Note: Descriptions are shown in the official language in which they were submitted.
393
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1 FA~ CYLII~DER ~VI~IG
INVISIBLE EASED INLET
-
This invention relates to air moving
mechanism of the type which has particular utility
in heat exchange equipment and provides increased
operating efficiency at lower cost for units such
as induced draft direct or indirect cooling towers.
Heat exchangers of the finned tube type
as well as evaporative water cooling towers have
long used direct and induced draft fan assemblies
for directing cooling air through the heat ex-
change zones of the apparatus to increase thermal
interchange at minimum cost and in the least
amount of space. Most evaporative water cooling
equipment initially depended upon convective air
currents enhanced by stacks which depended on
natural draft for air movement. This required the
fabrication of extremely high chimneys to produce
dependable air movement under varying ambient
conditions, particularly in geographical area
where high.temperatures were encountered for
critical or extended periods of time. Also, as
fan and electric motor designs became more ef-
ficient and dependable, means was presented for
moving cooling air through the evaporative or dry
thermal exchange séctions of the cooling apparatus
on demand, at predetermined flow rates and vol-
: umes, and at feasible operating costs. Further-
more, the use of fan driven air currents through
the cooling units permitted fabrication of compact
apparatus which not only could be sized accurately
for particular thermal requirements, but also
allowed location thereof in advantageous positions
for optimum cooling without creating attendant
aesthetic problems.
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1 Although for the most part forced draft
fans were initially used to direct cooling air
through evaporative and dry thermal interchange
sections, induced draft fan mechanisms are used
primarily today because of greater effectiveness
attributable to the more uniform air distrib~tion
which is obtained over the entire area of the
cooling section, and improvement in recirculation
resistance inherent in designs which force the hot
air away from the inlet of the cooling equipment
to the greatest possible extent.
Squirrel-cage type centrifugal blowers
have found application in many types of evapora-
tive or dry surface cooling towers because of
their quiet operation and ability to impart the
necessary velocity to the air entering the units.
However, rotary fans having a series of radial
blades have found greatest acceptance because of
their ability to deliver large volumes of air at
low static head (nominal 3/4 in. water or less).
Propeller fans are used almost exclusively on
large towers for outdoor installations because of
their lower cost than other types of air moving
devices, and the fact that they may be used on any
size tower and are particularly suited to cooling
tower usage where low draft losses prevail.
Properly designed fan cylinders having propeller
fans therein operate at efficiencies as high as
80%. Typically, fans of this type will have
diameters ranging from about 2 feet up to 30 - 40
-feet.
In a conventional evaporative water
cooling tower of the induced draft type, a single
propeller-type fan rotatable in a fan cylinder
therefor which discharges vertically into the
35~3
l atmosphere is located above a plenum chamber of a
casing that has two opposed fill sections therein
which receive air from diametrically opposed,
upright air inlets. I~ater to be cooled is gravi-
tationally delivered to the upper plan areas of
the fills and permitted to flow downwardly therein
before being collected in a cold water basin at
the bottom of the tower. Air pulled into the
casing of the tower intersects the gravitating
water in what is termed "crossflow relationship"
and then forced outwardly and upwardly through the
fan cylinder mounted at the top of the tower
casing. Drift eliminators over the inboard
upright faces of the opposed fill assemblies serve
- 15 the dual function of removing entrained water
droplets from the air before discharge thereof,
and turning the air from its initial essentially
horizontal path to an upward vector leading in an
essentially straight line toward the inlet of the
fan cylinder. It can be appreciated in this
respect though that the air moving in crossflow
fashion through the fill assemblies adjacent the
upper hot water distribution basins is moving in
an essentially radial direction with respect to
the fan, whereas air entering the plenum between
the fill units at the lower ends thereof is more
axially oriented with respeGt to the fan cylinder
as it leaves the fill and travels toward the air
outlet. The result is that the component of
velocity of air parallel to the fan axis at the
upper part of the casing plenum is substantially
lower than that of the air coming from the bottom
of the tower.
In addition, air is pulled into the
tower from opposite sides of the casing and
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393
1 delivered to the plenum zone from upright rec-
tangular areas in direct facing relationship, thus
creating an inherent imbalance insofar as delivery
of air to the circular fan and cylinder is con-
S cerned since supply of air to the perimeter of the
fan unit is from different directions and non-
uniform. Fan starvation can result around the
circumference thereof, as well as at the inboard
segments of the blade.
