Abstract:
An atmospheric cooling tower apparatus includes a housing structure having an air inlet and an air outlet, a first evaporative heat transfer media disposed in the housing, and a closed coil heat transfer media disposed in the housing. A water distribution assembly is disposed above the evaporative heat transfer media and configured to distribute water onto the evaporative fill heat transfer fill media. A collection basin is disposed beneath the evaporative heat transfer media configured to collect water that has passed through the evaporative heat transfer media. A first control valve controls an inflow of water to supply water to one or both of the evaporative heat transfer media and the closed coil heat transfer media. The closed coil heat transfer media and the evaporative heat transfer media are disposed laterally next to each other.

Description:
FIELD OF THE INVENTION 
     The invention pertains generally to the field of cooling towers which cool a warm liquid by interaction with cooler ambient air. 
     BACKGROUND OF THE INVENTION 
     Cooling towers are in wide use in industry. These towers are typically used to receive a warm or relatively warm fluid, such as, for example, warm water from an industrial operation. The warm water is passed through the tower and, by a heat exchange interaction with ambient air that is cooler than the water, the water is cooled and then can be discharged or returned to the industrial operation. Cooling towers include various configurations such as cross-flow cooling towers in which the air enters from a side of the tower and passes generally laterally horizontally across the fill media, and also counterflow cooling towers where the air generally enters beneath the fill material and is drawn upward through the fill material. 
     There are at least two general types of such cooling towers. The first general category includes evaporative type systems in which the water enters the top of the tower and falls through the tower while interacting with splash bars and/or sheet fill packs, also referred to herein as wet media. The water itself thus has contact with the ambient air and is cooled by its contact with the air, and then is collected in a lower collection basin. Evaporative cooling towers can take many configurations, and typically utilize a fan to move air through the tower and past the liquid being cooled, although natural draft cooling towers without fans are also known. 
     In evaporative cooling towers, depending on the operating and ambient conditions, some of the water will tend to evaporate and exit the tower with the exiting air. In some cases, the water vapor may exit the tower in the form of a visible water vapor or plume which is sometimes considered undesirable depending on location and other circumstances. 
     Another general category of cooling towers is closed circuit or dry cooling towers. A dry cooling tower contains the liquid to be cooled inside a conduit and air interacts with the conduit material and thus cools the liquid. The dry approach has the advantage that there is no evaporation into the cooling air and thus no plume. However, depending on the operating and ambient temperatures, in some cases dry cooling can be less efficient than wet cooling in terms of the energy consumption and/or construction expense of the tower. Moreover, dry cooling tends in some circumstances to be more dependent on the ambient temperature, and thus less suitable for climates where the weather and ambient temperature change through a wide range. Dry cooling towers can also use one or more fans or can be natural draft. 
     There are also known so-called hybrid towers which pass the fluid through a combination of evaporative and dry heat exchangers. In the prior art these combination or hybrid cooling towers have operated in a single mode where the water passes serially through one type of heat exchanger media (wet or dry) and then is recollected and passes through a second different type of heat exchanger media (wet or dry). The water travels serially through the two heat exchangers. Turning to air flow, it has been known to arrange the media so that each heat exchanger is contacted by its own air path. That is, the air paths through the two types of heat exchangers are separated from each other, at least to some extent, and thus the air itself passes through one or the other media section in a parallel fashion. In the parallel fashion of air flow, one air stream passes through one media and a second different air stream passes through the other media. It has been known to subsequently mix these two air streams for discharge from the tower. A potential difficulty in operating and designing such hybrid systems is that the optimum configuration for reducing plume is dependent on the operating and ambient temperatures, and when these temperatures vary, for example due to seasonal changes, there can be too much plume, or less than optimal efficiency. 
     Accordingly, it would be desirable to have a cooling tower that can provide desirable efficiencies while also reducing plume. 
     SUMMARY OF THE INVENTION 
     Some embodiments according to the present invention provide a cooling tower and method that can provide desirable efficiencies while also reducing plume. 
