US3225824A

US3225824A - Air-cooled heat exchanger for cooling liquid media

Info

Publication number: US3225824A
Application number: US311153A
Authority: US
Inventors: Wartenburg Kurt
Original assignee: Individual
Current assignee: Individual
Priority date: 1962-09-29
Filing date: 1963-09-24
Publication date: 1965-12-28
Anticipated expiration: 1982-12-28
Also published as: GB1016725A; AT232017B; CH416698A; ES291962A1

Description

1965 K. WARTENBERG AIR-COOLED HEAT EXCHANGER FOR COOLING LIQUID MEDIA 2 Sheets-Sheet 1 Filed Sept. 24, 1963 Jnvenfor:

Dec. 28, 1965 K. WARTENBERG AIR-COOLED HEAT EXCHANGER FOR COOLING LIQUID MEDIA Filed Sept. 24, 1963 2 Sheets-Sheet 2 P. fl H 2 4 0,, 1 Q E 5/ w. 4 m :1

WNW/WA WA/A MA MA ANN Jnvenfor:

United States Patent 3,225,824 AIR-COOLED HEAT EXCHANGER FOR COOLING LIQUID MEDIA Kurt Wartenhurg, 14 Kemmanns-Weg, Kettwig, Germany Filed Sept. 24, 1963, Ser. No. 311,153 Claims priority, application Austria, Sept. 29, 1962, A 7,717/62 7 Claims. (Cl. 165122) The present invention relates to an air-cooled heat exchanger for cool-ing liquids. More specifically, the present invention is directed to an lair-cooled heat exchanger for cooling highly viscous liquids.

In the past, liquids have been cooled almost exclusively in tube-type heat exchangers with external finning, using air as cooling medium. In such heat exchangers, the liquid to be cooled is passed through tubes of round or oval-shaped diameter, while the heat-absorbing air is directed along the outer surfaces of the finned tubes. In heat exchanging systems of this type the heat exchanging media are passed through the system in counter flow or cross-counter flow relative to one another, the flow of liquid through the heat exchanger being a forced flow and being subdivided into a plurality of separate currents, each of which preferably carries the same amount of liquid and exhibits the same end temperature, assuming a uniform efiiciency of the heat-exchanging surfaces.

The efliciency of the heat exchanger, besides other factors, is governed particularly by the velocity of flow and by the state of flow. A special problem encountered in this connection is the nonuniformity of the flow rates of the separate currents. Thus, it is extremely diflicult to maintain a uniform flow throughout the system, and the longer the separate channels, the greater will be the difliculty of making the flow uniform. The flow pattern is subject to continuous changes and can be stabilized only by special apparatus as throttling members at the outlet of the liquid medium.

To eliminate the disadvantages set forth before, heavyduty tube-type heat exchanging systems are divided into short tube sections arranged in series, with a mixing chamber being inserted between each two sections, thereby providing for an equalization of pressure and temperature between successive tube sections. Besides the equalization of pressure and temperature, which reduces the differences in the flow rates and in the end temperatures between the tube sections to a negligible amount, such an arrangement has the advantage that heat-exchanger units of any desired capacity can be assembled to meet any operational requirements, using building blocks of like shape and like dimensions as standard tube elements. The tubes are designed with a view toward keeping die manufacturing costs at a minimum, at the same time insuring that an optimum amount of heat will be transferred from the tube surface to the atmosphere.

Tube-type heat exchangers of the type described before have proved highly useful, particularly in the case of great differences between the inlet and outlet temperatures in the heat exchanging system. However, such heat exchangers are not suitable for cooling highly viscous media whose inlet and outlet temperatures differ only slightly from one another. To cool highly viscous liquids, large unrestricted passage areas of small hydrodynamic diameter are required. This requirement, however, cannot be satisfied by conventional tube-type heat exchanging systems.

