WO2007054642A1

WO2007054642A1 - Grooved tubes for heat exchangers with better resistance to expansion

Info

Publication number: WO2007054642A1
Application number: PCT/FR2006/002491
Authority: WO
Inventors: Pascal Leterrible; Gérard Lemaitre
Original assignee: Trefimetaux
Priority date: 2005-11-09
Filing date: 2006-11-08
Publication date: 2007-05-18
Also published as: DE602006011939D1; FR2893124B1; ES2341626T3; EP1949012B1; FR2893124A1; EP1949012A1; ATE456017T1

Abstract

The grooved metal tubes (1), with a thickness Tf at the bottom of the groove, and an outside diameter De, typically intended for the manufacture of heat exchangers or batteries (4) using a cold-transfer or heat-transfer fluid of single-phase or diphase type, the said tubes (1) being internally grooved with N helical ribs, where N ranges from 20 to 80 according to the outside diameter De, of apex angle α, of height H in a radial direction (11) of the said tube, and of base B of width LN and of helix angle β, two consecutive ribs being separated by a groove (3), the bottom (30) of which is typically flat and of width LR, with a spacing P equal to LR + LN, are characterized in that: a) the said widths LN and LR are such that LN/LR is between 0.40 and 0.80; b) the said N ribs have a mid-height width LN1/2 at least equal to 2.LN/3; c) the said N ribs are inclined oblique ribs (2), and in which the said rib (2) is a rib (2’) that has a tetragonal cross section.

Description

GROOVED TUBES FOR RESISTANCE THERMAL EXCHANGERS

IMPROVED EXPANSION

FIELD OF THE INVENTION

The invention relates to the field of tubes for heat exchangers, and more particularly the field of heat exchanger tubes using either a so-called "monophasic" fluid, that is to say a fluid for which the heat exchange does not include not a cycle of evaporation and condensation, a so-called "two-phase" fluid, that is to say a fluid that puts its stake latent heat of vaporization and condensation.

STATE OF THE ART

A large number of documents are known describing the geometry of grooved tubes used in heat exchangers.

By way of example, mention may be made of patent application EP-A2-0 148 609, which describes tubes with triangular or trapezoidal grooves having the following characteristics:

an H / Di ratio of between 0.02 and 0.03, H denoting the depth of the grooves (or the height of the ribs), and Di the inside diameter of the grooved tube,

a helix angle β with respect to the tube axis of between 7 and 30 °, a S / H ratio of between 0.15 and 0.40, with S denoting the cross section of the groove,

an apex angle α of ribs between 30 and 60 °.

These tube characteristics are adapted to phase transition fluids, the performance of the tubes being analyzed separately during the evaporation of the fluid and during the condensation of the fluid.

Japanese Application No. 57-58088 discloses V-grooved tubes, with H between 0.02 mm and 0.2 mm, and with an angle β between 4 ° and 15 °. Neighboring tubes are described in Japanese Application No. 57-58094.

Japanese Application No. 52-38663 discloses tubes with V or U grooves, with H between 0.02 and 0.2 mm, a pitch P between 0.1 and 0.5 mm and an angle β between 4 and 15 °.

U.S. Patent No. 4,044,797 discloses V or U groove tubes adjacent to the preceding tubes.

Japanese Utility Model No. 55-180186 discloses trapezoidal grooves and triangular ribs, with a height H of 0.15 to 0.25 mm, a pitch P of 0.56 mm, an apex angle α (angle called θ in this document) typically equal to 73 °, an angle β of 30 °, and an average thickness of 0.44 mm.

U.S. Patent Nos. 4,545,428 and 4,480,684 disclose V-grooved and triangular-shaped tubes with a height H of 0.1 to 0.6 mm, a pitch P of 0.2 to 0, 6 mm, an apex angle α between 50 and 100 °, a helix angle β between 16 and 35 °.

Japanese Patent No. 62-25959 describes tubes with trapezoidal grooves and ribs, with a groove depth H of between 0.2 and 0.5 mm, a pitch P of between 0.3 and 1.5 mm, the width average of the grooves being at least equal to the average width of the ribs. In one example, the pitch P is 0.70 mm and the helix angle β is 10 °.

Also known is the European patent EP 1 061 318 describing triangular tubes with inclined triangular shapes able to be deformed by folding when fins external to the tube are crimped to the tube to form heat exchangers.

