3.2. Model validation
The validation process of the optical-geometric model is performed
by comparing the experimental results for the WGA500
concentrator [31] and the results of the simulator of the geometric-optical
model. To do this, the optical and geometric features
of the WGA500 concentrator (focal length 4.5 m, diameter 3.8 m
parabola, reflector) are introduced in the simulator. This type of
concentrator is most appropriate for validating low-power solar
concentrators, according to a study by Fraser [15]. Fig. 5 shows that
the proposed model is modified by adjusting the exponential of the
polynomial I (a) of Eq. (8) from a value of 1.5–1.15, resulting in a
better approximation of the curve of the experimental results,
coinciding with maximum variations of 10%, while the proposed
model without modification presents variations greater than 10%.
These results also show that for intercept factors greater than
0.9, the proposed modified model coincides with maximum variations
of 1%. This result is adequate because the intercept factor is
used precisely in this range as in this range, reductions in the heat
losses caused by the excessive size of the opening of the cavity receiver
are achieved.
The validation process of the thermal model is performed by
comparing the experimental results reported for the 10 kW cavity
receiver CNRS-PROMES system and the results obtained from simulation
of the thermal model for this purpose. The thermal and
geometric features of the 10 kW receiver CNRS-PROMES system
(focal length 4.5 m, diameter 3.8 m parabola, reflector) [32] are
introduced in the simulator. According to [15], this type of receptor
is most appropriate for validating low-power receivers. Table 1
shows that the results of the proposed model are in the range
established with respect to the experimental values. It is clear that
the losses are not compared by conduction because this system
considers the losses by conduction within the losses due to convec