Method of wetting evaporative cooler media through a permeable layer

BACKGROUND OF THE INVENTION

p-00021. Field of the Invention

p-0003The present invention relates generally to a method and apparatus concerning the operation of evaporative cooling systems and, in particular, to a method and apparatus concerning the effective wetting by a liquid coolant of an evaporative pad of an evaporative cooling system that cools air supplied to a gas turbine system.

p-00042. Discussion of the Prior Art

p-0005Evaporative cooling systems, or evaporative coolers as such systems are typically referred to, are employed in various ways in residential, commercial and industrial contexts. In one example, the evaporative coolers cool air that is directed through the evaporative coolers. The evaporative coolers cool the air through the evaporation of a coolant, typically water, which is brought into contact with the air at the evaporative coolers.

p-0006Typically, an evaporative cooler includes an evaporative pad at which the air directed to the evaporative cooler is cooled. A coolant, such as water for example, is caused to flow through the evaporative pad and air is brought into contact with the coolant at the pad, usually by means of a fan, blower or turbine drawing or forcing the air through the pad. The evaporative pad typically is constructed of a material that has a large surface area over which the coolant is dispersed so that the coolant assumes a large surface area at the evaporative pad, thereby facilitating the evaporation of the coolant at the pad. Heat transfer takes place between the air and the dispersed coolant, as the air comes into contact with the coolant at the evaporative pad, and the coolant thereby evaporated, causing the air to cool and the density of the air to increase. Coolant is continuously delivered to the evaporative pad to replace the coolant that evaporates.

p-0007Evaporative coolers are known to be employed for the purpose of cooling the living spaces of residential structures and the working environments of commercial and industrial buildings for thermal comfort for example. In addition, evaporative coolers are known to be applied in industrial processes in which a supply of cooler and denser air can be used to advantage. For example, an evaporative cooler can be employed in conjunction with a gas turbine system wherein the cooled air from the evaporative cooler is compressed and the compressed air mixed with a fuel such as natural gas for example. The mixture of air and fuel is combusted and the resulting expanding gases are directed to a turbine so as to drive the turbine that, in turn, drives an electrical generator for producing electrical power for example. The cooled air, because of its increased density, provides a higher mass flow rate and pressure ratio at the gas turbine equipment, resulting in an increase in turbine output and efficiency.

p-0008The foregoing benefit, however, may not be fully realized in those instances in which the evaporative pad is not completely wetted by the coolant so that the air passing through the pad is cooled to a lesser extent than would be the case in which the pad is essentially entirely wetted by the coolant. Additionally, the areas of the evaporative pad that are not wetted by the coolant can result in the establishment of temperatures in the air that passes through these non-wetted areas that are warmer than the temperatures in the air that has come into contact with the coolant in areas of the evaporative pad that have been wetted by the liquid coolant. These temperature differences in the respective air masses that are then directed to the turbine compressor can cause air turbulence that can result in damage to the turbine equipment. Even in the absence such damage, the vibration of the turbine blades can result in the deteriorated performance of the turbine equipment.

BRIEF DESCRIPTION OF THE INVENTION

p-0009The following sets forth a simplified summary of examples of the present invention for the purpose of providing a basic understanding of selected aspects of the invention. The summary does not constitute an extensive overview of all the aspects or embodiments of the invention. Neither is the summary intended to identify critical aspects or delineate the scope of the invention. The sole purpose of the summary is to present selected aspects of the invention in a simplified form as an introduction to the more detailed description of the embodiments of the invention that follows the summary.

p-0010In accordance with one aspect, the present invention provides an evaporative cooler that includes an evaporative pad including a liquid coolant-receiving surface at which a liquid coolant distributed to the evaporative pad is received and thereafter passes into the evaporative pad. The evaporative cooler also includes a liquid coolant distribution container that includes an upper portion configured to hold liquid coolant and a lower portion contiguous with the upper portion. The lower portion includes an opening and a permeable bed in place over the opening through which the liquid coolant held in the upper portion of the liquid coolant distribution container passes and is distributed to the liquid coolant-receiving surface of the evaporative pad.