Finally, the European patent EP-B1-701 680, in the name of the applicant, describes grooved tubes, with grooves with a flat bottom and with ribs of different height H, with a helix angle β of between 5 and 50 °. , of apex angle α between 30 and 60 °, so as to obtain better performance after crimping the tubes and mounting in the exchangers. In general, the technical and economic performances of the tubes, which result from the choice of the combination of means defining the tubes (H, P, α, β, form grooves and ribs, etc.), are generally relative to four types of considerations: - on the one hand, the characteristics relating to the heat transfer (heat exchange coefficient), area in which the grooved tubes are much greater than the non-grooved tubes, so that equivalent heat exchange, the length grooved tube required will be less than that of non-grooved tube,

- On the other hand, the characteristics relating to pressure drops, low pressure losses allowing the use of pumps or compressors of lower power, size and cost,

- in addition, the industrial feasibility of the tubes and the speed of production which conditions the cost price of the tube at the tube manufacturer,

- Finally, the characteristics relating to the mechanical properties of the tubes, typically in relation to the nature of the alloys used or the average thickness of the tubes, which thickness determines the weight of the tube per unit length, and therefore affects its cost price .

PROBLEMS POSED

On the one hand, as is the result of the state of the art, there is a large number and a great diversity of teachings with regard to the grooved tubes, knowing that they generally aim at the optimization of the heat exchange and the reduction of the pressure drop. On the other hand, each of these teachings itself usually offers a wide range of possibilities, the parameters being generally defined by relatively wide ranges of values, so that the skilled person already has many difficulties to draw. the quintessence of the state of the art, among so many data, sometimes contradictory.

In addition, these teachings are most often grooved tubes considered as such, grooved tubes that can optionally be used in tabular exchangers. However, the grooved tubes can also be used in heat exchangers or batteries that include heat diffusing fins. In this case, the tubes are secured to the fins by crimping which requires an expansion of the tube made by a mechanical part, typically a ball, of diameter chosen to achieve an expansion of the tube, which tends to crush mechanically or to bend said grooves during said expansion.

While attempts have already been made to make tubes relatively resistant to crushing, as a general rule, even these tubes represent an improvement over other tubes, but they still exhibit a relatively large deformation which decreases very significantly. its performance and its heat exchange capabilities.

In addition, the tubes should be able to withstand increasingly severe crimping conditions so as to maximize the mechanical contact area between the tube and the fins, so as to simultaneously increase the strength of the batteries and the thermal conduction between the tubes and the fins. Finally, another problem, which is essential at the industrial level, is the possibility of manufacturing grooved tubes, because there may be profiles of grooved tubes which would be, in theory at least, excellent, but in practice if not impossible at least difficult to make, or impossible to manufacture from non-grooved tubes. In addition, it should be that these tubes can be manufactured with sufficient productivity and with equipment or investment that is not greater than that of grooved pipes of the state of the art.

The Applicant has therefore researched and developed tubes and exchangers that can be used either in tabular exchangers, or in finned exchangers or batteries, the developed tubes having both a very high resistance to deformation during said expansion high heat exchange performance, a relatively low pressure drop so as to limit the power of the compressors and circulation pumps of the fluids circulating in said tabes, for applications or fields that use monophasic or biphasic fluids, and that can be manufactured with productivity and equipment as in the case of grooved pipes already industrialized.

DESCRIPTION OF THE INVENTION

According to the invention, the groove metal tube, of thickness T _f at the groove bottom, of external diameter De typically ₅ for the manufacture of heat exchangers or batteries using a secondary refrigerant or coolant fluid monophasic or biphasic, said tube being internally grooved by N helical ribs, with N ranging from 20 to 80 depending on the outside diameter De, apex angle α, height H in a radial direction of said tube, base B of width L _N and of β helix angle, two consecutive ribs being separated by a generally flat bottom groove of width L _R , with a pitch P equal to L _R + L _N , is characterized in that: a) said widths L _N and L _R are such that L _N / L _R is between 0.40 and 0.80, b) said N ribs have a half-height width L _NI / 2 at least equal to 2.L _N / 3 c) said N-ribs are oblique ribs, inclined, typically in the same direction, of an angle γ by rap port at said radial direction from 10 ° to 35 °, said angle γ being the angle formed between said radial direction and a median line passing through the middle of said base B of said rib and by the middle of the width of the rib taken at its mid-height H / 2, and in this tube, said rib is a rib which has a tetragonal section comprising, in addition to its base B, an upper side S facing said base B, and two lateral sides CL ₁ and CL ₂ between them forming said apex angle α, one CL ₁ (22) makes an angle G ₁ less than 90 ° with said bottom groove (30) adjacent, and the other CL ₂ (23) makes an angle θ ₂ typically greater than 90 ° with said adjacent groove bottom (30), so as to have a high crush resistance, high heat exchange capacities and low pressure drop, when said tube is secured to cooling fins in a battery. These ribs are said oblique and inclined because they have a lateral side (CL ₁ ) making an angle B ₁ less than 90 ° with said groove bottom (30) adjacent. These ribs are typically identical to each other.

