Patent Document

RELATED APPLICATIONS 
     The application claims the benefit of U.S. provisional application 62/061,894, filed Oct. 9, 2014, the entirety of which is hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to an improved heat exchange apparatus such as a closed circuit fluid cooler, fluid heater, condenser, evaporator, thermal storage system, air cooler or air heater. More specifically, the present invention relates to a combination or combinations of separate indirect and direct evaporative heat exchange sections or components arranged to achieve improved capacity, improved performance and reduced scale formation on the surfaces of the indirect heat exchanger. 
     The invention includes the use of a coil type heat exchanger as an indirect heat exchange section. Such indirect heat exchange section can be combined with a direct heat exchange section, which usually is comprised of a fill section over which an evaporative liquid such as water is transferred, usually in a downwardly flowing operation. Such combined indirect and direct heat exchange sections together provide improved performance as an overall heat exchange apparatus such as a closed circuit fluid cooler, fluid heater, condenser, evaporator, air cooler or air heater. 
     Part of the improved performance of the indirect heat exchange section comprising a coil type heat exchanger is the capability of the indirect heat exchange section to provide both sensible and latent heat exchange with the evaporative liquid which is streamed or otherwise transported downwardly over and through the indirect heat exchange section. Such indirect heat exchangers are usually comprised of a series of serpentine tube runs with each tube run providing a circuit of a coil. Improved performance of such indirect heat exchangers is achieved by opening the spacing between the generally horizontal tube runs in one or more of the serpentine coil return bends. Such opened spacing in the serpentine coil return bends creates a more efficient cooling zone for the evaporative liquid flowing downwardly over the serpentine coils. 
     Various combinations of the heat exchange arrangements are possible in accordance with the present invention. Such arrangements could include an arrangement having an indirect heat exchange section with increased vertical spacing in the series of serpentine tube runs formed by increased height return bends. In such an arrangement, an evaporative liquid flows downwardly onto and through the indirect heat exchange section with such evaporative liquid, which is usually water, then exiting the indirect section to be collected in a cold water sump and then pumped upwardly to again be distributed downwardly over the indirect heat exchange section. In this counterflow arrangement, embodiments work more efficiently with generally lower spray flow rates, in the order of 2-4 GPM/sq. ft. In other arrangements presented, the design spray flow rates may be higher. 
     In another arrangement, a combined heat exchange apparatus is provided with an indirect heat exchange section comprised of serpentine tube runs over which and evaporative liquid is distributed downwardly onto and through the indirect heat exchange section. Such indirect heat exchange sections are comprised of serpentine tube runs having an increased spacing between one or more return bends of increased height. Further, a direct heat exchange section comprised of fill can be located in one or more of the areas of increased vertical spacing formed by the return bends of the serpentine coil. In this arrangement, the embodiments work more efficiently with generally lower spray flow rates, in the order of 2-4 GPM/sq. ft. The embodiments presented are more efficient providing increased heat rejection and also do it with less energy requirement for the spray water pump. In other arrangements presented, the design spray flow rates may be higher. 
     The heat exchanger apparatus, condenser or fluid cooler of the present invention could be operated wherein both air and an evaporative liquid such as water are drawn or supplied across both the indirect and direct heat exchange section if present. It may be desirable to operate the heat exchanger without a supply of the evaporative liquid, wherein air only would be drawn across the indirect heat exchange section and across a direct section if present. It is also possible to operate a combined heat exchanger in accordance with the present invention wherein only evaporative liquid would be supplied across or downwardly through the indirect heat exchange section and the direct heat exchange section if present, and wherein air would not be drawn by typical means such as a fan or the fan may be turned off. 
