Ethylene Glycol Solution; Pressure Drops - AERMEC NSB Serie 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 correction factor of the pressure
drop already takes into account the
different 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
account the presence of glycols.
20

ETHYLENE GLYCOL SOLUTION

8
- 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 correction factor of the pressure
drop already takes into account the
different 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 vertical line which,
in turn, will intercept all the other
curves; the points obtained from the
upper curves represent
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.