To reduce the heat-transmission resistance by decreasing the hydrodynamic diameter and, consequently, increasing the heat exchanging efficiency, attempts have been made to increase the turbulence with the aid of socalled whirling members, swirl elements, bafile plates,

and the like. The increase in turbulence, however, is accompanied by a drop in pressure. Hence, it is only in few cases that satisfactory results can be expected from such .a system.

It has also been suggested to reduce the hydrodynamic diameter by decreasing the tube diameter. However, besides the pressure drop inentioned before this suggestion has the disadvantage that the cross-sectional area of the passage will be decreased also, thereby reducing the rate of flow and increasing the possibility of obstruction of the tubes which, in turn, will lead to a further reduction of the flow rate. This is particularly true of such heat exchangers as are employed in cooling highly viscous liquids as oils. In such cooling systems it is always possible that sediments and incrustations will be formed as the viscous liquid is directed through the tubes. The formation of such deposits not being dependent on any certain temperature level or temperature gradient between the oil and the coolant, large unrestricted passage areas will be indispensable to avoid incrustation and obstruction in the cooling systems [for highly viscous liquids To form large unrestricted passages of small hydrodynamic diameters, channels of substantially rectangular cross-section are required, and such channels must be relatively fiat and wide. Although in plate-type heat exchangers channels of the type set forth before can be provided, these cooling systems have a number of serious disadvantages which account for the fact that plate heat exchangers have hardly found any application in the cooling of liquids, particularly highly viscous liquids.

The main disadvantage of plate-type heat exchangers consists in that plates of certain dimensions are required for each width of cooling zone, that is, the distance beticular outlet temperature. This is due to the fact that the depth of plates is predetermined by the length of passage provided for the cooling air, which length can be varied only within extremely small limits, and that the height of the channels, that is, the distance between the plates, must be selected in accordance with the characteristics of the liquid. Hence, it is the width of the channels that is the only variable which can be altered to obtain a desired rate of flow. In addition, since the width of the cooling zone, that is, the temperature gradient in the cooler, is determined by the length of the cooling passage, each heat exchanger operating on the crosscounter flow principle in which the pressure losses of the cooling air and of the medium to be cooled are given and the flow rates in each of the cooling zones should be alike, is assigned a distinct width of plate. From this follows that plate-type heat exchangers for any operating conditions cannot be constructed of identical components.

It is accordingly a primary object of this invention to provide a heat exchanger in which are combined the advantages of tube-type heat exchangers with plate-type coolers.

Another object of the invention is to provide a heat exchanger incorporating the advantages of tube-type and plate-type heat exchangers and in which channels of large unrestricted cross-sectional areas having small hydrodynamic diameters are provided for the liquid medium to be cooled.

A further object of the invention is to provide a heat exchanger in which the rates of flow can be easily controlled.

Still another object of the invention is to provide a heat exchanger that can be constructed of identical components whereby its adaptability to distinct operating conditions is greatly improved.

The heat exchanger of the invention is composed of internally finned tube members of substantially rectangular cross-section through which the coolant is passed. The

tubes are arranged side by side to form rows of tubes or tube levels, and the rows of tubes are disposed in superjacent relationship and are separated from one another by spacer bars known per se whereby channels are defined by the outer surfaces of the tubes and the spacer bars through which the liquid to be cooled is passed in crosscounter flow. At the flow-reversal points all liquid flow levels are in communication with one another.

In this manner, heat exchangers for any desired operating condition can be constructed of identical elements. The height of the liquid stream can be varied over a wide range by proper selection of the spacing between superjacent tube levels, while the width of the channels is determined by the selected width of the spacer bars. To extend the flow path of the liquid, that is, the width of the cooling zone, each tube level can be enlarged by simply adding to it the required number of rectangular tubes together with the corresponding number of spacer bars.

At each point of fiow reversal an equalization of temperature and pressure is effected via the respective connecting channel thereby insuring that the flow rates in the channels on a particular level are virtually alike.