It has been known for a long time that
smooth flow of air into a fan cylinder equally
around the perimeter thereof must be provided for
most efficient operation. Since air flowing
essentially radially at the upper end of the tower
must be turned to a greater extent than air de-
livered to the fan cylinder from the lower section
of the casing, it can be appreciated that there
would be a tendency to stall the tips of the
blades unless means is provided to assure uniform
transition of the air streams into the ultimate
axial path thereof through the fan. Tests over
the years ultimately confirmed that most efficient
fan operation is assured by use of what has become
known in the art as an eased inlet. But since fan
performance is sensitive not only to inlet airflow
conditions but also fan tip blade clearance, it
necessarily follows that the inlet structure must
provide for minimum clearance with the blade tips
while at the same time allowing air to smoothly
enter the inlet from all directions. Various
configurations of fan opening structure may be
advantageously employed in this respect to in
effect "seal" the tips of the blades against
inefficient leakage of air.
Furthermore, i~ i9 desirable alth~u~h
~1183~33
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1 not essential to operability of this invention
that the fan inlet also be accompanied by an
upright or outwardly extending stack generally
termed a fan cylinder which serves as an enclosure
around the fan to effectively improve fan per-
formance. It necessarily follows that a structure
of substantial size must be fabricated and mounted
on the tower, usually at the upper end of the
casing in the case of vertical discharge, rela-
tively large towers. Oftentimes, these cylinders
can be relatively massive in size for large
diameter fans (30 to 40 ft.) employed in high
water volu~e cooling towers. In addition, in view
of the fact that most industrial towers are of the
multicell type wherein a long line of side-by-side
fill assemblies are served by respective fan
units, avoidance of hot air recirculation is an
essential requirement necessitating fan cylinders
of considerable height. These cylinders must not
only be constructed of materials which withstand
the corrosive atmospheres in which they operate,
but must also be rugged enough to withstand the
vibration induced by pulsating air flows. Re-
covery stacks for large scale industrial water
cooling towers are often 15 - 20 feet in height
where large diameter fans are utilized. The eased
inlet of the fan cylinders leading to the oper-
ating area of the fan blades desirably are of a
logarithmic curved configuration but for practical
reasons usually are fabricated as elliptical
-surfaces which approximates the theoretical
optimum contour.
Although curvilinear eased inlets offer
operating advantages, fabrication can be expensive
if other requirements such as corrosion resistance
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l and inherent strength are satisfied for a particu-
lar applica~ion. Compound curves are difficult to
fabricate using metal; and reinforced synthetic
resin designs not only are costly to mold, but
must be specially shaped and reinforced to provide
adequate strength. Exemplary fan cylinders
fabricated of wood and embodying eased inlets for
improving fan performance are found in U.S.
Patents Nos. 2,681,178, No. 2,681,179, and No.
2,814,435, all assigned to the assignee hereof.
These wooden cylinders, although corrosion re-
sistant, were subject to deterioration over a
period of time by virtue of the humid conditions
under which they normally operated, and not only
were costly, but not as aesthetically pleasing to
the eye as desired. Glass reinforced polyester fan
cylinders have, for the most part, replaced earlier
wood struetures but here again, although deterior-
ation is not the problem encountered with wood,
they are still subject to limitations, particu-
larly wind damage deflection by strong wind gusts
which can cause the blade tips to ~ouge through
the inner wall of the cylinder and destroy the
blade tip as well as part of the enclosure struc-
ture. Relatively high initial cost is a major
deterrant to widespread usage of synthetic resin
fan cylinders. Exemplary structures of this type
are illustrated in the assignee's U.S. Patents
Nos. 3,708,155, and 3,780,999.
It has now been discovered that fan
inlet structure may be provided for units such as
wet or dry surface cooling towers which may be
fabricated of corrosion resistant materials such
as metal, plastics or concrete without the neces-
sity of providing compound curves therein, all at
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1 a subs~antially lower cost than heretofore possible
in equipment of this size, and providing optimum
efficiency even in instances where airflow veloci-
ties and directions of air travel toward the fan
cylinder are not equal throughout the air delivery
zone. Others have disclosed fan cylinder struc-
ture which attempts to do away with the necessity
of providing a compound curve eased inlet, but
none of these prior efforts have addressed them-
selves to the need to modify the vena contracta of
the airflow into the inlet so that it fully fills
the fan cylinder without stalling of the blades
regardless of the variations in air velocities and
directions of supply thereof to the fan. An
exemplary noncurved eased inlet for fans is
illustrated in U.S. Patent No. 3,814,538, de-
picting two cylinders interconnected by a radial
flange with the fan being rotatable within one of
the cylindrical segments while the other is
outboard thereof in the direction of air supply.
