Abstract:
A heat exchange apparatus is provided with an indirect evaporative heat exchange section and a direct evaporative heat exchange section. The indirect evaporative heat exchange section is usually located above the direct evaporative heat exchange section, and an evaporative liquid is passed downwardly onto the indirect heat exchange section. The evaporative liquid that exits the indirect evaporative heat exchange section then passes downwardly across and through the direct heat exchange section. The evaporative liquid is collected in a sump and then pumped upwardly to be distributed again across the indirect heat exchange section. The indirect heat exchange section is comprised of a plate type heat exchanger. 
     An improved heat exchange apparatus is provided with indirect evaporative heat exchange section consisting of a plate type heat exchanger which provides more surface area per volume compared to other designs. The indirect plate style heat exchanger may be combined with one or more direct evaporative heat exchange sections in multiple arrangements.

Description:
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 and performance. 
     The invention includes the use of a plate type heat exchanger as an indirect heat exchange section. When compared with coil circuit indirect heat exchangers which are comprised of individual circuits of tubing, the performance of an indirect heat exchange section comprised of a plate type heat exchanger is improved. 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 streaming operation. Such combined indirect heat exchange section and direct heat exchange section 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 plate heat exchanger is the capability of the indirect heat exchange section as a plate type heat exchanger to provide both sensible and latent heat exchange with the evaporative liquid which is streamed or otherwise transported over and through the indirect heat exchange section. Another important improvement is that plate heat exchangers will have more surface area in the same physical space as other evaporative indirect heat exchangers. Such as indirect heat exchangers comprised, of serpentine coils. 
     Various combinations of the heat exchange arrangements are possible in accordance with the present invention. Such arrangements could include an arrangement wherein the indirect heat exchange section operates alone, is physically located above the direct heat exchange section or is physically located below the direct heat exchange section. In such an arrangement with indirect section located above the direct section, an evaporative liquid is streamed or otherwise sprayed downwardly onto the indirect heat exchange section with such evaporative liquid, which is usually water, then exiting the indirect section to be transported over the direct heat exchange section which is usually comprised of a fill arrangement. In another arrangement of a combined heat exchange apparatus the indirect heat exchange section is physically located below the direct heat exchange section. In another arrangement of a combined heat exchange apparatus two or more indirect sections are placed in a single closed circuit fluid cooler or heat exchanger each above or below a direct heat exchange section is also part of the present invention. Further, it should be understood that due to varying heat loads and needs of heat exchange, the heat exchanger apparatus 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 sections. 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. 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, and wherein air would not be drawn by typical means such as a fan. 
     In the operation of an indirect heat exchange section, a fluid stream passing through the internal openings in the plate type heat exchanger 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 in passages between individual plate pairs or cassettes in the indirect heat exchanger. Such combined heat exchange results in a more efficient operation of the indirect heat exchange section. The evaporative liquid, which again is usually water, which passes across or downwardly through the indirect heat exchange section then passes, usually downwardly, across or through the direct heat exchange section which is typically a fill assembly. Heat in the evaporative liquid is passed to air which is drawn generally downwardly, upwardly or across the direct 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. Of course, as explained above, the indirect and direct heat exchange sections can be reversed wherein, in the reversed situation where a direct heat exchange section would be located above an indirect heat exchange section, the evaporative fluid exiting the indirect section would be collected in a sump and pumped upwardly for distribution across the direct heat exchange section. Alternatively, only the indirect heat exchange section may be present. 
     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 and possibly a direct 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 plate type heat exchanger. 
     It is another object of the invention to provide an improved heat exchange apparatus comprising a plate type heat exchanger with more surface area per volume than other evaporative indirect heat exchangers. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved heat exchange apparatus which typically is comprised of a combination of an indirect heat exchange section and a direct heat exchange section. The indirect heat exchange section provides improved performance by utilizing a plate type heat exchanger as the indirect heat exchange section. The plate type heat exchanger contains more surface area per unit volume that other indirect evaporative heat exchangers. The plate type heat exchanger is comprised of one or more combined plate heat exchange groupings or cassettes each comprised of a pair of plates. Each cassette forms an internal passage between plates. Such plates are designed to allow a fluid stream to be passed there through within the cassette, exposing the fluid stream to a large surface area of one side of each plate in the cassette of the heat exchanger. Outside each plate a space is provided wherein air or an evaporative liquid such as water, or a combination of air and an evaporative liquid, can be passed to provide both sensible and latent heat exchange from the outside surfaces of the plates of the plate heat exchanger. Such utilization of a plate 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 plates in the plate heat exchanger. 
     A direct heat exchange section is located generally beneath the indirect heat exchange section whereby the evaporative liquid falling from the indirect heat exchange section is allowed to pass across or through fill and accordingly allow heat to be drawn from such evaporative liquid by a passage of air across or through the direct heat exchange section 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. 