     In the operation of an indirect heat exchange section, a fluid stream passing through the internal side of the serpentine coils is cooled, heated, condensed, or evaporated in either or both a sensible heat exchange operation and a latent heat exchange operation by passing an evaporative liquid such as water together with air over the serpentine coils of the indirect heat exchange section. Such combined heat exchange results in a more efficient operation of the indirect heat exchange section, as does the presence of the increased spacing formed in one or more of the return bends of the serpentine tube runs of the indirect heat exchange section. The evaporative liquid is usually water and passes generally downwardly through the indirect heat exchange section and generally downwardly through the direct heat exchange section if present. The direct section, which is typically a fill assembly, is located in the increased vertical spacing in one or more of the increased height return bends of the serpentine coils of the indirect heat exchange section. Heat in the evaporative liquid is passed to air which is drawn generally passing upwardly or in some cases generally downwardly through the indirect heat exchange section and outwardly from the closed circuit fluid cooler or heat exchanger assembly by an air moving system such as a fan. The evaporative liquid draining from the indirect or direct heat exchange section is typically collected in a sump and then pumped upwardly for redistribution across the indirect or direct evaporative heat exchange section. 
     The type of fan system whether induced or forced draft, belt drive, gear drive or direct drive can be used with all embodiments presented. The type of fan whether axial, centrifugal or other can be used with all embodiments presented. All type of tubes, material of tubes, tube diameters, tube shapes, tube enhancements, tube fins, can be used with all the embodiments presented. Further, the number of tube passes, number of return bends, number of increased vertical spaces are limitations of the embodiments presented. Further, the coil may consist of tubes or may be a plate fin type or may be any type of plates in any material which can be used with all embodiments presented within. The type of fill, whether efficient counterflow fill, contaminated water application fills or any material fill can be used with all embodiments presented. 
     Extensive testing conducted has shown that in addition to the benefits of providing more cooling of the spray water in the large spray water cooling zones, the direct heat exchange surface located within the confines of the indirect heat exchange section, evaporates a considerable amount of water compared to that in the indirect section and accordingly prevents at least partially the scale from building on surfaces of indirect coil. 
     Accordingly, it is an object of the present invention to provide an improved heat exchange apparatus, which could be a closed circuit fluid cooler, fluid heater, condenser, evaporator, air cooler or air heater, which includes an indirect heat exchange section with increased spacing formed in one or more return bends of the serpentine tube forming the indirect heat exchange section. 
     It is another object of the present invention to provide an improved heat exchange apparatus such as a closed circuit fluid cooler, fluid heater, condenser, evaporator, air cooler or air heater, including an indirect heat exchange section that comprises a series of serpentine tube runs with increased vertical spacing between one or more of the tube runs and with a direct heat exchange section located in one or more of the areas of increased vertical spacing. 
     It is another object of the present invention to provide an improved evaporative heat exchange apparatus such as a closed circuit fluid cooler, fluid heater, condenser, evaporator, air cooler or air heater, including at least two indirect heat exchange sections that comprise a series of serpentine tube runs with increased vertical spacing between one or more tube runs and with a direct heat exchange located in one or more of the areas of increased vertical spacing between tube runs. 
     It is another object of the present invention to provide an improved evaporative heat exchange apparatus such as a closed circuit fluid cooler, fluid heater, condenser, evaporator, air cooler or air heater, including at least two indirect heat exchange sections separated by an increased vertical spacing with an optional direct heat exchange located in the increased vertical space between indirect heat exchange sections. 
     It is another object of the present invention to provide an improved evaporative heat exchange apparatus such as a closed circuit fluid cooler, fluid heater, condenser, evaporator, air cooler or air heater, including at least two indirect heat exchange sections separated by an increased vertical spacing where the indirect heat exchangers are connected with vertical tube runs in lieu of external piping such that a direct heat exchange may be located in the increased vertical space between indirect heat exchange sections. 
     It is another object of the present invention to provide an improved evaporative heat exchange apparatus such as a closed circuit fluid cooler, fluid heater, condenser, evaporator, air cooler or air heater, where direct heat exchange sections located in one or more of the areas of increased vertical spacing between tube runs or alternatively located between increased vertical space between indirect heat exchange sections are easily accessible and replaceable for serviceability. 
