EP1851498B1 - Slotted tube with reversible usage for heat exchangers - Google Patents

Description

FIELD OF THE INVENTION

The invention relates to the field of tubes for heat exchangers, and more particularly the field of heat exchangers operating in evaporation / condensation and in reversible mode. The invention relates to the use of heat exchangers defined in claim 1.

STATE OF THE ART

• a) De= 9,52nm; b) N= 60;
• c) H= 0,2 mm;
• d) 30°<d<60°;
• e) β= 18°;
• f) le facteur de cavallini est égal a 3.15.

The document EP 0148609 , considered as representing the state of the art closest to the object of claim 1, discloses the use of a heat exchanger in condensation or invaporation mode (without being reversible), said exchanger comprising metal grooved tubes , of thickness Tp at the bottom of groove, of outside diameter De, said tubes being grooved internally by N helical grooves of apex angle (α), of height H, of basic width L _N and of angle d β helix, two consecutive ribs being separated by a groove typically flat bottom of width L _R , with a pitch equal to L _R + L _N , where:

• a) De = 9.52nm; (b) N = 60;
• c) H = 0.2 mm;
• d) 30 ° <d <60 °;
• e) β = 18 °;
• f) the cavallini factor is equal to 3.15.

In addition, there is a large number of documents 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°.

Ces caractéristiques de tube sont adaptées à des fluides à transition de phase, les performances des tubes étant analysées de manière distincte lors de l'évaporation du fluide et lors de la condensation du fluide.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-grooved tubes, with H between 0.02 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 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 °.

Finally, the European patent EP-B1-701 680 , in the name of the applicant, describes grooved tubes, with grooves typically flat bottom and with ribs of different height H, helix angle β between 5 and 50 °, apex angle α between 30 and 60 °, to obtain better performances after the crimping of the tubes and assembly 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 rainuré nécessaire sera moindre que celle de tube non rainuré,
• d'autre part, les caractéristiques relatives aux pertes de charge, de faibles pertes de charge permettant d'utiliser des pompes ou compresseurs de plus faible puissance, encombrement et coût,
• en outre, 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.
• enfin, la faisabilité industrielle des tubes et la vitesse de production qui conditionne le prix de revient du tube chez le fabricant de tubes.

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.), must satisfy four requirements for:

• 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 drops, low pressure drops allowing the use of pumps or compressors of lower power, size and cost,
• in addition, 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 thus influences its cost price .
• finally, the industrial feasibility of the tubes and the speed of production which conditions the cost price of the tube at the tube manufacturer.

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 reduction of pressure loss.
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.
Finally, these teachings concern, where specified, exchanges with refrigerant fluid which typically evaporates or condenses in the refrigerant circuit, the fluid having a different behavior in evaporation and condensation. So far, these teachings relate to grooved tubes for exchangers operating either in condensation or in evaporation.

Ultimately, a person skilled in the art already has many difficulties in drawing the quintessence of the state of the art, from so many, sometimes contradictory data.
On the other hand, a person skilled in the art knows that a typical commercial tube with triangular ribs as shown in FIG. figure 1 typically has the following characteristics: outer diameter De = 12 mm, rib height H = 0.25 mm, tube wall thickness Tf = 0.35 mm, number of ribs N = 65, helix angle β = 15 ° Apex angle α = 55 °.

In order to meet a market demand, the object of the present invention relates to the use of tubes for reversible heat exchangers, that is to say a use where tubes or exchangers are used with refrigerants with change of applications. phase, sometimes in evaporation, sometimes in condensation, that is to say either to cool, for example as air conditioners, or to heat, for example as heating means, typically air or a secondary fluid.

More particularly, the present invention relates to the use of tubes which not only have an excellent compromise between thermal performance in evaporative and refrigerant condensation mode, but which, moreover, intrinsically have high performance as well. in evaporation only in condensation.

The applicant has therefore sought economic tubes and exchangers, with a relatively low weight per meter, and high heat exchange performance, both in evaporation and in condensation.

