US3637195A

US3637195A - Cooling tower apparatus

Info

Publication number: US3637195A
Application number: US9794A
Authority: US
Inventors: Benjamin V Blazer; Mahmoud S El-Tahry
Original assignee: BLAZER CORP
Current assignee: BLAZER CORP
Priority date: 1968-07-05
Filing date: 1970-02-09
Publication date: 1972-01-25
Anticipated expiration: 1989-01-25

Abstract

An improved modular cooling tower includes an air fan centrally located at the bottom of the tower, and a baffle vane and pivoted shutter arrangement disposed above the fan. The fan generates an airflow which passes through the baffles and vanes to react with a heated liquid flowing downward through the tower via a plurality of evaporating surfaces. The shutter structure is adapted to pass the fan generated airflow for cooling purposes while preventing the escape of fluid or vapor laden air from the tower fan orifice, thus obviating a potentially hazardous condensation condition. In accordance with other aspects of the present invention, improved sump, fan and drive apparatus is provided to accommodate plural module installations.

Description

United States Patent Blazer et al,

[451 Jan. 25, 1972 [54] COOLING TOWER APPARATUS [72] Inventors: Benjamin V. Blazer, Paterson; Mahmoud S. El-Tahry, Passaic, both of NJ.

[73] Assignee: Blazer Corporation, East Rutherford, NJ.

[22] Filed: Feb. 9, 1970 [21] Appl. No.: 9,794

Related US. Application Data [63] Continuation-in-part of Ser. No. 742,567, July 5,

1968, Pat. No. 3,494,109.

[52] U.S.Cl ..261/30, 261/64, 261/109 [51] Int. Cl ..B0ld 47/00 [58] Field ofSearch ..26l/30, 108-113,

261/64, 64.3, DIG. ll

[56] References Cited UNITED STATES PATENTS 1,986,653 1/1935 Wade ..26l/DIG. 11

Primary Examiner-Tim R. Miles Assistant Examiner-Steven H. Markavitz Attorney-Stephen B. Judlowe, Esq.

[5 7 ABSTRACT An improved modular cooling tower includes an air fan centrally located at the bottom of the tower, and a baffle vane and pivoted shutter arrangement disposed above the fan. The fan generates an airflow which passes through the baffles and vanes to react with a heated liquid flowing downward through the tower via a plurality of evaporating surfaces. The shutter structure is adapted to pass the fan generated airflow for cooling purposes while preventing the escape of fluid or vapor laden air from the tower fan orifice, thus obviating a potentially hazardous condensation condition.

In accordance with other aspects of the present invention, im' proved sump, fan and drive apparatus is provided to accommodate plural module installations.

12 Claims, 6 Drawing Figures HEAT some:

ENERGY SOURCE COUMNG TUWER APPARATUS This invention relates to heat transfer apparatus and, more specifically, to an improved cooling tower arrangement for cooling a heated liquid by an evaporator process. This application is a continuation-in-part of our like entitled application Ser. No. 742,567 filed July 5, 1968, and now US. Pat. No. 3,494,109.

Heat exchanging apparatus for cooling a flowing heated liquid with a counterflowing airstream has been widely employed. Such arrangements typically employ nozzles for supplying a heated liquid into the tower, with the liquid flowing downward under the action of gravity. Blowing apparatus is employed to generate an upward airflow exiting through the top of the tower. The moving airstream reacts with, and cools the liquid by an evaporator process.

However, prior art'cooling tower arrangements have been characterized by one or more of the deficiencies considered hereinbelow, and have thus not been completely satisfactory. First, the requisite airflowing fans have commonly been located at the top of the cooling tower to induce an upward airflow, with the air radially entering the tower through apertures located about the bottom periphery thereof. Ac cordingly, such an induced draft, or draw through" cooling tower must be fabricated of strong structural materials to support the relatively weighty top-mounted fan and its attendant driving apparatus. This problem is often compounded throughout an entire building structure since the cooling towers are placed on top of the building in many installations. Then also, relatively large, oversized fans are required for such an arrangement since the airflow is induced by the relatively inefficient low-pressure, upstream side of the fan, and not by the more efiicient discharge fan side. Further, fan maintenance is complicated since all work must be performed on top of the tower.

