Abstract:
A method for heating a fluid using a heating tower. The method includes the steps of drawing an air stream into the heating tower through an inlet and passing the air stream over a fill medium. The method for heating a fluid also includes passing a fluid over the fill medium along with discharging the air stream from the heating tower through an outlet. The method further includes isolating the inlet air stream from the outlet air stream.

Description:
FIELD OF THE INVENTION 
   This invention relates generally to an apparatus and method for imparting heat to a circulating fluid by water heated by a heating tower apparatus. More particularly, the present invention relates, for example, to an apparatus and method whereby liquefied natural gas or the like, is vaporized via heat exchange. 
   BACKGROUND OF THE INVENTION 
   There are times when it is desirable to impart heat from ambient air to a relatively cool liquid to “heat” the liquid. This circumstance can arrive with respect to liquefied natural gas. 
   The cryogenic liquefaction of natural gas is routinely practiced as a means for converting natural gas into a more convenient form for transportation. Such liquefaction typically reduces the volume by about 600 fold and results in an end product that can be stored and transported more easily. Also, it is desirable to store excess natural gas so that it may be easily and efficiently supplied when the demand for natural gas increases. One practical means for transporting natural gas and also for storing excess natural gas, is to convert the natural gas to a liquefied state for storage and/or transportation and then vaporize the liquid as demand requires. 
   Natural gas often is available in areas remote from where it will ultimately be used, therefore the liquefaction of natural gas is even of greater importance. Typically, natural gas is transported via pipeline from the supply source directly to the user market. However, it has become more common that the natural gas be transported from a supply source which is separated by great distances from the user market, where a pipeline is either not available or is impractical. This is particularly true of marine transportation where transport must be made by ocean-going vessels. Ship transportation of natural gas in the gaseous state is generally not practical because of the great volume of the gas in the gaseous state, and because appreciable pressurization is required to significantly reduce the volume of the gas. Therefore, in order to store and transport natural gas, the volume of the gas is typically reduced by cooling the gas to approximately −240° F. to approximately −260° F. A this temperature, the natural gas is converted into liquefied natural gas (LNG), which possesses near atmospheric vapor pressure. Upon completion of transportation and/or storage of the LNG, the LNG must be returned to the gaseous state prior to providing the natural gas to the end user for consumption. 
   Typically, the re-gasification or vaporization of LNG is achieved through the employment of various heat transfer fluids, systems and processes. For example, some processes used in the art utilize evaporators that employ hot water or steam to heat the LNG to vaporize it. These heating processes have drawbacks however because the hot water or steam oftentimes freezes due to the extreme cold temperatures of the LNG which in turn causes the evaporators to clog. In order to overcome this drawback, alternative evaporators are presently used in the art, such as open rack evaporators, intermediate fluid evaporators and submerged combustion evaporators. 
   Open rack evaporators typically use sea water or like as a heat source for countercurrent heat exchange with LNG. Similar to the evaporators mentioned above, open rack evaporators tend to “ice up” on the evaporator surface, causing increased resistance to heat transfer. Therefore, open rack evaporators must be designed having evaporators with increased heat transfer area, which entails a higher equipment cost and increased foot print of the evaporator. 
   Instead of vaporizing LNG by direct heating by water or steam, as described above, evaporators of the intermediate type employ an intermediate fluid or refrigerant such as propane, fluorinated hydrocarbons or the like, having a low freezing point. The refrigerant can be heated with hot water or steam, and then the heated refrigerant or refrigerant mixture is passed through the evaporator and used to vaporize the LNG. Evaporators of this type overcome the icing and freezing episodes that are common in the previously described evaporators, however these intermediate fluid evaporators require a means for heating the refrigerant, such as a boiler or heater. These types of evaporators also have drawbacks because they are very costly to operate due to the fuel consumption of the heating means used to heat the refrigerant. 
   One practice currently employed in the art to overcome the high cost of operating boilers or heaters is the use of water towers, by themselves or in combination with the heaters or boilers, to heat the refrigerant that acts to vaporize the LNG. In these systems, water is passed into a water tower wherein the temperature of the water is elevated. The elevated temperature water is then used to heat the refrigerant such as glycol via a first evaporator, which in turn is used to vaporize the LNG via a second evaporator. These systems also have drawbacks however in terms of the buoyancy differential between the tower inlet steam and the tower outlet steam. The heating towers discharge large quantities of cold moist air or effluent that is very heavy compared to the ambient air. Once the cold effluent is discharged from the tower, it tends to want to sink or travel to ground because it is so much heavier than the ambient air. The cold effluent is then drawn into the water tower, hindering the heat exchange properties of the tower and causing tower to be inefficient. The aforementioned buoyancy problem causes the recirculation of cold air through water towers, hindering their ability to heat the water and essentially limiting the effectiveness of the towers. 
   Accordingly, there is a need in the art to provide an improved apparatus and method for imparting heat to a circulating fluid by a heating tower apparatus. It is desirable to have such apparatus and method to accomplish the vaporization of LNG that in a efficient and cost effective manner. Furthermore, there is a need in the art to provide a heating tower for use in the LNG vaporization process and/or in a vaporization system that enables the process and/or system to effectively heat water and enable the process to be more efficient and cost effective. 
   SUMMARY OF THE INVENTION 
   The foregoing needs are met, to a great extent, by the present invention, wherein aspects of a heating tower apparatus and method are provided. 
   In accordance with one embodiment of the present invention, a method for heating a fluid using a heating tower is provided, comprising the steps of: drawing an air stream into the heating tower through an inlet; passing the air stream over a fill medium; passing the fluid over the fill medium; discharging the air steam from the heating tower through an outlet; and isolating the inlet air stream from the outlet air stream. 