DESCRIPTION OF THE INVENTION

1. a) le diamètre extérieur De est compris entre 4 et 20 mm,
2. b) le nombre N de nervures va de 46 à 98, en fonction notamment du diamètre De,
3. c) la hauteur H des nervures va de 0,18 mm à 0,40 mm, en fonction notamment du diamètre De,
4. d) l'angle d'apex α tel que 20° ≤ α < 28°,
5. e) l'angle d'hélice β va de 18° à 35°, ledit tube présentant un facteur de Cavalini au moins égal à 3.5,

de manière à obtenir simultanément un coefficient d'échange thermique élevé à la fois en évaporation et en condensation, une faible perte de charge et un tube le plus léger possible et cela sans surcoût de fabrication par rapport aux tubes spécifiques à l'évaporation ou à la condensation.According to the invention, the grooved metal tubes, of thickness T _f at the bottom of the groove, with an outer diameter De, typically intended for the manufacture of heat exchangers operating in evaporation or in condensation or in reversible mode and using a refrigerant with phase change, grooved internally by N helical ribs of apex angle α, of height H, of base width L _N and of helix angle β, two consecutive ribs being separated by a groove with a flat bottom of width L _R , with a pitch P equal L _R + L _N , are such that,

1. a) the outer diameter De is between 4 and 20 mm,
2. b) the number N of ribs ranges from 46 to 98, in particular according to the diameter De,
3. c) the height H of the ribs ranges from 0.18 mm to 0.40 mm, depending in particular on the diameter De,
4. d) the apex angle α such that 20 ° ≤ α <28 °,
5. e) the helix angle β is from 18 ° to 35 °, said tube having a Cavalini factor of at least 3.5,

so as simultaneously to obtain a high heat exchange coefficient in both evaporation and condensation, a low pressure drop and a lightest possible tube and this without manufacturing cost over the specific tubes for evaporation or condensation. the condensation.

As a result of her research, the Applicant has successfully solved the problems posed by the combination of means and the preceding set of features.

The characteristic defined under a) defines the outer diameter range of tubes in the range of application targeted by the tubes according to the invention.

The characteristic under b), relative to the number N of grooves, and therefore to the corresponding pitch P, specifies that this number must be relatively high. The applicant's tests with finned batteries have shown that this number of grooves has a great influence on the heat performance of the exchangers.

• quand le nombre N est inférieur à 46, il a été observé que la performance de l'échangeur chutait considérablement.
• en ce qui concerne la limite supérieure du nombre N, elle est essentiellement d'ordre technologique et pratique, et dépend des possibilités technique de fabrication des tubes rainurés, cette limite supérieure varie donc, et augmente avec le diamètre De du tube.

Il a été observé sur un tube de 12 mm de diamètre De, qu'un nombre de nervures N de 98 assure une performance thermique élevée de l'échangeur en évaporation et en condensation.Thus, for example, for a tube diameter of 9.52 mm:

• when the number N is less than 46, it was observed that the performance of the exchanger fell considerably.
• as regards the upper limit of the number N, it is essentially of a technological and practical nature, and depends on the technical possibilities of manufacture of the grooved tubes, this upper limit therefore varies, and increases with the diameter De of the tube.

It has been observed on a tube 12 mm in diameter that a number of ribs N of 98 ensures a high thermal performance of the exchanger in evaporation and condensation.

• pour des valeurs de H supérieures à 0,40 mm, il a été noté une faisabilité technique moindre, car il n'est pas aisé de fabriquer des nervures de très grande hauteur, et il a été noté en outre une augmentation de la perte de charge,
• pour des valeurs de H inférieures à 0,20 mm, il a été noté que la performance d'échange thermique diminue trop et devient insuffisante.

Cette hauteur H peut varier avec le diamètre du tube, les tubes de plus grand diamètre ayant de préférence les nervures de plus grande hauteur.With regard to the characteristic under c), relative to the height H of the ribs or depth of the grooves, the limits of H result from the following observations:

• for values of H greater than 0.40 mm, a lower technical feasibility was noted, as it is not easy to make very high ribs, and there was also an increase in the loss of charge,
• for values of H less than 0.20 mm, it was noted that the heat exchange performance decreases too much and becomes insufficient.

This height H can vary with the diameter of the tube, the larger diameter tubes preferably having the ribs of greater height.

The characteristic under d), relative to the apex angle α, provides that this angle must be chosen in a relatively narrow range (20 ° - 28 °) and with relatively low α-apex angle values.
On the one hand, a low α-angle value is preferable for improving the heat transfer performance to decrease the pressure drop and to decrease the weight of the tube / m. It is with trapezoidal ribs that the angle α may be the weakest. However, the lower limit is essentially related to the manufacture of grooved tubes according to the invention to maintain a high rate of production.

