Abstract:
Novel heat exchangers and methods of constructing the heat exchangers for use in indirect evaporative cooling applications. The evaporative apparatus for cooling comprises both a multi-stage indirect evaporative cooling heat exchanger; and a multi-stage sump where each sump stage, in a one-to-one relationship. Other multistage heat exchangers with their associated multistage sumps can be combined, with the cooled air of a first multistage evaporative assembly feeding into the intake end of a second multistage evaporative assembly, and so on. These heat exchangers can be used for comfort and industrial applications cooling. The invention can be an entire assembly for the pre-cooling and cleaning of the air going to a gas turbine or any other air breathing device, with an air washer stage in which air is directly cooled by evaporation and where simultaneously the air is also cleaned of dust, dirt and other impurities.

Description:
[0001]    This application claims the benefit of Provisional Application 60/184,255 filed Feb. 23, 2000. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The invention relates to a method and apparatus for increasing the density of air being used in a compression process such as air compressors, gas turbines and other processes where the increase of air density is important. This invention also relates to a method and apparatus for reducing the temperature of air. It relates to air-conditioning. It relates to heat exchangers.  
         BACKGROUND  
         [0003]    Indirect evaporative cooling invented in the mid-seventies (see, for example, Schlom, et al., U.S. Pat. No. 4,023,949) uses the latent heat of the evaporation of water to remove heat from the air. Direct evaporative coolers on the other hand, also known as swamp coolers, cool the air by passing the air through wet pads by which the evaporative absorption of the latent heat of evaporation by the water directly cools the air. Since the water vapor evaporates directly into the air, the air ends up with a heavy load of moisture. With a third approach, direct refrigeration, the air passes through a heat exchanger where it evaporates a refrigerant such as freon. The latent heat of evaporation of the freon acts on the air through a heat exchanger to cool the air. To recycle the freon additional energy is used to compress and condense the freon vapor back to a liquid, which can then be evaporated all over again. Indirect evaporation evaporates water instead of freon in the heat exchanger. Another difference is that the water vapor is not recaptured and condensed back to the liquid state, as is freon, for example, in the refrigeration case. Therefore the energy use efficiency is increased in the indirect evaporative process because no energy is expended on the condensation of the refrigerant part of a refrigeration process.  
           [0004]    Traditionally, gas turbine intake systems depend upon the density of air to increase efficiency. Three methods, historically, to increase gas turbine intake efficiency include steam injection, refrigeration, and direct evaporative cooling. A less expensive approach to increasing the intake air density by cooling, other than these historical methods, is an indirect evaporative approach. Prior patents in this area include Schlom et al.: U.S. Pat. Nos. 4,023,949; 4,107,940; 4,137,058; 4,156,351 and 4,418,527; Fogelman: U.S. Pat. No. 5,076,347; and Kopko: WO9851916A1.  
           [0005]    Areas in which additional increased efficiency of the indirect evaporative cooling, or the “Everest Cycle” (U.S. Pat. No. 4,0233,949), might be improved include (a) better heat exchange process, (b) better water evaporation process, and (c) bringing the “room inlet dry-bulb” as close as possible to the “exhaust air wet-bulb temperature” so as to increase the thermodynamic efficiency of the actual process.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention comprises novel heat exchangers and methods of constructing the heat exchangers for use in indirect evaporative cooling applications. The heat exchanger is useful for both single and multiple unit (where a plurality of heat exchangers are back-to-back) indirect evaporative processes. The evaporative apparatus for cooling comprises both a multi-stage indirect evaporative cooling heat exchanger; and a multi-stage sump where each sump stage, in a one-to-one relationship with a stage of the multi-stage heat exchanger has sump water at progressively cooler temperatures as one progresses further into the heat exchanger. Because there are separate stages of the heat exchanger and the water sumps, progressive cooling is induced on dry side output air. Other multistage heat exchangers with their associated multistage sumps can be combined, with the cooled air of a first multistage evaporative assembly feeding into the intake end of a second multistage evaporative assembly, and so on.  
           [0007]    As a multi-stage process, for n stages, as n approaches infinity, the thermodynamic efficiency may approach a maximum, since the entropy production dS=Σdq/T may be minimized (S=entropy, dq=heat transferred at temperature T). This is the case where the operational cycle of the multi-stage process is as close to a reversible process as possible. In actual practice most of the thermodynamic efficiency gain may be achieved with four to six stages.  
           [0008]    These heat exchangers can be used for comfort cooling, pre-cooling of intake air for gas turbines and for supplying cooling air for other applications such as electrical generators and lubricating oil coolers. As a comfort, or other cooler, the present invention may be used as either a stand-alone cooling unit or as a precooler for another air conditioning device where it precools the ambient air.  
