EP1949012B1 - Grooved tubes for heat exchangers with better resistance to expansion - Google Patents

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 a, of height H in a radial direction (11) of the said tube, and of base B of width LN and of helix angle ß, 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

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.

• un rapport H/Di compris entre 0,02 et 0,03, H désignant la profondeur des rainures (ou la hauteur des nervures), et Di le diamètre intérieur du tube rainuré,
• un angle d'hélice β par rapport à l'axe de tube compris entre 7 et 30°,
• un rapport S/H compris entre 0,15 et 0,40, avec S désignant la section transversale de la rainure,
• un angle d'apex α des nervures compris entre 30 et 60°.

By way of example, mention may be made of the patent application EP-A2-0 148 609 which describes triangular or trapezoidal groove tubes 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 demand no. 57-58088 discloses V-groove 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 demand JP 54-125563 discloses sloping U-shaped or V-grooved tubes, with H ranging from 0.002 to 0.2 mm, a pitch P ranging from 0.1 to 0.5 mm and an angle β ranging from 4 to 15 °.

Japanese demand 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 °.
The patent U.S. 4,044,797 describes grooved tubes in V or U adjacent to the preceding tubes.

Japanese utility model no. 55-180186 describes tubes with 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.

Licences U.S. Patent No. 4,545,428 and no 4480684 describe tubes with V-grooves and triangular ribs, with the height H between 0.1 and 0.6 mm, a pitch P between 0.2 and 0.6 mm, an apex angle α of 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 average width 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 °.

Japanese demand is known JP 2001-074384 describing tubes with inclined ribs.

We also know the European patent EP 1 061 318 describing angled triangular ribbed tubes adapted 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 flat-bottomed grooves and with ribs of different height H, with a helix angle β of between 5 and 50 °, with an apex angle α of between 30.degree. and 60 °, to obtain better performance after crimping the tubes and mounting in the exchangers.

• d'une part, les caractéristiques relatives au transfert de chaleur (coefficient d'échange thermique), domaine dans lequel les tubes rainurés sont très supérieurs aux tubes non rainurés, de sorte qu'à échange thermique équivalent, la longueur de tube rainurée nécessaire sera moindre que celle de tube non rainuré,
• d'autre part, les caractéristiques relatives aux pertes de charge, de faibles pertes de charges permettant d'utiliser des pompes ou compresseurs de plus faible puissance, encombrement et coût,
• en outre, la faisabilité industrielle des tubes et la vitesse de production qui conditionne le prix de revient du tube chez le fabricant de tubes,
• enfin, les caractéristiques relatives aux propriétés mécaniques des tubes, typiquement en relation avec la nature des alliages utilisés ou avec l'épaisseur moyenne des tubes, épaisseur qui conditionne le poids du tube par unité de longueur, et donc influe sur son prix de revient.

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 higher than the non-grooved tubes, so that equivalent heat exchange, the length of grooved tube necessary will be less than that of ungrooved tube,
• on the other hand, the characteristics relating to pressure drop, 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 great number and a great diversity of teachings with regard to 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 tubular exchangers.

However, 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 tubular heat 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 tubes, for applications or domains that use monophasic or biphasic fluids, and that can be manufactured with productivity and equipment as in the case of grooved tubes already industrialized.

DESCRIPTION OF THE INVENTION

1. a) lesdites largeurs L_N et L_R sont telles que L_N / L_R soit compris entre 0,40 et 0,80,
2. b) lesdites N nervures présentent une largeur à mi-hauteur L_N1/2 au moins égale à 2.L_N/3
3. c) lesdites N nervures sont des nervures obliques, inclinées, typiquement dans un même sens, d'un angle γ par rapport à ladite direction radiale allant de 10° à 35°, ledit angle γ étant l'angle formé entre ladite direction radiale et une droite médiane passant par le milieu de ladite base B de ladite nervure et par le milieu de la largeur de la nervure prise à sa mi-hauteur H/2,

