Temporal tracking of the interface with mass transfer
phenomena
is very complex during the boiling process. In this paper, the physics
of two-phase boiling phenomena of water around the heated surface
of a helically coiled tube at a critical pressure (P
sat = 21.9 MPa) has been predicted numerically. Such high-pressure
systems are usually observed in boiling water reactors (BWRs). The
boiling heat transfer characteristics were studied on eight different
helically coiled heated surfaces with varying curvature ratios (δ)
from 0 to 7.16 and coiled tube orientations (vertical and horizontal)
at a degree of superheat (ΔT) of 10 K. The
vapor bubble dynamics, i.e., bubble merging, sliding over the surface,
and departure, have been studied over the heated helical surface.
Although having vapor blanketing over the surface, the coil having
zero curvature (straight tube) possesses a higher velocity and generation
of vapor phase among all considered cases. The orthogonality of the
surface normal and gravitation force makes the vapor move faster.
Thus, the H1 (horizontally oriented tube) configuration possesses
3.79 times higher average velocity than the H4 coiled tube configuration.
Vertical configuration, i.e., a helically coiled tube (V4) with a
curvature ratio (δ = 0) produced 4.4 times higher vapor than
that produced by a horizontally oriented helically coiled (H4) configuration.
Thus, curvature and orientation play a critical role in fluid dynamics,
heat transfer, and vapor volume production.