The double ring configuration of the '538 Patent
does not allow for modification of the vena
contracta of the airflow into the primary cylinder
regardless of variations in airflow direction and
velocities leading into the fan. Equally as
important though is the fact that the structure of
this patent fails to really provide smooth transi-
tional movement of the air from the source into
the fan cylinder around the full perimeter thereof
without attendant blade starvation.
It is therefore the primary object of
the present invention to overcome the disadvan-
tages of the prior art and permit utilization of
an easily fabricatable and relatively inexpensive
right circular cylinder as an enclosure for the
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1 fan blades and utilizing an appertured baffle in a
strategic position ahead of the cylinder inlet for
modifying the airflow thereto in a manner to
assure circumferentially uniform flow of air into
the fan cylinder in substantially coaxial rela-
tionship with the axis of rotation of the fan
blades.
Another important object of the inven-
tion is to provide air moving mechanism as des-
cribed wherein uniform transition of air from a
source into the fan cylinder is assured even in
instances where the air is delivered to the fan
cylinder from zones which are essentially on
opposite sides of the center line of the fan, by
the simple expedient of modifying the shape of the
aperture in the baffle ahead of the fan to provide
a generally rectangular opening which has the
effect of modifying the vena contracta of the
airflow to an extent that the air enters the fan
cylinder substantially equally around the perimeter
thereof and in generally parallel relationship to
the axis of the fan. Also an important object of
the invention is to provide air moving mechanism
as mentioned above which may be used on cooling
towers of conventional design without significant
modification thereof being required, all at
reasonable cost while at the same time permitting
optimized fan performance. Another important
object of the invention is to provide air moving
mechanism for units such as cooling towers or the
.like wherein an invisible eased inlet for a fan
cylinder is formed by simply mounting a plate
ahead of the cylinder inlet with an orifice being
provided in the baffle plate of a size and shape
to control the vena contracta of the air delivered
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g
to the fan so as to cause the airflow entering the fan opening
to be of desired circular shape thus completely filling the
cylinder without stalling o the blades at any point around the
perimeter of the fan cylinder. In addition, variation of the
shape of the vena contracta of the flowing air may be accom-
plished by simply changing the relative position of the baffle
with respect to the fan, or in the alternative or as an adjunct,
changing the shape of the baffle orifice.
A further object of the invention is to provide air
moving mechanism of the characteristics defined which is usable
on various size cooling towers of either the wet or dry surface
type and which may be employed in either vertical or horizontal
orientation as desired and in cases where the source of air is
immediately aligned with the fan opening, to one side thereof,
or on opposite sides of the same.
Other objects of the invention will be explained or
become evident as the following description progresses.
The present invention can be defined, in general terms,
as an air moving mechanism comprising: structure defining
restricted, generally circular opening for passage of air there-
through, said opening communicating with a plenum zone from
which air is to be removed and leading to an area into which
the air is to be discharged, said zone having a cross-sectional
area transverse to the flow path of air therethrough which is
larger than that of said opening and defined by a non-circular
perimeter whereby throttling of the air must occur as it flows
from all parts of the zone toward the opening in said structure
and ultimate discharge to said area; means associated with said
structure for removing air from said zone, increasing the
velocity thereof as it flows toward and through said opening
in the structure, and directing such air into the area; air
throttling baffle means adjacent the opening in said structure
in spaced relationship therefrom toward the zone and provided
with a continuous edge surface defining a non-circular orifice
larger than the opening and having an overall shape geometr~c-
ally similar to that of said perimeter and through which the
air from the zone must pass in flowing toward the opening in
said structure, the edge portions of said baffle means being
positioned to project into those regions of the zone where
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- 9a -
the a:ir flow paths toward the opening from any boundary of
the zone are non-parallel to the axis of the opening; and
enclosure means operable associated with the structure and
said baffle means for preventing area derived air from flowing
5 to said opening without first passing through said zone and
thence the orifice in said baffle means, said orifice defining
edge surface of the baffle means being configured and arranged
relative to said opening in the structure and the baffle means
being positioned with respect to the opening in the struc~ure
in a location to cause air removed from said boundaries of the
zone to follow non-linear transition paths between the baffle
means and said opening which vary in angularity relatively to
an extent that such boundary derived air not only assumes
a generally circular pattern conforming to and substantially
fills the opening as the air flows into the structure and is
directed through the latter to said area but also enters the
opening in generally parallel relationship to the axis thereof.
