CH338211A - Tube heat exchanger - Google Patents

Description

Tube heat exchanger In tube heat exchangers where the fluids circulate parallel to the tubes, generally against the current, it is advisable, particularly in the case where the temperature difference between the two fluids which 6exchange their heat is low, for example of the order of 20 to 50, to have large exchange surfaces, per unit volume.

The subject of the present invention is a heat exchanger with tubes comprising tubes provided with longitudinal fins, on their external surface at least, the exchanger being traversed by two fluids circulating parallel to the tubes, one external laterally, the other internally and elements to delimit the spaces offered to the flow of one of the fluids.

This heat exchanger is characterized in that these elements have a general direction parallel to that of the tubes and are corrugated in this direction so as to vary the passage section offered to the external fluid.

The accompanying drawing shows, by way of example, several embodiments of the heat exchanger forming the subject of the present invention.

Figs. 1 to 4 are cross-sections of various sections of heat exchanger tubing.

fig. 5 is a cross-section of a first form of heat exchanger using the tube of FIG. 1.

fig. 6 is a perspective view of a detail. fig. 7 is a section of a variant.

fig. 8 is a section of a heat exchanger with tubes of generally circular section, comprising two different numbers of fins.

fig. 9 is a section of a variant in which the tubes are generally rectangular in section, H-shaped, with different numbers of fins on the two faces provided with H-fins.

fig. 10 represents in perspective a tube of FIG. 8 undulates along its longitudinal axis.

fig. 11 schematically represents the tube corrugations of FIG. 10, juxtaposed to form an exchanger.

fig. 12 shows, in perspective, a tube with two longitudinally corrugated fins.

fig. 13 shows a cross-section of a portion of a heat exchanger with corrugated plate blades interposed between the fins of the tubes.

fig. 14 represents in perspective one of the blind cores used inside the tubes of FIG. 13.

fig. 15 represents in perspective RTI ID="0001.0270" WI="6" HE="4" LX="1739" LY="2180"> a variant of a portion of H-section tubes, and corrugated fins on the one side of the H.

fig. 16 shows in section a portion of a heat exchanger with corrugated finned cores.

fig. 17 reproduces in section a part of the exchanger of FIG. 16 with tubular cores. fig. 18 is a longitudinal section of the tubular core of FIG. 17. Fig. 19 is a section by III-III of a detail of fig. 17.

The heat exchanger tubes which are used have on their internal surface and on their external surface, or at least on one of these faces, longitudinal fins, that is to say directed in the direction parallel to the axis. tubes, and whose first profile, for example of triangular section with a rounded angle, is of a height varying from the order of a few millimeters to one or more centimeters.

These fins are adapted to the importance of the heat exchanger that has to be made between. two fluids, and to the intrinsic qualities of each of the fluids.

To specify, in the case where the temperature difference between the two fluids which exchange their heat is low, the height of the fins is relatively reduced because a greater height would be inefficient. In fact, the temperature difference necessary for the conduction of heat from the top to the bottom of a fin quickly exhausts the temperature difference available to it, and a fin, long or high, no longer has any reason to 'be. On the contrary, in the case where there is a large temperature difference between the two fluids, the fins can be higher.

On the other hand, the intrinsic qualities of the fluid, that is to say its nature, liquid or gaseous, its speed, its pressure, its specific heat, its viscosity which condition the transmission coefficient of the fluid with the metal, are find to determine the number of fins; that is to say, if the transmission coefficient is high, it suffices that the fins are few in number and if the transmission coefficient is bad, the fins will be in greater number.

In summary, the temperature difference between fluid and metal conditions the profile of the fins, and the intrinsic properties of the fluids, their number.

For example, in the first case of a heat exchanger between gas and water. as it is used in atomic installations, the difference between the two fluids is of the order of 20 to 500. the height of the fin will not exceed 1 cm and the number of fins will be about twenty at the outer surface of the tube. On the contrary, at the interior, which is swept by water, which has an excellent coefficient of transmission with RTI ID="0002.0278" WI="3" HE="4" LX="807" LY="2260"> the metal, a few fins a few millimeters high will suffice, or even no fins will be necessary.

In fig. 1, the tubes have an approximately equal number of fins, of the same height, on the internal face and the external face.

