EP2567167A2

EP2567167A2 - Refrigerator and evaporator for same

Info

Publication number: EP2567167A2
Application number: EP11712574A
Authority: EP
Inventors: Stefan Holzer
Original assignee: BSH Bosch und Siemens Hausgeraete GmbH
Current assignee: BSH Hausgeraete GmbH
Priority date: 2010-05-04
Filing date: 2011-04-07
Publication date: 2013-03-13
Anticipated expiration: 2031-04-07
Also published as: WO2011138117A2; CN102869941A; EP2567167B1; RU2528799C2; CN102869941B; DE102010028527A1; WO2011138117A3; RU2012147335A

Abstract

The invention relates to an evaporator for a refrigerator, comprising a pipe (11) carrying refrigerant, at least one carrier plate (7, 8, 9, 10), to which the pipe (11) is fixed, and a graphite-containing heat distributor layer (14, 16, 21) disposed between the pipe (11) and the carrier plate (7, 8, 9, 10).

Description

Refrigerating appliance and evaporator for it

The present invention relates to a refrigeration device, in particular a domestic refrigerator, and a usable in such a refrigerator evaporator. Such an evaporator conventionally comprises a pipe in which refrigerant circulates, a support plate to which the pipe is fixed and via the one

Heat exchange takes place between the tube and an interior of the refrigerator cooled by the evaporator, and a heat spreader layer disposed between the tube and the carrier plate, which provides efficient heat transfer between the carrier plate and the tube.

From DE 20 2005 000 909 U1 an evaporator of this type is known in which the carrier plate is a freezer compartment trough formed in an inner container of the refrigeration device, around which the tube is wound. As a heat spreader layer, metal plates may be disposed between the tube and the freezer tray. If such a metal plate touches the freezer well over a large area, it causes a good

Heat coupling of the pipe to the freezer. However, it is hard and expensive.

A slightly cheaper solution is to glue a 30 micron thick aluminum foil to the outer surfaces of the freezer compartment and wrap and glue the tube around it. If the adhesive layer that fixes the tube to the aluminum foil is thin enough, sufficient thermal conductivity of the evaporator for practical requirements is readily achievable. However, it is precisely this thin adhesive layer that can not be reliably realized everywhere. Fluctuations in the ductility of the tube may cause individual turns of the tube to not conform tightly to the aluminum foil, leaving an air gap therebetween or creating a thick layer of adhesive that significantly impedes heat transfer. Although the aluminum foil is cheaper than a metal plate, but still there is a need for a more cost-effective solution that reliably ensures good heat exchange between the tube and the support plate. Object of the present invention is to provide an evaporator for a refrigerator, which at low cost the conventional evaporator in its thermal

Characteristics is at least equal.

The object is achieved by graphite-containing in an evaporator for a refrigerator with a refrigerant-carrying tube, at least one support plate to which the tube is attached, and arranged between the tube and the carrier plate heat spreader layer graphite. The thermal conductivity of graphite is better than that of many metals and only slightly lower than that of aluminum at significantly lower cost. It is therefore sufficient a layer thickness of the graphite, which is only slightly larger than that of the aluminum foil to provide an evaporator whose

Heat exchange performance is at least as large as that of a conventional one

Evaporator of the same size of the type described above.

The graphite content of the heat spreader layer should preferably be at least 100 mg / cm ² , more preferably at least 200 mg / cm ² , corresponding in each case to a layer thickness of pure graphite of approximately 50 or 100 μm. A graphite layer of this thickness can easily reach a heat transfer coefficient of 0.4 Wm ^"2 K ^{" 1} .

According to a first aspect of the invention, the heat spreader layer comprises a sheet of substantially pure graphite. As substantially pure within the meaning of the present invention, a graphite layer can be considered if any impurities present do not affect the thermal conductivity of the layer.

