US2655346A - Heat exchanger with tube matrix - Google Patents

Description

Oct. 13, 1953 R. w. CORBITT ETAL 2,655,346

HEAT EXCHANGER WITH TUBE MATRIX Filed July 7, 1950 luvzllrm R. W CORB T q- I H. DALE "WJM- 22 M45 AT YWIYJ' 2 Sheets-Sheet 1 Oct. 13, 1953 R. w. CORBITT ET AL 2,655,346 HEAT EXCHANGER WITH TUBE MATRIX Filed July 7, 1950 2 Sheets-Sheet 2 1%EMI l V/um/w Coma/Wt El Joy/v. f/z/afl D046 MMJ W bank, from developing downstream of the tube bank, and thus diminishes the resonant energy.

The invention is applicable to various forms of heat exchanger of the kind specified. For instance the invention is readily applied ina heat-exchanger which comprises a straightthrough duct carrying the first medium and a matrix of heat-exchange tubes extending across the duct, so that the first medium fiows over the surfaces of the tubes. Another common heat exchanger arrangement in which the invention can be readily applied, comprises a central cylindrical duct and an outer annular duct separated by an annular matrix of heat exchange tubes, so that, in use, the first medium flows transversely across the tubes; in this arrangement, when whistle in the heat exchanger is experienced, the presence of resonant nodal planes has been detected in the outer annular duct.

The application of the invention in these forms of heat exchanger is illustrated diagrammatically in the accompanying drawings, to which the following description refers.

In this drawing:

Figure 1 is a section parallel to the direction of flow of the first medium through a straightthrough type of heat exchanger, the plane of the section being indicated at 1-1 of Figure 2 which is a view in the direction of arrow II of Figure 1;

Figure 3 is a section at right angles to the axis of a heat exchanger having a matrix of heat exchanger tubes of annular form the section being taken on the line IIIIII of Figure 4 and Figure 4 is a section on IVIV of Figure 3, and

Figure 5 illustrates a modification of the arrangement of Figure 4. 7

Referring to Figures 1 and 2, the heat exchanger diagrammatically illustrated comprises a duct passage ill with side walls [HA and MB, through which passage Ill the first medium flows in the direction of the arrow II. A bank or matrix 12 of heat exchange tubes extends across the duct passage parallel to the side walls IDA, B; the first fiuid medium fiows through the spaces between the tubes and over the surfaces of the tubes and the second medium flows in the bores of the tubes.

With a heat exchanger of this type, it has been found that the flow of the first medium across the tube matrix i2 may give rise to an objectionable whistle having a node in a transverse plane as indicated by the dotted line I l, and we have found that if bafile plates such as baflle plates l3 are provided within the tube matrix 52 in planes parallel to the direction of flow of the first medium through the duct and to the tubes [2, the whistle can be avoided.

In the simple heat exchanger illustrated, two baiile plates I3 are provided within the matrix and the plates is divide up the space between the side walls WA, HEB into three parts, so that the transverse dimension of each of these parts, either between adjacent baiiles It! or between a bafiie l3 and a side wall MIA or IUB is less than half the wave length of a note having a frequency equal to the estimated freouency of vortex shedding in the manner described.

In certain cases, however, it is inconvenient to construct the heat exchanger with bafiie plates within the structure of the matrix 12, and an alternative arrangement is used, which consists in the provision of external baflle plates l5. The bafiie plates l5 are located in planes parallel to 4 the direction of flow of the first medium on the outlet side of the tube matrix [2 and inclined at acute angles to the tubes, and their function is to prevent the development of or extension of a nodal plane, such as plane [4, on the downstream side of the tube matrix I2. Where it is possible to employ bafiies such as baffles 13 they may be used in combination with baffle plates 50.

It will be seen from Figure 2 that the external baffle plates !5 are at an acute angle to the nodal plane [4, thereby preventing the maintenance of this node (if formed) in the heat exchanger outlet. By inclining the baiiles in this way it is unnecessary for them to be spaced less than half a wave length apart as described for baffle plates [3. If desired, bafile plates may be arranged downstream of matrix I2 in a manner similar to baflie plates 13.

In Figures 3 and 4, an alternative form of heat exchanger is illustrated in which the first medium flows, in the direction of the arrow 2!, through an inlet duct 20 into the space 22A within an annular matrix of heat exchanger tubes 22, and. through the matrix 22 into an annular outlet duct 23, the external wall of which is indicated at 23A.

With such an arrangement, it has been found that the flow of the first fluid medium across the heat exchanger tubes may give rise to a series of circumferentially distributed nodal planes some of which are indicated at 25. It will be noted that these nodal planes are not parallel to a side wall but are radial to the axis of the heat exchanger system; the number of the nodal planes 25 is determined by the circumferential dimensions of the matrix 22 and the frequency of vortex shedding. The vibrations which produce the nodal system give rise to the undesirable whistle effects previously mentioned.

In order to avoid this whistle efiect, external bafiles as indicated at 24 are provided, which due to their inclination to the radial planes serve to absorb vibrational energy and prevent the maintenance of the nodal system in the annual outlet duct 23. It is not necessary to space inclined bafiles at a distance less than half the wavelength of the resonant frequency.

If desired, there may also be provided radially disposed bafiies 26 (Figure 5) arranged within the matrix 22, to be spaced apart by a mean distance, which is less than half the wavelength of a note having a frequency corresponding to the frequency of the vibrations induced by the passage of the first medium. Such bafiles will therefore be spaced apart at somewhat less distance than the dimension between the adjacent nodal planes 25.

It has been found that the present invention is particularly useful in its application to heat exchangers for gas-turbine engines where the de sirability of designing the heat exchanger to have small tubes, combined with the comparatively high mass flow of exhaust gas (the first medium) gives rise to high gas velocities through the tube matrix and high frequency of vortex shedding.

