Title:
An investigation of surface shape effects on near-field radiative transfer
An investigation of surface shape effects on near-field radiative transfer
Author(s)
Prussing, Keith F.
Advisor(s)
Cathcart, J. M.
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Abstract
It has been shown that the energy exchange between two objects can be
greatly enhanced when the separation between the objects is on the order
of the wavelength of thermal emission. The earliest theoretical and
computational work focused on simple planar and spherical geometries, or
they resorted to approximations that separated the object to outside of
the thermal wavelength \(\lambda_T = hc/(k_BT)\). Since those original
works, the study of near-field energy exchange has expanded to object
shapes that can be described by a separable coordinate system using a
spectral expansion of the dyadic Green function of the system. The
boundary element method has also been used to study arbitrary shapes in
thermal equilibrium. Application of these new expansion methods to
general shapes out of thermal equilibrium will facilitate in the
optimization of nanoscale structures.
A three step process is used to investigate the effects of object shape
on the total and directionality of the energy exchange between objects.
First, a general expression for the energy flux between the objects will
be formulated. Second, a computational method to evaluate the
expression will be implemented. Finally, the effects of varying the
surface geometry will be explored.
The computational results demonstrate that the total energy exchange
between two bodies is influenced by the surface shape of the objects
even when the surface areas are held constant. While the primary
increase over the classical blackbody energy exchange \(\sigma T^4 A\)
is primarily governed by separation of the surfaces, we show that the
view factors from classical far-field radiative transfer can be used to
predict the change in the total energy exchange from a reference
configuration at the same separation when the surface area of the two
objects is comparable. Additionally, we demonstrate that the spatial
distribution of the energy exchange can be localized into small spatial
region with a peak value increased over \SI{30}{\percent} by using two
objects with dramatically different projected areas.
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Date Issued
2015-05-19
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Text
Resource Subtype
Dissertation