Evaporative Heat Exchange Apparatus

Abstract

A blow-through evaporative heat exchange apparatus having a blower section with a wet deck section above it. The blower section has at least one slanting wall to provide space for an electric motor and blower under the slanting wall. Diffusion means are provided to ensure a uniform flow of air over the cross section of the wet deck.

Parent Case Text

This application is a division of our copending U. S. application Ser. No. 706,003, filed Feb. 16, 1968 and now Pat. No. 3,442,494.

Description

This invention relates to evaporative type heat exchangers of the blow through (forced draft), counter-flow type in which air flows counter-current to the fluid to be cooled or condensed. Although this description is chiefly concerned with evaporative heat exchangers of the cooling tower type, it should be understood that its features and concepts could be adapted to all blow-through evaporative heat exchangers such as evaporative condensers, liquid coolers, gas coolers, etc.

In a conventional type "blow through" cooling tower the water to be cooled is introduced just below mist eliminators through closely spaced spray nozzles to insure an even distribution across the entire surface area of the tower. An example of such an arrangement is disclosed in U. S. Pat. No. 3,198,441 and is hereby incorporated by reference. The water flows by gravity over a wet deck or fill material and drops into a sump below.

A fan section, consisting of one or more centrifugal fans, is fastened to a side wall of the cooling tower and introduces air into a plenum region, which is located above the sump water level but below the wet deck section. This plenum region must be of adequate size so as to allow the air to distribute itself evenly across the wet deck surface sheets. The fan section is usually a separate assembly secured to the outside of the cooling tower wall, thus increasing the overall horizontal width of the tower substantially.

This invention is directed to a more efficient, compact, and light weight unit. The fan and drive motor form an integral part of the pan and sump. There is no substantial extension or protrusion of the fans beyond the cooling tower side wall. The fan motor and drive arrangement are protected from direct exposure by the overhead sloping pan side wall. The sump and plenum is in the form of an inverted right triangle whose apex forms the bottom of the sump. Being triangular in shape, the sump water inventory is greatly reduced with a subsequent reduction in operating weight. The fan discharges high velocity air through a discharge cowl located in the sloping side wall of the pan section. This discharge cowl is situated in the pan section above the sump water level and below the top of the pan. This type of discharge cowl is disclosed in U. S. Pat. No. 3,132,190 to Engalitcheff and the disclosure thereof is hereby incorporated by reference. Due to the compact design, the discharge cowls are necessarily shorter than those of the above patent and not as much air expansion can be accomplished in the cowls themselves, resulting in a somewhat lesser velocity (kinetic) pressure conversion to static pressure. Additional static pressure conversion is accomplished in the pan section because its area gradually expands from the sump water level to the top of the pan section as will become apparent in the following description. According to the present invention, it is possible, without loss of efficiency in the air system, to use a sump of much smaller volume, with resulting saving in weight by reduction in the volume of cooled water inventory and saving in plan area or floor space by locating the fans wholly or partly within the vertical projection of heat exchange section.

It is an object of the present invention to provide evaporative heat exchange apparatus that has greater cooling capacity in proportion to its material weight.

Another object of the present invention is to provide an evaporative cooler characterized by a reduction in weight resulting from a decrease in the still water inventory.

A further object of this invention is to provide a more compact evaporative heat exchanger while maintaining the same cooling efficiency as in comparable prior art units.

Other objects and advantages of this invention will be apparent upon consideration of the following detailed description of several embodiments thereof in conjunction with the annexed drawings wherein:

FIG. 1 is a view in side elevation of a single module of an evaporative cooler of the cooling tower type constructed in accordance with the teachings and principles of the present invention;

FIG. 2 is a vertical section view of an end elevation of two modules of FIG. 1 placed back-to-back with a common sump;

FIG. 3 is a side elevation of a multiple fan unit of FIG. 1 placed end to end;

FIG. 4 is a view in vertical section taken along the line 4--4 of FIG. 3 showing the air fan construction at a much enlarged scale;

FIG. 5 is a view in horizontal section taken along the line 5--5 of FIG. 2;

FIG. 6 is a partial perspective view of the plenum chamber section showing the baffle angle.

It is to be understood that FIG. 1 illustrates the basic unit of this invention, where the sump is an inverted right triangle and a single blower or several blowers on a single shaft driven by a single motor is located under the hypotenuse of that triangle so that no substantial projection beyond the superstructure of the unit is necessary in order to house the motor and blower(s) as has been necessary in the prior art. This single unit then represents a basic form of the invention and a basic module which can be increased in capacity by securing similar units in an end relationship. Such a multiple unit can then be further increased increased in capacity by securing similar units "back-to-back" so that the right triangle sump becomes an inverted isosceles triangle as depicted in FIG. 2 with a motor and blowers located under each of the equal sides of that triangle.