Of special importance, air carrying considerable water vapor escapes from the tower through the lower tower configurations. The vapor so conveyed oftentimes condenses on the building top thus forming water pools and, in winter, ice fonnations. Such water and/or ice collection creates hazardous conditions for tower maintenance and other rooftop activities; cause structural damage attributable to corrosive and weight effects; and also periodically generates a potentially harmful waterflow running off the building top.

One alternative building tower configuration employs one or more blower fans mounted external to the tower about its lower periphery, thus largely obviated the structural problems accruing to tower top fan mounting. However, the horizontally protruding fans impart a large vertical profile to such cooling towers which thus take up a relatively large roof area for any given cooling capacity. Also the fans, located at best at a number of discrete locations, do not produce an airflow which is uniform throughout the tower. Thus segments of the flowing heated liquid are not acted upon by a significant counter airflow and are thus not cooled appreciably. Further, vapor can escape from such towers through the fan-mounting apertures when the fans are inactive.

Moreover, a plurality of cooling towers are often required on top of a building structure where increased cooling capacity is required. Prior art tower arrangements place a heavy weight load on the building structure, each such tower holding a full quantum of cooled fluid in a sump awaiting recycling of a pump to a heat source. Accordingly, sufiicient structural strength must be incorporated into the building to support this weight load.

In addition, where plural tower modules have been employed, or plural centrifugal fans within a single module, there have been great difficulty in removing the fans when service or inspection is required. The impeller in a centrifugal fan has heretofore been extracted axially from the fan scroll, first requiring that a common fan driving shaft be withdrawn. This is diflicult per se, further inconvenient when several fans are coupled to one shaft, and particularly disadvantageous where there is tight module packing such that there is little or no room to conveniently maneuver the shaft.

Further, in cooling towers with a high-thermal loading, the cooled fluid must be extracted and recycled at a relatively rapid rate. This has produced water cavitation above a drain outlet, thereby reducing pump and drain efficiency. Moreover, in many cases, the insufficient waterhead has resulted in air being drawn into the pump and fluid conduits, causing noisy and potentially harmful vibrations, pump oxidation, and severely reduced efficiencies.

It is thus an object of the present invention to provide an improved cooling tower arrangement.

Mlore specifically, it is an object of the present invention to provide a cooling tower arrangement having a fan located at the bottom portion thereof to facilitate maintenance access to the fan, and to permit fabricating the tower of relatively light, inexpensive structural materials making maximum use of prefabrication techniques, rather than site work construction.

Still another object of the present invention is the provision of a cooling tower arrangement which prevents water vapor from escaping from the lower portion thereof, and which occupies a relatively small surface area.

Yet another object of the present invention is the provision of a modular cooling tower arrangement wherein plural modules may be readily and conveniently assembled.

A still further object of the present invention is the provision of an improved sump arrangement which greatly reduces the waterload to be supported by a building structure, and where cavitation problems are eliminated.

it is another object of the present invention to provide a cooling tower fan and improved vane and battle assembly which provides uniform air distribution. about the tower cross section.

Yet another object of the present invention is the provision of an improved drive arrangement for plural cooling towers employing a flexible coupling.

The above and other objects of the present invention are realized in a specific, illustrative modular cooling tower arrangement which includes a nozzle array for spraying water for downward translation through a plurality of corrugated evaporating surface plates. One or more centrifugal fans are centrally located at the bottom of the tower and generate an upward airflow through the evaporating surfaces acting through a plurality of baffle-defining vanes disposed vertically above the fan. Pivoted shutter plates are secured to the tuning vanes.

During the cooling process, the velocity pressure generated by the fans keeps the pivoted shutter plates open and the airflow uniformly passes through the turning baffles to the evaporating plates where it reacts with, and efficiently cools the downward moving heated liquid. The discharge velocity and static pressure produced by the energized fans is more than sufficient to prevent liquid and water vapor from escap ing from the tower through the fan orifice.

