US3430691A - High-capacity air-cooled heat exchanger - Google Patents

Description

March 4, 1969 G. SCHOLL 3,430,691

HIGH-CAPACITY AIR'COOLED HEAT EXCHANG ER Filed Oct. 31 1966 Sheet of 2 I INVENTOR. $4 177 fer f e/3672 March 4,- 1969 e. SCHOLL HIGH-CAPACITYAIN COOLED HEAT EXCHANGER Z of 2 Sheet Filed Oct. 31, 1966 illdlllll lilllllllillllllllll lornvilriiilnlll irlllllilvill llllilllllli'll I lilllllfllllllilll IIIII'IIIIIII I II INVENTOR. 6 1)): I JcfiJ/Y United States Patent 3,430,691 HIGH-CAPACITY AIR-COOLED HEAT EXCHANGER Giinter Schiill, Mulbergerstrasse 21a, Esslingen (Neckar), Germany Filed Oct. 31, 1966, Ser. No. 590,875 Claims priority, application Germany, Nov. 5, 1965, Sch 37,976 US. Cl. 165122 Claims Int. Cl. FZSf 13/12 ABSTRACT OF THE DISCLOSURE Large-capacity heat exchanger associated with a power plant or the like, the exchanger including a movable impeller whose vanes are mounted on a pair of coaxial circular rails supported by two annular arrays of rollers; some of these rollers are motor-driven to impart rotation to the impeller.

The present invention relates to a high-capacity aircooled heat exchanger which consists of a ventilator and a large number of heat-exchanging elements which are disposed either in front of or behind the ventilator and either above or below the same.

The progressive increase in the dimensions and output of power plants and also of manufacturing plants, especially of the chemical industry, requires ever greater quantities of accumulated heat to be dissipated, even though for economic reasons they occur at temperatures which are not very much higher than the outside temperature. In the past, these large quantities of heat were usually conducted into rivers or, if no rivers were available near the plants, they were dissipated by means of cooling towers provided with sprinkling systems. The heat-absorption capacity of rivers is, however, rather limited for biological reasons and in many cases already exhausted, and the employment of cooling towers with sprinkling systems is likewise limited because of the large quantities of water which are lost in these apparatus by evaporation.

The problem of dissipating large quantities of heat may also be solved by the use of atmospheric air which is available in unlimited amounts. However, since the thermal capacity of air is extremely low as compared with that of water, it is necessary to drive huge quantities of air through such an air cooler. According to one known design of such an air cooler, this has been accomplished by employing a large number of axial-flow fans for either blowing or drawing the outside air through the channels between the heat-exchanging elements which preferably consist of ribbed pipes and together form an inclined roof. Such air coolers are, however, very uneconomical because of the high cost of the axial-flow fans and the amount of energy which they require.

It is also known to dissipate these large quantities of heat by mounting the heat-exchanging elements at the lower part of a giant circular chimney and to ventilate them without fans by the draft of the heated air within the chimney. In order to attain a suificient differential pressure, these chimneys are required to have a height of 100 meters and more, and since in view of the size of a large modern power plant or the like the quantities of air which have to be conveyed amount to 100 million cubic meters per hour and more, these chimneys have to 3,430,691 Patented Mar. 4, 1969 have a diameter of meters and more. Aside from the tremendous cost of building such chimneys, these socalled self-ventilating coolers also have especially the disadvantage that their cooling power depends upon the prevailing outer-atmospheric conditions.

It is an object of the present invention to provide a high-capacity air-cooled heat exchanger of the type first mentioned above which may be manufactured and installed as well as operated at a relatively low cost since for attaining the high rate of flow of air which has to be passed through the heat-exchanging elements of this apparatus it is not necessary to provide either a high chimney or a large number of individual fans, there being required only a single large ventilator which may be driven at a low speed.

According to the invention, this object is attained by providing the ventilator of the new heat exchanger in the form of one or several large impellers whose blades are mounted on one or several coaxial circular rails which are supported on and movable along a plurality of rollers which are disposed in fixed positions spaced from each other in a circular arrangement and at least some of which may be motor-driven for driving the large impeller.

The heat exchanger according to the invention has the great advantage of being composed of extremely simple and inexpensive elements and of requiring relatively little power for its operation and for overcoming the frictional losses which occur between the rails of the impeller and their supporting or driving rollers. While the minimum diameter of this annular heat exchanger is generally larger than the maximum diameter of an axialflow fan, it may easily be made of such a large diameter that an entire power plant may be disposed at the inside thereof so that its ventilator will revolve completely around this plant. The heat exchanger according to the invention may therefore be built for any rate of flow and is particularly of value when the output of an axial-flow fan is insufficient.