When two basic units are secured back-to-back, suitable modifications are made in the sump and drain fittings so that the sumps are joined and a common water outlet can be used.

Referring now to the drawings in greater detail and, more particularly, to FIGS. 1, 2 and 3 thereof, in which the cooling tower illustrated is comprised of an upper portion 10 (in which the water is cooled) and a lower sump portion in the form of a V trough or container 11 in which the cooled water is collected. The upper portion 10 is rectangular in plan and is made up of a number of frames superimposed in registry to define four vertical side walls.

The lower part of sump section 11 has two vertical opposite walls 12 and 13 in the plane of two of the side walls of the upper casing section and, between them, wall 14 disposed at 45.degree. to the vertical, convergent and intersecting to define with the walls 12 and 13 the V trough 11. Water to be cooled is supplied through manifold 16 and issues from various spray nozzles 17 to fall by gravity through a cooling region containing a wet deck surface section in the form of a large number of sheet metal elements 18 held by frames in horizontally and vertically spaced relation to present to the water, in total, a large surface area. The water, after flowing through the cooling area in contact with the various sheet metal elements 18 falls by gravity into the V sump 11. This wet deck section is more fully disclosed in the co-pending application Ser. No. 706,004 now abandoned entitled "Wet Deck Fill Section" of the same assignee and filed on even date. Although this particular section has been illustrated, any wet deck or any evaporative heat exchange surface can be used in connection with this invention.

The unit illustrated in FIGS. 1 to 3, inclusive, is provided with centrifugal blowers which, by means to be hereinafter more fully described, cause air to flow upwardly between the surface elements 18 counter-current to the gravitating water, whereby some of the water is evaporated and carried upwardly with the flowing air to leave the unit through mist eliminators 19 arranged at the top thereof. Although a centrifugal blower is illustrated, the unit would operate equally as well with axial flow fans and the term "blower" as used herein is intended to encompass both. The heat extracted from the remaining water is, of course, carried with the exhausting air to the ambient atmosphere. As previously stated, the cool water falls to the sump. Makeup water enters through valve 20 opened by float 21 (see FIG. 2) and replaces the evaporated water and any waste water which has been drained to reduce contamination, etc.

The cooled water is withdrawn from the sump 11 through a conduit 22 and delivered by a pump 23 and conduit 24 to a point of use such as the heat exchanger schematically shown at 25 in FIG. 3. After use, the water has taken on heat and must be returned to the cooling unit for cooling. This return is effected through conduit 26 leading to manifold 16.

Now that the cycling of the water has been described, attention is called to the effect of the V-bottom sump 11 upon water inventory. Because the lower portion of the triangular or V-section trough is of very small volume, only a very little water is held in inventory, with a decided advantage in reducing weight load on the supporting area which accommodates the unit.

Not only does the V-bottom of the sump reduce the amount of the water inventory, but it also, by an arrangement constituting an important part of the present invention, permits locating of the blowers substantially within a vertical projection of the rectangular plan of the upper portion 10 of the unit and because of its V shape promotes static pressure increase in the sump section. Of course it is desirable that the fan(s) ae completely under the sloping wall if possible. However, if a large blower is used due to particular design requirements, then there may be some projection beyond the side wall of the unit.

The air distribution for a multiple-blower unit as illustrated in FIG. 5 is described later in detail. As viewed in FIGS. 2 and 5, there are two sets of three centrifugal blowers each, a left-hand set the nearest blower of which bears reference numeral 28, and a right-hand set the nearest blower of which bears reference numeral 29. Blower 29 and the two blowers 30 and 31 behind it are keyed to a common drive shaft 32 to which there is also keyed a sheave 33 connected by multiple belts 34 to a drive sheave 35 of an electric motor 36. Motor 36 is mounted on a base plate 37 slidable in tracks 38. Connected to base plate 37 is a bracket 39 having a threaded stud 40 passing through it. This stud also passes through a U-section piece 41 which is the bottom piece of framework of the blower and motor support system. The stud 40 is provided with nuts 42 by adjustment of which on the stud 40 the motor mount may be easily shifted and held to control the tension on belts 34.

An arrangement identical to that just described is provided for the blower 28 and the two blowers behind it. In this case the motor bears numeral 44, the belt adjusting assembly 45, the belt sheave 46, the common drive shaft 47.