     It is another object of the present invention to provide an improved evaporative heat exchange apparatus such as a closed circuit fluid cooler, fluid heater, condenser, evaporator, air cooler or air heater, where direct heat exchange sections located in one or more of the areas of increased vertical spacing between tube runs or alternatively located between increased vertical space between indirect heat exchange sections evaporates a considerable amount of water compared to that in the indirect section and accordingly prevents at least partially the scale from building on surfaces of indirect coil. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved heat exchange apparatus which typically is comprised of an indirect heat exchange section. The indirect heat exchange section provides improved performance by utilizing a serpentine coil arrangement comprised of tube run sections and return bends, with a means of increasing the distance between one or more of the tube runs of the serpentine coils. One way to accomplish this vertical separation between the generally horizontal or sloped tube runs is by increasing one or more of the return bend radius in the return bends of the serpentine tube runs in the serpentine coil or by using two 90 degree bends separated by a vertical tube run. Another way to accomplish this vertical separation between generally horizontal or sloped tube runs is to install a purposeful vertical spacing between two or more serpentine coils or other indirect heat exchange sections such as plate heat exchangers. Another way to accomplish this vertical separation between generally horizontal or sloped tube runs is to have at least one short return bend which is less than 180 degrees allowing the tubes to be sloped such that a marked higher distance between the indirect tubes is accomplished which allows a generally triangular shaped direct heat exchange section. 
     The tube run sections of the serpentine coil arrangement may be generally horizontal and can be slanted downwardly from the inlet end of the coils toward the outlet end of the coils to improve flow of the fluid stream there through. Such serpentine coils are designed to allow a fluid stream to be passed there through, exposing the fluid stream indirectly to air or an evaporative liquid such as water, or a combination of air and an evaporative liquid, to provide both sensible and latent heat exchange from the outside surfaces of the serpentine coils of the indirect heat exchanger. Such utilization of an indirect heat exchanger in the closed circuit fluid cooler, fluid heater, condenser, evaporator, air cooler or air heater of the present invention provides improved performance and also allows for combined operation or alternative operation wherein only air or only an evaporative liquid or a combination of the two can be passed through or across the outside of the serpentine coils of the indirect heat exchanger. 
     A direct heat exchange section or sections can be located generally within the indirect heat exchange section in the vertical spacing between the increased height return bends of the generally horizontal tube runs of the serpentine coil. Accordingly, the evaporative liquid is allowed to pass across and through the indirect and direct sections comprising the heat exchange section. Heat is drawn from such evaporative liquid by a passage of air across or through the indirect and direct heat exchange sections by air moving apparatus such as a fan. Such evaporative liquid is collected in a sump in the bottom of closed circuit fluid cooler, fluid heater, condenser, evaporator, air cooler or air heater and pumped back for distribution, usually downwardly, across or through the indirect heat exchange section. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, 
         FIG. 1  is a side view of a prior art indirect heat exchanger including a series of serpentine tube runs; 
         FIG. 2  is a side view of a prior art indirect heat exchanger serpentine coil; 
         FIG. 3  is a side view of a first embodiment of an indirect heat exchanger with a series of serpentine tube runs with direct heat exchange sections in accordance with the present invention 
         FIG. 4  is a side view of a second embodiment of an indirect heat exchanger with a series of serpentine tube runs with direct heat exchange sections in accordance with the present invention 
         FIG. 5  is a side view of a third embodiment of an indirect heat exchanger with a series of serpentine tube runs with direct heat exchange sections in accordance with the present invention 
         FIG. 6  includes  FIGS. 6 a    and  6   b.    
         FIG. 6 a    is a side view of an embodiment where the direct section rests on top of the indirect section 
         FIG. 6 b    is a side view of an embodiment where the direct section is supported such that it does not touch the indirect section. 
         FIG. 7  includes  FIGS. 7 a , 7 b    and  7   c.    
