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Influence of the Vertical Heat Transfer on Thermocapillary Convection in A Rectangular Cavity

Author: ZhangHongRu
Tutor: LiYouRong
School: Chongqing University
Course: Power Engineering and Engineering Thermophysics
Keywords: Thermocapillary convection Numerical Simulation Rectangular liquid pool Heat flux
CLC: TK124
Type: Master's thesis
Year: 2010
Downloads: 31
Quote: 0
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Abstract


Horizontal temperature gradient and vertical temperature gradient co-driven thermal convection process is widely present in the crystal growth, thin films, coatings and paint and other industrial areas of production, however, the current understanding of the vertical heat transfer characteristics of horizontal fluid layer Marangoni convection rarely, so study the liquid tanks vertical heat transfer thermal convection process to determine the critical flow from steady-state transition to the oscillating flow conditions, the physical mechanism of transition between the various flow patterns can not only enrich thermocapillary convection theory, and provide a theoretical basis for improving the production process, and therefore, has important theoretical significance and practical value. Established the physical and mathematical models of horizontal fluid layer Marangoni convection consider the bottom of the liquid pool heating, free-surface heat, and two-dimensional and three-dimensional numerical simulation of the temperature field and flow field in the liquid layer, parameters of the liquid pool width to depth ratio, the bottom of the heat flux, Marangoni (Ma) number and Biot (Bi) number of thermal convection, and understanding of the basic characteristics of the steady-state and oscillatory thermocapillary convection. The results show that (1) when the the sidewall temperature difference, the flow is steady state current, rectangular liquid tanks with the bottom heating a heat flux density increases, current will be converted to the opposite direction of rotation of the the twin asymmetric flow stream type The transformation of the critical heat flux increases with the increase in the number and Ma Bi. (2) the smaller the heat flux inhibit thermal convection, when the heat flux increases to a certain value, the maximum temperature inside the liquid pool, its value decreases with the increase of the number of Ma, with wide Depth increases. When the rotation direction opposite to the twin asymmetric flow, the flow near the hot wall extracellular extension, with the width to depth ratio increases and extends backward with the increase of the number of Ma, contraction. (3) As Ma is large, the flow from steady-state multi-cell flow into the oscillating flow, that hot fluid wave, the wavelength increases with the increase of the number of Ma, velocity and frequency with Ma number increases decreases. In the shallow pool, the current changes in the critical Ma number with the increase of the heat flux first increases and then decreases, deep liquid pool critical Ma number increases monotonously with the increase of heat flux. (4) velocity and temperature field and the two-dimensional numerical simulation of three-dimensional numerical simulation of the mainstream cross-section close to the flow pattern is identical; When the hydrothermal wave, three-dimensional numerical simulation of frequency, velocity and wavelength two-dimensional numerical simulation results are basically the same, therefore, can be used numerical method for simulating rectangular liquid pool of thermal convection characteristics and the impact of various factors on the thermal convection.

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CLC: > Industrial Technology > Energy and Power Engineering > Thermal engineering, heat > Thermal Engineering Theory > Heat Transfer
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