EP2158434A1

EP2158434A1 - Rear wall condenser for domestic refrigerators and freezers

Info

Publication number: EP2158434A1
Application number: EP08758094A
Authority: EP
Inventors: Olaf Hempel; Eberhard Wobst; Carsten Heinrich; Markus Müller
Original assignee: Institut fuer Luft und Kaeltetechnik Gemeinnuetzige GmbH
Current assignee: Institut fuer Luft und Kaeltetechnik Gemeinnuetzige GmbH
Priority date: 2007-05-22
Filing date: 2008-05-20
Publication date: 2010-03-03
Also published as: KR20100032388A; CN101680690B; US20100206531A1; WO2008141626A1; CN101680690A; KR101468912B1

Abstract

The invention relates to a condenser for refrigerators and freezers,with free convection, particularly for domestic refrigerators and freezers. The condenser has at least one tape-like pipeline (1), the width of which is at least twice the thickness, which has at least two separate channels (3, 4) which extend next to one another and which, when used as intended, extend on edge and largely close to and parallel to the lower edge of the refrigerator or freezer. For pipeline sections, disposed consecutively in the flow direction, the upper edge of a preceding section is offset in the flow direction parallel to the lower edge of the pipeline section which follows. A reasonably priced condenser with excellent heat exchange properties can be produced by the use of conventional, commercial, extruded aluminum profile pipes.

Description

Rear wall condenser for household refrigerators

The invention relates to a condenser for refrigeration appliances with free convection, in particular household refrigerators such as refrigerators, freezers or fridge freezers, which is simple and inexpensive to produce and has a high efficiency.

The usual refrigerators, freezers or fridge freezers are so-called compressor refrigerators. Since refrigerators that operate on other cooling principles, such. As absorber cooling units, which are characterized by a low noise, or thermoelectric cooling units that allow compact designs, in addition to these specific advantages, however, have the disadvantage of a much higher energy consumption, they find only in niche application.

In compressor refrigerators, a compressor compresses a gaseous refrigerant that heats up. The refrigerant is passed through a condenser located on the outside of the unit. Using the condenser, the refrigerant releases heat to the environment and condenses. Thereafter, the refrigerant flows to reduce the pressure via a throttle, such. As an expansion valve or capillary tube, located in the inside of the refrigerator evaporator. In this the refrigerant evaporates and cools down strongly. The evaporator allows for heat exchange, thereby cooling the interior of the refrigerator.

The energy consumption of a compressor chiller depends largely on how well the condenser transfers heat to the environment. Due to the constantly rising energy and electricity prices on the one hand and a growing environmental awareness on the other hand, it is becoming increasingly important to produce energy-saving household refrigerators.

The condenser used for domestic refrigerators usually consist of a meandering curved pipe to which wire ribs are welded for better heat dissipation. To the heat transfer by heat radiation on To increase, the pipe and the wire ribs are painted black. The condenser is located mainly on the back of the refrigerator.

However, such condenser have the disadvantage that the wire fins heat up to the same temperature as this only in the vicinity of the connection with the pipe. Due to the comparatively large distances between the pipes and due to the unfavorable geometry of the wire ribs, namely their large length and their small diameter, larger areas of the ribs are only slightly heated. The result is a low rib efficiency. This leads to a comparatively poor heat transfer, which ultimately results in an increased power consumption of the household refrigerating appliance.

In other known embodiments of condensers no wire ribs, but a line completely covering sheet metal plate are welded to the pipe. In order to achieve a good thermal connection between the pipeline and the metal plate, however, as many spot welds as possible must be installed between the line and the metal plate. It is cheaper to connect the line with a continuous welding or soldering seam to the sheet. Although this achieves an improved, but still uneven, temperature distribution over the heat exchanger surface. The mean temperature difference between the refrigerant and the air is thereby lower, and thus also the heat transfer rate per unit area. Another disadvantage is the relatively high manufacturing expense.

Numerous proposals are known from the prior art, which have the goal of improving the heat output and / or reducing the manufacturing costs of condensers for domestic refrigerators.