The characteristic under e), relative to the helix angle β, shows that this angle must be at least equal to 18 ° to solve the problems of the invention, and at most equal to 35 ° to because of the significant increase in pressure losses, especially with certain refrigerants, for example R134a refrigerant.

Regarding the thickness Tf of the tube at the bottom of the groove, it may vary according to the diameter De, so as to have both sufficient mechanical properties, including resistance to internal pressure, a maximum saving in material, and therefore optimized material cost, and a weight per meter as low as possible. This thickness Tf is 0.28 mm for a 9.55 mm diameter tube De, and 0.35 mm for a tube 12.7 mm in diameter De.

All of these means make it possible to define a selection of tubes, specific tubes particularly adapted to exchangers with phase-change refrigerants, so as to simultaneously have a high heat exchange coefficient in evaporation and condensation, a small loss of charge and a tube as light as possible.

DESCRIPTION OF THE FIGURES

• The Figures 1a and 1b are intended to illustrate the meaning of the various parameters used to define the tubes used in the method according to the invention.
• The figure 1a is a partial view of a grooved tube (1), in partial section along the axis of the tube, so as to illustrate the helix angle β.
• The figure 1b represents a partial view of a grooved tube (1), in partial section perpendicular to the axis of the tube, so as to illustrate the case of a tube comprising a succession of ribs (2) of height H, substantially shaped ribs triangular, of width L _N at the base and apex angle α, separated by grooves (3) of substantially trapezoidal shape and width L _R , L _R being the distance between two grooves ribs. This tube has a thickness Tf, an outside diameter De, an inner diameter Di and a pitch P equal to L _R + L _N.
• The Figures 2a to 2c are partial sections of a tube 8 mm in diameter and 0.26 mm thick Tf, according to an exemplary embodiment of the invention, in which the ribs form an alternation of trapezoidal ribs of height H1 and height H2 <H1, at different scales.
• The figure 2a represents 3 complete ribs (2) and 2 partial ribs, spaced by grooves (3), and carries a "200 μm" scale.
• The figure 2b represents 2 complete ribs and carries a scale "100 μm".
• The Figure 2c represents 1 single rib (2) and carries a scale "50 μm".
• The figure 3 represents a partial section of a 9.52 mm diameter tube De and 0.30 mm thick Tf according to the invention.

The different curves of the figure 4 give, in condensation at 30 ° C with fluid R22, the exchange coefficient Hi (in W / m ² .K) in ordinate as a function of the fluid flow G, in abscissa (in Kg / m ² .s).
The different curves of the figure 5 give, in evaporation at 0 ° C of the fluid R22, the exchange coefficient Hi (in W / m ² .K) in ordinate as a function of the fluid flow G, in abscissa (in Kg / m ² .s).
These curves correspond to a tube according to the invention - noted E according to the figure 3 , and tubes of the state of the art denoted "A", "C", "D" and "S", all these tubes being of the same external diameter De = 9.52 mm. See the examples of realization.

The Figures 6 and 7 indicate, on the ordinate, the exchange refrigeration power measured in watts of a battery of tubes and fins as a function, on the abscissa of the frontal velocity of the air which circulates between the fins expressed in m / s.
These curves correspond to a tube according to the invention - noted E, according to Figures 2a to 2c , and tubes of the state of the art denoted "A", "B" and "S", all these tubes being of the same external diameter De = 8.00 mm. See the examples of realization.
The battery (4), schematized on the figure 8 , is formed of tubes (1) of De = 9.52 mm and forms a block of dimensions: 400 mm x 400 mm x 65 mm, with a density of 12 fins (5) by 25.4 mm, the battery (4) comprising 3 rows of 16 grooved tubes (1), and the refrigerant being R22.
The figure 6 is relative to the condensation measurements on the same battery as before, with an air inlet temperature of 23.5 ° C and a condensing temperature of 36 ° C of the refrigerant R22.
The figure 7 is relative to the evaporation measurements on the same battery, with an inlet temperature of 26.5 ° C, and an evaporation temperature of 6 ° C of the refrigerant R22.

