Code Manual for CONTAIN 2.0 - Federation of American Scientists

follows the standard recommendations [Bir60] for dealing with such gas properties. Namely, the
boundary layer temperature T~~used for such properties is taken to be fixed at the arithmetic average ~
of the bulk temperature T~and the interface temperature Ti~,and the boundary layer composition is
taken to be fixed at the average of the bulk and interface values. Also, as discussed in Section
10.1.1.2, the interface temperature used in the heat and mass transfer coefficients is actually taken
to be the interface temperature calculated in the previous timestep for the surface in question.
For the example in Figure 10-7, both the molar fluxes (kgmole/m2-s)of noncondensable gas JnCand
condensable vapor J, passing through the interface are given by Reference C0181:
and
acne
Bv— + C~CvJ= JnC
ay
~ acv + CVVJ= Jv
‘*
(10-46)
(lo-47)
where D, is the boundary layer vapor diffusion coefficient (m*/s),evaluated as discussed in Section
10.2.1.1, CnCis the molar concentration of noncondensable gas (kgmole/m3), v, is the drift-flux
velocity of the bulk mixture toward the interface (m/s), and C, is the molar concentration of vapor
(kgmole/m3).
Since the total pressure P~= P,C+ P, is assumed constant in the diffusion process, it follows that
(10-48)
Furthermore, if one assumes that the diffusion takes place at a fixed boundary layer temperature T~~
then the ideal gas law implies that
acne acv
—= ——
ay @
Substituting Equation (10-49) into Equation (10-47) results in
acne
Jv = CVVJ- Dv —
@
Combining Equation (10-46) and Equation (10-50) to eliminate v, results in
(lo-49)
(10-50)
Rev, O 10-34 6/30/97