Abstract:
The flexible belt evaporator employs an endless woven textile belt serving as a carrier for saline or otherwise contaminated water for evaporation of the water therefrom, and also serves as the evaporator surface. Mechanical equipment immersed in the saltwater and corresponding maintenance difficulties are largely avoided by placing most or all belt rollers clear of the liquid water tank of the system. Saltwater or contaminated water is sprayed onto the belt from above. The continuing passage of the belt about the exposed rollers results in water evaporation from the belt. Scale and residue buildup on the belt is removed by passing the belt through a wash tank. The wash tank preferably contains an ultrasonic generator to produce ultrasonic energy for removal of residue from the textile belt. The flexible belt evaporator system may be applied to evaporative cooling systems, humidifying systems, and salt or residue recovery systems.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to water evaporation systems, and particularly to a flexible belt evaporator for cooling and humidifying closed areas and for the desalination of water. 
     2. Description of the Related Art 
     Water evaporation systems are well known for various purposes, e.g., removing seawater to recover salt and/or other minerals, cooling due to the heat absorption of evaporating water, and humidifying air. Accordingly, a number of different water evaporation devices, systems, and methods of operation have been developed in the past. 
     A general class of such systems comprises the spreading of a relatively thin film or layer of water on a sheet of material so that the relatively large surface area per volume of water provides reasonably efficient evaporation. The problem with this principle of operation is that salt or other contaminants or impurities in the water will rapidly coat the sheet of material once the water evaporates. Some means must be provided for removal of the salt and/or other residue from the evaporation sheet or substrate material, at least from time to time. The more efficient the evaporative process, the more rapidly the salt and/or other residue builds upon the evaporative base material. Some method for preventing salt from accumulating on the evaporator would increase the efficiency and extend the life of the device. 
     Thus, a flexible belt evaporator solving the aforementioned problems is desired. 
     SUMMARY OF THE INVENTION 
     The flexible belt evaporator has an endless water absorbent textile belt or web that is continually advanced over and around a plurality of rollers. The textile material is preferably formed with hydrophilic weft or woof strands or threads disposed generally horizontally, i.e., across the width of the web, and hydrophobic warp strands or threads disposed vertically, i.e., in the direction of travel of the web. This limits or obviates water absorption along the vertical strands, thus slowing any dripping that might otherwise occur from an overly saturated belt or web. 
     Most, or all, of the rollers are located clear of any liquid water. The water that is contaminated with salt and/or other materials is sprayed onto the textile belt from above as the belt passes over a series of upper rollers. Evaporation takes place as the textile belt or web is advanced over and about the rollers. The salt and/or other residue remains on the belt. The belt is then passed through a wash tank, where the salt and/or other residue is washed or otherwise cleaned from the belt. The wash tank preferably includes an ultrasonic generator using ultrasonic energy to better remove the salt and/or other residue from the textile belt or web. The belt then passes from the wash tank to continue its endless path about the rollers, where it is again wetted by the overhead spray nozzles. 
     In one embodiment, belt tension is maintained by one or more rollers immersed in the lower portion of the wash tank. In another embodiment, the belt passes loosely through the wash tank, and no rollers are installed in the tank. Belt tension exterior to the wash tank is maintained by pinch rollers adjacent to the wash tank. This embodiment avoids the need for installation of rollers in the salt contaminated wash tank, and the corresponding difficulties in maintenance of the rollers in such an environment. The evaporative system may be applied to cooling systems, humidifying systems, and salt and/or contaminant recovery systems for water. 
     These and other features of the present invention will become readily apparent upon further review of the following specification and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic elevation view of a first embodiment of a flexible belt evaporator according to the present invention, having rollers disposed within the wash tank. 
         FIG. 2  is a diagrammatic elevation view of a second embodiment of a flexible belt evaporator according to the present invention, having no rollers installed within the wash tank. 
         FIG. 3  is a diagrammatic elevation view of a third embodiment of a flexible belt evaporator according to the present invention, having a large number of closely spaced rollers. 
         FIG. 4  is a partial perspective view of a woven textile incorporating mutually orthogonal hydrophilic and hydrophobic strands in its weave for use as the belt in a flexible belt evaporator according to the present invention. 