Adoption of the invention not only reduces or avoids objectionable noise but also avoids losses arising from the production of wave energy.

We claim:

1. In heat-exchange apparatus of the class comprising a casing, a matrix of tubes arranged within said casing, an inlet connection to said casing, an outlet connection from said casing, said inlet and outlet connections being positioned to permit a first fluid medium in passing from said inlet connection to said outlet connection to flow transversely across the tubes of said matrix of tubes, and inlet connection to the tubes of said matrix of tubes and an outlet connection from said tubes whereby a second fiuid medium can flow in said tubes; the combination with said matrix of tubes of a plurality of bailie elements located within said casing between said matrix of tubes and said outlet connection from said casing thereby to be in the path of said first fluid medium on the downstream side of said matrix of tubes, each said bafile element being disposed at an acute angle to a plane containing both the direction of the flow of said first fluid medium through the matrix of tubes at a location adjacent said bafile element and also the lengthwise dimensions of the adjacent tubes, whereby the formation of nodal planes of resonant vibrations on the downstream side of said matrix of tubes is inhibited.

2. Heat-exchange apparatus as claimed in claim 1 comprising also internal bafile devices within said matrix of tubes, said baflle devices being arranged to be parallel both to the direction of adjacent flow of said first fluid medium through said matrix of tubes and to the longitudinal dimension of the tubes, and being spaced with respect to one another by a distance which is less than the distance between vibrational nodes liable to form in said matrix in planes parallel to said baflle devices.

3. Heat-exchange apparatus as claimed in claim 2 having said baflie devices spaced from a wall of said casing when adjacent a wall and from a next adjacent baffle device by a distance W given by the expression 0.6a-D Vmax.

where a is the velocity of sound in said first fluid medium, D is the diameter of the tubes of said matrix of tubes, and V max. is the maximum velocity of said first fluid medium between the tubes.

4. In heat-exchange apparatus comprising a tubular casing member having an inlet thereto and an outlet therefrom, a matrix of parallel tubes arranged within said casing in the flow path between said inlet and said outlet with their axes substantially at right angles to the flow path, there being an inlet connection to the tubes and an outlet connection from the tubes to provide a second flow path, the combination with said matrix of tubes of a plurality of plate-like baflles arranged in first said flow path between said matrix and said first outlet thereby to be downstream of the matrix, each said baffle being contained in a plane containing the direction of flow from said matrix to said first outlet and inclined at an acute angle to nodal planes tending to develop downstream of the matrix.

5. In heat-exchange apparatus comprising a cylindrical casing having an inlet thereto and an outlet therefrom, a plurality of tubes arranged within the casing with their axes parallel to one another and parallel to the casing axis and to form an annular matrix with its outer bounding surface spaced radially inwards from the casing wall so that fluid flowing from said inlet to said outlet flows substantially radially through the matrix of tubes, there being an inlet connection to said tubes and an outlet connection therefrom so that the bores of said tubes afford a second flow path; the combination with said casing and said matrix of a plurality of plate-like baffles located in said first flow path between said matrix and said first outlet thereby to be downstream of said matrix and circumferentially spaced in said flow path relative to said matrix, each said bafile being contained in a plane which is parallel to the casing axis and is inclined at an acute angle to adjacent radii from the casing axis.

6. In heat-exchange apparatus comprising a cylindrical casing having an inlet thereto and an outlet therefrom, a plurality of tubes arranged within the casing with their axes parallel to one another and parallel to the casing axis and to form an annular matrix with its outer bounding surface spaced radially inwards from the casing wall so that fluid flowing from said inlet to said outlet flows substantially radially outwards through the matrix of tubes, there being an inlet connection to said tubes and an outlet connection therefrom so that the bores of said tubes afford a second flow path; the combination with said casing and said matrix of a plurality of plate-like baffles located in circumferentially spaced relation in the annular space between said annular matrix and said casing wall thereby to be downstream of said matrix,

each said bafile being contained in a plane which is parallel to the casing axis and is inclined at an acute angle to adjacent radii from said casing axis.

7. Heat-exchange apparatus as claimed in claim 6, comprising also bafiles located in said matrix each said bafile being radially disposed with respect to the casing axis and being spaced from each next adjacent bafile by a distance which is less than half the wave length of a note covering a frequency equal to the frequency of vortex shedding from the matrix tubes.

8. In heat-exchange apparatus comprising a tubular casing having an inlet at one end and an outlet at its opposite end with a first flow path between said inlet and outlet which flow path is parallel to the casing axis, and a plurality of parallel tubes extending across said casing substantially at right angles to the easing axis and afiording in their bores a second flow path, the combination with said casing and matrix of a plurality of plate-like baflles located parallel to one another within said casing between said matrix and first said outlet thereby to be on the downstream end of said tubes, each of which baffles is in a plane which is parallel to the casing axis but is inclined at an acute angle to the axes of the tubes.

9. Heat-exchange apparatus as claimed in claim 8, comprising also baflles within said matrix of tubes each said baille being contained in a plane parallel to the axis of said casing and to the axes of the tubes and being spaced from each adjacent battle by a distance which is less than half the wave-length of a note covering a frequency equal to the frequency of vortex shedding from the matrix tubes.

ROBERT WILLIAM CORBITT. JOHN HUGH DALE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,641,999 Webster Sept. 18, 1927 1,888,711 Bourne Nov. 22, 1932 2,144,506 Potter Jan. 17, 1939 2,155,278 Mautsch Apr. 18, 1939 2,396,208 'Serre et al Mar. 5, 1946 2,397,208 Saco, Jr., et al. Mar. 26, 1946 2,479,165 Jackson Aug. 16, 1949

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