Since pure graphite is very soft, a pure graphite foil is not easy to handle. In a second embodiment, the heat spreader layer may comprise a graphite filled plastic film. Although such a plastic film must be generally thicker than a pure graphite foil to achieve the same thermal conductivity, but has the advantage of more convenient handling. The film may have a macroscopically homogeneous structure with embedded in a plastic matrix graphite particles or a

Sandwich structure with a sandwiched between plastic layers graphite layer. A third embodiment results as a heat distribution layer a graphite-containing plastic plate into consideration.

It is also conceivable to combine the three embodiments mentioned in an evaporator with each other, as will be explained in more detail below.

An advantage of pure graphite is its compliance, which makes it possible in the case of

Mounting the tube to press a recess in the graphite layer and in this way a close thermal contact between the tube and the

Produce heat spreader layer on a much larger surface than would be possible conventionally between the tube and a metal plate or adhered to a solid support plate metal foil. Also in the graphite filled

Plastic film, such a depression can be easily formed, since such a film will generally be the more compliant, the higher their graphite content. In the case of a graphite-containing plastic plate, such a recess may be formed in advance on the plate to subsequently lay the tube therein.

Due to their - in comparison to the films, relatively high - stiffness, the plastic plate may also have the tube clamping projections that produce a close thermal contact between plastic plate and tube.

Preferably, these projections have mutually opposite concave flanks, in which the tube can be inserted.

In order to provide a large contact surface for efficient heat transfer, the projections may conveniently be formed as ribs extending along the tube.

The support plate may form a wall of a freezer compartment or a refrigerating compartment in a refrigerator according to the invention.

When at least two walls of the freezer compartment are support plates of the heat exchanger, the heat distribution layer may comprise a graphite-containing plastic plate on a first of these walls and a foil on a second wall. Due to the higher in comparison to the film carrying capacity of the plastic plate, the tube can be laid closer to the first wall than at the second.

Preferably, the first wall is a rear wall or a bottom wall of the

Freezer. In the case of the rear wall, the use of the plastic plate makes sense, because it is not practical here to anchor the tube by wrapping around the freezer. On a bottom wall, a denser installation of the pipe may be desirable in order to provide a high cooling capacity for rapid freezing of stored refrigerated goods.

However, the invention is also applicable to an evaporator, the support plate is arranged freely in an interior of the refrigerator.

Further features and advantages of the invention will become apparent from the following description of embodiments with reference to the accompanying figures. FIG. 1 shows a schematic cross section through a domestic refrigerator according to a first embodiment of the invention; FIG. 2 shows a schematic cross section through a refrigeration device according to a second

Embodiment of the invention;

Fig 3 n not to scale partial section through the freezer compartment of the refrigerator

Fig. 1 or 2;

4 shows a section through a wall of the freezer compartment;

5 shows a wall section of the freezer compartment according to a modified

design; and

6 shows a schematic perspective view of a freezer inner container with an evaporator according to the invention. Fig. 1 shows a section through a combination household refrigeration appliance with a body 1, a normal refrigeration compartment 2, a freezer compartment 3 and doors 4, 5 for closing the two compartments 2, 3. The compartments 2, 3 are in a conventional manner by Plastic deep-drawn inner container delimited by a surrounding insulating material layer 6. The inner containers are each box-shaped with a front side open to the door 4 or 5, a rear wall 7, ceiling floor and side walls 8, 9 and 10 respectively. The insulation material layer 6 facing outer sides of the walls 8, 9, 10 of the freezer compartment Inner container are covered with a graphite or graphite-filled plastic film, which is not visible in Fig. 1 due to their small thickness. The foil may be glued individually piece by piece to each wall 8, 9, 10, or it may be wound in one piece around all four walls 8, 9, 10. A refrigerant pipe 1 1 made of aluminum extends helically over the walls 8, 9, 10 of the inner container in close contact with the film.

Fig. 2 shows an alternative embodiment of a refrigeration device according to the invention. In this embodiment, an inner container surrounded by an insulating material layer 6 delimits an inner space 12 which is subdivided by a box 13 mounted therein into a freezer compartment (inside the box 13) and a normal refrigerated compartment 2 (outside the box 13). The molded plastic or metal walls of the box 13 are externally covered with a sheet of graphite or graphite-filled plastic, and around the film is helically wrapped a refrigerant pipe 1 1.

