US3351131A - Heat exchangers - Google Patents

Description

Nov. 7, 1967 L. BERTHOLD HEAT EXCHANGERS Filed April 8, 1965 ZNVENT OR LOU/S BE RTHOLD M BY W 7/ ATTORNEY United States Patent 3,351,131 HEAT EXCHANGERS Louis Berthold, Grenoble, France, assignor to Societe Grenobloise dEtudes et dApplications Hydrauliques, Grenoble, France, a corporation of France Filed Apr. 8, 1965, Ser. No. 446,614 Claims priority, application France, Apr. 9, 1964, 4,672/ 64 1 Claim. (Cl. 165-159) This invention relates to heat exchangers and more particularly to heat exchangers of the type in which there are arranged within a casing a plurality of spaced longitudinally extending parallel tubes and spaced, alternately disposed transverse baffles so as to provide a first fluid circulatory system inside of the tubes, and to provide outside of the tubes a second fluid circulatory system in which the fluid is caused to flow in an alternate fashion repeatedly across the tubes in transverse passageway sections defined by the baflie plates.

Heat exchangers of the indicated type have been constructed so that the aforesaid transverse passage sections of the second fluid system are of substantially equal crosssection, but the constructions of such exchangers have been such that the system as a whole caused a substantial reduction in the velocity of the fluid passing therethrough. This is an undesirable condition because it results in a reduction of the efliciency of heat transfer. Prior heat exchangers of the indicated type are also usually constructed so that portions of one or more of the parallel tubes are located beyond the free edges of the alternately disposed baflles thus providing unsupported tube portions of longer lengths than the lengths of the tube portions between the baffles, in the areas of flow of the fluid beyond such free baffle edges. The disadvantages of this construction are that the unsupported tube portions will vibrate more easily and in a diflerent frequency from that of the other tube portions between the bafllles, and because such vibrating tube portions constitute obstacles to the fluid flow in the areas beyond the free baflle edges, the fluid flow velocity in such areas will be unevenly distributed. Since it is practically impossible to determine the flow velocity distribution in such areas of the prior exchangers, the heat exchange condtions in the tubes and the possible vibration frequencies of the tubes cannot be accurately calculated.

The primary purpose of the present invention is to pro vide an improved heat exchanger of the indicated type which shall be free of the aforesaid disadvantages of prior constructions.

In accordance with one of the features of the invention, the space in the areas of the casing beyond the edges of the baflles is clear and unoccupied by tubes thereby enabling the fluid circulation flow inside the casing to be given a direction perpendicular to the tubes thereby ensuring eflicient heat exchange and little loss of head in such flow. The cross-sectional area of such clear spaces is made substantially equal to that of the transverse passage sections between the baflles to ensure that there are no appreciable velocity variations occurring at any point along the fluid circulation path. It has been found that when the heat exchanger is so constructed, it is possible to maintain a uniform pressure distribution in the clear spaces and thereby to make effective arrangements to ensure that the fluid flow will change its direction at the baflle plates to one perpendicular to the tube clusters between such plates, and thereby enable the use of such tube clusters under satisfactory thermal efliciency conditions. Furthermore, it has been found that the absence of tubes in such clear spaces, not only reduces the head losses of the fluid circulating in the cas- "ice ing, but instead of having any adverse effect on the heat exchange efliciency, actually increases it because the heat exchange conditions in these spaces in prior constructions have always been unsatisfactory due to the dead circulation zones that are usually formed in such spaces thereof.

A further feature of the aforesaid arrangement is that all of the tubes in the cluster are supported by the baffle plates and are in uniform fluid velocity Zones. Accordingly, the vibration frequency afiecting them can be calculated and steps taken to avoid vibration of such tubes.

The features and advantages of the invention will be better understood from a perusal of the following description when read in connection with the accompanying drawings which illustrate by way of example one form in which the invention may be utilized in practice and in which FIG. 1 is a vertical sectonal view of a heat exchanger constructed in accordance with the invention;

FIG. 2 is a transverse vertical sectional view taken along the line 22 of FIG. 1; and

FIG. 3 is a view similar to FIG. 2 but taken along the line 33 of FIG. 1.

In the drawings, the reference 10 indicates generally the cylindrical casing of the heat exchanger. Located within the casing and partly filling the space therein are a cluster of tubes 12 which are arranged in spaced parallel relation in .a plurality of rows and which extend throughout the length of the casing and are supported by the tube walls or plates 11, 11' at the end of the cylindrical casing. A fluid is circulated in the direction of the arrows f through the tube 12 in a known manner.

Located in equally spaced relation within the casing 10 are a plurality of transverse baflle plates 13 and 13 to set up the required fluid circulation inside the casing. It will be noted from a comparison of FIGS. 1 and 2 of the drawings, that the baflles 13 which are alternately arranged with relation to the 'baflies 13, terminate just below the lowermost row of tubes 12 in the cluster or bank thereof so that the free bottom edges 23 thereof and the portions of the cylinder opposed to such edges 23 define clear spaces 14 unobstructed by any tubing. A comparison of 'FIGS. 1 and 3 will show that the battles 13' which extend upwardly from the bottom or opposite side of the casing terminate just above the uppermost row of tubes 12 so that the free upper edges 23' thereof and the portions of the cylinder opposed to such edges 23' define clear spaces 15 unobstructed by any tubing. The remaining peripheries of the baflie plates 13 and 13 are welded or otherwise suitably secured to the interior wall of the casing 10 so that such plates form additional supporting means for all of the tubes 12, it "being noted from FIGS. 2 and 3 that all of the tubes 12 extend through snug openings provided in each of such plates to permit of such support. The tubes 12 may be suitably secured as by welding to the baflles plates 13, 13.

