Thermal modelling of parabolic trough collectors - Solar Energy Sciences and Engineering Applications - page 189

Figure 6.3.3 Comparison of measured against predicted thermal efficiency with air in receiver annulus.
Figure 6.3.4 Comparison of measured against predicted heat loss with air in receiver annulus.
stiff and precise parabolic reflector panels manufactured from reinforced polymeric
material, a structurally efficient galvanised steel torque tube, a tubular receiver and an
accurate solar tracking system.
As the collector is able to operate up to about 200 ◦ C the selective coating properties
are assumed to be constant to all possible temperature range. The results of the program
are shown graphically in Figure 6.3.6 and give a thermal efficiency of 58.16% at
200 ◦ C, which is very satisfactory. These results were obtained at a solar radiation of