         FIG. 5  is a flowchart illustrating the flow paths of water and air in a solar-heated heat exchanger and desalination system. 
         FIG. 6  is a flowchart illustrating the flow paths of water and air in a solar-powered evaporative cooling system. 
     
    
    
     Similar reference characters denote corresponding features consistently throughout the attached drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The flexible belt evaporator has an endless flexible woven textile belt or web that passes about a series of rollers. A spray system is provided above the rollers to wet the belt with salt water or water containing other impurities. The belt is exposed to the air between the rollers to evaporate water from the belt. A wash bath is provided to rinse the salt and/or other impurities from the belt. The apparatus may be used to cool the surrounding air by means of the heat absorbed by the evaporating water, to humidify air as the water evaporates from the belt, and/or to collect salt and/or other residue from the belt after the water evaporates therefrom. 
       FIG. 1  of the drawings is a diagrammatic drawing of a first embodiment  110  of the flexible belt evaporator. The evaporator  110  includes a plurality of closely spaced upper guide rollers  112   a ,  112   b ,  112   c ,  112   d , and  112   e , and a plurality of closely spaced lower guide rollers  114   a ,  114   b ,  114   c ,  114   d , and  114   e . It will be seen that more or fewer upper and lower guide rollers may be provided. The guide rollers  112   a  through  114   e , and other rollers employed with the evaporator  110 , may have their rotational axes sloped slightly from the horizontal to encourage water runoff toward one end thereof, if desired. The upper guide rollers  112   a  through  112   e  are separated vertically from the lower rollers  114   a  through  114   e  by a clear span that is greater than the span between adjacent rollers, through which air may be circulated for evaporation. This configuration provides a very compact horizontal area for the flexible belt evaporator  110  in comparison to the overall evaporative area of the belt  118 , as most of the area of the belt  118  is oriented generally vertically between the alternating upper and lower rollers. First and second master rollers  116   a  and  116   b  are disposed above the upper guide rollers  112   a  through  112   e . One of the rollers, e.g., the first master roller  116   a , may be motorized, as is conventional in the art of conveyor belts and the like. 
     An endless, water-absorbent, flexible woven fabric belt  118  travels a sinusoidal path about the guide rollers  112   a  through  114   e . The belt  118  passes about the first lower guide roller  114   a , then up and over the first upper guide roller  112   a , back down to the second lower guide roller  114   b , and continues in sequence about guide rollers  112   b ,  114   c ,  112   c ,  114   d ,  112   d ,  114   e , and  112   e . A wash bath or tank  120  is provided adjacent to the last guide rollers  112   e  and  114   e , to wash salt and/or other residue from the belt  118  after saltwater or other contaminated water evaporates from the belt. The belt  118  forms a loop portion  122  that passes through the wash bath or tank  120 . The belt  118  is guided into the wash bath  120  by an entrance roller  124   a , and is guided from the wash bath  120  and back to the second master roller  116   b  by a wash bath exit roller  124   b . While the return path for the belt  118  is shown extending over the two master rollers  116   a  and  116   b  and above the upper rollers  112   a  through  112   e , it will be seen that the belt return path may extend beneath the lower rollers  114   a  through  114   e  and beneath the wash bath  120  by providing rollers in appropriate locations. One or more wash bath rollers, e.g., first and second wash bath rollers  126   a  and  126   b , are installed within the wash tank  120  to maintain tension on the endless belt  118  as it travels about the rollers  112   a  through  116   b  and the wash bath entrance and exit rollers  124   a  and  124   b.    