   In accordance with another embodiment of the present invention, a heating tower apparatus for heating a liquid is provided having an air flow inlet that provides an inlet air flow stream. The inlet includes an inlet duct. The heating tower also includes an air flow outlet that provides an outlet air flow stream. The inlet duct operates to isolate the inlet air flow stream for the outlet air flow stream. The heating tower further includes at least one heating tower cell connected to the inlet duct and the outlet. The heating tower cell comprises a liquid distribution assembly along with a fill medium, wherein the liquid distribution assembly distributes liquid onto the fill medium. 
   In accordance with yet another embodiment of the present invention, a heating tower apparatus for heating a liquid is provided having an air flow inlet that provides an inlet air flow stream. The heating tower also includes an air flow outlet having an outlet duct that provides an outlet air flow stream. The outlet duct operates to isolate the inlet air flow stream for the outlet air flow stream. The heating tower further includes at least one heating tower cell connected to the inlet and the outlet duct. The heating tower cell comprises a liquid distribution assembly along with a fill medium, wherein the liquid distribution assembly distributes liquid onto the fill medium. 
   In accordance with still another embodiment of the present invention, a heating tower apparatus for heating a liquid is provided having an air flow inlet that provides an inlet air flow stream and an air flow outlet that provides an outlet air flow stream. The inlet duct operates to isolate the inlet air flow stream for the outlet air flow stream. The heating tower further includes at least one heating tower cell connected to the inlet duct and the outlet. The heating tower cell comprises a liquid distribution assembly along with a fill medium, wherein the liquid distribution assembly distributes liquid onto the fill medium. The heating tower additionally includes a housing that isolates the inlet air flow stream from the outlet air flow stream. 
   In accordance with another embodiment of the present invention, a heating tower apparatus for heating a liquid is provided. The tower includes an air flow inlet that provides an inlet air flow stream along with a plurality of heating tower cells, each connected to the inlet. Each of the heating tower cells comprises a liquid distribution assembly along with fill medium and an air flow outlet that provides an outlet air flow stream. The heating tower also includes a housing that extends over each of the air flow outlets of the heating tower cells that isolates the inlet air flow stream from the outlet air flow stream. 
   In accordance with yet a further embodiment of the present invention, a heating tower apparatus for heating a liquid is provided, comprising: means for drawing an air stream into the heating tower through an inlet; means for passing the air stream over a fill medium; means for passing the fluid over the fill medium; means for discharging the air steam from the heating tower through an outlet; and means for isolating the inlet air stream from the outlet air stream. 
   In accordance with another embodiment of the present invention, an air guide for a heating tower is provided. The air guide includes an air flow inlet which provides an inlet air flow stream. The air guide also includes an air flow outlet which provides an outlet air flow stream. During operation, the air guide isolates the inlet air flow stream from the outlet air flow stream. 
   In accordance with another embodiment of the present invention, a heating tower apparatus for heating a liquid which falls in a generally downward direction along a vertical axis is provided, comprising: a first air flow inlet that provides a first inlet air flow stream, wherein said first air flow inlet has a first inlet door that moves between an open and a closed position; a second air flow inlet that provides a second inlet air flow stream, wherein said second air flow inlet has a second inlet door that moves between an open and a closed position; a first air flow outlet that provides a first outlet air flow stream, wherein said first air flow inlet has a first outlet door that moves between an open and a closed position; a second air flow outlet that provides a second outlet air flow stream, wherein said second air flow inlet has a second outlet door that moves between an open and a closed position; a liquid distribution assembly; and a fill medium, wherein said liquid distribution assembly distributes liquid onto said fill medium, wherein the heating tower is operable in a first configuration in which said first inlet door is in the open position, said second inlet door is in the closed position, said first outlet door is in the open position and wherein said second outlet door is in the closed position, and wherein the heating tower is operable in a second configuration in which said first inlet door is in the closed position, said second inlet door is in the open position, said first outlet door is in the closed position and wherein said second outlet door is in the open position, and wherein the tower can be switched between the first configuration and the second configuration. 
   In accordance with another embodiment of the present invention, a heating tower apparatus for heating a liquid which falls in a generally downward direction along a vertical axis is provided, comprising: more than one inlet; more than one outlet; a liquid distribution assembly; and a fill medium, wherein said liquid distribution assembly distributes liquid onto said fill medium, wherein each of said more than one inlet and said more than one outlet is selectively openable and closable. 
   In accordance with still another embodiment, a heating tower apparatus for heating a liquid which falls in a generally downward direction along a vertical axis is provided, comprising: a first air flow inlet that provides a first inlet air flow stream, wherein said first air flow inlet has a first inlet door that moves between an open and a closed position; a second air flow inlet that provides a second inlet air flow stream, wherein said second air flow inlet has a second inlet door that moves between an open and a closed position, wherein during operation of the heating tower, said first inlet door is in the open position, said second inlet door is in the closed position; an air flow outlet that provides a first outlet air flow stream, wherein said air flow inlet is connected to a rotatable outlet duct; a liquid distribution assembly; and a fill medium, wherein said liquid distribution assembly distributes liquid onto said fill medium, wherein said outlet duct directionally rotates about the vertical axis over the air flow outlet to isolate the inlet air flow stream from the outlet air flow stream. 
   In accordance with another embodiment of the present invention, a heating tower apparatus for heating a liquid which falls in a generally downward direction along a vertical axis is provided, comprising: a first air flow inlet that provides a first inlet air flow stream, wherein said first air flow inlet has a first inlet door that moves between an open and a closed position; a second air flow inlet that provides a second inlet air flow stream, wherein said second air flow inlet has a second inlet door that moves between an open and a closed position, wherein during operation of the heating tower, said first inlet door is in the closed position and said second inlet door is in the open position; n air flow outlet that provides a first outlet air flow stream, wherein said air flow inlet is connected to a rotatable outlet duct; a liquid distribution assembly; and a fill medium, wherein said liquid distribution assembly distributes liquid onto said fill medium, wherein said inlet duct directionally rotates about the vertical axis over the first and second air flow inlets to isolate the inlet air flow stream from the outlet air flow stream. 