     It is also part of the present invention to provide an assembly wherein two or more indirect heat exchange sections are located above two or more direct heat exchange sections in a single cooling tower or heat exchanger unit. It is also part of the present invention to reverse the positioning of the indirect and direct heat exchange sections wherein the direct heat exchange section would be located above the indirect section. Accordingly an evaporative liquid would be passed initially downwardly through the direct heat exchange fill section, with the evaporative liquid falling from the direct heat exchange section to the indirect heat exchange section. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, 
         FIG. 1  is a side view of a first embodiment of a heat exchanger in accordance with the present invention; 
         FIG. 1A  is a side view of another embodiment of a heat exchanger in accordance with the present invention; 
         FIG. 2  is a side view of a second embodiment of a heat exchanger in accordance with the present invention; 
         FIG. 3  is a side view of a third embodiment of a heat exchanger in accordance with the present invention; 
         FIG. 4  is side view of a fourth embodiment of a heat exchanger in accordance with the present invention; 
         FIG. 5  is a side view of a fifth embodiment of a heat exchanger in accordance with the present invention; 
         FIG. 6  is a side view of a sixth embodiment of a heat exchanger in accordance with the present invention; 
         FIG. 7  is a side view of a seventh embodiment of a heat exchanger in accordance with the present invention; 
         FIG. 8  is a side view of an eighth embodiment of a heat exchanger in accordance with the present invention; 
         FIG. 9  is a side view of a ninth embodiment of a heat exchanger in accordance with the present invention; 
         FIG. 10  is a side view of a tenth embodiment of a heat exchanger in accordance with the present invention; 
         FIG. 11  is a perspective view of a plate heat exchanger in accordance with an embodiment of the present invention; 
         FIG. 12  is a partial view of a plate heat exchanger in accordance with an embodiment of the present invention; 
         FIG. 13  is a side view of a plate heat exchanger with plates separated in accordance with the present invention; 
         FIG. 14  is a side view of a plate heat exchanger showing places separated in accordance with the present invention; 
         FIG. 15  is a top view of a plate heat exchanger in accordance with the present invention; 
         FIG. 16  is a perspective view of an assembled plate heat exchanger in accordance with the present invention; 
         FIG. 17  is an end view of a plate heat exchanger in accordance with the present invention, and 
         FIG. 18  is a side view of a plate heat exchanger in accordance with the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIG. 1  of the drawings, a heat exchanger in accordance with a first embodiment of the present invention is shown generally at  10 . Such heat exchangers generally are present in a closed circuit cooling tower with a direct heat exchange section  4  and an indirect heat exchange section  5  located above direct heat exchange section  4 . Direct heat exchange section  4  is typically comprised of fill usually comprised of sheets of polyvinyl chloride. Direct heat exchange section  4  receives air through air inlet  8  on the outside of heat exchanger  10 , with air being drawn generally across and somewhat upwardly through direct heat exchange section  4  by fan  6 . Indirect heat exchange section  5  is usually comprised of plate type heat exchanger  5 A having a fluid outlet  2  and a fluid inlet  1 . It should be understood that the operation of fluid outlet  2  and fluid inlet  1  can be reversed if it is desired. The preferred air direction through the indirect heat exchange section  5  is to enter from the top of the water distribution assembly  3 . Air is then drawn generally downwardly from the top through the indirect heat exchanger section  5  and exits from the bottom of section  5  by fan  6 . In addition, air can also be optionally drawn through air inlet  7  and generally downwardly across and upwardly through indirect heat exchange section  5  by fan  6  with the top of the water distribution assembly  7 ′ open or closed. An evaporative liquid, usually water, flows downwardly from water distribution assembly  3  such that the evaporative liquid falls downwardly and through indirect heat exchange section  5 . The evaporative liquid that passes through indirect heat exchange section  5  passes downwardly and through direct heat exchange section  4 . The evaporative liquid that passes downwardly and out from direct heat exchange section  4  is collected in sump  9 A and is pumped upwardly by pump  9  for redistribution through water distribution assembly  3 . Water distribution assembly  3  can be comprised of a variety of pipes with openings, or any other water distribution arrangement such as using spray nozzles, troughs, or other water distribution assemblies. Indirect heat exchange section  5  is usually comprised of a plate type heat exchanger  5 A. A fluid to be cooled, condensed, heated, or evaporated, passes within the joined plates or cassettes of plate heat exchanger  5 A. 
