Abstract:
A cooling tower is provided for industrial process cooling as well as air conditioning systems. The cooling tower includes a tower shell that is unitarily molded from a plastic material. The tower shell includes opposed parallel top and bottom walls, a bottom connecting wall extending upwardly and outwardly from the bottom wall, a top connecting wall extending downwardly and outwardly from the top wall and a side wall extending between the connecting walls. Supports are unitarily molded and extend outwardly from the bottom connecting wall for supporting a tower shell and filler material disposed therein.

Description:
This application claims priority on Provisional patent Appl. Ser. No. 60/097,904, filed Aug. 26, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The subject invention relates to cooling towers for air conditioning systems and industrial process cooling. 
     2. Description of the Prior Art 
     Air conditioning systems for large buildings employ cooling towers for carrying out a portion of the heat exchange that is essential to the cooling process. Industrial processes (e.g., chemical production, metals industry, plastics industry, food processing, etc.) generate heat that must be disposed of, often by use of cooling towers. The cooling tower is a housing that channelizes air in proximity to a heat exchange fluid. For example, a heat exchange fluid may be circulated through the cooling tower, and at least one fan may be mounted on the cooling tower to generate a flow of cooling air in proximity to the heat exchange fluid. Heat is transferred from the heat exchange fluid to the air, largely through the evaporation of a small percentage of fluid which substantially lowers the temperature of the primary heat exchange fluid. The cooled heat exchange fluid can then return to the process to perform a heat exchange function for either industrial process equipment or commercial air conditioning system. 
     The efficiency of an air conditioning system depends, in part, upon the heat exchange carried out in the cooling tower. Large buildings require large cooling towers, and in many instances an array of large cooling towers. Industrial processes depend on cooling towers to prolong the life of other equipment as well as produce top quality production. 
     The majority of prior art cooling towers are assembled from a plurality of pieces of sheet metal that are mounted to a metallic support frame. These prior art cooling towers typically are manufactured at a location remote from the installation site, and then are shipped to the installation site in a substantially assembled form. These large metallic prior art cooling towers are fairly heavy, and therefore require extensive structural support and greater transportation costs. Furthermore, the size and weight of prior art cooling towers complicates the hoisting and installation of the cooling tower onto the roof of the building. Costs of prior art cooling towers also are adversely affected by the labor intensive process for manufacturing and assembling the various metallic components of the prior cooling tower. 
     In addition to the cost penalties, the metallic sheet material used in prior art cooling towers generates significant vibration related noise due to the rotation of the fans and due to the flow of air through the cooling tower. Noise pollution often requires noise abatement measures that complicate the installation process and that further add to costs. 
     Prior art metallic cooling towers also are subject to corrosion or rust. Thus, prior art cooling towers have a relatively short life. Corrosion and rust problems can be avoided or deferred by employing corrosion or rust resistant alloys. However, these metallic materials further add significantly to the cost of the prior art cooling tower. 
     The prior art includes two types of cooling towers made with plastics. The first type of prior art plastic cooling tower is fabricated from a plurality of fiberglass reinforced polyester (FRP) panels that are fastened together. These plastic towers gain strength through the supplemental glass fiber in the plastic. FRP towers are generally more costly than the galvanized metal towers. Additionally these prior art towers have to be caulked at the seams, require many fasteners to hold the tower together and can develop leaks at the many joints. 
     The other type of prior art plastic towers are vertically oriented unitary cylinders. These towers can be very tall, with heights up to 19 feet. The ratio of the height to the cross-sectional area limits the cooling capability of the tower since cross-sectional are is more determinant of cooling capacity. The excessive height of these towers requires these prior art towers to be shipped with the axis of the cylinder oriented horizontally, which complicates off-loading and installation. These units have also been limited to one fan assembly per cylindrical unit. 
     In view of the above, it is an object of the subject invention to provide a cooling tower that is lighter weight and more durable than prior art cooling towers. 
     It is another object of the subject invention to provide a cooling tower that substantially avoids complex and costly assembly of components. 
     It is an additional object of the subject invention to provide a cooling tower that produces low levels of vibration related noise. 
     It is also an object to provide a unitary molded plastic tower that is not cylindrical and allows a much higher ratio of cross-sectional area to overall height. 
     It is also an object to provide a cooling tower that can be shipped fully assembled and upright to ease off-loading and installation. 
     Still a further object of the subject invention is to provide a substantially corrosion resistant cooling tower. 
