Abstract:
Background In high-temperature pebble bed cores, radiative heat transfer plays a crucial role, where the view factor is a key parameter in determining radiative exchange between particles. Traditional methods for calculating view factors rely on complex integration, which varies with geometric configurations and is computationally intensive.
Purpose This study aims to accurately calculate view factors in randomly packed pebble beds. It proposes a ray tracing model based on thermal radiation mechanisms to simplify the calculation of view factors between particles in complex packing structures.
Methods Firstly, the particle surface is discretized to generate uniformly distributed ray origin points. Secondly, ray directions are determined based on the characteristics of thermal emission. Thirdly, rays defined in local coordinates are transformed into global space and traced for intersections with target particles. Finally, the view factor is computed as the ratio of rays that collide with target particles to the total number of emitted rays.
Results The results show that inter-particle radiation is mainly concentrated at the center line and decays towards the periphery, showing a clear cosine distribution. The radiation range of a single particle is mainly concentrated within twice the particle diameter, at which point the view factor exceeds 0.98 and the number of particles is less than 100. Within three times the diameter, the cumulative view factor exceeds 0.99.
Conclusions The proposed quasi-Monte Carlo ray tracing model provides an accurate and efficient method for computing view factors in dense particle systems. It effectively captures the anisotropic nature of radiative transfer in randomly packed beds and offers a practical tool for analysing thermal radiation in high-temperature pebble beds.
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