   In accordance with a further embodiment of the present invention, a method for heating a liquid using a heating tower is provided, comprising the steps of: actuating a first inlet door to an open position, opening a first air flow inlet; actuating a first outlet door to an open position, opening a first air flow outlet; drawing an air stream into the heating tower through the first air flow inlet; passing the air stream over a fill medium; discharging the air stream from the heating tower through the first air flow outlet; and isolating the inlet air stream for the outlet air stream. 
   In accordance with still another embodiment of the present invention, a heating tower apparatus for heating a liquid which falls in a generally downward direction along a vertical axis is provided, comprising: a first heating tower cell having a width W; and a second heating tower cell having the width W, adjacent said first heating tower cell, wherein said first heating tower cell and said second heating tower cell are spaced apart a distance D, wherein D is equal to 2W. 
   There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto. 
   In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting. 
   As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side perspective view of a heating tower in accordance with an embodiment of the present invention. 
       FIG. 2  is a cross-sectional view of a cross-flow heating tower cell that may be employed in the heating tower illustrated in  FIG. 1 , in accordance with an embodiment of the present invention. 
       FIG. 3  is a cross-sectional view of a counter flow heating tower cell that may be employed in the heating tower illustrated in  FIG. 1 , in accordance with another embodiment of the present invention. 
       FIG. 4  is a schematic side view of a heating tower cell in accordance with another embodiment of the present invention. 
       FIG. 5  is a top perspective view of a heating tower in accordance with the embodiment of  FIG. 4 . 
       FIG. 6  is a schematic side view of a heating tower in accordance with yet another embodiment of the present invention. 
       FIG. 7  is top perspective view of a heating tower cell in accordance with still another embodiment of the present invention. 
       FIG. 8  is partial cut-away, side perspective view of a heating tower cell in accordance with another embodiment of the present invention. 
       FIG. 9  is a top perspective view of a heating tower cell in accordance with another embodiment of the present invention. 
       FIG. 10  is a schematic plan view of a heating tower configuration in accordance with another embodiment of the present invention. 
       FIG. 11  is a schematic side view of a heating tower in accordance with another embodiment of the present invention. 
   

   DETAILED DESCRIPTION 
   Various preferred embodiments of the present invention provide for a heating tower apparatus and method for heating a liquid such as water or the like. In some arrangements, the heating tower and apparatus are utilized in vaporization or gasification systems and/or processes utilized for the vaporization of liquid natural gas (LNG). It should be understood, however, that the present invention is not limited in its application to LNG vaporization processes, but, for example, can be used with other systems and/or other processes that require the addition of heat to a liquid or the like. Preferred embodiments of the invention will now be further described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. 
   Referring now to  FIGS. 1–3 , a heating tower is depicted, generally designated  10 , having an intake shell or duct  12  that defines an air inlet  13 . The heating tower  10  also includes a plurality of individual heating tower cells  14  connected to the intake shell  12 .  FIG. 2  depicts a cross-flow heating tower cell, generally designated  14   a  while  FIG. 3  depicts counter flow heating tower cell, generally designated  14   b , both of which will be discussed in further detail below. While  FIG. 1  illustrates a heating tower  10  that employs twelve heating tower cells  14  (two are located directly behind the hyperbolic shell and not pictured), the heating tower  10  may employ a varying number of heating tower cells  14  which can generally vary the heating capacity of the heating tower  10 . Similarly, the heating tower  10  may employ entirely all cross-flow heating tower cells  14   a , entirely all counter flow heating tower cells  14   b , or any combination to the two types of heating tower cells  14 . 
   As depicted in  FIG. 1 , the air intake shell  12  is preferably hyperbolic in shape; however, intake shells of varying geometries may be employed. The hyperbolic shaped air intake shell  12  provides a light weight, strong intake duct that defines the heating tower air intake  13  and isolates the air inlet from the heating tower air outlet, which will be discussed in greater detail below. 
   Referring now to  FIG. 2 , a cross-flow heating tower cell  14   a  is schematically depicted, which may be employed in the heating tower  10 . The heating tower cell  14   a  is a mechanical draft heating tower cell  14   a  that includes a water basin  16  and a frame assembly or structure  18  to which the water basin  16  is connected. The frame assembly  18  includes an air inlet, generally designated  20 , which is located above the water basin  16  and an outlet  21 . The cross-flow heating tower cell  14   a  also includes a fan stack or shroud  22  connected to the frame assembly  18  that has an air generator or fan blade assembly disposed therein. The fan blade assembly is rotated by a gear structure which in turn is driven by a motor. 
   As illustrated in  FIG. 2 , the cross-flow heating tower cell  14   a  also includes a water distribution assembly  24  that is schematically depicted. The cross-flow heating tower cell  14   a  also includes a fill assembly, generally designated  28 , that is oriented in a position that opposes the shroud  22  and fan assembly. The fill assembly  28  directly underlies the water distribution assembly  24  and extends along the entire air inlet of the cross-flow heating tower cell  14   a . The fill assembly  28  is made of up of a number of cross-flow film fill packs and each fill pack comprises a plurality of individual cross-flow film fill sheets connected to one another. The film fill packs can be various sizes and dimensions depending upon the size and dimensions of the cross-flow heating tower cell  14   a  in which they are employed. The film fill packs that make up the fill assembly  28  are supported in the cross-flow heating tower cell  14   a  by a water distribution basin structure  30 . In one preferred embodiment, the individual sheets that make up the fillpacks can hang from wire loops which wrap around fill support tubes that run transversely to the sheets. The wire loops then may be attached to the supporting structure such as the basin structure  30 . 
