THESIS
2019
xiii, 73 pages : illustrations ; 30 cm
Abstract
A thermal diode is a device where the effective thermal conductivity in one direction is higher
than that in the opposite direction. Among various types of thermal diodes reported in the
literature, the phase-change thermal diode yields a greater thermal rectification performance.
However, there are some limitations to the current phase-change thermal diodes, such as
complex structures, complicated manufacturing procedures, and sophisticated working
mechanisms. More importantly, some thermal diodes involve toxic, rare and expensive
constituent materials. Hence, a simple water-vapour chamber thermal diode utilising the latent
heat from pure water is designed, assembled and investigated, both experimentally and
numerically in this study. The effects of the temperature gradient ac...[
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A thermal diode is a device where the effective thermal conductivity in one direction is higher
than that in the opposite direction. Among various types of thermal diodes reported in the
literature, the phase-change thermal diode yields a greater thermal rectification performance.
However, there are some limitations to the current phase-change thermal diodes, such as
complex structures, complicated manufacturing procedures, and sophisticated working
mechanisms. More importantly, some thermal diodes involve toxic, rare and expensive
constituent materials. Hence, a simple water-vapour chamber thermal diode utilising the latent
heat from pure water is designed, assembled and investigated, both experimentally and
numerically in this study. The effects of the temperature gradient across the thermal diode, and
the water-air volume ratio inside the water chamber on the heat transfer and thermal
rectification performance of the water-vapour chamber thermal diode are examined.
Mathematical models for anticipating the heat transfer performance of the proposed thermal
diode are also built and verified by the experimental results. It should be noted that this is the
first study to investigate this kind of thermal diode theoretically and experimentally. The
findings reveal that the forward effective thermal conductivity of the thermal diode shows a 50
% enhancement when the hot side temperature rises from 40 ℃ to 70 ℃. A maximum diodicity
of 1.43 is reported at the water-air volume ratio of 0.5. The results also indicate that the heat
transfer and thermal rectification performances of the thermal diode is improved for a high
water-air volume ratio. There are lots of applications for the thermal diode. In this study, a
thermal diode based solar thermoelectric power system is established. The findings show that
a maximum power output of 0.057 W is reported when the hot plate temperature is 120 ℃ and
the cooling temperature is 10 ℃.
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