GB1559329A - Air cooled atmospheric heat exchanger - Google Patents

Description

(54) AIR COOLED ATMOSPHERIC HEAT EXCHANGER (71) We, THE MARLEY COMPANY of 5800 Foxridge Drive, Mission, Kansas, United States of America, a corporation organised and existing under the laws of the State of Delaware, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to air cooled, atmospheric, indirect heat exchangers especially adapted for use in water cooling towers. The invention is concerned with synthetic resin heat exchangers.

Indirect heat exchange structures have been used for many years in a wide variety of applications. In general, water or other liquids to be cooled are passed through a plurality of separate structure of heat conductive material which are in turn contacted with an external cooling medium such as air.

The most common type of indirect exchanger is the so-called finned tube heat exchanger.

In these units a series of elongated, hollow, metallic tubes are provided, along with a number of generally transversely extending metallic fins which serve to increase the thermal effectiveness of the overall exchanger by increasing the total heat exchange area thereof. A hot liquid to be cooled (such as water) is directed through the exchanger tubes as external ambient derived airstreams are simultaneously directed past the fin and tube arrangement. This has the effect of cooling the hot fluid within the exchanger tubes without any direct contact between the hot fluid and the cooling air.

Indirect heat exchangers have also found wide application in cooling towers, especially in smaller towers used in conjunction with air conditioning equipment or the like. In most instances, simple finned tube heat exchangers of the type described above are ern ployed in these towers, and in general the cooling efficiencies thereof are sufficient to meet the relatively low heat load requirements normally imposed thereon. However, when larger heat loads must be handled, conventional indirect heat exchange towers (oftentimes referred to as "dry" towers) are generally too inefficient for practical use.

This is particularly troublesome since dry towers are especially advantageous in cases where it is necessary to limit the water consumption as well as the visible fog discharge or plume oftentimes encountered with large conventional evaporative or wet-type water cooling towers. The fact that dry towers avoid the problem of excess water usage and have essentially no fog or plume problem has led to proposals that the dry concept be employed in larger industrial sized towers, or that evaporative fill and indirect heat exchangers be incorporated into a single tower. The latter idea is especially attractive because the generally more efficient wet section of a dual-type tower can be utilized when ambient weather conditions permit, but such use can be lessened or eliminated completely as desired, with the consequent increased use of the dry section.All of these factors have led many researchers in the art of water cooling towers to investigate wider applications for indirect heat exchange towers, and as a consequence any developments aimed at increasing the water cooling efficiency of such dry towers could represent a major breakthrough in this art.

Another vexing problem associated with conventional dry towers, and especially those of relatively large capacity, stems from the high cost of the conventional heat exchangers used therein. These units are not only expensive in and of themselves, but require costly header constructions and the like for the delivery and return of the water being cooled. Therefore, the fact that evaporative water cooling towers are substantially more efficient, as well as being less expensive in meeting a given heat load requirement has deterred many from utilizing indirect heat exchange cooling towers in situations where their advantages would otherwise be- manifest.

It has also been proposed in the past to employ more or less conventional heat exchangers which are formed of synthetic resin materials such as the synthetic plastics.

This suggestion has many advantages, especially from the standpoint of cost, since synthetic resin materials are generally much less expensive and easier to fabricate, install and maintain than heat exchangers formed of metal. However, the most persistent objection to the use of synthetic resin exchangers results from the fact that heat conductivity of these materials is relatively low normally only about 1/100 that of metal. Thus, workers in the art have avoided using synthetic resin heat exchange apparatus because the latter have been through to be inefficient to the point of impracticality.According to the present invention there is provided heat exchange apparatus for cooling a hot liquid with ambient derived air comprising: a plurality of imperferate, thermally conductive, synthetic resin sheets rebent upon themselves to present individual transversely U-shaped structures which are oriented in upright. inverted, juxtaposed disposition in use with adjacent structures being joined to present a heat exchange pack, the upright sidewalls of each structure being located in horizontally spaced disposition, joined at the upper ends thereof by an overlying, integral top bight portion, and defining a substantially upright air passage for horizontal flow of ambient derived air therethrough which enters respective structures of the pack at one upright, open end face of each of the structures below respective top portions and exits from the upright, open opposite end face thereof, the upright sidewalls of adjacent structures also being in horizontally spaced relationship with means being provided to interconnect and seal the upright, adjacent side margins of proximal structures for preventing loss of liquid along substantially the entire longitudinal lengths thereof to cause the sidewalls of adjacent structures to define upright liquid conveying passages therebetween each of which has a substantially horizontally extending liquid inlet and a liquid discharge at the top and bottom respectively, said liquid passages alternating with the air passages and allowing liquid to gravitate downwardly therethrough in heat exchange relationship with air moving in cross flow relationship thereto through said air passages each of said sidewalls being provided with integral projecting segments which extend into the liquid receiving passages to increase the flow path of liquid gravitating downwardly on the surfaces of respective sidewalls and also extending into the area between the sidewalls defining each air passage for imparting turbulence to the air flowing through corresponding air passages; and elongated, horizontal support elements extending beneath a plurality of the top bight portions of the heat exchange structures in load bearing relationship thereto to fully support the pack.