et dans ce tube, ladite nervure est une nervure qui présente une section tétragonale comprenant, outre sa base B, un côté sommital S en regard de ladite base B, et deux côtés latéraux CL₁ et CL₂ formant entre eux ledit angle d'apex α, dont l'un CL₁ (22) fait un angle θ₁ inférieur à 90° avec ledit fond de rainure (30) adjacent, et dont l'autre CL₂ (23) fait un angle θ₂ typiquement supérieur à 90° avec ledit fond de rainure (30) adjacent, ledit angle d'apex α allant de 10 à 35°,
de manière à présenter une résistance élevée à l'écrasement, des capacités d'échange thermique élevées et une faible perte de charge, quand ledit tube est solidarisé à des ailettes de refroidissement dans une batterie.According to the invention, the grooved metal tube, of thickness T _f at the bottom of the groove, of outer diameter De, typically intended for the manufacture of heat exchangers or batteries using a coolant or heat transfer fluid of monophasic or diphasic type, said tube being grooved internally by N helical ribs, with N ranging from 20 to 80 according to the outside diameter De, apex angle α, height H in a radial direction of said tube, base B of width L _N and of helix angle β, two consecutive ribs being separated by a generally flat bottom groove L _R , with a pitch P equal L _R + L _N , is characterized in that :

1. a) said widths L _N and L _R are such that L _N / L _R is between 0.40 and 0.80,
2. b) said N ribs have a width at half height L _{N1 / 2} at least equal to 2.L _N / 3
3. c) said N ribs are oblique ribs, inclined, typically in the same direction, by an angle γ with respect to 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 half-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 forming between them said apex angle α, one CL ₁ (22) makes an angle θ ₁ less than 90 ° with said groove bottom (30) adjacent, and the other CL ₂ (23) makes an angle θ ₂ typically greater than 90 ° with said adjacent groove bottom (30), said apex angle α ranging from 10 to 35 °,
so as to have a high crush resistance, high heat exchange capacity 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 θ ₁ less than 90 ° with said groove bottom (30) adjacent. These ribs are typically identical to each other.

• d'une part, après expansion, même dans les conditions les plus sévères, les nervures de ces tubes passent d'une hauteur H à une hauteur H' telle que H'/H est au moins égal à 0,85, alors qu'avec les tubes traditionnels, ce rapport est inférieur à 0,85.
• d'autre part, comme cela apparaîtra avec les exemples, les performances présentent des capacités d'échange thermique élevées, et cela avec une perte de charge typiquement moindre.
• enfin, en ce qui concerne la fabrication de ces tubes, elle peut être réalisée par rainurage de tubes non rainurés, ce qui est avantageux en pratique, et cela, avec une productivité et un équipement et une cadence analogues à ceux des procédés de fabrication des tubes rainurés traditionnels déjà industrialisés.

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 '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 capacities, 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 of traditional grooved tubes already industrialized.

DESCRIPTION OF THE FIGURES

FIG. 1a schematically represents a grooved 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).
The figure 1b is a partial section of the grooved tube (1) in a transverse plane perpendicular to said axial direction (10).

The figure 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).
The figure 2b is a perspective view of a battery (4) formed by crimping a plurality of tubes (1) in a plurality of fins (5) oriented perpendicularly to the axial direction (10) of the tubes (1).

The Figure 2c is a sectional view of a tubular heat exchanger in which the tubes (1) forming a bundle do not have to be expanded as in the case of the battery (4) of the figure 2b .

The Figures 3a to 4b are partial sections of tubes, in section along a transverse plane perpendicular to said axial direction (10).
The Figures 3a and 3b relate to tubes (1) before expansion. These figures according to identical, and are distinguished in that the figure 3b carries measurement values for certain parameters.

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

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

The figure 5a gives on the ordinate the exchange coefficient Hi (Wm ² .K) as a function of the Reynolds number Re on the abscissa.
The figure 5b gives the ordinate the pressure drop (Pa / m) as a function of the Reynolds number Re on the abscissa.

The figure 6a is an axial section illustrating a device for grooving (7) tubes.
The Figures 6b and 6c are relative 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.
The figure 6b is a composite view comprising 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).

The Figure 6c is a top view, an oblique arrow pointing to the left indicating the inclination to the left of the grooves, another axial arrow indicating the direction of movement of the tube relative to the mandrel (70).

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

In this figure, said grooving mandrel (70) is that of Figures 6b and 6c , its cross-section being that represented on the lower part of the figure 6b , and the direction of rotation of the rotary cage (710) is the forward direction, in the clockwise direction, the observer looking in the axial direction (10) corresponding to the direction towards which said tube (1) is pulled.
Under these conditions, the grooved tube (1) has a plurality of ribs (2) having no defect.