           [0009]    As an application, the indirect-direct evaporative apparatus can be considered as an entire assembly for the pre-cooling and cleaning of the air going to a gas turbine or any other air-breathing device. As such, an additional stage is included, viz., an air washer stage in which air is directly evaporatively cooled and where simultaneously the air is also cleaned of dust, dirt and other impurities. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    The above and other features and advantages of the invention will be more apparent from the following detailed description wherein:  
         [0011]    [0011]FIG. 1A schematically depicts heat exchanger plates used in this invention, in particular a sinusoidal plate type;  
         [0012]    [0012]FIG. 1B schematically depicts heat exchanger plates used in this invention, in particular a polygonal plate type;  
         [0013]    [0013]FIG. 1C schematically depicts heat exchanger plates used in this invention, in particular, an assembly of two polygonal plates to form an airflow path;  
         [0014]    [0014]FIG. 1D schematically depicts heat exchanger plates used in this invention, in particular, the assembly of  1 C with the inclusion of an intermediate plate;  
         [0015]    [0015]FIG. 2A schematically depicts a polygonal plate with deformations to induce air turbulence, i.e., embossed “turbulators” on the heat exchanger plates;  
         [0016]    [0016]FIG. 2B shows a plate assemblage with deformations to induce air turbulence;  
         [0017]    [0017]FIG. 3A shows a plate assemblage with tabs to induce air turbulence;  
         [0018]    [0018]FIG. 3B shows an intermediate plate with tabs to induce air turbulence;  
         [0019]    [0019]FIG. 3C shows a detail of an individual tab;  
         [0020]    [0020]FIG. 3D a detail depicting a section of an intermediate plate, as in FIG. 3B, showing an associated airflow, as a consequence of a tab in an intermediate plate;  
         [0021]    [0021]FIG. 4A shows a plate assembly without tabs or deformations;  
         [0022]    [0022]FIG. 4B is an end view of a portion of a heat exchanger, showing dividers;  
         [0023]    [0023]FIG. 5 shows a schematic section of two-stage indirect evaporative cooler showing airflow paths;  
         [0024]    [0024]FIG. 6 shows a schematic section of multistage (“n”-series) indirect evaporative cooler showing airflow paths;  
         [0025]    [0025]FIG. 7 shows a schematic section of cascaded sumps;  
         [0026]    [0026]FIG. 8A shows a schematic top view of an indirect evaporative cooler with first indirect stage on sides;  
         [0027]    [0027]FIG. 8B Schematic side view of an indirect evaporative cooler with first indirect stage on sides;  
         [0028]    [0028]FIG. 9 shows a schematic section of multi-stage indirect evaporative cooler with an air washer operating thermodynamically and psychometrically according to the Schlom Cycle;  
         [0029]    [0029]FIG. 10 shows a schematic section of the air washer;  
         [0030]    [0030]FIG. 11 shows a side view of unit described in FIG. 5, with the air intake on the left;  
         [0031]    [0031]FIG. 12 shows an isometric section of the unit described in FIG. 5;  
         [0032]    [0032]FIG. 13 shows an end view and section of intake of the unit described in FIG. 5;  
         [0033]    [0033]FIG. 14 shows an end view and section of discharge of the unit described in FIG. 5;  
         [0034]    [0034]FIG. 15 shows a side view of unit described in FIG. 5, with the intake on right;  
         [0035]    [0035]FIG. 16 shows a top view of the unit described in FIG. 5;  
         [0036]    [0036]FIG. 17 shows a top view of the multi-stage unit shown in FIG. 6;  
         [0037]    [0037]FIG. 18 shows a psychrometric chart depicting various evaporative cycles (direct evaporative cooling, direct evaporative cooling with fogging, multistage indirect evaporative cooling and indirect evaporative cooling with air washer) with comparisons relating to air density;  
         [0038]    [0038]FIG. 19 shows plate dividers made with holes;  
         [0039]    [0039]FIG. 20 shows plate dividers made with slats;  
         [0040]    [0040]FIG. 21 shows plate dividers made with reticulated foam;  
         [0041]    [0041]FIG. 22 shows solid plate dividers;  
         [0042]    [0042]FIG. 23 shows an isometric section of unit depicted in FIG. 9 with item callouts;  
         [0043]    [0043]FIG. 24 shows an isometric section of unit described in FIG. 9 with air flow path depicted;  
         [0044]    [0044]FIG. 25 shows a section of a unit described in FIG. 9, as viewed from intake end;  
         [0045]    [0045]FIG. 26 shows a section of a unit described in FIG. 9, as viewed from discharge end;  
         [0046]    [0046]FIG. 27 shows a psychrometric chart depicting the thermodynamic path of an “n”-series arrangement of heat exchangers, for n=4;  
         [0047]    [0047]FIG. 28 shows a section of a unit described in FIG. 9, with item callouts. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0048]    The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is merely made for the purpose of describing the general principles of the invention. The scope of the invention should be determined with reference to the claims.  
