| Summary: | In the present study, a theoretical method for sphere-to-sphere radiative heat exchange is
implemented for silica, lithium fluoride, and arsenic triselenide nanospheres of equal and
unequal radii. The method is extended to approximate a sphere-to-plane geometric configuration
via an asymptotic method. The asymptotic method calls for an iterative process by which the
radiative exchange is continuously calculated up to convergence as the radii of one microsphere
is increased. These results are compared to previously published theoretical approximations and
experimental data.
A theoretical method for cylinder-to-cylinder radiative heat exchange is formulated. The
method utilizes a modified version of the numerical method for near-field sphere-to-sphere
radiative exchange. Modifications were made to the numerical procedure to make it applicable to
cylindrical geometry of nanorods. Nanorods investigated had length to diameter ratios of 3: I
and 7:1. The heat exchange of nanorods is plotted vs. gap to assess the impact of near-field
radiative transfer as gap decreases. Graphical results of energy vs. nanorod radii are also
presented. A nanorod-to-plane configuration is estimated utilizing a nanorod asymptotic
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method. The nanorod-to-nanorod method approximates a nanorod-to-plane geometric
configuration when one nanorod radii is held constant, and the second nanorod radii is iteratively
increased until the corresponding radiative exchange converges.
A theoretical method for cylinder-to-cylinder radiative heat exchange is formulated by
utilizing a sphere approximation method. The sphere approximation method calls for dividing
the cylinders into smaller connected spheres and applying a previously published numerical
method for near-field sphere-to-sphere radiative exchange. The overall radiative power
exchange is obtained by an additive ray tracing assumption. These results are compared to
results produced by a rigorous cylinder-to-cylinder radiative heat exchange method. The heat
exchange of nanorods is plotted vs. gap to assess the impact of near-field radiative transfer as
gap decreases. The unit sphere method is applied to nanorod configurations having length to
diameter ratios of 3: 1, 5: 1, 7: 1. Graphical results of energy vs. nanorod radii are presented. A
nanoradii/gap dimensionless relationship caused by geometric effects is found and related to
power for nanorods of different aspect ratios and temperatures. A V -shaped configuration is
considered with the results plotted for heat exchange vs. angle. An assessment of the number of
spheres required to produce an accurate approximation of the V -shaped configuration of
nanorods is presented. An error analysis of this method based on a ray blocking assumption
from neighboring spheres is discussed.
An analysis is presented of a new device that utilizes near-field radiative heat transfer
incorporated with pyroelectric materials to convert spacecraft waste heat to electrical energy. A
background of pyroelectric material devices is presented to show the background as applied to
this application. Near-field plane-to-plane radiative heat exchange is implemented for
calculation of the near-field radiative heat exchange within the device. The numerical method is
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based upon an asymptotic approximation shown in previous work for sphere-to-sphere. One
sphere is iteratively increased with the radiative heat exchange continuously calculated until
convergence, whereby, the geometric configuration approaches plane-to-sphere. By
superimposing this method on multiple spheres, the plane-to-plane approximation is achieved.
This procedure is applied for silica and lithium fluoride coated planes. Near-field radiative heat
transfer results expected in the spacecraft device are presented.
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