Patent Application
20130000329
1. Field of the Invention
The 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.
2. Discussion of the Prior Art
Evaporative 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.
Typically, 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.
Evaporative 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.
The 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.
The 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.
In 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.
In 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.
The 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:
Examples 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.
A compressor 52 at the gas turbine system 50 functions to draw ambient air into the air inlet 41 of the air-conditioning system 40 and through the air-conditioning system. After being suitably conditioned at the air-conditioning system 40, the air streams through the adapter duct 44 (sometimes referred to as a transition duct or bellmouth) to the compressor 52. The conditioned air, upon entering the compressor 52, is compressed to relatively high pressures. Thereafter, the compressed air enters a combustion area 54 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 54. The high-pressure, high-velocity gases proceed to a turbine 55 possessed with considerable energy and drive the blades of the turbine that are attached to an output shaft 56. The rotation of the turbine blades causes the output shaft 56 which is attached to rotate as well, and the energy of the output shaft 56 as it rotates is delivered to a generator 58 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.
For optimum plant operation, air from the ambient environment is used at the gas turbine system 50. The ambient air may first be conditioned and that is accomplished at the air-conditioning system 40. Again referring to
The filtered and cooled air that exits the evaporative cooler 10 flows to demisters 43 which remove unwanted water from the air. From the demisters, the air flows into the adapter duct 44 and from the adapter duct the conditioned air flows to the gas turbine system 50 where the conditioned air after being compressed is mixed with fuel and burned as described above. The arrows in
The evaporative cooler 10 itself includes an evaporative pad, indicated generally at 12 in
A reservoir 20 is provided at the air-conditioning unit adjacent the bottom of the evaporative pad 12 as an adjunct to the evaporative cooler 10. Water is added to the reservoir 20 through water inlet 21 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 18 of the evaporator pad. The delivery of the water is accomplished, for example, by means of a pump 24 that pumps water from the reservoir 20 through a conduit 25 to a water-delivery header 26. The water-delivery header 26 delivers water to a liquid coolant distribution container, indicated generally at 28, and, from the container, the water flows to the liquid coolant-receiving surface 18 of the evaporative pad 12. The water-delivery header 26 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 28. From the liquid coolant-receiving surface 18, the water flows downwardly towards the bottom of the evaporative pad 12. The reservoir 20 also includes a drain 23 for removing sludge from the bottom portion of the reservoir that may accumulate over time.
The water distributed to the liquid coolant-receiving surface 18 and passing into the evaporative pad 12 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 12, the water will flow from the evaporator pad at a liquid coolant-exiting surface 19 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 12 exits the evaporative pad at the liquid coolant-exiting surface 19.
Based on the foregoing description, it will be understood that the air-entry surface 14, the air-exiting surface 16, the liquid coolant-receiving surface 18 and the liquid coolant-exiting surface 19 of the evaporative pad 12 are arranged so that air flowing from the air-entry surface 14 to the air-exiting surface 16 through the evaporative pad 12 and liquid flowing from the liquid coolant-receiving surface 18 towards the liquid coolant-exiting surface 19 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 14 to the air-exiting surface 16 through the evaporative pad is cooled.
The evaporative pad 12 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.
Turning to a discussion of the construction of the liquid coolant distribution container 28, as best illustrated in
The permeable bed 37 is sufficiently permeable to allow water held in the upper portion 32 of the liquid coolant distribution container to pass through the permeable bed and distributed to the liquid coolant-receiving surface 18 of the evaporative pad 12 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 36 in the lower portion 34 of the liquid coolant distribution container 28 and held in place by the sloping sides 29, 29 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 36. 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 36.
In order to be most assured that the liquid coolant distribution container 28 will function to wet essentially the entirety of the evaporative pad 12, as best seen in
Essentially 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.
Another aspect of the invention that can be included in the construct of the liquid coolant distribution container 28 concerns features of the liquid coolant distribution container that result in the liquid coolant being distributed to the liquid coolant-receiving surface 18 of the evaporative pad 12 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 18 of the evaporator pad towards the liquid coolant-exiting surface 19 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 19 of the evaporative pad 12. In this aspect, the excessive recirculation of the water from the reservoir 20 to the water-delivery header 26 is avoided.
The rate at which liquid coolant will flow through the opening 36 in the liquid coolant distribution container 28, 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 37. Consequently, in the example of the invention shown in the drawings, the upper portion 32 of the liquid coolant distribution container 28 is configured to maintain the liquid coolant at a selected depth in the upper portion 32 of the liquid coolant distribution container 28 above the permeable bed 37 and the permeable bed has a permeability characteristic, such that the liquid coolant is distributed to the liquid coolant-receiving surface 18 of the evaporative pad 12 through the permeable bed 37 at a rate that is sufficient to cause essentially the entirety of the evaporative pad 12 to be wetted by the liquid coolant flowing from the liquid coolant-receiving surface 18 of the evaporator pad towards the liquid coolant-exiting surface 19 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.
The 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
The permeability characteristic of the permeable bed 37 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.
It 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.
While 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.
Modifications 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.