The figure 8 is a schematic perspective view of the battery (4) of tubes (1) with fins (5) used for testing.
The figure 9 graphically represents on the ordinate the cooling capacity gain in evaporation of the batteries, according to the figure 7 , with a reference air speed of 1.25 m / s, as a function of the Cavallini factor on the abscissa for the various tubes tested: smooth tube S, tube E according to the invention, and tubes A and B according to FIG. state of the art.

The figure 10 is a graph indicating, on the ordinate, the heat exchange coefficient Hi (W / m ² .K) on evaporation tubes with the refrigerant R407C, as a function of the weight percentage of vapor in the refrigerant, on the abscissa, the temperature evaporation rate of 5 ° C. The measurements were made with a heat flux of 12 kW / m ² and a mass flow rate of 100 or 200 kg / m ² .s of refrigerant R407C, as shown in the figure, on tubes of diameter D equal to 9 52mm.

The figure 11 is a view of an inner surface portion of a grooved tube according to the invention provided with an axial counter-groove (30), with, below, its schematic representation.

DETAILED DESCRIPTION OF THE INVENTION

According to a modality of the invention illustrated on the Figures 2a to 2c said ribs may form a succession of ribs of height H1 = H and height H2 = a.H1, with a between 0.6 and 0.9, and preferably between 0.70 and 0.85, the value of a being close to 0.75 on the Figures 2a to 2c .
Typically, and as illustrated in these figures, said succession may be an alternation of ribs of height H1 and ribs of height H2 separated by a generally flat groove bottom.
However, as shown on the figure 3 the grooved tubes according to the invention do not necessarily include such an alternation of differentially height ribs as on the Figures 2a to 2c , the ribs may have substantially the same height.

• H allant de 0,18 à 0,3 mm,
• et/ou N inférieur à 75, et allant de préférence de 64 à 70.

De même, lorsque De est au moins égal à 9,55 mm, on peut avoir :

• H allant de 0,25 à 0,40 mm,
• N allant de 70 à 98.

Typically, in the case of 9.52 mm diameter tubes De, one can have:

• H ranging from 0.18 to 0.3 mm,
• and / or N less than 75, and preferably from 64 to 70.

Similarly, when De is at least equal to 9.55 mm, we can have:

• H ranging from 0.25 to 0.40 mm,
• N ranging from 70 to 98.

With regard to the apex angle α, a range according to the invention of the apex angle α ranges from 20 ° to 28 °, an even more restricted range from 22 ° to 25 ° ensuring the best compromise. between the technical performance requirements and those related to the expansion of the tubes for attachment to the fins of the batteries.

With regard to the helix angle β, a preferred range of the helix angle β can range from 22 ° to 30 °, a still more restricted range from 25 ° to 28 ° ensuring the best compromise between technical performance requirements and those related to pressure drop. This angle can vary with the inner diameter Di: it has been found advantageous to have a β / Di ratio greater than 2.40 ° / mm, and preferably greater than 3 ° / mm.

Preferably, said ribs have a "trapezium" type profile with a base of width L _N and a vertex, connected by lateral edges forming between them said apex angle α, as illustrated in FIG. Figure 2c said apex comprising a substantially flat central portion, typically parallel to said base, but possibly sloping with respect to said base.
Whatever the case, said vertex of said rib forming a short side of the trapezium may have rounded edges or not, that is to say, very small radius of curvature, these edges forming a connection of said vertex audits side edges.
Said rounded edges may have a radius of curvature typically ranging from 40 .mu.m to 100 .mu.m, and preferably ranging from 50 .mu.m to 80 .mu.m, as illustrated in FIGS. Figures 2a to 2c . These ranges of radius of curvature correspond to a compromise between the thermal performance of the tubes and the feasibility of the tubes, the tools for making the tubes with the smallest radii of curvature having the most tendency to wear out.
When the edges are not rounded, as shown on the figure 3 , the radius of: curvature can be typically less than 50 microns, and even less than 20 microns.

According to the invention, the width L _R of the flat bottom of said groove and the width L _N of the base of said rib may be such that L _R = bL _N with b ranging from 1 to 2, and preferably 1.1 at 1.8, so as to have a tube having a relatively low weight per meter.

Typically, and as illustrated on Figures 2a to 2c and 3 , said ribs and said flat bottom of said grooves may be connected with a radius of curvature less than 50 microns, and preferably less than 20 microns. In this case, it seems that there is better separation of the liquid refrigerant film from the inner wall of the tube, which promotes heat exchange.