     Referring now to  FIG. 1A  of the drawings, a heat exchanger in accordance with another embodiment of the present invention is shown generally at  170 . Such heat exchangers generally are present in a closed circuit cooling tower with a direct heat exchange section  174  and two indirect heat exchange sections  184  and  185  located above direct heat exchange section  174 . Direct heat exchange section  174  is typically comprised of fill usually comprised of sheets of polyvinyl chloride. Direct heat exchange section  174  receives air through air inlet  178  on the outside of heat exchanger  170 , with air being drawn generally across and somewhat upwardly through direct heat exchange section  174  by fan  175 . The first indirect heat exchange section  184  is usually comprised of plate type heat exchanger  184 A having a fluid outlet  172  and a fluid inlet  171 . The second indirect heat exchange section  185  is usually comprised of plate type heat exchanger  185 A having a fluid outlet  182  and a fluid inlet  181 . It should be understood that the operation of fluid outlets  172  and  182  and fluid inlets  171  and  181  can be reversed if it is desired. The preferred air direction through the indirect heat exchange sections  184  and  185  is to enter from the top of the water distribution assembly  173 . Air is then drawn generally downwardly from the top through the indirect heat exchanger sections  184  and  185  and exits from the bottom of section  184  and  185  by fan  175 . In addition, air can also be optionally drawn through air inlet  177  and generally downwardly across and upwardly through indirect heat exchange section  184  and  185  by fan  175  with the top of the water distribution assembly  177 A open or closed. An evaporative liquid, usually water, flows downwardly from water distribution assembly  173  such that the evaporative liquid falls downwardly and through indirect heat exchange sections  184  and  185 . The evaporative liquid that passes through indirect heat exchange sections  184  and  185  passes downwardly and through direct heat exchange section  174 . The evaporative liquid that passes downwardly and out from direct heat exchange section  174  is collected in sump  179 A and is pumped upwardly by pump  179  for redistribution through water distribution assembly  173 . Water distribution assembly  173  can be comprised of a variety of pipes with openings, or any other water distribution arrangement such as using spray nozzles, troughs, or other water distribution assemblies. Indirect heat exchange sections  184  and  185  are usually comprised of a plate type heat exchanger  184  and  185 A, respectively. Two fluids to be cooled, condensed, heated, or evaporated, pass independently within the joined plates or cassettes of plate heat exchanger  184  and  185 A as separate fluid streams. 
       FIG. 2  is a side view of the second embodiment of heat exchanger  20  in accordance with a second embodiment of the present invention. Heat exchanger  20  is usually a closed circuit cooling tower including an indirect heat exchange section  15  located above a direct heat exchange section  14 , with the understanding that two such indirect and direct sections are provided as part of heat exchanger  20 . Direct heat exchange section  14  is again comprised of fill sheets of a suitable material such as polyvinyl chloride. Air to be passed across and generally crossways through direct heat exchange section  14  enters through air inlet  18  and is drawn by fan  16 . Indirect heat exchange section  15  is usually comprised of a plate heat exchanger  15 A. The preferred air direction through the indirect heat exchange section  15  is to enter from the top of the evaporative liquid distribution arrangement  13 A. Air is then drawn generally downwardly from the top through the indirect heat exchanger section  15  and exits from the bottom of section  15  by fan  16 . In addition, air can also be optionally drawn downwardly, across and generally upwardly through indirect heat exchange section  15  entering through air inlet  17  by fan  16  with the top of the liquid distribution arrangement ent  17 ′ open or closed. Evaporative liquid is provided to flow downwardly from an evaporative liquid distribution arrangement  13 A. Such evaporative liquid passes generally downwardly across indirect heat exchange section  15 . The evaporative liquid that exits indirect heat exchange section  15  passes downwardly through direct heat exchange section  14  and is collected in sump  19 A. Such collected evaporative liquid is pumped by pump  19  upwardly for distribution to water evaporative liquid distribution assembly  13 A. Plate heat exchanger  15 A includes fluid outlet  12  and fluid inlet  13 , which can be reversed if it is desired. A fluid to be cooled, condensed, heated or evaporated passes within the joined plates or cassettes of plate heat exchanger  15 A. 
     It should be understood in the operation of heat exchanger  10  and heat exchanger  20  described above, that depending on the performance required, both such heat exchangers may be operated with both evaporative liquid exiting the evaporative liquid distribution system and the fan drawing air across and through the direct and indirect heat exchange sections. If a lesser degree of heat exchange is required, it is possible to operate without the fan drawing air across the indirect and direct sections, such that only the evaporative liquid would exit and pass downwardly and through the indirect and direct heat exchange sections. Finally, the unit may be operated such that the evaporative liquid would not be supplied through the evaporative liquid distribution assembly, and the heat exchanger would operate only with the fluid passing within the indirect heat exchange section joined plate pairs being cooled by air passing downwardly or across and upwardly drawn by the fan in the heat exchanger or cooling tower. 