   Referring now to  FIG. 3 , a counter flow heating tower cell  14   b  is schematically depicted, which may be employed in the heating tower  10 . Like the cross-flow heating tower cell  14   a  depicted in  FIG. 2 , the counter flow heating tower cell  14   b  is a mechanical draft heating tower cell  14   b  that includes a water basin  16  and a frame assembly or structure  18  to which the water basin  16  is connected. The frame assembly  18  includes an air inlet, generally designated  20 , which is located above the water basin  16  along with an air flow outlet  21 . The counter flow heating tower cell  14   b  also includes a fan stack or shroud  22  connected to the frame assembly  18 , that has an air generator or fan blade assembly  23  disposed therein. The fan blade assembly is rotated by a gear structure which in turn is driven by a motor. 
   As illustrated in  FIG. 3 , the counter flow heating tower cell  14   b  also includes a water distribution assembly  24  having a plurality of spray nozzles  26 . The counter flow heating tower cell  14   b  also includes a fill assembly, generally designated  32 , however, as the name of the counter flow heating tower cell  14   b  suggests, the fill assembly  32  is a counter flow fill assembly  32 . The fill assembly  32  directly underlies the water distribution assembly  24  like its counterpart in the cross-flow fill assembly  28 , however unlike its counterpart, it extends along the entire horizontal area of the frame assembly  18 , directly above the air inlet  20 . The fill assembly  32  is made of up of a number of counter flow film fill packs and each fill pack comprises a plurality of individual counter flow film fill sheets connected to one another. The film fill packs can be various sizes and dimensions depending upon the size and dimensions of the counter flow heating tower cell  14   b  in which they are employed. The film fill packs that make up the fill assembly  32  are also supported in the counter flow heating tower cell  14   b  by a plurality of horizontally disposed and spaced cross-members (not pictured). 
   Referring now to  FIGS. 1–3 , during operation of the heating tower  10 , water is delivered to the water distribution assembly  24  and the distribution assembly proceeds to the deliver or spray the water onto the fill assemblies  28 ,  32 . While water is sprayed onto the fill assemblies, air is simultaneously pulled through the heating tower cells  14   a ,  14   b  by their respective fan assemblies. The air initially enters the heating tower  10  via the air inlet  13  of the of the intake shell  12  where it then proceeds to the individual air flow inlets of the individual heating tower cells  14   a ,  14   b.    
   As illustrated in  FIG. 2 , as the air flow enters the cross-flow heating tower cell  14   a  through the inlet  20 , it proceeds to flow along a path A, where it contacts and flows through the fill assembly  28 . As a result of this contact with the fill assembly, the heat exchange occurs and the air becomes very cool and moist. The cold moist air or effluent, then proceeds to exit the cross-flow heating tower cell  12   a  through the air flow outlet  21 . Similarly, as illustrated in  FIG. 3 , the air flow enters the counter flow heating tower cell  14   b  through the inlet  20 , beneath the fill assembly  32 , and proceeds to flow along a path B, where it contacts and flows through the fill assembly  32 , where heat exchange occurs and the air becomes very cool and moist. The cold moist air or effluent then exits the counter flow heating tower cell  14   b  through the air flow outlet  21 . However, as illustrated in  FIGS. 2 and 3 , the flow path is such in the cross-flow cell  12   a  that air flows through the cross-flow cell  14   a  along path A, such that it contacts the fill assembly  28  and water in a perpendicular or normal relationship whereas the air flows through the counter flow cell  14   b  along path B such that it, contacts the fill assembly  32  in a concurrent relationship. 
   During operation of the heating tower  10  as described above, the intake shell  12  is positioned with respect to the heating tower cells  14  such that the intake shell  12  functions to isolate the flow of air into the inlet  13  from the outlet flow of effluent exiting the respective outlets  21  of the heating tower cells  14 . This positioning or orientation of the intake shell  12  with respect to the heating tower cells  14  reduces the occurrence of recirculation. More specifically this orientation reduces the occurrence of the heating tower effluent from exiting the cells  14  and re-entering the heating tower  10  through the inlet  13 . 
   The cross-flow heating tower cell  14   a  and counter flow heating tower cell  14   b  depicted in  FIGS. 2 and 3 , respectively, may alternatively be utilized in heating tower arrangements that do not utilize an intake shell or the like. For example, in these arrangements such as the one depicted in  FIG. 10 , the individual cells  14  maybe placed in groupings where the cells  14  are spaced apart a distance D of at least one cell width W, preferably two, and the individual cells  14  are preferably elevated off of the ground. In addition, the heating tower cells  14  may be employed singularly, wherein the single cell defines a heating tower, for example a single cell cross-flow heating tower or a single cell counter flow heating tower. 
   Referring now to  FIG. 4 , a heating tower cell, generally designated  100 , is depicted in accordance with another embodiment of the present invention. The heating tower cell  100  is a mechanical draft heating tower that includes a wet section  102 , a water collection basin  104  a shroud or fan stack  106 , a frame or frame assembly  108  and an upper housing  110  or canopy that extends above the fan stack  106 . The heating tower cell  100  has an air flow inlet  112  and an air flow outlet  114 . 
   The fan stack  106  includes a blade assembly disposed therein that is driven by a motor, while the wet section  102 , includes liquid distributors along with a fill assembly, similar to the previous embodiments. The fill assembly includes a number of film fill packs that are made up of individual film fill sheets. Depending upon the heating tower cell  100  application, the heating tower cell  100  can either function in a cross-flow or counter flow capacity, which is dependent upon the type of film fill sheets utilized in the fill assembly of the wet section  102 . Counterflow is shown because of the air inlet. 