Fig. 3 shows schematically and not to scale a partial section through the freezer compartment inner container of the refrigerator of FIG. 1 or the box 13 of FIG. 2. To see the ceiling wall 8 and adjacent parts of the side walls 10. The designated here with 14 film Graphite or of graphite-filled plastic extends integrally over the walls 8, 10. By the forces occurring when the tube 1 1 is wound around the container, the tube 11 is in the vicinity of rounded edges 15 between the walls 8, 10 in the yielding Slide 14 is pressed. The original thickness of the film 14 at these locations is indicated by a dashed line. From this flexibility of the film results in a large-area contact between the film 14 and the tube 1 1 in the vicinity of the edges 15, which in turn provides for a highly efficient heat transfer between the tube 1 1 and the film 14. Fig. 4 shows a section through a part of the ceiling wall 8, on which is clearly visible, as the tube 1 1 has pressed into the film 14.

In addition, as shown in Fig. 3, extending between two corners segment of the tube 1 1 be slightly curved and still touch the film 14 over its entire length. The effectiveness of the heat exchanger formed by the tube 1 1, the film 14 and the walls 8, 9, 10 of the inner container is therefore equal to the effectiveness of a conventional evaporator using an aluminum foil as a heat spreader layer between the refrigerant tube and the inner container wall, even if the heat transfer coefficient of the film 14 should be lower than that of conventional

Aluminum foil.

In practice, however, it is not a problem to give the film 14 also an at least equivalent heat transfer coefficient. If the film 14 consists of pure graphite, a thickness of 100 to 200 μm suffices to achieve a heat transfer coefficient of approximately 0.5 μm ² K ^-1 , which corresponds to that of a conventional aluminum foil of 30 μm thickness. This layer thickness corresponds to a graphite amount of about 100 to 200 mg / cm ² , and it is to be assumed that a corresponding amount of graphite will also be sufficient in a graphite-filled film in order to achieve a heat transfer coefficient of the same level.

Instead of the flexible film 14 can be provided as heat spreader layer between the pipe 1 1 and the walls 7, 8, 9 and / or 10, a plastic plate 16, whose thermal conductivity is increased by the addition of graphite. While the amount of graphite that can be added to most plastics without losing their strength is limited, the thermal conductivity of plastic sheet 16 will generally be significantly less than that of pure graphite. However, this disadvantage is of little importance, since suitable plastics are available inexpensively, so that sufficient for practical purposes heat transfer coefficient of at least 0.4 watts per square meter Kelvin can be achieved, in which the thickness of the plastic plate 16 is chosen sufficiently large. In practice, a thickness of the plate 16 of 1 to 2 mm is sufficient to accommodate the required amount of graphite from about 100 to 200 mg / cm ² . A major advantage of the plastic plate 16, however, is that on her, as shown in the view of Fig. 5, projections 17 can be formed, which clamp the pipe 1 1 and in this way for an efficient heat transfer between the pipe 1 and the plate 16 provide. Such projections may be formed, for example, as hooks which press the tube against the plate; preferred is the embodiment shown in Fig. 5, in which the projections 17 are formed as elongated ribs, each pairwise define a groove in which the tube 1 1 is clamped. To further improve the heat transfer, the rib-shaped projections 17 of FIG. 5 facing concave flanks 18 whose radius of curvature corresponds to the outer radius of the tube 1 1, so that the flanks 18 and the tube 1 1 to more than half of the pipe circumference.