The Figures 8a and 8b are analogous to the Figures 6c and 7 .
The figure 8a represents a grooving mandrel (70) which differs from that of the Figure 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.
The figure 8b is analogous to the figure 7 and differs therefrom in that the grooving mandrel (70), which is that of the figure 8a , has grooves (700) inclined to the right, instead of being inclined to the left, the direction of rotation of the rotary cage (710) being the forward direction.

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

The Figures 9a and 9b are similar to Figures 8a and 8b .
The figure 9a represents a grooving mandrel (70) identical to that of the Figure 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.

The figure 9b is analogous to the figure 8b and differs therefrom in that the grooving mandrel (70), which is that of the figure 9a , has grooves (700) inclined to the left, instead of being inclined to the right and in that the direction of rotation of the rotary cage (710) is the opposite direction.

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

The Figures 10a and 10b are analogous to the Figures 8a and 8b .
The figure 10a represents a grooving mandrel (70) identical to that of the figure 8a , an oblique arrow pointing to the right indicating the inclination to the right of the grooves.
The figure 10b is analogous to the figure 8b and is distinguished in that the direction of rotation of the rotary cage (710) is reversed instead of being direct.

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

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

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

The figure 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.

The figure 11c , analogous to the 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 modality of the invention illustrated on the figures 1b and 3a to 3b said rib (2) may be a rib (2 ') having 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 of which CL ₁ (22) makes an angle θ ₁ less than 90 ° with said adjacent groove bottom (30), and wherein 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 half-height width L _{N1 / 2} at least equal to _N 0,65.L.
Typically, said rib (2) may have a width at half height L _{N1 / 2} at least equal to 0.70.L _N.

Preferably, said rib (2) may have a half-height width L _{N1 / 2} at least equal to _N 0,75.L.
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 °.
On the figure 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 illustrated also on figures 1b and 3a to 3b said upper side S (21) may have a width of at least 0.3.L _N , and a reference of at least 0.4.L _N.

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, 2 ') 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 may 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 from 1.7 to 2.3.

As illustrated on 1a figure 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 typically less than 100 microns, and typically less than 50 microns.

As illustrated on the figure 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 H1 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 on the figure 11c a straight rib (2 ") may be interposed between two adjacent oblique ribs (2Comm, 2 '), said right rib having a height H'<H or less than H1.

Generally, said rib (2) and said groove (3) may 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 denoting the surface respectively said rib (2) and said groove (3).

As it appears by comparing the Figures 3a to 3b with the Figures 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 tube performance before and after expansion of the tube.

According to the invention, the tubes (1) can be Cu and Cu alloys, Al and Al alloys, 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 (1 ') formed by expanding tubes (1) according to the invention.

1. a) lesdites rainures (700) de ladite pluralité de rainures sont des rainures hélicoïdales, de pas droit ou gauche, de manière à obtenir un tube rainuré (1) d'angle d'hélice β ≠ 0,
2. b) lesdites rainures (700) de ladite pluralité de rainures sont des rainures inclinées, avec une inclinaison droite ou gauche, de manière à obtenir un tube rainuré (1) dont les nervures (2) présentent un angle d'inclinaison γ > 0°,
3. c) on choisit ledit sens de rotation de ladite cage rotative (710), ledit sens étant direct ou inverse, en fonction notamment dé ladite inclinaison droite ou gauche desdites rainures (700), de manière à former ladite pluralité de nervures (2) desdits tubes rainurés (1) dans leur intégralité, ledit pas droit ou gauche dudit mandrin de rainurage (70), ladite inclinaison droite ou gauche desdites rainures (700) et ledit sens de rotation direct ou inverse de ladite cage rotative (710) étant déterminés relativement à un observateur placé à l'arrière et au-dessus dudit mandrin de rainurage (70) et regardant dans ladite direction axiale (10) de défilement dudit tube rainuré (1), ledit sens de rotation direct étant celui des aiguilles d'une montre.
   Ce procédé utilise un dispositif de rainurage, par exemple un dispositif de rainurage tel que décrit dans le brevet français n° 2 707 534 au nom de la demanderesse, la figure 6a qui schématise ce procédé correspondant à la figure 2a de ce brevet.