         FIG. 7 a    is a side view of an embodiment having a generally rectangular direct section 
         FIG. 7 b    is a side view of an embodiment having a generally triangular direct section 
         FIG. 7 c    is a side view of an embodiment having a generally rectangular direct section 
         FIG. 8  is a perspective view of the fourth embodiment of a closed circuit cooling tower with an indirect heat exchange section with direct heat exchange sections in accordance with the present invention; 
         FIG. 9  is a chart of performance of heat exchangers constructed in accordance with the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIG. 1 , a prior art evaporatively cooled coil product  10  which could be a closed circuit cooling tower or an evaporative condenser. Both of these products are well known and can operate wet in the evaporative mode or can operate dry, with the spray pump  12  turned off when ambient conditions or lower loads permit. Pump  12  receives the coldest cooled evaporatively sprayed fluid, usually water, from cold water sump  11  and pumps it to spray water header  19  where the water comes out of nozzles or orifices  17  to distribute water over indirect coil  14 . Spray water header  19  and nozzles  17  serve to evenly distribute the water over the top of the coil(s)  14 . As the coldest water is distributed over the top of coil  14 , motor  21  spins fan  22  which induces or pulls ambient air in through inlet louvers  13 , up through coil  14 , then through drift eliminators  20  which serve to prevent drift from leaving the unit, and then the warmed air is blown to the environment. The air is generally flowing in a counterflow direction to the falling spray water. Although  FIG. 1  and all following Figures are shown with axial fan  22  inducing or pulling air through the unit, the actual fan system may be any style fan system that moves air through the unit including but not limited to induced and forced draft. Additionally, motor  21  may be belt drive as shown, gear drive or directly connected to the fan. It should be understood that in all the embodiments presented, there are many circuits in parallel with tube runs but only the outside circuit is shown for clarity. Indirect coil  14  is shown with an inlet header  15  and outlet header  16  which connects to all the serpentine tubes having normal height return bend sections  18 . It should be further understood that the number of circuits or number of return bends within a serpentine coil is not a limitation to embodiments presented. 
     Referring now to  FIG. 2 , prior art coil  30  has inlet and outlet headers  37  and  31  respectively, is supported by coil clips  32  and  38  with center support  41 . There are two circuits coming out of the inlet header shown as generally horizontal tube runs  39  and  40 . Coil  30  is built with short radius or normal return bends  36  with a small slope to allow for proper drainage. In some prior art coils, this slope of the generally horizontal tube runs can vary with the last set of tube runs on the bottom having more slope. The spacing  35  between tube runs on the left side can be seen as nearly zero and accordingly allows very little interaction between the falling spray water and generally counter flowing air before the spray water hits the next set of tube runs. Similarly, the space  33  and  34  between generally horizontal tube runs is seen as a little larger but still there is insufficient interaction between the falling spray water and generally counter flowing air before the spray water hits the next set of tube runs compared to the embodiments presented within. In addition, there is not enough room in gaps  33 ,  34  or  35  to install a direct heat exchange section such as counterflow fill to further increase the spray water cooling such as the embodiments presented within. 
     Referring now to  FIG. 3 , a cooling tower in accordance with a first embodiment is shown at  610 . In this embodiment, air enters through air inlet louvers  613 , passes generally upwards through the indirect and heat exchanger  616  and also passes through optional direct heat exchanger  615  then passes through drift eliminators  622  then through fan  624  driven by fan motor  623 . At the same time, when wet evaporative operation is desired, water is pumped from cold water sump  611  by pump  612  to spray header  621  and out of nozzles  620  to spray onto the top of the indirect heat exchange surface  616 . Operation of the spray pump may be omitted during dry operation. Optionally, spray pump  612  may operate without fan motor  623  operating when desired, or with fan motor  623  operating between 0 to 100% speed, as known in the art. Indirect section inlet header connection  619  and outlet header connection  625  are piped to the indirect section process fluid accordingly. 
