Transient Temperature Measurements of a Plume in a Confined Space

• Main Authors: Hsieh Chin-Feng, 謝錦豐
• Other Authors: Hsu Cheng-Hsing
• Format: Others
• Language: zh-TW
• Published: 1994
• Online Access: http://ndltd.ncl.edu.tw/handle/71387184104594410964

碩士 === 中原大學 === 機械工程研究所 === 82 === The major purpose of the present work is to study the unsteady natural convection phenomenon of a thermal plume, which is coused by locating a constant heat flux annular cylinder heater in a confined enclosure. The combination of thermocouples and data acquisition system are used to measure the temperatures at different locations in the plume. The measurements indicate that the heat transfer mechanism in the plume is characterized by up-moving buoyancy-driven energy envelopes, stratified temperature structure is also observed in the plume. The existence of the structure is due to the retarding motion of the plume near the top wall. Heat convection is less effective in the region. Consequently, heat diffusion becomes the major heat transfer mechanism. According to the measured results, an empirical relation between local Nusselt number and Rayleigh number is obtained by the regression analysis. The formula is written as Nu/Ra^(1/4)= 76.3*t^(-0.92).