For example, EP 0 125 642 A2 proposes a refrigerator with a rear wall condenser which merely consists of a meander-shaped curved pipeline. In this case, the straight pipe sections have an elliptical cross section, the curved one circular. Since tubes with an elliptical cross-section have a larger surface compared to tubes with a circular cross-section, the welding of wires or sheets is dispensed with. Although this will However, the efficiency of the heat exchange is not improved.

EP 0 843 138 A1 describes a back wall condenser for domestic refrigerators, which shows a meander-shaped bent pipe which is clamped between two sheets. One of the two plates forms with a third plate a container which is filled with a liquid of high heat capacity.

CN 1616904 A discloses a back-wall condenser consisting of two horizontally superposed pipes connected by means of many pipes connected in parallel and vertically arranged. The vertical tubes have a diameter of 1 to 3 mm, that is, they are comparatively thin. Using the horizontal tube above, the refrigerant is distributed to the vertical tubes, in the underlying tube this is collected again. To improve the heat dissipation, a sheet may be attached to the pipes. By using many thin tubes or microchannel lines, a large surface area and thus a good heat exchange can be achieved. However, the use of thin tubes or micro-channel lines makes, in order to avoid excessive pressure losses, a parallel circuit necessary, which increases the production cost. It is also disadvantageous that the air flow runs continuously along the tubes or microchannel lines, so that comparatively thick, laminar boundary layers are built up there, which prevent optimal heat dissipation.

Furthermore, condenser for forced convection refrigerators are known in which extruded aluminum profile lines are used, which are band-shaped and have a plurality of parallel channels. For example, EP 1 557 622 A2, US 2006/0144076 A1 and DE 10 2004 024 825 A1 describe condenser for forced convection with headers and condenser without headers corresponding in US 2005/0076506 A1 and JP 06317363.

For use as a back wall condenser for refrigeration appliances with free convection these condensers are not suitable due to their design. Even if the condenser were placed upright and flowed through free convection from the bottom up with air, they would have an extremely poor efficiency, firstly the transverse profile lines would cause a high flow resistance and secondly because of their orientation could give off little heat by radiation to the environment. In free convection condensers, however, unlike condensers with forced convection, up to 45% of the heat is emitted by radiation.

The object of the invention is to eliminate the disadvantages of the prior art. In particular, a condenser is to be created for household refrigerators with free convection, which has a high efficiency and is simple and inexpensive to produce.

This object is achieved by the characterizing features of claim 1; advantageous embodiments of the invention will become apparent from the claims 2 to 15.

According to the invention, the condenser for refrigeration appliances with free convection at least one line for the refrigerant, which is formed like a strip whose width is at least twice their thickness and in which there are at least two separate, side by side extending channels. When used as intended, the line runs edgewise and for the most part almost parallel to the lower edge of the refrigeration device.

The flow of the individual lines through the air takes place by free convection, ie from below or above. The air hits the narrow edges of the lines.

In line sections arranged in flow directions, wherein the line sections can be both sections of the same line as well as sections of different lines of the condenser, the upper edge of the preceding is offset parallel to the lower edge of the subsequent line section in the flow direction. Thus, a fresh start of the air flow takes place at each line section and the insulating laminar boundary layer at the line sections is consequently kept thin. As a result, the efficiency of the condenser can be increased by up to 15%. The parallel displacement between the upper and lower edges is achieved in that either the line sections are arranged offset in parallel in the flow direction or these are tilted. From a flow point of view, only tilt angles between 0 and 45 ° make sense. It is also conceivable to simultaneously displace and tilt the line sections; however, this does not achieve any particular advantage.

In one embodiment of the condenser according to the invention, in which this is characterized in that it has a particularly small flow resistance on the refrigerant side, the condenser has a vertically arranged one

Collecting pipe at the inlet and outlet of the refrigerant. The two manifolds may have a round, namely circular, semi-circular, elliptical and oval, or angular, namely triangular, square or rectangular, flow cross-section. In the collecting tube at the entrance, a distribution device can be integrated.

