IL148749A - Heat exchanger - Google Patents

Description

Heat exchanger Societe D'Etudes Et De Constructions Aero-Navales C. 138243.1 FIELD AND BACKGROUND OF THE INVENTION This invention relates to a heat exchanger in particular of a type that comprises a great number of first flowing paths of a first fluid at a first temperature made of a thermally conducting material and extending axially in a hollow housing in which a second fluid at a second temperature which is different from the first temperature passes in thermal exchange contact with said first flowing paths.

In known heat exchangers of the above type, the first paths are each formed by a separate tube. The fact that there is thus provided a great number of such tubes makes that the construction of these heat exchangers is complicated and costly. This drawback is still increased when the tubes are formed by pin shaped tubes, each necessitating a shape with a specific length and width.

OBJECT AND SUMMARY OF THE INVENTION The present invention has for its object to provide a heat exchanger of the hereinabove type, which does not have the drawbacks as above indicated.

To reach this object, the heat exchanger according to this invention is characterized in that it comprises a plurality of parallel fiat tubes that are juxtaposed in direction of their width within the housing at a predetermined distance the one from the other, and the inner space of which is divided by means of intercalary means of a thermally conducting material into a plurality of parallel axial channels that constitute the first flowing paths.

According to another feature of the invention, the second fluid flows through spaces between adjacent flat tubes, and each space is divided by means of intercalary means of thermally conducting material into a plurality of second channels.

According to still another feature of the invention, the second channels are parallely or perpendicularly extended to the first channels and open at their two ends respectively in a perpendicular inlet channel and a perpendicular outlet channel communicating with inlet and outlet apertures, respectively, in the wall of the housing.

Various other features of the invention will moreover be revealed from the following detained disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention is shown, as a non limitating example, in the accompanying drawings, wherein : Fig. 1 is a horizontal cross sectional view of a heat exchanger according to the present invention, taken along line l-l of Fig. 2 ; Fig. 2 is a cross sectional view taken along line ll-lll of Fig. 1 ; Fig. 3 is an enlarged view of the portion that is encircled at III in Fig. 2 ; Fig. 4 is a partly cut-away perspective view of the part shown at IV in Fig. 1 ; Fig. 5 is a diagrammatic view showing another circulation profile of the fluid F2 ; Fig. 6 is a diagrammatic view showing still another circulation profile of the fluid F2 ; Fig. 7 is diagrammatic perspective view of another embodiment of the flat tubes and of a pin-shaped profile of the fluid F2 ; Fig. 8 is a cross-sectionnal view of a heat exchanger fitted with the device of Fig. 7 ; ■ _ Fig. 9 is a diagrammatic cross-sectionnal view of still another embodiment of the heat exchanger of the invention, with a crossed circulation profile ; Fig. 10 is a detailed cut-away cross-sectional view of a specific profile of the fluid circulation channels ; Fig. 11 is a cross-sectionnal view taken along line XI-XI of Fig. 10 ; and Fig. 12 is a view similar to Fig. 1 of another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, the heat exchanger of the invention, as shown as a non limitating example in the figures, essentially comprises a . hollow housing 1 that is advantageously made of cast iron or a composite material which contains, surrounded by a casing 2, a plurality of flat tubes 3, made of a thermally conducting material, that are parallel and juxtaposed in a direction perpendicular to their cross section great axis at a predetermined distance the one from the other.

As shown particularly in Fig. 2, the casing 2 surrounding the tubes 3 has a substantially rectangular cross-section, in the illustrated example a square cross-section when the housing 1 has a circular cross-section.

The tubes 4 are at each end fitted and fixed, for example through brazing; in a seal-tight manner, in a header plate 5 and 6, respectively. The header plate 5, shaped as a flange, is mounted on the right hand end of the housing 1 , which is open and is part of an inlet and outlet header tank 7 for a first fluid F1 , as this is shown by arrows. The inner chamber 8 of the header tank 7 is separated into two portions communicating with inlet and outlet fittings 9 and 10, respectively. The header plate 6 that is placed at the closed side of the housing 1 is mounted on a fluid transfer or return header tank 12. Therefore, the fluid F1 that enters through the inlet fitting 9 into the inlet part of the chamber 8 of the header tank 7 flows through one half of the tubes 3 in direction of the header plate 6 and is sent back by the transfer header tank through the other half of the tubes 3 into the outlet fitting 1 1. In Fig. 2, the five upper tubes can be considered as being connected to the inlet fitting 9, and the five lower tubes to the outlet fitting 10.

