Ping-Yang Wang

Transient thermal analysis of semitransparent composite layer with an opaque boundary

Abstract Transient coupled radiative and conductive heat transfer in a two-layer, absorbing, emitting, and isotropically scattering non-gray slab is investigated by the ray tracing method in combination with Hottels zonal method. One outer boundary is opaque, and another is semitransparent. The radiative energy transfer process in a semitransparent composite is divided into two sub-processes, one of which considers scattering, the other does not. The radiative transfer coefficients of the composite are deduced under specular and diffuse reflection and combined specular and diffuse reflection, respectively. The radiative heat source term is calculated by the radiative transfer coefficients. Temperature and heat flux are obtained by using the full implicit control-volume method in combination with the spectral band model. The method presented here needs only to disperse the space position, instead of the solid angle. A comparison with previous results shows that the results are more accurate.

Coupled radiation-conduction heat transfer in an anisotropically scattering slab with mixed boundaries

Abstract Ray tracing method combined with Hottels zonal method is used to establish radiation transfer model in anisotropic scattering media. The transmission progress of radiation intensity in the absorbing, emitting and anisotropically scattering medium is divided into two sub-progresses: emitting–attenuating–reflecting progress and absorbing–scattering progress. For the medium with both surfaces being semitransparent and mirror-like, radiative transfer coefficients are developed. Energy equation of transient coupled radiation and conduction heat transfer is solved by the fully implicit control-volume method. In this paper, it needs only to disperse spatial location while spatial solid angle is integrated directly. On this basis, effects of conduction–radiation parameter, spectral refractive index and scattering phase functions etc., on the temperature field and radiative heat flux field within an anisotropic scattering medium are examined. The results show that: the linear part in linear or nonlinear scattering phase function can produce great difference of the temperature field and radiative heat flux field between anisotropic scattering medium and isotropic scattering medium.

Coupled Radiation and Conduction in a Scattering Composite Layer with Coatings

Transient coupled radiation and conduction in a two-layer isotropically scattering semitransparent nongray medium with thin opaque coatings is studied by the ray tracing method in combination with Hottel and Sarofims zonal method and the control-volume method. The radiative energy transfer process in a semitransparent medium is divided into two subprocesses: without considering scattering and considering scattering. The radiative transfer coefficients of the composite are deduced under specular and diffuse reflection, respectively; internal multireflection, total reflection, and refraction are included. The method is extended to gain the radiative transfer coefficients of an isotropically scattering composite with combined specular and diffuse reflection. The radiative heat source term is calculated from the radiative transfer coefficients. The steady-state and transient temperature distributions and heat fluxes in the composite are obtained for the general boundary conditions of external radiation and convection. The present analysis includes the influences of emissivity, surface radiative properties, and spectral properties on the temperature distributions and the heat fluxes