   As illustrated in  FIG. 4 , the upper housing  110  has a first wall  116  that extends upwardly away from the wet section  102 . The upper housing  110  also includes a second wall  118  connected to the first wall  114 , that extends horizontally across the heating tower cell  100 , above the fan stack  106 . The upper housing  110  further includes a third, angled wall, or eave  120 , connected to the second wall  118 , that extends at an angle downwardly and away from the heating tower cell  100  a distance below the fan stack  106 . 
   During operation of the heating tower cell  100 , water is delivered to the wet section  102  where the spray nozzles proceed to spray the water onto the fill assemblies. While water is sprayed onto the fill assemblies, air is simultaneously pulled through the heating tower cell  100  by the fan assembly. The air initially enters the heating tower cell  100  via the air inlet  112  and proceeds to flow along an initial path C, where it flows through the wet section  102  and contacts the fill assembly. As the air passes through the fill assembly of the wet section  102 , heat exchange occurs and the air becomes very cool and moist. The cold moist air or effluent, then proceeds to exit the heating tower cell  100  through the fan stack  106 . Once the effluent exits the heating tower cell  100 , the upper housing  110  directs the flow of effluent downward and outward, away from the heating tower cell  100  as indicated by the arrow D. 
   During the aforementioned operation of the heating tower cell  100  as described above, the upper housing  110  functions to isolate the flow of effluent from the flow of air entering the inlet  112 . Once the effluent exits the heating tower cell via the fan stack  106 , the air contacts the walls  116 ,  118 ,  120  of upper housing which force the effluent in a direction opposite the inlet  112 , as indicated by the arrow D, reducing the likelihood of recirculation occurring. More specifically, the use of the upper housing  110  and, the action of its walls  116 ,  118 ,  120 , reduces the occurrence of the heating tower effluent from exiting the heating tower cell  100  and re-entering the cell  100  through the inlet  112 . Upper housing wall configuration is not limited to that shown, but, for example, walls  116  and  118  could be replaced by three or more straight wall segments that provide more of a curvature approximation. Furthermore, the upper housing  110  may be curvilinear. 
   Like the embodiments described previously, the heating tower cell illustrated in  FIG. 4  may also be used in combination with an intake shell that extends from the inlet  112 . Also, the heating tower cell  100  may be used in combination with multiple similar heating tower cells to form a large multi-cell heating tower, such as with a hyperbolic shell similar to  FIG. 1 . 
     FIG. 5  depicts a multi-cell heating tower, generally designated  122 , that employs four heating tower cells  100 , each similar to that illustrated in  FIG. 4 . Each of the cells  100  has an upper housing  110  that combines to form a roof or canopy  123  over all the fan stacks of the respective heating tower cells  100 . In the embodiment depicted, the heating tower cells  100  have a common inlet  124  where air enters the to heating tower  122 . The common inlet  124  functions like an air inlet shell, similar to that depicted on the embodiment illustrated in  FIG. 1 . The common inlet  124  combines with the roof or canopy  123  to reduce the occurrence of the heating tower effluent from exiting the heating tower cells  100  and re-entering the heating tower  122  through the air inlet  124 . 
   Referring now to  FIG. 6 , a cross-flow heating tower cell  200  is depicted, in accordance with an alternative embodiment of the present invention. The heating tower cell  200  is a mechanical draft heating tower cell  200 , similar to the previous embodiments described, that includes a water basin  16  and a frame assembly or structure  18  to which the water basin  16  is connected. The heating tower cell  200  is preferably elevated or raised off of the ground like the previous embodiments, however the this elevation is not necessarily required for proper operation. The cross-flow heating tower cell  200  also includes a fan stack or shroud  202  connected to the frame assembly  18  that defines an air inlet  204 . The fan stack  202  has an air generator or fan blade assembly disposed therein. The fan blade assembly is rotated by a gear structure which in turn is driven by a motor. 
   As illustrated in  FIG. 6 , the cross-flow heating tower cell  200  also includes a water distribution assembly  24  along with an air flow outlet, generally designated  206 . The cross-flow heating tower cell  200  also includes a fill assembly, generally designated  28 , that directly underlies the water distribution assembly  24  and extends across the entire outlet  206  of the cross-flow heating tower cell  200 . The fill assembly  28  is made of up of a number of cross-flow film fill packs and each fill pack comprises a plurality of individual cross-flow film fill sheets connected to one another. The film fill packs can be various sizes and dimensions depending upon the size and dimensions of the cross-flow heating tower cell  200  in which they are employed. The film fill packs that make up the fill assembly  28  are supported in the cross-flow heating tower cell  200  by wire loops or the like, which wrap around fill support tubes that run transversely to the individual sheets of the packs. The wire loops then may be attached to the supporting structure such as the basin structure  30 . 
   During operation of the cross-flow heating tower cell  200 , water is delivered or sprayed onto the fill assembly  28  via the water distribution assembly  24 . While water is sprayed onto the fill assembly  28 , air is simultaneously pulled through the cross-flow heating tower cell  200  by the fan assembly. The air initially enters the heating tower  200  via the air inlet  204 , where it then proceeds to contact the fill assembly  28 . 
   As illustrated in  FIG. 6 , as the air flow enters the cross-flow heating tower cell  200  through the inlet  204  and it proceeds to flow along a path E, where it contacts the fill assembly  28  in a perpendicular or normal relationship, and flows through the wet fill assembly  28  causing heat exchange to occur. Again, due to this contact the air becomes very cool and moist. The cold, moist air or effluent, then proceeds to exit the cross-flow heating tower cell  200  through the air flow outlet  206 . 