A plurality of the cooling tower modules may be cascaded to effect increased cooling capacity. When cascaded, only one such tower employs a relatively deep (full size) sump, the remaining tower sumps being connected by a flapper check valve with the full sump. This arrangement decreases the weight load to be supported by a building structure and the fluid heating area required for winter operation, and increases the efficiency of the water-extracting conduits and pump(s). Further in this regard, anticavitation apparatus is provided to ensure a full waterhead above a water exiting drain, thereby preventing air from entering the fluid circulating system.

in accordance with other aspects of the present invention, a split scroll is employed for each of the fans to permit easy impeller removal for inspection and/or maintenance. Further, selected turning vanes have an irregular upper edge such that air leaves the turning surfaces at varying tangent directions to uniformly distribute air throughout the tower for efficient interaction with the falling heated fluid. Further, an improved motor drive and flexible coupling is employed to join two modules together to accommodate possible misalignment of the fan impeller driving shafts for the adjacent modules; to

permit such modules to be driven by relatively inexpensive and commercially available single shaft motors rather than double shaft motors heretofore employed; and wherein the flexible coupling need sustain and transmit the driving torque for only one module.

A complete understanding of the present invention and of the above and other features and advantage thereof may be gained from a consideration of the following detailed description of an illustrative embodiment thereof presented hereinbelow in conjunction with the accompanying drawing in which:

FIG. 1 is a schematic cross-sectional diagram illustrating a modular cooling tower arrangement which embodies the principles of the present invention;

FIG. 2 is a cross-sectional schematic diagram depicting a sump configuration for a cooling tower assembly formed of three individual cooling tower modules;

FIG. 3 is a graph depicting the relationship between fluid flow through a conduit, the height of fluid disposed above the conduit, and conduit diameter;

FIG. 4 schematically illustrates in cross section a driving arrangement for two contiguous cooling tower modules;

FIG. 5 depicts a turning vane employed in the arrangement of FIG. 1; and

FIG. 6 illustrates a makeup water system for the module of FIG. 1.

Referring now to FIG. 1, there is shown a composite cooling tower 10 of any desired cross-sectional shape having sidewalls 14, an open top 12, operative bottom surfaces 71 and 72, and standoff mounting apparatus 20. The tower 10 is located on a surface 5 which may illustratively comprise the top of a buildmg.

Heated liquid, for example, water is supplied by a heat source 40 to a plurality of emitting nozzles 32 by way of trunk and

branch conduits

30 and 31. The water flows downward through a plurality of corrugated evaporating surface plates 22 into a reservoir sump area 70. Water is recirculated from the sump 70 to the heat source 40 and eventually to the nozzles 32 by a conduit 43-41. The recirculation path will typically include a pump 42. The heat source 40 may comprise any apparatus for imparting heat to a liquid such as watercooled machinery (e.g., compressors or other motors), airconditioning equipment, industrial or chemical processes, or the like.

Disposed at the bottom of the tower is at least one, and typically a plurality of fans, e.g., a centrifugal fan 30. As discussed below in conjunction with FIG. 4, three such fans may be employed, only one being shown in the cross-sectional view of FIG. 1. The fan 30 includes an outer scroll comprising

scroll portions

31 and 32, the scroll portion 31 including an expanding exit end portion thereof to convert a portion of the air velocity generated by the fan to static air pressure by means of the well-known static regain mechanism. Mounted within the assembled scroll 31-32 is an impeller wheel 34 which includes driven vanes 35 and a hub 36. The wheel is supported, and driven for rotation by a shaft 39, the hub 36 being secured to the shaft 39 by any well-known mechanism such as a bolt, key and slot, or the like.

The front and

rear scroll portions

31 and 32 are secured together when the fan 30 is in service, as by screws 33. Should the impeller 34 or other internal fan assembly require extraction for service, inspection, or maintenance, the screws 33 are extracted and the rear scroll portion removed. The impeller and internal fan portion are then readily available for inspection. Should the impellers require service, end bearings 100 and 101 (FIG. 4) which support the shaft 39 are simply removed from tower structural members 13 (as by removing screws), and the entire shaft with its impeller wheels 34 secured thereto simply removed from the back of the tower.

A motor 73 is connected by any suitable coupling 73a, e.g., a belt, chain or the like, to the shaft 39 (see, for example, the belt 106 and pulley wheel 105 of FIG. 4). When supplied with electrical energy from an energy source 37, the motor 73 and the coupling 73a rotate the impeller wheel 34 thereby forcing air upward through the scroll portion 31 and into the cooling tower for heat-exchanging purposes. A temperature sensor 38 may optionally be provided within the sump 70 to disconnect energy from the motor when the water is cooled sufficiently such that no further cooling is appropriate.