p-0011In accordance with another aspect, the present invention provides a method of cooling air. The method includes passing a liquid coolant into an evaporative pad. The pad includes a liquid coolant-receiving surface at which a liquid coolant distributed to the evaporative pad is received and thereafter passes into the evaporative pad. The evaporative pad is of an evaporative cooler and the passage of liquid coolant is from a liquid coolant distribution container. The liquid coolant distribution container includes an upper portion configured to hold liquid coolant and a lower portion contiguous with the upper portion. The lower portion includes an opening and a permeable bed in place over the opening through which the liquid coolant held in the upper portion of the liquid coolant distribution container passes and is distributed to the liquid coolant-receiving surface of the evaporative pad. The method includes wetting essentially the entirety of the evaporative pad with the liquid coolant passing into the evaporative pad. The method includes passing the air through the essentially entirely wetted evaporative pad. The method includes contacting essentially the entirety of the air with the coolant at the essentially entirely wetted evaporative pad, whereby essentially the entirety of the air passing through the essentially entirely wetted evaporative pad is cooled.

BRIEF DESCRIPTION OF THE DRAWINGS

p-0012The foregoing and other aspects of the present invention will be apparent to those skilled in the art to which the present invention relates from the detailed descriptions of examples of aspects and embodiments of the invention that follow with reference to the accompanying drawings, wherein the same reference numerals are used in the several figures to refer to the same parts or elements and in which:

p-0013<figref idrefs="DRAWINGS">FIG. 1</figref> is a schematic side elevational view of an example of an evaporative cooling system, or evaporative cooler, incorporated in an air-conditioning system that supplies cooled air to a gas turbine system;

p-0014<figref idrefs="DRAWINGS">FIG. 2</figref> is a schematic perspective view of an example of a liquid coolant distribution container for distributing liquid coolant to an evaporative pad of an evaporative cooler such as the evaporative cooler referred to with respect to <figref idrefs="DRAWINGS">FIG. 1</figref>; and

p-0015<figref idrefs="DRAWINGS">FIG. 3</figref> is a schematic cross-sectional view of the liquid coolant distribution container of <figref idrefs="DRAWINGS">FIG. 2</figref>.

DETAILED DESCRIPTION OF THE INVENTION

p-0016Examples of embodiments that incorporate one or more aspects of the present invention are described below with references, in certain respects, to the accompanying drawings. These examples are not intended to be limitations on the present invention. Thus, for example, in some instances, one or more examples of the present invention described with reference to one aspect or embodiment can be utilized in other aspects and embodiments. In addition, certain terminology is used herein for convenience only and is not to be taken as limiting the present invention.

p-0017<figref idrefs="DRAWINGS">FIG. 1</figref> schematically illustrates an example embodiment of the invention wherein an evaporative cooling system, or evaporative cooler, indicated generally at <b>10</b>, is included as a component of an air-conditioning system, indicated generally at <b>40</b>. The air-conditioning system, including the evaporative cooler <b>10</b>, is operably associated with a gas turbine system, indicated generally at <b>50</b>, to which air exiting the evaporative cooler <b>10</b> is directed to the gas turbine system.

p-0018A compressor <b>52</b> at the gas turbine system <b>50</b> functions to draw ambient air into the air inlet <b>41</b> of the air-conditioning system <b>40</b> and through the air-conditioning system. After being suitably conditioned at the air-conditioning system <b>40</b>, the air streams through the adapter duct <b>44</b> (sometimes referred to as a transition duct or bellmouth) to the compressor <b>52</b>. The conditioned air, upon entering the compressor <b>52</b>, is compressed to relatively high pressures. Thereafter, the compressed air enters a combustion area <b>54</b> where the compressed air is mixed with a fuel such as natural gas, for example, and the mixture is burned to produce high-pressure, high-velocity gases that are the product of the combustion that takes place in the combustion area <b>54</b>. The high-pressure, high-velocity gases proceed to a turbine <b>55</b> possessed with considerable energy and drive the blades of the turbine that are attached to an output shaft <b>56</b>. The rotation of the turbine blades causes the output shaft <b>56</b> which is attached to rotate as well, and the energy of the output shaft <b>56</b> as it rotates is delivered to a generator <b>58</b> and electrical energy thereby produced at the generator as will be understood by those having ordinary skill in the art. The use of gas turbine systems is not limited to electrical power generation, however, and the turbine systems also can be applied, for example, to driving pumps and compressors.

