What is the operating temperature for an evacuated tube collector operating at \(50 \%\) efficiency if the insolation is \(800 \mathrm{~W} / \mathrm{m}^{2}\) ? Use data from Figure 7.19.

Figure 7.19

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80 50 20 ne collector efficiency 20 40 40 0 Symbol Fluid Covers Surface FRnopt FRU (W/mC) 123456 Water 0 Black paint 0.68 34.0 Water 1 Black paint 0.74 8.2 Air 1 Black chrome 0.52 4.8 Water 1 Black chrome 0.70 4.7 Water 2 Black chrome 0.61 3.2 Water Evacuated tube 0.54 1.4 5 Flow rates Water: 0.02 kg/s m(14.7 lb/h ft) Air: 0.01 m/s m(1.97 cfm/ft) 6 2 0.1 0.2 Tin-Ta (km) I 0.3 0.4