As previously indicated, the baffles plates 13, 13' are equally spaced from each other. The end baflle plates 13 and 13 are also spaced from the tube plates 11 and 11', respectively, a distance equal to the distance between adjacent baflle plates. As shown in FIG. 1, the fluid circulating across the tubes 12 in the casing 10 enters the latter through an adaptor stub 16 in the direction of arrow flows through the casing in the manner indicated by the arrows f and finally discharges through the adaptor stub 17 as indicated by arrow f In its flow, the fluid alternately passes through the clear spaces 14 and 15 formed by the baflle plate edges 23, 23', respectively, with the interior wall of the casing 10.

To accomplish the purposes of the invention the optimum amount of clear space to be allowed for a given volume inside the casing 10 may be readily calculated in a manner known to the art. If, as a conventional assumption, the tube spacing e is taken as being equal to a quarter of the tube diameter, i.e.

4 the total fluid passage width between the tubes for a casing of diameter D will be D/5, and the passage cross-section between baffle plates spaced a distance L apart will be i.e., roughly 25%. In other words, the total clear volume above and below the tube cluster amounts to roughly half the casing volume, which is quite considerable.

It will be understood from the foregoing that the clear spaces 14 and beyond the baflle plates 13, 13' respectively, appreciably reduce the head losses in these regions While also enabling the direction of fluid flow to be changed from one baffle plate to the next under satisfactory conditions, and causing the fluid circulation between the baflle plates to occur in a direction perpendicular to all the tubes so that satisfactory heat exchange is ensured. Since the clear spaces 14 and 15 are unoccupied by tubes, there is provided the best possible conditions for determination of the flow circulation conditions in such spaces where the flow has a change of direction of 180. Having a knowledge of the flow conditions at the entrances of the transverse passageway sections defined by the baffle plates, there can be accurately calculated the heat exchange conditions in the cluster of tubes and the possible vibration frequency of the tubes with the view of avoiding it, the latter of which may be accomplished because in accordance with the invention all of the tubes are identically installed, are all supported by all of the baffles and are situated in uniform fluid velocity zones.

In the practice of the invention, it is preferred that in the clear space above the tube cluster between the tube wall 11 and the adjacent baflle plate 13, and below the fluid intake 16, there be provided a suitable flow distribution device, such as the perforated plate 18, to give a practically uniform pressure distribution in the first transverse passageway section 19 in which the incoming fluid comes into contact with the tubes, so as to ensure that the flow circulating through transverse passageway section 19 is directed truly perpendicular to the tubes in such section.

The tube cluster may also be provided with one or more 4- additional partitions 20 located between two neighboring baifle plates 13, 13' in order to provide a more rigid asscm bly and prevent vibration. These additional partitions 20 may also be constructed to assist in guiding the fluid flow in a direction perpendicular to the tubes.

While I have herein above described and illustrated in the drawings one manner in which my invention may be utilized, it will be understood by those skilled in the art that modifications thereof may be made, such as, for example, by using a square or rectangular heat exchanger cross-section, without departing from the spirit of the invention, or the scope of the appended claims.

I claim:

A heat exchanger for fluids comprising two passageways arranged in heat exchange relation, one of said passageways being composed of a cluster of tubes extending longitudinally of the exchanger, and the other of said passageways being composed of a longitudinal tubular wall of said exchanger, tube plates at the ends of said tubular wall, and a plurality of spaced, transverse baffles arranged within said tubular wall between said tube plates to cause a fluid to flow repeatedly across the tubes in a series of transverse passageway sections, said baffles being equally spaced from each other and being spaced from said tube plates a distance equal to the distance between adjacent baffles and together with said tube plates defining transverse passageway sections of equal cross-sectional area, said baflles providing in alternate relation at their ends fluid openings connecting the ends of adjacent transverse passageway sections and each having a cross-sectional area substantially equal to the cross-sectional area of one of said transverse passageway sections to prevent the occurrence of appreciable velocity variations at any point along the fluid circulation path, and all of the tubes in said cluster thereof extending through and being supported by all of said baffles to minimize vibration thereof and so that said fluid openings are clear and unoccupied by said tubes, thereby enabling the fluid circulation flow to be directed through said transverse passageway sections perpendicularly to the tubes therein to ensure efficient heat exchange, and with little loss of head in said flow, the clear space at the entry end of the first transverse passageway section in the series thereof having provided therein a flow distribution device extending across the entire uniform width of such pasasgeway in such space.

and capable of directing the incoming fluid so that it enters into such section at a practically uniformly distributed pressure and perpendicularly to the tube portions in such section.

References Cited UNITED STATES PATENTS 1,457,941 6/1923 Shevlin l--159 1,982,010 11/1934 McNeal l59 X 2,391,244 12/1945 Jackson 165-l5 8 X 2,513,124 6/1950 Weiks 165-174 X 2,589,730 3/1952 Rathkey 165-146 FOREIGN PATENTS 984,248 2/ 1951 France. 633,132 7/1936 Germany.

ROBERT A. OLEARY, Primary Examiner.

A. DAVIS, Assistant Examiner.

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