     Referring now to  FIG. 3  of the drawings, the third embodiment of a heat exchanger is shown generally at  30 , in the form of a closed circuit cooling tower. Heat exchanger  30  is comprised of a direct heat exchange section  34  which is located generally above an indirect heat exchange section  35 . Direct heat exchange section  34  is usually comprised of a fill sheet assembly wherein the fill sheets are typically comprised of polyvinyl chloride. Air enters through air inlet  38  and is drawn by fan  36  across and upwardly through direct heat exchange section  34 . An evaporative liquid usually water is distributed downwardly from evaporative liquid distribution assembly  33 ; such evaporative liquid passes downwardly and through direct heat exchange section  34 . The top  33 A of the evaporative liquid distribution assembly  33 , is usually closed. Indirect heat exchange section  35  is usually comprised of a plate heat exchanger  35 A which is comprised of a series of joined plate cassettes with separated spaces between each cassette. Fluid to be cooled, heated, condensed or evaporated enters through fluid inlet  31  and exits through fluid outlet  32 , although such can be reversed if it is desired. Air passes through the indirect heat exchange section  35  and between plate pairs or cassettes of the plate heat exchanger entering through air inlet  37  and drawn by fan  36 . Note that air inlet  38  can be partially open to change the air flow ratio between the indirect and the direct heat exchange sections or can be fully closed which allows the full amount of air entering the direct heat exchange section. Evaporative liquid falling from direct heat exchange section  34  passes between the plate pairs or cassettes of plate heat exchanger  35  and provides both sensible and latent heat transfer of the fluid passing within the joined plates in plate heat exchanger  35 A. Such evaporative liquid is collected in sump  39 A and is pumped upwardly through using pump  39  for redistribution through evaporative distribution assembly  33 . 
     Referring now to  FIG. 4 , a fourth embodiment of a heat exchanger assembly is shown generally at  40  in accordance with the present invention. In this embodiment two direct heat exchanger sections  44  are located above two indirect heat exchanger sections  45 . Evaporative liquid exits evaporative liquid distribution assembly  43  and is distributed downwardly through direct heat exchange section  44  which is usually comprised of a series of fill sheets made of polyvinyl chloride. The top  43 A of the evaporative liquid distribution assembly  43 , is usually closed. Air passed across and generally upwardly through direct heat exchange section  44  entering through air inlet  48  and with air drawn by fan  46 . Note that air inlet  48  can be partially open to change the air flow ratio between the indirect and the direct heat exchange sections or can be fully closed which allows the full amount of air entering the direct heat exchange section. Indirect heat exchange section  45  is usually comprised of a series of plate heat exchangers  45 A. Such plate heat exchangers allow a fluid to be passed through the joined plates or cassettes thereby exposing such fluid to a large surface area of the plates themselves. Such plates are usually arranged such that a space between each joined plate pair or cassette is provided for the evaporative liquid to be passed there through, currently with air, to allow both sensible and latent heat transfer of the evaporative liquid passing between the plates. Further air enters and passes across and upwardly through the plate heat exchanger  45 . Air is drawn through air inlet  47  and outwardly by fan  46 . Evaporative liquid passing downwardly through indirect heat exchange section  45  is collected in sump  49 A and is pumped upwardly by pump  49  to be distributed again through evaporative liquid distribution assembly  43 . 
     It should be understood in the operation of heat exchanger  30  and heat exchanger  40  described above, that depending on the performance required, both such heat exchangers may be operated with both evaporative liquid exiting the evaporative liquid distribution system and the fan drawing air across and through the direct and heat exchange sections. It is possible to operate without the fan drawing air across the indirect and direct sections, such that only the evaporative liquid would exit and pass downwardly and through the indirect and direct heat exchange sections. Finally, it is possible that the evaporative liquid would not be supplied through the evaporative liquid distribution assembly, and the heat exchanger would operate only with the fluid passing through the indirect heat exchange section joined plate pairs or cassettes being cooled, heated, condensed, or evaporated by air passing across and upwardly there through drawn by the fan in the heat exchanger or cooling tower. 
     Referring now to  FIG. 5 , a fifth embodiment of the present invention is shown as a heat exchanger in a closed circuit cooling tower assembly  50 . Such heat exchanger is shown to be comprised of a direct heat exchange section  54  located generally above two indirect heat exchange sections  55 . Direct heat exchange section  54  is usually comprised of a series of fill sheets with each fill sheet being comprised of polyvinyl chloride. Each indirect heat exchange section is comprised of a plate heat exchanger arrangement having a fluid outlet  52  and a fluid inlet  51 , which can be reversed if it is desired. Air is drawn inwardly through air inlets  57  by fan  56 . Evaporative liquid passes from evaporative distribution assembly  53  downwardly and through direct heat exchange section  54 . Evaporative liquid passing through direct heat exchange section  54  passes downwardly through both indirect heat exchange sections  55 . Evaporative liquid passing from indirect heat exchange sections  55  is collected in sump  59 A, and is pumped upwardly by pump  59  for distribution through evaporative liquid distribution assembly  53 . Indirect heat exchange section  55  is comprised of a collection of joined plate pairs or cassettes  55 A. Each plate pair is separated such that evaporative liquid passing downwardly through indirect heat exchange section  55  can draw heat from the fluid within plate pairs  55 A sensibly by contact with the outside of the plates. All of the heat is eventually released to the air from the evaporative fluid in both latent and sensible fashions in the evaporative passage. 