     In this embodiment of  FIG. 3 , all of the indirect heat exchanger tubes in coil  616  are separated by a large vertical distance such that  627 , the distance between the tubes and room for the direct surface  615 , is at least 2″ in height. Note that the large distance between tubes of indirect surface  627  of at least 2″ forms a large spray water cooling zone  614  in coil  616 . In this embodiment, direct section  615  may be omitted or may contain one or greater number of direct heat exchange sections  615 . Further, direct sections  615  may be removed for cleaning or replacement as required. Direct heat exchange section  615  can be counterflow fill which is installed inside the large spray water cooling zone  614 . Direct section  615  increases the efficiency of the cooling of the spray water within the large spray water cooling section  614 . In this embodiment, there are repeating sets of indirect tube runs or passes with large radius bends  626 . Alternatively, the vertical separation between tube runs may be formed with two 90 degree bends  618  separated by vertical run  617 . The large separation between tube runs  627  form three large spray water cooling zones  614  to exist within the confines of the coil. In this case, up to three direct sections  615  can be used if desired as shown. The efficiency gained in further cooling the spray water between the tubes in cooling zones  614  far exceeds the loss of airflow from the added direct sections or fill decks  615  to apparatus  610 . The type of direct section can be counterflow fill, contaminated water fill or any substrate that increases the surface area of the spray water within the large spray water cooling zone  614 . It should be noted that the tube runs in coil  616  are shown as horizontal for clarity but can be sloped or slanted as known in the art. It should be noted that the number of tube runs between large spray water cooling zones, the number of large spray water cooling zones, number of total tube runs, the height of large spray water cooling zone can all be varied to optimize performance and unit height. 
     Referring now to  FIG. 4 , a cooling tower in accordance with a second embodiment is shown at  710 . In this embodiment, air enters through air inlet louvers  713 , passes generally upwards through the indirect and heat exchanger  714  and also optional direct heat exchanger  715  then passes through drift eliminators  722  then through fan  724  driven by fan motor  723 . At the same time, when desired, water is pumped from sump cold water  711  by pump  712  to spray header  721  and out of nozzles  720  to spray onto the top of the indirect heat exchange surface  714 . Operation of the spray pump may be omitted during “dry operation”. Optionally, spray pump  712  may operate without fan motor  723  operating, or with fan motor  723  operating between 0 to 100% speed, when desired as known in the art. Indirect section inlet header connection  719  and outlet header connection  725  are piped to the indirect section process fluid accordingly. 
     In the embodiment of  FIG. 4 , all of the top and bottom indirect heat exchanger tubes have multiple short return radius bends  718  followed by at least one extraordinarily long radius return bend  729  which allows  727 , the distance between the tubes and room for the direct surface  715 , to be at least 2″ in height. Alternatively, the large separation between tube runs may be formed with two 90 degree bends  716  separated by vertical run  717 . Note that the large distance between tubes of indirect surface  727  forms a large spray water cooling zone  728  in coil  714 . In this embodiment, direct section  715  may be omitted or may contain one or greater number of direct heat exchange sections  715 . Further, direct sections  715  may be removed for cleaning or replacement as required. Direct heat exchange section  715  can be counterflow fill which is installed inside the large spray water cooling zone  728 . Direct section  715  increases the efficiency of the cooling of the spray water within the large spray water cooling section  728 . The efficiency gained in further cooling the spray water between the tubes  727  far exceeds the loss of airflow from the added direct sections or fill decks  715  to apparatus  710 . The type of direct section can be counterflow fill, contaminated water fill or any substrate that increases the surface area of the spray water within the large spray water cooling zone. It should be noted that the tube runs in coil  714  are shown as horizontal for clarity but can be sloped or slanted as known in the art. It should be noted that the number of tube runs between large spray water cooling zones  728 , the number of large spray water cooling zones, number of total tube runs, number of circuit feeds, the height of large spray water cooling zone can all be varied to optimize performance and unit height. The embodiment in  FIG. 4  allows for a central location for the direct section or sections for ease of manufacturing and for ease of serviceability. The embodiment also uses the vertical tube runs  717  to connect the top short radius bend indirect heat exchanger to the bottom short radius return bend indirect heat exchange. 
