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An Evaluation of the Impact of Surface Coatings on the Heat Transfer in High Temperature Ceramic Recuperators
Date
1988-09Metadata
Show full item recordAbstract
Engineering ceramics, particularly
silicon carbide (SiC), are increasingly
being used as materials in high temperature
recuperators for preheating combustion
air from furnace exhaust gases. As
typical flue gases from these furnaces
may contain sodium, potassium, halides,
etc. that may attack SiC, protective
coatings, such as alumina, zirconia and
others, have been investigated as a means
of increasing the life and reliability
of these SiC recuperators. The objective
of this work was to determine the effect
of coating properties, such as emissivity
and thermal conductivity, on the heat
transfer performance of these high
temperature ceramic recuperators.
The approach was to formulate a
simple rectangular cross section flow
model to determine the amount of heat
transferred by radiation from H2O and
CO2 in the combustion gases to the
coating surface as well as by convection
to the same surface and by conduction
through the coating and plate
material to the combustion air on the
other side. The results indicated that
the thermal conductivity of the coating
and coating thickness had a negligible
effect on the overall heat transfer
coefficient. Further, increasing the
surface emissivity from 0.5 to 0.8
resulted in an increase of 10% in the
overall heat transfer coefficient in
typical waste heat recovery applications.
It was concluded that by combining
enhancement techniques on the air side
with high emissivity materials on the gas
side, one obtains optimal performance
in a gas to gas heat exchanger.
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Citation
Guerrero, P. S.; Rebello, W. J.; Federer, J. I. (1988). An Evaluation of the Impact of Surface Coatings on the Heat Transfer in High Temperature Ceramic Recuperators. Energy Systems Laboratory (http://esl.eslwin.tamu.edu). Available electronically from https : / /hdl .handle .net /1969 .1 /92398.