T e x a sThe turbulent transport of mass, energy, and momentum was studied in a 4 in. diameter cylindrical column packed with 0.3 in. diameter stoneware spheres. Helium was used as a tracer material, with air as the mainstream fluid. The concentration of tracer present, the temperature, and the velocity of the gas were measured a t several axial and radial increments.These data were analyzed numerically to obtain the radial component of the effective thermal conductivity and the radial component of the mass-dispersion coefficient as functions of radial position. Experimental conditions covered isothermal determinations a t room temperature and nonisothermal determinations in which a temperature gradient was established in the radial direction. Significant differences were found between the isothermal and strong13 nonisothermal results, primarily for the velocity profiles and thermal conductivities. Correlations were developed for the local values of the parameters.Heat and mass transfer in packed beds is important in many ways in the chemical industry. Some examples of the use of packed beds are catalytic reactors, chromatographic reactors, ion exchange columns, and contacting towers. The objective of this study was to obtain correlations of the point values of eddy thermal conductivity and mass dispersion coefficients in a nonisothermal system in terms of the physical properties of the packed bed and the fluid flowing through it.Considerable data has been reported in the literature concerning the prediction of temperatures and concentrations in packed bed reactors (1 through 9). Much of the effort has utilized the procedure of writing differential mass and energy balances on the reactor, assuming that the packed bed could be treated as a continuum, although alternate methods have also been used (I 0, 11 ) . The resulting differential equations were then simplified by various assumptions to yield equations that could be solved analytically. Results from computations of this type have been useful tools, but have not been completely successful in predicting the performance of actual reactors (1 ) . The next level of sophistication was to solve the partial differential equations by numerical methods using high speed computers. This allowed Richardson and Fahien ( 1 2 ) , for example, to use varying values for the bed properties in calculations of reactor behavior. However, they found that various assumptions utilizing mean value correlations for varying local values gave poor comparison with measured reactor data.Ideally, one would like the values of the mass and heat transfer dispersion coefficients to be as representative of the real case as possible. In other words, if these parameters are dependent upon temperature level, concentration, position, velocity, etc., knowledge of this dependence is desired so that the most accurate values may be used in design calculations. Yagi and Kunii ( 1 3 ) measured effective values of thermal conductivity, and also used values reported by other investigators (1 4 through 19) t...

A one-dimensional numerical model is developed to predict the diurnal variations of vertical temperature and concentration profiles in salt-gradient solar ponds. The model employs augmented thermal and mass diffusivities due to turbulent wind mixing and double-diffusive convection. Numerical results indicate that the thickness of the surface convective layer increases with wind speed (or the wavelength of the surface wave). Double-diffusive convection is, in the absence of wind, capable of sustaining a mixed layer at the surface when strong cooling occurs over the pond. In field ponds, the surface convective layer is probably maintained as a result of the combined action of wind-generated turbulent mixing and double-diffusive convection.

This project was an analytical and experimental study of the application of the Compound Parabolic Concentrator (CPC) and the Dielectric Compound Parabolic Concentrator (DCPC) to solar photovoltaic conversion. The objectives of the program included: * Determination of the design requirements for using a CPC or DCPC for concentrating solar energy onto photovoltaic cells. * Analyses of the design requirements imposed by the CPC or DCPC optical characteristics on the photovoltaic cells. ® Development of fabrication techniques suitable for making CPC or DCPC components in mass production. ® Design of a CPC panel and a DCPC panel that meet the essential requirements of JPL Specification 5-342-1. ® Construction and testing of a 1.2 m x 1.2 m (nominal) passively cooled panel incorporating the CPC. ® Construction and testing of a 1.2 m x 1.2 m (nominal) passively cooled panel incorporating the DCPC. ® Determination of the cost-effectiveness potential if panels of this type were mass produced. These objectives were all met. The results of the first four above objectives were used in constructing the DCPC and CPC panels. Panels were delivered to

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