p-0019For optimum plant operation, air from the ambient environment is used at the gas turbine system <b>50</b>. The ambient air may first be conditioned and that is accomplished at the air-conditioning system <b>40</b>. Again referring to <figref idrefs="DRAWINGS">FIG. 1</figref>, as noted above, ambient air, under the influence of the compressor <b>52</b>, is drawn into the air-conditioning system at air inlet <b>41</b>. The ambient air first enters a filter chamber <b>42</b> where particulate matter, including in some cases water droplets, is removed from the ambient air. Thereafter, the filtered air passes through the evaporative cooler <b>10</b>, the operation of which is discussed in greater detail below. However, it is noted here that the evaporative cooler functions to cool the filtered air and increases its density; and, as noted above, the denser air provides a higher mass flow rate and pressure ratio at the gas turbine system <b>50</b>, resulting in an increase in turbine output and efficiency.

p-0020The filtered and cooled air that exits the evaporative cooler <b>10</b> flows to demisters <b>43</b> which remove unwanted water from the air. From the demisters, the air flows into the adapter duct <b>44</b> and from the adapter duct the conditioned air flows to the gas turbine system <b>50</b> where the conditioned air after being compressed is mixed with fuel and burned as described above. The arrows in <figref idrefs="DRAWINGS">FIG. 1</figref> are all indicative of the flow of the air from its entry into the air-conditioning system <b>40</b> at the air inlet <b>41</b> to the delivery of the air at the compressor <b>52</b> of the gas turbine system <b>50</b>.

p-0021The evaporative cooler <b>10</b> itself includes an evaporative pad, indicated generally at <b>12</b> in <figref idrefs="DRAWINGS">FIG. 2</figref>, that includes an air-entry surface <b>14</b> at which air delivered to the evaporative pad from the filter chamber <b>42</b> enters and passes through the evaporative pad. The evaporative pad <b>12</b> also includes an air-exiting surface <b>16</b> at which air passing through the evaporative pad, and cooled at the pad, exits from the evaporative pad. The evaporative pad <b>12</b> further includes a liquid coolant-receiving surface <b>18</b> at which a liquid coolant distributed to the evaporator pad is received and thereafter passes into the evaporative pad. Although various types of liquid coolants can be employed with evaporative coolers, in the example illustrated in the drawings water, either treated or untreated, or an aqueous solution can be used as the liquid coolant. Untreated water can include raw water taken from the environment or water that has been treated only for the purpose of making it potable. Treated water would include water that has been treated in order to render it more suitable for application to evaporative coolers. Water that has been demineralized and/or treated with surfactants and/or fungicides and bactericides are examples of treated water. Aqueous solutions would include homogeneous mixtures in which water is the solvent.

p-0022A reservoir <b>20</b> is provided at the air-conditioning unit adjacent the bottom of the evaporative pad <b>12</b> as an adjunct to the evaporative cooler <b>10</b>. Water is added to the reservoir <b>20</b> through water inlet <b>21</b> in order to maintain sufficient water in the reservoir for the purpose of delivering the water in adequate amounts to the liquid coolant-receiving surface <b>18</b> of the evaporator pad. The delivery of the water is accomplished, for example, by means of a pump <b>24</b> that pumps water from the reservoir <b>20</b> through a conduit <b>25</b> to a water-delivery header <b>26</b>. The water-delivery header <b>26</b> delivers water to a liquid coolant distribution container, indicated generally at <b>28</b>, and, from the container, the water flows to the liquid coolant-receiving surface <b>18</b> of the evaporative pad <b>12</b>. The water-delivery header <b>26</b> can be configured so as to deliver the water in relatively equal amounts along the length and across the width of the liquid coolant distribution container <b>28</b>. From the liquid coolant-receiving surface <b>18</b>, the water flows downwardly towards the bottom of the evaporative pad <b>12</b>. The reservoir <b>20</b> also includes a drain <b>23</b> for removing sludge from the bottom portion of the reservoir that may accumulate over time.

