Geophysical Methods Adapted to Highway Engineering Problems

Moore, R. Woodward

doi:10.1190/1.1437779

Cited by 12 publications

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“…Again the reason for this behavior is the steady state assumption depicted by Equation (8). At very low values of m the reaction rate is insensitive to variations in composition and temperature and is thus essentially uniform across the pipe cross section, but nevertheless when the steady state region is reached, ro must have built up to a sufficiently large value to satisfy Equation (15). Thus when the stream enters the equilibrium mixing box, very large changes in temperature and composition are required to bring it to equilibrium.…”

Section: Lewis Number Equal To Unitymentioning

confidence: 96%

“…For energetic chemical reactions these enthalpy fluxes can increase the net rate of heat transfer many fold. Examples of this phenomenon include air dissociation effects upon the rate of heat transfer to re-entering missiles and satellites (1,7,12,14,15,17,22) and the very high heat transfer coefficients observed when heat is transferred to nitrogen tetroxide-nitrogen dioxide mixtures ( 3 , 8, 10, 11, 16, 18, 2 0 ) .When the homogeneous reaction rate is large relative to rates of diffusion within the boundary layer, the temperature and composition profiles through the boundary layer will correspond approximately to local chemical equilibrium. In this case heat transfer rates can be predicted by correlations for physical heat transfer except that effective values of the thermal conductivity and the heat capacity of the gas mixture are used ( 3 , 8, 10, 11, 16, 18, 2 0 ) .…”

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confidence: 99%

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Turbulent pipe flow heat transfer with a simultaneous chemical reaction of finite rate

Brian

1963

AIChE Journal

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The rate of heat transfer from a solid wall to a gas mixture can be substantially affected by rapid reversible homogeneous reactions occurring between components in the gaseous mixture. The thermal gradients cause gradients in the equilibrium gas concentrations and thus produce enthalpy fluxes due to counter diffusion of reactants and products. For energetic chemical reactions these enthalpy fluxes can increase the net rate of heat transfer many fold. Examples of this phenomenon include air dissociation effects upon the rate of heat transfer to re-entering missiles and satellites (1,7,12,14,15,17,22) and the very high heat transfer coefficients observed when heat is transferred to nitrogen tetroxide-nitrogen dioxide mixtures ( 3 , 8, 10, 11, 16, 18, 2 0 ) .When the homogeneous reaction rate is large relative to rates of diffusion within the boundary layer, the temperature and composition profiles through the boundary layer will correspond approximately to local chemical equilibrium. In this case heat transfer rates can be predicted by correlations for physical heat transfer except that effective values of the thermal conductivity and the heat capacity of the gas mixture are used ( 3 , 8, 10, 11, 16, 18, 2 0 ) . The effective equilibrium thermal conductivity and heat capacity of a reacting gas mixture can be substantially greater than the thermal conductivity and heat capacity that the mixture would have if the chemical reactions were frozen. Furthermore these effective properties will generally show much greater variations with temperature than the corresponding properties for gaseous mixtures undergoing no chemical reactions, and the variations with temperature must be considered in order to accurately account for observed heat transfer rates with large temperature driving forces. If the homogeneous reaction rate is high enough to cause the chemical reaction to have a substantial effect upon the heat transfer rate but is not high enough to justify the assumption of local chemical equilibrium, the use of effective thermal properties appears not to be a fruitful approach for predicting the rate of heat transfer. In this case the effective properties would be found to vary with the boundary-layer thickness and thus with the gas flow rate past the solid wall. The effect af a simultaneous chemical reaction of finite rate upon turbulent heat transfer is similar in many respects to the effect upon heat conduction in a stagnant gas layer, which is discussed by Brokaw ( 4 ) .In a recent publication ( 2 ) a theoretical solution was presented for the effect of a simultaneous chemical reaction of finite rate upon the rate of heat transfer between il wall and a reacting gas mixture. The analysis was based upon a film-theory model. By limiting the analysis to the case of a very small temperature driving force the reaction kinetic equation was linearized, and thus the results were given general expression in terms of the partial derivatives of arbitrary reaction kinetic equations. Speculation was presented to suggest that th...

