Temperature Measurements of a Developing Plume in an Enclosure

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 wal...

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Bibliographic Details
Main Authors: Yu ,Jiann-Horng, 余建宏
Other Authors: Hsu, Cheng-Hsing
Format: Others
Language:zh-TW
Published: 1995
Online Access:http://ndltd.ncl.edu.tw/handle/04297356508995265059
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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}