The tubes according to the invention solve the problems posed.

Indeed, the applicant has observed that with the grooved tubes according to the invention:

on the one hand, after expansion, even under the most severe conditions, the ribs of these tubes pass from a height H to a height H ¹ such that H '/ H is at least 0.85, whereas 'with traditional tubes, this ratio is less than 0.85. - On the other hand, as will appear with the examples, the performances have high heat exchange capacity, and this with a typically lower pressure drop.

- Finally, as regards the manufacture of these tubes, it can be performed by grooving non-grooved tubes, which is advantageous in practice, and this, with a productivity and equipment and a rate similar to those of the manufacturing processes. traditional grooved tubes already industrialized.

DESCRIPTION OF THE FIGURES

FIG. 1a schematically represents a groove tube portion (1) of axial direction (10) internally bearing a plurality of helical ribs (2) with a helix angle β with respect to its axial direction (10), as shown in FIG. the left part of the figure in partial section along said axial direction (10). Figure Ib is a partial section of the groove tube (1) in a transverse plane perpendicular to said axial direction (10).

FIG. 2a is a schematic representation, in section in the axial direction (10), to illustrate the expansion of a smooth tube during crimping of the tube (1) and the fins (5) by passing a ball (6). ) in the tube (1). FIG. 2b is a perspective view of a battery (4) formed by crimping a plurality of tubes (1) in a plurality of fins (5) oriented perpendicular to the axial direction (10) of the tubes (1). . Figure 2c is a sectional view of a tabular heat exchanger in which the tubes (1) forming a beam do not have to be expanded as in the case of the battery (4) of Figure 2b.

Figures 3a to 4b are partial sections of tubes, in section along a transverse plane perpendicular to said axial direction (10).

Figures 3a and 3b relate to tubes (1) before expansion. These figures according to identical, and are distinguished in that Figure 3b carries measurement values for certain parameters.

Figures 4a and 4b relate to the same tubes after expansion. These figures according to identical, and are distinguished in that Figure 4b carries measurement values for certain parameters.

FIGS. 5a and 5b are diagrams that illustrate the performances of a tube A according to the invention, compared to a groove tube B of the state of the art and to a non-grooved tube C, in evaporation at 8 ° C. Reynolds number function Re, the fluid being brine.

Figure 5a gives the ordinate the exchange coefficient Hi (Wm ² .K) as a function of the Reynolds number Re on the abscissa.

FIG. 5b gives the ordinate the pressure drop (Pa / m) as a function of the Reynolds number Re on the abscissa.

Figure 6a is an axial section illustrating a channel grooving device (7).

Figures 6b and 6c relate to a grooving mandrel (70) having a plurality of helical grooves (700), the pitch of these grooves (700) being on the left, these grooves also being inclined to the left.

Figure 6b is a composite view including a cross-sectional view in a plane perpendicular to the axial direction (10) and a perspective view from above for an observer placed at the rear of the grooving mandrel (70). Figure 6c is a top view, an oblique arrow pointing to the left indicating the left inclination of the grooves, another axial arrow indicating the direction of movement of the tube relative to the mandrel (70).

Fig. 7 is a cross-sectional view of the groove tube (1) formed by radial compression between the grooving mandrel (70) inside the tube, and the plurality of balls (711, 711 ') outside the groove tube.

In this figure, said grooving mandrel (70) is that of Figures 6b and 6c, its cross section being that shown on the lower part of Figure 6b, and the direction of rotation of the rotary cage (710) is the direct direction in a clockwise direction, the observer looking in the axial direction (10) corresponding to the direction towards which said tube (1) is drawn.

Under these conditions, the groove tube (1) has a plurality of ribs (2) having no defect.

Figures 8a and 8b are similar respectively to Figures 6c and 7.

FIG. 8a shows a grooving mandrel (70) which differs from that of FIG. 6c in that the helical grooves (700) are inclined to the right, instead of being inclined to the left, an oblique arrow pointing to the right indicating the inclination to the right of the grooves.

