Code Manual for CONTAIN 2.0 - Federation of American Scientists

exit losses and other fictional losses. Section 4.4.1 gives additional discussion regarding the flow
loss coefficient.
The atmosphere mass conservation equation for a cell is given in Table 4-3. The equation in this
table takes into account (a) the flow of principal fluids into a cell from other cells, (b) flow out of
the cell to other cells, (c) pool-gas exchange terms from boiling and equilibration of gas injected into
the cell below the coolant pool surface, and (d) mass sources and sinks from processes modeled
explicitly outside of the flow solver.
The energy conservation equation for the atmosphere of a cell is given in Table 4-4. The equation
includes volume displacement work, work associated with gravity, and the energy from sources and
sinks within a cell. Note that the kinetic energy term is neglected in the energy equation, because
the flow velocities must be on the order of the sound speed in order for the kinetic energy terms to
become. @er85b] Volume displacement work terms are implicitly included in the equation through
the use of the flow specific enthalpy. Similarly, volume displacement work from explicit processes
is taken into account through use of the enthalpy to define the q terms. The gravitational work terms
are explicitly displayed. The elevations used in the work terms are dictated by the fact that the
enthalpy fluxes are referenced to the gas center of elevation for transfers from an atmosphere and
to the pool surface for transfers from a pool.
The coolant pool mass conservation equation is similarly given in Table 4-5, and the energy
conservation equation for a pool is given in Table 4-6.
The thermodynamic state equations for the atmosphere and pool given in Table 4-7. From the
component masses and the total internal energy of the atmosphere and pool, the thermodynamic state
calculation determines the temperature, pressure, enthalpy, and saturation condition of the
atmosphere and the temperature of the pool in the cell.
From the given internal energy and the component masses, it is necessary to invert the internal
energy function to obtain the temperature. This is done iteratively for both the atmosphere and pool.
An initial guess for the temperature close to the expected temperature is made. In practice, these fust
estimates are chosen to be close to the last known temperature. The internal energy for ttis
temperature is then calculated and compared to the total energy that should be present. If the
comparison is not acceptable, a new temperature is selected, and the iterative process is continued
until acceptable convergence occurs. In the implicit method, if more than 50 iterations are required,
the calculation simply will abort. In the explicit (Runge-Kutta) method, if more than 30 iterations
are required, a message warning of nonconvergence is given. One should note that the inversion
routines are extremely robust. Nonconvergence that is not the result of too large a timestep is usually
a symptom of a ca.lculational fault outside the solver, such as a negative mass for the condensable
gas. ‘The code does check for negative masses,
performed prior to this check. Another potential
user-defined materials for the gas phase components
thermodynamic laws are specified.
but intermediate calculations are sometimes
cause of nonconvergence may be the use of
of the atmosphere, particularly if data violating
Rev O 445 6/30/97