Civil Engineering Reference
In-Depth Information
portion) is reflected evenly by the LightLouvers™ to the ceiling surface 6.
The remaining 10% is assumed to be inward diffuse radiation from the
daylighting glazing/LightLouver™ combination. All transmitted solar
radiation throughtheotherwindowsisassumedtobeperfectlydiffusesince
thewindowsaredesignedtoavoiddirectbeamradiation.Thereflectedsolar
radiation from surface 6 is also considered to be perfectly diffuse. Assumed
surface reflectances are summarized in
Table 7.16
.
Table 7.16
Reflectance of different surfaces (
Figure 7.60
)
used in radiant
heat transfer calculations with radiosity method.
Type of
Radiation
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Visible 0.7 0.7 0.2 0.2 0.2 0.7 0.7 0.7 0.2 0.2 0.2 0.2 0.7 1 1
Solar 0.3 0.3 0.2 0.2 0.2 0.4 0.4 0.4 0.6 0.5 0.5 0.5 0.3 1 1
Long wave 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 1 1
Surface Number
Daylighting Model
The Perez model (Perez
et al.
, 1990) is used to estimate the exterior
illuminance on façades based on beam and horizontal diffuse radiation. The
treatment of transmitted and reflected daylight is the same as described
in the preceding paragraph for solar radiation - perfectly diffuse. Using
the radiosity enclosure and the initial diffuse luminous exitances on each
surface, average workplane illuminance is calculated. Configuration factors
have not been used because illuminance at specific points is not considered
in this case.
7.4.3.2 Model Validation and Calibration
The measured data (
Figure 7.54
to
Figure 7.56
)
are used to calibrate the
thermal model.
Figure 7.63
compares the simulation results from the
calibrated thermal model to the measured data. Comparison indicates that
the interzonal convection correlation (
Eq. (7.7)
) is accurate. The effective
thermal capacity of the room control volume is about 50 to 60 times the
room air thermal capacity. Acoustic panels are estimated to weaken the heat
exchange rate (by about 50%) between the ceiling slab and office space.
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