All of the centrifugal blowers, such as blowers 28 and 29, are of the axial intake, radial discharge type. The individual blowers are spaced apart, and shaft bearings are located on each end of a group of blowers. Typical of the construction is the arrangement shown in FIG. 3, where shaft 32 is provided with a main front bearing at 48 to the left of fan 29 and at the end of shaft 32 remote from the sheave 33 there is located another main bearing 50. Due to the fact that an enlarged diameter shaft is used between bearings 48 and 50 only these outboard bearings are required with no bearing between the blowers on a single shaft. The main bearings 48 and 50 are held by rigid frame members such as 51 and 52 which extend between U-section base members 41 and the wall 14. The sides of each fan, essentially triangular in shape, bear reference numerals 53, 54 and 55. They are arranged in parallel, spaced relationship extending vertically from the bottom of the unit to the sloping wall 14 of the pan section. Walls 53, 54 and 55 show in FIG. 3 and, of course, the front face of an equivalent wall 56 appears on the left side of FIG. 2. Note that the blowers are held between these vertical walls in this particular unit, in a position wholly underlying the sloping walls 14 and 15 of the pan units.

The outlet side of each blower, such as 28 and 29, is connected to air ducting which passes through the respective sloping wall 15, 14 of the pan section and terminates in a mouth lying nearly in a vertical plane but sloping slightly in a direction opposite to the slope of the respective wall 14 or 15 through which the ducting passes. The ducting associated with blower 29 includes a portion 58 lying wholly within the sump 11. Blower 30 is provided with a duct portion 59 within the sump and blower 31 with a portion 60. In FIG. 5 portions 61 and 62 within the sump 11 serve the two unnumbered blowers which lie behind blower 28 as it is viewed in FIG. 2 and which lie beside it. These duct portions are all of identical construction, usually of rectangular cross section and therefore only the ducting for blower 29 will be described in detail.

In FIG. 4, blower 29 is shown to an enlarged scale with side wall 53 cut away to reveal the construction of the ducting from the cutoff at 63 to the mouth 64 of the interior ducting portion 58. The total ducted area is defined by wall 53, removed in FIG. 4 for convenience of illustration, spaced parallel wall 54, a curved wall located between walls 53 and 54 and extending spirally from the cutoff 63 through the side wall 14 of the sump to terminate at 66, flange portion 68 and duct portion 58. Notice that both ends, the cutoff end at 63 and the end at 66, of the spiral wall 65 telescopes into duct 68 which is fastened by its flanges 68 to the inner surface of the wall 14 of the V sump 11. The air path defined by the walls 53, 54 and 65 and the added duct portion 58 and flange portion 68 is of progressively increasing cross-sectional area in the direction of air flow, so that a considerable measure of conversion of velocity pressure to static pressure is accomplished between the cutoff 63 and the mouth 64 of the ducting system. Note that the fan 29, as illustrated in FIG. 4, rotates in a counterclockwise direction.

In the back-to-back unit, the sump or pan section 11, as illustrated in FIGS. 2, 4 and 5, is centrally divided by a partition 69 which extends between walls 12 and 13 and from the top of the pan section downwardly somewhat below the water level of the sump. Below the lower end of the partition 69 there is located an air-antientrainment baffle 70 which extends horizontally across the bottom of the sump above the level of outlet pipe 22. The plate 70 also functions to equalize the withdrawal of water from the sump 11, since it is tapered to present a wider opening for water passage on the end remote from the outlet. Directly above the air-antientrainment baffle 70 there can be located a strainer supported by appropriate brackets.

Upon reference to FIGS. 1, 2 and 5 it can be seen that the air issuing from the mouths of the various ducts 57 to 62, inclusive, is directed into a somewhat confined space defined at the bottom by the water level and in front of the duct mouth by partition 69 and behind the duct by the sloping wall 14 or 15, as the case may be. While there is a measure of static pressure increase before the air leaves the various duct portions 57 to 62, inclusive, yet the velocity of the air issuing from the mouths of these ducts is too high for efficient and even air distribution across the cross section of the fill region which lies above the V-sump section 11. In the form of the invention illustrated in FIGS. 1 to 4, inclusive, several means are shown which contribute to the evenness of the distribution of air across the cross section of the fill. One of these is the fact that the portion of the sump chamber above the fan outlet increases in cross-sectional area as the air moves upwardly from the mouth of the fan duct. This, of course, is due to the fact that the vertical wall or center partition 69 defines with the sloping wall 14, in effect, a region in the shape of inverted right triangle as viewed in vertical section, so that air moving away from the bottom of the sump and upwardly is necessarily moving into a region of progressively increasing cross section. This brings about a measure of static increase in addition to that which takes place in the discharge ducts.