p-0023The water distributed to the liquid coolant-receiving surface <b>18</b> and passing into the evaporative pad <b>12</b> wets the evaporator pad as the water flows downwardly through the pad and, thereby, the water tends to be retained, at least in part, at the evaporator pad. To the extent that the water is not retained at the evaporative pad <b>12</b>, the water will flow from the evaporator pad at a liquid coolant-exiting surface <b>19</b> that is included as a part of the evaporator pad. Thus, the liquid coolant, water in the illustrated embodiment, which passes entirely through the evaporative pad <b>12</b> exits the evaporative pad at the liquid coolant-exiting surface <b>19</b>.

p-0024Based on the foregoing description, it will be understood that the air-entry surface <b>14</b>, the air-exiting surface <b>16</b>, the liquid coolant-receiving surface <b>18</b> and the liquid coolant-exiting surface <b>19</b> of the evaporative pad <b>12</b> are arranged so that air flowing from the air-entry surface <b>14</b> to the air-exiting surface <b>16</b> through the evaporative pad <b>12</b> and liquid flowing from the liquid coolant-receiving surface <b>18</b> towards the liquid coolant-exiting surface <b>19</b> through the evaporative pad come into contact with one another. As a result of this contact of the air and the liquid coolant, the liquid coolant evaporates so that the air flowing from the air-entry surface <b>14</b> to the air-exiting surface <b>16</b> through the evaporative pad is cooled.

p-0025The evaporative pad <b>12</b> can be made of any one of a number of evaporative cooling media. One example of a medium that can be employed is excelsior that is held in place by netting. Another example of a medium that can be used is plastic fibers. Corrugated structures, including structures made of corrugated cellulose or plastics also can be used. It can be important that, whatever medium is used, a large surface area be presented to the coolant and the air flowing through the evaporative pad so that cooling of the air upon contact with the liquid coolant is carried out efficiently. It also can be important that the evaporative cooling medium employed have the properties of providing for the relatively even distribution and good retention of the coolant at the medium.

p-0026Turning to a discussion of the construction of the liquid coolant distribution container <b>28</b>, as best illustrated in <figref idrefs="DRAWINGS">FIGS. 2 and 3</figref>, the liquid coolant distribution container can take the form of a trough including sloping sides <b>29</b> that are inclined toward one another in the direction of the bottom of the trough. The liquid coolant distribution container <b>28</b> includes an upper portion <b>32</b> and a lower portion <b>34</b>. The upper portion <b>32</b> of the liquid coolant distribution container can be constructed of sheet material such as stainless steel or plastic sheeting for example and be configured to hold the liquid coolant so that the coolant cannot flow outwardly at the first portion of the liquid coolant distribution container and can flow only downwardly in the trough. The lower portion <b>34</b> of the liquid coolant distribution container is contiguous with the upper portion <b>32</b> and includes an opening <b>36</b> at the base of the lower portion. The lower portion <b>34</b> also includes a permeable bed <b>37</b> that is supported in place over the opening <b>36</b>, and the liquid coolant held in the upper portion <b>32</b> of the liquid coolant distribution container passes through the opening <b>36</b> and the permeable bed <b>37</b> and is distributed to the liquid coolant-receiving surface <b>18</b> of the evaporative pad <b>12</b>. In the example illustrated in <figref idrefs="DRAWINGS">FIGS. 1 and 2</figref>, the liquid coolant distribution container <b>28</b> is shown as supported somewhat above the liquid coolant-receiving surface <b>18</b>. However, the liquid coolant distribution container can be supported on and in contact with the liquid coolant-receiving surface <b>18</b>.

p-0027The permeable bed <b>37</b> is sufficiently permeable to allow water held in the upper portion <b>32</b> of the liquid coolant distribution container to pass through the permeable bed and distributed to the liquid coolant-receiving surface <b>18</b> of the evaporative pad <b>12</b> at a selected rate that is sufficient to adequately keep essentially the entirety of the evaporative pad wetted with the coolant so that essentially the entirety of the air flowing through the pad comes into contact with the coolant and is cooled. An example of a material from which the permeable bed can be made is fiberglass padding. When fiberglass padding is employed, the padding can be placed over the opening <b>36</b> in the lower portion <b>34</b> of the liquid coolant distribution container <b>28</b> and held in place by the sloping sides <b>29</b>, <b>29</b> of the container. Another example of a material that can be used to form the permeable bed is relatively finely divided plastic material that can be contained within suitable netting and the finely divided plastic-filled netting placed over the opening <b>36</b>. It will be understood to those skilled in the art that the sides of the trough need not be sloping as shown in the drawings but can be arranged so as to be positioned substantially vertically. In that case, it can be necessary to provide retainers of a suitable sort to hold the permeable bed in place over the opening <b>36</b>.

