------ PIL real array; default=1.0; group 10, -
CINT(phi)....ratio of the bulk-to-interface transfer coefficient, for the variable indicated, to the reference value set by way of CFIPS.
CINT(phi) becomes active when two phases are present. It controls the value of the coefficient for diffusive transfer of the named variable between the bulk of the phase and its interface with the other phase.
Specifically, if CINT equals a constant other than GRND, the coefficient is equal to the product of CINT and the reference interphase friction coefficient per cell (which is determined by the setting of CFIPS).
If CINT is set equal to GRND, EARTH calls GROUP 10 of GROUND, where it expects to find an array of interphase-coefficient values set.
In this case, EARTH does N O T multiply the array values by the interphase friction coefficient.
For inter-phase processes, other than momentum transfer, it is frequently more practicable to set the diffusion coefficient in GROUP 10 of GROUND. This prevents unwanted multiplication by FIP.
The options supplied in GREX are as follows:
CINT(indvar) = GRND7 selects the transfer coefficent for INDVAR
equal to:
COI = RHO1*(ENUL*Nuss/(PRNDTL(indvar)*Dp))*As
where
Nuss, the Nusselt Number for a sphere
As, the surface area of the spheres in each cell
= 6*R2*Volume/Dp
Dp, sphere diameter
= CINH2C
The Nusselt Number for a sphere is taken from equation 5.25 on p 121 and
equations E
and F of Table 5.4 of 'Bubbles, Drops and Particles' by R Clift,
JR Grace and ME Weber.
The minimum slip velocity used in the Reynolds Number calculation is CINH1C.
The correlation for the transfer coefficient assumes bulk-to- bulk transfer, so the PHINTs for both phases should be left at their default value.
The CINT of the continuous or carrier phase should be set to GRND7, whereas the CINT for the dispersed phase should be set to a very large number, say 1.0E20 (see the entry on PHINT for an explanation).
In the case of heat transfer these settings are appropriate for constant and equal phase specific heats, i.e CP1=CP2. For constant and different phase specific heats, phase 1 must be taken as the continuous phase and PHINT(H1)=CP1/CP2 (again see the PHINT entry for an explanation).
In the case of heat-transfer, the correlations assume that the bulk values are temperatures, not enthalpies.
If the shadow volume fraction, RS, is SOLVEd, the diameter is taken as CINH2C*(R2/RS)**2.
STORE(NUSS) causes the Nusselt Number to be stored.
NOTE - If this option is used together with CFIPS = GRND7 or GRND8, the STORED diameter (STORE(SIZE)) will be used instead of CINH2C, and the STORED slip velocity (STORE(VREL)) will also be used if present.
CINT(indvar) = GRND8 selects the same form of transfer coefficient as GRND7, except
that the Nusselt Number is calculated from the Ranz-Marshall correlation,
Nu = 2 + 0.6*Pr**0.333*Re**0.5
See CFIPS and PHINT for further information.
wbs