In the drawings:
Figure 1 is a fragmentary perspective view of the
~0 upper part of a cooling tower showing air moving mechanism
embodying the preferred concepts of the present invention,
with parts thereof being broken away for clarity;
Figure 2 is a fragmentary plan view of the cooling
tower structure having air moving mechanism thereon as
depicted in Figure l;
Figure 3 is a fragmentary vertical cross-sectional view
of the cooling tower as is shown in Figure 2, with parts being
broken away for clarity and with certain components thereof
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393
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1 being shown schematically;
Figures 4, 5, 6 and 7 are fragmentary
cross-sectional views taken substantially on the
lines 4-4, 5-5, 6-6, and 7-7 respectively of
Figure 2;
Figure 8 is a fragmentary horizontal
cross-sectional view on the line 8-8 of Figure 3
and looking upwardly in the direction of the
arrow;
Figure 9 is a schematic vertical cross-
sectional view of another type of coolin~ tower on
which air moving mechanism of this invention may
be advantageously employed;
Figure 10 is a vertical cross-sectional
view taken on the line 10-10 of Figure 9 and
looking to the right as indicated by the arrows;
Figure 11 is a fragmentary, essentially
schematic, cross-sectional view of the upper part
of air moving mechanism comprising another embodi-
ment of this invention and showing structure
presenting an air passage opening and a rotary fan
in operable association with the structure wherein
~he blade tips of the fan are aligned with the
opening defining edge of the structure;
Figure 12 is a fragmentary, essentially
schematic, cross-sectional view of the upper part
of another embodiment of the invention similar to
that shown in Figure 11 but having the rotary fan
located in disposition such that the blade tips
are inside the opening defining structure and
extending beyond the edge thereof for enhancing
efficiency of the fan;
Figure 13 is a fragmentary, essentially
schematic, cross-sectional view of still another
embodiment of the invention similar to those of
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1 Figures 11 and 12 but having the fan blades located
outside of the structure and beyond the opening
de~ining edge thereof;
Figure 14 is a fragmentary, essentially
schematic, cross-sectional view of a further
embodiment of the invention like those shown in
Figures 11-13 wherein a pair of planar members
define the air passage opening and the blade tips
of the rotary fan extend between the members for
more effective fan operation;
Figure 15 is a fragmentary, essentially
schematic, cross-sectional view of an embodiment
of the invention similar to Figure 12 but em-
ploying a fan cylinder of the type shown j.n the
tower of Figures 1-3;
Figure 16 is a fragmentary, also gen-
erally schematic, cross-sectional showing of the
upper part of a further embodiment of the inven-
tion wherein air enters the structure from only
one side thereof and the air flow modifying
apertured baffle is inclined from the horizontal
to more effectively control air movement toward
the outlet opening of the structure; and
Figure 17 is a fragmentary, essentially
schematic, cross-sectional view of an embodiment
of the invention similar to that of Figuxe 16 but
differing therefrom in that air enters the struc-
ture from opposite side thereof and the apertured
air flow modifying baffle is configured to present
a double incline facing toward respective air
inlet to more precisely control air movement
toward the outlet opening of the structure.
