Showing papers by "Ephraim M Sparrow published in 1973"
TL;DR: In this article, the authors used the naphthalene sublimation technique to perform mass transfer at a heated isothermal upwardfacing plate or at a cooled downward-facing plate.
253 citations
156 citations
TL;DR: In this article, an analysis is made to determine how the radiant energy streaming from an isothermal-wall conical cavity is affected by a baffle that partially obstructs the cavity opening.
Abstract: An analysis is made to determine how the radiant energy streaming from an isothermal-wall conical cavity is affected by a baffle that partially obstructs the cavity opening. Consideration is given both to baffles that are maintained at the same temperature as the cavity wall (emitting baffles) and to baffles that are cooled to a temperature well below that of the wall (non-emitting baffles). The cone-apex angle and the emissivity of the cavity wall are varied parametrically. The results are obtained by employing a newly devised Monte Carlo method, the application of which is described in detail. The presentation of results is made in terms of the apparent emissivity, which is the ratio of the radiant energy actually streaming from the cavity to the radiant energy emitted by a black surface whose size is the same as the baffle aperture. It is found that the apparent emissivity increases as more and more of the cavity opening is blocked by the baffle. The increases of apparent emissivity are greater when the baffle is emitting than when the baffle is non-emitting.
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TL;DR: In this article, a contrived transient version of the steady-state problem is constructed by appending time derivatives to all the participating equations, regardless of whether or not such terms have physical reality.
13 citations
TL;DR: In this article, an analysis of the effect of film absorption on the characteristics of a reflection polarizer consisting of a thin film on an absorbing metal substrate is made. But the analysis is restricted to the case when only one component of polarization is extinguished by means of interference, and it is shown that very weakly absorbing or transparent films may give rise to excessive sensitivity of the extinguished component to departures from the polarizing angle and from the optimum film thickness.
Abstract: An analysis is made of the effect of film absorption on the characteristics of a reflection polarizer consisting of a thin film on an absorbing metal substrate. Monochromatic polarized light is obtained when one component of polarization is extinguished by means of interference. A method of analysis is developed for determining the angle of incidence and the film thickness for which polarization occurs. Numerical reflectance results are presented for polarizers having a silver substrate and films with different degrees of absorption. Very weakly absorbing or transparent films may give rise to excessive sensitivity of the extinguished component to departures from the polarizing angle and from the optimum film thickness, particularly when the substrate is highly reflecting (e.g., silver). The use of properly selected absorbing films can provide a low degree of sensitivity for the extinguished component and still yield adequately high reflectances for the unextinguished component.
5 citations
5 citations
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TL;DR: It is found that by proper choice of the extinction coefficient of the film, all four criteria of quality can be satisfied and for substrates having intermediate values of reflectance, very small film extinction coefficients appear to be appropriate.
Abstract: The performance characteristics of film-substrate reflection polarizers consisting of an absorbing film on a metallic substrate are investigated. Monochromatic polarized light is obtained for certain discrete values of incidence angle and film thickness, corresponding to given values of the optical constants and the wavelength. The departures from perfect polarization due to operation at off-design wavelengths are examined. Three additional criteria are also employed to appraise polarizer quality. It is found that by proper choice of the extinction coefficient of the film, all four criteria of quality can be satisfied. For substrates having intermediate values of reflectance, very small film extinction coefficients appear to be appropriate. When the substrate is highly reflecting, somewhat larger extinction coefficients are required.
TL;DR: Analytical results are presented for radiation interchange in cavities having nonisothermal walls in order to implement experimental methods for determining the emittance of solids.
Abstract: Analytical results are presented for radiation interchange in cavities having nonisothermal walls in order to implement experimental methods for determining the emittance of solids The cavity may be visualized as a hole that is machined into the exposed face of a solid whose emittance is to be determined, with the solid being heated uniformly from behind The results were obtained by solving the coupled problems of radiant transport in the cavity and two-dimensional heat conduction in the solid that bounds the cavity From the solutions, results for the radiant flux leaving the base surface of the cavity are presented as a function of the emittance, of the depth-radius ratio of the cavity, and of a temperature gradient parameter This information can be used in conjunction with measurements of the radiances of the base surface and the exposed face of the solid to determine the emittance A method is also described for simultaneously determining both the emittance of the material and the temperature of the exposed face