164
Ip(ay)
o'2
KeIn IgfAy)
Ke In Iptay)
Igy) —vwn——
R1
=|)
=
Tgl))
Amp.
ajo
,
IgQ2)e—Ww—>
Igtho)
Ke In Pa
Biz? Ina
o'1
Diff,
Igihy) Tog)
fain =
Ipihy)
€
Ry
Numerator
Tythg}e- —wa—
Ri
© IofA,)
i woe!
we. Th)
>
Denominator
Ir)
Ke in Ipaq)
€
+!
—|
Diff.
I]
Ky In TpQy)
+|
Ty(A}) wt
.
Diff.
Amp.
Ry
Xa
Ke In ec)
Bu2
Diff.
Amp.
+.
a
a
Divider
In
yy) yoy)
IpQ>) |
ez,
Tp (hy)
Ke
9 A
" Tp)
Fig. 131,—-Cireuit diagram for providing a continuous reading of the mixing depth in the case of uniform mixing using twopairs
of pyrheliometers, with one of the two pyrheliometers in each pair operating in one wave band and the other in a different wave band.
“a = kz,
where & is a constant and z is measured in the vertical
direction with positive upward.
The basic differential equation then becomes (see
Figure 129)
dl = —ywdb = —kzed
L = —kz sec 6 dz.
I
Integrating between the limits of the top of the build-
i
i
p
0
in ZZ
Ip _ —k sec 02
Ty
2
or
2")
= Iy exp (-a-5
— *(sec aep.
24
(24)
Three Pyrheliometers at One Wave Band and One
Zenith Distance
If we use three pyrheliometers, each at a different
level, it is possible to determine an effective height of
We maythen write
(23)
I, = Ig exp {ne _f = @ \
where Zp = intensity of solar radiation at top of the
mixing Jayer and z is measured from the top of the
layer.
If we express
Ip = foe7*
—(k/2) see @ z2
the mixing layer instantaneously and without filters
under the assumption that the concentration decreases
linearly with height. If we are dealing with a tall building, we may place one pyrheliometer at the ground denoted by subscript B; one at an intermediate level (JZ);
and one at the top (T). (See Figure 132.)
—k seco | zdz
Ir = Ip exp {Eeeee a},
I> = Toe *
(22)
ing and the top of the mixing layer we have
LF
where 7, = the solar constant for all-band radiation,
and @ is a constant, we have
(25)
' or
Ip = In exp(
k
o\
—a — 5 (cos aL
(26)