1000.k_F (almost complete extraction at equilibrium) >>How to handle uncertainty on k values 
D_Pi  diffusion coefficient in Pi [SI unit: m²/s] 
THE FOOD/SIMULANT DOES NOT INTERACT WITH THE POLYMER Safety value = must be [over]estimated or measured at a temperature higher than the conditions of use. For an overestimate, use: Piringer Calculator 
Bi  dimensionless mass Biot number [no unit]  EXTERNAL
MASS TRANSFER RESISTANCE DUE TO FOOD TEXTURE/ABSENCE OF STIRRING/MASS TRANSFER IN FOOD Bi=h.D_iref·rho_iref/(k_iref·l_iref) with iref layer with maximal transport resistance [(k_i·l_i)/(D_i·rho_i)] NB: The internal solver use a dimensionless formulation based on the layer with a maximum transport resistance. Safety value = 1000 (almost no external mass transfer resistance) 
C0_Pi  initial concentration in Pi [SI unit: kgM/kgP] 
ASSUMES AN HOMOEGENOUS AND UNIFORM INITIAL CONCENTRATION IN THE LAYER _Pi Safety value = 5000 ppm >>maximum recommended concentrations 
t  contact time [SI unit s]  NO
REACTION AND NO MASS LOSSES DURING DESORPTION Default value = 10 days (use the maximum shelf life combined with the maximum storage temperature) 
PARAMETER FORM 
©2007 by INRA\Olivier Vitrac
» Search strong D overestimates 
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