FIG. 8b is similar to FIG. 7 and is distinguished in that the grooving mandrel (70), which is that of FIG. 8a, has grooves (700) inclined to the right, instead of being inclined at left, the direction of rotation of the rotary cage (710) being the direct direction.

Under these conditions, the groove tube (1) has a plurality of ribs (2) which have defects, the ribs being more or less poorly formed or incompletely formed.

Figures 9a and 9b are similar to Figures 8a and 8b.

FIG. 9a shows a grooving mandrel (70) identical to that of FIG. 6c, which has a plurality of helical grooves (700) inclined to the left and with a not on the left, an oblique arrow pointing to the left indicating the inclination to the left of the grooves.

FIG. 9b is similar to FIG. 8b and is distinguished in that the grooving mandrel (70), which is that of FIG. 9a, has grooves (700) inclined to the left, instead of being inclined at right and in that the direction of rotation of the rotary cage (710) is the opposite direction.

Figures 10a and 10b are similar respectively to Figures 8a and 8b. Figure 10a shows a grooving mandrel (70) identical to that of Figure 8a, an oblique arrow pointing to the right indicating the right inclination of the grooves.

Figure 10b is similar to Figure 8b and differs in that the direction of rotation of the rotary cage (710) is reversed instead of being direct.

Under these conditions, the groove tube (1) has a plurality of ribs (2) having no defect, as in the case of the tube obtained according to FIGS. 6a to 7.

FIGS. 11a to 11c, similar to FIGS. 3a and 3b, are partial sections, in section in the axial direction (10), of tubes (1) before expansion.

FIG. 1a is identical to FIG. 3a and illustrates the case where said ribs (2) are inclined or oblique ribs forming an angle γ with said radial direction (11) forming an angle of 90 ° with the outer wall of the tube and passing through the geometric center of the tube.

FIG. 11b illustrates the case where said ribs (2) are in the form of an alternation of inclined ribs of height H1 and height H2 <H1. Figure 11a, similar to Figure 11a, but on a different scale, illustrates the case where a straight rib (2 ") of height H '<H are interposed between two inclined ribs (2).

DETAILED DESCRIPTION OF THE INVENTION

According to the embodiment of the invention illustrated in FIGS. 1b and 3a to 3b, said rib (2) may be a rib (2 ') which has a tetragonal section comprising, in addition to its base B (20), an upper side S ( 21) opposite said base B (20), and two lateral sides CL ₁ (22) and CL ₂ (23) forming between them said apex angle α, one of which CL ₁ (22) forms an angle B ₁ less than 90 ° with said adjacent groove bottom (30), and the other CL ₂ (23) makes an angle θ ₂ greater than 90 ° with said adjacent groove bottom (30).

According to the invention, said rib (2) may have a width at half height L _N1Z2 at least equal to 0.65.

Typically, said rib (2) may have a width at half height L _{NI / 2} at least equal to 0.70.L _N -

Preferably, said rib (2) may have a half-height width L _N1Z2 at least 0,75.L _N -

Indeed, the ribs (2) according to the invention have a shape quite far from the conventional triangular shape, so that the width at half height is only slightly less than the width of the base B (20) of the rib, the lateral sides being almost parallel.

Said apex angle α formed by said two lateral sides CL ₁ (22) and CL ₂ (23) can range from 10 ° to 35 °.

In FIG. 3b, an angle α of 22.4 ° has been indicated, but the invention makes it possible to obtain industrially tubes with ribs (2, 2 ') having a much smaller angle α, typically 10-15. °.

As also illustrated in Figures Ib and 3a to 3b, said upper side S (21) may have a width at least equal to 0.3.L _N , and reference at least 0.4.L _N - U

In addition, said upper side S (21) can be inclined relative to said base B (20) with an angle δ ranging from 5 ° to 35 °.

Said angle δ may have its top typically closer to said lateral side of the lateral side CL ₂ (23) than the CL ₁ side (22).

According to the invention, said ribs (2, 2 ') may advantageously be of height H such that H / De is equal to 0.020 ± 0.005, H and De being expressed in mm. Similarly, the number N of ribs (2, T) may be such that N / De is equal to 4.5 ± 0.5, the corresponding pitch P being equal to π.Di / N, with Di equal to De- 2.Tf, and De being expressed in mm.

Said helix angle β can range from 5 ° to 25 °.