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 grooved tube (1) having a plurality of ribs (2) on its inner surface, said grooved tube thus formed (1 ) being pulled by a traction means (72) in a so-called axial direction (10) of movement of said grooved 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 rotational cage ative (710) having a plurality of members (711), typically a plurality of balls (711 '), rotating about said non-grooved tube (1 ") in line with said groove tread (70) in one direction predetermined rotation with respect to said axial direction (10), characterized in that :

1. a) said grooves (700) of said plurality of grooves are helical grooves, of right or left pitch, so as to obtain a grooved tube (1) of helix angle β ≠ 0,
2. b) said grooves (700) of said plurality of grooves are inclined grooves, with a right or left inclination, so as to obtain a grooved tube (1) whose ribs (2) have an inclination angle γ> 0 ° ,
3. c) selecting said direction of rotation of said rotary cage (710), said direction being direct or inverse, in particular according to said right or left inclination of said grooves (700), so as to form said plurality of ribs (2) of said grooved tubes (1) in their entirety, 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 relatively an observer placed at the rear and above said grooving mandrel (70) and looking in said axial direction (10) of said slotted 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 on behalf of the plaintiff, the figure 6a which schematizes this process corresponding to the figure 2a of this patent.

1. a) lorsque ledit sens de rotation de ladite cage rotative (710) est direct, lesdites rainures hélicoïdales (700) dudit mandrin de rainurage (70) présentent une inclinaison gauche, ledit pas dudit mandrin de rainurage (70) étant droit ou gauche, comme illustré sur les figures 6b à 7,
2. b) lorsque ledit sens de rotation de ladite cage rotative (710) est inverse, lesdites rainures hélicoïdales (700) dudit mandrin de rainurage (70) présentent une inclinaison droite, ledit pas étant droit ou gauche, comme illustré sur les figures 10a et 10b.
   Lorsque ces conditions ne sont pas respectées, la demanderesse a observé que les rainures (700) se remplissaient mal ou de manière incomplète, de sorte que les nervures (2) correspondantes du tube rainuré (1) étaient défectueuses.

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:

1. 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 on the Figures 6b to 7 ,
2. b) when said direction of rotation of said rotary cage (710) is reversed, said helical grooves (700) of said grooving mandrel (70) have a right inclination, said pitch being right or left, as illustrated in Figures 10a and 10b .
   When these conditions are not met, the Applicant has observed that the grooves (700) were filling incorrectly or incompletely, so that the ribs (2) corresponding to the grooved 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 copper tube (1) was manufactured as shown in figures 1b and 3a to 3b , by grooving a smooth tube, using the method according to the invention, using the grooving device illustrated on the Figures 6a to 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 manufactured using the grooving device illustrated in FIGS. Figures 10a and 10b using a grooving mandrel (70) having a plurality of grooves (700) inclined to the right, and rotating the rotary cage (710) in the opposite direction.

Tests conducted, according to the 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.

• l'angle d'apex α vaut 22°
• l'angle d'hélice β vaut 20°.
• l'angle γ vaut 15°. Cet angle est formé entre ladite direction radiale (11) et la droite médiane (24) passant par le milieu de ladite base B (20) de ladite nervure (2) et par le milieu de la largeur de la nervure (2) prise à sa mi-hauteur H/2.
• l'angle δ vaut environ 18°.

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 _{N1 / 2} equal to 0.77.L _N.
Regarding the angles:

• the angle of apex α is 22 °
• the helix angle β is 20 °.
• the angle γ is 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 about 18 °.

A cross-section of this tube (1) was made as shown in FIG. Figure 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 were represented on the Figures 5a and 5b .
The tube A is the tube (1) according to the invention.

The tube B is a tube similar 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 to 60 °, and in that the angle γ is zero, the triangular ribs not being inclined.

Diagram 5a shows the great interest of a grooved 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 expanding the tube in fins, as shown schematically on the Figures 2a and 2b .

• la hauteur H a diminué d'environ 13 %
• la largeur des rainures a augmenté d'environ 16%
• l'angle δ est devenu nul.
  Comme on peut le voir en comparant les figures 3a à 3b et 4a à 4b, les nervures sont devenues un peu plus "trapues" après expansion du tube, mais elles ont conservé leur forme générale et leur inclinaison γ a été peu modifiée.
  Les mesures de performances effectuées sur ces tubes ont montré une très faible diminution des performances mesurées sur tubes avant expansion.