The tubes used according to the invention have even in the absence of axial grooving, a Cavallini factor of at least 3.5. They may advantageously have a Cavallini factor of at least 4.0.

The Cavallini factor Rx ^ 2 (Rx .Rx), which is involved in the evaluation models of the exchange coefficient, is a purely geometrical factor equal to: $${\left[\left[\mathrm{2.}\mathrm{NOT}\mathrm{.}\mathrm{H}\mathrm{.}\left(\mathrm{1}\mathrm{-}\mathrm{Sin}\left(\mathrm{\alpha }\mathrm{/}\mathrm{2}\right)\mathrm{/}\mathrm{3}\mathrm{,}\mathrm{14.}\mathrm{di}\mathrm{.}\mathrm{Cos}\left(\mathrm{\alpha }\mathrm{/}\mathrm{2}\right)\right)\mathrm{+}\mathrm{1}\right]\mathrm{/}\mathrm{Cos\; \beta }\right]}^{\mathrm{\wedge }}\mathrm{2}$$

In order to further increase the Cavallini factor, and as illustrated on the figure 11 , the tubes according to the invention may further comprise an axial groove (30) creating in said ribs notches with a typically triangular profile with a rounded top, said top having an angle γ ranging from 25 to 65 °, said lower part or top is at a distance h from the bottom of said grooves from 0 to 0.2 mm.
Such axial grooving can be obtained once formed said ribs by passage of a grooving wheel in the axial direction.

The grooved tubes according to the invention may be made of copper and alloys of copper, aluminum and aluminum alloys. These tubes can be obtained typically by grooving tubes, or possibly by flat grooving of a metal strip and forming a welded tube.

EXAMPLES OF REALIZATION I - Manufacture of tubes:

The tests were carried out on copper tubes of 8.0 mm or 9.52 mm of external diameter.
The "E" tube of the invention was manufactured according to the Figures 2a to 2c with a diameter of 8.0 mm, and according to the figure 3 with a diameter of 9.52 mm, as well as comparative "S" or smooth, "C", "D", tubes which have a high β helix angle (at least equal to 20 °), intended for the condensation according to the state of the art, and comparative tubes "A" and "B", which have a high apex angle α (at least equal to 40 °) and a low helix angle β (at most equal at 18 °), intended for evaporation according to the state of the art.
The tubes E, A, B, C were made by grooving a smooth copper tube - S tube, while the D tube was manufactured by flat grooving a metal band and then forming a welded tube.

A number of tests have been carried out on 9.52 mm OD copper tubes. These tubes have the following characteristics: Tube type H in mm angle α angle β NOT Rib type Tf mm L _R / L _N E Fig.3 0.20 25 25 66 V 0.30 2.3 B from 0.20 to 0.17 40 16 74 Alternating triangles 0.30 1.88 AT 0.20 50 18 60 triangular 0.30 2.00 VS 0.20 40 30 60 triangular 0.30 1.94 D 0.20 15 20 72 Double crossed ribs * 0.30 3.66 s ------- ------- ------- ----- Smooth tube 0.30 ------- * 72 main ribs of helix angle β equal to + 20 ° interspersed with secondary grooves inclined at an angle of -20 ° relative to the axis of the tube, the depth of the grooves being substantially equal to the height of the ribs main.

A number of other tests were performed on copper tubes of 8.0 mm OD. These tubes have the following characteristics: Tube type H in mm angle α angle β NOT Rib type Tf mm L _R / L _N E Fig.2a 0.20 to 0.16 21 18 46 Alternate trapezoidal 0.26 2.5 B 0.18 to 0.16 40 18 64 Alternating triangles 0.26 2.38 AT 0.18 40 18 50 triangular 0.26 2.33 S ---------- ------ ------ ---- Smooth tube 0.3 -

II - Manufacture of batteries or exchangers:

Winged batteries were manufactured according to the figure 8 from these tubes, placing the tubes in the flanges of the fins and then pressing the tube against the flange of the flanges by expansion of the tube with a conical mandrel. These batteries form a block of dimensions: 400 mm x 400 mm x 65 mm, with a density of 12 fins per 25.4 mm, the battery comprising 3 rows of 16 tubes, and the refrigerant being the R22.