     A water dispenser  128  is disposed above the upper rollers  112   a  through  112   d  or  112   e , generally between the two master rollers  116   a  and  116   b . The water dispenser  128  preferably comprises a plurality of spray nozzles  130   a  through  130   d , oriented to spray saltwater or water containing other contaminants onto the belt  118  as it passes over and around the upper guide rollers  112   a  through  112   e . More or fewer spray nozzles may be provided, the drawing being exemplary. The woven fabric of the belt  118  absorbs the saltwater (saline) or otherwise contaminated water from the spray nozzles  130   a  through  130   d  and travels around the various upper and lower rollers to expose the wet belt surface to the air for evaporation. Individual drip catch trays or a single large drip catch pan may be placed beneath the lower rollers  114   a  through  114   e . Any collected salt and/or other residue remains on the belt. The belt  118  continues its travel around the rollers  112   a  through  114   e , eventually reaching the wash bath  120  via the entrance roller  124   a . The loop portion  122  of the belt  118  is immersed in the wash bath  120  so that the salt and/or other residue is washed from the belt  118 . An ultrasonic device  132  may be installed within the wash bath  120  to remove fine particulates from the belt  118  ultrasonically. Also, chemicals may be provided in the wash bath  120  for further cleaning of the belt  118 . After passing through the wash bath  120 , that portion of the endless belt  118  continues its travel back across the master rollers  116   a ,  116   b  to travel through the upper and lower rollers  112   a  through  114   e  in order to be wetted once again for further evaporation. 
       FIG. 2  of the drawings is a diagrammatic illustration of an alternative embodiment of the flexible belt evaporator, designated as flexible belt evaporator  210 . The flexible belt evaporator  210  of  FIG. 2  includes most of the components of the flexible belt evaporator  110  of  FIG. 1 , i.e., upper and lower guide rollers  112   a  through  114   e , master rollers  116   a  and  116   b , belt  118 , wash bath  120 , the belt loop  122  immersed in the wash bath  120  (the loop is flaccid, in the embodiment of  FIG. 2 ), the water dispenser  128  and spray nozzles  130   a  through  130   d , and the ultrasonic device  132 . These like numbered components are essentially identical in the two embodiments  110  of  FIGS. 1 and 210  of  FIG. 2 . However, it will be noted that there are no rollers immersed within the wash bath  120  in the flexible belt evaporator  210  of  FIG. 2 . This results in the belt loop  122  being loosely suspended within the wash bath tank  120  in the embodiment of  FIG. 2 . The remainder of the belt  118  is kept taut by a first or entrance pair of pinch rollers  224   a  and  224   b , and a second or exit pair of pinch rollers  226   a  and  226   b . These pinch rollers  224   a  through  226   b  are roughly analogous to the entrance and exit rollers  124   a  and  124   b  of the embodiment  110  of  FIG. 1 , but two rollers at each location are required to grip or pinch the belt  118  therebetween in order to prevent the slack in the loop  122  from spreading about the remainder of the endless belt as it passes over and around the rest of the roller system. The flexible belt evaporator  210  of  FIG. 2  avoids the need for any rollers within the water of the wash bath  120 , thus avoiding the problems of operation and maintenance of a moving mechanical device within a corrosive liquid, i.e., the salty or otherwise contaminated water that collects in the wash bath  120 . 
       FIG. 3  provides a diagrammatic illustration of another embodiment of the evaporator, designated as flexible belt evaporator  310 . The configuration of the flexible belt evaporator  310  is similar to that of the evaporator  110  of  FIG. 1 , but includes a much greater number of upper and lower guide rollers. These guide rollers are designated as upper guide rollers  312   a  through  3121  and lower guide rollers  314   a  through  314   l . They differ from their corresponding rollers  112   a  through  112   e  and  114   a  through  114   e  of the embodiments  110  of  FIGS. 1 and 210  of  FIG. 2  in that the diameters of the rollers  312   a  through  3141  are considerably smaller than the diameters of the rollers  112   a  through  114   e . Advantageous placement of the smaller diameter rollers  312   a  through  3141  to one another may be made, even though their bases and bearings may be essentially the same diameter as the diameters of the rollers  112   a  through  114   e , by staggering the alternating rollers of each set relative to one another. Thus, the first upper roller  312   a  is offset vertically slightly below the second upper roller  312   b , the second upper roller  312   b  is slightly higher than the third upper roller  312   c , etc. This places every other upper roller  312   a ,  312   c ,  312   e ,  312   g ,  312   i , and  312   k  in a horizontal row below a horizontal row containing the other upper rollers  312   b ,  312   d ,  312   f ,  312   h ,  312   j , and  312   l . The lower rollers are arranged similarly, so that the lower rollers  314   a ,  314   c ,  314   e ,  314   g ,  314   i , and  314   k  are aligned in a horizontal row slightly above another horizontal row containing lower rollers  314   b ,  314   d ,  314   f ,  314   h ,  314   j , and  314   l . This configuration allows a much larger vertical evaporative surface area for the belt  118  as it passes back and forth between the much greater number of rollers. The remaining components  116  through  132  of the embodiment  310  of  FIG. 3  are substantially identical to those like designated components in the embodiment  110  of  FIG. 1  and operate in the same manner. 
