Please use this identifier to cite or link to this item:
tsung, kuo chun
|關鍵字:||Viscosity independent temperature;黏度隨溫度變化;Transient forced convection;Flat plate;Arrehnius's law;暫態強制對流;平板;Arrehnius定律||出版社:||化學工程學系||摘要:||
The subject of this thesis is to establish a rigorous and precise method to solve the unsteady forced convection heat transfer with a viscosity dependent temperature. Based on Arrehnius's law, the variable viscosity is respectively proposed as (1) the viscosity is decreased with temperature (VDT) and (2) the viscosity is increased with temperature (VIT) due to a step changing uniform wall temperature (UWT) on a semi-infinite flat plate. In order to make a comparison, in a system of the constant viscosity, the simultaneous transient momentum and heat transfer over a flat plate with uniform heat flux (UHF) and case of UWT is also analyzed.
At first, a thickness of developing thermal layer, which simultaneously cover the limiting cases of the transient heat conduction and a steady forced convection, is introduced by means of the scale analysis from the unsteady heat transfer equation to define the transformed variables such as a dimensionless time and coordinates. Finally, the method of line (MOL) with the central finite difference and Newton's iteration is applied to solve the non-similar transformed momentum and energy equations under cases of the variable and constant viscosity, respectively.
As shown from the results, some notable conclusions are summarized as follows:
(1)For a system of the variable viscosity, the time response,
from transient molecule diffusion to a steady momentum
transfer, is increased with values of Pr that base on a
(2)In middle of the transient forced convection heat transfer,
the slope of Nu/Re1/2 varying with time parameter t is
gradually enlarged with value of Pr, and it is clearer for
the case of VDT in contrast to VIT case.
(3)The unsteady heat transfer will be early dominated by the
mechanism of a steady forced convection when value of Pr is
reduced in both cases of VDT and VIT.
Additionally, for the application on practical engineering, the correlation of unsteady friction and convective heat transfer coefficient are respectively developed by the correlation of transient molecule diffusion and a steady momentum transfer and a exact solution of transient heat conduction as well as the correlation of a steady forced convection heat transfer in this content. Comparing with numerical solution, the deviations of the correlation are less than 4%.
|Appears in Collections:||化學工程學系所|
Show full item record
TAIR Related Article
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.