Abstract:
The present invention relates to a method and an apparatus for providing enhanced indirect evaporative cooling of air, water, fuel, or other fluids while controlling the humidity. The design makes cooling down to the dew point possible without energy input other than the energy to produce the fluid flow needed. The design makes use of stacked composite plates ( 7 ) with channels ( 1, 2 ) for fluid flow between adjacent plates. On opposing surface areas of these plates, there are wet areas ( 4 ) or dry areas ( 3 ). The wet areas ( 4 ) provide cooling by conventional evaporation which is in turn used to cool the fluids in contact with the dry areas ( 3 ). The benefit is controlled heat transfer, which allows selected cooling of fluid flow such that the temperature as low as dew point are reachable.

Description:
[0001]    Applicant hereby claims benefit of a provisional application filed on Feb. 7, 2000 entitled “Dew point evaporative cooler,” serial No. 60/180,819, and provisional application filed on Jan. 31, 2001 entitled “Indirect Evaporative Cooling Mechanism,” Docket No. 163P. 
     
    
     
       FIELD ON THE ART  
         [0002]    The present invention relates to methods and apparatus for indirectly cooling a fluid by evaporation and more specifically to a method and an apparatus for cooling air, or a product other than air, to substantially the dew point temperature of the air used in the evaporative cooling.  
         BACKGROUND OF THE INVENTION  
         [0003]    Indirect evaporative cooling has been used for many years to cool high temperature fluids down to near the wet bulb temperatures for commercial and industrial processes such as refrigeration systems. The use of indirect evaporative cooling for direct air conditioning systems has been commercially available but never commercially viable as proven by the lack of available products on the market at costs that reflects their effectiveness.  
           [0004]    The commercially available indirect evaporative cooling systems use a two-step process for cooling, indirect evaporative cooling of the air to less than half of the difference between the wet bulb temperature and then adiabatic cooling to the final temperature. With this process the temperature is reduced to less than the wet bulb temperature however the humidity is increased significantly. The high humidity limits their use to some residential and industrial applications where temperature not humidity is a concern.  
           [0005]    There are two major problems with evaporative coolers that are to be used for supply of air directly for air conditioning: 1) associated high humidity, and 2) high cost of manufacturing.  
           [0006]    There are several prior art indirect evaporative coolers that have a more thermodynamic efficient indirect evaporative cooling process than older versions. The prior art has not made it to manufacturing most likely due to their lack of understanding of materials needed to realize the efficiency of the process, the physical design of the apparatus that require at least two separate pieces of equipment and the resultant high cost to manufacture the designs.  
           [0007]    This patent describes a method and apparatus for Dew Point Indirect Evaporative Cooling that utilizes a highly efficient thermodynamic process of heat and mass exchange between air and water, or other volatile fluid, is inexpensive to manufacture, providing temperatures that approach the dew point temperature of the entering fluid as opposed to the wet bulb temperature, and with little or no moisture added to the air.  
         DESCRIPTION OF PRIOR ART  
         [0008]    Analogy: U.S. Pat. No. 4,002,040 (dated January 1977). Incorporates indirect evaporative cooling over a number of plates and several airflow designs that includes using some of the precooled dry air as evaporative air. This design requires a higher-pressure drop due to the need of the air to enter, pass through, exit an indirect evaporative cooler, then turn around 180 degrees and reenter the indirect evaporative cooler. The wetting system was proposed to be intermittent to help prevent over wetting, but this is difficult in practice as the drying is dependent on entering air humidity and flow rate. In addition the apparatus will not operate efficiently when either over wetted or partially dried out. The materials to build the apparatus were not discussed, but these affect not only the efficiency but also the manufacturability at a cost that could be desirable to consumers.  
           [0009]    Russian Patent No. 2,037,104 (dated Jul. 7, 1991); U.S. Pat. No. 5,453,223 (filed Sep. 12, 1994), [though applicant does not admit the validity of the U.S. patent, as it was filed more than one year after the disclosure was public knowledge]. Disclosed using a square plate design with cross flow between the plate heat exchange surfaces. The plates were designed to have wet and dry zones with the opposing sides of the plate being dry and wet respectively. The wet and dry zones were created along the diagonal of the square plate where the air entered along a dry surface and proceeded to a wet surface where it departed. Because the plates had wet zones with opposing dry zones, the air passing in cross flow over them would be indirectly cooled. The design provided for pre-cooling of the air before entering an evaporative section and then the flow was split providing either waste heat exhaust air or cooling air to the user.  