The stationary heat-exchanging elements of this apparatus, through which the medium to be cooled is passed, may be constituted by a large number of hollow vanes which may have a flat boxlike cross section or a curved or arcuate shape.

In order to utilize the velocity at which the air emerges with a high tangential component from the blades of the impeller for the purpose of increasing the heat transfer, it is another feature of the invention to design the stationary heat-exchanging vanes so that their ends facing the impeller are curved and tapered at an acute angle to a point in the direction opposite to the direction of rotation of the impeller.

Furthermore, by also tapering the outer ends of the hollow heat-exchanging vanes at an acute angle to a point or by connecting additional guide vanes thereto, it is possible to increase the width of the air channels between these vanes so as to produce a diffuser effect so that the high velocity of the air within the heat exchanger before its discharge into the atmosphere will be at least partly converted into a static pressure and will thereby reduce the amount of energy which is required for operating the heat exchanger.

The features and advantages of the present invention will become more clearly apparent from the following detailed description thereof which is to be read with 3 reference to the accompanying diagrammatic drawing in which:

FIGURE 1 shows a vertical section of a heat exchanger according to a first embodiment of the invention;

FIGURE 2 shows a vertical section of a heat exchanger according to a second embodiment of the invention; while FIGURES 3 to 5 show sections of the rotatable impeller and of three difierent embodiments of the stationary heat-exchanging elements according to FIGURES l and 2.

In the drawing, FIGURE 1 shows a vertical section of a horizontal type of heat exchanger according to the invention which comprises an annular array of hollow heatexchanging elements 1 which are connected to an outer circular inlet pipe 21 and an inner circular outlet pipe 21" and through which the fluid to be cooled is conducted. The heat exchanger further comprises an annular impeller 2 underneath the array of heat-exchanging elements 1, consisting of a circular row of blades which span two pairs of concentric rings 22', 22" and 23' and 23". The impeller is mounted on a pair of coaxial circular rails 3', 3" of different diameters supported on and movable along a plurality of inner and outer rollers 4', 4" which are mounted in fixed positions in circular arrays and some of which are driven directly by electric motors 5 so as to drive the impeller 2 on its rails 3, 3" along these rollers. The axis of rotation of the ap aratus has been indicated at A and may be located at any desired radial distance from the inner rail 3, e.g. as determined by the dimensions of a power plant or the like surrounded by the heat exchanger. The array of heat-exchanging elements 1 together with the inlet and outlet pipes 21' and 21" and the rollers 4', 4" carrying the annular impeller 2 on its rails 3, 3" as well as the motors 5 (only one shown) driving some of these rollers are mounted on high posts 6', 6" so as to permit the cooling air to flow freely in the direction of the arrows toward the impeller 2 and through the blades thereof. This also permits pedestrians and vehicles to pass freely underneath the large heat exchanger toward and from the power plant located inside the heat exchanger, and it also permits underpasses for roads and siding tracks to lead underneath the heat exchanger to and from the power plant.

FIGURE 2 illustrates a vertical type of heat exchanger according to the invention. Its axis of rotation is likewise spaced at any suitable radial distance from the periphery of the structure. The impeller 2a, whose blades are again mounted between rings 22a, 22a" on a pair of circular rails 3a, 3a" which in this case are of equal diameters,

is adapted to run along and to be guided by the rollers 4a, 4a" some of which are driven by electric motors 5a. The direction of flow of the cooling air is again indicated by arrows as in FIGURE 1. The inlet and outlet pipes 21a and 21a" bracketing the array of hollow heat-exchanging elements 1a are likewise of equal diameters. Thus, the blades 2a of the impeller and the ducts 1a between conduits 21a, 21a" define a pair of concentric cylinders centered on the axis of the vertically spaced coils 3a, 3a".

