| Summary: | 碩士 === 國立臺灣大學 === 機械工程學系 === 85 === This study investigates the transient solidification process of
pure water and binary NH4Cl solution in a rectangular cavity
with upper and lower adiabatic walls, and two vertical
isothermal walls. Holographic interferometry was used to
visualize the flow field, and in the experiment of the binary
NH4Cl solution solidification, shadowgraph method was also used.
According to the result of the experiment, the process of
freezing pure water consists of 4 parts:(1) the development of
supercooling zone, (2)the growth of dendritic ice, (3)the
remelting of dendritic ice, (4)the growth of hard ice. Each part
is affected deeply by density inversion. In the initial period
of solidification, the impact from supercooling is deeper, and
the amount of dendritic ice in the flow would directly influence
the development of the solid-liquied interface. In the later
period, the iConcerning the solidification of the binary NH4Cl
solution, its process in eutectic composition is similar with
that of pure substance. In hypoeutectic solution, both of
double-diffusive layer and remelting occur in the lower part of
the flow which is stable. On the other hand, in hypereutectic
solution, double-diffusive layer and remelting occur in the
upper part of the flow. The layer is ruined seriously, and the
flow is unstable. The uprising of wall temperature would offset
the occurrence of double-d
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