Page 166 - Design of Solar Thermal Power Plants

3.3 THERMAL PERFORMANCE OF PARABOLIC TROUGH COLLECTOR 151

TABLE 3.3 Measured Values of Heat Loss Coefficient of SCHOTT PTR70
Evacuated Tube [22]

Evacuated
Evacuated Mean Tube and
Tube Mean Glass Ambient Air Ambient Air Heat Loss
Temperature/ Temperature/ Temperature/ Temperature Coefficient

Testing C C C Difference/ C HL/(W/m)
1 100 26 23 77 15
2 153 30 23 130 23
3 213 35 23 190 43
4 246 38 24 222 59
5 317 50 24 293 113
6 346 55 23 323 141
7 390 65 24 366 204
8 418 73 25 393 257
9 453 82 23 430 333
10 458 84 24 434 348
11 506 99 24 482 495

FIGURE 3.20 Heat loss coefficient of PTR70 evacuated tube from schott of germany [22].
Data Source: Technical Report NREL/TP-550-45633, May 2009.