           [0010]    This prior art designs have the following disadvantages:  
           [0011]    The existing method and design always increases the absolute humidity of air used.  
           [0012]    In some applications higher humidity is not wanted.  
           [0013]    The inefficiency of the working air&#39;s lower exhaust temperatures indicating the loss of cooling capacity.  
           [0014]    The unit&#39;s inability to cool a product other than air.  
           [0015]    The inability to separate the air streams entering the cooler for more efficient operation. Hot dry air coming out of a dehumidification process, separating from recirculating inside air.  
           [0016]    The unit lacked flow direction in channels causing air mixing and therefore temperature mixing preventing the greatest possible temperature differences across a plate. This prevents the lowest possible outlet temperatures. The lack of flow direction also causes uneven or stagnated flow diminishes the effectiveness of the surface area of the plates.  
           [0017]    Inefficient direct evaporative section of cooling air, caused by having an impervious surface on one side of the plate.  
           [0018]    The concepts were never put into practical application most likely due to their complex design and expensive fabrication requirements.  
           [0019]    The plates did not have a common wick material making it difficult to wet the plates.  
           [0020]    The design did not allow for non horizontal wetting of panels or using natural capillary transporting of water to wet moist surface.  
           [0021]    The design requires higher-pressure drops and thus impaired efficient surface area use.  
           [0022]    The proposed method and apparatus for this invention eliminates these disadvantages.  
         SUMMARY OF THE INVENTION  
         [0023]    The purpose of the method and apparatus for dew point indirect evaporative cooling is to provide the product fluid for example air, water, oil, etc., which is cooled by passing multiple product streams through the invention apparatus to a user. The apparatus uses multiple working air streams that are first precooled and then passed in cross flow, or counter flow, over an indirect evaporative cooling plate The working air streams, by evaporation, take heat from the heat exchange plate, which provides the interface between the working air and the product stream fluid, which in turn takes heat from the product fluid.  
           [0024]    A further object is to obtain lower temperatures when air is used as the product fluid, by using an adiabatic evaporative section added after the indirect cooling dry section, creating an efficient direct evaporative process within the same apparatus.  
           [0025]    Due to the thermodynamic cycle in the working air, a further refinement of the apparatus, air can be heated before entering the apparatus in some humid climate conditions to provide added cooling capacity by providing greater latent heat capacity. This may be done by direct heat input or by removing humidity from the entering air  
           [0026]    Another object of this invention is to allow the humid working air exhaust to be used as the product and directed to the user for humidification of desired area, for example, in the winter, in residential areas.  
           [0027]    The method and apparatus can be used in conjunction with existing desiccant dehumidification systems to cool building fresh makeup air taking advantage of relatively dry and cool building air making a very efficient process. It can also be used to cool dehumidified building recirculation air.  
           [0028]    The plates in the apparatus are made of a layer of wick material with a thin waterproof or low permeability coating in dry zones. Channel guides or corrugated sheets can be used to hold the plates apart and give direction to the working air and product fluids.  
           [0029]    The plate wick is wetted by wicking, or by natural capillary transportation of water out of a reservoir. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0030]    [0030]FIG. 1A is a schematic representation of the flow path of the present invention for the first side of plate.  
         [0031]    [0031]FIG. 1B is the reverse side of the plate in FIG. 1A.  
         [0032]    [0032]FIG. 2A is a schematic representation of the flow path of the present invention for the first side of a version of a plate.  
         [0033]    [0033]FIG. 2B is the reverse side of the plate shown in  2 A.  
         [0034]    [0034]FIG. 3A is a schematic representation of the flow channels on the first side of a plate as depicted in FIG. 2A.  
         [0035]    [0035]FIG. 3B is a schematic representation of a stack of plates.  