It is these parameter ranges that make it possible to obtain all the results obtained with the tubes according to the invention.

Typically, the thickness T _f can be such that T _f / De is equal to 0.03 ± 0.005, T _f and De being expressed in mm, with De ranging from 6 mm to 18 mm. The P / H ratio can range from 1.5 to 3 and preferably 1.7 to 2.3.

As illustrated in FIG. 1b, said lateral sides CL ₁ (22) and CL ₂ (23) can be connected to said adjacent groove bottoms (30) with radii of curvature R that are typically less than 100 μm, and typically less than 50 μm. .

As illustrated in FIG. 11b, said ribs (2, 2 ') can form a succession of ribs of height H1 = H and of height H2 = a.H1, with a between 0.1 and 0.9, the rib of height Hl being the main rib, and the rib of height H2 being the secondary rib, these two ribs being separated by a flat bottom groove.

With this modality, which may be useful in particular cases, only the rib of greater height H1 is affected by the expansion of the tube, while the second height H2 remains intact. As illustrated in FIG. 11c, a straight rib (2 ") may be interposed between two adjacent oblique ribs (2Comm, 2 '), said right rib having a height H ¹ <H or less than H1.

Generally, said rib (2) and said groove (3) may have substantially the shape of parallelograms, the ratio of S _N / S _R surfaces being substantially equal to the ratio L _N / L _R, S _N and S _R denoting the surface respectively said rib (2) and said groove (3).

As can be seen by comparing FIGS. 3a to 3b with FIGS. 4a to 4b, the geometrical shape of the ribs (2, 2 ') according to the invention does not prevent a certain deformation of these ribs and a certain crushing of these ribs, but, on the one hand, this deformation is relatively limited in view of the power and the resistance opposed by these ribs to crushing during the expansion of the tube, and secondly, once deformed, these ribs retain substantially the same shape, so that there is no significant decrease in performance of the tube before and after expansion of the tube.

According to the invention, the tubes (1) can be made of Cu and alloys of Cu, Al and alloys of Al, Fe and Fe alloys.

These tubes (1), typically not fluted, can be obtained typically by grooving tubes, or possibly by flat grooving of a metal strip and forming a welded tube.

These tubes may have a typically round cross section, oval or rectangular, depending on the manufacturing method, a round section being obtained by grooving a smooth round section tube.

Another object of the invention is constituted by heat exchangers or batteries (4) using fins (5) and expanded tubes (I ¹ ) formed by expanding tubes (1) according to the invention. Another object of the invention is constituted by a method of manufacturing grooved tubes in which a non-grooved tube (1 ") is radially compressed on a grooving mandrel (70) provided on its peripheral surface with a plurality of grooves ( 700), by means of a radial compression means (71), so as to form a groove tube (1) having a plurality of ribs (2) on its inner surface, said groove tube thus formed (1 ) being pulled by a traction means (72) in a so-called axial direction (10) of movement of said groove tube (1), said radial compression means (71) and said grooving mandrel (70) remaining fixed relative to said axial direction (10), said grooving mandrel (70) being a mandrel placed inside said non-grooved tube (1 ") and integral with a floating mandrel (73) retained upstream of the grooving mandrel (70) by a holding die (74), said radial compression means (71) comprising a rotary cage (710) having a plurality of members (711), typically a plurality of balls (711 '), rotating about said non-grooved tube (1 ") to the right of said grooving mandrel (70) in a direction of predetermined rotation with respect to said axial direction (10), characterized in that: a) said grooves (700) of said plurality of grooves are helical grooves, of right or left pitch, so as to obtain a groove tube (1) β ≠ 0, b) said grooves (700) of said plurality of grooves are inclined grooves, with a right or left inclination, so as to obtain a groove tube (1) whose ribs (2). have an angle of inclination γ> 0 °, c) one chooses said direction of rotation of said rotary cage (710), said direction being direct or inverse, depending in particular on said right or left inclination of said grooves (700), in order to form said plurality of ribs (2) of said groove tubes (1) in s their completeness, said right or left pitch of said grooving mandrel (70), said right or left inclination of said grooves (700) and said direct or inverse direction of rotation of said rotary cage (710) being determined relative to an observer placed at rearwardly and above said grooving mandrel (70) and looking in said axial direction (10) of said groove tube (1), said direct direction of rotation being that of the clockwise. This method uses a grooving device, for example a grooving device as described in French Patent No. 2,707,534 in the name of the Applicant, Figure 6a which schematizes this process corresponding to Figure 2a of this patent. Indeed, the Applicant has observed that the experimental conditions had a great influence on the result obtained.