The above configuration according to the present invention enables heat loads to be efficiently handled which heretofore were considered totally impractical for synthetic resin exchangers by virtue of the relatively low heat conductivity of synthetic resin materials. Further in an advantageous embodiment the construction ensures that initially hot quantities of water directed to the exchanger are measurably slowed during decending travel thereof by arranging for the flow to be along tortuous water paths of the structure defining sidewalls, so that ambient derived external cooling airstreams can be simultaneously directed for indirect thermal interchange with the hot water within the structures through the sidewalls of the latter.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings wherein: Figure 1 is a front elevational view of a synthetic resin, indirect heat exchanger pack in accordance with the present invention; Figure 2 is a side elevational view of the pack illustrated in Figure 1, with the upper right-hand corner of the pack broken away to expose the internal construction thereof; Figure 3 is a plan view of an initially flat sheet employed in the construction of the exchanger pack illustrated in Figures 1-2; Figure 4 is an enlarged, fragmentary plan view of an exchanger pack in accordance with the invention, shown with parts broken away for clarity; ; Figure 5 is a view in partial vertical section of a pair of stacked, nested heat exchanger packs operatively positioned within a cooling tower beneath the hot water distribution basin of the latter; Figure 6 is a fragmentary elevational view with parts broken away for clarity taken along line 6-6 of Figure 5 and illustrating the nested junction between the vertically aligned exchanger packs; Figure 7 is an enlarged, essentially schematic, fragmentary horizontal sectional view illustrating the manner in which the chevron channels of the heat exchanger sidewalls cause turbulence of cooling air flowing therepast; Figure 8 is an essentially schematic illustration of a modified form of the invention whrein water may be introduced into the air passages through means which also act as a support for the exchanger packs;; Figure 9 is a schematic sectional view further illustrating the construction of Figure 8; Figure 10 is a schematic representation of a mechanical draft crossflow cooling tower employing separate indirect heat exchange structures in accordance with the invention positioned atop conventional evaporative fill assemblies; Figure 11 is a schematic representation of a mechanical draft crossflow cooling tower employing opposed evaporative fill and indirect heat exchange sections respectively; Figure 12 is a schematic representation of a mechanical draft crossflow cooling tower employing opposed, indirect heat exchange sections in accordance with the invention;; Figure 13 is a schematic representation of a mechanical draft crossflow cooling tower having a two-pass indirect heat exchange construction with means for recirculating partially cooled volumes of hot water back to the heat exchange apparatus; Figure 14 is a schematic representation of a mechanical draft crossflow cooling tower employing an outermost evaporative fill section along with inner, indirect heat exchange apparatus; and Figure 15 is a graphical representation illustrating a psychrometric analysis of the water cooling and plume abatement qualities of the tower illustrated in Figure 14.

A heat exchanger pack 20 is depicted in Figures 1-2. Broadly, each pack 20 comprises a plurality of elongated, juxtaposed, integral synthetic resin members 22 of inverted, substantially U-shaped configuration which are interconnected along the respective vertical marginal edges of the sidewalls 28 thereof by means of adhesive solvents or pressure-heat sealing techniques to define a freestanding, structurally distinct pack 20. In this manner, a series of spaced, hollow, open-ended thin tube-like hot water receiving structures 24 are defined between the interconnected sidewalls of adjacent U-shaped members 22, with open-sided coling air passages 26 being defined by the transversely U-sely U-shaped configuration of each member 22. Thus, the passages 26 and structures 24 are in adjacent, alternating relationship throughout the width of pack 20.