     It should be understood in the operation of heat exchanger  50  described above, that depending on the performance required, such heat exchanger may be operated with both evaporative liquid exiting the evaporative liquid distribution system and the fan drawing air across and through the direct and indirect heat exchange sections. It is possible to operate without the fan drawing air across the indirect and direct sections, such that only the evaporative liquid would exit and pass downwardly and through the indirect and direct heat exchange sections. Finally, it is possible again that the evaporative liquid would not be supplied through the evaporative liquid distribution assembly, and the heat exchanger would operate only with the fluid passing through the indirect heat exchange section plates being cooled, heated, condensed, or evaporated by air passing across and upwardly there through drawn by the fan in the heat exchanger or cooling tower. 
     Referring now to  FIG. 6 , a sixth embodiment of the present invention is shown generally as heat exchanger  60 , which is usually a closed circuit cooling tower. Heat exchanger or cooling tower  60  is seen to be comprised of indirect heat exchange sections  65 . Each indirect heat exchange section  65  is seen to be usually comprised of plate heat exchangers  65 A, which are present as assemblies. Indirect heat exchange section  65  has a fluid outlet  61  and a fluid inlet  62 , which can be reversed if it is desired. An evaporative liquid, usually water, is discharged from evaporative liquid distribution assembly  63  generally downwardly such that evaporative liquid passes downwardly and through indirect heat exchange section  65 . Air is seen to be drawn inwardly through air inlets  67  generally upwardly through indirect heat exchange section  65  by fan  66 . Further, evaporative liquid that passes through indirect heat exchange section  65  is collected in sump  69 A and is pumped upwardly by pump  69  for redistribution through evaporative liquid distribution assembly  63 . Evaporative liquid  63  that passes through plate heat exchanger  65  absorbs heat by contacting the large plate surface of plate heat exchanger  65 A to absorb heat from the fluid within plate pairs  65 A in a sensible fashion. All of the heat is eventually released to the air from the evaporative fluid in both latent and sensible fashions in the evaporative passage. 
     It should be understood in the operation of heat exchanger  60  described above, that depending on the performance required, such heat exchanger may be operated with both evaporative liquid exiting the evaporative liquid distribution system and the fan drawing air up and through the indirect heat exchange sections. If a lesser degree of heat exchange is required, it is possible to operate without the fan drawing air up and through the indirect section, such that only the evaporative liquid would exit and pass downwardly and through the indirect section. Further, if the evaporative liquid would not be supplied through the evaporative liquid distribution assembly, and the heat exchanger would operate only with the fluid passing through the indirect heat exchange section plates being cooled, heated, condensed, or evaporated by air passing up and upwardly there through drawn by the fan in the heat exchanger or cooling tower. Further, the heat exchanger may be operated with the fan drawing air up and through one of the two indirect sections, with or without the evaporative liquid being supplied. 
     Referring now to  FIG. 7 , a seventh embodiment of the present invention is shown generally as heat exchanger  70 , which is generally in the form of a closed circuit cooling tower. Heat exchanger  70  is seen to be comprised of a direct heat exchange section  74  for above two indirect heat exchange sections  75 . Direct heat exchange section  74  is usually comprised of a series of fill sheets each comprised of polyvinyl chloride. Each indirect heat exchange section  75  is seen to be comprised of a series of joined plates or cassettes  75 A with fluid outlet  72  and fluid inlet  71 . These fluid inlet and outlet can be reversed if it is desired. Evaporative liquid is discharged from evaporative distribution assembly  73  downwardly onto and through direct heat exchange section  74 . Evaporative liquid that passes through direct heat exchange section  74  passes downwardly and through indirect heat exchange sections  75 . Evaporative liquid that passes through and out of indirect heat exchange sections  75  is collected in sump  79 A and pumped upwardly by pump  79  for distribution through evaporative liquid distribution assembly  73 . Air enters heat exchanger  70  through air inlet  77  and is drawn inwardly by centrifugal fan  76  and pushed upwardly, or in a counter flow direction, with respect to the evaporative liquid, through indirect heat exchange section  75  and direct heat exchange section  74 . Evaporative liquid that passes through indirect heat exchange section  75  passes between the joined plates or cassettes of plate heat exchangers  75 A thereby providing cooling, heating, evaporating, or condensing to the fluid passing through the joined plate pairs of plate heat exchangers  75 A. Further, the evaporative liquid passes downwardly through indirect heat exchange section  75  passes between the joined plates of plate heat exchanger  75 A along with air to thereby allow both sensible and latent heat exchanges of the fluid passing through the joined plate pairs of heat exchanger  75 A. 