The internal space of each flat tube 3 is divided by means of a corrugated intercalary strip 14 into a plurality of channels 15 that are parallel to axis of the tube (see in particular Figs. 3 and 4). By means of an intercalary strip of a same type, that is also corrugated, the space 18 separating two adjacent flat tubes 3 is separated into a plurality of parallel channels 19. The channels 19 are parallel to the channels 5 of the flat tubes 3. By referring to Figs. 1 and 4, there is found that the channels 19 formed between two tubes 3 communicate, at one end, with transverse channels 21 , also formed by means of an intercalary strip 22 between the two same tubes 3, that open in an internal space portion 23 of the housing 1 through a window 24 in the side wall of the casing 2. The space portion 23 forms an inlet space for a second fluid F2 which may enter this space through an inlet fitting 25. The other end of the axial channels 19 communicate, by means of transverse channels 27, with the internal space portion 28 of the housing 1 forming the outlet space for the fluid F2 2 which may flow out of the housing 1 through an outlet fitting 29. Obviously, the transverse channels 27 open in the space portion 28 through a window 30 in the side wall of the casing 2. The channels 27 are also formed by a corrugated intercalary strip 22' that is placed between the same two tubes 3. It is still found that the inlet and outlet spaces 23, 28 of the housing 1 are separated by means of a seal tightness ring 32.

With respect to the connection of the transverse channels 21 , 27 and axial channels 19 between two adjacent fiat tubes 3, the shapes of the intercalary strips constituting these two sets of channels are shown in Fig. 1 and more particularly in Fig. 4. Obviously, the intercalary strips are made of a thermally conducting material and are fixed by any suitable manner, in particular by brazing or glueing onto the inner or outer faces of the tubes along their ridge lines, according as it is an axial or transverse intercalary strip.

In the illustrated example, circulation of the fluid F2 is made according to a Z shaped profile, with inlet at one end of the housing 1 and outlet at the other end of the housing 1 , but at the opposite side, flowing being of a counter-flow type for the inlet flat tubes and of a parallel-flow type for the outlet tubes 3.

Fig. 5 diagrammatically shows, in a view similar to Fig. 1 , an arrangement of the channels 21 and 27 for obtaining a U shaped circulation of the fluid F2. Fig. 6 shows, in a diagrammatic way, the profile of the intercalary parts between tubes for obtaining a pin shaped circlation of the fluid F2. In this case, the inlet and outlet for this fluid are on the same side of the housing 1.

Fig. 7 diagrammatically shows a construction of a heat exchanger in which the P2, fluid -2f* circulates in a counter-flow in the inlet and outlet tubes that are respectively designated by numerals 32 and 33.

Fig. 8 shows that the internal space of the housing 1 is separated in inlet and outlet portions 35 and 36 corresponding to the portions 23 and 28 of Fig. 1 by means of axial seal-tightness partition walls 37. These partition walls may be provided with valves (not shown) the opening of which is controlled in function of temperatures of the fluids. Such valves that are temperature sensitive could advantageously be made of a form memory material, known per se.

Fig. 9 diagrammatically shows an embodiment of the heat exchanger of the invention with a crossed profile of the circulations of the fluids F1 and F2. For this purpose, the channels for circulating the fluid F2 are extended in each space between two adjacent flat tubes and between the outer tubes and the casing that surrounds them, perpendicularly to these tubes. On an other hand, the axial center portion of each space between tubes, shown at 39 in Fig. 9, is released for enabling an axial flowing of the fluid F2 between the inlet and outlet apertures for the fluid F2 in the housing 1 , the internal space of which is divided into an inlet space 40 and an outlet space 41 , that are separated by a seal tightness ring 42. The spaces 40 and 41 are delimited at ends of the housing 1 by means of header plates 43 and 44. The header plates 43 and 44 are mounted in a seal-tight manner in the housing 1.

In Fig. 9, the fluid F1 circulates through the heat exchanger in a single pass. Obviously, it could also be used a pin shaped circulation. In this case, the housing 1 will be closed at the header plate 44, and the header plate 44 will be part of a transfer header tank of a same type as the header tank 12 of Fig. 1. With respect to the fluid F2, flowing of this fluid could also be made according to a profile in a plurality of crossed passes. Now, with respect to the center s axial portion of the axiai flowing of the fluid F2, it could also be made by providing two sets of juxtaposed fiat tubes, as shown at 46 and 47 in Fig. 9.

Lastly, the channels could have any longitudinal shape, i.e. a rectilinear shape, a corrugated shape, or could even be formed by portions of intercallary parts that are laterally shifted as shown in Figs. 10 and 11. Fig. 11 shows a plurality of portions of intercalary parts 48-52 that are shifted and form therefore a network of communicating channels 53 in zig-zag. It should be noted that, which is important for the thermal performance of the heat exchanger, is the exchange surface obtained by the mounting of the intercalary parts.

