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ManualsBrandsCaleffi ManualsAir Eliminators2" Flanged 546 Series DISCALDIRT Commercial Steel Air and Dirt Separator
123456
The process of air formation
The amount of air which can remain dissolved in a water solution is
a function of pressure and temperature. This relationship is
governed by Henry’s law and the graph demonsrates the physical
phenomenon of the air release from water. As an example, at a
constant absolute pressure of 30 psi (2 bar), if the water is heated
from 65ºF (18ºC) to 170ºF (75ºC), the amount of air released by the
solution is equal to 1.8 gallons of air per 100 gallons of water.
According to this law it can be seen that the amount of air released
increases with temperature rise and pressure reduction. The air
comes in the form of micro-bubbles of diameters in the order of
tenths of a millmeter.
In heating and cooling systems there are specifi c points where this
process of formation of micro-bubbles takes place continuously in
the boiler and in any device which operates under conditions of
cavitation.
Solubility of air in water
Separation efficiency
The capacity for separating the impurities in the medium circulating
in the closed circuits of the systems basically depends on three
parameters:
1) It increases as the size and mass of the particle increase.
The larger and heavier particles drop before the lighter ones.
2) It increases as the speed decreases. If the speed decreases,
there is a calm zone inside the dirt separator and the particles
separate more easily.
3) It increases as the number of recirculations increases.
The medium in the circuit, fl owing through the dirt separator a
number of times during operation, is subjected to a progressive
action of separation, until the impurities are completely removed.
The special design of the internal element in the Caleffi
DISCALDIRT air and dirt separator, is able to completely separate
the impurities in the circuit down to a minimum particle size of 5 µm
(0.2 mil).
Boiler micro-bubbles
Micro-bubbles are formed continuously on the surface separating
the water from the combustion chamber due to the fl uid
temperature. This
air, carried by the
water, collects in
the critical points
of the circuit from
where it must be
removed.
Some of this air is
reabsorbed in
the presence of
colder surfaces.
Cavitation and micro-bubbles
Micro-bubbles develop where the fl uid velocity is very high with the
corresponding reduction in pressure. These points are typically the
pump impeller
and the valve
port.
These air and
vapor micro-
bubbles, the
formation of
which is
enchanced in
the case of
non deaerated
water, may
s u b s e q u e n t l y
implde due to
the cavitation
phenomenon.
Max amount in gallons of dissolved air per 100 gallons of water
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
15 psi
30 psi
45 psi 60 psi 75 psi 90 psi 105 psi 120 psi
Absolute pressure
Water temperature (∞F)
32 65 100 135 170 205 240 275 310 345
Flame temperature
1800∞F (1000∞C)
Wall temperature
320∞F (160∞C)
Combustion chamber wall
Boundary layer
Average water
temperature 160∞F (70∞C)
Boundary layer
temperature 313∞F (156∞C)
FLAME WATER
Micro-bubbles
Pressure
Velocity
Cavitation
micro-bubbles
Pressure Velocity
Implosions
Seat-obturator
distance
Fluid vapour
pressure
Particle separation rating - Dirt separator efficiency
Tests in a specialized laboratory
TNO - Science and Industry (NL)