US20130081414A1

US20130081414A1 - Evaporative cooler

Info

Publication number: US20130081414A1
Application number: US13/250,952
Authority: US
Inventors: John D. Penton
Original assignee: Chevron USA Inc
Current assignee: Chevron USA Inc
Priority date: 2011-09-30
Filing date: 2011-09-30
Publication date: 2013-04-04
Also published as: WO2013049685A4; WO2013049685A1

Abstract

An evaporative cooler that includes a frame, a plurality of pads attached to the frame so that the pads substantially enclose an air space to be cooled, a water delivery device positioned at or near the top of the pads to wet the pads, a plurality of drain pans positioned at or near the bottom of the pads to collect water from the pads, and a fan to draw air through the wetted pads, thereby cooling the air by evaporation.

Description

FIELD OF THE INVENTION

The present invention relates generally to evaporative coolers using cooling pads. More particularly, the present invention relates to evaporative coolers having discrete cooling pads that can be removed and replaced individually.

BACKGROUND AND SUMMARY OF THE INVENTION

Air cooled heat exchangers are commonly used in a wide variety of industries. As the name implies, heat exchangers are devices where two moving fluid streams exchange heat. In an air cooled heat exchanger, a fluid that is circulated through tubes may be cooled by forcing relatively cool ambient air to flow over the exterior of the tubes. As the ambient air passes over the exterior of the tubes, it absorbs heat from the fluid within the tubes, thereby cooling the fluid. As used herein, the term tubes refers to any mechanism for conveying fluid through a heat exchanger, including pipes of any shape, pressure vessels, etc. The lower the temperature of the ambient air, the greater is its capacity to absorb heat. Thus, air cooled heat exchangers are most effective where the ambient air used to cool is at a low temperature.
It stands to reason, therefore, that the performance of air cooled heat exchangers suffers when the heat exchanger is operated in a hot climate or during the summer months when the temperature of the ambient air is relatively high. Under such conditions, air cooled heat exchanger performance deteriorates rapidly. As a result, it is necessary to pre-cool the ambient air prior to its introduction to the heat exchanger.
There are numerous methods and devices for cooling air prior to its initiation to a heat exchanger, such as, for example, subjecting the air to a refrigeration process or an evaporative cooling process. Cooling systems that rely on a refrigeration cycle have disadvantages, including the fact that they typically have high initial and operating costs. Where the climate permits (i.e., where the climate is hot and dry), evaporative cooling may provide a better solution.
Evaporative cooling relies on one simple principle: As water evaporates, heat is absorbed from the surrounding air. As a result, the air is cooled during the process. An evaporative cooler preferably includes porous cooling pads that substantially surround an enclosed space that includes a fan. Moisture is applied to the pads, typically either by dripping water into the top end of the pads, or by spraying the pads with a mister. The fan is arranged to pull ambient air through the pads and into the enclosed space. As the air passes through the pads, the moving air evaporates the water in the pads. This evaporation cools the air as it enters the enclosed space. The fan then expels the cooled air from the enclosed space through an outlet.
One advantage to an evaporative cooler such as that just described is that the water supplied to the cooler does not need to be clean. If water that has impurities or contaminates is provided to the cooling pads, the air passing through the pads will still evaporate the water and be cooled. The contaminates will simply stay in the pads. Thus, in theory evaporative coolers are well suited to use, for example, in heavy applications such as oil production, where the water available may be contaminated with oil.
The practical use of evaporative coolers in industrial or other heavy applications is limited, however, by the size of the coolers required. Some applications require such a large amount of air to be cooled that evaporative coolers having very large air intake surface areas would be required to meet the demand. For example, a typical cooler bank at an oil production facility might require an air intake surface area of around 50,000 square feet or more. The size of the cooling pads that would be needed on a conventional evaporative cooler of that size would be impractical to manufacture, maintain, or replace.
In one embodiment, the present invention provides an evaporative cooler that includes a frame, a plurality of pads attached to the frame so that the pads substantially enclose an air space to be cooled, a water delivery device positioned at or near the top of the pads to wet the pads, a plurality of drain pans positioned at or near the bottom of the pads to collect water from the pads, and a fan to draw air through the wetted pads, thereby cooling the air by evaporation.
In another embodiment, the present invention may also provide an air cooled heat exchanger that includes cooling tubes containing a fluid to be cooled, and a supply of air that flows over the cooling tubes, the air having a lower temperature than the fluid to be cooled so that the air absorbs heat from the fluid, thereby cooling the fluid, and wherein at least a portion of the supply of air is provided by an evaporative air cooler. The evaporative air cooler includes a frame having a plurality of vertical open sides, wherein each side includes two or more stacked cooling sections, a plurality of pads attached to the frame so that the pads enclose the open sides of the frame, each pad corresponding to a cooling section, a plurality of water pipes attached to the cooler and positioned at the top of each cooling section adjacent the top of the pads, the water pipes having apertures arranged to allow water to exit the pipes and wet the pads, a plurality of drain pans positioned at the bottom of each cooling section adjacent the bottom of the pads to collect any water that drips from the pads, and a fan configured to draw air through the wetted pads, thereby cooling the air by evaporation, and provide the cooled air to the heat exchanger.
In one embodiment, the present invention also provides a method of cooling air, the method including the steps of providing a plurality of cooling pads stacked one on top of the other and substantially enclosing an air space to be cooled, wetting the cooling pads at an upper portion thereof, and pulling ambient air through the wetted cooling pads and into the air space to be cooled.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the subject matter of the present invention and the various advantages thereof can be realized by reference to the following detailed description in which reference is made to the accompanying drawings in which:

FIG. 1 is a schematic perspective view of a cooler;

FIG. 2 is a perspective view of the frame of a cooler;

FIG. 3 is a schematic cross-sectional view of the cooling pads, water delivery pipes, and drain pans of a cooler taken along line 3-3 of FIG. 1;

FIG. 4A is a perspective view of an intermediate drain pan to be positioned between two adjacent stacked cooling pads;

FIG. 4B is a perspective view of a bottom drain pan to be positioned below the bottom most cooling pad;

FIG. 5A is a perspective view of water delivery pipe corresponding to one layer of cooling pads; and

FIG. 5B is a perspective view of a portion of the water delivery pipe of FIG. 5A showing the perforations through which water is delivered.

DETAILED DESCRIPTION OF THE INVENTION

The foregoing aspects, features, and advantages of the present invention will be further appreciated when considered with reference to the following description of preferred embodiments and accompanying drawings, wherein like reference numerals represent like elements. In describing embodiments of the invention illustrated in the appended drawings, specific terminology will be used for the sake of clarity. However, the invention is not intended to be limited to the specific terms used, and it is to be understood that each specific term may include equivalents that operate in a similar manner to accomplish a similar purpose.
Referring now to the drawings, FIG. 1 shows a schematic perspective view of a cooler 10 according to one embodiment of the present invention. The cooler includes a face portion 16 having at least one fan located in an opening 12. As shown in FIG. 1, the face portion 16 may include a plurality of fans, although such is not necessary. The number of fans will depend on the size of the cooler, among other factors. The sides of the cooler 10 are substantially enclosed with cooling pads 14. The cooling pads 14 are porous, thereby allowing for the passage of air through the pads 14. In practice, water is introduced to the pads 14 at a top portion thereof and descends through the pads until the pads are wet. The fans are configured to draw air from the ambient environment to the inside of the cooler through the pads 14. As the air passes through the wet pads, heat from the air evaporates the water in the pads, thereby cooling the air. The cooled air may then be propelled from inside the cooler 10 through outlets on the face portion by the fans.
Each side of the cooler may preferably include a plurality of discrete pads that may be individually removed for cleaning or replacement. One advantage to such a configuration is that individual pads are smaller and may be removed and replaced more easily. As the pads become worn out or saturated with contaminates from water that has been evaporated, such removal of the pads for cleaning or replacement may be needed. A configuration with smaller pads, such as that shown in FIG. 1, allows for such removal and replacement of pads with minimal interruption to the operation of the cooler 10. For example, the pads may be removed and replaced while the cooler is running, thereby avoiding potentially costly downtime.
In one embodiment, the cooler 10 may include, a plurality of pads 14 that lie horizontally and are stacked one on top of the other as shown in FIG. 1. Alternatively, the pads may be angled with respect to the face of the cooler, or positioned vertically side by side. If the pads are angled, they may be positioned so that the centerline of each pad lies at a 45 degree angle to the horizontal face of the cooler. Alternatively, the pads may be angled less than 45 degrees to the horizontal face, such as, for example, around 10, 20, 30, or 40 degrees, or more than 45 degrees, such as around 50, 60, 70, or 80 degrees. The orientation and arrangement of the pads is not critical to the invention.
Any pad that holds water, and allows air to pass through the pad to evaporate the water, may be used in the present invention. The materials that make up the pads and the manner of construction of the pads are not critical. One example of a cooling pad that may be used in one embodiment consists of impregnated and corrugated cellulose paper sheets with different flute angles, one steep (e.g., about 60 degrees) and one shallow (e.g., about 30 degrees), that have been bonded together. This particular design yields a cooling pad with a high evaporation efficiency while still operating with a very low pressure drop. In addition, such a design keeps scaling to a minimum because water is naturally directed to the air inlet side of the pad, where most of the evaporation takes place. In addition, the impregnation procedure for the cellulose paper ensures a strong self-supporting pad, with high absorbance, which is protected against decomposition and rotting. Alternatively, pads may be constructed of other materials, such as, for example, excelsior (wood wool), plastics, and melamine paper.
Referring now to FIG. 2, there is shown a perspective view of a cooler 10 according to one possible embodiment of the present invention with the pads removed. As can be seen, the frame 18 of the cooler 10 includes legs 20 that may be positioned at corners of the cooler 10 such that the area between the legs 20 forms the sides of the cooler. The legs 20 of frame 18 may serve to support the stacked pads 14 (shown in FIG. 1). The embodiment of FIG. 2 further shows an air intake 22 inside the cooler 10 that has at least one fan (not shown) positioned therein. In operation, the fan is arranged to pull air into the air intake 22 and expel it through the face portion 16 of the cooler. When the pads 14 are in place, such as shown, for example, in FIG. 1, air is pulled through the pads 14 toward the air intake 22.