   During operation of the cross-flow heating tower cell  200  as described above, the fan stack or shroud  202  functions to isolate the flow of air into the inlet  204 , from the outlet flow of effluent exiting the outlet  206 . This positioning or orientation of the fan stack  202  in relation to the outlet  206 , reduces the occurrence of recirculation. More specifically, this orientation reduces the occurrence of the heating tower effluent from exiting the cell  200  and re-entering the cell through the inlet  204 . 
   Referring now to  FIG. 7 , a heating tower, generally designated  300 , is illustrated in accordance with another embodiment of the present invention. As depicted in  FIG. 7 , the heating tower includes an air inlet duct  302  through which the heating tower effluent travels as the air enters the heating tower  300 . Similar to the embodiment depicted illustrated in  FIGS. 1–3 , the heating tower  300  includes a plurality of individual heating tower cells  14  that are connect to the air inlet duct  302 , and to one another, in an opposed, series relationship. Like the embodiments discussed previously in  FIGS. 1–3 , the heating tower cells  14  utilized in the tower  300  are each mechanical draft heating tower cells  14  having a fan stack our shroud  303  having a fan assembly disposed therein. The fan stacks  303  of each of the heating tower cells  14  combine to define the air flow outlet(s) of the heating tower  300 . Also, the heating tower cells  14  may be either a cross-flow design, similar to that depicted in  FIG. 2 , or a counter flow design, similar to that depicted in  FIG. 3 . 
   While  FIG. 7  illustrates a heating tower  300  that employs twelve heating tower cells  14 , the heating tower  300  may employ a varying number of heating tower cells  14 , enabling the end user to adjust the heating capacity of the heating tower  300 . Similarly, the heating tower  300  may employ entirely all cross-flow heating tower cells  14 , entirely all counter flow heating tower cells  14 , or any combination to the two types of heating tower cells  14 . 
   As depicted in  FIG. 7 , the air inlet duct  302  is preferably rectangular in shape, having two end sections  304  and a middle section  306 . Each of the sections include opposing top and bottom walls connected to two opposing side walls  310 . Though an air inlet duct  302  having a generally rectangular geometry is depicted, inlet ducts  302  of varying geometries may be employed. In the illustrated embodiment, the air inlet duct defines a dual, air flow inlet  312  for the heating tower  300  which and functions to isolate the air inlet  312  from the heating tower air outlets of the individual heating tower cells  14 . 
   During operation of the heating tower  300 , air is pulled into the heating tower  300  through the heating tower cells viaducts  302  as indicated by arrows G. The air proceeds to flow into the wets sections of the respective heating tower cells  14 , where the heat exchange occurs, similar to the embodiments depicted in  FIGS. 1–6 . As the air flows through the wet sections, it imparts its heat upon the falling liquid and the air temperature significantly becomes cooler. The cold air or effluent then proceeds to exit each of the individual heating tower cells  14  through the stack  303  of the individual cells  14 , as indicated by arrow G′. 
   During the aforementioned operation of the heating tower  300 , the air flow inlet duct  302  functions to isolate the inlet airflow entering the individual heating tower cells from the effluent air being discharged from the stacks  303 , reducing the likelihood of recirculation occurring. 
   Alternatively, the heating tower depicted in  FIG. 7 , and the individual cells  14 , may be reconfigured so that the air inlet duct  302  functions as an outlet duct through which the heating tower effluent travels as the effluent exits the heating tower  300 . Similar to the embodiment depicted illustrated in  FIGS. 1–3 , the heating tower  300  includes a plurality of individual heating tower cells  14  that are connected to the air outlet duct  302 , and to one another, in an opposed, series relationship. Like the embodiments previously discussed, the heating tower cells  14  utilized in the tower  300  are each mechanical draft heating tower cells  14  having a fan stack our shroud  303  having a fan assembly disposed therein. In this reconfigured embodiment, however, the fan stacks  303  of each of the heating tower cells  14  now combine to define the air flow inlet(s) of the heating tower  300  instead of the outlet. 
   During operation of the heating tower  300  with that alternative configuration, as previously described, air is pulled into the heating tower  300  through the heating tower cells via each of the fan stacks  303  as indicated by the arrows H. The air proceeds to flow into the wet sections of the respective heating tower cells  14 , where the heat exchange occurs, similar to the embodiments depicted in  FIGS. 1–6 . As the air flows through the wet sections, it imparts its heat upon the falling liquid and the air temperature significantly becomes cooler and accumulates the moisture. The cold air or effluent then proceeds to exit each of the individual heating tower cells  14  where it enters the air flow outlet duct  302 , as indicated by arrows H′. 
   Referring now to  FIG. 8 , a heating tower cell, generally designated  400 , is illustrated in accordance with another embodiment of the present invention. The heating tower cell  400  is similar to the previous embodiments depicted in  FIGS. 1–7 . The heating tower cell  400  can be oriented to perform in a cross-flow heating tower arrangement or configuration, similar to that illustrated in  FIGS. 2 and 6 , or the heating tower cell  400  can be oriented to perform in a cross-flow heating tower arrangement or configuration, similar to that illustrated in  FIG. 3 . However, whereas the embodiment depicted in  FIG. 3  employs a side stack, the embodiment depicted in  FIG. 8  employs a vertical stack. 
   Like the embodiments previously described in connection with  FIGS. 1–7 , the heating tower cell  400  is a mechanical draft tower cell  400  that includes a water basin (not pictured) and a lower housing  401 . The lower housing  401  includes a wet section  402  along with the water basin and is composed of four sides  404 . The heating tower cell  400  also includes a first air inlet  403   a  and a second air inlet  403   b  which opposes the first air inlet  403   a . Each the air inlets  403   a ,  403   b  have a plurality of inlet doors or louvers  405 , which function to control the flow of air through the inlets  403   a ,  403   b , as desired during heating tower cell  400  operation. The heating tower cell  400  also includes a shroud or fan stack  407  mounted on top of the lower housing  401  that has an air generator or fan blade assembly disposed therein. The fan blade assembly is rotated by a gear structure which in turn is driven by a motor. 
