Ethylene Glycol Solution - AERMEC NRA 2000 Manual Tecnico

The cooling capacity and input power
correction factors make allowance for
the presence of glycol and the different
evaporation temperature.
The correction factors of the water
flow rate and the pressure drops are
applied directly to the data obtained
for operation without glycols. 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 glycols.
- The cor r ection f act or of t he
pressure drop already takes into
account the dif ferent capacity
deriving from the application of the
water flow rate correction factor.
- The correction factors of the water
flow rate and the pressure drops
are applied directly to the data
obtained for operation without
glycols.
- The correction factors of the cooling
and input capacities take into
18

ETHYLENE GLYCOL SOLUTION

8
account the presence of glycols.
- The correction factors of the water
flow rate and the pressure drops
are applied directly to the data
obtained for operation without
glycols.
- The correction factor of the water
flow rate is calculated so as to
maintain the same Dt that would be
used in the absence of glycols.
- The cor r ection f act or of t he
pressure drop already takes into
account the dif ferent capacity
deriving from the application of the
water flow rate correction factor.
NOTE
To make it easier to read the graph, an
example is given on the next page.
By using the diagram opposite 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.
8. 1 HOW TO READ
THE GLYCOL CURVES
The cur ves 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 t o calculat e t he
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 ver tical line
which, in turn, will intercept all the
KEY:
FcGPf Correction factor of the
cooling capacity
FcGPa Correction factor of the
input power
FcGDpF (a) C o r r e c t i o n f a c t o r o f
t h e p r e s s u r e d r o p s
(evaporat or) (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
o u t p u t s ( e v a p o r a t o r )
(average temp. = 9.5°C)
FcGQC Correction factor of the
o u t p u t s ( c o n d e n s e r )
(average temp. = 47.5°C)
NOTE
Although the graph reaches
outside air temperatures of -
40°C, it is necessary to maintain
the machine's operating limits as
reference.