p-0028In order to be most assured that the liquid coolant distribution container <b>28</b> will function to wet essentially the entirety of the evaporative pad <b>12</b>, as best seen in <figref idrefs="DRAWINGS">FIG. 2</figref>, the perimeter of the outer boundary of the evaporative pad <b>12</b>, the perimeter of the liquid coolant-receiving surface <b>18</b> and the perimeter of the opening <b>36</b> in the lower portion <b>34</b> of the liquid coolant distribution container <b>28</b> can be substantially co-extensive with one another. That is, these elements can have substantially the same outer dimensions or limits. Consequently, coolant flowing through the opening <b>36</b> in the liquid coolant distribution container <b>28</b> will flow to essentially the entirety of the liquid coolant-receiving surface <b>18</b> of the evaporative pad <b>12</b>; and the liquid coolant passing through the liquid coolant-receiving surface <b>18</b> and into the evaporative pad <b>12</b> will flow downwardly and wet essentially the entirety of the evaporative pad <b>12</b> so that essentially the entirety of the air flowing through the evaporative pad will come into contact with the liquid coolant and essentially the entirety of the flowing air cooled. Thereby, the development of hot spots in the evaporative pad <b>12</b> that can be the cause of damage to the blades of the compressor and the consequent operational failure of the gas turbine system can be avoided.

p-0029Essentially the entirety of the evaporative pad can be considered to have been wetted and essentially the entirety of the air can be considered to have been contacted by the coolant so that essentially the entirety of the air is cooled whenever the properties of the air passing through the evaporative pad are only negligibly different from the properties of air that has passed through the evaporator pad when it has been wetted in its entirety.

p-0030Another aspect of the invention that can be included in the construct of the liquid coolant distribution container <b>28</b> concerns features of the liquid coolant distribution container that result in the liquid coolant being distributed to the liquid coolant-receiving surface <b>18</b> of the evaporative pad <b>12</b> at a selected rate. The selected rate would be sufficient to cause essentially the entirety of the evaporative pad to be wetted by the liquid coolant flowing from the liquid coolant-receiving surface <b>18</b> of the evaporator pad towards the liquid coolant-exiting surface <b>19</b> of the evaporator pad. However, the selected rate would not be substantially greater than is required for that purpose and would be insufficient to cause an excessive amount of the liquid coolant to exit the liquid coolant-exiting surface <b>19</b> of the evaporative pad <b>12</b>. In this aspect, the excessive recirculation of the water from the reservoir <b>20</b> to the water-delivery header <b>26</b> is avoided.

p-0031The rate at which liquid coolant will flow through the opening <b>36</b> in the liquid coolant distribution container <b>28</b>, aside from the physical properties of the liquid coolant itself such as its viscosity for example, is essentially dependent on the depth of the liquid coolant in the container, or the magnitude of the head of the liquid coolant in the container, and the permeability characteristic of the permeable bed <b>37</b>. Consequently, in the example of the invention shown in the drawings, the upper portion <b>32</b> of the liquid coolant distribution container <b>28</b> is configured to maintain the liquid coolant at a selected depth in the upper portion <b>32</b> of the liquid coolant distribution container <b>28</b> above the permeable bed <b>37</b> and the permeable bed has a permeability characteristic, such that the liquid coolant is distributed to the liquid coolant-receiving surface <b>18</b> of the evaporative pad <b>12</b> through the permeable bed <b>37</b> at a rate that is sufficient to cause essentially the entirety of the evaporative pad <b>12</b> to be wetted by the liquid coolant flowing from the liquid coolant-receiving surface <b>18</b> of the evaporator pad towards the liquid coolant-exiting surface <b>19</b> of the evaporator pad but insufficient to cause an excessive amount of liquid coolant to exit the liquid coolant-exiting surface of the evaporative pad.