Another advantage of the invention is that if one of the channels should become clogged because of incrustation only that particular channel will malfunction rather than the entire tube level. In addition, the obstruction of the channels by sediments caused by undercooling is considerably reduced by continuous equalization of the temperature at the reversing points. Thus the life of the heat exchanger is considerably extendedv Further objects and advantages of the invention will become apparent from the following specification, when read in conjunction with the appended drawings in which an embodiment of the invention is illustrated.

In the drawings:

FIGURE 1 is a perspective view, partly broken away, of a standard tube element with internal finning as utilized in the construction of the heat exchanger of the invention;

FIGURE 2 is a sectional view taken along line IIIIII (FIG. 3) showing the arrangement of the flat iron bars welded to the tube elements and serving as spacer bars between superjacent tube levels, and the outer walls of the heat exchanger;

FIGURE 3 is an exploded view of a heat exchanger unit constructed in accordance with the invention, and

FIGURE 4 is a general side elevation, partly broken away, of a heat exchanger unit with cooling-air blower.

Referring now more particularly to FIG. 1, there is shown at 1, a heat exchanger element or tube of substantially rectangular cross-section. Inside of element 1, fin structures 3 are provided which extend throughout the length of heat exchanger element It. In the embodiment shown in FIG. 1, two fin structures 3' and 3" are provided which are mutually acted upon by tension and are firmly secured to the inner sides of a tube wall 2 as by soldering or hot-galvanizing, to insure a proper thermal connection between the fin structures and the tube wall.

As illustrated in FIG. 3, elements it are arranged side by side to form rows of tube elements or tube levels which are disposed one above the other thereby making up a stack of heat exchanger elements. Each row of tube elements 1 arranged in one plane is spaced apart from the next row of tube elements in another plane by fiat iron bar members 4' thereby forming between superjacent rows of tubes flat channels 4 of substantially rectangular cross-section through which the liquid to be cooled is passed. The height of channels 4 is determined by the thickness of spacing bar members 4 which are preferably welded to the outer sides of tube walls 2 and are adapted to direct the liquid through channels 4 which are defined by members 4 and the outer surfaces of tube elements 1.

Spacer bar members 4 have threaded pins 5 at their ends to permit vertical bar members 6 and

side walls

5 and 5" having corresponding holes to be secured thereto by nuts 5", bar members 6 being welded to heat exchanger elements 1 and holding the entire stack of superjacent rows of tubes in place. Thus, in the embodiment shown in FIG. 2, vertically extending passages or channels 16 are defined between bar members 6, which constitute partitions, by

wall members

5 or 5" and the lateral surfaces of the outer elements 1 extending perpendicularly to the direction of flow of the cooling medium. Passages or channels 16 are in communication with channels 4 which are formed by the upper and lower surfaces of tube elements 1 on different levels and whose height is defined by the thickness of the spacer bar members 4' as mentioned before.

As indicated by the arrows in FIGS. 2 and 3, the liquid to be cooled enters distribution chambers 9 of the heat exchanger through an input manifold constitute a feed pipeline 7 and branch pipes 8 and then flows in cross-counter flow through channels 4 to chambers 10 thereby giving off its heat. The cooled liquid leaves the heat exchanger through an output manifold constituted by branch pipes 11 and collecting pipe 12.

As is illustrated in FIG. 4, cooling is effected by an axial blower 13 and a diffusor 14 which force air through each of the heat exchanger elements 1 in the direction indicated by arrows 15.

In the figures is shown how the advantages of platetype heat exchangers have been utilized in tube-type coolers in designing the channels through which the medium to be cooled is passed. The arrangement shown is extremely economical and particularly efiicient in cooling highly viscous liquids having a high setting point in that the temperature in the various channels is prevented from dropping below the particular setting point before the liquid arrives at the end of the cooling path where it can join with liquid streams from other channels exhibiting a higher temperature. Since, in the cooling of highly viscous liquids, it has to be strongly anticipated that solid substances will be formed at some point in the flow passage which will disadvantageously affect the cooling time because of their tendency to reducing the unrestricted cross-sectional area of flow, the continuous connecting channels of the invention at the flow-reversal points are of vital importance. This will become apparent from the following example.