Air moving mechanism according to the
preferred concepts of the invention is broadly
designated by the numeral 20 in Figure 1. This
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1 apparatus is especially useful in connection with
cooling towers of either the wet or dry surface
type. An evaporative-type water cooling tower
generally identified by the numeral 22 is shown in
Figure 3, and includes a casing 24 made up of
opposed side walls 26 and 28 centrally joined at
the upper ends thereof by an upper panel 30 having
depending opposed wall segments 32 and 34 which
are parallel and span the distance between side
walls 26 and 28 as is evident from Figures 2 and
3. A pair of open top hot water distribution
basins 36 are carried at the upper end of the
casing 24 on opposite sides of the air moving
mechanism 20 outboard of wall segments 32 and 34
respective.ly, and serve to gravitationally deliver
water to be cooled onto the upper plan area of
respective parallelepiped shaped fill assemblies
38 and 40 respectively. Water leaving the lower
ends of fill assemblies 38 and 40 is collected in
cold water basin 42 underlying the entire plan
area of casing 24. The inwardly and downwardly
inclined inner faces of the fill assemblies 38 and
40 have vertically spaced, horizontally oriented
eliminators 44 thereon which present respective
inclined stacks that function to remove entrained
water droplets from air passing through fill
assemblies 38 and 40 toward the central plenum
zone 46. The eliminators 44 are also transversely
inclined upwardly as shown in Figure 3 to enhance
turning of air toward the inlet of air moving
mechanism 20 and more uniformly distribute the air
throughout the extent of plenum zone 46. Although
cooling tower 22 has been shown as having opposed
evaporative sections 38 and 40, it is to be
appreciated that the invention hereof is useful
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1 for other applications involving only a single
thermal interchange section as for example shown
in Figures 9 and 10 to be described hereunder.
Similarly, the fill assemblies 38 and 40 are shown
schematically since they may be either of the
splash or film type, or conceivably could be dry
surface exchangers oriented substantially in the
disposition of upright inclined eliminator stacks
44, in vertical planes or in a horizontal plane.
A baffle member 48 in the form of a
planar sheet is provided at the top of casing 24
in overlying relationship to plenum zone 46 and
extending between side walls 26 and 2~ as well as
the upper ends of the eliminator stacks 44. In
fact, as shown in Figure 3, baffle member 48 may
comprise an éxtension of the perforated bottom
walls of respective hot water distributors 36. It
is also to be noted that the wall segments 32 and
34 projecting downwardly from panel 30 are joined
to the upper surface of baffle member 48 in air
sealing relationship thereto. The circular air
inlet 50 which is coaxial with the central upright
axis of plenum zone 46 is enclosed by a right
circular fan cylinder 52 oriented to discharge hot
air vertically back into the atmosphere. Fan 54
mounted within cylinder 52 and rotated about a
vertical axis through gear reducer and motor means
not shown, has a series of radial blades 56 each
provided with a square or round tip 56a which just
clears the inner surface of cylinder 52. It is to
be appreciated that the higher the fan efficiency,
the lower the sound level. It is also to be noted
from Figure 3, that fan 54 i~ oriented such that
a major part of the vertical extent of each of the
blade tips 56a is contained within the tubular
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1 expanse of cylinder 52. It is also apparent from
Figure 3 that panel 30 is in a plane perpendicular
to the axis of rotation of fan 54. The close
spacing of blade tips 56 to the inner surface of
cylinder 52 in substantial air sealing relation-
ship thereto is believed to be an important factor
in successful operation of air moving mechanism 20
utilizing an apertured baffle as the sole eased
inlet defining means. As illustrated in other
embodiments of this invention, various arrangements
of the blade tip relative to the air outlet may be
utilized to minimize air velocity losses at the
tips of the rotary fan blades.
In the instance where air moving mechanism
20 is used for a cooling tower having air inlets
on opposite sides of the tower casing, baffle
member 48 is provided with an arcuate, somewhat
square shaped orifice 58 therein which is coaxial
with the axis of rotation of fan 54 and centrally
located with reference to plenum zone 46 there-
below. As will be explained hereinafter, baffle
member 48 is preferably located in predetermined
disposition relative to the horizontal median
plane of rotation of blades 56. Also, orifice 58
is of a predetermined size and shape to assure
that air delivered to fan 54 is led into opening
50 and thereby cylinder 52 in such manner that no
zone of the fan blade area is starved of access to
incoming air.