     It should be understood in the operation of heat exchanger  70  described above, that such heat exchanger may be operated with both evaporative liquid exiting the evaporative liquid distribution system and the fan drawing air up and through the direct and indirect heat exchange sections. It is possible to operate without the fan drawing air up and through the indirect and direct sections, such that only the evaporative liquid would exit and pass downwardly and through the indirect and direct heat exchange sections. Finally, it is possible again that the evaporative liquid would not be supplied through the evaporative liquid distribution assembly, and the heat exchanger would operate only with the fluid passing through the indirect heat exchange section plates being cooled, heated, condensed, or evaporated by air passing upwardly there through drawn by the fan in the heat exchanger or cooling tower. 
     Referring now to  FIG. 8 , an eighth embodiment of the heat exchanger in accordance with the present invention is shown generally at  80  which is shown in the form of heat exchanger or closed circuit cooling tower. Heat exchanger  80  is seen to be comprised of a pair of indirect heat exchange sections  85 . Each indirect heat exchange section  85  is comprised of a series of joined plates or cassettes  85 A. Indirect heat exchange section  85  also includes a fluid outlet  81  and a fluid inlet  82 , which can be reversed as it is desired. Evaporative liquid is provided by evaporative liquid distribution assembly  83  to pass downwardly and through each indirect heat exchange section  85 . Such evaporative liquid that passes through indirect heat exchange sections  85  is collected in sump  89 A and is pumped upwardly by pump  89  back to evaporative liquid distribution assembly  83 . Air that is drawn in air inlet  87  by centrifugal fan  86  passes generally upwardly or in a counter flow direction through indirect heat exchange sections  85 . Evaporative liquid that passes through heat exchange section  85  passes between the joined plate pairs or cassettes of plate heat exchanger  85 A such that the fluid passing through the joined plates of exchanger  85 A is cooled, heated, condensed, or evaporated both sensibly and in a latent manner by such evaporative liquid passing downwardly over the outer surface area of the joined plates of plate heat exchanger  85 A along with air. 
     It should be understood in the operation of heat exchanger  80  described above, that such heat exchanger may be operated with both evaporative liquid exiting the evaporative liquid distribution system and the fan drawing air up and through the indirect heat exchange section. It is possible to operate without the fan pushing air up and through the indirect section, such that only the evaporative liquid would exit and pass downwardly and through the indirect heat exchange section. Finally, it is possible again that the evaporative liquid would not be supplied through the evaporative liquid distribution assembly, and the heat exchanger would operate only with the fluid passing through the indirect heat exchange section plates being cooled, heated, condensed, or evaporated by air passing upwardly there through pushed by the fan in the heat exchanger or closed circuit cooling tower. 
     Referring now to  FIG. 9 , a ninth embodiment of the present invention is shown generally at  90  as a heat exchanger or a closed circuit cooling tower. Heat exchanger  90  is seen to be comprised of an indirect sections  95 . Indirect heat exchange section  95  is seen to be comprised of a series of joined plates or cassettes  95 A with fluid outlet  92  and fluid inlet  91 . It should be understood that fluid outlet and fluid inlet  92  and  91  can be reversed if it is desired. As the embodiment shown in  FIG. 9  of heat exchanger  90  is generally of a low profile arrangement, centrifugal fan  96  is seen to be located outside the structure of heat exchanger  90  to thereby draw air inwardly through the fan structure to be passed generally upwardly through and across indirect heat exchange section  95 . Evaporative liquid is distributed downwardly from evaporative liquid distribution assembly  93  to pass downwardly through indirect heat exchange section  95 . Such evaporative liquid that passes out from indirect heat exchange assembly  95  is collected in sump  99 A and is pumped upwardly by pump  99  for redistribution through evaporative liquid distribution assembly  93 . Evaporative liquid that passes through heat exchange section  95  passes between the joined plate pairs or cassettes of plate heat exchanger  95 A such that the fluid passing through inside of the joined plates of exchanger  95 A is cooled, heated, condensed, or evaporated both sensibly and in a latent manner by such evaporative liquid passing downwardly over the outer surface area of the joined plates of plate heat exchanger  95 A along with air. 
     It should be understood in the operation of heat exchanger  90  described above, that such heat exchanger may be operated with both evaporative liquid exiting the evaporative liquid distribution system and the fan pushing air up and through the indirect heat exchange section. It is possible to operate without the fan pushing air up and through the indirect section, such that only the evaporative liquid would exit and pass downwardly and through the indirect heat exchange section. Finally, it is possible again that the evaporative liquid would not be supplied through the evaporative liquid distribution assembly, and the heat exchanger would operate only with the fluid passing through the indirect heat exchange section plates being cooled, heated, condensed, or evaporated by air passing upwardly there through pushed by the fan in the heat exchanger or cooling tower. 
