The correction factors of cooling power
−
and input power take into account
the presence of glycol and diverse
evaporation temperatures.
The pressure drop correction factor
−
considers the different flow rate
resulting from the application of the
water flow rate correction factor.
Correction factor of water flow rate is
−
calculated to keep the same
∆
t that
would be present with the absence of
glycol.
NOTE
On the following page an example is given
to help graph reading.
to determine the percentage of glycol
required, see below diagram; this
percentage calculation can take into
consideration one of the following factors:
Depending on which fluid is considered
(water or air), the graph is interpreted
by the right or left side at the crossing
point on the curves with the external
temperature line or the water produced
line. A point from which the vertical line will
pass is obtained and this will distinguish
both glycol percentage and relative
correction coefficients.
HOW TO INTERPRET GLYCOL
12.1.
CURVES
The curves shown in the diagram
summarise a significant number of data,
each of which is represented by a specific
curve. In order to use these curves
correctly it is first necessary to make some
initial reflections.
If you wish to calculate the percentage
−
of glycol on the basis of the external
air temperature, enter from the left
axis and on reaching the curve draw a
vertical line, which in turn will intercept
all the other curves; the points obtained
from the upper curves represent the
coefficients for the correction of the
cooling capacity and input power, the
flow rates and the pressure drops
(remember that these coefficients
must be multiplied by the nominal value
of the size in question); while the glycol
percentage value recommended to
produce desired water temperature is
on the lower axis.
If you wish to calculate the percentage
−
of glycol on the basis of the temperature
of the water produced, enter from the
right axis and on reaching the curve
draw a vertical line, which in turn will
intercept all the other curves; the
points obtained from the upper curves
represent the coefficients for the
cooling capacity and input power, the
flow rates and the pressure drops
(remember that these coefficients
must be multiplied by the nominal
value of the size in question); while the
glycol percentage value recommended
to produce water at the desired
temperature.
Initial rates for “EXTERNAL AIR
−
TEMPERATURE” and “TEMPERATURE
OF PRODUCED WATER”, are not
directly related, therefore it is not
possible to refer to the curve of one of
these rates to obtain corresponding
point on the curve of the other rate.
ETHYLENE GLYCOL SOLUTIONS
12.
KEY:
FcGPf
Corrective factors for cooling capacity
FcGPa
Corrective factors of the input power
FcGDpF (a) Correction factors for pressure drop (evaporator) (av. temp. = -3.5 °C)
FcGDpF (b) Correction factors for pressure drops (av. temp. = 0.5 °C)
FcGDpF (c) Correction factors for pressure drops (av. temp. = 5.5 °C)
FcGDpF (d) Correction factors for pressure drops (av. temp. = 9.5 °C)
FcGDpF (e) Correction factors for pressure drops (av. temp. = 47.5 °C)
FcGQF
Correction factor of flow rates (evap.) (av. temp. = 9.5 °C)
FcGQC
Correction factors of flow rates (condenser) (av. temp. = 47.5 °C)
NOTE
Although graph shows up to external air temperature of -40°C, unit opera-
tional limits must be considered.
2.20
2.10
2.00
1.90
1.80
1.70
1.60
1.50
1.40
1.30
1.20
1.10
1.00
0.99
0.98
0.97
0.96
0.95
0.94
5
0
-5
-10
-15
-20
-25
-30
-35
-40
0
5
10
15
20
25
30
35
40
45
50
55
-6
0
5
0.975
0.990
1.000
1.090
1.110
1.180
1.280
1.310
1.390
-3
FcGPf
FcGPa
FcGPf (PdC)
FcGQ (PdC)
FcGDpF (e)
FcGDpF (d)
FcGDpF (c)
FcGDpF (b)
FcGDpF (a)
FcGQF
tem
per
atur
e of pr
oduced wat
er
ext
er
nal air t
em
per
atur
e
Glycol %
25