If in this respect it is assumed that
air moving mechanism 20 is to be employed for an
evaporative-type cooling tower such as 22 wherein
air is pulled into the interior of casing 24 for
cross flow contact with water gravitatin~ down-
wardly in corresponding opposed fill assemblies 38
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l and 40 and then allowed to enter plenum zone 46
before being pulled upwardly toward the air mover,
it is preferred that orifice 58 be of the essen-
tially noncircular configuration as best shown in
Figures 2 and 8 of the drawings. As is most
apparent from Figures 2 and 3, air flowing through
the fill assemblies 38 and 40 cannot to any really
significant extent commence movement toward the
air discharge opening until leaving corresponding
eliminator stacks 44. As a consequence, the
airflow patterns from the fill assemblies 38 and
40 are essentially as depicted by the arrows A to
D inclusive of Figure 3. Airflow alongside the
casing walls 26 and 28 is generally more direct to
the fan. The same is true for air coming from the
lower central part of the tower casing. Because
of these different airflow patterns, it has now
been unexpectedly found that configuring orifice
58 of the shape shown in Figures 2 and 8 modifies
the air flowing toward the fan cylinder 52 or air
outlet opening to an extent that there is even
transition of such air into the outlet passage or
opening notwithstanding the non-uniform direction
of air toward baffle member 48.
In the case of a cooling tower where air
comes in from two opposed sides of the casing, an
optimized orifice 58 is thus defined by flattened
arcuate end edge portions 58a and 58b on opposite
sides of the axis 60 of fan 54. These edge
portions are joined to opposed side edge portions
58c and 58d by respective corner edge portions 58e
of greater arcuateness as is most evident from
Figures 2 and 8. The lip portions of planar sheet
member 48 defining edges 58a and 58b respectively,
are spaced a greater distance from axis 60 than
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1 the lip portions presenting edges 58c and 58d.
Edge portions 58e are of somewhat greater arcuate-
ness than edge sections adjacent thereto as is
most evident from Figures 2 and 8. The lip
portions of planar sheet member 48 defining edges
58a and 58b respectively, are spaced a greater
distance from axis 60 than the lip portions
presenting edges 58c and 58d. Edge portions 58a
and 58b are located above corresponding subzones
46a and 46b where airflow is more radial than
adjacent casing side walls 26 and 28 to assure
that cylinder 52 is filled uniformly with air
around the entire perimeter thereof.
For best performance, baffle means 48
in the form of a planar sheet should be spaced
from about 10% to approximately 50% of the di-
ameter of fan cylinder 52 away from inlet 50 or of
the fan opening if no cylinder is provided and
sealed to the baffle means 48 by structure such as
wall segments 32 and 34 which in conjunction with
upper extensions of side walls 26 and 28 present a
confined space 62 surrounding orifice 58. Best
results are obtained when the spacing of planar
member 48 is from about 10% to 20% of the fan
cylinder diameter away from inlet 50 or the
equivalent fan opening.
With particular reference to Figures 2
and 3, airflow through the left hand fill assembly
38 adjacent planar member 48 is designated by the
arrows A which it can be seen are essentially
radial with respect to the axis 60 of fan 54
before clearing the edge portion 58a of orifice 58
and then moving into fan cylinder 52 for discharge
to the area 64 above tower 22 via the outlet
opening 66 of fan cylinder 52. However, cross-
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1 flowing air emanating from the lower part of fill
assembly 38 adjacent the bottom region of elimi-
nator stack 44 and depicted by the arrows desig-
nated D tends to flow toward fan 54 in a more
axial direction than air path A, and as a conse-
quence, the air from zone 46a being directed to
the cylinder opening 50 from the lower part of the
lefthand fill is almost coaxial with the axis of
fan 54 as it enters the fan cylinder 52. Simi-
larly, as air leaves the eliminators 44 in a
direction from the top of the tower toward the
bottom thereof, it tends to progressively assume a
more axial direction from the radial path A as is
indicated by the arrows B and C successively lower
along the outlet face 68 of corresponding fill
assembly 38 and 40. In accordance with the
present invention, it has been determined that
where airflow is predominantly axial, the orifice
should be reduced. In areas where airflow is
predominantly radial, the orifice should be
increased. The shaping of orifice 58 may be
accomplished mathematically using derived equa-
tions from performance figures, or optimized from
empirical data wherein velocities near the inside
wall of the cylinder 52 at its inlet 50 are measured
and the orifice shaped until the values obtained
are nearly equal at all angular locations. Test
data in this connection may be generated by
measuring the flow rate of air through cylinder
52, for example at points 1/2 in. inside the
cylinder, 1 in. above cylinder inlet 50 and at
locations evenly spaced around the circumference
of the cylindrical enclosure.
Optimum shaping of orifice 58 and proper
spacing of planar member 48 from cylinder opening
1'11~393
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1 50 may be illustrated by the following example.