In fig. 2, tubes b have higher fins on the external surface than on the internal surface, and those on the internal surface are fewer. It is the reverse in the case of FIG. 3, where it is the fins of the internal surface which are high and numerous.

Finally. in the first case of FIG. 4, an has provided, by way of example, a form of execution in which the fins of the outer surface, few in number and relatively thick, are themselves grooved on their faces to produce a kind of indentation. - fellow. Ort thus multiplies, as in all other cases, the area of the heat exchange surfaces of the tube.

The exchanger as represented in fig. 5, consists of rowfies of tubes a, such as that of fig. 1, arranged in staggered rows and which are internally traversed by a fluid. The external fluid also circulates parallel to the lines of the tubes, counter-current for example, in the spaces between the tubes. To reduce the passage section of the internal fluid, and force it to circulate more quickly in the grooves provided between the fins while & trusing the adherent film of fluid, blind cores e are provided at the inside of the tubes. and leave between their outer surface and the inner surface of the tube a relatively narrow passage. Similarly, between the tubes a are provided externally blind cores such that f adopts the section is that of a square with curvilinear sides, which adapts, as seen in fig. 5, to the outer shape of the tubes, to provide around them relatively small cross-section corridors traversed by the first external fluid.

In order to achieve variations in section and variations in direction in the passages thus offered to the fluids, both inside and outside the tube, an can corrugate the cores e and f longitudinally, like an a represented in perspective for the nucleus f in fig. 6. These nuclei can be constituted by simple coiled or folded sheets, as seen in fig. 6. In fig. 5, an has hatched these nuclei to show that they were not used for circulation, but they are not necessarily full for <RTI ID="0002.0552" WI="7" HE="4" LX="1502" LY ="1901"> this.

Similarly, the fins provided both outside and inside the tube, instead of being exactly directed along the generatrices of the tube, can be corrugated, that is to say the tubes can be subjected twisting around their axis, so as to obtain a helical or pseudo-sinusoidal winding of the fins on the surfaces of the tube.

If necessary, and to arrange the tubes of the exchanger in the most rational way within the space available to them, these tubes, instead of being of circular section as represented on the figures - figures, could be of square section, or polygonal, or of any other shape, by adapting to this section a corresponding section of the cores to achieve a compact assembly.

0n has shown, by way of example, in FIG. 7, a variant in which each tube g has on its outer face fins of unequal height falling, as seen in the figure, inside a square h. Similarly, the fins of the internal surface are of unequal height and are circumscribed around an internal square i, offset with respect to the first so that the highest fins correspond On the external and internal faces.

This square shape allows the tubes to be juxtaposed, as shown in the figure, in the manner of parquet slabs. Inside the tubes g, the cores j have a square section, approaching that of the inner square i.

Intervals can be arranged between the square sections h of the tubes g, in which blades k are arranged, which can also be corrugated in the direction of the flow of the external fluid, so as to obtain in these intervals variations in section and direction in the flow of the external fluid. These blades k can all be arranged in the horizontal direction only, or in the vertical direction, or in both as shown in the figure.

It is also possible to use, for example, as shown in FIG. 8, tubes of circular section arranged in staggered rows, but in every other row, for example the row A A, the tubes l which comprise eight fins on their external face, alternating with tubes m having six fins . In this way. the fins of the tubes <I>1</I> and, m can fit into each other, so that the space left to the external fluid is sufficiently restricted and that it is no longer necessary to provide between the tubes, blind nuclei.

Of course, blind cores e can also be provided inside the tubes.

In the variant represented in fig. 9, the general section of each tube n of the exchanger is H-shaped, which allows a very compact compaction of the tubes, by interposing the fins provided on the opposite faces of the tubes n. 0n will notice that, to obtain a regular assembly such as that shown in fig. 9, each tube n comprises five fins o On one of these faces and only four fins p On the other face, the fins p of a tube interlocking, as seen in FIG. 9, in the fins or of the tube located immediately above.

The tubes, as shown in Figs. 8 and 9, may have fins q on their internal face, and these fins are preferably, like anRTI ID="0003.0278" WI="3" HE="4" LX="977" LY="2203"> 1e see In the figures, offset from the spaced fins provided on the outer surface.