A plurality of air-baffle defining vanes 91, 92, and 94-99 are transversely connected across the interior of the cooling tower. Four plate assemblies 52, 53, 54 and 55 are pivotally attached to the surfaces 92, 94, 97 and 91, respectively, as by hinges 62, 63, 64 and 65. The plates 52-55 may be formed of water-resistant metal, rubber or plastic.

When the fan 30 is energized, the airflow about and between the vane structures 92, 94, 97 and 91 retains the plates 52-55 in an open position (shown in solid line in FIG. 1), such that air can exit from the scroll portion 31 and flow through the vane defined baffles without impediment. More particularly, air exiting from the scroll portion 31 follows the path indicated by vectors in FIG. 1 and flows through the baffles where it is redirected by

vanes

95, 96, 98 and 99 to be uniformly distributed across the cross section of the tower. The airflow form the

plates

95, 96, 98 and 88 moves upward to and through the evaporator surface plates 22 (fill) for interaction with the downward moving heating liquid. The corrugated shape and close spacing of the plates 22 serve to break up the flowing liquid mass so that a large liquid surface area, moving relatively slowly, is present for a relatively extended time period to be acted upon by the airflow for efficient heat exchanging.

A plurality of corrugated eliminator plates 24 are mounted above the nozzles 32. Plates 24 permit the heated, vapor-bearing rising airstream to escape from the tower while preventing water in a liquid state from escaping from the tower.

When the fan 30 is deenergized, the plates 52-55 rotate downward under action of their gravity moment weight to positions shown dashed in FIG. 1, effectively sealing the orifice of the scroll portion 31. This prevents vapor or water, which may still be flowing from the nozzles 32, from escaping from the tower through the fan 30 to the top of the building 5 where water accumulation or ice conditions may develop. Further, the plates 52-55 prevent water from reaching the interior of the fan 30 where freezing or oxidation can occur.

The air-tuming vane 98, illustrative of the

vanes

95, 96, 98 and 99, is depicted in detail in FIG. 5. The upper part of the vane 98 includes portions 114 which are fully curved, and portions 116 which terminate intermediate the full curvature. As indicated by the vectors and 112 in FIG. 5, air leaves the upper (downstream) edge of the plate 98 tangentially to the edge. Accordingly, air is distributed across the cross section of the tower by reason of the differing upper edge tangents of the

plates

95, 96, 98 and 99 and portions thereof. The air distribution is further aided by the pressure gradient effected should a disproportionate amount of air tend to flow to any given spot or area.

By way of functional operation for the above-described cooling tower apparatus shown in FIG. 1, heated liquid supplied by the source 40 and the nozzle 32 flows between and against the evaporating surface plates 22.

When cooling is being effected, i.e., when the transducer 38 notes a liquid temperature in the reservoir 70 above the threshold level, the fan 30 is energized by the source 37, motor 73 and coupling 73a and generates an airflow through the opened plates 52-55 between the turning vanes. The plates 52-55 are retained in their raised positions by the velocity pressure of the air, and the plates do not impede the airflow to any appreciable extent.

The airflow proceeds upward in the tower 10 to and through the plate array 22, and is uniformly distributed throughout the cross section of the tower. The flowing air reacts with the water, both within and below the plates 22, by evaporating a small portion of the water thus removing a quantum of heat energy, principally determined by the heat of vaporization for the evaporated water, from the liquid state which remains in the tower. Accordingly, the liquid is cooled as it flows downward through the composite structure it).

As the water continues to flow downward towards the bottom of the tower 3W, it is prevented by the positive air pressure generated by the fan Elli from flowing into the fan scroll portion 3t onto the building top 5. To the contrary, the water either falls directly, or is deflected by the air pressure gradient or the surface 712 into the watercollecting sump Tit for collection and recirculation. Similarly, the fan generated air pre"- sure prevents any vapor laden air from escaping ohto the building top 5.

The heated air, transporting the evaporated fluid, passes through the eliminator plates 2d and escapes through the open tower top l2. Accordingly, fluid must be continuously introduced into the system to replace that small percentage of fluid that is being lost (and which has effected the desired heat transfer).

