This issue is sponsored by the Philips Romania, Lighting Division

C Ţicleanu
horizontal illuminance within the axis of
the main light-pipe was measured at certain
distances from the diamond dome. In order
to assess the potential of light distribution
through the horizontal branches, vertical
illuminance on the inner wall of the lightpipe
was measured at certain distances from
the diamond dome.
Basing on these values, a recurrence law
was found to predict the illuminance at a
certain point of the light-pipe for a certain
value of the external horizontal illuminance
at roof level.
If E0 is the external horizontal
illuminance at roof level, then the
horizontal illuminance Eh,l within the lightpipe
axis at the distance l from the diamond
dome will be
Eh , l = E0
− ϕ()
l (4)
where ϕ(l) is the recurrence function
determined using the CurveExpert 1.3
software based on the Levenberg-
Marquardt method of nonlinear regression.
The same applies for the vertical
illuminance Ev,l on the inner wall of the
main light-pipe, which at the distance l
from the diamond dome will be
Ev , l = E0
−ψ
() l (5)
where the recurrence function ψ(l) was
determined using the same method as
above.
Beside the light transmission of the main
light-pipe, the transmission characteristics
of the secondary branch pipe were assessed.
Basing on the same algorithm, the
illuminance Ebδ at the distance δ from the
ramification within the axis of the branch
was expressed as a function of the initial
illuminance Eb at the entrance in the branch
and the distance δ:
42
INGINERIA ILUMINATULUI 18-2006
( δ )
E b,
δ = Eb
− β
(6)
where the recurrence function β(δ) results
using the same algorithm as for the main
light-pipe.
The first measurements were taken using
a 75 W incandescent lamp as the light
source for the main duct. The illuminance
within the axis of the light-pipe at the
distance L=23 cm from the lamp socket’s
base plane was considered as the initial
illuminance E0. Several measurements were
taken and the mean values are shown in the
table below.
Horizontal illuminance within pipe axis
L, cm l, cm Eh,l, cm ΔEh, cm
23 0 31,500 0
33 10 29,533 1967
43 20 28,467 3033
53 30 27,733 3767
63 40 25,833 5667
73 50 24,333 7167
Vertical illuminance on pipe’s inner wall
L l Ev,l ΔEv
23 0 12,000 19,500
33 10 9750 21,750
43 20 8850 22,650
53 30 8425 23,075
63 40 8150 23,350
73 50 7875 23,625
L is the distance from the socket’s base
plan at which the horizontal and vertical
illuminances Eh,l and Ev,l are measured, l is
the length at the measurement point relative
to the point where the initial illuminance E0
is measured, and ΔEh and ΔEv are the
differences of illuminance E0–Eh,l and E0–
Ev,l respectively.
In order to see the light amplification
effect specific to the SunPipe, the table
below shows the illuminance generated by