         [0036]    [0036]FIG. 4A is a schematic representation of a stack of square shaped plates.  
         [0037]    [0037]FIG. 4B is a schematic representation of a stack of diamond shaped plates.  
         [0038]    [0038]FIG. 5A is a schematic of a plate such as in FIG. 1A with the 4 th  quadrant used as a direct evaporative cooling area.  
         [0039]    [0039]FIG. 5B is a view of the reverse side of plate in  5 A.  
         [0040]    [0040]FIG. 6 is a schematic of a fresh make-up-air drying and cooling system for a conditioned space.  
         [0041]    [0041]FIG. 7 is a schematic of a recirculation air-drying and cooling system for a conditioned space.  
         [0042]    [0042]FIG. 8A is a schematic of an apparatus, wherein a plethora of plates set in a reservoir of water.  
         [0043]    [0043]FIG. 8B is an individual plate from FIG. 8A.  
         [0044]    [0044]FIG. 9 is a schematic of an apparatus, wherein a plethora of plates set in a reservoir of water with an apparatus, wherein an evaporative cooling section is included in the apparatus.  
         [0045]    [0045]FIG. 10 is a schematic of an apparatus, wherein a plethora of plates using corrugated sheets to separate them and wherein an evaporative cooling section is included in the apparatus.  
         [0046]    [0046]FIG. 11 is a schematic of an apparatus, wherein a plethora of plates with a feeder wick water distribution system.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0047]    The following embodiment as exemplified by the drawings is illustrative of the invention and is not intended to limit the invention as encompassed by the claims of the application. Method and apparatus for cooling a product fluid by using ambient air or dehumidified air in an indirect evaporative process that approaches the dew point temperature of the entering working airs absolute humidity. In addition the apparatus can be used to more effectively humidify the air in dry climates than existing humidifiers on the market. As will be appreciated by those persons skilled in the art, several major advantages are provided by the present invention for cooling a product by utilizing a simple, efficient method and apparatus, which has a high efficiency, uses a minimum of energy, consumes a minimum of space and is economical to fabricate.  
         [0048]    [0048]FIG. 1A illustrates one configuration of the top surface of the plate ( 7 ) as used in the apparatus. The plate ( 7 ) is formed by wick material with a portion having a low permeability material surface, such as plastic. The low permeability of the plastic layer prevents moisture from crossing the plate ( 7 ) from one side to the other. The plastic coating, if a separate layer, is thin and is placed onto the wick layer by painting, by lamination or other suitable means.  
         [0049]    As illustrated in FIG. 1A, the top surface of plate ( 7 ) has a portion where the wick material is exposed ( 4 ), and a portion with the plastic layer is exposed ( 3 ). Additionally, the FIG. 1A shows working air channels ( 2 ), product air channels ( 1 ) and channel guides ( 10 ). The wet zone ( 4 ) is exposed wick material. The dry zone ( 3 ) is the wick material with the impermeable surface. FIGS. 1A, 1B,  2 A, and  2 B are segmented into quadrants  51 ,  52 ,  53  and  54 .  
         [0050]    The configuration as shown is a square. It may be of any suitable structural shape. For ease of explanation FIG. 3A shows the overall square dimensions divided in four quadrants No.  51 , 52 , 53 , &amp;  54 . In this FIG. 3A quadrants ( 51 ) is covered by plastic. Quadrant  52  is covered by plastic over one-half of its area. While  53  is of the wick material and is not covered by plastic. Quadrant  54  in this particular embodiment is omitted from the plate ( 7 ).  
         [0051]    There are channel guides ( 10 ), see FIG. 1A, located along the top surface of plate ( 7 ). The channel guides ( 10 ) are in parallel and spaced the desired spacing to accomplish the task of confining and directing the flow of fluids along the surface of plate ( 7 ). The flow space is defined by the adjacent channel guides ( 10 ) and the surfaces of adjacent plates ( 7 ). Where the channel is bounded by plastic layers on the opposing surfaces of adjacent plates, the channel is designated a dry channel, or product channel ( 1 ) in as much as the liquid in the wick layer is prevented from evaporating into the channel fluid. While the channel is bounded by the wick layer of adjacent plates ( 7 ) the channel is designated as a wet channel or working channel ( 4 ) in as much as the liquid in the fiber interacts and evaporates with the fluid or air flowing in the working channel.  