     Referring now to  FIG. 10 , a tenth embodiment of the present invention is shown generally as a heat exchanger  100  or in the form of a closed circuit cooling tower. Heat exchanger  100  is seen to be comprised of an indirect heat exchange section  105  located generally below a direct heat exchange section  104 . Direct heat exchange section  104  is usually comprised of a series of fill sheets each comprised of a polyvinyl chloride. Indirect heat exchange section  105  is usually comprised of a series of plate heat exchanger pairs or cassettes  105 A, having a fluid outlet  101  and a fluid inlet  102 . If it desired, such fluid inlet and outlet can be reversed. Air is seen to be drawn inwardly by fan  106  which is located outside the physical structure or attached to the outside of the physical structure of heat exchanger  100 . This is usually centrifugal fan  106  which brings air inwardly near the side or bottom of heat exchanger  100  and near one end thereof such air is forced upwardly through and across indirect heat exchange section  105  and generally upwardly in a counter-flow direction, with respect to the evaporative liquid, through direct heat exchange section  104 . Evaporative liquid is distributed downwardly from evaporative liquid distribution assembly  103 . Such evaporative liquid passes downwardly through direct heat exchange section  104 . The evaporative liquid that exits direct heat exchange section  104  passes downwardly through indirect heat exchange section  105  and is collected in a sump  109 A. Such collected evaporative liquid is pumped from sump  109 A by pump  109  back to water distribution assembly  103 . Plate heat exchanger pairs or cassettes  105 A are typically spaced from each other such that the fluid passing inside the plates of plate heat exchanger  105  is cooled, heated, condensed, and evaporated both sensibly and in a latent manner by the evaporative liquid passing on the outside of the plate pairs of plate heat exchanger  105  and also by the air being drawn by a counter-current manner across and generally upwardly through indirect heat exchange section  105 . 
     It should be understood in the operation of heat exchanger  100  described above, that such heat exchanger may be operated with both evaporative liquid exiting the evaporative liquid distribution system and the fan forcing air up and through the direct and indirect heat exchange sections. It is possible to operate without the fan forcing air up and through the indirect and direct sections, such that only the evaporative liquid would exit and pass downwardly and through the indirect and direct heat exchange sections. Finally, it is possible again that the evaporative liquid would not be supplied through the evaporative liquid distribution assembly, and the heat exchanger would operate only with the fluid passing through the indirect heat exchange section plates being cooled, heated, condensed, or evaporated by air passing across and upwardly there through forced by the fan in the heat exchanger or cooling tower. 
     Referring now to  FIGS. 11 and 12 , a view of a plate heat exchanger in accordance with the present invention is shown generally at  110 . Each plate heat exchanger is shown to be comprised of a series of joined pairs or cassettes of plates  116  spaced from each other. A fluid outlet header is shown at  112  and a fluid inlet header is shown at  114 . As shown in  FIG. 12 , in a detailed breakaway view, fluid outlet header  112  is seen to include openings  118  such that fluid to be cooled, heated, evaporated or condensed may exit from within each plate pair  116 . Further passageways  120  are shown between plates  116  such that evaporative liquid and air can pass on the outside of plates  116  to provide both sensible and latent heat transfer to the fluid passing within joined plate or cassettes  116  of plate heat exchanger  110 . Each plate cassette  116  is seen to include an internal fluid passageway  122  that allows fluid to be cooled, heated, condensed, or evaporated to enter through fluid inlet header  114 , pass through the interior of joined plate pairs or cassettes  116  and exit through openings  118  in each plate pair to enter outlet header  112 . Such plate heat exchanger assembly  110  is seen to include usually a Chevron, embossing, cross hatch, dimpled, micro structurally extended, or any other surface enhancement pattern on both sides of each cassette assembly  116  to provide increased surface area and turbulent flow to allow improved performance and heat exchange between the fluid within the each cassette  116  and the air and evaporative liquid passing on the outside surface of each cassette  116 . The geometries of the surface enhancement pattern on the plate are strategically selected such that the passageway formed in the space between each cassette assembly  116  allows good heat and mass transfer between the air and the evaporative liquid which pass concurrently between each cassette  116 . This external passageway is usually, but not limited to, a general criss-cross pattern formed as the chevron patterns from adjacent cassettes approach close to, or even contacting, each other. Such arrangement leads to the overall improved performance in all the embodiments of the heat exchanger of the present invention that include an indirect heat exchange section. The surface pattern could be different on each side of the plate. The plate surface could be chemically treated (i.e., nano spray coated) to achieve an optimized surface tension value and thus enhance the air and evaporative liquid interaction. 