Referring now to Figure 2, it will be seen that the opposed sidewalls 28 of each U-shaped member 22 are configured to present a series of normally horizontally extending corrugated chevron patterns 30 which are vertically aligned and project into the zone between the sidewall 28 to define a series of continuous, tortuous or serpentine flow paths 32 extending generally from the top of each sidewall section 28 to the bottom thereof. Although not depicted throughout the drawings for the sake of clarity, it is to be understood that the multiple chevron corrugation pattern extends substantially the entire height of each sidewall 28 of each member 22. In particular, the chevron patterns 30 are defined by elongated, pyramid-like, generally vertically extending ridges 44 (Figure 4) with corresponding depressions 46.It is to be noted that both the internal surfaces of the side-walls 28 and the external surfaces thereof are configured in the described chevron pattern. Thus, each ridge 44 on the internal surface of a sidewall corresponds to a depression on the external surface thereof. Furthermore, the angle of inclination of directly opposed ridges 44 and respective depressions 46 are in opposite directions (see upper right-hand corner of Figure 2) so that liquid flowing downwardly in the grooves of proximal vertical passage defining sidewalls 28 is deflected in different directions. As a consequence, where the tortuous liquid passages are subsantially filled with liquid flowing downwardly therethrough, the resultant flow vectors of the liquid discharging from each inclined flow stage is essentially vertical.This not only maintains equal flow distribution through the horizontal extent of the members 22 but most importantly assures that liquid flow from the bottom edge of each liquid conveying section is gene rally vertical rather than angular, thus avoiding maldistribution of liquid from one level to another, as is clear from Figure 6. In addition, the facing surfaces of the sidewall of each U-shaped member 22 are provided with a plurality of spaced, knob-like projections 34 which are arranged for abutting interconnection in order to maintain the spacing between respective sidewalls 28 of each U-shaped member 22.In this regard the relatively wide spacing between the sidewalls of each member 22 prevents the collections of dust or vegetation particles within the passages 26 (with consequent decrease in heat-transfer efficiency) and moreover facilitate cleaning thereof should leaves or the like be allowed to enter the passages. A further example of the use of a multiple chevron corrugation pattern similar in many respects to that illustrated herein can be found in U.S. Patent No.

3.733,063, issued May 15, 1973.

As shown in detail on Figures 4 and 5, each U-shaped member 22 includes an uppermost, smooth, rounded top portion 36 with corrugated sidewalls 28 8 depending there- from. Each sidewall 28 includes offset, vetically extending. generally planar connection panels 38 which define the lateral marginal edges thereof and permit the respective sidewalls 28 of adjacent U-shaped members 22 to be interconnected to define the hollow, hot water receiving structures 24 therebetween. As shown, the corrugated surface area of each sidewall 28 is recessed with respect to the marginal panels 38 so that a hollow, thin tube-like passage is presented between the interconnected sidewalls.Each sidewall 28 also includes a pair of laterally spaced, vertically extending connection or stiffening ribs 40 on which are likewise offset from the corrugated surface thereof and adapted to be adhesively secured to corresponding ribs 40 on another sidewall section 28. In this man ner, the hot water receiving structure 24 is divided into a number of discrete, identical, elongated hot water passages, which for exemplary purposes have been shown as separate channels. The ribs 40 significantly increase the structural rigidity of the sidewalls 28 and serve to prevent the characteristic, gravity-induced "creep" of the PVC material, which can be especially troublesome in the case of corrugated sheets.

It will also be seen that the terminal ends of each exchanger pack 20 are defined by what can be thought of as approximately one-half of a U-shaped member 22. In this respect each terminal member 48 includes an upstanding. planar connection panel 50 extending above the remainder of pack 20, as well as a sidewall 52 which is identical in very respect with each sidewall 28 of the U-shaped members 22, in order to permit mating attachment of the terminal members 48 to complete pack 20. Moreover, the sidewalls of each U-shaped member 22 and terminal members 48 are laterally constricted as at 54 so that the open-top hot water receiving structures 24 defined between respective interconnected sidewalls 28 are of somewhat lesser width than the main body of the structures.The bottom of each sidewall 28 is also constricted as at 56 and angularly cut as at 57 so that the lower end of each exchanger pack 20 will complementally fit within and nest with the upper end of another exchanger pack, with the respective hot water receiving passages presented by structures 24 in each of the packs being in communication.