         [0049]    The item call-out numbers and description are listed below for reference:  
         [0050]    Item No. Description  
         [0051]    [0051] 1002  Sinusoidal plates.  
         [0052]    [0052] 1004  Polygonal plates.  
         [0053]    [0053] 1006  intermediate in assemblage of FIG. 1D.  
         [0054]    [0054] 1008  Deformed portion of plate to induce turbulence.  
         [0055]    [0055] 1010  Tabs and /or deformations to induce turbulence.  
         [0056]    [0056] 1012  Section of intermediate plate with deformations causing airflow to change direction.  
         [0057]    [0057] 1014  Dry side air path (primary air).  
         [0058]    [0058] 1016  Wet side air path (secondary air).  
         [0059]    [0059] 1018  Dry side air-leaving.  
         [0060]    [0060] 1020  Wet side air-leaving.  
         [0061]    [0061] 1022  Wet side fan/s  
         [0062]    [0062] 1024  Foundation (base).  
         [0063]    [0063] 1026  Sump/s.  
         [0064]    [0064] 1028  Spray manifold.  
         [0065]    [0065] 1030  Water Inlet.  
         [0066]    [0066] 1032  Float valve.  
         [0067]    [0067] 1034  Water line from float valve to first sump.  
         [0068]    [0068] 1036  Sump  
         [0069]    [0069] 1038  Water transfer pipe.  
         [0070]    [0070] 1040  Overflow/drain pipe.  
         [0071]    [0071] 1042  Screens.  
         [0072]    [0072] 1044  Spray manifold-Air Washer.  
         [0073]    [0073] 1046  Cover, Air Washer-primary media.  
         [0074]    [0074] 1048  Cover, Air Washer-secondary media.  
         [0075]    [0075] 1050  Primary evaporative media.  
         [0076]    [0076] 1052  Secondary evaporative media.  
         [0077]    [0077] 1054  Distribution pump-primary media.  
         [0078]    [0078] 1056  Distribution pipe-secondary media.  
         [0079]    [0079] 1058  Pump spray manifold-Air Washer  
         [0080]    [0080] 1060  Pump/s primary and secondary media.  
         [0081]    [0081] 1062  Pipe from pump to spray manifold.  
         [0082]    [0082] 1064  Pipe from pump/s to media distribution pipes.  
         [0083]    [0083] 1066  Access panel  
         [0084]    [0084] 1068  Housing.  
         [0085]    [0085] 1070  Moisture eliminator  
         [0086]    [0086] 1072  Airflow path from primary to secondary air (indirectly cooled air now goes to the wet side of the next stage).  
         [0087]    [0087] 1074  Heat exchanger assembly.  
         [0088]    [0088] 1076  “n” series unit and components.  
         [0089]    [0089] 1078  Plate separator with holes-end view.  
         [0090]    [0090] 1079  Plate separator with holes-side view.  
         [0091]    [0091] 1080  Plate separator with slats (louvers)-end view.  
         [0092]    [0092] 1081  Plate separator with slats (louvers)-side view.  
         [0093]    [0093] 1082  Plate separator of reticulated foam-end view.  
         [0094]    [0094] 1083  Plate separator of reticulated foam-side view.  
         [0095]    [0095] 1084  Plate separator, solid-end view.  
         [0096]    [0096] 1085  Plate separator, solid-side view.  
         [0097]    [0097] 1086  Strainer for pump/s.  
         [0098]    [0098] 1088  Intake air hood.  
         [0099]    [0099] 1090  Intake air filters.  
         [0100]    [0100] 1092  Framework (structure).  
         [0101]    [0101] 1094  A-B Air flow through heat exchanger to plenum.  
         [0102]    [0102] 1094  B-C Air flow downward in plenum.  
         [0103]    [0103] 1094  C-D Air flow from plenum into sump area.  
         [0104]    [0104] 1094  D-E Air flow upward through wet side of heat exchanger to atmosphere.  
         [0105]    [0105] 1096  Air discharge housing.  
         [0106]    [0106] 1098  Plenum (this is where air which has been indirect evaporatively cooled leaves the dry side of the heat exchanger and then enters the wet side of the next stage).  
