Abstract
This thesis describes the heating rate of a small liquid droplet in a develop-
ing boundary layer wherein the boundary layer thickness scales with the droplet
radius. Surface tension modifies the nature of thermal and hydrodynamic bound-
ary layer development, and consequently the droplet heating rate. A physical and
mathematical description precedes a reduction of the complete problem to droplet
heat transfer in an analogy to Stokes' first problem, which is numerically solved
by means of the Lagrangian volume of fluid methodology.
For Reynolds numbers of order one, the dispersed phase Prandtl number sig-
nificantly influences the droplet heating rate only in the transient period when the
thermal boundary layer first reaches the droplet surface. As the dispersed phase
Prandtl number increases, so does the duration of the transient. At later times,
when the the droplet becomes fully engulfed by the boundary layer, the heating
rate becomes a function of only the constant heat flux boundary condition. This
characteristic holds for all Péclet and Weber numbers, but the spatial behavior of
the droplet differs for small and large Péclet and Weber numbers.
Simulation results allow for the development of a predictive tool for the boiling
entry length of dilute systems in channel flow. The tool relies on an assumption
of temperature equivalency between the droplet and the thermal boundary layer
evaluated in absence of the dispersed phase, which is supported by the computa-
tional results. Solutions for plug and fully developed flow do not differ appreciably,
suggesting a precise description of the fluid mechanics is not necessary for an ap-
proximation of the boiling entry length. Future experimental work is required to
validate the predictive models derived in this thesis.
Users
Please
log in to take part in the discussion (add own reviews or comments).