Each tube <I>1, m, n,</I> can also be corrugated in the direction of its longitudinal axis, symmetrically or asymmetrically, as shown in perspective in FIG. 10. 0n thus produced between the tubes of the exchanger, ripples as year 1'a indicates schematically fig. 11 for three tubes, intervals between tubes presenting variations of direction and section for the external fluid and of direction for the internal fluid, variations which are favorable to the exchange of heat.

In fig. 12, the tube r which has six longitudinal and diametrical fins on its outer surface is such that one fin out of two, namely the fin s, is corrugated in the longitudinal direction of the axis of the tube, in an asymmetrical manner, this being That is, a long undulating Branch is followed by a shorter, steeper Branch. The other fins t remain flat and diametrical. In this way, in the channels which are formed between the fins, overlapping or not, of the tubes associated to constitute the exchanger and where the external fluid circulates, there are variations in section and direction which have the effect of improve heat exchange.

Instead of corrugating the fins such as s, an can weld, or fix by a few spot welds, On the tube itself r, between the fins which remain flat, Strips of corrugated sheets u, as in 1'a represented in punctuated lines In fig. 12. These sheets can then be fixed by a few spot welds, by their other edge either on a fin of another tube associated with the first to constitute the heat exchanger, or on the wall of this tube itself. . This edge can still remain free.

In fig. 13, an has shown in section, an arrangement in which tubes r, with six flat fins on the outer surface, are staggered, the ends of the fins coming close to each other and of the sheets v are welded together. fin to fin, to delimit the spaces offered to the flow of the external fluid, and to obtain, in these spaces, the desired variations of direction and section.

Of course, these sheets v do not contribute strictly speaking to the heat exchange, but simply to modify the flow conditions of the external fluid.

The sheets v could also be welded, as said above, from the wall of a tube to the RTI ID="0003.0551" WI="8" HE="4"LX="1846" LY="1791"> wall from another pipe. The choice of the layout of the sheets v depends on the layout adopted for the assembly of the tubes, depending on whether the fins fit more or less into each other, and the sheets v are arranged in such a way that the channels remaining between the fins are appropriately subdivided.

The arrangement of longitudinal corrugations on some of the fins of the outer surface of the tube is applicable to all shapes of tubes and in particular to the shape of H-section tubes. In this case, the fins p1 of one of the sides of the tube q are corrugated and the fins o of the other side remain flat and the tubes being nested one inside the other as seen in fig. 15, the corrugated p1 fins create variations in direction and section in the gaps remaining between the flat fins o of the tube located immediately above.

In Figs. 12 to 15, the tube has no fins on its inner surface, but the blind core which is arranged inside the tubes, as seen in fig. 13 and 14 presents, on the contrary, on its outer surface, small fins, or ribs w. These ribs w can preferably be corrugated as seen in w1, and cause, in the channels offered between the core e and the tube r for the flow of the internal fluid, variations in direction, while allowing also the centering of the core e inside the tube r.

In fig. 16, the outer finned tubes are arranged in regular rows. The section of these tubes fits as seen in a square and the external fins provided on the tubes are of different lengths for this purpose. Note that the fins terminating in the corners of the edge are a little shortened, so that the edge is at blunt angles. In this way, between four contiguous r tubes whose axes are at the top of a square. it is possible to house a core x whose body is placed between the extremities of the four fins of the four contiguous tubes and whose axis coincides with the center of the square. The cores x have four fins x1, which are inserted between the fins of the tubes r, so as to subdivide the space comprised between these fins.

The body of the core <I>x</I> can be grooved in <I>x2</I> as seen on the right of the figure, so that the tips of the fins of the tubes r come out of it. - Gagent in these grooves, which ensures the first wedging of the tubes and their maintenance in place.

The fins x1 are preferably corrugated Ion gitudinally, so that it occurs, in the spaces between the fins x1 and the fins of the tubes r, variations of direction and section which show, as we know, favorable ä Fdheat exchange. During assembly, a horizontal row of finned tubes r, having been put in place, an can then arrange the cores x, either by introducing them from the top, or by threading them horizontally on the two fins of the tubes with which said nuclei must cooperate.