The above-described mode of tower operation continues either indefinitely until shut off or until the transducer 38 senses that the water has been sufficiently cooled, whereupon the fan 3% is deactivated. As the air velocity pressure decreases responsive to the fan being deenergized, the plates 52-55 encounter a monotonically decreasing upward force, and thus move toward their dashed orientation to seal the scroll 31 orifice. Accordingly, with the fan 31 off, neither the continuously falling water nor the moisture laden air is permitted to escape through the scroll, and thus no condensation hazard is produced on the towersupporting surface 5.

The cooling tower resides in this passive state until the transducer 38 again notes a water temperature increases to a point at or exceeding the threshold level (or until a down tower is again put into service). When this occurs the fan is energized by the controlled energy source 37 and the abovedescribed operation is repeated.

Thus, a cooling tower embodying the principles of the present invention has been shown by the above to cool a heated liquid in an efficient and uniform manner, while not allowing a liquid accumulation on the tower supporting surface. The tower includes a bottom mounted fan which generates an airflow moving from the efficient discharge side thereof, and the weight of the fan is not supported by the tower walls. Accordingly, the tower may advantageously be fabricated from relatively light, inexpensive building material and, moreover, be largely prefabricated to avoid the expense and inconvenience attendant with job site construction. Further, the bottom located fan is readily accessible for maintenance purposes.

The above discussion has considered. the single cooling tower module of FIG. ll. As noted above, a plurality of such modules may be interconnected where increased cooling capacity is required. We have discovered, when assembling more than one module into a composite cooling structure, that it is desirable to eliminate most of the sump areas of all but one centrally located tower module. The sump assembly for three-cooling tower modules 10,, lit) and l0 is shown in FIG. 2. The sumps 'l'tt and 70 associated with the tower modules it), and Mi are truncated, and only the sump 7% associated with the module llll includes full depth. The water exit conduit A3 is located at the bottom of the full sump 70 The heated fluid falling downward in the tower module falls directly into the sump 70 while that flowing downward in the towers 10 and llll flows into the sump 70 via

sumps

70 and 70 and hinged flapper valve plates 85 and 85. Since most of the water is accommodated in the sump 7%, there is a greater head of water in this sump above the orifice of conduit 43 than there would be if water were individually collected in the several tower sumps. Accordingly, this pronounced head of water above the circuit 43 allows a relatively greater amount of water to flow through a relatively small diameter pipe, thus permitting a pipe cost savings since the price of piping increased markedly with diameter. There is a concomitant savings in weight for the tower assembly as well. A graphical relationship between fluid flow through a conduit vis-a vis the fluid head and pipe diameter illustrating this savings is shown in FlG. 3.

Further, for winter operation, only the bottom area of the tower lltlt need be heated since only the sump 7111 collects cooled fluid awaiting recirculation. The flapper plates and 88 prevent moist air from flowing from the tower llllt into the tower it), or lll when these latter towers are shut down, as for winter operations or other reduced load application.

For tower assemblies of large capacity, there is a rapid fluid circulation with attendant large fluid velocity at the orifice of the output conduit (i.e., the pipe id in the instant case). in prior art arrangements, this rapid fluid extraction has generated a fluid cavitation above the circuit thereby lowering pump and circulation efficiencies, as well as the aforementioned attendant serious disadvantages obtaining if air is drawn into the pump and fluid system. To obviate these difficulties, we employ a plate 80 disposed above the input to the conduit l-Ii, the plate being supported as by standoffs fill. The waterflow per unit of time through the system is determined by the velocity of water entering the pipe 43 multiplied by the cross-sectional area of the pipe. This quantity of water will enter the volume beneath the plate M through an area defined by the periphery of the plate 8t), multiplied by the distance between the plate 50 and the bottom of the sump 70 Since this latter area is much greater than the cross section of the pipe 43, water moves relatively slowly beneath the plate 80 and hence the entire volume between the plate fill is always filled with water. This is aided by the head of water above the plate 80. Accordingly, a full head of water is assured above the pipe $3, and cavitation problems are eliminated. Thus, the pump and circulation apparatus perform efficiently and no air can be drawn into the system.

A filter 84 may advantageously be disposed about the periphery of the plate W to block dirt and other undesired impediments. Also, the pipe 43 may project a distance d2 above the bottom of the sump, such that dirt and other foreign matter will collect as sediment at the bottom of the sump within the height 82 to be collected and removed at an appropriate time while not flowing into the pipe 43 and clogging the fluid apparatus.