Fig. 6 shows in a perspective view obliquely from below a freezer compartment inner container according to a further development of the present invention. Ceiling bottom and side walls 8, 9, 10 of the inner container are, as described with reference to FIGS. 1 to 3, coated with a graphite-containing film 14, and drawn in Fig. 6 in dashed lines section 19 of the refrigerant raw r 1 1 1 pulls is in contact with the film 14 helically around the walls 8, 9, 10. Since on the rear wall 7 of the inner container, the tube 1 1 can not be secured as in the case of the section 19 by sloshing around, here is a plate 16 with reference to 5 and a meandering over the plate 16 extending portion 20 of the tube 1 1 is respectively clamped between the plate 16 protruding projections 17. Thus, the freezer can be cooled from five sides at the same time; Heat can only penetrate through its open front. In order to compensate for the incidence of heat at the open front and to obtain the most homogeneous temperature distribution in the freezer compartment, it is desirable to increase the density in which the tube 1 1 is laid in a front region of at least the bottom wall 9. However, such an increased laying density on a single wall is wrapped with the helically around the walls 8, 9, 10

Pipe section 19 not realizable. In order nevertheless to be able to increase the laying density in the front region of the bottom wall 9, a second plate 21 of graphite-containing plastic is attached here: it can be glued to the film 14, or the film 14 is recessed in the area occupied by the plate 21. A segment 22 of the around the walls 8, 9, 10 wound pipe section 19 extends over the plastic plate 21 in the longitudinal direction. On both sides of this tube segment 22 pairs of projections 17 are formed, which clamp between them to the tube segment 21 parallel tube segments 23, 24. These pipe segments 23, 24 are connected to each other and to one end of the pipe section 19 via arches 25, 26. A along an edge 15 between the bottom and side walls 9, 10 extending pipe section 27 establishes a connection to the extending over the rear wall 7 pipe.

Claims

1. evaporator for a refrigerator with a refrigerant-carrying tube (1 1), at least one support plate (7, 8, 9, 10) to which the tube (1 1) is fixed, and one between the tube (1 1) and the heat carrier layer (14, 16, 21) is graphite-containing the heat transfer layer (14, 16, 21) arranged carrier plate (7, 8, 9, 10).

2. evaporator according to claim 1, characterized in that the graphite part of the

Heat spreader layer (14, 16, 21) at least 100mg / cm ² , preferably at least 200mg / cm ² , is.

3. evaporator according to claim 1 or 2, characterized in that the

Heat spreader layer (14, 16, 21) has a heat transfer coefficient of at least 0.4

Wm has ^"2 K ^{" 1} .

4. evaporator according to claim 1, 2 or 3, characterized in that the tube (1 1) extends in a recess of the heat spreader layer (14).

5. Vaporizer according to one of claims 1 to 4, characterized in that the heat spreader layer comprises a film (14) made of substantially pure graphite.

6. evaporator according to one of claims 1 to 4, characterized in that the heat spreader layer comprises a graphite-filled plastic film (14).

7. evaporator according to one of claims 1 to 4, characterized in that the heat spreader layer comprises a graphite-containing plastic plate (16, 21).

8. evaporator according to claim 7, characterized in that the plastic plate (16, 21) the tube (1 1) clamping projections (17).

9. evaporator according to claim 8, characterized in that the projections (17) have mutually opposite pairs of concave flanks (18).

10. evaporator according to claim 8 or 9, characterized in that the projections (17) are formed as along the tube (1 1) extending ribs.

1 1. Refrigeration appliance, in particular domestic refrigeration appliance, with an evaporator according to one of the preceding claims, characterized in that the carrier plate (7, 8, 9, 10) forms a wall of a refrigerator or freezer compartment of the refrigerator.

12. Refrigerating appliance according to claim 1 1, characterized in that at least two walls (7, 8, 9, 10) of the freezer compartment support plates of the heat exchanger, and that the heat spreader layer (14, 16, 21) on a first of the walls (7, 9) one

graphite-filled plastic plate (16, 21) and on a second wall (9) comprises a film (14).

13. Refrigerating appliance according to claim 12, characterized in that the tube (1 1) on the first wall (9) is laid denser than on the second wall (10).

14. Refrigerating appliance according to claim 12 or 13, characterized in that the first wall is a rear wall (7) or a bottom wall (9) of the freezer compartment container.

15. Refrigerating appliance with an evaporator according to one of claims 1 to 10, characterized

characterized in that the carrier plate is arranged freely in an interior of the refrigeration device.