Control Of Radiative Heat Transfer Research Articles

Control of Radiation Heat Transfer from Solid Surface Using Grating Composed of Parallel Elliptical Cylinders. Energy Concentration in Direction Normal to Solid Surface.

A specially designed grating is applicable to directional control of radiation heat transfer from a heated surface. In this paper, a study of radiation heat transfer control using a grating composed of elliptical cylinders (GEC) is described. An analysis of radiation heat transfer is performed for a physical model in which the grating of circular cylinders (GCC) of our previous study are replaced by the GEC and the major or minor axes of the elliptical cylinders are set vertically to the heated base surface. Numerical solutions are obtained. The apparent hemispherical emissivity and the limiting angle expressing the degree of radiation energy concentration are calculated for geometrical parameters, e. g., ratio of the major axis to the minor axis and center-to-center distance of cylinders. It is found that the GEC has even better characteristics for the control of radiation heat transfer, compared with the GCC, especially for apparent hemispherical emissivity, i. e., the heat-transfer rate.

Control of Radiation Heat Transfer from Solid Surface by a Grating of Parallel Circular Cylinders.

Radiation heat transfer from a solid plane surface is directionally controllable by means of a grating composed of circular cylinders. An analysis of the radiation heat transfer is made for a physical model in which a grating of parallel cylinders is placed in front of a black heat-transfer surface, and the cylinder surfaces have both specular and diffuse reflectivity components ( ρc=ρsc+ρdc). Numerical solutions are obtained. The apparent directional emissivities and the limiting angles expressing a degree of energy concentration are calculated for parameters such as ρsc/ρc and center-to-center distance of cylinders. It is clarified that the grating of cylinders is useful for concentrating the radiation energy emitted from the heat-transfer surface in the direction normal to the grating surface.

Directional Control of Radiation Heat Transfer by V-Groove Cavities—Collimation of Energy in Direction Normal to Cavity Opening

To improve the V-groove cavity devised for directional control of radiation heat transfer, a new model with a black fin provided on the cavity base is proposed. The radiative characteristics of the new model are theoretically offered comparing two typical constitutional forms—symmetrical and asymmetrical. It is evident that the fin helps accelerate radiation heat transfer from the V-groove and promote its collimation. The effects can be further enhanced by carefully choosing the various geometrical parameters. The new V-groove cavity proposed would probably be evaluated as a favorable directional surface. The direction of energy collimation can be altered by using the asymmetrical groove cavity.