III - Results obtained:

The Figures 4 to 7 , and 9 at 10 illustrate the different results of the invention.

III-1 Results obtained on tubes:

A) Results obtained in condensation with refrigerant R22 on De tubes equal to 9.52 mm: TUBES => Properties E Fig. 3 AT VS D S Weight g / m 89 93.5 95 95 78 Loss of charge dP ** 2500 +/- 100 - 2400 +/- 100 3000 +/- 100 Cavallini factor 3.94 2.72 3.53 --- 1 Coefficient * of exchange Hi average 6850 +/- 50 4950 +/- 50 6300 +/- 50 6000 +/- 50 2850 +/- 50 * Exchange coefficient Hi in W / m ² .K for a fluid flow G equal to 350 Kg / m ² .s. Measuring conditions: temperature 30 ° C, tube length 6 m, and fluid flow G equal to 350 kg / m ² .s
** in Pa / m measured for a fluid flow G equal to 350 kg / m ² .s
B) Results obtained in evaporation with refrigerant R22 on De tubes equal to 8.0 mm: TUBES => Properties E Fig. 2a B AT S Weight g / m 66 68 66 - Loss of charge dP ** 6700 +/- 100 8000 +/- 100 7000 +/- 100 5800 +/- 100 Cavallini factor 3.13 3.02 2.68 1 Coefficient * of exchange Hi average 10500 +/- 100 9500 +/- 100 8500 +/- 100 4500 +/- 100 * Exchange coefficient Hi in W / m ² .K for a fluid flow G equal to 200 Kg / m ² .s. Measuring conditions: temperature 0 ° C, tube length 3 m, flux 10 to 12 kW / m ² .K, vapor content 0.2 to 0.9, and fluid flow G 200 kg / m ² .s
** in Pa / m measured for a fluid flow G equal to 200 kg / m ² .s
C) Results obtained in evaporation with refrigerant R407C on De tubes equal to 9.52 mm: TUBES => Properties E Fig.3 B Weight g / m 89 92.3 Cavallini's Factor 3.94 3.3 Loss of charge dP * 600 +/- 40 700 +/- 40 Coefficient * of exchange Hi local 6000 +/- 100 2500 +/- 100 Loss of charge dP ** 1200 +/- 40 1200 +/- 40 Coefficient ** of exchange Hi mean 11000 +/- 100 3000 +/- 100 Measurement conditions: temperature 5 ° C and flow 12 kw / m ² .K. See figure 10 .
* Exchange coefficient Hi in W / m ² .K and pressure drop dP in Pa / m taken at a fluid flow rate G equal to 100 Kg / m ² .s and with an average vapor head of 0.6.
** Coefficient of exchange Hi in W / m ² .K and pressure drop dP in Pa / m taken at a flow rate of fluid G equal to 200 Kg / m ² .s and with an average vapor head of 0.3 .

III - 2 Results obtained on batteries:

BATTERIES Properties E B AT s Power * Condensation (watt) Fig.6 5025 +/- 150 4230 +/- 127 4100 +/- 164 4050 +/- 121 Power ** Evaporation (watt) Fig.7 4650 +/- 140 4350 +/- 175 4200 +/- 90 4050 +/- 121 * for a frontal air speed of 2.8 m / s.
** for a frontal air speed of 1.5 m / s

IV - Conclusions:

All these results show that the tubes and exchangers or batteries of tubes according to the invention have properties superior to the analogous products of the state of the art, both in evaporation and in condensation.
As a result, and surprisingly, the tubes according to the invention do not only constitute a good compromise of performance in evaporation and condensation, but also have, in absolute terms, excellent performance compared to the tubes of the state. of the technique used in evaporation and those used in condensation, which is of great interest in practice.
In addition, as regards the weight per meter, the values obtained with the tubes according to the invention correspond to a gain ranging from 3.7 to 6.7% compared to the tubes according to the state of the art, taken from same diameter and same thickness Tf, which is considered very important.
Finally, the tubes according to the invention of the type E can be advantageously manufactured by high-speed grooving of smooth non-grooved copper tube, typically at a grooving speed close to that used for the type B tubes, namely at least 80 m / min.