         [0107]    The new heat exchanger design utilizes plates or sheets of material in either a or a sinusoidal  1002  shape (FIG. 1A) or a polygonal  1004  shape (FIG. 1B) in cross section, either one of which closely approximates a repeating wave form. The plates  1004  (FIG. 1C) may be arranged in pairs forming channels for air flow; the arrows in FIG. 1C indicate the air flow. Optionally, as an enhancement of the heat exchanger, pairs of plates may optionally utilized an intermediate plate  1006  to separate the plate pair and to provide a uniformly shaped channel between them. The purpose of this intermediate plate  1004  (FIG. 1D) is to form another heat transfer surface, transferring heat between the center of the airflow and the polygonal walls.  
         [0108]    The plates may be fabricated from one or more of a number of materials. Any thermally conductive material may be a candidate. Without limiting or restricting the material or materials of which the sheets of material might be fabricated, a number of candidate materials are nevertheless listed. These include steel, galvanized iron, galvanized steel, stainless steel, thermally conductive plastic, thermally conductive ceramic, metal coated with paint, metal coated with varnish, metal coated with plastic, metal coated with ceramic, metal coated with glass, metal coated with diamond-like coating, titanium thermally conductive composite, aluminum, magnesium, copper or silver.  
         [0109]    Since turbulent air flow over a water surface can increase the evaporation rate for a given net air flow rate, increased roughness and vortex generators are used to increase the turbulence of the air flowing over the water film as the water film itself gravitationally flows down toward a sump. Extrapolation of known data of ocean surface roughness related to evaporation rates yields a factor of three or more for the rate of increased evaporation for turbulent air flow compared to a laminar type of air flow over a smooth ocean.  
         [0110]    Another use of this intermediate plate is to provide a support surface for tabs and fins which help enable turbulence in the air flowing over them. The turbulence will improve the heat transfer by changing the laminar flow to turbulent flow.  
         [0111]    One method of initiating turbulence in the air flow is the use of irregularities ( 1008 , FIG. 2A) mechanically or otherwise produced on the surface of the preformed sheets  1002  (FIG. 1A),  1004  (FIG. 1B) used to produce the “pairs” (FIG. 1C). The roughness of these irregularities gives rise to a mixing length of increased turbulent vertical mixing into the airflow. These irregularities can be produced either by embossing the material  1008  (FIG. 2A, 2B) or by mechanically attaching tabs, fins  1010  (FIG. 3A, 3B,  3 C) or “turbulators”, to which these tabs, fins, embossments and bumps will be generically referred. The embossments  1008  (FIG. 2A) may be applied to the inside of the outer walls of the plate pair channels as shown in FIGS. 2A and 2B.  
         [0112]    The tabs  1010  (FIG. 3B) are shown formed on an intermediate plate  1006 . FIG. 3A shows the assembly as in FIG. 1D, but with the intermediate plate  1006  having tabs  1010 . The turbulators act on the process air flow produce vortex eddies and breakup the laminar flow. FIG. 3D shows an air flow condition (arrows)  1012  on a tab  1010  on an intermediate plate  1006 .  
         [0113]    Bumps or tab-like elements can also be added from any material compatible with the basic structure. These may include such materials as sintered metal powder and foamed metal, which, when applied act to increase surface roughness, and may also act to increase the total wetted surface. For many of the tabs or bumps, water flowing gravitationally down a channel may encounter a vertex or edge of a tab, bump or other attached material, and may fall off that object as a droplet, with the potential to provide a greater evaporation rate, as a droplet will expose more surface area. The net effect of introducing methods and devices for producing turbulence is to increase the efficiency of operation of the overall apparatus.  
         [0114]    [0114]FIG. 4A shows an assembly of polygonal plates  1004  and the optional intermediate plate  1006 . FIG. 4B shows several assemblies as in FIG. 4A further assembled into a heat exchanger with polygonal plates  1004 , intermediate plate  1006  dividers, and also shows the dry side air path (primary air)  1014  and the wet side air path (secondary air)  1016 .  
         [0115]    [0115]FIG. 5 shows a schematic section of the two-stage version of the indirect evaporative cooler, showing airflow paths. FIG. 5 shows the dry side (primary) air path  1014 , the wet side (secondary) air path  1016 , the dry side air leaving  1018  the unit, the wet side air leaving  1020  and the airflow path from the primary to the secondary air  1072 . The two-stage version of the evaporative cooler sits on a base  1024 , which supports sumps  1026  which collects water cascading down the cooler which is sprayed by the spray manifold  1028 . The wet side air  1016 ,  1020  is drawn out by the wet side fans  1022 .  
