ACCELERATED RAY TRACING FOR RADIATIVE HEAT TRANSFER MODELING: USING REPETITION OF RAY TRACKS

Abstract

Ray tracing is used in radiative heat transfer calculations for utilizing presence ray obstructions and for view factors calculation. Ray tracing with finite-element mesh supposes determination of traversed cells and intersected faces along the ray. In standard ray tracing next cell is determined by searching cell’s intersected face among several cell faces. A new accelerated method of ray tracing is proposed. The method is based on assumption that track of each current ray is close to track of previous ray and current ray may intersect the same faces and cells as previous ray does. For current ray and current cell the face is firstly checked for intersection which was intersected by previous ray. If ray intersects that face, other faces are not checked. If ray doesn’t intersect checked face, remain faces are checked like with standard method. Proposed method was tested for view factors calculation with model of sectional furnace with hexahedral mesh. Both deterministic and Monte-Carlo methods were used for choosing ray directions. Various numbers of rays were tested to emit from each mesh face that involves in radiative heat transfer (furnace bounds, surface of billets and roll). The method gives acceleration if ray directions are chosen deterministically, and the acceleration increases as number of rays increases. It is shown that in many cases (from 19.6 % to 71.4 %) it is enough to check intersection with only one of five faces, and first checked face is intersected by checked ray. The method doesn’t aff ect the accuracy and gives up to 30 % of acceleration.