The frame may be made of any suitable material, which material may vary depending on the requirements of the cooling system, the environment in which the cooling system is operated, and many other factors. In one embodiment, the frame may be constructed of steel. The frame may be constructed so that the cooler is positioned above the ground. For example, in one embodiment, the cooler may be 30 feet or more above the ground. In other embodiments, the cooler may be 10, 15, 20, or 25 feet or more off the ground. The placement of the cooler will depend on the conditions at the site where the cooler is to be installed and the arrangement of components to which the cooler is to be connected, such as a heat exchanger. The size and configuration of the frame will vary depending on factors such as the size of the cooler and the position of the cooler above the ground. For example, a larger cooler will require a larger, more heavy duty frame. Similarly, a cooler that is 30 feet or more above the ground will require a frame structure capable of lifting the cooler to that height while still providing a stable foundation for the cooler to rest on. Accordingly, the size, configuration, and composition of the frame are not critical to the invention.
FIG. 3 shows a cross-sectional view of the cooling pads 14, as well as water delivery pipes 24, intermediate drain pans 26, and bottom drain pan 28 taken along line 3-3 of FIG. 1. As discussed above, in practice water is introduced to the pads 14 at a top portion thereof and descends through the pads until the pads are wet. To accomplish this, water is delivered to the top of each pad by water delivery pipes 24. The water delivery pipes 24 have apertures 30 (shown in FIG. 5B) that allow water running through the pipes to discharge directly onto the pads 14 at an interface 32 between the water pipes 24 and the pads 14. As discussed above, the pads 14 are porous and are typically constructed of a plurality of corrugated cellulose paper sheets that are bonded together, although any suitable material may be used. As the water is delivered to the top of each pad 14, it travels downward through the porous pad until substantially all of the pad becomes wet. Excess water drains from the bottom of the pad.
At the bottom of each pad there is preferably a drain pan 26, 28. All but the bottom most pads are positioned above intermediate drain pans 26. The intermediate drain pans 26 are configured to collect water that drains from the bottom of the pad directly above each intermediate drain pan 26, and deliver that water to the top of the next lower pad. The bottom drain pan 28 is positioned below the bottom most pad. The bottom drain pan 28 may be shaped differently from the intermediate drain pans 26 because the function of the bottom drain pan 28 is not to deliver water to a lower pad, but rather to collect water for reuse either in the cooler or elsewhere, or for disposal according to known methods. A more detailed explanation of the shape and function of the intermediate and bottom drain pans 26, 28 is written below with respect to FIGS. 4A and 4B.
In operation, the water delivery pipes 24 deliver water to the tops of pads 14 and the water percolates down through the pads 14 until the pads are wetted. Ambient air is pulled through the pads, as discussed above, by fans 12 into an air intake inside the cooler 10. The direction of motion of the air through the pads is indicated in FIG. 3 by arrows A. As the air passes through the wet pads, it evaporates the water in the pads. The energy required for such evaporation is pulled from the passing air in the form of latent heat. Thus, as the air passes through the pads and the water evaporates, the air is cooled. Because of this evaporation, much of the water that is provided to the top of the pads by the water delivery pipes 24 never reaches the bottom of the pads. The water that does reach the bottom of the pads, however, drains into the intermediate drain pans 26 and is channeled to the top portion of the next lower pad. Any water that reaches the bottom of the bottom most pad drains into the bottom drain pan 28 where it may be recycled for reuse, in which case it is reintroduced to the water delivery pipe system, or it may be disposed of according to conventional methods.
There is shown in FIGS. 4A and 4B drain pans according to an embodiment of the present invention. FIG. 4A shows an intermediate drain pan 26 that may be sloped from a raised first end 34 to a depressed second end 36. The sides of the drain pan 26 are raised and enclose a trough 38 for catching water. When in use, a pad 14 is positioned so that its bottom portion drains excess water into the trough 38. If the drain pan 26 is sloped, the water runs to the depressed second end 36 thereof. At the depressed second end 36 there is an aperture (not shown) or other outlet that permits the water to exit the trough 38 of the drain pan 26, where it enters the top of the next lower pad (see FIG. 3). If the drain pan is not sloped, the aperture or other outlet may be positioned anywhere in the bottom of the drain pan.
