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14. GLYCOL

−

The cooling capacity and input

power correction factors make
allowance for the presence of
glycol and the different evaporation
temperature.

−

The pressure drop correction factor

already takes account of 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.

NOTE
To make it easier to read the following
graph, an example is given.
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 enter the graph from the right or
left side, from the intersection of the
outside air temperature or processed
water temperature straight lines and
the relative 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.

14.1. HOW TO READ THE GLYCOL

CURVES

The curves shown in the figure
summarise 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

percentage 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 coefficients must anyway
be multiplied by the nominal value
of the sizes examined); the lower
axis advises the percentage of
glycol necessary on the basis of the
outside air temperature 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 coefficients
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 nominal 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)