If, now, reference is made to FIG. 5, it will be observed that the horizontal spacing between the ducting portions such as duct portions 57, 61 and 62 on the left side of the unit and 58, 59 and 60 on the right side of the unit is such that the space between the duct portions is equal to or greater than the width of those portions themselves. To compute this spacing, it was found convenient for a unit about 12 feet long to use the following formula:

spacing between blower equals the length of the sump section minus with combined width of the blowers in that section divided by the number of blowers.

This allows a considerable amount of air space between the ducts, which has been found to contribute importantly to efficiency.

The space between the end fans of a group and the adjacent end wall of the sump is no less than half the width of the fan ducting. Arrows in FIG. 5 indicate how a portion of the air, somewhat baffled by the partition 69, tends to rise toward the top of the sump in the spaces between the fan ducts.

The air leaving the fan discharge cowls contacts the vertical wall opposite the cowl opening and some of the air is directed upward toward the wet deck section. The remainder of the air is turned 180.degree. and fills the space between blowers, as it expands upward through the V-sump section. The space between blowers should be so chosen so as to allow the correct proportion of air to enter and fill this space. It has been found that optimum cooling capacity is a function of blower width, spacing along the drive shaft, and the length/width ratio of the V-sump dimensions. For example, in a particular unit where the sump section was 12 feet long, 3 22 inches diameter blowers, each 21 inches wide were used with 27 inches spacing between them and 13 1/2 inches between the end blowers and the end walls of the sump. Deviation from optimum blower spacing as previously described, can cause unequal air distribution which seriously affects the cooling capacity of the equipment. As the air reaches the top of the V-sump section, its velocity has been reduced with an accompanying static pressure gain. For the most part, the air is distributed evenly when it reaches the top of the V-sump section, however, for a further refinement in air distribution before reaching the wet deck section, plenum chamber sections 170 and 71 may be used. These plenum chambers serve to equalize the small differences in air velocities leaving the top of the V-sump section.

Thus above the top of the sump section 11 and the lowermost layer of the fill there may be disposed one or more plenum chamber sections which are frames each constituting an air distribution module. The lower module bearing numeral 170 is shown in FIG. 1, and it can be seen that the unit consists of a rectangular frame defined by channel members with their flanges facing outwardly, the side members bearing numerals 73 and 74. Member 73 has secured on its inside edge an angle member of L section to form angle baffle 77. The horizontal portion of this angle baffle 77 extends horizontally usually about 2 to 3 inches in length toward the blower duct. When units are built "back-to-back" as in FIG. 2, the module 170 is constructed with a central member 75 with angle baffles 77 extending toward each blower assembly. Frame unit 71 is in all respects structurally similar to frame unit 170, except that the angle baffle 77 is omitted.

The effect of the two frames 170 and 71 is to create a large space, rectangular in plan, above the top of the V trough 11 and below the wet deck, the function and purpose of said space being to provide a region to effect more even distribution of the air entering the fill. The distribution of the air is also greatly improved by angle baffle 77. Thus the V shape of the trough 11, the provision of space-defining frames 170 and 71, and the angle baffle 77 all, both separately and together, contribute materially to the efficiency of the unit, create a uniform air flow and thus raise the cooling capacity substantially.

Claims

What is claimed is:

1. In a cooling tower having a region of fill, a chamber below said region, a sloping wall partially defining said chamber, said sloping wall having a port therethrough, a blower located outside said chamber and below said wall, means to guide air from said blower through said port into said chamber, and means including a curved portion extending adjacent the upper defining edge of said port into said chamber beyond the plane of said wall, said curved portion being boxed-in by side walls which also perform an air guiding function.

2. In a cooling tower having a region of fill, a chamber below said region, a sloping wall partially defining said chamber, said sloping wall having a port therethrough, a blower located outside said chamber and below said wall, means to guide air from said blower through said port into said chamber, said means including a curved portion extending adjacent the upper defining edge of said port into said chamber beyond the plane of said wall.

3. In a cooling tower having a region of fill, a chamber below said region, a sloping wall partially defining said chamber, said sloping wall having a port therethrough, means located outside said chamber below said wall to supply air under pressure through said port into said chamber, said means including a curved portion extending adjacent the upper defining edge of said port into said chamber beyond the plane of said wall.