The driving arrangement for driving two contiguous tower modules A and B is shown in FIG. 4i and has largely been described above. Each module includes a shaft 39 mounted between two end bearings tilt) and 1101. The impellers 34 for one or more fans 30 are secured to each shaft 39, three such impellers being shown in the drawing. A driven pulley W5 is secured to one of the shafts 39 and driven by the motor 73 acting through the belt coupling W6. A flexible coupling 103 of any well-known type is employed to join the two shafts, the flexible coupling accommodating any shaft misalignment in the system. The entire assembly may be driven by a single shaft rather than by a complex and expensive double shaft motor, and the flexible coupling W3 need transmit only the torque required for the module distant from the pulley 105, in this case the tower module 13.

Finally, a makeup water system is shown in FIG. 6. Where plural modules are employed, only one: such water makeup system will be utilized and connected with the tower module which includes the full sump. The tower wall 14 is indented over a limited transverse distance (e.g., 2 feet), and a float valve lllll, controlled by a float 129 is employed. When the water level decreases below a minimally acceptable height, the float i activates the valve lid and makeup water flows into the sump 7t) through a nozzle ill. The threshold level is adjusted above the top of plate fill, and set to a value for optimum system operation.

The tower sidewall area is open, and the height of the wall is made something more than the height above the rooftop 25 of the system overflow discharge valve. if the system water level rises unduly, and the excess water is not dissipated through the discharge valve for any reason, the wall 125 serves as an energizing overflow mechanism and water follows a dashed path ll23 discharging from the tower over the wall R25.

It is to be understood that the above-described arrangement is only illustrative of the principles of the present invention. Numerous modifications and adaptations thereof will be readily apparent to those skilled in the art without departing from the spirit and scope of the present invention.

What is claimed is:

1. In combination, a cooling tower including a fan orifice in the bottom portion thereof, a fan including a scroll projecting through said orifice in the bottom of said tower for generating an upward airflow in said tower via said orifice, means for injecting a flow of fluid in said tower, a plurality of vanes mounted above said fan scroll, and means for covering said fan when said fan is deenergized and for opening said orifice and passing said airflow upward through said tower when said fan is energized, said fan orifice selective covering means including pivotally mounted means affixed to selected of said vanes.

2. A combination as in claim 1 further comprising a plurality of evaporating surface plates included in said tower and mounted intermediate said selective fan covering means and said fluid inserting means.

3. A combination as in claim 1 wherein said pivotally mounted means includes at least one shutter member pivoted for rotation above said fan.

4. A combination as in claim 3 further comprising corrugated eliminator plates included in said tower and mounted above said fluid inserting means.

5. A combination as in claim 1 wherein at least one of said vanes includes an air downstream edge having portions therealong which terminate at diflering spatial angles.

6. A combination as in claim 1 wherein said fan is of the centrifugal type, and wherein said scroll is formed of two selectively disengageable members.

7. A combination as in claim 1 wherein said cooling tower includes means forming a sump about the bottom of said tower, an exit conduit about the bottom of said sump, and a cavitation eliminating plate disposed over and spaced from the input orifice of said conduit.

8. A combination as in claim 1 further comprising additional like cooling towers, means in one of said towers forming a relatively deep sump about the bottom of said tower, means in the remainder of said towers forming relatively shallow sumps in said towers, and fluid passing means connecting said relatively shallow and relatively deep sumps.

9. A combination as in claim 8 wherein said fluid passing means including means for permitting only a one-way flow therethrough.

10. A combination as in claim 1 wherein said cooling tower includes means for defining a sump about the bottom of said tower, said sump defining means including two-spaced walls defining an opening accessible to the tower exterior, a float valve having a control float disposed in said sump between said spaced walls.

11. A combination as in claim 1 further comprising an additional cooling tower, each of said towers including a fan driving shaft, and a flexible coupling interconnecting said shafts.

12. A combination as in claim 11 further comprising axle driving means including means secured to one of said shafts.

Claims

5. A combination as in claim 1 wherein at least one of said vanes includes an air downstream edge having portions therealong which terminate at differing spatial angles.