     An atmospheric cooling tower apparatus includes a housing structure having an air inlet and an air outlet, a first evaporative heat transfer media disposed in the housing, a closed coil heat transfer media disposed in the housing, a first water distribution assembly disposed above the first evaporative heat transfer media configured to distribute water onto the first evaporative fill heat transfer fill media, a first collection basin disposed beneath the first evaporative heat transfer media configured to collect water that has passed through the first evaporative heat transfer media, a first control valve that controls an inflow of water to supply water to one or both of the first evaporative heat transfer media and the closed coil heat transfer media, wherein the first control valve has one position where all of the water is supplied to the first evaporative heat transfer media, and another position where all of the water is supplied to the closed coil heat transfer media, wherein the closed coil heat transfer media and the first evaporative heat transfer media are disposed laterally next to each other and wherein a first air path is defined between the first water distribution assembly and the first collection basin, through the first evaporative heat transfer media, and through the closed coil heat transfer media. 
     Another embodiment includes an atmospheric cooling tower apparatus with a housing means having an air inlet and an air outlet, a first evaporative heat transfer means disposed in the housing, a closed coil heat transfer means disposed in the housing, a first water distribution means disposed above the first evaporative heat transfer means configured to distribute water onto the first evaporative fill heat transfer fill means, a first collection means disposed beneath the first evaporative heat transfer means configured to collect water that has passed through the first evaporative heat transfer means, a first control valve means that controls an inflow of water to supply water to one or both of the first evaporative heat transfer means and the closed coil heat transfer means, wherein the first control valve means has one position where all of the water is supplied to the first evaporative heat transfer means, and another position where all of the water is supplied to the closed coil heat transfer means, wherein the closed coil heat transfer means and the first evaporative heat transfer means are disposed laterally next to each other and wherein a first air path is defined between the first water distribution means and the first collection means, through the first evaporative heat transfer means, and through the closed coil heat transfer means. 
     Yet another embodiment of the atmospheric cooling method for a tower apparatus having a housing structure having an air inlet and an air outlet, includes distributing water to a first evaporative heat transfer media disposed in the housing using a first water distribution assembly disposed above the first evaporative heat transfer media configured to distribute water onto the first evaporative fill heat transfer fill media, distributing water to a closed coil heat transfer media disposed in the housing, collecting water using a first collection basin disposed beneath the first evaporative heat transfer media configured to collect water that has passed through the first evaporative heat transfer media, controlling an inflow of water to supply water to one or both of the first evaporative heat transfer media and the closed coil heat transfer media using a first control valve, wherein the first control valve has one position where all of the water is supplied to the first evaporative heat transfer media, and another position where all of the water is supplied to the closed coil heat transfer media, wherein the closed coil heat transfer media and the first evaporative heat transfer media are disposed laterally next to each other and wherein a first air path is defined between the first water distribution assembly and the first collection basin, through the first evaporative heat transfer media, and through the closed coil heat transfer media. 
     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 schematic and cross-sectional view providing a diagram of a cooling tower according to a first preferred embodiment of the invention. 
         FIG. 2  is a diagrammatic air flow view corresponding to the view and embodiment of  FIG. 1 . 
         FIG. 3  is another diagrammatic air flow view corresponding to the view and embodiment of  FIG. 1 . 
         FIG. 4  is a schematic and cross-sectional view providing a diagram of a cooling tower according to a second preferred embodiment of the invention. 
         FIG. 5  is a diagrammatic air flow view corresponding to the view and embodiment of  FIG. 4 , and showing further variations. 
         FIG. 6  is a diagrammatic air flow view corresponding to the view and embodiment of  FIG. 4 , and showing further variations. 
         FIG. 7  is a schematic and cross-sectional view providing a diagram of a cooling tower according to another preferred embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Some embodiments according to the invention provide a cooling tower and method that can provide desirable efficiencies while also reducing plume. Examples of preferred embodiments will now be described with reference to the drawing figures, in which like reference numbers refer to like parts throughout. 
       FIG. 1  is a schematic diagram of a first preferred embodiment of the invention. In this embodiment, a generally or completely symmetrical structure is provided, where air enters the side of the tower  10 , passes through various media, as shown, and exits out the top of the tower  10 . The cooling tower  10  includes a fan  12  which draws air out of an air outlet structure  14 . The tower  10  also has an internal framework (not illustrated) which supports the various components that will be discussed. The tower  10  may have a basin cover  16  forming a roof of the tower, or may simply have an open roof. Turning next to the water flow, relatively warm water or other liquid to be cooled is supplied to the tower via water inlet conduit  18 , as shown. The tower  10  has two sides which are essentially mirror images of each other. For convenience, one side is discussed below, and both sides have reference numbers. 
