15.07.2015   The Experimental Analyze Of The Solar Energy Collector

Reduction of stagnation temperature

1.1. Stagnation temperatures in reference — and ventilated collector (set-up A)

The measurements of the maximum temperatures in the reference — (Tr) and the ventilated collector (Tv) are shown in Fig. 2 for different days and tilt angles. The difference between these temperatures gives the reduction of the maximum temperature, which can be obtained by ventilating the solar collector. The maximum temperature reduction occurs during the warmest period of the day and lies in the present cases between approximately 20-30 K. Fig. 2 (a) and (b) display data from days with high solar irradiance. The collector tilt angle в was 45° for (a) and (b). The bottom slit aperture was 10 mm for (a). The maximum temperature of the ventilated collector, Tv, was slightly below 130 °C.

a) June 9, 2006 b) June 10, 2006 c) August 3, 2006

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Tilt angle: 45°; slit aperture: 10 mm Tilt angle: 45°; slit aperture: 20 mm Tilt angle: 90°; slit aperture: 20 mm

Fig. 2 Maximum temperatures in the ventilated (Tv) and reference collector (Tr) for different days and tilt angles; Im is the global solar irradiance, Ta the ambient temperature [set-up A];

For (b) the bottom slit aperture was extended to 20 mm and the maximum temperature Tv was slightly below 120 °C. In (c) the collector tilt angle was changed to 90° with a bottom slit aperture of 20 mm. Here a maximum temperature of Tv ~ 100 °C of the ventilated collector was measured.