12. GLYCOL
−
The cooling capacity and input
power correction factors make al-
lowance for the presence of glycol
and the different evaporation tem-
perature.
−
The pressure drop correction factor
already takes into account the
different flow rate deriving from the
application of the water flow rate
correction factor.
−
The correction factor of the water
flow rate is calculated so as to
maintain the same
∆
t that would be
used in the absence of glycol.
NB
An example is given to make it easier
to read the following graph.
By using the diagram below it possible
to establish the percentage of glycol
necessary; this percentage can be
calculated taking into account one of
the following factors:
On the basis of the fluid considered
(water or air), it will be necessary to en-
ter the graph from the right or left side,
from the intersection of the outside
air temperature or processed water
temperature straight lines and the rela-
tive curves, a point is obtained through
which the vertical line that will identify
both the percentage of glycol and the
relative correction coefficients will have
to pass.
12.1. HOW TO READ THE GLYCOL
CURVES
The curves shown in the figure summa-
rise a notable quantity of data, each
of which is represented by a specific
curve. In order to use these curves
correctly, it is necessary to make some
initial considerations:
−
If you want to calculate the per-
centage of glycol on the basis of
the outside air temperature, you
must enter from the left-hand axis
and, once you have intersected
the curve, trace 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,
for the flow rates and the pressure
drops (remember that these coef-
ficients must anyway be multiplied
by the rated value of the sizes
examined); the lower axis advises
the percentage of glycol necessary
on the basis of the outside air tem-
perature considered. If you want to
calculate the percentage of glycol
on the basis of the temperature
of the processed water, you must
enter from the right-hand axis and,
once you have intersected the
curve, trace a vertical line which,
in turn, will intercept all the other
curves; the points obtained from
the upper curves represent the co-
efficients for the cooling capacity
and input power, for the flow rates
and the pressure drops (remember
that these coefficients must anyway
be multiplied by the rated value of
the sizes examined); the lower axis
advises the percentage of glycol
necessary to produce water at the
required temperature.
−
Remember that the initial sizes
“OUTSIDE AIR TEMPERATURE” and
“PROCESSED WATER TEMPERATURE”,
are not directly linked to each
other, so it is not possible to enter
the curve of one of these sizes, and
obtain the corresponding point on
the other curve.
KEY:
FcGPf
Correction factor of the cooling capacity
FcGPa
Correction factor of the input power
FcGDpF (a) Correction factor of the pressure drops (evaporator) (average temp. = -3.5°C)
FcGDpF (b) Correction factor of the pressure drops (average temp. = 0.5°C)
FcGDpF (c) Correction factor of the pressure drops (average temp. = 5.5°C)
FcGDpF (d) Correction factor of the pressure drops (average temp. = 9.5°C)
FcGDpF (e) Correction factor of the pressure drops (average temp. = 47.5°C)
FcGQF
Correction factor of the outputs (evaporator) (average temp. = 9.5°C)
FcGQC
Correction factor of the outputs (condenser) (average temp. = 47.5°C)
NB
Although the graph reaches outside air temperatures of -40°C, it is necessary to maintain
the machine's operating limits as reference.
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
Processed water temperature
Outside air temperature
% Glycol
28
INXWPY. 1004. 4438805_00