The exchanger packs 20 described above are preferably fabricated from a series of initially flat. vacuum-formed, integral sheets 58 depicted in figure 3. Each sheet 58 includes a pair of chevron-ribbed sidewall sections 28 as well as the generally planar midsection 36 adapted to define the uppermost rounded portion of each U-shaped member 22. The left-hand end of each sheet 58 terminates in a generally flat, uncorrugated panel section 50. In practice, the intermediate, generally U-shaped members of each pack 20 are formed from a length of shet 58 referred to by the dimension "A", with the panel section 50 being removed.

Dimension "B" (with panel section 50 intact) is employed for the leftmost end sheet 48 of a pack as illustrated in Figure 1, while dimension "C" refers to the right-hand end sheet of the pack wherein section 36 serves as the upstanding planar section 50 thereof.

The sheets used in the formation of each pack 20 are in each case cut along one of the dotted lines depicted in the drawings, in order to ensure that each pack is of uniform shape and dimension.

Referring now to Figures 5 and 6, the indirect heat exchange apparatus hereof is shown in operative disposition in a crossflow cooling tower construction. The cooling tower is shown only fragmentarily but includes an upper hot water distribution basin 60 having a plurality of water delivery openings 62 therein for permitting hot water to gravitate toward the indirect heat exchange structure disposed therebelow. A pair of heat exchanger packs 20 are illustrated in the Figure with the respective packs being in stacked, nested relationship, and the air passages 26 thereof oriented for receiving ambient derived crossflowing cooling air currents. In this regard, a skeletal framework including support members 64, 66, 68 and 70 is employed for tension ably supporting the packs 20 in operative disposition beneath basin 60.Horizontally extending support elements 66 and 70 support a series of spaced. rounded top beams 72 which are adapted to complementally fit within the uppermost rounded portion 36 of each U-shaped member 22 making up the respective packs 20. In practice, it has been determined that it is only necessary to positively support every other U-shaped member 22 by means of a beam 72. Installation of each pack 20 may be completed if desired by stapling the upright terminal panels 50 thereof to adjacent structural members, for example as at 74.

Referring specifically to Figure 6, it will be seen that the constricted bottom of each of the spaced sidewalls 28 defining the spaced, hot water receiving structures 24 is nestably received within the complemental upper ends of the corresponding hot water receiving structure 24 of the pack 20 therebelow.

Thus, the elongated hot wate receiving structures 24 of each pack 20 are in full communication so that hot water delivered to the uppermost pack 20 flows continuously through all packs therebelow. In addition, although only two packs are illustrated in Figure 6, it is to be understood that virtually any number of such packs can be employed in practice, depending principally upon the desired use and heat load requirements to be met.

In use, hot water to be cooled is initially directed to basin structure 60 and allowed to descend through openings 62. By virtue of the fact that the uppermost end of upper pack 20 is spaced somewhat below basin 60, such initially hot water must descend through the air to reach the indirect heat exchange apparatus. When the latter is reached, the volumes of water flow down the respective hot water receiving structures 24 defined by the interconnected U-shaped members 22.

In order to prevent undue channelling of the water, the rounded tops of the members 22 are preferably positioned directly below the openings 62 so that the water must impinge upon the rounded sections before flowing into the structures 24. In this regard, actual tests have demonstrated that the descending water entering the structures 24 causes a homogenous pattern of air bubbles to be entrained therewithin (arrow 75) by a venturi effect, so that the air and water mixture actually entering the respective structures 24 (arrow 76) contains a measurable amount of entrained air. Air entrainment is most pronounced when the water flow rates to the exchanger pack are sufficient to effect a near seal of the water-receiving structures 24, thereby precluding the possibility of venting the pack over its full height.Thus, during low water flow conditions the venturi-induced air entrainment is not as effective, and cooling is due primarily to film-type surface heat exchange. In any event, the entrainment phenomenon when applicable is important for a number of reasons.

Firstly, entrained air has the effect of slowing the descent of the water through the hot water receiving structures 24 and moreover ensures that the water travels down the continous, serpentine hot water paths 32 defined by the chevron-arranged corrugations discussed above. This tortuous water travel is illustrated by arrows 78 of Figure 6. As can be appreciated, the intimate flowing contact of the hot water along the defining sidewalls 28 of structures 24 enhances the cooling efficiency of the overall exchanger since essentially all cooling is through the prime heat exchange surface of the sidewalls 28. Just as importantly however, the entrained air within the water descending through the structures 24 does not reach a level sufficient to cause inward collapse of the relatively thin sidewalls 28.That is, the descending volumes of hot water produce a slight negative pressure within each structure 24 by virtue of the venturi type flow thereof. Without entrained air within such descending water, the sidewalls of the respective structures 24 could be subjected to negative pressure levels sufficient to cause their collapse. It should also be noted that the slight venturiinduced negative pressures within the structures 24 are important in preventing untoward splash-out of water therefrom. This is especially significant in the case of synthetic resin exchangers since pinholes made during fabrication thereof, and minor leaks at the seams of such units, could present serious problems if the exchangers were operated at positive pressures, as is common with metallic finned tube constructions.

