"Heat exchange unit and method for manufacturing a heat exchange unit"

TECHNICAL FIELD

The present invention is related to a heat exchange unit, in particular for cooling appliances, and to a method for manufacturing a heat exchange unit.

PRIOR ART

Convection heat exchangers in which a fluid circulates around a solid, for example inside a tube, and in which, given the existence of a temperature difference between both, a heat exchange takes place, are known.

In particular heat exchangers in which a tube through which a cooling liquid circulates is arranged on a metal sheet are known. Such exchangers are used, for example, in cooling appliances, freezers, boilers, etc. The tube is generally arranged on the largest possible surface of the metal sheet to improve the heat exchange, so it is usually necessary to bend the tube so that it has the same shape as the sheet on which it is going to be fixed, as shown for example in US2386889A. To that end, the tube can be bent on one side and the sheet on the other, and the tube can be fixed to the sheet after bending. Another option is to fix the tube to the sheet and bend them together. It is known that bending the tube and the sheet together can cause the crushing of the tube, which is not convenient because it would limit circulation of the cooling liquid. Bending the tube and the sheet together is also known to cause marks on the sheet, damaging it.

Documents US1987422A and GB438267A describe a method for making heat exchangers. Said method comprises the following steps: a step in which a conduit is placed on a metal sheet, a step in which said conduit is fixed to the sheet through cleats, said cleats allowing the conduit to slide under the same, and a step in which the unit formed by the sheet and the conduit is bent, sliding the conduit with respect to the sheet such that the radius of curvature of the conduit is substantially greater than that of the sheet.

Document US2625378A discloses a heat exchange comprising a metal sheet, a metal exchange tube supported on said sheet, and fastening means for fastening the tube to the sheet, said heat exchange being bent with respect to at least one bend line and the fastening means comprising a cover covering almost the entire length of the tube, said cover being fixed to the sheet by means of adhesive.

DISCLOSURE OF THE INVENTION

The object of the invention is to provide a heat exchange unit, and a method for manufacturing a heat exchange unit, as defined in the claims.

A first aspect of the invention is related to a heat exchange unit, in particular for a cooling appliance, comprising a metal sheet, at least one metal exchange tube supported on said sheet, and fastening means for fastening the tube to the sheet, said unit being bent with respect to at least one bend line. The fastening means comprise a cover covering the entire or almost the entire length of the tube, said cover being fixed to the sheet by means of adhesive. The surface of the cover in contact with the tube has no adhesive, therefore said surface having a coefficient of friction that allows sliding said tube under said cover when bending the unit with respect to said at least one bend line.

A second aspect of the invention is related to a method for manufacturing a heat exchange unit comprising a metal sheet and at least one metal exchange tube. The method comprises the following steps:

- a step in which the tube is arranged on the sheet,

- a step in which the entire or almost the entire length of the tube is covered with a cover, the surface of the cover in contact with the tube having a coefficient of friction that allows sliding said tube under said cover,

- a step in which the cover is fixed to the sheet and

- a step in which the sheet is bent, the tube being slid under the cover. The sliding the tube under the cover enables being able to bend the sheet and the tube at the same time, making up for the developmental difference between the sheet and the tube due to the different radii of curvature. The unit of the invention has the additional advantage that by covering the entire or almost the entire length of the tube with the cover, contact between the tube and the sheet is assured and it allows insulating the contact surface of the tube with the sheet from external elements such as insulators (for example polyurethane foam in the case of units for cooling appliances), allowing the contact surface to be maximum and thereby improving thermal efficiency of the heat exchanger.

These and other advantages and features of the invention will become evident in view of the drawings and the detailed description of the invention.

DESCRIPTION OF THE DRAWINGS

Figure 1 shows a view of a first embodiment of the heat exchange unit according to the invention before the unit is bent.

Figure 2 is a partial cross-section view of the heat exchange unit shown in Figure 1 .

Figure 3 is a partial perspective view of the heat exchange unit shown in Figure 1 . Figure 4 is a plan view of the heat exchange unit shown in Figure 1 after the unit is bent.