         [0116]    [0116]FIG. 6 shows a schematic section of an n-stage (five stages are shown) indirect evaporative cooler. The incoming dry side (primary) air  1014  enters from the left of FIG. 6 and ultimately exits  1018  on the right. The wet side air  1016  enters from the bottom (left) and some exits through the top  1020 , drawn up by the wet side fans  1022 .  
         [0117]    However, in the n-stage process, some of the dry side air, at each stage, is redirected into the wet side air, at a next successive stage. Consequently, the already cooled dry side air becomes the wet side air, resulting in a lower temperature wet side air with a lower wet side dew point temperature. The effect, as will be seen, is to efficiently cool the dry side air which exits  1018  to a lower temperature air stream with a higher air density. The coldest dry-side  5002  (FIG. 5) is being cooled by the coldest water and the coldest air with the lowest wet bulb temperature.  
         [0118]    Another advantageous feature of this embodiment of the heat exchanger is to provide separate, distinct sumps  1036 ,  1036 ,  1036  (FIG. 7) for the water utilized on the “wet side” of the heat exchanger. The separate sumps maintain the coldest water on the leaving side of the heat exchanger. Additionally, these sumps can be arranged in a “cascade” fashion (FIG. 7, 1036,  1036 ,  1036 ) where the water flows from the coldest sump  1036  on the right to the warmest sump,  1036  on the left.  
         [0119]    A float valve  1032  regulates the refilling of the coldest sump  1036  on the right, as required, by the level in the warm-side sump  1036  on the left. When the level in the sump  1036  on the left falls, the float valve  1032  allows water to enter from the water inlet  1030 . The water line  1034  from the float valve to the first sump  1036  on the right, allows the first sump to be refilled according to the level of the last sump ( 1036  on the left). Water transfer pipes  1038  and an overflow (and drain) pipe  1040  complete the sump system.  
         [0120]    Each separate sump sits at the bottom of separate spray systems  1028  (FIG. 5) with separate pumps that supply each separate spray and sump unit. In the preferred embodiment the first sump  1036  (on the right) would be at the air washer, or, at the last heat exchanger, if a direct evaporative stage were not used. In this embodiment water is supplied to the direct evaporative stage only and then flows down to the lowest sump where any excess water is discharged. Also, at this point sufficient “bleed”  1040  will be employed to maintain a low concentration of dissolved solids in the water to prevent the build-up of dissolved solids on the walls of the heat exchanger. Because the different sumps are sufficiently thermally insulated, and the air progressing through each partition or stage, is tending to be cooler than the previous stage or partition, the temperature of the thermally graded sumps both reflect this increased cooling and contribute to it.  
         [0121]    A unique feature of the heat exchanger is that it provides for a portion of the air to be first indirectly evaporatively cooled and then used  1072  (FIG. 8A, 8B) for the wet side of the final portion of the heat exchanger. FIG. 8A shows a schematic top view of an embodiment of the indirect evaporative cooler with a first indirect stage on the sides. FIG. 8B shows a schematic side view of an embodiment of the indirect evaporative cooler with a first indirect stage on the sides.  
         [0122]    Advantageously, this process within the heat exchanger itself significantly improves performance. Previous technology utilized separate heat exchangers to achieve this process. The air tends to evaporate the water. The water changes from a liquid to a vapor state, which requires a gain of molecular kinetic energy. This gain of molecular kinetic energy is at the expense of the remaining water, which loses that amount of energy, expressed as the latent heat of evaporation. Thus, the temperature of the unevaporated water and the heat exchange surfaces in contact with it reflect some decrease in their molecular kinetic energy (conservation of energy). The decreased molecular kinetic energy is (expressed as) a decreased temperature. A wet-bulb temperature is that temperature to which a fully aspirated thermometer would fall due to the evaporation from water which is continuously supplied to it by a wetted wick. In order to further cool that wet bulb thermometer, one needs to bring it in contact with matter that is at a lower temperature. Then, sensible heat is transferred from the thermometer to the colder matter. The sensible heat transfer is in the form of the thermometer&#39;s higher kinetic energy molecules transferring kinetic energy to the lower kinetic energy matter. This transfer of sensible heat can then lower the thermometer&#39;s temperature below the wet bulb temperature, if the temperature of the colder matter is below the thermometer&#39;s wet bulb temperature. Air from the dry side which has been cooled toward the wet bulb temperature of the wet side air has a lower dry bulb temperature.  