     SUMMARY OF THE INVENTION 
     The subject invention is directed to a cooling tower that is made substantially from plastic. More particularly, a major portion of the cooling tower is defined by a tower shell that is unitarily molded from a suitable plastic, such as polyethylene. The unitarily molded tower shell may be formed by rotational molding. The tower shell may be molded to include air inlet louvers that are unitarily molded with the body of the tower shell. Additionally, short cylindrical flanges may be molded at the top of the tower shell for accommodating fans and necessary support housings for the fans. Apertures may be molded into the tower shell or may subsequently be cut into the tower shell for accommodating fluid pipes and/or conduits for electric cables. Separate fittings may then be mounted to these molded or cut apertures to accommodate connections with pipes or conduits. These separate fittings may be plastic or metal depending upon specifications of the heat exchange system. 
     The tower shell preferably is elongated and of polygonal cross-sectional shape, such as an octagonal cross-sectional shape. Thus, the cooling tower may include substantially parallel top and bottom surfaces that are aligned or alignable substantially horizontally. The tower shell may further include at least one vertically aligned or alignable side wall that is unitarily formed to extend continuously around the periphery of the tower shell. Angled connecting walls extend between the side walls and the respective top and bottom walls. 
     Tower shells in accordance with the subject invention may be of different respective lengths to accommodate different cooling demands. However, all of the tower shells may be of substantially constant longitudinal cross-sectional size and shape. Thus, a larger tower shell may differ from a smaller tower shell primarily by the length and by the number of cooling fans accommodated along the length. This use of a uniform cross-sectional shape for all tower shells enables the tower shells to be manufactured in the same or similar rotational molds. The molds may be rotatable about a horizontal axis and may be adapted to adjust the length of the mold by merely repositioning end wall portions of the mold. 
     The polygonal cross-section of tower shells in accordance with the subject invention enables a uniform width and depth for the fill material that performs the mass transfer function within the tower shell. Additionally, the tapered bottom portion of the polygonal tower shell defines a concave water sump at the bottom of the tower, while the tapered top section achieves an efficient exit air flow. 
     The tower also has several strengthening ribs designed to provide structural stability where needed. These ribs are a corrugated shape that provides more strength than a straight wall. Additional strength is created by conical ends that help support fan systems on the top of the tower. 
     Strength also is achieved by the rotational molding. In particular, the rotational molding of a structure as large as the subject cooling towers results in greater thicknesses at locations where surfaces meet at an angle. These greater thicknesses effectively define unitary fillets that add to the strength and vibration resistance. The fillets are particularly helpful at the peripheries of the top and bottom walls at the louvers, at the reinforcing flanges and where the fan-mounting flanges meet the top wall. Thus, the subject cooling towers avoid the complex assembling inefficiencies of the prior art and simultaneously enhance strength and efficiency at critical locations. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top plan view of a two-fan cooling tower in accordance with the subject invention. 
     FIG. 2 is a front elevational view of the cooling tower shown in FIG.  1 . 
     FIG. 3 is an end elevational view of the cooling tower of FIGS. 1 and 2. 
     FIG. 4 is a top plan view of a three-fan cooling tower in accordance with the subject invention. 
     FIG. 5 is a front elevational view of the three-fan cooling tower shown in FIG.  4 . 
     FIG. 6 is a cross-sectional view taken along line  6 — 6  in FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A two-fan cooling tower in accordance with the subject invention is identified generally by the numeral  10  in FIGS. 1-3. The cooling tower  10  includes a tower shell  12  that is unitarily molded from polyethylene in a rotational mold. The tower shell  12  is molded to include a substantially vertically aligned side wall  14  extending continuously about the tower shell  12 . The side wall  14  includes planar parallel front and rear sections  16  and  18  that extend between semi-cylindrical end sections  20  and  22 . 
     The tower shell  12  further includes the tapered top connecting wall  24  extending unitarily from the side wall  14 . The top connecting wall  24  includes planar front and rear sections  26  and  28  respectively which extend unitarily from the planar front and rear side wall section  16  and  18  respectively. Additionally, the tapered top connecting wall  24  further includes conically generated end sections  30  and  32  respectively which extend upwardly and inwardly from the semi-cylindrical sections  20  and  22  respectively of the side wall  14 . 