p-0032The depth of the liquid coolant in the liquid coolant distribution container can be controlled, simply, by controlling the height to which the top of the container extends. In that case, coolant delivered to the container would be delivered at a rate such that coolant would continually flow to outside the container over the top of the container. In the embodiment shown in the drawings, however, an alternate technique is employed to control the depth of the liquid coolant. Thus, as best seen in <figref idrefs="DRAWINGS">FIGS. 2 and 3</figref>, a notch <b>31</b> is provided in the rear panel <b>33</b> of the liquid coolant distribution container <b>28</b>. The bottom of the notch establishes the height to which coolant in the container can be maintained, with the coolant being delivered to the container from the water-delivery header <b>26</b> at a sufficient rate to cause coolant to continually, but somewhat slowly, flow through the notch in order to maintain that height. The coolant flowing from the liquid coolant distribution container through the notch <b>31</b> can be collected and routed through a conduit, for example, to the reservoir <b>20</b>. It will be understood to those skilled in the art that water can be delivered to the liquid coolant distribution container <b>28</b> using other than the water-delivery header <b>26</b> illustrated in <figref idrefs="DRAWINGS">FIG. 1</figref>. For example, a simple water delivery line can be hung over the top of one of the sloping sides <b>29</b> of the liquid coolant distribution container. Alternately, an opening can be made in a side of the upper portion <b>32</b> of the container and the water line secured to the opening at the water line's discharge point.

p-0033The permeability characteristic of the permeable bed <b>37</b> can be established in any one or more of a number of ways. For example, the medium selected to make up the permeable bed can influence the permeability characteristic of the bed. Thus, a permeable bed of a fiberglass material can have a permeability characteristic that is different than the permeability characteristic of granulated material such as finely divided plastic spheres. Also, the permeability characteristic of the fiberglass material itself can be influenced by the density of the fiberglass material. As well, the permeability characteristic of the granulated material can be influenced by how tightly the granules are packed together for example.

p-0034It will be understood from the foregoing description that in one aspect, the invention can include a method of cooling air including passing a liquid coolant through an evaporative pad of an evaporative cooler and wetting essentially the entirety of the evaporative pad with the liquid coolant as the liquid coolant passes through the evaporative pad. The method can also include passing the air to be cooled through the essentially entirely wetted evaporative pad and contacting essentially the entirety of the air with the essentially entirely wetted evaporative pad, whereby essentially the entirety of the air passing through the essentially entirely wetted evaporative pad is cooled. In another aspect, the method can include distributing the liquid coolant to a liquid coolant-receiving surface at the evaporative pad by passing the liquid coolant through a permeable bed before passing the liquid coolant into the evaporative pad. In still another aspect, the method can include maintaining the depth of the liquid coolant in the upper portion of a liquid coolant distribution container at a level and the permeability characteristic of the permeable bed at a value such that the liquid coolant is distributed to the liquid coolant-receiving surface of the evaporative pad through an opening in the liquid coolant distribution container and the permeable bed that overlies the opening at a rate that is sufficient to cause essentially the entirety of the evaporative pad to be wetted by the liquid coolant flowing from the liquid coolant-receiving surface of the evaporator pad towards a liquid coolant-exiting surface of the evaporator pad but insufficient to cause an excessive amount of liquid coolant to exit from the liquid coolant-exiting surface of the evaporative pad. In yet further aspects, the invention can include the foregoing methods wherein liquid coolant distribution containers and evaporative pads of the types described above can be employed and the methods are employed to provide cooled air to a gas turbine system.

p-0035While the present invention has been described above and illustrated with reference to certain embodiments thereof, it is to be understood that the invention is not so limited. Thus, the present invention has applications to evaporative cooler systems, or evaporative coolers of essentially any type. These include, but are not limited to, evaporative coolers for cooling air for thermal comfort and evaporative coolers for controlling the temperature of the air in structures such as greenhouses and buildings containing livestock.

p-0036Modifications and alterations will occur to those skilled in the art upon reading and understanding the specification, including the drawings. In any event, the present invention covers and includes any and all modifications and variations to the described embodiments that are encompassed by the following claims.