A plurality of ribs (2) is correctly formed only under the following conditions: a) when said direction of rotation of said rotary cage (710) is direct, said helical grooves (700) of said grooving mandrel (70) have a left inclination, said pitch of said grooving mandrel (70) being right or left, as illustrated in FIGS. 6b to 7, b) when said direction of rotation of said rotary cage (710) is opposite, said helical grooves (700) of said grooving mandrel (70) have a right inclination, said pitch being right or left, as shown in Figures 10a and 10b.

When these conditions are not respected, the Applicant has observed that the grooves (700) filled incorrectly or incompletely, so that the ribs (2) corresponding to the groove tube (1) were defective.

Another object of the invention is constituted by a method of manufacturing tubes according to the invention, typically not fluted, obtained by flat grooving of a metal strip and forming a welded tube.

EXAMPLES OF REALIZATION

A tube (1) made of copper, as illustrated in FIGS. 1b and 3a to 3b, was manufactured by grooving a smooth tube, using the method according to the invention, using the grooving device illustrated. in Figures 6a-7 using a grooving mandrel (70) having a plurality of grooves (700) inclined to the left, and rotating the rotary cage (710) in the forward direction.

Tubes according to the invention have also been made using the grooving device shown in Figs. 10a and 10b using a grooving mandrel (70) having a plurality of grooves (700) inclined to the right, and rotating the rotating cage (710) in the opposite direction. Tests conducted according to Figures 9a and 9b with the same grooving mandrel (70), but rotating the rotary cage (710) in the opposite direction were negative.

Similarly, tests conducted according to Figures 8a and 8b, with a grooving mandrel (70) having a plurality of grooves (700) inclined to the right, and rotating the rotary cage (710) in the forward direction, were negative.

This tube (1) has an outside diameter of 15.87 mm and a groove bottom thickness Tf of 0.51 mm. The height H of grooves is 0.32 mm.

The number N of grooves is 75.

The diameter Di, equal to De 2 · Tf, is 14.85 mm.

The pitch P, equal to π.Di / N, is 0.62 mm.

The ratio L _N / L _R is 0.59, so that the base B (20) has a width L _N which is approximately 0.23 mm.

Said rib (2) has a width at half height L _{NI / 2} equal to 0.77X _N -

Regarding the angles:

the apex angle α is 22 °

the helix angle β is 20 °. the angle γ is equal to 15 °. This angle is formed between said radial direction (11) and the median line (24) passing through the middle of said base B (20) of said rib (2) and by the middle of the width of the rib (2) taken at its mid-height H / 2.

the angle δ is approximately 18 °.

A cross-section of this tube (1) was made as shown in FIG. 3a and 3b.

The performance of this tube (1) was measured in evaporation at 8 ° C. with brine (27% by weight) as fluid and for different values of Reynolds number Re.

The results are shown in Figures 5a and 5b. The tube A is the tube (1) according to the invention. The tube B is a tube analogous to the tube A (same diameter De, same N, same H, same angle β, etc.) but which differs in that the ribs are triangular ribs of apex angle α equal at 60 °, and in that the angle γ is zero, the triangular ribs not being inclined.

Diagram 5a shows the great interest of a groove tube (1) according to the invention. Moreover, in a large part of the range of the Reynolds number, the pressure drop of such a tube A is less than that of the corresponding tube B.

This tube was used to form a battery by expansion of the tube in fins, as shown schematically in Figures 2a and 2b.

After expansion, a cross section was made according to Figures 4a and 4b. It has been observed that: - the height H has decreased by about 13%

- the width of the grooves has increased by about 16%

the angle δ has become zero.

As can be seen by comparing Figures 3a to 3b and 4a to 4b, the ribs became a little more "squat" after expansion of the tube, but they have retained their general shape and their inclination γ has been little changed.

The performance measurements performed on these tubes showed a very slight decrease in the performances measured on tubes before expansion.

Similar groove tubes (1) with oblique ribs of different heights have also been manufactured, as shown in Fig. 11, with H 2 = 0.85. Hl.

Similar grooved tubes (1) having straight ribs (2 ") have also been made, as shown in FIG. 11c, with any straight rib (2") interposed between two oblique ribs (2).

