The comparison of the predicted results and experimental results are shown in Figs. 24–27. The results shown in Fig. 24 are for the clear glass window installed with the black venetian blind with slat angle of +45 degree.
In the morning (6.00–13.00) the incident radiation mostly comes from the diffuse radiation, therefore the transmittance in
this period is referred to in the figures as the solar transmittance (diffuse).
In the afternoon the incident radiation comes from both the direct radiation and diffuse radiation therefore the transmittance in this period is referred to in the figures as the solar transmittance (total).
The results from the prediction agree very well with the results from experiment except some discrepancy around 11.00–13.00.
The results shown in Figs. 25–27 are for the clear glass window installed with the white venetian blind having slat angle of +45, 0 and 40 degree, respectively.
The results from the prediction agree quite well with the results from experiment for blind with slat angle of 0 and 40 degree.
There are some discrepancy between the results from the prediction and experiment clearly seen in the morning (6.00–13.00) (the incident radiation mostly comes from the diffuse radiation) for the blind with slat angle of +45 degree.
The main difference between the black and white venetian blind is its slat reflectance.
It can be said that the developed mathematical model of the blind for diffuse radiation may not be quite accurate in the case of high reflectance blind (white blind has reflectance of 0.82 while black blind has reflectance of 0.1).
One should also note that the parameter used for validation in this analysis is the solar transmittance which is the ratio of the transmitted radiation through the glass window with blind system to the incident radiation on the glass window.
Since the magnitude of diffuse radiation incident on the glass window in the morning is much lower compared to the magnitude of the total solar radiation incident on the glass window in the afternoon therefore the same different value of solar transmittance between the predicted results and experimental results in the morning and in the afternoon shown in the figures does not represent the same absolute error predicted by the mathematical model.
This kind of discrepancy is not found for the blind with low reflectance blind like the black color blind shown in Fig. 24.
The results predicted from the mathematical model in the afternoon (the incident radiation mainly comes from the direct radiation) agree quite well with the results from experiment in all cases (low and high reflectance blind, blind with different slat angle shown in Figs. 24–27).
All discrepancy values except ones in Fig. 25 are within the experimental uncertainty 0:05 (Chantrasrisalai and Fisher, 2006).
The discrepancy in the compared results in the morning shown in Fig. 25 (slat angle of +45 degree) may come from the inaccurate model in diffuse radiation from the ground effect that sensitive to a high reflectance slat since this same problem does not show on the same blind with different slat angle.
More works need to be done to confirm this deviation. And when compared the predicted results shown in Figs. 24–27 with
the comparison results from Parmelee, Pfrommer and Energyplus model in Chantrasrisalai and Fisher (2004),one can clearly seen the results from the developed optical model that included the effect of slat curvature and thickness from the beginning gives much more accurate predicted results.
From the study, it can be said that the developed mathematical model of the effective layer for the curved blind with thickness gives a rather accurate result.