Nusselt Numbers for Superhydrophobic Microchannels and Shrouded Longitudinal-Fin Heat Sinks
numbers that are relevant, but not limited, to thermal management of electronics are
computed in this thesis. The first two parts of the thesis compute Nusselt numbers for
liquid flow between parallel plates that are textured with ridges oriented parallel to
the flow. The configurations analyzed are both plates textured, and one plate textured
as such and the other one smoot... read moreh and adiabatic. The flow is laminar and the liquid is in
the Cassie state on the textured surface(s). The menisci are flat and adiabatic, and the
ridges are isothermal. First, axial conduction is neglected and the three-dimensional
developing temperature field is computed assuming a hydrodynamically developed flow,
i.e., the Graetz-Nusselt problem is solved. Then, the assumption of negligible axial
conduction is relaxed, i.e., the Extended Graetz-Nusselt problem is solved. Effects of
viscous dissipation and (uniform) volumetric heat generation are also considered. The
last two parts of the thesis are relevant to conjugate forced-convection heat transfer
through longitudinal-fin heat sinks. The third part computes and tabulates conjugate
Nusselt numbers for such heat sinks. Importantly, the analysis accounts for axial
conduction in the coolant and the fin. The flow is laminar, and
simultaneously-developing. The heat sink has an adiabatic shroud and its base is
isothermal. A conjugate boundary condition applies at the fin-coolant interface to
impose continuity of the temperature field and heat flux there. In the last part of the
thesis, an algorithm is presented to simultaneously optimize the geometry of an array of
such heat sinks utilizing the conjugate Nusselt number tabulations. The optimization
algorithm models heat transfer in a circuit pack using the Flow Network Modeling method.
The resulting system of nonlinear algebraic equations constitutes the implicit
constraints of the optimization problem. The objective function and the explicit
constraints of the optimization problem are user defined and arbitrary. The optimization
problem is iteratively solved using the Barrier Function method in conjunction with the
Trust Region method.
Thesis (Ph.D.)--Tufts University, 2018.
Submitted to the Dept. of Mechanical Engineering.
Advisor: Marc Hodes.
Committee: Erica Kemmerling, James Adler, and Alan Lyons.
Keyword: Mechanical engineering.read less