JiSMART2021—027: Simulation of Tube Transmission Efficiency of Light Pipes Based on Ray-Tracing Method

Abstract

The precise prediction of a light pipe's tube transmission efficiency (TTE) is a really difficult issue. Based on measured data, CIE-173 document “Tubular Daylight Guidance Systems” have provided the TTE values of typical straight pipes and bends, and also proposed a method to roughly estimate the overall TTE of any component, composed of at least two straight pipes and one bend. This article aims at obtaining light pipes’ TTEs by optical simulation and comparing the simulated results of different kinds of light pipes with the corresponding TTE values in CIE-173 document. Thus, a series of light pipes’ optical models have been developed to calculate the various pipes’ TTEs by using TracePro. The simulation results indicate that a light pipe’ TTE reduces with the increase of its aspect ratio or bending angle (if there is one or more bends), while it rises with the increase of the inner surface’s reflectance. Besides, the simulation results demonstrate a considerable agreement for straight pipes’ TTEs with CIE-173’s values, but display a substantial divergence for the TTE data of bends and components in comparison of CIE-173’s values, and reveal that pipe diameter does not affect bends’ TTEs.