     Referring now to  FIG. 13 , a plate heat exchanger in accordance with the present invention is shown generally at  130 . Each such plate heat exchanger is seen to be comprised of a series of adjacent plate pairs or cassettes  136 . Each plate cassette  136  has an internal spacing within to allow a fluid to enter through fluid inlet header  134  pass within each plate cassette  136  and exit through fluid outlet header  132 . Each inlet header includes a spacer ring  134 A to allow header  134  to be affixed to the series of plate cassettes  136 , and an outlet header spacer ring  132 A to allow fluid outlet header  132  to be attached to the series of plate cassettes  136 . Further, spacing  138  is seen in an exploded arrangement to exist between each plate cassette  136  to provide an adequate passageway for evaporative liquid to pass in a cross-current, parallel-current, counter-current or some combination thereof arrangement with assembled plates  136 . Such spacing also allows for air to pass between such plates such air usually being drawn in a cross-current, counter-current, parallel-current fashion or some combination thereof arrangement by fans within the heat exchanger. Such spacing between plate cassettes allows for increased performance of the indirect heat exchange section comprised of plate heat exchanger  130  by allowing both sensible and latent heat exchange to occur between the fluid within each plate pair or cassette  136  and the evaporative liquid and air passing in the passageway between such plate pair or cassettes  136 . The internal passage within each plate cassette is labeled  139 . 
     Referring now to  FIG. 14 , a perspective view of a plate heat exchanger assembly  140  is shown. Plate heat exchanger assembly  140  is seen to be comprised of a series of plate cassettes  146  each of which includes an internal passageway to allow fluid to pass therein. Each plate cassette is seen to ideally be comprised of a chevron or other surface arrangement to provide increased surface area of each plate pair. Plate heat exchanger assembly  140  is seen to also comprise a fluid outlet header  142  connected to the series of plate cassettes by outlet header spacer ring  142 A, and a fluid inlet header  144  connected to the series of plate cassettes  146  by inlet header spacer ring  144 A. Passageway  148  is seen to be created by the extended surface on the outside of each neighboring plate cassette  146  such that an evaporative liquid can be allowed to pass between each plate cassette  146  to provide sensible cooling for the liquid passing within each plate cassette  146 . Further, passageway  148  provides space between plate cassettes  146  such that air can be drawn in a counter-current, parallel-current, cross-current fashion, or some combination thereof arrangement between plate cassettes  146  to also provide both sensible and latent heat exchange with the evaporative liquid, and hence provide indirect cooling, heating, condensing, or evaporating for the fluid within plates  146 . The spacers,  149 , are optional which provide extra structure support to the plate heat exchanger assembly  140  to prevent the extended surface from crushing when the plate heat exchanger assembly  140  is tightened by bolts. Also, the spacers  149  may be used to increase the width of the passageway  148  beyond its natural value which is two times of the height of the extended surface. 
     Referring now to  FIGS. 15-18 , a detailed view of plate heat exchanger assembly  150  is shown. Each plate heat exchanger assembly is seen to be comprised of a series of plate pairs or cassettes  156  with a fluid outlet header  152  and a fluid inlet header  154 . Each fluid inlet header  154  is connected by a fluid inlet header space ring  154 A and fluid outlet header  152  is seen to be connected by a fluid outlet header space ring  152 A. The series of plate pairs or cassettes  156  are seen to be spaced from each other by the extended surface pattern on the outside of each plate cassette  156 . On each plate, the enhanced surface pattern is on both sides. It is composed of extended surfaces (peaks,  158 A) and downwardly extruded surfaces (valleys,  158 B). The peaks  158 A on one side of the plate is the valleys  158 B on the other side (and vice versa). The valleys  158 B touch each other to form the internal passageways  159  within the plate pair or cassette  156 . The peaks  158 A on the outside surface of each plate pair  156  touch the peaks of the neighboring plate pair  156  to form the external passageway  158  (e.g., typically a criss-cross pattern) such that air and evaporative liquid can pass outside and between plate cassettes  156  to provide both good sensible and latent heat exchanges. Each plate cassette  156  is seen to usually have a Chevron or any other surface enhancement pattern on both sides of each cassette assembly  156  to provide increased surface area and turbulent flow to allow improved performance and heat exchange between the fluid within the each cassette  156  and the evaporative liquid passing between each cassette  156 . The geometries of the surface enhancement pattern on the plate are strategically selected such that the external passageways  158  formed in the space between each cassette assembly  156  allows good heat and mass transfer between the air and the evaporative liquid which pass concurrently outside and between each cassette  156 . This external passageway is usually, but not limited to, a general criss-cross pattern. 
     In all the embodiments of the present invention, the plates can be comprised of various steels such as stainless steel or other corrosion resistant steels and alloys. It is also possible that such plates can be comprised of other materials that would lead to good heat exchange between the fluid within the plate and the evaporative liquid or air passing outwardly therefrom. Such materials could be aluminum or copper; various alloys, or plastics that provide corrosion resistance and good heat exchange.