   The wet section  402 , like those of the previously discussed embodiments, includes liquid distributors along with a fill assembly, both of which are not pictured for the purposes of clarity. The fill assembly includes a number of film fill packs that are made up of individual film fill sheets. Depending upon the heating tower cell  400  application, the heating tower cell can either be fitted with counter flow film fill sheets or cross-flow film fill sheets, and therefore the cell may either function as a counter flow cell in counter flow tower or a cross-flow cell in a cross-flow tower. 
   As illustrated in  FIG. 8 , the heating tower cell  400  also includes an upper housing or outlet housing  406 , that is mounted to or connected to the lower housing  401 . The outlet housing  406  includes two opposing end walls  408  extending upwardly from the lower housing  401  which are connected to two opposing side walls  410 , which also extend upwardly from the lower housing  401 . The outlet housing  406  also includes a first air outlet  412 , positioned in a downward sloping orientation and a second air outlet  414 , positioned opposite the first air outlet  412 , in a downward sloping orientation. Each of the air outlets  412 ,  414  include a series of louvers or doors  416  that extend horizontally between the end walls  408  of the outlet housing  406  that function to control the flow of air or effluent out of the respective outlets  412 ,  414 . 
   In the embodiment illustrated in  FIG. 8 , the air flow inlets  403   a ,  403   b  of the heating tower cell  400  are illustrated on opposing side walls only, however, the heating tower cell  400  may have multiple air inlets  403 , similar to the ones depicted, on all four sides  404  of the lower housing  401 . Each of the multiple air inlets also include inlet louvers or doors  404 , that extend horizontally along the entire length of the walls. Similarly, the air outlets  414  do not have to be positioned on opposing sides, in a downward sloping orientation. Alternatively, the upper housing  406  may have a generally square or rectangular geometry, similar to the lower housing  401 , having multiple air outlets  414 , similar to that depicted, each located or extending along the four sides  408 ,  410  of the upper housing  406 . Each of the multiple air outlets  412 ,  414  also include outlet louvers or doors  406 , that extend horizontally along the entire length of the outlets. 
   During operation of the heating cell  400 , water is delivered to the wet section  402  where nozzles proceed to distribute the water onto the fill assembly whether it be cross-flow or counter flow. While water is distributed onto the fill assembly, air is simultaneously pulled through the heating tower cell  400  by the fan assembly. As indicated by the arrows F, the air initially enters the heating tower cell  400  via the air inlet  403   a  and proceeds to flow into and through the wet section  402 , where it contacts the fill assembly. As the air passes through the wet section  402 , heat exchange occurs and then becomes very cool and moist. The cool, moist air, or effluent, then proceeds to exit the heating tower cell  400  through the fan stack  407 . 
   As illustrated in  FIG. 8 , the fan stack  407  is disposed on top of lower housing within the upper housing  406 , thus, once the effluent exits the heating tower cell  400 , it enters the upper housing  406 . In the embodiment depicted, the heating tower cell  400  is configured such that the louvers  416  of the first air outlet  412  are closed, closing the outlet  412 , while the louvers or doors  416  of the second air outlet  414  are open. Therefore, upon entering the upper housing  406 , the air proceeds to exit the heating tower cell  400  through the second air outlet  414  as indicated by the arrow F. 
   During operation of the heating tower cell  400 , the upper housing  406 , in combination with the louvers  416  of the air outlet  414 , functions to isolate the flow of effluent from the fan stack  407  from the air entering the inlet  403 . Once the effluent exits the heating tower cell  400  via the fan stack  407 , the effluent is prevented from exiting the upper housing  406  through the first air outlet  412 , because the louvers  416  are closed. The effluent is therefore essentially forced or directed to exit via the second air outlet  414 . The effluent therefore exits the heating tower cell  400  on the side opposite the air inlet  403 , reducing the likelihood that recirculation will occur. More specifically, the utilization of the second air flow outlet  414  in combination with the first air inlet  403   a , reduces the occurrence of the heating tower cell  400  effluent from exiting the heating tower cell  400  and re-entering the cell  400  through the inlet  403   a.    
   Also during operation, the heating tower cell  400  may operate using an alternate configuration then that illustrated in  FIG. 8 . The heating tower cell  400  may also operate via configuration, wherein the first inlet  403   a  is closed along with the second outlet  414 , and the second air inlet outlet  403   b  is open along with the first air outlet  412 . While in this configuration, air flows in the heating tower cell  400  via the second inlet  403   b  and though the wet section  402  and out the fan stack  407 , as described in connection with the previous embodiment. However, contrary to the configuration depicted in  FIG. 8 , the effluent exits the fan stack  407  and proceeds to exit the upper housing  406  through the first outlet  412 , opposite the second air inlet  403   b.    
   Like the configuration illustrated in  FIG. 8 , the above-described alternate configuration louvers  416  of the first air outlet  412 , functions to isolate the flow of effluent of the heating tower cell  400  from the air entering the second inlet  403   b . Once the effluent exits the heating tower cell  400  via the fan stack  407 , the effluent is now prevented from exiting the upper housing  406  through the second air outlet  414 , because the louvers  416  are closed. The effluent is therefore forced or directed to exit via the first air outlet  412 . The effluent therefore exits the heating tower cell  400  on the side opposite the second air inlet  403   b , reducing the likelihood that recirculation will occur. More specifically, the closing of the louvers  416  on the second air outlet  414 , while opening the louvers  416  on the first air outlet  412 , in combination with utilizing the second inlet  403   b , reduces the occurrence of the effluent from exiting the heating tower cell  400  and re-entering the cell  400  through the second inlet  403   b.    