     Referring now to  FIG. 5 , a cooling tower in accordance with a third embodiment is shown at  810 . In this embodiment, air enters through air inlet louvers  813 , passes generally upwards through the indirect heat exchanger  818  and also optional direct heat exchanger  815  then passes through drift eliminators  822  then through fan  824  driven by fan motor  823 . At the same time, when desired, water is pumped from cold water sump  811  by pump  812  to spray header  821  and out of nozzles  820  to spray onto the top of the indirect heat exchange surface  830 . Operation of the spray pump may be omitted during “dry operation”. Optionally, spray pump  812  may operate without fan motor  823  operating, or with fan motor  823  operating between 0 to 100% speed, when desired as known in the art. Indirect section inlet header connection  819  and outlet header connection  825  are piped to the indirect section process fluid accordingly. 
     In the embodiment of  FIG. 5 , the indirect heat exchanger tubes have a combination of at least two consecutive short return bends  830  with at least two consecutive long return bends which allows  827 , the distance between the tubes and room for the direct surface  815 , to be at least 2″ in height. Alternatively, the large separation between tube runs may be formed with two 90 degree bends  816  separated by vertical tube run  831 . Note that the large distance between tubes of indirect surface  827  forms a large spray water cooling zone  814  in coil  818 . In this embodiment, direct section  815  may be omitted or may contain one or greater number of direct heat exchange sections  815 . Further, direct sections  815  may be removed for cleaning or replacement as required. Direct heat exchange section  815  can be counterflow fill which is installed inside the large spray water cooling zone  814 . Direct section  815  increases the efficiency of the cooling of the spray water within the large spray water cooling section  814 . The efficiency gained in further cooling the spray water in direct section  815  far exceeds the loss of airflow from the added direct sections or fill decks  815  to apparatus  810 . The type of direct section can be counterflow fill, contaminated water fill or any substrate that increases the surface area of the spray water within the large spray water cooling zone. It should be noted that the tube runs in coil  818  are shown as horizontal for clarity but can be sloped or slanted as known in the art. It should be noted that the number of tube runs between large spray water cooling zones  827 , the number of large spray water cooling zones, number of total tube runs, the height of large spray water cooling zone can all be varied to optimize performance and unit height. 
     Referring now to  FIG. 6 , the method of mounting the direct heat exchange section within the indirect tube runs of the three embodiments presented is discussed. In  FIG. 6 a   , direct section  93  rests on and is supported by indirect surface  90  such that there is no space between 90 and 93 while space  97  is sufficient to allow direct heat exchange surface  93  to be installed and removed for service or replacement. It should be noted that height  91  between indirect tubes  90  and  92  is at least 2″ inches in height for all embodiments. In  FIG. 6 b   , direct section  93  rests on and is supported by support means  94  and does not directly touch indirect surface  90  or  92  forming spacing  95  and  96  such that direct surface  93  can be installed and removed for service or replacement. It should be noted that height  91  between support means  94  and indirect tube  92  is at least 2″ inches in height for all embodiments. 
     Referring now to  FIG. 7 , the height and shape of the direct heat exchange surface is discussed relative to the indirect heat exchange design. In  FIG. 7 a   , heat exchange section  110  with indirect inlet and outlet pipes  114  and  115 , consists of multiple indirect serpentine tubes with at least one short radius return bend  111  and at least one longer return bend  112  such that  113 , the distance between the indirect tubes on the longer return bends is at least 2″ in height. This allows generally rectangular shaped direct heat exchange section  117  to be at least 2″ in height. In  FIG. 7 b   , heat exchange section  120  with indirect inlet and outlet pipes  124  and  125 , consists of multiple indirect serpentine tubes  126  with at least one short return bend  121  which is less than 180 degrees allowing the tubes to be sloped such that  123 , the highest distance between the indirect tubes is at least 2″ in height. This allows generally triangular shaped direct heat exchange section  127  to be at least 2″ in height at the base. In  FIG. 7 c   , heat exchange section  160  with indirect inlet and outlet pipes  164  and  165 , consists of multiple indirect heat exchange plates  161  such that  163 , the distance between indirect plates  161  and  166  is at least 2″ in height. This allows generally rectangular shaped direct heat exchange section  167  to be at least 2″ in height. 
