Code Manual for CONTAIN 2.0 - Federation of American Scientists

In these equations, N~~is the drop Reynolds number, N%is the Prandtl number, and N~Cis the
Schmidt number. Note that the Sherwood number is determined from Equation (12-19) by using an
analogy between heat transfer and mass transfer [Kre58]:
N~h = NNU{Npr” ‘SC}
12.4 Heat Exchamzer Models
(12-21)
The containment spray system typically uses a heat exchanger to cool the liquid water recirculated
from the sump pool (Figure 12-2) to the containment spray nozzles. There is only one combination
of components in which a heat exchanger can appear, and this is along with a spray, tank, and pump.
An example of such a system is given in Section 14.3.3.4.
One of four heat exchanger models can be used. These correspond to (a) a single-pass shell and Utube
geometry, (b) across-flow geometry with hot-side tubes and cold-side shell, (c) a counterflow
geometry, and (d) a parallel flow geometry. These models are specified in the HEX input block (see
Section 14.3.3.5) using the keywords SHELL, CROSS, COUNTER, and PARALLEL, respectively.
The heat exchangers are depicted in Figure 12-7. A nonmechanistic model with a constant userspecified
hot-side temperature drop is also available by specification of USER and the temperature
drop across the hot side “hxdelt.” Throughout this section, the terminology in Figure 12-8 will be
used.
The basis for modeling the four heat exchangers illustrated in Figure 12-7 is obtained from
Reference Kay64. The important quantity to model for a heat exchanger is the hot-side outlet
temperature. In this formulation it is expressed as a function of an effectiveness factor, the inlet hotand
cold-side temperatures, the hot- and cold-side mass flow rates, and the liquid heat capacity. The
hot-side flow rate and temperature are determined from the pump capacity and pool thermal
conditions, respectively. The cold-side flow rate and temperature are input parameters “hxclmd” and
“hxticl.” The efficiency depends upon the heat exchanger type, effective surface are%and the overall
heat transfer coefficient, which correspond to the input parameters “otype,” “hxarea,” and “hxcoef,”
respectively. Because heat exchanger designs vary greatly, no default parameters are provided.
The heat exchanger modeling is based on an effectiveness factor E defined as
caph(Th.i - ‘b)
capmi.(Th,i - ‘.,i)
capc(Tc,o - ‘c,i)
capmi.(Th,i - ‘qi )
(12-22)
R O 12 19 6/30/97