FIGURES 3 to 5 show diagrammatic sections of the annular impeller with its endless row of blades together with three different embodiments of the heat-exchanging elements or ducts which are connected to the inlet and outlet pipes shown in FIGURES 1 and 2 so as to lie in generally axial planes. The impeller 2b, 2c or 2d, with its mounting rings 22!), 220 or 22d, is adapted to rotate in the direction indicated by the arrows. The heat-exefinging elements are in the form of hollow guide vanes through which the fluid to be cooled is conducted, these vanes having elongate profiles generally parallel to the axis of rotation. The heat-exchanging elements according to FIGURE 3 form hollow box-shaped vanes 1b whose lower ends 11 facing the movable impeller 2b are curved so that the air currents emerging from the impeller will flow as freely as possible and without change of its velocity between the vanes. At the air-outlet side, however, the outer ends 12 of the vanes 1b are tapered at an acute angle so that the air channels between them increase in width and produce a diifuser eflect.

In order to stabilize the vanes 1b to prevent them from being crushed in the event that an underpressure occurs therein, their walls may be braced by inserting corrugated plates 13 therein. If, on the other hand, an excessive pressure by the fluid to be cooled might occur within the vanes, they may be braced by inserting similar corrugated plates into the air channels between the vanes 1b.

FIGURE 4 shows diagrammatically a modification of the hollow vanes which in this case are plates 1c of undulating profile, made from corrugated sheet metal, and may easily be given a sufiicient compressive strength even though they consist of a thin material. The acutely ta pered ends 111 (proximal to the impeller) and 112 (remote from the impeller) of the vanes according to FIG- URE 4 serve for the same purpose as described with reference to FIGURE 3.

FIGURE 5 shows diagrammatically still another modification of the stationary heat-exchanging elements above or adjacent to annular impeller 2d which again consists of an endless row of blades. The heat-exchanging elements consist in this case of two rows of descent-shaped hollow vanes 2d, 2d" of mutually opposite curvature, through which the fluid to be cooled is conducted, and of a row of guide blades 14 which reduce the discharge velocity of the air and convert the same into a static pressure. The convergent lower ends 211 of the vanes 7c, proximal to the impeller, point again in the direction of the oncoming blades 2d.

The large ventilators according to the invention may also be employed in combination with cooling towers of a conventional type which are provided with sprinkling systems so as to ventilate such towers more effectively and increase their efiiciency considerably. Such ventilators may also be easily installed on older cooling towers which have already been in operation for some time.

Although my invention has been illustrated and described with reference to the preferred embodiments thereof, I wish to have it understood that it is in no way limited to the details of such embodiments but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed my invention, I claim:

1. A heat exchanger comprising a stationary array of peripherally spaced ducts centered on an axis, said ducts being disposed in generally axial planes; conduit means connected to said ducts for passing therethrough a fluid to be cooled; an impeller centered on and rotatable about said axis, said impeller including a pair of coaxial annular circular rails and an annular array of blades spanning said rails adjacent said ducts; a pair of concentric annular arrays of supporting rollers for said impeller, each of said rails resting on a respective array of said rollers; and drive means for rotating at least certain of said rollers to impart motion to said impeller for circulating air through the spaces between said ducts.

2. A heat exchanger as defined in claim 1 wherein said rails lie concentrically in a substantially horizontal plane.

3. A heat exchanger as defined in claim 2 wherein said ducts are disposed above said impeller.

4. A heat exchanger as defined in claim 3, further comprising two concentric sets of mounting posts for said rollers arrayed about said axis, said impeller being held sufficiently high above ground on said posts for providing a thoroughfare for people and vehicles.

5. A heat exchanger as defined in claim 1 wherein said rails are of substantially identical diameters and lie in vertically spaced generally horizontal planes, said ducts and said blades defining two concentric cylinders.

6. A heat exchanger as defined in claim 1 wherein said ducts are in the form of hollow vanes with elongate profiles.

7. A heat exchanger as defined in claim 6 wherein said vanes are internally provided with reinforcing ribs.

8. A heat exchanger as defined in claim 6 wherein said profiles have tapering ends proximal to and remote from said impeller, said proximal ends pointing in the direction of the oncoming blades thereof.

9. A heat exchanger as defined in claim 8, further comprising a set of solid stationary guide vanes disposed adjacent said remote ends of said hollow vanes.

10. A heat exchanger as defined in claim 6, wherein said vanes are divided into two parallel groups spaced along said axis, the vanes of each group having a generally crescent-shaped profile of a curvature opposite that of the vanes of the other group.

References Cited UNITED STATES PATENTS 2,085,282 6/1937 Waterval l03l 11 X 2,470,794 5/1949 Snyder 10394 X 3,280,900 10/1966 Wartenberg 165-122 10 ROBERT A. OLEARY, Primary Examiner.

THEOPHIL W. STREULE, Assistant Examiner.

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