In this case, a groove tube (1) with 80 uniformly spaced ribs has been manufactured: 40 being oblique ribs (2) and 40 being straight ribs (2 "). ADVANTAGES OF THE INVENTION

The invention has great advantages.

Indeed, it allows on the one hand to have heat exchanger tubes of high efficiency with regard to heat exchange with a very high exchange coefficient Hi, and this while maintaining a relatively low loss.

Moreover, these tubes have a high resistance to deformation following the expansion of the tube to form batteries, and especially retain high performance after expansion. Indeed, the tubes according to the invention are suitable both for the manufacture of finned exchangers, as illustrated in Figure 2b, and for tabular exchangers, as shown in Figure 2c.

Finally, these tabes could be manufactured by grooving tabès smooth, high speed as in the case of the manufacture of tabès grooves classic.

LIST OF FIGURES

Groove pipe 1

Expanded Tube Non-Grooved Tube 1 "

Axial direction 10

Radial direction 11

Oblique rib 2

Tetragonal rib 2 'Right rib 2 "

Base B 20

Top side S 21

Lateral side CL ₁ 22

Side side CL ₂ 23 Middle right 24

Groove 3

Groove bottom 30

Battery 4 Ailette 5

Expansion medium - ball 6

Grooving device 7

Grooving chuck 70 Branches of 70,700

Radial compression means .... 71

Rotary cage 710

Rotating elements, balls ... 711,71 V

Means of traction of 1 72 Floating chuck 73

Holding die 74

Claims

1. Metal tube (1) groove, of thickness T _f at the bottom of the groove, of external diameter De, typically intended for the manufacture of heat exchangers or batteries (4) using a coolant or heat transfer fluid of monophasic or diphasic type said tube (1) being internally grooved by N helical ribs, with N ranging from 20 to 80 depending on the outer diameter De, of apex angle α, of height H in a radial direction (11) of said tube, of base B of width L _N and of helix angle β, two consecutive ribs being separated by a groove (3) with bottom (30) typically flat of width L _R , with a pitch P equal L _R + L _N , characterized in that: a) the said widths L _N and L _R are such that L _N / L _R is between 0.40 and 0.80, b) the said N ribs have a half-height width L _{NI /} 2 at least equal to at 2.L _N / 3 c) said N ribs are oblique ribs (2), inclined, typically in the same direction, by an angle γ p with respect to said radial direction (11) from 10 ° to 35 °, said angle γ being the angle formed between said radial direction (11) and a median line (24) passing through the middle of said base B (20) of said rib (2) and by the middle of the width of the rib (2) taken at its mid-height H / 2, and wherein said rib (2) is a rib (2 ') which has a tetragonal section comprising , in addition to its base B (20), an upper side S (21) facing said base B (20), and two lateral sides CL ₁ (22) and CL ₂ (23) forming between them said apex angle α , one CL ₁ (22) makes an angle B ₁ less than 90 ° with said adjacent groove bottom (30), and the other CL ₂ (23) makes an angle G ₂ typically greater than

90 ° with said groove bottom (30) adjacent, so as to have a high resistance to crushing, high heat exchange capacity and low pressure drop, when said tube is secured to cooling fins in a drums.

2. Metal tube according to claim 1 wherein said lateral side CL ₂ makes an angle θ ₂ greater than 90 ° with said groove bottom (30) adjacent.

3. Metal tube according to any one of claims 1 to 2 wherein said rib (2) has a width at half height L _{Nî / 2} at least equal to 0.70.L _N.

4. Metal tube according to claim 3 wherein said rib (2) has a mid-height width L _N I _{/ 2} at least equal to _N 0,75.L.

5. Metal tube according to any one of claims 1 to 4 wherein said apex angle α formed by said two lateral sides CL ₁ (22) and CL ₂ (23) ranges from 10 ° to

35 °.

6. Metal tube according to any one of claims 1 to 5 wherein said upper side S (21) has a width at least equal to 0.3.L _N , and reference at least 0.4.L _N.

7. Tube according to any one of claims 1 to 6 wherein said upper side S (21) is inclined relative to said base B (20) with an angle δ ranging from 5 ° to 35 °.

8. The tube of claim 7 wherein said angle δ has its apex closer to the lateral side CL ₂ (23) than the CL side ₁ (22).

9. Tube according to any one of claims 1 to 8 wherein said ribs (2, T) are of height H such that H / De is equal to 0.020 ± 0.005, H and De being expressed in mm.