After expansion, a cross-section was made according to the Figures 4a and 4B.
It has been observed that:

• H height 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 the Figures 3a to 3b and 4a to 4b , the ribs became a little more "squat" after expansion of the tube, but they retained their general shape and their inclination γ was little changed.
  The performance measurements performed on these tubes showed a very slight decrease in the performances measured on tubes before expansion.

Similar grooved tubes (1) with oblique ribs of different heights have also been manufactured, as shown in FIG. figure 11 with H2 = 0.85. H1.

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

In this case, a grooved tube (1) with 80 evenly 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 FIG. figure 2b , and for tubular heat exchangers, as illustrated on the Figure 2c .

Finally, these tubes could be manufactured by grooving smooth tubes, at high speed as in the case of the manufacture of conventional grooved tubes.

LIST OF FIGURES

Grooved tube 1 Expanded tube 1 ' Non grooved tube 1 " Axial direction 10 Radial direction 11 Oblique rib 2 Tibial tetragonal rib 2 ' Right rib 2 " Base B 20 Summit side S 21 Side side CL ₁ 22 Side side CL ₂ 23 Right median 24 Groove 3 Groove bottom 30 Drums 4 Fin 5 Means of expansion - ball 6 Grooving device 7 Grooving chuck 70 Grooves of 70 700 Radial compression means 71 Rotary cage 710 Rotating elements, balls 711.711 ' Means of traction of 1 72 Floating chuck 73 Holding die 74

Claims (23)

1. Grooved metal tube (1), of thickness T_f at the bottom of a groove, of external diameter De, typically intended for the manufacture of heat exchangers or batteries (4) using a cooling or heating fluid of the single-phase or two-phase type, said tube (1) being grooved interiorly by N helicoidal ribs, with N ranging from 20 to 80 according to the external diameter De, of apex angle α, of height H according to 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 a bottom (30) that is typically flat of width L_R with a pitch P equal to L_R + L_N, characterised in that:

