− The corrective factors of cooling
capacity and input power take into
account the presence of glycol
and the difference in evaporation
temperatures.
− The pressure drop correction factor
considers the different flow rate
resulting from the application of the
water flow rate correction factor.
− The water flow rate correction factor
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 diagram below; 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.
10.13. HOW TO INTERPRET GLYCOL
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
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 lower axis recommends the
glycol percentage value necessary
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.
KEY:
Pc Corrective factors for cooling capacity
Pe Corrective factors of the input power
Ph Corrective factor for heating capacity
ΔP (1) Corrective factor for pressure drops with an average fluid temp. = -3.5 °C)
ΔP (2) Corrective factor for pressure drops with an average fluid temp. = 0.5 °C)
ΔP (3) Corrective factor for pressure drops with an average fluid temp. = 5.5 °C)
ΔP (4) Corrective factor for pressure drops with an average fluid temp. = 9.5 °C)
ΔP (5) Corrective factor for pressure drops with an average fluid temp. = 47.5 °C)
Qw (1) Corrective factor for pressure drops (evap) with an average fluid temp. = 9.5 °C
Qw (2) Corrective factor of flow rates (condenser) with an average fluid temp. = 47.5 °C
NOTE
Although the graph shows a max external air temperature of -40°C, the unit
operational limits must be complied with.
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
05101520
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
temperature of produced water
external air temperature
Glycol %
Corrective factors
11. ETHYLENE GLYCOL SOLUTIONS
41
IWRLTY. 1201. 5890974_06
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