         [0052]    To complete the channel there needs to be a top surface spanning the channel guides. This is provided by the bottom surface of second or next plate in an assembly or stack. As can be seen by looking at FIG. 2A, the dry zone ( 3 ) is in the comparable location to the dry zone on the bottom surface of the first plate ( 7 ). See FIG. 1B and FIG. 2A. Thus the dry zone of the surface of adjoining plates oppose each other across the space defined by those two plates. Thus the dry channel, or product channel ( 1 ), is created and bounded by plastic coated plate sections.  
         [0053]    In the assembly of plates ( 7 ) as shown in FIG. 3B, all odd number plates will be identical. All even number plates will be identical. If we look at a sample plate as FIG. 2A, divided into quadrants as shown in, and farther remove the fourth quadrant as depicted we will have plate  1  of the assembly. The channel guides ( 10 ) are oriented for this layer in the designated position. The next plate in the assembly, plate  2 , also is a square with the fourth quadrant missing but it has its plastic sheet covering the mirror image of that portion covered in the first plate shown in FIG. 2A. When the second plate is stacked onto the first plate, resting on the channel guides, there will be space defining channels.  
         [0054]    For purposes of explaining the working of the assembly, we will designate the channels between the first and second plate as product dry channel  61 ,  62 ,  63  and  64 .  61  and  62  are product dry channels.  63  and  64  are the working air wet channels. In quadrant No.  52  the working air passes over some surface that is plastic coated and some that is not. For channel  63  the majority of the path in the quadrant is over plastic and thus primarily a dry channel. For channel  64  it is primarily over the wick area and thus a wet channel though it has some plastic or dry channel.  
         [0055]    In the assembly as shown in FIG. 3B the plastic coated section of the plate top of the second plate is the mirror image of that portion of the first plate. The channel guides are oriented 90 degrees from the orientation of the channel guides on the first plate. With the addition of a third plate channels  71 ,  72 ,  73  and  74  are formed and defined by the channel guides on the second plate, the top surface of the second plate and the bottom surface of the third plate.  
         [0056]    The flow of the channels in  71 ,  72 ,  73  and  74  are cross flow oriented to the flow in channels  61 ,  62 ,  63  and  64 . The channel guides-for the third plate are oriented in parallel to the channel guides on the first plate. With the addition of a fourth plate on top of the third plate channels  81 ,  82 ,  83  and  84  are formed and defined by the channel guides on the third plate, the top surface of the third plate and the bottom surface of the fourth plate.  
         [0057]    Channels  81  through  84  are flowing parallel to channels  61  through  64  while at the same time being in crossflow orientation to channels  71  through  74 . Using these channel numbers and the orientation as described in FIG. 3A for the quadrants of the plates the interaction and cooling due to the evaporation and particular orientation set forth herein will be discussed and explained.  
         [0058]    For channels  61  and  62  and channels  81  and  82  their flow is entirely in dry channels of the product cooling quadrant  51 . Adjacent to them in the space above plate  2  are the channels  71  and  72 , which are working channels ( 2 ) or wet channels. In quadrant  52  over those portions of channels  71  and  72  that are in the wet area there is an area called the pre-cooling section. Through evaporation of the fluid in the wick like material that are on the floor and ceiling of channels  71  and  72 , when the flow is in the pre-cooling area, or later in the product cooling of quadrant  51 , the temperature of channel surfaces and the fluids will be lowered.  
         [0059]    The fluids in channels  71  and  72  will have temperatures below that of the ambient or starting temperature going into channels  71  and  72  caused by the evaporation in the wet portion of channels  63 ,  64 ,  83  and  84  in quadrant  52 . In turn, channels  63 ,  64 ,  83 , and  84  are precooled by the evaporation in channels  71  and  72  in quadrant  52 . As the flow continues down channels  71  and  72  additional evaporation will occur in quadrant  51  further lowering the temperature of the flow and of the adjacent walls of the channel. Because the wick layer on the adjacent plates are the upper and lower walls of channels  71  and  72  and because this wick layer is moist from the evaporative liquid there is good heat transfer through the plates. The product fluid in channels  61 ,  62 ,  81  ands  82  are then cooled by indirect evaporation.  