Obviously, various modifications can be brought to the different variants of embodiment which have just been described, without departing from the scope of the invention. Thus, the transfer and return tank could be omitted, by using pin shaped flat tubes. Besides, the use of flat tubes enables to greatly reduce the number of tubes, so that, in the case of the invention, such pin shaped tube profile, that implies different sizes for each tube, remains an alternative which is greatly valuable, where the transfer header plate could be of a circular shape, as shown in Fig. 9.

In any way, with respect to the prior art, this invention has very . important advantages to the. known heat exchangers as far as it substitutes, a great number of separate tubes used in these known heat exchangers by a number of relatively small fiat tubes but the inner space of which is divided, as the space between adjacent tubes, by means of intercalary strips into a great c number of channels. To. the mechanical advantages of the invention, there is thus added an improvement of the thermal performance with respect to the state of the art.

Although the fluids F1 and F2 may be of any suitable kind, they are typically formed by liquids.

It should be noted that the use of flat tubes has the very important advantage to solve the seal tightness problem which was raised in the known plate type arrangements with a closing of the inner space by means of end bars. Actually, in particular when high pressure fluids are used, the seal tightness at the assembly of the bars to the plates is questionable, and leaks are produced. Thanks to the tubes, in the case of the invention, a perfect seal tightness is provided, even with high pressure fluids.

An other major advantage of the invention lies in the fact that the assembly of the components of the heat exchanger is made easy. Actually, the relatively thick header plates in which the tubes are fitted will provide, upon the assembly procedure, the reciprocal necessary holding of the parts to be assembled. This enables to omit the specific holding devices that are required upon assembly of plate type heat exchangers.

Moreover, the use of flat tubes enables also to provide heat exchangers with a plurality of transverse passes of the fluid F2, as this is shown in Fig. 12, without the structure and mounting of the heat exchanger be complicated, and without the risk of seal tightness defects be increased as much. Actually, as shown in this figure, it suffices to introduce intercalaray parts 22 into the spaces 18 between two adjacents flat tubes that are perfectly held by the header plates at their ends and to provide, within the housing 1 , suitable transverse partition walls 54, that are fixed at one end to the housing 1 by leaving, at the other end, a passage 55 in order to cause the fluid F2 to pass in a multipass flowing as this is shown by arrows. The passage 55 could be made in the shape of a window in a partition wall fixed in a seal-tight manner to the housing, as this is shown at the left hand side of Fig. 12.

Claims (2)

WHAT IS CLAIMED IS:

1. A heat exchanger comprising: a hollow housing; a plurality of flat tubes, each flat tube having an internal space and, in cross-section, larger and smaller axes perpendicular to each other, said flat tubes being stacked in a direction perpendicular to the larger axis, parallel and spaced from each other; first intercalary means made of a thermally conducting material and disposed within the internal spaces within said flat tubes, dividing the internal spaces of said flat tubes into a plurality of first flow channels for flow of a first liquid at a first temperature, the first flow channels extending axially in said hollow housing; second intercalary means made of a thermally conducting material and disposed between adjacent pairs of said flat tubes, dividing spaces between adjacent pairs of said flat tubes into a plurality of second flow channels for a second fluid, a first fluid flowing at a first temperature through the first flow channels being in thermal exchange with a second fluid flowing at a second temperature, different from the first temperature, through the second flow channels; an inlet/outlet header tank including an inlet/outlet header plate sealed to first ends of said flat tubes for flow of the first fluid, said inlet/outlet header plate being rigidly secured to said hollow housing; and a fluid return header tank including a header plate to which second ends of said flat tubes are sealed for returning flow of the first fluid, said header plate not being connected to said hollow housing, wherein said inlet/outlet header is separated into an inlet portion and an outlet portion, said plurality of flat tubes comprises flat tubes extending between the inlet portion of said inlet/outlet header and said fluid return header tank, and flat tubes extending between said fluid return header tank and the output portion of said inlet/outlet header, said hollow housing comprises an inner space separated by a partition wall into at least first and second space parts, the first space part being a second fluid inlet space and the second space part being a second fluid outlet space, said hollow housing comprises inlet and outlet openings communicating respectively with said second fluid inlet space and said second fluid outlet space and situated adjacent said inlet/outlet header and said fluid return header, respectively, and said second flow channels comprise channels extending in said second fluid inlet space, transverse to an axis of said hollow housing, in one direction, and channels extending in said hollow housing, transverse to the axis of said hollow housing, in a direction opposite to said channels extending in said second fluid inlet space, transverse to the axis of said hollow housing, and said first and second space parts communicate with one another through an opening in said partition wall.

2. The heat exchanger as set forth in claim 1 , wherein said first and second intercalary means comprise corrugated strips fixed to inner and outer surfaces of said flat tubes. For the Applicants, REINHOLD COHN AND PARTNERS