Transient Heat Transfer In A Semitransparent Radiating Layer With Boundary Convection And Surface Reflections Nasa Tm 111963 May 30 1997

Transient Heat Transfer In A Semitransparent Radiating Layer With Boundary Convection And Surface Reflections ... NASA-TM-111963 ... May 30, 1997

Radiation Effects in a Semitransparent Gray Coating Heated by Convection and Cooled by Radiation

A parametric study using a one dimensional model of a semitransparent gray thermal barrier coating was performed to gain an understanding of the role thermal radiation can play in the heat transferred. Some ceramic materials are semitransparent in the wavelength ranges were thermal radiation is important. Therefore, absorption, emission, and scattering of thermal radiation can affect the he at transfer through the coating. In this paper, a one dimensional layer was used to model the heat transfer process occurring, in a burner test rig. The semitransparent layer is heated by a hot gas flowing over its surface. The layer and substrate at a cooled by radiation to the surroundings. The back side of the substrate is insulated. The coating is assumed to be gray (absorption and scattering coefficients are not function of wavelength). An absorption coefficient of 0.3/cm and scatter a rig coefficients of 0 (no scattering) and 100/cm (isotropic scattering) were used. The thickness and thermal conductivity of the layer are varied. The results show that the temperatures are affected by the properties of the semitransparent .ever and the emissivity of the substrate. The substrate and surface temperatures are presented. The apparent temperature an optical pyrometer would read for the emitted energy is also given. An apparent thermal conductivity was calculated for the layer. Spuckler, Charles M. Glenn Research Center NASA/TM-2002-211554, NAS 1.15:211554, E-13329

The Effect of an Arbitrary Surface-temperature Variation Along a Flat Plate on the Convective Heat Transfer in an Incompressible Turbulent Boundary Layer

An analysis was performed to determine the effects on the rates of convective heat transfer produced by arbitrary variations of the surface temperature with distance along a flat plate. The analysis was confined to the case of a low-speed turbulent boundary layer on a flat plate oriented parallel to the free-stream velocity. It was found that a continuously variable surface temperature has, in general, a smaller effect on the local convective heat transfer than does a surface-temperature discontinuity.