     It should be noted that the desired minimum height of each direct heat exchange section in all the embodiments is at least 2″ (5.08 cm) in height, usually not more than 60 inches ((152.4 cm) in height with the preferred height being 12 inches (30.48 cm). 
       FIG. 8  is a perspective view of a cooling tower  280  in accordance with all the embodiments. More specifically, the cutaway views show that direct sections  285  may be easily removed for cleaning and replacement by opening or removing panels  284 . Removal of panels allows access to clean indirect heat exchanger  283  as well. In embodiment  280 , indirect coil  283  is shown with panels  284  removed for clarity where the large spray water cooling zones is located. A means for supporting the direct sections within the large spray water cooling zones in indirect coil  283  can be the direct section  285  resting on the indirect section, or sitting on small rods or other support means that are installed on top of indirect section  283  or any means to hang the direct section without it touching the indirect section if desired. The means to install the direct section within the large spray cooling zone is not a limitation. Spray water inlet  287  serves to distribute the spray water uniformly to the top of coil  283 . Air inlet  282  is shown without the inlet louvers installed so the inside of cold water basin  281  can be seen. Coil inlet and outlet  289  are shown for connection for the incoming fluid to be cooled or condensed. Fan shaft  288 , is connected to the fan and motor (not shown) and the fan system pulls air though the air inlet  282  through indirect coil  283  and direct sections  285  through the drift eliminators (not shown) and then generally upwards to the environment. 
       FIG. 9  is a chart showing data from the prior art unit shown in  FIG. 1  and the improved heat exchanger in the fourth embodiment employing indirect and direct sections. Specifically, the process fluid is represented in both prior art and the fourth embodiment by the top solid line (curve PF TempTest) showing the closed circuit cooling tower cooled the internal indirect coil fluid, in this case water, from 100 F to 88 F. It should be noted that in the prior art coil test, the top dotted line shows the spray water temperature at the top and bottom of the coil to be approximately 86 F while the maximum spray water temperature reached is approximately 91 F. However, note that with forth embodiment test data of the spray water temperature represented by the squiggly solid line, the spray water temperature at the top and bottom of the indirect coil section was 84 F and the maximum spray water temperature was 93 F. The improvement of the large spray water cooling zones can be seen as the spray water temperatures are both cooler displaying the ability to absorb more heat from the indirect tube runs yet overall the spray temperature was cooler as noted by the squiggly lines. The bottom two lines are the entering and leaving wet bulb temperatures. The bottom dotted line is from the prior art coil test showing the wet bulb entered at 78 F and left the unit at 89 F. The bottom solid line shows the wet bulb entering and leaving temperatures from test data from the fourth embodiment. Note that again the wet bulb entering temperature was 78 F yet the leaving wet bulb is higher than the prior art data leaving at 94 F. This increase in leaving wet bulb temperature shows the increased performance at identical operating test unit power draw (motors from both tests were both at 30 HP). In the fourth embodiment test data, because the spray water temperature profile is pushed up and the air wet bulb line (WB Coil&amp;Fill) is also pushed up, this allows air to have a larger enthalpy increase. So by adding direct sections to a prior art indirect coil only product, the efficiency gain from having large spray water cooling zones between the tube runs can be seen to be much more beneficial than a slight loss in airflow caused by adding the direct sections. With fill decks sandwiched between coil tubes, the efficiency of heat rejection is increased as the spray water picks up more sensible heat and transfers it to air in both latent and sensible fashions.

Technology Category: f