Figure 5 is detail A of Figure 4. Figure 6 shows a second embodiment of the heat exchange unit according to the invention before the unit is bent. DETAILED DISCLOSURE OF THE INVENTION

Figures 1 to 5 show a first embodiment of the heat exchange unit 1 of the invention, in particular for a cooling appliance, according to the invention. The heat exchange unit 1 comprises a metal sheet 2, a metal exchange tube 3 supported on said sheet 2, and fastening means for fastening the tube 3 to the sheet 2. In this first embodiment, the metal sheet 2 is rectangular, being able to have different shapes in other embodiments. The section of the tube 3 is substantially circular. In other embodiments, the part of the tube 3 that is supported on the sheet 2 can be substantially planar. The contact surface between the sheet 2 and the tube 3 would thereby be increased, thus improving thermal efficiency of the unit 1 .

The heat exchange unit 1 is bent with respect to the bend line 7a, 7b, 7c, 7d, as can be seen in Figure 4. Therefore in this embodiment, the unit 1 is bent forming a closed enclosure with a rectangular base. In other embodiments, the heat exchange unit 1 can be bent configuring different shapes. Heat exchange units 1 which are bent into a U shape, L shape, C shape, etc., are common.

In this first embodiment, the fastening means comprise a cover 4 covering almost the entire length of the tube 3, as shown in Figure 1 . Since the cover 4 covers almost the entire length of the tube 3, contact between the tube 3 and the sheet 2 is assured and it allows insulating the contact surface of the tube 3 with the sheet 2 from external elements such as insulators (for example polyurethane foam in the case of units for cooling appliances), allowing the contact surface to be maximum and thereby improving thermal efficiency of the heat exchanger 1.

Furthermore, the surface of the cover 4 in contact with the tube 3 has a coefficient of friction that allows sliding said tube 3 under said cover 4 when bending the unit 1 with respect to the bend lines 7a, 7b, 7c, 7d. Sliding said tube 3 under said cover 4 enables bending the sheet 2 and the tube 3 at the same time, said sliding of the tube 3 allowing compensating the difference in the radii of curvatures of the sheet 2 and the tube 3, as can be seen in Figure 5. Figure 1 shows the arrangement of the tube 3 with respect to the sheet 2 before bending the unit. It also shows with discontinuous lines the disposition the tube 3' will have with respect to the sheet 2 once the unit 1 is bent. ln this first embodiment, the cover 4 comprises an aluminum tape 5. In other embodiments, the tape 5 can be made of any other material with thermal conduction properties, such as copper or any other known material complying with said features. Said tape 5 has adhesive on the side facing the sheet 2 whereby it fixes the cover 4 to the metal sheet 2.

In other possible embodiments in which the tape 5 does not have adhesive, the fastening means can comprise an adhesive tape for fastening the cover 4 to the sheet 2.

On the other hand, in this embodiment the cover 4 comprises a plastic strip 6 fixed to said tape 5, the surface of the plastic strip 6 corresponding with the surface of the cover 4 in contact with the tube 3. The plastic strip 6 must be wide enough for the tube 3 to be able to slide under the cover 4.

In other possible embodiments, the strip can be made of any other material provided that it meets the condition that the coefficient of friction of said strip allows sliding the tube 3 under the cover 4. On the other hand, in other embodiments, the strip can be eliminated if the condition that the contact surface of the tape 5 with the tube 3 allows sliding the latter is met. To that end, at least the part of the tape 5 in contact with the tube 3 should not have elements that prevent sliding the tube 3 in the tape 5, such as adhesives for example. Figure 6 shows a second embodiment of the heat exchange unit 1 according to the invention. This second embodiment differs from the first embodiment in that the cover 4 does not cover the surfaces of the tube 3 close to the bend lines 7a, 7b, 7c, 7d. When bending the heat exchange unit 1 , the cover 4 often becomes detached or it can even partially break in these areas close to said bend lines 7a, 7b, 7c, 7d. The remaining features are similar to those of the first embodiment, so it is not necessary to describe them again.

The method for manufacturing the heat exchange unit 1 according to the invention comprises at least the following steps:

- first the tube 3 is arranged on the sheet 2, - then the entire or almost the entire length of the tube 3 is covered with a cover 4, for example as shown in Figure 1 or Figure 6. The surface of the cover 4 in contact with the tube 3 has to have a coefficient of friction that allows sliding said tube 3 under said cover 4 ,

- next the cover 4 is fixed to the sheet 2 and

- finally the sheet 2 is bent, the tube 3 being slid under the cover 4. As previously explained, the unit can be bent under different shapes, being able to be bent forming a closed enclosure as shown in Figure 4 for example.