         [0123]    If one places an imaginary box around the n-stage heat exchanger, one may examine aspects of its efficiency. The wet side air process is evaporating water. The evaporation is a change of phase and takes place isothermally. For an amount of (latent) energy equal to L released, some amount is absorbed by the dry side air, L-dL. The quantity dL represents energy loss not transferred to the dry air. The amount of entropy transferred in from the ambient temperature wet side air flow is: L/T ambient  while the entropy carried out by the dry side air is (L−dL)/(T ambient −dT) since the dry side air has been sensibly cooled. The difference is then: heat absorbed at the higher temperature minus the heat rejected at a lower temperature, or, 
         (T ambient dL−LdT)/(T ambient (T ambient −dT)). 
         [0124]    Where the latent heat loss (dL) is kept as small as feasible, the determining factor is LdT. Since L is a constant, the difference between the temperature at the wet side air and the dry side air flow (dT) determines the efficiency of the process. The smaller dT, the more efficient the process. In the multistage process, dT is automatically kept small by utilizing some of the cooled dry air flow for the next stage of the wet side cooling.  
         [0125]    [0125]FIG. 9 shows a schematic section of multi-stage indirect evaporative cooler with an air washer operating thermodynamically and psychometrically according to the Schlom Cycle. The dry air  1014  enters from the left; the wet air  1016  enters from the left bottom. Some of the cooled dry air is used  1072  on the wet side of the next stage. The separate sumps  1026  are fairly thermally isolated from each other. The final, cool dry air  1018  exits on the right to be used, for example, in an electric generating gas turbine. Screens  1042  are placed in the air stream  1018 . Spray manifolds  1044  provide the washing of the air. There is a cover  1046  for the primary media and a cover for  1048  the secondary media.  
         [0126]    [0126]FIG. 10 shows a schematic section of an air washer operating thermodynamically and psychometrically according to the Schlom Cycle. The air washer is the final stage in this indirect-direct evaporative process. It represents a direct evaporative mode. In the air washer, the air receives its final cooling and is also thoroughly cleansed of dirt and pollutants of all types. The air washer consists of two sub-stages. The first sub-stage is a spray section  1044  where the air must pass through a deluge of fine spray (not mist)  1044 . The second, final, sub-stage comprises two media type sub-stages  1046 ,  1048 . In these two media type substages clean flowing water  1054  (distribution pipe for the primary media),  1056  (distribution pipe for the secondary media) removes any dirt that may have gotten through the previous stages. Also, that clean flowing water  1054 ,  1056  will re-dissolve any salts that may have been entrained in the evaporation in the previous stages.  
         [0127]    In the first air washer sub-stage, the nozzles  1044  (FIG. 10) are supplied with clean water, which has been cleansed by use of ten-micron filtration. In this preferred embodiment, this water can be at normal line pressure (50-70 psi) or can be supplied from the sump by means of a pump at pressures as low as 5-10 psi. Any workable pressure range may be utilized. Screens  1042  in this air stream are also employed to further breakup the droplets. The spray manifold  1044  directs its water droplet spray into the screens  1042  where they tend to be broken into smaller spay droplets by hitting the screens with the dry air flow ( 1018 -arrows shown but not number) entering from the left.  
         [0128]    [0128]FIG. 10 shows a schematic section of the air washer including the pump spray manifold  1058  for the water supply through pipe  1062  to the spray manifold  1044 . A pump  1060  supplies water for the primary  1050  and the secondary  1052  media through the pipes  1064 .  
         [0129]    The air velocity in this air washer section sub-stage is kept low enough to prevent moisture carryover to the final sub-stage. For a preferred embodiment, this may entail air velocity staying below 500 feet per minute. Excess water from this sub-stage sump  10261  will flow to the sump  10262  of the final stage of the heat exchanger where it will be used on that stage&#39;s wet side.  
         [0130]    The final media sub-stage consists of media  1050 ,  1052  such as a cross-fluted design implemented in a cellulose paper, such as Munters “CELDEK”™, or implemented in glass matting, such as Munter&#39;s “GLASDEK”™, which is supplied with very clean water  1054 ,  1056 , which has been cleansed with a one-micron filter. Since almost no evaporation occurs in this stage only a very small amount of water is needed, just that amount which is sufficient to maintain wetness throughout this section. Not only will this sub-stage remove any particulate matter which may have gotten past the prior sub-stage, it will also cause any dissolved solids which may have evaporated to again be re-dissolved and then flushed from the system.  
         [0131]    A proprietary media may also be used in this stage. It is designed to allow the purified water to very effectively clean the air flowing through it and to not require frequent replacement. The water in this air washer section sub-stage will be passed through one time only and not used again in this sub-stage. This water will go to the sump  10261  of an indirect evaporative stage where it will be filtered before being used in that stage.  
