Page 191 - Thermal Hydraulics Aspects of Liquid Metal Cooled Nuclear Reactors

162 Thermal Hydraulics Aspects of Liquid Metal Cooled Nuclear Reactors

Fig. 4.4 Nusselt number from different correlations for convective heat transfer of liquid metals
in vertical bundles of heated rods (case with p/D¼1.3 and triangular lattice).

function of the Peclet number, obtained from the five different convective heat trans-
fer correlations for liquid metals in a vertical bundle of triangular lattice heated rods.

4.2 Hydrodynamic model for STH codes

Mathematically, there are two ways to address the concept of finite balance of a given
“extensive” variable:
l The Eulerian point of view in which the different properties of a fluid passing from a well-
defined “control volume” are evaluated. With this point of view, the fluid can enter or exit
from the “control volume” due to advection and diffusion phenomena.

Control Exchanges due to fluid motion (advection)
volume
Exchanges not due to fluid motion (diffusion)

l The Lagrangian point of view in which the different properties of a given “control mass” are
evaluated while evolving/moving into the system. With this point of view, no mass
exchanges can occur.