     The water supplied to inlet  18 , which is referred to herein as inlet water, may in some exemplary industrial applications may range from 80° F. to 120° F. Although water is described in the following examples, various embodiments can be used with other fluids, including treated water or other liquids, any or all of which are referred to as water herein. The inlet hot water is passed to a three-way diverter valve, or control valve  20 . The operation of this control valve  20  will be discussed in more detail below. In one configuration, the control valve  20  directs all or some of the water through a conduit  22  so that it enters an upper water distribution basin  24 . The water distribution basin  24 , for example, can take the form of a tray having nozzles therethrough so that water is collected in the water distribution basin  24  and drips downward from the nozzles of the tray in a distributed fashion. 
     As it drops, the water will contact and pass through an upper heat exchange media  26 . The upper heat exchange media  26  in this example is an evaporative fill media such as a series of splash bars or a sheet fill pack. 
     After falling through the evaporative media  26 , the water is collected in an intermediate distribution tray, or re-distribution tray,  28 . The re-distribution tray  28  is similar in structure to distribution tray  24 . The water in the re-distribution tray  28  falls downward onto a lower heat transfer media  30 , which in this example is also an evaporative media such as a splash bar or sheet fill pack media. Some embodiments thus have both upper and lower evaporative media. Moreover, in some embodiments having both of these be a film fill type media is also preferred. However, as will be illustrated for example with respect to a version of the second embodiment, shown in  FIGS. 5 and 6 , there may be instances where one or the other of the upper media  26  or the lower media  30  may be a closed dry media, such as a coil type. Also either of the upper media  26  and lower media  30  can be a compound media, wherein liquid is to be cooled passing through a coil and also another liquid is being sprayed over the coil. 
     Returning to  FIG. 1 , a lower water collection basin  31  is located at the bottom of the tower  10  to collect water for discharge from the tower. After being cooled, the water is collected in the lower water collection basin  31 . The water in the water collection basin  31  can be extracted by a pump or gravity flow and returned to the process location or exhausted into the environment. 
     The control valve  20  may also direct the water into a conduit  34  where it enters a closed circuit heat transfer coil  32 . This water travels through the coil  32  and is cooled by the coil operating as a closed circuit heat exchanger with the ambient air. The water exits the coil  32  via conduit  35  at which point it can be collected by the re-distribution tray  28 . In an example of an optional embodiment, the discharge conduit of the coil  32  may be connected to a second control valve  36  which can divert the water leaving the coil  32  so that instead of entering the re-distribution basin  28 , it instead is directed to a bypass conduit  38  which directs the water directly to the lower water collection basin  31 , and thus the water bypasses the intermediate collection basin  28  in this mode. This feature is optional as are many other features described herein, such as for example a purely closed loop mode that is discussed farther below. 
     Continuing with  FIG. 1 , it will be appreciated that when the control valve  20  is a gradual diverter valve, it can gradually shift the operation of the upper section of the tower such that the water flow can transition between (1) a fully evaporative condition (with all the water entering the conduit  22 , the top distribution basin  24 , and passing through the media  26  to be collected in the intermediate tray  28 ), and (2) when the valve is operated in completely the other direction, the top section of the tower operates as a purely closed circuit tower (with all of the water being directed through the coil  32  and exiting the coil  32  and upon exit of the coil  32 , depending on the condition of the secondary valve  36 , the water being directed either into the intermediate distribution tray  28  or sent directly to the lower water basin  31 ). 
     The top section of the tower  10  can also be operated with the inlet water supply being split fractionally as a percentage by the control valve  20  so that some of the water is operating in an evaporative condition through the media  26  and another proportion of the water is operating in a closed dry configuration through the coil  32 . Again, water may be sent after it has passed through the coil  32  either through the lower media  30  or can bypass the lower media  30  directly into the lower basin  31 . The coil  32  is illustrated as being outward of the media  26 ; however, if desired the coil  32  can be inbound of the media  26 , which may have benefits such as protection of the coil  32  from the elements and/or external debris. 