Utilizing a fan cylinder having a diameter of 36.4
in., it was determined that the distance from
sheet 48 to opening 50 should be about 5 3/4 in.
based primarily on geometrical structural con-
siderations. Using one 90 quadrant of cylinder
52 as a reference and starting from the 270
position (Fig. 8) and proceeding to the 360
position, 11 1/4 arcuate segments have been
designated by the numerals (1) to (9) inclusive.
If in the assumed structure the vertical height of
the fill units 36 and 40 is about 40 ]/2 in. and
the angle of each eliminator stack 44 is approxi-
mately 11.2 with the individual eliminators
thereby being at a 60 angle with respect to the
horizontal, airflow toward the fan cylinder would
be substantially along the lines depicted by
arrows A, B, C and D respectively of Figure 3.
Also assuming a plenum chamber having an overall
size of the order of 42 3/4 by 46 11/16 in hori-
zontal cross-section, and with the distance
between the lower ends of eliminators 44 being
about 16 inches, best results obtain when the edge
segments of orifice 58 at points (1) to (9)
inclusive are spaced horizontally from diamet-
rically opposite vertical projections of cylinder
opening 50 as follows: (1) 2.3 in.; (2) 2.55
in.; (3) 2.67 in.; (4) 2.61 in.; (5) 2.24 in.; (6)
1.55 in.; (8) 0.61 in.; and (9) 0.36 in. These
values were found to be optimum for any of a
number of airflow rates through the test fill as
defined.
In the operation of air moving mechanism
20, it is believed that special shaping of orifice
58 in baffle member 48 and location of the latter
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1 in predetermined relationship with respect to the
opening 50 of fan cylinder 52 allows relatively
uniform filling of the cylinder with air not-
withstanding the fact that air from plenum 46 is
traveling in an essentially radial direction
toward the fan opening in parts of the chamber,
while moving toward the opening 50 in a generally
axial direction from other sections of the tower
casing. Greater spacing of the orifice opening
from the axis 60 in those areas where airflow is
radial, as contrasted with more axial flow of air
permits the apertured baffle 48 to modify the vena
contracta of airflow to the cylinder, thus in
effect functioning as an optimized invisible eased
inlet. Smooth airflow into cylinder 52 is as-
sisted by the fact that air in the confined space
62 (see Figures 4 to 7 inclusive) is caused to
rotate in a counter clockwise fashion at the
points at which the sections are taken (viewing
Figure 2) which means that the air flow in the
confined space 62 between oriice 58 and an
adjacent segment of opening 50 is in the same
direction as air delivered to the fan cylinder.
Because of the simplicity of the in-
visible eased inlet structure of this invention
which comprises a planar plate with an optimally
sized orifice therein configured to conform to
operating parameters for a particular tower
structure, it is possible to design a required
orifice and to properly space it from the fan
cylinder without regard to metal or reinforced
resin shaping limitations heretofore imposed on
design personnel. This is true whether or not the
tower has air inlets on one, two or all four
sides, and independent of the direction of dis-
93
- 20 -
1 charge of the fan. For example, an evaporative
water cooling tower of the small package type is
illustrated in Figures 9 and 10 wherein casing 124
has an upright air inlet face 170 aligned with
package fill 138 while inlet louvers 172 are
complementary with the inclined outer inlet face
170. Double pass eliminators 144 cover the inner
outlet face 168 of the fill. A hot water dis-
tributor 136 overlies the upper end of fill 138
while the lower part of casing 124 serves as a
cold water basin 142. Air moving structure 120 is
mounted in the end wall of casing 124 opposite air
inlet 170 and comprises a fan 154 rotatable within
fan cylinder 152 projecting outwardly from upright
end wall 130. Fan 154 has been illustrated as
being of the propeller type having a series of
blades 156, but it is to be appreciated that other
types of air moving devices may be employed, as
for example a centrifugal blower or a fan of the
squirrel-cage type.
An upright baffle I48 mounted within
casing 124 and comprising a sheet metal member
spaced from wall 130, is provided with a special
shaped rectangular orifice 158 therein as illus-
trated in Figure 10. In this instance, it is to
be seen that the long axis of orifice 158 extends
vertically to compensate for the radial flow of
air along the upper and lower stretches of baffle
member 148 as contrasted with the more axial flow
of air toward the fan cylinder 152 at the sides of
the casing 124 view~ng Figure 10. Orifice
158 is thus specially shaped to modify the vena
contracta of air flowing into cylinder 152 and
assures that supply thereof near the inside wall
of the cylinder at its inlet is nearly equal at
:
,
- 21 -
1 all angular locations around the circumference Gf
the enclosure.
