Critical conditions in uniform temperature systems with variable heat transfer coefficients in thermal explosion theory

1994 ◽  
Vol 7 (3) ◽  
pp. 223-231 ◽  
Author(s):  
Saad A. El-Sayed
Keyword(s):  
Heat Transfer ◽  
Thermal Explosion ◽  
Critical Conditions ◽  
Uniform Temperature ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Variable Heat ◽  
Thermal Explosion Theory

The Effect of the Thermal Boundary Condition on Transient Method Heat Transfer Measurements on a Flat Plate With a Laminar Boundary Layer

1996 ◽  
Vol 118 (4) ◽  
pp. 831-837 ◽  
Author(s):  
R. J. Butler ◽  
J. W. Baughn
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Boundary Condition ◽  
Thermal Boundary Condition ◽  
Uniform Heat Flux ◽  
Transient Method ◽  
Uniform Temperature ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Numerical Predictions

The heat transfer coefficient distribution on a flat plate with a laminar boundary layer is investigated for the case of a transient thermal boundary condition (such as that produced with the transient measurement method). The conjugate problem of boundary layer convection with simultaneous wall conduction is solved numerically, and the predicted transient local heat transfer coefficients at several locations are determined. The numerical solutions for the surface temperature are used to determine the Nusselt number that would be measured in a transient method experiment for a range of (nondimensionalized) surface measurement temperatures (liquid crystal temperatures when they are used as the surface sensor). These predicted transient method results are compared to the well-known results for uniform temperature and uniform heat flux thermal boundary conditions. Measurements are made and compared to the numerical predictions using a shroud (transient) experimental technique for a range of nondimensional surface temperatures. The numerical predictions and measurements compare well and both demonstrate the strong effect of the (nondimensional) surface temperature on transient method measurements. Transient method measurements will give heat transfer coefficients that range from as low as that of the uniform temperature case to higher than that of the uniform heat flux case (a 36 percent difference). These results demonstrate the importance of the temperatures used with the transient method.

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