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1205. 6755517_02

•

The correction factors of cooling power

and input power take into account the

presence of glycol and diverse evapora-

tion 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 Δt 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 per-
centage 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 tempe-
rature 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 correc-
tion coefficients.

11.5. How to INterPret gLYCoL CUrVeS

The curves shown in the diagram summarise a signifi-
cant 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.

1. 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 coeffi-

cients 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 re-

commended to produce desired water

temperature is on the lower axis.

2. 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 repre-

sent 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

3. 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 “TEMPERATURE OF PRODUCED WATER”, 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.

12.

etHYLeNe gLYCoL SoLUtIoNS

KEY:
Pc

Corrective factors for cooling capacity

Corrective factors of the input power

Corrective factors of heating capacity

∆

p (1) Correction factors for pressure drop av. temp. = 25,7°F / -3,5°C

∆

p (2) Correction factors for pressure drop av. temp. = 32,9°F / 0,5°C

∆