     The provision of relatively large diameter bearings is desirable in order to reduce the rolling friction of the various rollers. This friction can be substantial when a large number of rollers is considered. It will be seen that by staggering the adjacent rollers in each of the upper and lower sets or rows, the bases and/or bearings of each roller may be larger than would otherwise be the case, and/or the rollers may be placed closer to one another than in a linear array of rollers in order to increase the density of the flexible belt and the evaporative surface area as the belt runs among the closely spaced rollers. In fact, the diameters of the bearings and their bases in the configuration of  FIG. 3  may be a few times larger (e.g., 2-4 times larger) than the diameters of the rollers because the rollers and their bearings are staggered in the manner illustrated in  FIG. 3 . The two upper and lower rows of rollers illustrated in  FIG. 3  are exemplary, and are not intended to be limiting. Even larger bearings may be used by configuring the system to have three or more upper and lower rows of rollers, as desired. 
       FIG. 4  is a perspective view of a portion of the absorbent, flexible woven fabric belt  118  used in the various embodiments of the flexible belt evaporator. The belt or web  118  is preferably formed with the warp strands or threads  118   a , i.e., those strands extending vertically between the upper guide rollers and the lower guide rollers, being hydrophobic or water-repellent. The weft or woof strands or threads  118   b , i.e., those strands extending parallel to the rotary axes of the rollers, are hydrophilic or water-absorbent. A belt or web  118  manufactured in this manner will have the horizontal or weft strands  118   b  absorbing water as the water is repelled from the vertical or warp strands  118   a , thus greatly reducing vertical runoff along the belt or web  118  as it extends vertically between upper and lower rollers. 
       FIG. 5  is a schematic diagram or flowchart illustrating the components of an evaporative cooling and desalination system incorporating the flexible belt evaporator of the present invention. The evaporator of  FIG. 5  is designated as  510 , but it will be understood that it may comprise any of the flexible belt evaporators  110 ,  210 , or  310  respectively of  FIG. 1 ,  2 , or  3 , and/or any of the variations thereof described further above. In  FIG. 5 , solar energy is applied to a solar-powered liquid heater  512 . The heated fluid is used to heat seawater or other contaminated water in a water heater  514 . The heated seawater (or other water) then passes to the flexible belt evaporator  510 , where the heat assists in the evaporative process. The heat absorption accomplished by the water as it evaporates in the flexible belt evaporator  510  results in a cooling of the air (or other gas) in which the water vapor is suspended. The high humidity air or gas is then passed to a condenser  516 , and the condensed water is returned to the water heater  514  to repeat the cycle. Additional water may be added as necessary, but the water cycling is essentially a closed system. The evaporative cooling and desalination system of  FIG. 5  requires no net energy input, other than the solar energy used to heat a fluid that is, in turn, used to heat the saline water circulating in the system. 
       FIG. 6  is a schematic flowchart of an air conditioning system using a flexible belt evaporator  610  according to the present invention. As in the case of the flexible belt evaporator  510  of  FIG. 5 , the evaporator  610  may comprise any of the embodiments of the flexible belt evaporator described herein. As in the ease of the system of  FIG. 5 , the system of  FIG. 6  initially uses a solar heater  612  to heat a fluid. The hot fluid is used to heat a moisture-absorbent (desiccant) material  614 , driving any absorbed moisture therefrom. The desiccant  614  receives warm and moist air from the flexible belt evaporator  610  after the water input has been evaporated therein. As the evaporative process removes heat from the air, the cooled and moist air is used as a heat exchanger to accept waste heat output from an air conditioning system (air conditioning heat load). Other than the energy required to run any required circulation fans or pumps in the system, the air conditioning system of  FIG. 6  requires no additional energy, other than the solar input to the solar heater  612 , resulting in a very energy efficient system. 
     It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.