It is also to be appreciated that the
results of this invention are not dependent on the
provision of a fan cylinder in operable associ-
ation with an air moving device such as a rotary
fan. A vena contract modifying apertured baffle
may also be used where the fan is simply posi-
tioned in a suitable fan opening in a wall, plate
or other structure separating the zone from which
air is to be removed from an area into which the
air is to be discharged.
In the schematic illustration of Figure
11 for example, air moving mechanism 220 includes
structure 224 which has a panel 230 provided with
a circular fan opening 250 therein. A rotary fan
having a series of radially extending blades 256
is positioned for blade rotation inside of opening
250 with the tips 256a of the blades just clearing
the edge of panel 230 defining opening 250.
Baffle member 248 on structure 224 has an ir-
regularly shaped orifice 258 therein sized and
configured in the same manner as described with
respect to baffle orifice 48. Circumscribing
closure wall 232 prevents surrounding air from
entering structure 224 between panel 230 and
baff~e membçr 248. The operation of mechanism 220
is identical with that previously described in
connection with mechanism 20, noting only in this
respect that air is discharged to the area sur-
rounding structure 224 without passing through a
cylinder associated with the fan.
In the variation 320 of the invention
shown in Figure 12, the fan blades 356 are located
just inside of the fan opening 350 in panel 330
- 22 -
1 and the rotary fan is of a diameter causing the
blade tips 356a to extend beneath the edge of the
panel for somewhat better fan efficiency attri-
butable to an improved air seal between the fan
blades and the fan housing. Here again though
baffle member 348 having an orifice 358 is located
in proper airflow modifying-relationship to the
fan and opening 350 therefore.
Mechanism 420 of Figure 13 differs from
that of mechanism 320 only in the location of the
fan in disposition such that the blades 456 are
outboard of the panel 430 above baffle 448 with
the tips 456a overlying the opening defining edge
of the panel for improved air sealing in the same
manner as described with respect to mechanism 320.
In mechanism 520 shown in Figure 14, a
pair of spaced panels 530a and 530b are provided
with cooperatively defined fan opening 550 above
baffle 548. Blades 556 are located such that the
tips 556a extend between panels 530 aand 530b. It
is preferred in t.his respect that the blade tips
extend outwardly to an extent to overlap the edges
of the panels presenting the fan openings 350
therein.
Mechanism 620 in Figure 15 is illus-
trative of the fact that fan cylinder such as
cylinder 652 may be used in association with
rotary fan of any of the variations of the inven-
tion shown in Figures 12 and 14.
In Figure 16, the casing 724 of air
moving mechanism 720 is constructed for entrance
of air only through the right hand side of the
structure. This mono-flow unit therefore has only
a single fill assembly 740 for passage of air
therethrough before entering plenum 746 via
~ 3~ 3
1 eliminators 744. In this instance, the vena
contracta controlling baffle member 748 provided
with an orifice 758 is inclined at angle relative
to the horizontal with the greatest distance
between the baffle and panel 730 provided with the
fan opening 750 being adjacent the air inlet side
of the structure. As a consequence, even though
air enters the tower casing 720 from only one
direction, modification of airflow toward the fan
opening 750 receiving rotary fan 754 may still be
optimized by proper sizing and shaping of orifice
758 in baffle 748.
Another form of dual flow tower is shown
in Figure 17 wherein casing 820 has air inlets on
opposite sides thereof in the same manner as
casing 20 of tower 20 in Figures 1-3. In this
instance though, air entering plenum 846 from
opposed fill assemblies is modified before passing
to fan opening 850 in panel 830 by a baffle member
848 having inclined sections 848a and 848b de-
fining an apex 848c at the central part of the
casing intermediate fill assemblies 738 and 740.
The orifice 858 in baffle member is still shaped
and sized for optimum transition of airflow from
plenum 846 to circular opening 850 in panel 830.
It is also to be appreciated that the baffle
member may be of conical shape overall for strength
purposes and that an orifice of any required
generally rectangular shape or otherwise may be
provided therein.