Assume a heat exchanger having ten liquid flow levels with ten flow reversal points on each level. Further assume that one of the channel sections between two flow reversal points is obstructed. In such a case the efiiciency of the heat exchanger would be reduced 10% in the absence of the connecting channels of the invention. On the other hand, if the heat exchanger were equipped with the connecting channels of the invention, its efficiency would be reduced only 1%.

Further assume that on each flow level a channel section is obstructed between two reversing points. In this case, the efficiency of the heat exchanger would decrease as much as in the absence of the connecting channels of the invention, while, under the same conditions, the efiiciency of the heat exchanger of the invention would be reduced only 10%.

The formation of solid substances in the liquid to be cooled is directly controlled by the connecting channels, inasmuch as these channels serve to prevent the liquid from being excessively cooled. Thus, the formation of solid substances will be reduced. In addition, the connecting channels also minimize the loss in emciency caused by the formation of solid substances in the liquid.

It should be understood that the term air as used herein includes any type of gas suitable for cooling as atmospheric air, carbonic acid, nitrogen or the like.

While the novel features of the invention as applied to a preferred embodiment have been shown and described herein, it will be obvious that modifications of the heat exchanger illustrated may be made without departing from the spirit and the scope of the invention. Accordingly, the scope of this invention is to be governed by the language of the following claims construed in the light of the foregoing description of this invention.

What is claimed is:

1. A heat exchanger comprising, in combination:

(a) a plurality of tubular elements elongated in a common direction,

(1) said elements being secured to each other to constitute a plurality of rows,

(2) the elements of each row being contiguously juxtaposed in a common plane and being spaced from the elements of adjacent rows in a direction transverse of said plane, said rows jointly constituting a stack of tubular elements;

(b) two wall members extending in said common direction in respective planes transverse of said common planes and being spaced from said stack of elements in opposite directions;

(c) a plurality of spacer members elongated transversely of said common direction and interposed between said rows,

(1) the spacer members interposed between each pair of adjacent rows constituting a group of spacer members spaced from each other in each other in said common direction and alternatingly extending from said wall members to a point spacedly adjacent the other wall memher,

(2) whereby each pair of said rows, the interposed group of spacer members, and said wall members define an elongated serpentine shaped flow path having a plurality of areas of flow reversal adjacent said Wall members, the several flow paths being spaced in said transverse direction,

(3) the spacer members of the several groups being aligned with each other in respective planes of alignment spaced in said transverse direction and transverse thereto;

(d) a plurality of partition members interposed between said wall members and said stack of elements in said planes of alignment whereby said wall members, said partition members, and said stack jointly define a plurality of passages connecting the areas of flow reversal of adjacent flow paths in said transverse direction, said partitions respectively separating adjacent passages;

(e) first means for passing a first fluid through said tubuar elements in said common direction; and

(f) second means for passing a second fluid longitudinally through said flow paths.

2. A heat exchanger as set forth in claim 1, further comprising fin means in said tubular elements.

3. A heat exchanger as set forth in claim 1, wherein said tubular elements are of approximately rectangular cross section.

4. A heat exchanger as set forth in claim 1, wherein said partition members are elongated in said planes of alignment.

5. A heat exchanger as set forth in claim 1, wherein said first means include a blower.

6. A heat exchanger as set forth in claim 1, wherein said second means include input manifold means communicating with respective first terminal portions of said flow paths, and output manifold means communicating with respective second terminal portions of said flow paths, said terminal portions being spaced in a direction opposite to the direction of passage of said first fluid through said tubular elements.

