
457Solar Process Heat and Thermal Power
© 2008 Taylor & Francis Group, LLC
Once σ
total
has been estimated, various CRs (and thus receiver diameters) can be evalu-
ated for their resulting impact on the intercept factor. A reasonable value for the intercept
factor from an engineering perspective is 95%, that is, 5% spill over losses.
The absorber/receiver for the parabolic trough system is usually a metal tube surrounded
by a glass tube. The heat loss coefcient for this type of receiver/absorber is
U
L
=
−
(8.19)
Figure 8.18 shows experimentally measured absorber heat loss coefcients as a function of
absorber ...