FIG. 4B shows a bottom drain pan 28 according to an embodiment of the present invention. Similar to the intermediate drain pan 26, the bottom drain pan 28 may have a raised first end 40 and a depressed second end 42. The bottom drain pan also has raised sides that define a trough 44. In the embodiment shown, the bottom drain pan may have a trough 44 that is elongated compared to the troughs 38 of the intermediate drain pans 26. In addition, the slope of the bottom drain pan 28 may change at a slope transition place 46, although the length of the trough and the exact slope of the drain pan are not critical to the design of the cooler and may vary depending on the needs and configuration of a particular cooler arrangement. In addition, there is at least one aperture 48, or other outlet, at or near the depressed second end 42 of the bottom drain pan 28 to allow water to exit the drain pan. After exiting the drain pan, the water may be recycled for reuse in the cooler, or it may be disposed of according to known conventional methods.
The drain pans 26, 28 may be constructed of any suitable material, such as, for example, metal or plastic. Because the function of drain pans 26, 28 is to collect water, they are preferably constructed of a material that will not be adversely affected by contact with water. Furthermore, the shape and configuration of the drain pans in the drawings is merely a representation of one particular embodiment. The shape of the drain pans is not critical to the invention and any shape the allows the drain pans to carry out their intended functions is contemplated.
Referring now to FIG. 5A, there is shown a water distribution pipe 24 according to one possible embodiment of the present invention. The water distribution pipe is preferably positioned around the sides of the cooler 10 so that the pipes are adjacent the top of a row of pads (see, e.g., FIG. 3). There is a water inlet 50 through which water may be supplied to the delivery pipes 24. The water inlet may be configured to connect to, for example, a water hose that is connected to a source of water. The water delivery pipe 24 shown in FIG. 5A is only one portion of the water delivery system that may be employed in a single cooler. For example, the water delivery pipe 24 of FIG. 5A corresponds to a single pipe capable of delivering water to a single layer of pads. However, As shown, in FIG. 3, certain embodiments of the invention contemplate the use of multiple layers of pads, with each layer having its own water delivery pipe 24 similar to that shown in FIG. 5A. Of coarse, more than one pipe may be used to deliver water to each layer of pads. Preferably, for purposes of simplicity, each layer is connected to a single common water source. This is not necessary, however, and different water delivery pipes 24 may be connected to different sources of water. FIG. 5B shows a magnified view of a portion of a water delivery pipe 24 showing apertures 30 through which water may be discharged from the water delivery pipe 24 to a corresponding pad.
The arrangement and construction of the water delivery pipes is not critical to the present invention, and the pipes may be constructed of any material suitable for carrying water. For example, the pipes may be constructed of steel or plastic. In addition, while the water may be discharged from the pipes and onto the pads through apertures in the pipes, as discussed above, this configuration is not critical. Other mechanisms for dispersing water from the pipes to the pads may be employed as well. For example, in one embodiment the pipes may be fitted with nozzles that drip or spray the water onto the pads in the form of a mist.
An advantage of the present invention is that the water used in the cooler need not be clean, although clean water can be used if desired. In one embodiment, the water used in the cooler may be produced water that has been extracted with oil during an oil production process. In such a case, the water may be contaminated with up to 2 percent oil, and sometimes as high as 3 percent or more. Although such produced water may be filtered prior to use in the cooler, this is not necessary. In some cases, the cooler may be connected directly to an oil producing facility with produced water being fed directly to the cooler.
The reason that the cooler of the present invention can be used with contaminated water is because as the water evaporates from the pads, any contaminates within the water will remain in the pads. The consequence of this is that over time, the contaminates within the pads will increase until air flow through the pads is restricted. However, as discussed above, the design of the cooler allows for individual pads to be removed as needed for cleaning or replacement, thereby allowing continued use of the cooler despite the buildup of contaminates from the water. This provides a benefit over coolers that need clean water to operate.
To better understand the cooling potential of an evaporative cooler, the following example may be considered. In the example, a cooler having a width of 112 feet, a length of 62 feet, and a height of 20 feet is provided. This sides of the cooler are enclosed with cooling pads having a thickness of 2 feet. The pads are provided about 850 gallons of water per minute distributed evenly throughout the pads. The ambient air entering the pads has a dry bulb temperature of 104 degrees Fahrenheit, and a wet bulb temperature of 71 degrees Fahrenheit. After passing through the pads and evaporating the water in the pads, the cooled air will have a temperature of 90 degrees Fahrenheit.
Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention.

