Airedale EcoChill 6kW - 46kW - Manual (Page 30)

30
EcoChill Chiller
Technical Manual 7300221 V1.1.0_02/2013
9. ETHYLENE GLYCOL
SOLUTIONS
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.
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.
Using the diagram below it is possible
to determine the percentage of glycol
required; this percentage can be
calculated by taking of the following
factors into consideration one:
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
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 “Water
Temperature °C”, 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:
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 the graph arrives at external air temperatures 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
W
ater T
emperature °C
External air temperature
Glicol%