SIMULATED NUCLEAR REACTOR VIBRATIONAL HEAT TRANSFER. Quarterly Progress Report, August 1, 1962-October 31, 1962
Progress on the design and construction of vibrational heat transfer test sections is reported. An electrodynamic shaker, at the lower frequencies, and piezoelectric ceramic transducers, at higher frequencies, will provide the vibrations to heated cylindrical tubes. The design of the transducer plates is described. Calibration of a probe for determining the sound pressure level is discussed. (M.C.G.) The total mass transfer diffusivity for turbulent pipe flow was represented by a second order tensor with two significant components, the radial mass diffusivity and the axial mass diffusivity. These components were determined as functions of radial position for three Reynolds numbers in the low turbulent range by making a study of the transient diffusion of a dye solution from a point source into water in turbulent pipe flow. Concentration data were obtained as a function of position and time. These data were combined with the results of a steady state experiment to compute the diffusivities from a second order linear partial differential equation. Two solution methods were used : a graphical derivative evaluation procedure, and a method which applies the LaPlace transformation in both time and axial distance. Both methods produce two simultaneous ordinary differential equations which could be numerically integrated to produce the diffusivities. Both the radial and axial diffusivity were found to vary with radial position. The variation of the radial component qualitatively resembles the variation of eddy viscosity in the same system. The axial component was appreciable only in the central or core region of the stream. The average values of both components were found to increase linearly with Reynolds number. The diffusivities could be correlated as functions of position and Reynolds number by expressions which accounted for the effects of the velocity, the velocity gradient, and the boundary layer. The ratio of axial diffusion to bulk flow was found to increase slightly with Reynolds number through the range studied. Eddy diffusion was about one hundred thousand times greater than molecular diffusion. Neglecting the contribution of axial diffusion produces smaller calculated values of the radial diffusivity. The variation of the Peclet and Schmidt numbers in the system was similar. Both quantities decreased with increasing Reynolds number in the range. Although a rough analogy between mass and momentum transport existed, the diffusivities were generally not equal. The Schmidt number varied from a value less than one to a value greater than one across the tube radius. It was found that the position Peclet numbers for both mass and momentum varied similarly with position Reynolds numbers. Both quantities increased near the wall, and approached values given by correlations which have been previously proposed for momentum transport quantities. (auth)
- Research Organization:
- Catholic Univ. of America, Washington, D.C.
- NSA Number:
- NSA-17-023475
- OSTI ID:
- 4724074
- Report Number(s):
- CUA-NE-26
- Country of Publication:
- United States
- Language:
- English
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