       FIGS. 2 and 3  further illustrate the air flow through the system of  FIG. 1  and also depict an arrangement wherein the lower air inlets of the tower feature dampers  40  that can be opened or closed. In  FIGS. 2 and 3 , dashed lines indicate a heat exchange media that is not in use, and the arrows represent active air flow paths.  FIG. 2  shows a mode of operation where the water is being sprayed over the upper fill  26 , is recollected and also passes through the lower fill  30 . In  FIG. 3  the left side shows a mode of operation which may for example be a purely closed dry configuration in which fluid is flowing only through the coil  32 . Thus, the dampers  40  can be closed off and air is drawn only through the coil  32 . This completely dry operation would be most desirable in the case of very cool conditions. In this mode shown on the left side of  FIG. 3 , the bypass valve  36  (see  FIG. 1 ) is activated in the configuration of  FIG. 3  so that the liquid also does not fall over the lower fill  30 , although in some embodiments the water may fall over the tower fill. The right side of  FIG. 3  shows a configuration in which the dampers  40  are open and air is flowing both over the coil  32  and the lower media  30 . This shows an operation wherein the upper section the coil  32  is being used, and in the lower half the fill media  30  is being used. 
       FIGS. 2 and 3  show the extreme end point modes, in which in the upper section of the tower all the water is passing through only one or the other of the evaporative media  26  ( FIG. 2 ) or the coil  32  ( FIG. 3 ). However, although not specifically depicted in its own figure, it will be appreciated that the control valve  20  is a continuously adjustable valve in some embodiments, so that any proportion of the water in the upper section of the tower may be passing through one or the other of the two upper fill media  26  and  32 . Also, the bypass valve  36  can be a continuous adjustable valve to control a traditional flow through the lower media  30 . 
       FIG. 4  is a view similar to  FIG. 1 , but shows a tower  50  that is essentially one-sided. The systems being depicted in  FIG. 4  are thus similar to one side of  FIG. 1  except that a solid end wall  54  is provided.  FIG. 4  also schematically depicts the concepts of exit air mixing baffles  52 . The air baffles  52  may be provided to enhance mixing of the upper air flow with the lower air flow before the air is exhausted from the tower. In some situations, the lower air flow may tend to have more water vapor suspended in it compared to the upper air flow, and if these paths remain unmixed, there can tend to be plume from the higher water vapor air flow. Mixing the air flows in some circumstances can thus reduce the plume overall. The baffles  52  are illustrated solely in a schematic nature, and any of the wide variety of air mixing baffles that are known could be utilized, as well as other air mixing baffles. 
       FIGS. 5 and 6  illustrate a variant embodiment generally corresponding to  FIG. 4 . Also in  FIGS. 5 and 6  dashed lines indicate a heat exchange media that is not in use, and the arrows represent active air flow paths. In this embodiment the lower fill media ( 30  in  FIG. 4 ) is a coil circuit  56  which could incorporate an evaporative enhancing component  58 , as disclosed in U.S. Pat. No. 6,702,004. In this embodiment, the process fluid at its warmest entering temperature can first enter the coil  56  in the lower section of the tower, then exit the coil  56  at a cooler temperature to be discharged or returned to the process equipment. The fluid passing through the coil  56  has its cooling enhanced by a second circuit of falling evaporative heat exchange water, which is being pumped from the lower water collection basin up into a top water distribution system  24 . Thus, this system provides heat exchange to a primary fluid by virtue of the circulation of a secondary fluid through the tower. The secondary fluid flow is similar to that described for  FIGS. 1-4 . 
     Thus,  FIGS. 5 and 6  illustrate an embodiment schematically as in  FIG. 4 , but with the addition of the lower coil circuit  56 . Of course, an embodiment according to  FIG. 1  can also be implemented with a lower coil similar to that illustrated in  FIGS. 5 and 6  disposed with the lower fill media  30  of the embodiment of  FIG. 1 . In this way the above description for  FIGS. 1-6  includes four sub-groups of embodiments, the embodiment of  FIGS. 1-3  without the additional lower coil, the embodiment of  FIG. 4  without the additional lower coil, the embodiment of  FIG. 1  but also having an additional lower coil (not shown), and the embodiment of  FIGS. 5-6  having an additional lower coil. 
       FIG. 5  shows the top section in evaporative mode, and  FIG. 6  shows closed circuit mode for the top section. In both  FIGS. 5 and 6  the lower section is active to pass water over the coils being cooled. 
