| Summary: | 碩士 === 中原大學 === 機械工程研究所 === 83 === The goal of the present work is to study the unsteady natural
convection phenomenon of a developing thermal plume, which is
caused by locating a constant heat flux annular cylinder heater
on the bottom wall of a confined enclosure. Six thermocouples
are used to measure the temperature profiles of the developing
thermal plume . The combination of the temperature measuring
system , the data acquisition system and a computer is used to
collect data and develop an empirical formula relating heat
transfer parameters , i.e., Nu=f(Fo,Ra). The measurements
indicate that the heat transfer mechanism in the plume is
characterized by up-moving buoyancy-driven energy envelopes. At
the upper portion of the plume ,stratified temperature
structure is observed.As the result of this thermal
stratification , the convective heat transfer is less effective
and the heat diffusion becomes the major heat transfer
mechanism The Rayleigh number is within $10^7$∼$10^{13}$,
which indicates that the structures of the plume include the
laminar, transition and turbulent ranges. The data are analyzed
and correlated by the least-squares regression method to obtain
an empirical formula relating the Fourier number, the local
Nusselt number and the modified Rayleigh number. The relation
is expressed as Nu/Ra^1/4=0.0035*Fo^{-0.915}
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