ADVANTAGES OF THE INVENTION

The invention has great advantages.
Indeed, on the one hand, the tubes and batteries used according to the invention have high intrinsic performances.
On the other hand, these performances are high in both evaporation and condensation, which allows the use of the same tube for these two applications.
In addition, the tubes have a relatively low weight per meter, which is very advantageous both from a practical point of view and from the economic point of view with a relatively low material cost.

Finally, the tubes used according to the invention do not require specific manufacturing means. They can be manufactured with standard equipment and especially with the usual production rates.

LIST OF REFERENCES

Grooved tube 1 Rib 2 Groove 3 Axial groove 30 Drums. 4 Fin 5

Claims (18)

1. Use of a heat exchanger operating in reversible mode, in evaporation or in condensation using a phrase-change refrigeration fluid, said exchanger comprising grooved metal tubes (1), of thickness T_f at the bottom of the groove, with an outside diameter D_e, said tubes being grooved internally by N helical grooves (2) of apex angle α, height H, base width L_N and helix angle β, two consecutive ribs being separated by a groove (3) typically with a flat bottom of width L_R, with a pitch P equal to L_R + L_N.

   a) the outside diameter D_e being between 4 and 20 mm,

   b) the number N of ribs ranging from 46 to 98, depending in particular on the diameter D_e,

   c) the height H of the ribs ranging from 0.18 mm to 0.40 mm, depending in particular on the diameter D_e,

   d) the apex angle α such that 20° ≤ α < 28°,

   e) the helix angle β ranging from 18° to 35°,

   f) said tube having a Cavallini factor of at least 3.5,

   so as to obtain simultaneously a high heat exchange coefficient in evaporation and condensation, a low pressure drop and a tube as lightweight as possible.
2. Use according to claim 1, in which said ribs form a succession of ribs of height H1 = H and height H2 = a.H1, with a between 0.6 and 0.9.
3. Use according to any one of claims 1 to 2, in which said succession is an alternation of ribs of height H1 and ribs of height H2 separated by a typically flat groove bottom.
4. Use according to any one of claims 1 to 3, in which, when D_e is less than or equal to 9.55 mm, this gives:

   - H ranging 0.18 to 0.3 mm, and preferably 0.20 to 0.25 mm,

   - and/or N less than 75, and preferably ranging from 64 to 70.
5. Use according to any one of claims 1 to 3, in which, when D_e is at least equal to 9.55 mm, this gives:

   - H ranging from 0.25 to 0.40 mm,

   - N ranging from 70 to 98.
6. Use according to one of claims 1 to 5, in which the angle α ranges from 22° to 25°.
7. Use according to any one of claims 1 to 6, in which the helix angle β ranges from 22° to 30°.
8. Use according to any one of claims 1 to 7, in which the helix angle β ranges from 25° to 28°.
9. Use according to any one of claims 1 to 8, in which said ribs have a profile of the "trapezium type with a base and vertex, said vertex comprising a substantially flat central part, and optionally a slope with respect to said base.
10. Use according to claim 9, in which the vertex of said rib forming a small side of the trapezium has rounded edges.
11. Use according to claim 10, in which said rounded vertex or said rounded edges have a radius of curvature ranging typically from 40 µm to 100 µm, and preferably 50 µm to 80 µm.
12. Use according to any one of claims 1 to 11, in which the width L_R of the flat bottom of said groove and the width L_N of the base of said rib are such that L_R = b.L_N with b ranging from 1 to 2, and preferably 1.10 to 1.8.
13. Use according to any one of claims 1 to 12, in which said ribs and said flat bottom of said grooves are connected with a radius of curvature typically less than 50 µm and preferable less than 20 µm.
14. Use according to any one of claims 1 to 13, in which the Cavallini factor is at least 4.0.
15. Use according to any one of claims 1 to 14, in which the tubes further comprise an axial grooving creating in said ribs recesses with a typically triangular profile with a rounded vertex, said vertex having an angle γ ranging from 25° to 65°, said bottom part or vertex is at a distance h from the bottom of said grooves ranging from 0 to 0.2 mm.
16. Use according to any one of claims 1 to 15, in which the tubes are made from copper and copper alloys, aluminium and aluminium alloys.
17. Use according to any one of claims 1 to 16, in which the tubes have typically been obtained by the grooving of tubes, or optionally by flat grooving of a metal strip and then formation of a welded tube.
18. Use according to any one of claims 1 to 17, for reversible hair conditioners and multi-tube exchangers as coolers.

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