7. A heat exchanger as set forth in claim 4, wherein said tubular elements are substantially identical.

References Cited by the Examiner UNITED STATES PATENTS 791,876 6/1905 Burdh 167 1,874,360 8/1932 Ryan 165-143 X 1,899,080 2/1933 Dalgliesh 165-166 X 2,650,073 8/1953 Holm 165-167 X 3,017,161 1/1962 Slaasted et a1. 165167 FOREIGN PATENTS 189,806 6/ 1937 Switzerland.

ROBERT A. OLEARY, Primary Examiner.

CHARLES SUKALO, Examiner.

Claims

1. A HEAT EXCHANGER COMPRISING IN COMBINATION: (A) A PLURALITY OF TUBULAR ELEMENTS ELONGATED IN A COMMON DIRECTION, (1) SAID ELEMENTS BEING SECURED TO EACH OTHER TO CONSTITUTE A PLURALITY OF ROWS, (2) THE ELEMENTS OF EACH ROW BEING CONTIGUOUSLY JUXTAPOSED IN A COMMON PLANE AND BEING SPACED FROM THE ELEMENTS OF ADJACENT ROWS IN A DIRECTION TRANSVERSE OF SAID PLANE, SAID ROWS JOINTLY CONSTITUTING A STACK OF TUBULAR ELEMENTS; (B) TWO WALL MEMBER EXTENDING IN SAID COMMON DIRECTIONS IN RESPONSIVE PLANES TRANSVERSE OF SAID COMMON PLANES AND BEING SPACED FROM SAID STACK OF ELEMENTS IN OPPOSITE DIRECTIONS; (C) A PLURALITY OF SPACER MEMBER SELONGATED TRANSVERSELY OF SAID COMMON DIECTION AND INTERPOSED BETWEEN SAID ROWS, (1) THE SPACER MEMBERS INTERPOSED BETWEEN EACH PAIR OF ADJACENT ROWS CONSTITUTING A GROUP OF SPACER MEMBERS SPACED FROM EACH OTHER IN EACH OTHER IN SAID COMMON DIRECTION AND ALTERNATINGLY EXTENDING FROM SAID WALL MEMBERS TO A POINT SPACEDLY ADJACENT THE OTHER WALL MEMBER, (2) WHEREBY EACH PAIR OF SAID ROWS, THE INTERPOSED GROUP OF SPACER MEMBERS, AND SAID WALL MEM BERS DEFINE AN ELONGATED SERPENTINE SHAPED FLOW PATH HAVING A PLURALITY OF AREAS OF FLOW REVERSAL ADJACENT SAID WALL MEMBERS, THE SEVERAL FLOW PATHS BEING SPACED IN SAID TRANSVERSE DIRECTION, (3) THE SPACER MEMBERS OF THE SEVERAL GROUPS BEING ALIGNED WITH EACH OTHER IN RESPECTIVE PLANES OF ALIGNMENT SPACED IN SAID TANSVERSE DIRECTION AND TRANSVERSE THERETO; (D) A PLURALITY OF PARTITION MEMBERS INTERPOSED BETWEEN SAID WALL MEMBERS AND SAID STACK OF ELEMENTS IN SAID PLANES OF ALIGNMENT WHEREBY SAID WALL MEMBERS, SAID PARTITION MEMBERS, AND SAID STACK JOINTLY DEFINE A PLURALITY OF PASSAGES CONNECTING THE AREAS OF FLOW REVERSAL OF ADJACENT FLOW PATHS IN SAID TRANSVERSE DIRECTION, SAID PARTITIONS RESPECTIVELY SEPARATING ADJACENT PASSAGES; (E) FIRST MEANS FOR PASSING A FIRST FLUID THROUGH SAID TUBUAR ELEMENTS IN SAID COMMON DIRECTION; AND (F) SECOND MEANS FOR PASSING A SECOND FLUID LONGITUDINALLY THROUGH SAID FLOW PATHS.