A coupled radiative and conductive three dimensional numerical model of transparent insulation material (TIM) is presented and the simulation results are compared with experimental results found in the literature. Since the studied TIM structure has the form of honeycomb that consists of a cellular array of repetitive nature, we considered a single isolated cell with opaque and adiabatic walls. The combined radiation and conduction heat transfer across the isolated cell is treated by solving the energy equation coupled to the radiative transfer equation (RTE). For the resolution of the RTE, the Finite Volume Method is used. The boundary conditions for the intensity of radiation are considered as diffusely emitting, specularly reflecting opaque surfaces. The detailed simulation of the TIM cells allows to obtain simplified correlations of the heat losses through the TIM that then will be introduced into a general model of flat plate solar collector with TIM.

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