In order to adequately cool the hot water gravitating through the exchanger packs 20, ambient derived cooling airstreams are induced to pass along the open passages 26 between the spaced structures 24 by means of mechanical fans or the stack effect of a hyperbolic natural draft tower, as is well known in this art. Heat from the hot water is thus passed through the thin PVC sidewalls 28 to the cross-flowing cooling airstreams to effect the desired cooling of the initially hot water. In this respect, the chevron corrugations of the sidewalls are very important in enhancing the ultimate heat-transfer efficiency of the exchanger.This stems not only from the effects mentioned above (i.e., minimizing channeling of the water by ensuring that the latter travels along the internal serpentine flow paths), but also in causing turbulence of the cooling airstreams flowing past the external surfaces of the sidewalls 28.

this effect is depicted schematically in Figure 7 and illustrates that the undulating, chevron corrugated outer wall surfaces of each of the structures 24 causes eddies and other types of turbulence (illustrated by arrows 79) which would not obtain if the external wall surfaces were substantially planar in configuration. As can be appreciated, this turbulence increases the effective thermal contact between the cooling air and the sidewalls 28 of the respective structures 24, so that the hot water within the latter is more efficiently cooled.

It will also be recognized that the present exchanger apparatus presents a simplified heat flow path as compared with conventional finned tube exchangers. That is, substantially the entire surface area of each sidewall 28 is prime heat exchange area, that is, in direct simultaneous contact with the cooling air and hot water. By way of comparison, the fins of conventional finned tube exchangers (which carry the principal portion of the heat transferred) are so-called secondary heat exchange surfaces because they are not in direct, simultaneous contact with the liquid being cooled and the external cooling medium. In the present invention for example, heat must flow only across the relatively thin (about 15 mils) sidewalls 28.This of course has the effect of minimizing any heat transfer problems stemming from the fact that the preferred polyvinyl chloride fabrication material is of low heat conductivity as compared to metal.

Another embodiment of the present invention is depicted in Figures 8 and 9. In this instance, a hot water distribution basin 80 having delivery openings 82 therein is provided with a heat exchanger pack 20 suspended therebelow. In this case however, a series of elongated hot water delivery pipes 84 are positioned within the confines of the U-shaped members 22 and are employed for suspending the pack 20 in place of the support beams 72 illustrated in Figures 5-6. Each pipe 84 is provided with a plurality of spaced delivery opening or nozzles 86 along the length thereof, and the pipes are in operative communication with a common delivery header 88.Hence, during operation of indirect cooling section of the cooling tower as explained, it is also possible to provide a degree of direct thermal innerchange between descending water delivered through the support pipes 84 and the crossflowing cooling air currents passing through passages 26. This feature is especially significant in that it permits more flexibility in tower operation and enables a given size tower to handle a greater heat load than would be possible without the use of delivery pipes 84.

The inherent operational flexibility of the present indirect heat exchangers also permits use thereof in a number of specialized situations. Referring specifically to Figures 10-14, representative examples of this operational flexibility are illustrated in the context of a variety of cooling towers. In each case, a mechanical draft, crossflow cooling tower 90 is illustrated with varying types of heat exchange apparatus employed therein. Each tower 90 includes hot water distribution basin structure 92 (142 in Figure 14), a cold water collection basin 94 therebelow, and a central, mechanically powered fan 96 circumscribed by an upright, venturi-shaped cylinder 98 positioned atop the tower on an apertured fan deck 99 for inducing ambient derived air currents through the heat exchange apparatus of the tower in crossflowing relationship thereto.A central plenum chamber 100 is defined between respective opposed sections of the heat exchanger apparatus of the tower (which may be annular in form or in separate, opposed sections as illustrated).