10. Tube according to any one of claims 1 to 9 wherein the number N of ribs (2, T) is such that N / De is equal to 4.5 + 0.5, the corresponding pitch P being equal to π.Di / N, with Di equal to De-2.Tf, and De being expressed in mm.

11. Tube according to any one of claims 1 to 10 wherein said helix angle β ranges from 5 ° to 25 °.

12. Tube according to any one of claims 1 to 11, the thickness T _f is such that T _f / De is equal to 0.03 ± 0.005, T _f and De being expressed in mm, with De ranging from 6 mm to 18 mm

13. Tube according to any one of claims 1 to 12 wherein the P / H ratio ranges from 1.5 to 3 and preferably from 1.7 to 2.3.

14. Tube according to any one of claims 1 to 13 wherein said lateral sides CL ₁ (22) and CL ₂ (23) are connected to said adjacent groove bottoms (30) with radii of curvature R typically less than 100 microns, and typically less than 50 microns.

15. Tube according to any one of claims 1 to 14 wherein said ribs (2, T) form a succession of ribs of height H1 = H and height H2 = a.Hl, with a between 0.1 and 0.9 , the rib of height Hl being the main rib, and the rib of height H2 being the secondary rib, these two ribs being separated by a flat bottom groove.

16. Tube according to any one of claims 1 to 15 wherein a straight rib (2 ") is interposed between two adjacent oblique ribs (2, T), said straight rib having a height H ¹ <H or less than Hl.

17. Tube according to any one of claims 1 to 16 wherein said rib (2) and said groove (3) have substantially the shape of parallelograms, the ratio of the surfaces S _N / S _R being substantially equal to the ratio L _N / L _R , S _N and S _R respectively designating the surface of said rib (2) and said groove (3).

18. Tube according to any one of claims 1 to 17 in Cu and alloys of Cu, Al and alloys of Al, Fe and Fe alloys.

19. Tube according to any one of claims 1 to 18 of typically round cross section, oval or rectangular.

20. Heat exchanger or battery (4) using fins (5) and expanded tubes (I ¹ ) formed by expanding tubes (1) according to any one of claims 1 to 19.

21. A method of manufacturing grooved tubes according to any one of claims 1 to 19 wherein a non-grooved tube (1 ") is radially compressed on a grooving mandrel (70) provided on its peripheral surface with a plurality of grooves (700). ), by means of a radial compression means (71), so as to form a groove tube (1) having a plurality of ribs (2) on its inner surface, said groove tube thus formed (1) being pulled by a traction means (72) in a so-called axial direction (10) of displacement of said groove tube (1), said radial compression means (71) and said grooving mandrel (70) remaining fixed with respect to said direction axial (10), said grooving mandrel (70) being a mandrel placed inside said non-grooved tube (1 ") and integral with a floating mandrel (73) retained upstream of the grooving mandrel (70) by a holding die (74), said radial compression means (71) comprising a rotary cage (710) having a plurality of members (711), typically a plurality of balls (711 '), rotating about said non-grooved tube (1 ") to the right of said grooving mandrel (70) in a direction of predetermined rotation with respect to said axial direction (10), characterized in that: a) said grooves (700) of said plurality of grooves are helical grooves, of right or left pitch, so as to obtain a groove tube (1) β ≠ 0, b) said grooves (700) of said plurality of grooves are inclined grooves, with a right or left inclination, so as to obtain a groove tube (1) whose ribs (2). have an angle of inclination γ, c) one chooses said direction of rotation of said rotary cage (710), said direction being direct or inverse, depending in particular on said right or left inclination of said grooves (700), so as to form said plurality of ribs (2) of said groove tubes (1) in their integrally, said right or left pitch of said grooving mandrel (70), said right or left inclination of said grooves (700) and said direct or inverse direction of rotation of said rotary cage (710) being determined relative to an observer placed at the rear and above said grooving mandrel (70) and looking in said axial direction (10) of said scroll tube (1), said direct direction of rotation being that of the clockwise.

22. The method of claim 21 wherein, when said direction of rotation of said rotary cage (710) is direct, said helical grooves (700) of said mandrel. grooving means (70) have a left inclination, said pitch of said grooving mandrel (70) being right or left.

23. The method of claim 21 wherein, when said direction of rotation of said rotary cage (710) is opposite, said helical grooves (700) of said grooving mandrel (70) have a right inclination, said pitch being right or left.

24. A method of manufacturing grooved tubes according to any one of claims 1 to 19, typically non-corrugated, obtained by flat grooving of a metal strip and forming a welded tube.