When greater accuracy is required, the following equations can be used to represent the curves plotted in Figures 3.38 to 3.40. The various symbols used are presented in Figure A6.1. The subscript T is for the truncated compound parabolic collector (CPC) design.
FIGURE A6.1 A truncated CPC. Its height-to-aperture ratio is about one half the full height of a CPC.
The following equations apply for a full and truncated (subscript T) CPCs (Welford and Winston, 1978):