Referring now to Figure 10. it will be seen that a pair of stacked, nested exchanger packs 20 are provided on each side of the tower and situated directly above conventional opposed evaporative fill structure sections 102. the latter having drift eliminator structure 104 on the outlet faces thereof and a series of stacked, inclined inlet louvers 105 on the inlet faces thereof. In the operation of this tower, hot water is delivered through conventional header structures 106 and descends through basins 92 and the indirect heat exchanges packs 20 as described hereinabove. After initial cooling of the hot water in the indirect section of the tower, the water descends into secondary distribution basins 108 positioned beneath the pack and above the fill structure sections 102.At this point the water flows down through the evaporator sections of the tower for direct thermal interchange with the crossflowing air currents drawn therethrough (and through packs 20) by means of fan 96. It is to be appreciated in this respect that any one of a number of conventional evaporative fill structures can be employed in this context for the purpose of increasing the surface area of the gravitating water for enhanced, more efficient thermal contact with the crossflowing cooling airstreams. Finally, cooled water collected in basin 94 is directed through pipe 110 for reuse or disposal.

Figure 12 illustrates a purely dry tower employing a pair of spaced, opposed heat exchange sections, each composed of a series of vertically stacked, nested heat exchanger packs 20. In this instance, the cooling is purely by indirect thermal interchange and is accomplished in accordance with the methods fully described above.

Another type of dry cooling tower construction is illustrated in Figure 13. In this instance plenum chamber 100 is defined by a pair of spaced, opposed indirect heat exchanger assemblies 112. Each assembly 112 comprises two side-by-side sets of vertically stacked, nested heat exchanger packs 20. In addition, separate distribution basins 92a and 92b, and collection basins 94a and 94b, are provided for the outer and inner series of nested packs 20, along with separate distribution header structures 106a and 106b. In operation, hot water is initially delivered through line 114 to the inner distribution headers 106b for descending travel through the inner indirect heat exchange packs 20. After initial passage through these packs, the partially cooled water collected in basin 92b is allowed to pass therefrom through recirculation pipes 118 and 120.A pump 122 is interposed within line 120 and directs the partially cooled water back to the distribution headers 106a at the top of the tower. The partially cooled water is thus allowed to descend through the outermost packs 20 and is ultimately collected within the outer basin 94a for ultimate return through line 126. This type of tower is particularly advantageous in that the amount of cooling of the initially hot volumes of water can be more precisely controlled. For example, during light thermal load or cold weather operating conditions it may be necessary only to run the water through one path of the tower and not recirculate the same for a second pass.

The tower depicted in Figure 11 is espe cially adapted for situations where plume abatement is a major concern. The tower employs a first dry exchange section defined by stacked packs 20 with an evaporative fill section 126 in opposed, facing relationship thereto. Separate headers 128 and 130 are provided for selectively directing quantities of hot water to the respective heat exchange sections of the tower. In the operation of this unit, the amount of evaporative cooling (and thereby, water consumption) can be precisely controlled, or when ambient weather conditions are such that fog formation becomes troublesome, the tower can be utilized essentially as a dry unit with little or no wet cooling.However, when water consumption or fog problems are not of concern, a substantial amount of the hot water to be cooled can be directed to the evaporative section for the most efficient cooling thereof.

In addition, in the case of the Figure 11 tower the crossflowing induced airstreams 132 and 134 leaving dry and wet exchange sections of the tower come into direct, comingling relationship so that the air leaving the tower through stack 98 is effectively admixed to thus minimize the possibility of producing a visible fog plume at the outlet of the tower.

Yet another tower application is illustrated in Figure 14 wherein multiple pack, indirect heat exchange sections 136 are positioned inboard of adjacent, outermost evaporative fill sections 138 so that air leaving the latter will thereafter pass in serial order through the dry section of the tower.

Separate distribution basins 140 and 142 are provided for the wet and dry sections respectively, along with separate headers 144 and 146. During operation of this tower, opposed, crossflowing cooling airstreams (represented by arrows 148) first pass through the outer evaporative sections 138 and thence through the adjacent dry sections 136 before admixing in plenum chamber 100 and being returned to the atmosphere through stack 98.

In order to demonstrate the fog abatement qualities of the tower illustrated in Figure 14, and particularly with respect to the use of the indirect heat exchangers hereof, the graphical representation of Figure 15 is presented.