   a) said widths L_N and L_R as such that L_N / L_R is between 0.40 and 0.80,

   b) said N ribs having a width at mid-height L_NI/2 at least equal to 2.L_N/3

   c) said N ribs are slanted ribs (2), inclined, typically in the same direction, of an angle γ in relation to said radial direction (11) ranging from 10° to 35°, said angle γ being the angle formed between said radial direction (11) and a median straight line (24) passing through the middle of said base B (20) of said rib (2) and through 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') that has a tetragonal section comprising, other than its base B (20), an apical side S (21) across from said base B (20), and two lateral sides CL₁ (22) and CL₂ (23) forming between them said apex angle α, of which one CL₁ (22) forms an angle θ1 less than 90° with said adjacent groove bottom (30), and of which the other CL₂ (23) forms an angle θ2 typically greater than 90° with said adjacent groove bottom (30), said apex angle ranging from 10° to 35°,
   in such a way as to have a high resistance to crushing, high heat exchange capacities and a low loss of load, when said tube is integral with cooling vanes in a battery.
2. Metal tube according to claim 1 wherein said lateral side CL₂ forms an angle θ2 greater than 90° with said adjacent groove bottom (30).
3. Metal tube according to any of claims 1 to 2 wherein said rib (2) has a width at mid-height L_NI/2 at least equal to 0.70.LN.
4. Metal tube according to claim 3 wherein said rib (2) has a width at mid-height L_NI/2 at least equal to 0.75.L_N.
5. Metal tube according to any of claims 1 to 4 wherein said apical side S (21) has a width at least equal to 0.3.L_N, and preferably at least equal to 0.4.L_N.
6. Tube according to any of claims 1 to 5 wherein said apical side S (21) is inclined in relation to said base B (20) with an angle δ ranging from 5° to 35°.
7. Tube according to claim 6 wherein said angle δ has its apical closer to the lateral side CL₂ (23) than to the side CL₁ (22).
8. Tube according to any of claims 1 to 7 wherein said ribs (2, 2') are of height H such that H/De is equal to 0,020 ± 0,005, H and De being expressed in mm.
9. Tube according to any of claims 1 to 8 wherein the number N of ribs (2, 2') is such that N/De is equal to 4.5 ± 0.5, the corresponding pitch P being equal to n.Di/N, with Di equal to De-2.Tf, and De being expressed in mm.
10. Tube according to any of claims 1 to 9 wherein said helix angle β ranges from 5° to 25°.
11. Tube according to any of claims 1 to 10 of which 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.
12. Tube according to any of claims 1 to 11 wherein the ratio P/H ranges from 1.5 to 3 and preferably from 1.7 to 2.3.
13. Tube according to any of claims 1 to 12 wherein said lateral sides CL₁ (22) and CL₂ (23) connect with said adjacent groove bottoms (30) with radiuses of curvature R typically less than 100 µm, and typically less than 50 µm.
14. Tube according to any of claims 1 to 13 wherein said ribs (2, 2') 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 H1 being the main rib, and the rib of height H2 being the secondary rib, these two ribs being separated by a flat-bottomed groove.
15. Tube according to any of claims 1 to 14 wherein a straight rib (2") is inserted between two adjacent slanted ribs (2, 2'), said straight rib having a height H' < H or less than H1.
16. Tube according to any of claims 1 to 15 wherein said rib (2) and said groove (3) substantially have the form of parallelograms, the ratio of areas S_N / S_R being substantially equal to the ratio L_N/L_R, S_N and S_R respectively designating the area of said rib (2) and of said groove (3).
17. Tube according to any of claims 1 to 16 made of Cu and Cu alloys, Al and Al alloys, Fe and Fe alloys.
18. Tube according to any of claims 1 to 17 of transversal section that is typically round, oval or rectangular.
19. Heat exchanger or battery (4) using vanes (5) and expanded tubes (1') formed by expansion of tubes (1) according to any of claims 1 to 18.
20. Method of manufacturing grooved tubes according to any of claims 1 to 18 wherein a non-grooved tube (1'') is compressed radially on a grooved mandrel (70) provided on its peripheral surface with a plurality of grooves (700), using a means of radial compression (71), in such a way as to form a grooved tube (1) provided with a plurality of ribs (2) on its interior surface, said grooved tube formed as such (1) being drawn by a means of traction (72) according to a so-called axial direction (10) of displacement of said grooved tube (1), said means of radial compression (71) and said grooved mandrel (70) remaining fixed in relation to said axial direction (10), said grooved mandrel (70) being a mandrel placed inside of said non-grooved tube (1") and integral with a floating mandrel (73) retained upstream of the grooved mandrel (70) by a holding die (74), said means of radial compression (71) comprising a rotating cage(710) provided with a plurality of elements (711), typically of a plurality of balls (711'), rotating around said non-grooved tube (1'') to the right of said grooved mandrel (70) according to a predetermined direction of rotation in relation to said axial direction (10), characterised in that:

    a) said grooves (700) of said plurality of grooves are helicoidal grooves, of right or left pitch, in such a way as to obtain a grooved tube (1) of helix angle β ≠ 0,

    b) said grooves (700) of said plurality of grooves are inclined grooves, with a right or left inclination, in such a way as to obtain a grooved tube (1) of which the ribs (2) have an angle of inclination γ,

    c) said direction of rotation of said rotating cage (710), said direction being direct or inverse, is chosen according in particular to said right or left inclination of said grooves (700), in such a way as to form said plurality of ribs (2) of said grooved tubes (1) in their entirety, said right or left pitch of said grooved mandrel (70), said right or left inclination of said grooves (700) and said direct or inverse direction of rotation of said rotating cage (710) being determined relative to an observer located to the rear and above said grooved mandrel (70) and observing in said axial direction (10) of travel of said grooved tube (1), said direct direction of rotation being clockwise.
21. Method according to claim 20 wherein, when said direction of rotation of said rotating cage (710) is direct, said helicoidal grooves (700) of said grooved mandrel (70) having a left inclination, said pitch of said grooved mandrel (70) being right or left.
22. Method according to claim 20 wherein, when said direction of rotation of said rotating cage (710) is inverse, said helicoidal grooves (700) of said grooved mandrel (70) have a right inclination, said pitch being right or left.
23. Method for manufacturing grooved tubes according to any of claims 1 to 18, typically not ribbed, obtained by flat grooving of a metal strip then formation of a welded tube.

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