     The tower shell  12  further includes a tapered bottom connecting wall  34  extending unitarily downwardly and inwardly from the side wall  14 . More particularly, the tapered bottom connecting wall  34  includes front and rear panels  36  and  38  that extend from the planar front and rear sections  16  and  18  respectively of the side wall  14 . The tapered bottom connecting wall  34  further includes planar bottom end panels  40  and  42  that extend angularly inwardly from opposite ends of the tower shell  12 . Upper ends of the end panels  40  and  42  are connected to the side wall  14  by substantially horizontal chordal support panels  44  and  46  respectively. Triangular corner panels  48 ,  50 ,  52  and  54  extend between the front and rear panels  36  and  38  and the end panels  40  and  42  of the tapered bottom connecting wall  34 . More particularly, the triangular corner panel  48  extends between the front panel  36  and the end panel  40 . The triangular corner panel  50  extends between the rear panel  38  and the end panel  40 . The triangular corner panel  52  extends between the front panel  36  and the end panel  46 , while the triangular corner panel  54  extends between the rear panel  38  and the end panel  42 . Upper ends of the lower corner panels  48 - 54  are connected to lower portions of the side wall  14  by horizontal chordal support panels  58 - 64 . The chordal support panels  44 ,  46  and  58 - 64  provide necessary structural support for the tower shell  12  and also support the PVC fill  66  disposed in the tower shell. The front and rear lower panels  36  and  38  and the triangular lower corner panels  48 - 54  all are molded to include louvers  68  for accommodating an upward air flow. 
     The tower shell  12  further includes a planar bottom wall  70  of substantially rectangular configuration extending unitarily between the lower edges of the front and rear panels  36  and  38  and the end panels  40  and  42 . The tower is mounted on a support platform  100  constructed of steel or fiberglass reinforced plastic (FRP) that uniformly supports the planar bottom  70  of the tower. This support platform also has support legs  101  that protrude perpendicular to the bottom of the tower to provide additional support for the side walls  14 . End support enclosures  72  and  74  extend unitarily downwardly from the lower end panels  40  and  42  and terminate in substantially coplanar relationship with the bottom wall  70 . Portions of the end enclosure  74  are provided with circular apertures  78  extending therethrough for accommodating fittings to deliver electrical conduits and pipes to the cooling tower  10 . Strengthening ribs  105  are molded corrugations placed several places in the tower to provide enhanced strength over a straight wall. 
     The tower shell  12  further includes a substantially oval top wall  84  which extends unitarily between and joins upper end regions of the tapered upper wall  24 . The top wall  84  is molded to include first and second circular fan openings  86  and  88  respectively. 
     As shown most clearly in FIG. 2, the tower shell  12  assumes a substantially octagonal profile when viewed from the front and from the rear. Additionally, as shown in FIG. 3, the tower shell  12  assumes a substantially octagonal profile and cross-section when viewed from the left or right ends. 
     As noted above, the tower shell  12  is used with fittings at apertures  78  in the end enclosure  74 . Still further, a coated steel fan ring  92  may be mounted to each of the fan apertures  86  and  88  in the top wall  84 . Fans  94  along with the appropriate hardware and motors then are mounted to the fan rings  92  for generating an upward flow of air through the louvers  68  and out of the fan apertures  86  and  88 . 
     The tower shell  12  is unitarily formed in a rotational mold that rotates about an axis extending from left to right in FIG.  1 . The mold may be elongated to provide a larger tower shell as shown in FIGS. 4 and 5 respectively. More particularly, FIGS. 4 and 5 show a tower shell  112  that is structurally and functionally similar to the tower shell  12  shown in FIGS. 1-3. Additionally, the end view of the tower shell  12  shown in FIG. 3 is substantially identical to the end view for the tower shell  112 . However, the tower shell  112  differs by being sufficiently elongated to accommodate a third fan. Furthermore, additional supports are provided at the tapered lower front and rear panels, on planar portions of the side panels and on the elongated planar portions of the upper panel. The tower shell  12  shown in FIGS. 1-3 defines an overall length of approximately 15 feet. In contrast, the tower shell  112  shown in FIGS. 4 and 5 to define an overall length of almost 22 feet. 
     The rotational molding results in greater thickness at locations where walls, panels, flanges and/or ribs meet at an angle. For example this greater thickness defines a unitary fillet  102  as illustrated in FIG. 6 where the oval top wall  84  intersects the planar front section  26  of the tapered top connecting wall  24 . The fillets define a thickness approximately twice the thickness of other locations. For example, the nominal plastic thickness at most locations on the tower shell  12  is approximately 0.375 inch. However the unitary fillets define thicknesses of about 0.750 inch. Comparable fillets exist at other intersecting surfaces. In particular, unitary fillets exist at the strengthening ribs  105 , at the louvers  68 , and at the fan apertures  86  and  88 . These unitary fillets add to strength and vibration resistance.