Thermal-flux effect

Thermal diffusion effects will be neglected throughout, so the flux relations are given by equations (3.17) - (3.19), which are repeated here for convenience ... 

Lapp, K., Thibault, P., Ward, S., and Weller, D. 1991. The Effect of Momentum and Thermal Flux in Long Lines on the Westech Second Generation Detona-tion/Flame Arrester. Paper presented to DOT/USCG Hazardous Material Branch Bulk Cargo Section, June 12, 1991, Washington, DC. 

Carne, M., and D. H. Charlesworth, 1966, Thermal Conduction Effects on the Critical Heat Flux in Pool Boiling, Chem. Eng. Prog. Symp. Ser. 62(64) 24-34. (5)... 

The mass flux vector is also the sum of four components j (l), the mass flux due to a concentration gradient (ordinary diffusion) jYp), the mass flux associated with a gradient in the pressure (pressure diffusion) ji(F), the mass flux associated with differences in external forces (forced diffusion) and j,-(r), the mass flux due to a temperature gradient (the thermal diffusion effect or the Soret effect). The mass flux contributions may then be summarized ... 

The present approach to the prediction of thermal transport in turbulent flow neglects the effect of thermal flux and temperature distribution upon the relationship of thermal to momentum transport. The influence of the temperature variation upon the important molecular properties of the fluid in both momentum and thermal transport may be taken into account without difficulty if such refinement is necessary. 

The external heat flux (q"x) from the cone heater does not exclusively determine the heat flux important for samples pyrolysis in the cone calorimeter, since the reradiation from the hot sample surface (q"eTad), the loss by thermal conductivity into the specimen and the surroundings ( I SS), and the heat flux from the flame (q Lmt) are also of the same order of magnitude.82 85 Thus, the heat flux effective with respect to pyrolysis during a cone calorimeter run (qeii) is the result of the external heat flux and the material s response (qeB = q L + < L - gCad - qLs). 

The overall heat transfer coefficient U in Eqn. (3) is based on the measured temperature difference between the central axis of the bed and the coolant. It is derived by asymptotic matching of thermal fluxes between the one-dimensional (U) and two-dimensional (kr,eff kw,eff) continuum models of heat transfer. Existing correlations are employed to describe the underlying heat transfer processes with the exception of Eqn. (7), which is a new result for the apparent solid phase conductivity (k g), including the effect of the tube wall. Its derivation is based on an analysis of stagnant bed conductivity data (8, 9), accounting for "central-core" and wall thermal resistances. 

Holmium in the form of HooO, powder was sealed in quartz ampoules (5 mg/ampoule), which were cold welded in an aluminium container for irradiation in the core of PARR-1 at a thermal flux of 1 x 10 n-cm -s for 1,10, 24 or 48 h. To work out the effect of shielding on the activation yield, 10,20 and 40 mg of Ho were also irradiated. Irradiated targets were dissolved in 5M HCl and evaporated to dryness. The residue was dissolved in physiological sahne solution and diluted to a specified volume for labelhng studies. The long hved radionuchdic impurity Ho was also measured using gamma spectrometry. 

The diffusion-thermal effect or the Dufour energy flux eff describes the tendency of a temperature gradient under the influence of mass diffusion of chemical species. Onsager s reciprocal relations for the thermod3mamics of irreversible processes imply that if temperature gives rise to diffusion velocities (the thermal-diffusion effect or Soret effect), concentration gradients must produce a heat flux. This reciprocal effect, known as the Dufour effect, provides an additional contribution to the heat flux [89]. 

It is convenient to determine an effective cross section a for the nuclide, so that when a is multiplied by the total thermal flux (j>M the proper reaction rate is obtained ... 

The Westcott g and s factors can also be used to determine the effective thermal cross section a, such that when multiplied by the integrated Maxwell-Boltzmann thermal flux the proper reaction rate with a nuclide is obtained, as already defined by Eq. (2.55). From Eqs. (2.55) and (2.62), a is related to a by... 

Thermal flux time, n/kb Effective cross section Op, in bams, of fission-product pairs from ... 

In compliance with the Onsager reciprocal formula in irreversible processes thermodynamics, the concentration gradients of the chemical species are also able to produce the thermal flux, known as Dufour effect. 

The effect of a local change in the reactor is a fairly sensitive function of position. Experiments described in Appendix 3 have shown that an absorber is about twice as effective in the center of the core as at the edge, and the importance of an absorber diminishes rapidly as its distance from the core increases. This, of course, means that experiments can be done in the reflector, where the thermal flux is very high, without producing a major change in reactivity. 

The term in the mass flux involving the temperature gradient describes the Soret (or thermal-diffiisiori) effect the term on the right side of Eq. (31) involving the concentration gradient describes the Dufour (or diffusion-thermo) effect. 

Flux effect exists in Cu-containing materials. Both cluster size and number density increase at lower flux conditions in Cu-containing materials. Some computer simulations at an atomistic level have demonstrated that this is due to the contribution of thermal vacancies at very low flux levels. ... 

To give a comparison of OMD with, for example, MD, in the case of orange juice, Alves and Coelhoso (2006) found that the water flux was more than 50% lower in MD processing simply because of the thermal polarisation effect. 

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