         [0060]    The only structure that separates the working channels,  71  and  72 , from the adjacent spaces and their temperatures, is the plastic layer on the top surface of the third plate and bottom surface of the second plate in quadrant  51 . Because this plastic layer is very thin the heat transfer between channels  71  and  72  and the product channels  81  and  82  and  61  and  62  is very high, maintaining a small temperature difference across the plates. Thus the temperature in channels  61  and  62  in the first space layer and channels  81  and  82  in the third space layer are lowered due to the low-temperature in channels  71  and  72  brought about by evaporation and pre-cooling. Thus the product flow of fluid entering channels  61  and  62  and channels  81  and  82  has its temperature lowered during its passage through the channels. Product exits into what had been the fourth quadrant and are thus and then directed for the desired use of the product fluid or air.  
         [0061]    The product fluid or air in the second space contained in channels  73  and  74  are likewise cooled across the plastic barrier by the working air channels of  63  and  64  and  83  and  84  in the adjacent channel layer&#39;s in the stack as illustrated.  
         [0062]    Within quadrant  52 , because there is pre-cooling of working fluid in channels  63 ,  64 ,  71 ,  72 ,  83  and  84  there will be additional cooling in the spaces between the plates  1 , 2 , 3  and  4 . In channel  71  the first quarter of the flow is over plastic and thus is a dry channel. There is no evaporation occurring in this section. For the remainder of channels  71  in quadrant  52  there is evaporation and thus cooling of the flow and of the adjacent walls. This cooling by channel  71  through heat transfer across the second and third plates that border channel  71  in channels  63  and  64  above the first plates space and in channels  83  and  84  above the third plates space precools the air. This cooling due to channel  71  occurs in the early part of the flow in  63 ,  64 ,  83  and  84 . Thus the flow in these four channels is precooled, without adding humidity, before it commences to be cooled by evaporation within its own channel.  
         [0063]    Similar pre-cooling occurs in channel  71  however channel  72  has more cooling because there is more plastic covering channel  72  in quadrant  52 . The flow in channel  72  is precooled by the flow occurring in  63 ,  64 ,  83  and  84 . Because there is more plastic in channel  72  there is more pre-cooling from these adjacent channels.  
         [0064]    The pre-cooling occurring in quadrant  52  lowers the temperatures of all the working air before entering the product cooling section in quadrant  51  and  53 .  
         [0065]    The embodiments as shown in FIGS. 1, 2,  3  and  4 A are of a square configuration of plates ( 7 ). There are alternatives, among them a diamond shape such as shown in FIG. 4B. The selection of a square shape or diamond shape would be determined by the design decisions as further explained.  
         [0066]    A diamond shape has the advantages of having the working fluid flowing relative to the product fluid at an angle other that ninety degrees. Rather than being oriented at right angles to the adjoining fluid flow it is more of an obtuse angle. The flow is more counter flow than cross flow. As the angle of orientation moves beyond 90 degrees the area of interaction of the product flow and the working fluid in the adjoining layer increases. Thus the working fluid while becoming cooler through evaporation has more time to interact with the product fluid. The product fluid is given more time to cool by heat transfer.  
         [0067]    At the end of the working air channel the working air temperature is lower due to its longer exposure to the evaporative surface in the wet zone. In the diamond shape, there is a greater proportion of the area of the plate ( 7 ) on the perimeter, in as much as the square shape has more interior area. Thus the diamond shape gives proportionately more area on the perimeter, area that is cooler due to the ends of the working air channels are at the perimeter. In any heat transfer surface, the amount of area and the differential temperatures in these areas (all other things being equal) will affect the amount of heat transfer that will occur. In the diamond shape the coolest part of the working fluid is at the perimeter, and inasmuch as the diamond gives more area at the perimeter, the diamond gives more proportion of its area to heat transfer where the temperature of the working flow is the coolest. Thus the diamond shape gets greater heat transfer because of the distribution of the area in the diamond puts more of the coolest area at the perimeter, where the product fluid has the largest amount of area to interact with it. Thus there will be more area for heat exchange for the two flows and thus to have the sensible heat transfer across the plastic surface ( 3 ).  