   The louvers  405  and  416  of the inlets  403  and outlets  412 ,  414 , respectively, preferably are actuated between the open and closed positions by mechanical actuators. The actuators are operated by a control  418  which allows the heating tower cell  400  operator to select or designate which inlets  403  or outlets  412 ,  414  to open or close during cell  400  operation, for example in response to atmospheric conditions, such as wind direction. Also, the controller  418  may include a sensing means that senses the atmospheric conditions, or changes in the atmospheric conditions, and automatically changes the configuration of the heating tower cell by opening and closing the air flow inlets and outlets accordingly. 
   Referring now to  FIG. 9 , a heating tower cell  500  is illustrated, which is an alternative embodiment of the heating tower cell  400  depicted in  FIG. 8 . The heating tower cell  500  is similar to that illustrated in  FIG. 8 , however the heating tower cell  500  depicted in  FIG. 9  employs an exhaust duct or port  502  instead of an upper housing  406 . 
   As illustrated in  FIG. 9 , the exhaust port  502  is connected to the fan stack  407  and provides a pathway for the heating tower effluent to exit, away from the inlet  403   a . During the operation of the heating tower cell  500 , the effluent exits the heating tower cell  500  via the fan stack  407  and proceeds through the exhaust port  502 . The exhaust port  502  acts to direct the effluent along a path outward, away from the heating tower cell  500 , as indicated by arrow F. This path reduces the likelihood of recirculation occurring. More specifically, the exhaust duct  502  functions to reduce the occurrence of the heating tower cell effluent from exiting the heating tower cell  500  and re-entering the cell  500  through the inlets  403   a  and  403   b.    
   The exhaust duct  502  of the heating tower cell  500  is preferably rotated about the fan stack  407  by a mechanical rotation means. Like the actuators in the embodiment depicted in  FIG. 8 , the mechanical rotation means is operated by the control  418  which allows the heating tower cell  500  operator to select a desired position for the exhaust duct  502  during cell  500  operation, for example in response to atmospheric conditions, such as wind direction. Also, the controller  418  may include a sensing means that senses the atmospheric conditions, or changes in the atmospheric conditions, and automatically rotates the exhaust duct  502  to a predetermined or pre-programmed position. 
   Referring now to  FIG. 10 , a schematic plan view of a heating tower configuration, generally designated  600 , is depicted in accordance with an alternative embodiment of the present invention. As illustrated in  FIG. 10 , the individual heating tower cells  14  of the heating tower configuration  600  each have a width W while they are spaced apart a distance D. In some heating tower configurations, for example, the heating tower cell width W may range from approximately 30′ to approximately 60′ while in other configurations the width W of the individual cells may range from approximately 50′ to approximately 60′. In one preferred embodiment, the distance D between the individual heating tower cells  14  is preferably twice the width W of the heating tower cells  14 , or equal to approximately 2W. 
   Referring now to  FIG. 11 , a side, schematic view of a heating tower is illustrated, generally designated  700 . The heating tower  700  is preferably a mechanical draft heating tower having opposing air inlets  702  and  704  along with a first series of blade type damper doors  706  which correspond to the first inlet  702  and a second series of blade type damper doors  708  which correspond to the second inlet  704 . While blade type damper doors  706 ,  708  are illustrated in  FIG. 11 , the heating tower  700  may alternatively employ damper doors other that the blade type ones depicted, for example roll-up doors. The first series of damper doors  706  function to control inlet air flow through the first inlet  702  while the second series of damper doors  708  function to control inlet air flow through the second inlet  704 . The heating tower further includes a wet section  710  located generally above the inlets  702 ,  704  for counterflow or horizontally adjacent the inlets  702 ,  704  for crossflow along with a fan stack  712  connected to the wet section  710 . As illustrated in  FIG. 11 , the heating tower  700  also includes a series of rotatable vanes  714  that are connected to the fan stack  712  and extend across the heating tower outlet, generally designated  716 . 
   During operation of the heating tower  700 , water is delivered to the wet section  710  similar to that described in connection with the previous embodiments, while air is simultaneously pulled through the heating tower  700  by a fan assembly. In the configuration depicted, the first damper doors  706  are open while the second  708  are closed. Therefore, the air enters the heating tower  700  via the first air inlet  702  and proceeds to flow along an the path I, where it flows through the wet section  710  and contacts the fill assembly. As the air passes through the fill assembly of the wet section  710 , heat exchange occurs and the air becomes very cool. The cold air or effluent, then proceeds to exit the heating tower  700  through the fan stack  712 . As the effluent exits the heating tower  700 , the rotatable vanes  714  function to isolate the flow of effluent from the fan stack  712  from the air entering the inlet  702 . 
   As illustrated in  FIG. 11 , the rotatable vanes direct the effluent to exit the heating tower  700  on the side opposite the air inlet  702 , as indicated by the airflow stream I, reducing the likelihood that recirculation will occur. More specifically, the utilization of the rotatable vanes  714  in combination with the first air inlet  702 , reduces the occurrence of the heating tower  700  effluent from exiting the heating tower  700  and re-entering the tower  700  through the inlet  702 . 
   Also during operation, the heating tower  700  may operate using an alternate configuration then that illustrated in  FIG. 11 . The heating tower  700  may also operate via a configuration, wherein the first series of damper doors  706  are closed, while the second series of damper doors  708  are open. In this configuration, the rotatable vanes  714  are rotated in a direction opposite the second inlet  704 . While in this configuration, air flows into the heating tower  700  via the second inlet  704  and though the wet section  710  and out the fan stack  712 , as described in connection with the previous embodiment. However, contrary to the configuration depicted in  FIG. 11 , the effluent exits the fan stack  712  opposite the second air inlet  704 . 
   The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.