Claims

What is claimed is:

1. An evaporative cooler, comprising:

a frame;

a plurality of pads attached to the frame so that the pads substantially enclose an air space to be cooled;

a water delivery device positioned at or near the top of the pads to wet the pads;

a plurality of drain pans positioned at or near the bottom of the pads to collect water from the pads; and

a fan to draw air through the wetted pads, thereby cooling the air by evaporation.

2. The evaporative cooler of claim 1, wherein the pads include a bottom pad and intermediate pads positioned above the bottom pad.

3. The evaporative cooler of claim 2, wherein the drain pans associated with the intermediate pads are configured to deliver the collected water to the lower pads.

4. The evaporative cooler of claim 1, wherein the cooler is configured to recycle the collected water for reuse.

5. The evaporative cooler of claim 1, wherein the water is comprises one or more contaminates.

6. The evaporative cooler of claim 5, wherein the one or more contaminates includes oil.

7. The evaporative cooler of claim 1, wherein the frame has a horizontal face, and the fan is configured to expel the cooled air through the face and out of the cooler.

8. An air cooling bank comprising a plurality of evaporative coolers wherein one or more coolers is as claimed in claim 1, wherein the evaporative coolers are connected together and configured to run simultaneously, thereby increasing the amount of air cooled.

9. The evaporative cooler of claim 1, wherein the water delivery device is a plurality of pipes positioned adjacent the top of the pads.

10. The evaporative cooler of claim 9, wherein the pipes have apertures configured to release water from the pipes onto the pads.

11. A method of cooling air, comprising:

providing a plurality of cooling pads stacked one on top of the other and substantially enclosing an air space to be cooled;

wetting the cooling pads at an upper portion thereof;

pulling ambient air through the wetted cooling pads and into the air space to be cooled.

12. The method of claim 11, wherein the water applied to the cooling pads comprises one or more contaminates.

13. The method of claim 12, wherein the one or more contaminates includes oil.

14. The method of claim 11, further comprising collecting excess water for reuse after it passes through the cooling pads.

15. An air cooled heat exchanger, comprising:

cooling tubes containing a fluid to be cooled; and

a supply of air that flows over the cooling tubes, the air having a lower temperature than the fluid to be cooled so that the air absorbs heat from the fluid, thereby cooling the fluid;

wherein at least a portion of the supply of air is provided by an evaporative air cooler, the evaporative air cooler comprising:

a frame having a plurality of vertical sides, wherein each side includes two or more cooling sections;

a plurality of pads attached to the frame so that the pads enclose the sides of the frame, each pad corresponding to a cooling section;

a plurality of water pipes attached to the cooler and positioned at the top of each cooling section adjacent the top of the pads, the water pipes having apertures arranged to allow water to exit the pipes and wet the pads;

a plurality of drain pans positioned at the bottom of each cooling section adjacent the bottom of the pads to collect any water that drips from the pads; and

a fan configured to draw air through the wetted pads, thereby cooling the air by evaporation, and provide the cooled air to the heat exchanger.

16. The evaporative cooler of claim 15, wherein the cooler is configured to recycle the collected water for reuse.

17. The evaporative cooler of claim 15, wherein the water is comprises one or more contaminates.

18. The evaporative cooler of claim 17, wherein the one or more contaminates includes oil.

19. An air cooling bank comprising a plurality of evaporative coolers wherein one or more coolers is as claimed in claim 15, wherein the evaporative coolers are connected together and configured to run simultaneously, thereby increasing the amount of air cooled.