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Section: Lewis Number Equal To Unitymentioning

confidence: 96%

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confidence: 99%

Turbulent pipe flow heat transfer with a simultaneous chemical reaction of finite rate

Brian

1963

AIChE Journal

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“…Even assuming that boring equipment can be brought to a given location, ordinary core borings can be more than ten to twenty times more costly than seismic and electrical resistivity tests (Moore, 1952).…”

Section: Introductionmentioning

confidence: 99%

Identification of landslide slip-surface and its shear strength: A new application for shallow seismic refraction method

Al-Saigh

Dabbagh

2010

J Geol Soc India

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Traditional investigation methods for studying landslide and slope stability is concentrated on studying the present and original geometry of slope, geological cross-section, position of water table and shear strength parameters. It is of prime importance to determine the thickness of slipped ground and the slope of the slip surface. The depth is usually estimated from trial pitting, trenching and drilling boreholes. By using advanced non-invasive geophysical techniques engineers can get a representative picture of hidden subsurface condition with less disruption than using traditional investigation methods like coring, boring and sampling.In this reconnaissance study, seismic refraction survey using a hammer seismograph was conducted in order to determine the thickness of slip material and dip of the slip surface of a landslide.The results of seismic refraction surveys showed good correlation with borehole information. The thickness of the sliding material and the dip of the slip surface were well delineated. The results of the survey were then used to estimate the value of the shear strength parameter as a back value analysis technique. This value was then obtained by ring shear apparatus. The difference between the measured and calculated residual shear strength value was 2°.

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“…This phenomenon has been studied by a number of investigators in recent years. Most attention has been focused on the effect of air dissociation upon heat transfer to reentering space vehicles (1, 17, 25, 28,29) and on the high coefficients obtained for heat transfer to dissociating nitrogen tetroxide (10, 21, 24, 30, 32, 35, 3 8 ) .…”

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confidence: 99%

Heat transfer to decomposing nitrogen dioxide in a turbulent boundary layer

1965

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Heat transfer coefficients were measured for the dissociating system 2 NO2 e 2N0 + 02 in turbulent flow. Heat transfer rates to this reacting gas are limited by the kinetics of the decomposition and recombination reactions. Experimental results agree t o within 10% with a film-theory solution for heat transfer accompanied by a nonequilibrium chemical reaction.The rate of heat transfer from a solid surface to a gas mixture can be greatly augmented if the components in the gas phase undergo a reversible homogeneous chemical reaction. The temperature gradient through the boundary layer gives rise to a gradient in the equilibrium gas composition that produces an enthalpy flux owing to the counterdiffusion of reactant and product species. This flux of chemical enthalpy transported by the diffusing reaction partners may considerably enhance the rate of convective heat transport at the solid surface, especially if the enthalpy change for the chemical reaction is large. This phenomenon has been studied by a number of investigators in recent years. Most attention has been focused on the effect of air dissociation upon heat transfer to reentering space vehicles (1, 17, 25, 28, 29) and on the high coefficients obtained for heat transfer to dissociating nitrogen tetroxide (10, 21, 24, 30, 32, 35, 3 8 ) .The nitrogen tetroxide system is an example of an "equilibrium" system, in which the chemical reaction rate is so fast that the temperature and composition profiles through the boundary layer correspond essentially to local chemical equilibrium. In this case, the heat transfer rate can be predicted from standard relationships for nonreacting systems, except that effective "equilibrium" values for the heat capacity and the thermal conductivity of the gas mixture are used (10, 21, 24, 3 0 ) . These effective equilibrium thermal properties can be much greater than the "frozen" properties that the systems would have if the chemical reaction did not take place, and the equilibrium properties generally vary with temperature more sharply than the thermal properties of nonreacting gases.In contrast to the equilibrium case, a "frozen" system is one in which the chemical kinetic rates are slow relative to diffusion rates through the boundary layer. In this case the reaction cannot support appreciable concentration gradients, and the heat transfer process is not augmented by an enthalpy flux. Such a system was studied by Srivastava, Barua, and Chakraborti ( 3 6 ) when they measured the thermal conductivity of nitrogen dioxide-nitric oxide-oxygen mixtures at low temperatures.Intermediate between the frozen and equilibrium systems is the case of a reaction whose kinetics are too slow to allow the attainment of local chemical equilibrium but are sufficiently fast to cause an appreciable increase in the heat transfer rate. In such nonequilibrium systems the heat transfer rate is strongly affected by the homogeneous chemical reaction rate. The use of effective thermal properties is not a fruitful approach in this case, because the effective ...

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Geophysical Methods Adapted to Highway Engineering Problems

Cited by 12 publications

References 0 publications

Turbulent pipe flow heat transfer with a simultaneous chemical reaction of finite rate

Turbulent pipe flow heat transfer with a simultaneous chemical reaction of finite rate

Identification of landslide slip-surface and its shear strength: A new application for shallow seismic refraction method

Heat transfer to decomposing nitrogen dioxide in a turbulent boundary layer

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