         [0068]    An additional feature of the diamond shape that accentuates the heat transfer more than what occurs in the square shape, is the counterflow. Flows being more counter flow than cross flow, the gradient of temperature as it decreases along the working air ( 2 ) channel, puts the lowest part of the temperature in the working channel, across the heat transfer surface from the product air ( 1 ). Thus the heat differential is greatest and the heat transfer will be the greatest. Though this same effect will occur in square shapes, the square having more interior area does not get the same quantity of heat transfer.  
         [0069]    Another advantage of a diamond shape when used in an upright orientation (See FIGS. 8A and 8B) is the advantage of lower vertical distance for plates when the diamond is oriented with its long axis horizontal to the ground. If the plates ( 7 ) in their assembled state are vertical or at an angle of orientation or slope the lower edge may be immersed in a reservoir of evaporating fluid. The wicking function of the wick layer transports the evaporating fluid from the reservoir upward to the upper reaches of the wick layer. If the plates shape is a diamond shape this vertical height that must be wicked in order to wet the upper reaches of the wick layer will be lower. The wicking can occur over longer distances, more efficiently, the more horizontal the plates are.  
         [0070]    The advantages of a square shaped plate is in its compactness. As discussed previously, a square, over a diamond, creates the smallest footprint. More of the area is in the interior. The square shape then is best where compactness is essential.  
         [0071]    In addition to the shape, the omission of the 4 th  quadrant( 54 ) as shown in FIG. 3A has advantages. By removing the 4 th  quadrant a reduced pressure drop for the fluid flow for the product air ( 1 ) is achieved. The product air is cooled by the adjacent working air ( 2 ). The 4 th  quadrant would merely place adjacent layers of product air (presumable at the same temperature) next to each other. No gain in the product temperature is had. By omitting the 4 th  quadrant less energy is expended in the passage of the product through these areas of the product channels, as the restricted channel is shorter.  
         [0072]    An alternative design decisions may dictate that quadrant  4  ( 54 ) not be omitted but rather kept as an evaporative area for the product flow, see FIG. 5A. This added area of direct evaporative cooling for the product air ( 1 ) that is previously came through the product air channels ( 3 ) will give these advantages: there will be added cooling to the product air and some degree of humidity will be added to the product air. The addition of direct evaporation cooling may be necessary in some applications to lower the temperature.  
         [0073]    In some environments the main feature or function of the within design may be to add humidity. This can be accomplished by the apparatus as shown in FIG. 3A by making use of the exhaust product which has increased humidity over typical evaporative humidifiers. Additionally the use of direct evaporative channels after the product channel can be used to add humidity to the product air such as in FIG. 5A.  
         [0074]    The exact mix of humidity to add to the product air can be altered by design decisions of the amount of direct evaporative cooling added to the product channel or by mixing the exhaust working air in some proportion with the dry cooler product air by use of baffles or other means.  
         [0075]    In addition the ability to add humidity and at the same time control the temperature of the end product mixture enables the user to adjust humidity and temperature independently to accomplish the target conditions. This apparatus allows the user to adjust the humidity without having to also adjust the temperature by an outside heat source in conditions where higher humidity is desired but not lower temperature.  
         [0076]    The apparatus by an additional feature can manipulate the latent heat capacity of the working fluid to accomplish a more efficient cooler. By adding heat to the working air ( 2 ), additional latent heat capacity of the working air and additional evaporation capacity results to the system. If the working air has humidity above 0.0011 to 0.0014 pounds of water per pound of air (wherein the variation is dependent upon the elevation above sea level) the adding of heat to the working air will aid in the heat transfer mechanism. Above this level of humidity the addition of sensible heat causes a much greater increase in the latent heat capacity of air. This is a benefit to the cooling process. This added latent heat capability gives the working air greater capacity, which in turn gives the system greater capacity to cool down the temperature through the evaporative process.  