This graph illustrates a psychrometric analysis of the water cooling performance of the depicted series-path tower and demonstrates that during normal operations no visible fog plume is produced at the outlet thereof. Referring specifically to the graph and Figure 14, point P, represents the average heat and mass balance conduction of the ambient air before entering the cooling tower. Point P2 represents this conduction for the air leaving the wet section of the tower, and point P3 represents air quality where the air leaves the dry section of the tower (comprised of stacked heat exchanger packs 20).

The arrow line 149 extending from point P3 to P1 represents the heat and mass balance conduction of a typical effluent air mixture as discharged from stack 98, and indicates that as the air is discharged, it blends with ambient air and finally reverts to ambient quality (i.e., point Pl) at some distance from the tower outlet. It is important to note that arrow line 149 always remains below the saturation curve illustrated on the graph; this therefore confirms that no visible fog or plume will be formed adjacent the outlet of the cooling tower. Hence it is clear that the series-path tower of Figure 14 utilizing the exchanger packs 20 hereof is capable of effectively cooling hot water without objectionable fog formation.

It will be appreciated from the foregoing that use of the synthetic resin exchangers hereof is highly advantageous, even in very large cooling towers capable of handling high heat loads. The exchangers are low in cost, corrosion-free (which permits cooling of brackish or salt water) and non-fouling to facilitate maintenance thereof. Most important however, the cooling effectiveness is more than doubled when compared with conventional metal finned-tube constructions.

Reference is made to the applicants copending application No. 81/79 (Serial No.

1559330) which describes and claims water cooling apparatus as above described.

WHAT WE CLAIM IS: 1. Heat exchange apparatus for cooling a hot liquid with ambient derived air comprising: a plurality of imperferate, thermally conductive, synthetic resin sheets rebent upon themselves to present individual transversely U-shaped structures which are oriented in upright, inverted, juxtaposed disposition in use with adjacent structures being joined to present a heat exchange pack, the upright sidewalls of each structure being located in horizontally spaced disposition, joined at the upper ends thereof by an overlying, integral top bight portion, and defining a substantially upright air passage for horizontal flow of ambient derived air therethrough which enters respective structures of the pack at one upright, open end face of each of the structures below respective top portions and exits from the upright, open opposite end face thereof, the upright sidewalls of adjacent structures also being in horizontally spaced relationship with means being provided to interconnect and seal the upright, adjacent side margins of proximal structures for preventing loss of liquid along substantially the entire longitudinal lengths thereof to cause the sidewalls of adjacent structures to define upright liquid conveying passages therebetween each of which has a substantially horizontally extending liquid inlet and a liquid discharge at the top and bottom respectively, said liquid passages alternating with the air passages and allowing liquid to gravitate downwardly therethrough in heat exchange relationship with air moving in cross flow relationship thereto through said air passages each of said sidewalls being provided with integral projecting segments which extend into the liquid receiving passages to increase the flow path of liquid

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. unit, the amount of evaporative cooling (and thereby, water consumption) can be precisely controlled, or when ambient weather conditions are such that fog formation becomes troublesome, the tower can be utilized essentially as a dry unit with little or no wet cooling. However, when water consumption or fog problems are not of concern, a substantial amount of the hot water to be cooled can be directed to the evaporative section for the most efficient cooling thereof. In addition, in the case of the Figure 11 tower the crossflowing induced airstreams 132 and 134 leaving dry and wet exchange sections of the tower come into direct, comingling relationship so that the air leaving the tower through stack 98 is effectively admixed to thus minimize the possibility of producing a visible fog plume at the outlet of the tower. Yet another tower application is illustrated in Figure 14 wherein multiple pack, indirect heat exchange sections 136 are positioned inboard of adjacent, outermost evaporative fill sections 138 so that air leaving the latter will thereafter pass in serial order through the dry section of the tower. Separate distribution basins 140 and 142 are provided for the wet and dry sections respectively, along with separate headers 144 and 146. During operation of this tower, opposed, crossflowing cooling airstreams (represented by arrows 148) first pass through the outer evaporative sections 138 and thence through the adjacent dry sections 136 before admixing in plenum chamber 100 and being returned to the atmosphere through stack 98. In order to demonstrate the fog abatement qualities of the tower illustrated in Figure 14, and particularly with respect to the use of the indirect heat exchangers hereof, the graphical representation of Figure 15 is presented. This graph illustrates a psychrometric analysis of the water cooling performance of the depicted series-path tower and demonstrates that during normal operations no visible fog plume is produced at the outlet thereof. Referring specifically to the graph and Figure 14, point P, represents the average heat and mass balance conduction of the ambient air before entering the cooling tower. Point P2 represents this conduction for the air leaving the wet section of the tower, and point P3 represents air quality where the air leaves the dry section of the tower (comprised of stacked heat exchanger packs 20). The arrow line 149 extending from point P3 to P1 represents the heat and mass balance conduction of a typical effluent air mixture as discharged from stack 98, and indicates that as the air is discharged, it blends with ambient air and finally reverts to ambient quality (i.e., point Pl) at some distance from the tower outlet. It is important to note that arrow line 149 always remains below the saturation curve illustrated on the graph; this therefore confirms that no visible fog or plume will be formed adjacent the outlet of the cooling tower. Hence it is clear that the series-path tower of Figure 14 utilizing the exchanger packs 20 hereof is capable of effectively cooling hot water without objectionable fog formation. It will be appreciated from the foregoing that use of the synthetic resin exchangers hereof is highly advantageous, even in very large cooling towers capable of handling high heat loads. The exchangers are low in cost, corrosion-free (which permits cooling of brackish or salt water) and non-fouling to facilitate maintenance thereof. Most important however, the cooling effectiveness is more than doubled when compared with conventional metal finned-tube constructions. Reference is made to the applicants copending application No. 81/79 (Serial No. 1559330) which describes and claims water cooling apparatus as above described. WHAT WE CLAIM IS:

1. Heat exchange apparatus for cooling a hot liquid with ambient derived air comprising: a plurality of imperferate, thermally conductive, synthetic resin sheets rebent upon themselves to present individual transversely U-shaped structures which are oriented in upright, inverted, juxtaposed disposition in use with adjacent structures being joined to present a heat exchange pack, the upright sidewalls of each structure being located in horizontally spaced disposition, joined at the upper ends thereof by an overlying, integral top bight portion, and defining a substantially upright air passage for horizontal flow of ambient derived air therethrough which enters respective structures of the pack at one upright, open end face of each of the structures below respective top portions and exits from the upright, open opposite end face thereof, the upright sidewalls of adjacent structures also being in horizontally spaced relationship with means being provided to interconnect and seal the upright, adjacent side margins of proximal structures for preventing loss of liquid along substantially the entire longitudinal lengths thereof to cause the sidewalls of adjacent structures to define upright liquid conveying passages therebetween each of which has a substantially horizontally extending liquid inlet and a liquid discharge at the top and bottom respectively, said liquid passages alternating with the air passages and allowing liquid to gravitate downwardly therethrough in heat exchange relationship with air moving in cross flow relationship thereto through said air passages each of said sidewalls being provided with integral projecting segments which extend into the liquid receiving passages to increase the flow path of liquid

gravitating downwardly. On the surfaces of respective sidealls and also extending into the area between the sidewalls defining each air passage for imparting turbulence to the air flowing through corresponding air passages; and elongated, horizontal support elements extending beneath a plurality of the top bight portions of the heat exchange structures in load bearing relationship thereto to fully support the pack.

2. Heat exchange apparatus as claimed in Claim 1, wherein said segments extending into the liquid and air passages include abutting projections on the opposed faces of the sidewalls of each U-shaped structure remote from the adjacent U-shaped structures for maintaining the spacing between said sidewalls.

3. Heat exchange apparatus as claimed in Claim 1 or 2 wherein said proximal sidewalls of said respective structures are also interconnected along spaced, vertically extending ribs in order to divide said liquid passages into discrete sections.

4. Heat exchange apparatus as claimed in any one of the preceding claims, wherein the corresponding interior and exterior faces of said sidewalls are provided with surface undulations presenting a tortuous path configuration.

5. Heat exchange apparatus as claimed in any one of the preceding Claims, wherein said extensions from the sidewalls present a series of normally horizontally extending chevron patterns which are configured to define continous, tortuous, vertically extending paths.

6. Heat exchange apparatus as claimed in any one of the preceding Claims, wherein the synthetic resin sheets defining said sidewalls are formed of relatively thin preformed synthetic resin material sheets.

7. Heat exchange apparatus as claimed in any of the preceding Claims, wherein the sidewalls of said structures have sections defining the bottom discharges thereof which are configured to complementally nest within the top inlets of the structures of another of said packs therebelow.

8. Heat exchange apparatus as set forth in Claim 6, wherein said material is polyvinyl chloride.

9. Heat exchange apparatus substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 7 or these Figures as modified by Figures 8 and 9 of the accompanying drawings.