In a variant also represented on the left of FIG. 16, the outer core y does not have grooves like the cores x, but these grooves are replaced by spot welds y1, arranged spaced apart from the faces of the horizontal fins. These welding points form a stop RTI ID="0004.0280" WI="8" HE="4" LX="538" LY="2115"> for the fins of the tubes r with which the cores in question cooperate. This form of execution facilitates the manufacture of the cores y which is made more economical. On the other hand, it allows the positioning, by stacking successive horizontal layers, of the r tubes and the y cores.

Inside the tubes r, there are provided solid cores e having longitudinally undulating ribs w, or wound in helices, and which have the effect of varying the section and the direction of the intervals provided between the said cores e and the inner surface of the tubes r.

The heat exchanger fig. 17 is formed of tubes r, with longitudinal fins, between which are arranged solid cores with corrugated fins x and these tubes r, instead of being partially closed off by a solid core, are closed off by a tubular core e1. The tubular core e1 bears externally, as did the solid core, ribs w arranged in Mlice, as seen in fig. 18, so as to cause a movement of gyration and variations in section in the space offered to the fluid circulating inside the tubes r and outside the cores e1. But the tubular construction of the core e1 above all makes it possible to circulate a fluid inside this core, which may be the fluid circulating externally to the tubes r, which thus passes on either side of the fluid circulating internally to the tubes r and externally to the nuclei e1.

Tubular cores e1, deviator cores 1 can be arranged inside, as seen in FIG. 18 known per se, and which have the effect of varying the internal passage section of the fluid inside the core e1, in order to obtain effects of beats in the speed, the pressure and the direction. fluid, which improves heat exchange.

It can also be arranged, at the entrance to the cores e1, a head 2 shaped so as to impart to the fluid current a gyratory movement which comprises helical ribs 3, as seen in FIG. 18.

When, as is the case for the embodiment represented in FIG. 17, the tubes of the exchanger are arranged vertically, the fins r of the finned tubes come with their tips into the hollow of the outer cores x and there is provided in this hollow, at the top of the cores x, a small crosspiece 4 which engages in a notch 5 provided in the tip of Failette as seen in FIG. 19. Of the RTI ID="0004.0554" WI="8" HE="4" LX="1239" LY="1661"> so, the outer cores x serve as suspension points for the finned tubes r.

Claims (10)

CLAIM Tube heat exchanger comprising tubes provided with longitudinal fins on their external surface at least, the exchanger being traversed by two fluids circulating parallel to the tubes, one externally, the other internally and elements to delimit the spaces offered to the flow of one of the fluids, characterized in that these elements have a general direction parallel to that of the tubes and are undulated in this direction so as to vary the section of passage offered to the external fluid. SUB-CLAIMS 1. Heat exchanger according to claim, characterized in that the finned tubes are corrugated in the longitudinal direction. 2. Heat exchanger according to claim, characterized in that cores (e) constituting said elements are arranged inside the tubes, these cores (e) presenting fins (w1) undulating in the first longitudinal direction. 3. Heat exchanger according to claim, characterized in that some of the fins (s) of the finned tubes are corrugated while the others (t) remain planar. 4. Heat exchanger according to claim, characterized in that said elements are constituted by plates (u, v) corrugated in the longitudinal direction, welded by their longitudinal edge at least on the tubes (r) with fins . 5. Heat exchanger according to sub-claim 4, characterized in that said sheets are welded to the outer surface of said tube. 6. Heat exchanger according to sub-claim 4, characterized in that said sheets are welded to the fins of said tube. 7. Heat exchanger according to claim, characterized in that said elements are constituted by outer cores (x) disposed between the tubes and comprising fins (x1) corrugated in the first longitudinal direction. B. Heat exchanger according to sub-claim 7, characterized in that the fins (x1) have grooves (x2) to serve as housing for the ends of the fins of the tubes. 9. Heat exchanger according to sub-claim 7, characterized in that the fins (x1) have pegs (y1) to act as abutment at the ends of the fins of the tubes. 10. Heat exchanger according to sub-claim 8, characterized in that a tubular core (e1) having an internal deviating core (1) is arranged inside each tube (r) so as to constitute a third fluid passage.