         [0132]    This use of this air washer relieves normal intake air filters of a great deal of their work. Before, their role was to remove all potential airborne particulate matter, which could be injurious to the gas turbine. Now they only need remove large particulate matter such as bugs, leaves, feathers and other large items, which could be harmful to the heat exchanger.  
         [0133]    Advantageously, the air washer sub-stage will provide the cleanliness required by the turbine utilizing potable water only, without any de-ionized water. The use of normal potable water for cleaning the air is a great improvement over current practice, which requires more expensive de-ionized water as the basis of the method of achieving great cleanliness. Advantageously, it should be noted that the addition of water vapor to the cooled air fed to a gas turbine might have a significant impact in reducing emissions of NOx and other pollutants.  
         [0134]    [0134]FIG. 11 shows a side view of unit described in FIG. 5, with the air intake on the right showing wet side fans  1022 , foundation  1024 , housing  1068 , wet side air flow  1016 , pipe from pump to spray manifold  1062  and access panel  1066 .  
         [0135]    [0135]FIG. 12 shows an isometric section of the unit described in FIG. 5. The wet side air inflow  1016  is shown along with a float valve  1032 , together with a pump for the spray manifold  1058 , an overflow/drain pipe  1040 , a sump  1036 , the foundation  1026 , the heat exchanger assembly  1074 , the spray manifold  1028 , housing  1068 , access panel  1066 , a wet side fan  1022 , and the airflow path from primary to secondary air  1072 .  
         [0136]    [0136]FIG. 13 shows an end view and section of intake of the unit described in FIG. 5. The float valve  1032  may be seen, together with an overflow/drain pipe  1040 , foundation  1024 , housing  1068 , the heat exchanger assembly  1074 , a pipe from the pump to the spray manifold  1062 , a spray manifold  1028 , a wet side fan  1022  and a moisture eliminator  1070 .  
         [0137]    [0137]FIG. 14 shows an end view and section of discharge of the unit described in FIG. 5. The overflow/drain pipe  1040  may be seen, together with the foundation  1024 , housing  1068 , the heat exchanger assembly  1074 , a pipe from the pump to the spray manifold  1062 , a spray manifold  1028 , a wet side fan  1022 , access panel  1066  and a moisture eliminator  1070 .  
         [0138]    [0138]FIG. 15 shows a side view of unit described in FIG. 5, with the intake on left. The foundation  1024 , wet side air flow in  1016 , housing  1068  and wet side fans  1022  are shown.  
         [0139]    [0139]FIG. 16 shows a top view of the unit described in FIG. 5 with wet side fans  1022  and housing  1068 .  
         [0140]    [0140]FIG. 17 shows a top view of the multi-stage unit shown in FIG. 6 with n-series units and components  1076  indicated.  
         [0141]    [0141]FIG. 18 shows a psychrometric chart depicting various evaporative cycles (direct evaporative cooling, direct evaporative cooling with fogging, multistage indirect evaporative cooling and indirect evaporative cooling with air washer) with comparisons relating to air density.  
         [0142]    [0142]FIG. 19 shows plate dividers made with holes, including an end-on view  1078  and cross section  1079 . FIG. 20 shows plate dividers made with slats, including an end-on view  1080  and a cross section  1081 . FIG. 21 shows plate dividers made with reticulated foam, including an end-on view  1082  and a cross section  1083 . FIG. 22 shows solid plate dividers, including an end-on view  1084  and a cross section  1085 .  
         [0143]    [0143]FIG. 23 shows an isometric section of unit depicted in FIG. 9. It shows the wet side air inflow  1016  along with a float valve  1032 , a strainer for the pump  1086 , sumps  1036 , the foundation  1024 , the heat exchanger assembly  1074 , the spray manifold  1028 , framework  1092 , intake air hood  1088 , a wet side fan  1022 , intake air filters  1090 , moisture eliminator  1070 , air washer cover for the primary media  1046 , air washer cover for the secondary media  1048 , air discharge housing  1096 , air washer spray manifold  1044 , primary evaporative media  1050 , and the secondary evaporative media  1052 .  
         [0144]    [0144]FIG. 24 shows an isometric section of unit described in FIG. 9 with airflow path depicted  1094 . The airflow  1094  on the path A to B is the airflow entering the heat exchanger and flowing through to the plenum. On the next leg of flow, on path B to C, the flow is downward in the plenum. On the next leg of airflow, the path is C to D, from the plenum to the sump area. On the last leg of airflow shown, the path is from D to E, from the sump area upward through the wet side of the heat exchanger, into the atmosphere.  