       FIG. 7  is a view similar to  FIG. 1  but showing yet another alternative embodiment. In this embodiment, each side has a lower closed coil  60  opposed next to the lower heat transfer media  30 . In the case where the lower heat transfer media  30  is an evaporative media, it will be appreciated that this entire lower cooling section in this embodiment operates similarly to the upper cooling section. That is, the valve  36  in this embodiment can be used to selectively direct fluid either into the intermediate collection basin  28  so that it (1) falls over the evaporative fill media  30  or (2) flows to the coil  60 . In this way, the valve  36  would operate similarly in function to the valve  20 . Valve  36  can be a continuous valve to direct a portion of the flow through one media and the rest through the other media. It will be appreciated that this embodiment can have a mode where it is run entirely as a “dry” cooling tower wherein valve  20  directs all of the fluid through the coil  32 , and valve  36  directs all of the fluid through the coil  60 . Fluid leaving the coil  60  is directed to the lower collection basin  31 . Various embodiments according to  FIG. 7  can be two-sided or one-sided, and use sheet media or coil media or the lower media  30 . 
     It is believed that the above description fully describes components and operation of the system in detail with reference to the drawings. However, the discussion below even further describes the modes of operations of some embodiments of the system. 
     Taking the embodiment of  FIG. 1  as an example, for near design heat load conditions, water passes from the control valve  20  to the top distribution basin  24  (bypassing the dry heat exchanger  32 ). The water then passes over the top evaporative fill  26  and into the re-distribution spray system  28  where it finally passes over the bottom evaporative heat exchanger  30 . 
     In this example, for less than design heat load conditions, the valve  20  is opened to maintain a pre-determined cold water set point. The more the valve  20  is opened, the more water passes through the dry heat exchanger  32 , and the warmer the water gets, less water is consumed by evaporation and less plume is generated as well. The more the valve  20  is closed, the more water passes over the evaporative heat exchanger  26 , the cooler the water gets and more water is consumed and more plume is generated as well. A control system for actuating the valve  20  can be used to maintain at or near an optimum balance condition, or this can also be done manually. The air in the upper section thus moves through both evaporative and closed heat exchanges in a series path, but the upper and lower sections are therefore arranged as in a parallel path system. The ability to switch between evaporative and dry heat transfer, and do it gradually provides advantageous operation in the “shoulder” seasons. 
     The water from the dry coil  32  combines with the water from the upper evaporative heat exchanger  26  at the re-distribution basin  28  before passing over the bottom evaporative heat exchanger  30 . 
     At far less than design heat load conditions, or at sufficiently cool conditions, the top evaporative heat exchanger  26  is completely bypassed so that no evaporation takes place. At this point all heat transfer in the top section is done through the dry heat exchanger  32 . The bottom evaporative heat exchanger  30  can continue to operate, enabling the system to operate as a true parallel path wet dry cross flow cooling tower, or can be bypassed (with or without the addition of dampers). 
     For extreme cold conditions or for additional water conservation, air inlet dampers  40  can be placed at the bottom heat exchanger  30  as shown in  FIG. 3 . If water is completely bypassing the top evaporative heat exchanger  26 , water temperature can be maintained at full fan speed by fully or partially closing the bottom heat exchanger dampers  40 . This reduces the air flow, which reduces the heat transfer and conserves water, and reduces plume as well, maintaining full fan speed allows for maximum heat transfer through the dry heat exchanger  34 . Once the dampers  40  are completely closed, the tower now operates in a completely dry mode. In this mode, very little water is consumed, and no plume is emitted. 
     Turning now to yet another variation which can be applied to any of the embodiments of the invention, although not specifically illustrated in any figure a variation is described in this paragraph. Each of the drawing figures illustrates the closed coil such as, for example, closed coil  32 , being disposed outwardly or outbound of the evaporative film media  26 . That is, in the embodiments that are illustrated in the configuration of the figures, the coil is closer to the air inlet, and closer to the outside of the tower, and the evaporative film media is inboard or closer to the center of the tower. However, the position of these elements can be reversed. That is, embodiments are possible where the coil is inbound of the evaporative film media. This can be advantageous in protecting the coils from environmental effects such as snow, ice, or wind-driven or falling debris such as tree branches or leaves. In some instances, the fill may be less expensive to replace than the coils. Further, if the fill is contacted by debris its effectiveness is generally affected only slightly, whereas if a coil is punctured, a leak can be very undesirable. Therefore, placing the fill towards the outboard as described in this paragraph may in some instances provide for a more weather and debris resistant configuration. The desirability of placing the coil inboard and the fill media outboard as described in this paragraph may also depend on whether external louvers are present on the outer side of the tower. 
     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.