CALCULATING THE REFLECTED PATHS OF RADIATION IN HIGH REFLECTIVITY ENCLOSURES

摘要

A novel method of calculating the reflected paths of radiation in Monte Carlo simulations is described. This method is well suited to high reflectivity (e.g., ρ > 0.5) systems, which tend to have strong directional and bi-directional characteristics. The prime advantage of the described approach is that it retains the inherent flexibility of the traditional Monte Carlo approach, but allows the paths of reflected radiation to be evaluated without the need for ray-surface intersection calculations. The paths of reflected radiation can therefore be evaluated much more rapidly, and Monte Carlo simulation times can be substantially reduced. Simulations of an enclosure containing an obstruction, exhibiting directional emission and reflection, and bi-directional reflection, are described and compared with solutions obtained by traditional Monte Carlo. For the studied cases, predictions from the new and traditional methods are in close agreement. Application of the new method resulted in computational speeds being improved by up to a factor of eight, depending upon the chosen reflection function (directional, specular, or bi-directional) and the desired accuracy of radiative exchange-factor calculation. For example, to achieve an average exchange-factor uncertainty of ±10% (95% confidence), computational performance improvements of approximately twofold for the bi-directional case and threefold for the specular case were attained. For an uncertainty of ±5% (99% confidence), the performance improvements increased to six and eightfold for bi-directional and specular reflection respectively.