         [0077]    The flow of fluids, working air ( 2 ) or product air ( 1 ), can be aided by common mass transfer devices such as fans pumps or other devices common in industry. To aid in the efficiency of the system and its design the indirect evaporative cooler is enhanced if the working air ( 2 ) has a pressure drop at its exhaust which induces the flow of the working air through the working air channels ( 17 ). By producing a negative pressure differential across the working air channel the evaporative process in the working air channel will be enhanced as lower pressure aids evaporation.  
         [0078]    Desiccants can also be used in the system as shown in FIGS. 6 and 7. The benefits to the indirect evaporative cooler are in enhanced efficiencies of the evaporative process, control of the humidity of the working or product air, and the use of the by product of the heat generated during dehumidification to increase the latent heat capacity of the working air in the evaporative process In viewing FIGS. 6 and 7 the desiccants wheel is illustrated ( 13 ). In FIG. 6 outside air is first drawn through and dehumidified by the desiccant wheel. The dehumidification raises the temperature of the dehumidified air due to the heat occurring by extracting the water from the outside air. In FIG. 6 the dehumidified air is used as the product air, in order to control the humidity and yield cool dry air as product ( 1 ). In FIG. 6 the working air is recirculated air from the condition space ( 12 ) which is already dry and thus a larger capacity for the evaporative process for the cooling.  
         [0079]    As shown in FIG. 7 the air from the conditioned space is recirculated. In this embodiment the recirculated air is used for both the product air and the working air. After recycling, the working air is exhausted and thus there is a net loss of air for circulation. To make up for this loss, outside air is used to supplement the system air. Before use the outside air may have to be dehumidified. After going through the desiccant wheel and becoming dehumidified this combination air is fed into both the product ( 16 ) and working ( 17 ) channels. The exhaust of the working channel ( 17 ) is exhausted to the outside and the product channels ( 16 ) in sent to the conditioned space ( 12 ).  
         [0080]    The dissipate of the desiccant system usually requires the use of the heat exchanger system to redirect or dissipate the heat caused by the dehumidification step. However in the subject design the heat generated by the dehumidifier is used to enhance the evaporative process by going to the working air stream. Thus rather than having to remove heat from this dehumidified air the heat gives added efficiency and capacity to the system.  
         [0081]    The system of wetting the wick material in the plates ( 7 ) by evaporating fluid can be accomplished by pure wicking from a low point of the wick material immersed in a reservoir or by distributing the evaporating fluid by means of feeder wick that is positioned and interface with the wick material on the plates. FIG. 11 illustrates a feeder wick where evaporating fluids are distributed by way of hoses or tubes to the desired location. From the tube the evaporating fluid enters the feeder wick which fits in a hole in the plates. The outer edge of the wick material on the feeder wick interfaces with the inside surface of the holes in the plates and the wicking layer on the plates. The evaporating fluid fed by way of the tube to the feeder wick and then exits the tube through porous openings or holes into the feeder wick material. This feeder system prevents the pooling of liquid which can inhibit the evaporation process due to surface tension of fluids. Additionally the wicking methods do not require as much energy to transport the fluid. Thus energy cost will be saved.  
         [0082]    [0082]FIGS. 8A, 8B, and  9  illustrate the reservoir system where the plates are vertical or in a sloped position with their lower edge immersed in the reservoir holding the evaporating fluids. As the evaporation takes fluids from the wick material the wicking from the reservoir replenishes that liquid for subsequent evaporation. In order to aid in the wicking the plates cannot be overly tall.  
         [0083]    This may be addressed by the use of a diamond shape as previously discussed rather than a square shape. Alternately the plates may be elevated at an angle rather than vertical. This minimizes the amount of gravity that must be overcome to wet the uppermost area of the wick material.  
         [0084]    [0084]FIG. 10 illustrates an assembly where the individual plates (without the separate channel guides ( 10 ) are separated by corrugated inserts. These inserts maintain the separation and also act as the channel guides for the flow of product air and workign air. The inserts are preferred to be of an impermeable material such as plastic or resin impregnated cellulose or paper so that in the wet channel the purportrating liquid won&#39;t be in the inserts.