         [0145]    [0145]FIG. 25 shows a section of a unit described in FIG. 9, as viewed from intake end. It shows the foundation  1024 , a pump for the spray manifold  1058 , a pipe from the pump to the spray manifold  1062 , sumps  1036 , the heat exchanger assembly  1074 , the spray manifold  1028 , the framework  1092 , wet side fans  1022 , moisture eliminator  1070 , an air washer spray manifold  1044 , primary evaporative media  1050 , and the secondary evaporative media  1052 .  
         [0146]    [0146]FIG. 26 shows a section of a unit described in FIG. 9, as viewed from discharge end. It shows the foundation  1024 , a pump for the spray manifold  1058 , a pipe from the pump to the spray manifold  1062 , sumps  1036 , the heat exchanger assembly  1074 , the spray manifold  1028 , the framework  1092 , wet side fans  1022 , moisture eliminator  1070 , primary evaporative media  1050 , and the secondary evaporative media  1052 .  
         [0147]    [0147]FIG. 27 shows a psychrometric chart depicting the thermodynamic path of an “n”-series arrangement of heat exchangers, for n=4. In the progressive lowering of the temperature, from point  1  to point  2  to point  3  to point  4 , the progressively smaller enthalpy changes are denoted, Δh 1 , Δh 2 , Δh 3 , and Δh 4 , where Δh 1 &gt;Δh 2 &gt;Δh 3 &gt;Δh 4 . This illustrates that the effect of n-stages converges rapidly during the first four to six multi-stages.  
         [0148]    [0148]FIG. 28 shows a section of a unit described in FIG. 9. It shows the foundation  1024 , a pump for the spray manifold  1058 , sumps  1036 , the heat exchanger assembly  1074 , the spray manifold  1028 , the framework  1092 , wet side fans  1022 , moisture eliminator  1070 , an air washer spray manifold  1044 , air washer cover  1046  for the primary evaporative media, air washer cover  1048  for the secondary evaporative media and the air discharge housing  1096 . It also shows the wet side air inflow  1016 , the dry side inward airflow  1014 , the dry air outflow  1018 , pumps for the spray media  1060 , intake air hood  1088  and intake air filters  1090 .  
         [0149]    Advantageously, this invention utilizes more airflow  1016  (FIG. 28) on the wet side as compared to the dry side  1014 . This greater airflow on the wet side relative to the dry side creates a much higher thermal efficiency. Air from the wet side, which is not recirculated to the dry side, in circumstances where that is done, or otherwise utilized, is dumped to the atmosphere  1020  (FIG. 5). In this invention, there is no need to keep the airflow on the wet side comparable to that on the dry side. Therefore, the relative rate of flow of wet side air to dry side airflow can be chosen to attempt a highest feasible efficiency.  
         [0150]    While in the past heat exchangers tended to utilize tubes or a semi-rectangular shape arranged vertically and tended to have header sheets at each end to keep the primary and secondary air flows separated, the new shape can be utilized in either vertical or horizontal applications.  
         [0151]    When used as a pre-cooler for gas turbines the preferred method is to have the tubes horizontal, in the direction of airflow to the gas turbine intake. In this situation, the length of the plates can be adjusted to provide sound attenuation as “tuned lengths” to damp out specific frequencies. Additionally, the heat exchanger can be made up of two or more sections each of a different length so that several frequencies can be damped out. A further embodiment utilizes a space or plenum between heat exchanger sections, these sections acting as expansion chambers to further dampen the noise, and sound attenuation devices can also be installed in these expansion chambers.  
         [0152]    What is described is a complete, unique, system for cooling and cleaning the air being used by a gas turbine. This cycle is far more efficient than any system now on the market or even contemplated in any theoretical literature. The psychrometric chart (FIG. 11) shows graphically how this technology advantageously compares with other technologies and how on a normal warm day in semi-arid regions can provide air at a density almost equal to IS 0  conditions. From the starting point of nominal ambient conditions of temperature of about 100° F. (point A, FIG. 18) and a wet bulb temperature of about 70° F. (point A, FIG. 18) with a relative humidity of about 22% (point A, FIG. 18), one can reach a dry bulb temperature for the cooled air of about 65° F. (point E, FIG. 18). Starting at (point A, FIG. 18), one can move along a line of constant moisture or water content to (point E, FIG. 18) by indirect evaporative cooling. In the indirect evaporative cooling, moisture is not being taken out of the “dry” side air. Direct evaporative cooling, where the enthalpy, or sensible heat is constant is not added, leads to a wet bulb temperature of about 58° F. (point F, FIG. 18). In the multi-stage process, under the same approximate conditions, one may achieve about a dry bulb temperature of about 53.5° F., with a less consumption of energy, because the n-stage process operates more efficiently  
         [0153]    While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.