The headers are connected by a plurality of horizontally located and at different heights parallel to each other arranged lines for the refrigerant mainly in parallel. Through installations in the headers but also a series connection of all lines or a series connection of several parallel lines can be generated, so that the refrigerant flows through the condenser meandering from top to bottom. The lines run straight between the headers or are bent horizontally wave or meandering.

It is envisaged that a plurality of lines are arranged side by side, usually parallel spaced, on a horizontal plane. It is advantageous to install spacers between these lines, for example in the form of sheets. This creates a secondary heat exchanger surface at the same time.

In another embodiment of the condenser, which is characterized by a particularly simple structure, the line for the refrigerant bent in at least one flat-shaped layer runs spiral, helical, helical, helical or three-dimensional meandering. Here no headers are used. The preferred three-dimensional meandering arrangement of the conduit means that it is meandering in lateral view and also has a spatial depth. Such a conduit thus typically has a helical or helical course in space, but does not have the otherwise usual round or elliptical cross-sectional areas in the case of screws / helices, but has a cross-section (in plan view) which is either in the form of an oblong Rectangles with rounded corners or the shape of the outline of an elongated "eight" has.

Under a flat shaped position is a flat arrangement of the line, such. B. in the form of a three-dimensional meander understood, which has a spatial depth. Following the essence of the invention, several such layers can be arranged one behind the other.

For the common domestic refrigerators, it is sufficient in this embodiment to use for the condenser only one line, which is preferably bent three-dimensional meandering. Such a condenser is particularly easy to manufacture and ensures a sufficiently good heat exchange between refrigerant and ambient air. However, arrangements are also conceivable for specific applications, which consist of a plurality of separate lines, possibly spaced apart from one another, or of lines arranged in a plurality of superimposed layers.

It can also be used lines by means of compounds such. As sleeves, are composed. For reasons of cost, lines designed in this way can be useful if length-standardized cable lengths can be used as a result.

Both for the variant with and for the variant without headers, to achieve on the one hand large surfaces for heat transfer and on the other hand to avoid larger pressure drops due to small flow cross sections, line cross-sectional areas of 3 to 30 mm ² chosen, with the hydraulic diameter of the channels in the range of 0.1 to 3 mm. A particularly cost-effective embodiment of the condenser is achieved when an extruded profile tube is used for the lines. In order to further improve the heat transfer properties, a rib structure may be applied to the outside of the profile tube.

To be able to connect the line in a simple manner to the household refrigerating appliance, it is inventively provided that it has molded connections at the inlet and outlet of the refrigerant, wherein at the outlet advantageously a filter dryer can be integrated.

The pipes are usually made of aluminum, since aluminum has a good thermal conductivity, is inexpensive and can be bent well. By providing the pipes with a coating which has a high emission coefficient, an increase in the heat output by thermal radiation to the ambient air is achieved.

In accordance with the essence of the invention, compact condensers for forced convection refrigerating appliances could also be produced from extruded profile tubes which are bent in such a way that several layers are arranged one behind the other in the flow direction, whereby line sections one behind the other are staggered relative to one another.

Due to the staggered arrangement, an increase in efficiency of up to 10% could be achieved even with forced convection. It is also advantageous that a better use of space is made possible by the arrangement in several layers compared to the conventional single-layer arrangements.

The invention will be explained in more detail with reference to two embodiments of condensers for refrigeration appliances with free convection. this is shown in a schematic representation:

1 shows a cross section of the line of the condenser,

2: a condenser with headers in a side view, 3: a condenser with headers in plan view,

Fig. 4: a condenser (without manifolds) with three-dimensional meandering curved line.

The line 1 according to FIG. 1 consists of extruded aluminum profile tubes, with a width of 2.54 cm and a thickness of 2.1 mm. The sides 5 of the profile tubes 1 are rounded, z. B. with a radius of 1 mm. To improve the heat transfer properties, profiles 1 are covered with black lacquer. The profiles 1 are standardized and therefore inexpensive.

The line 1 has thirteen channels 3, 4, which serve for the passage of the refrigerant 2. The channels 3 have a square cross section with rounded corners, wherein the edge length is approximately 1, 5 mm. The two outer channels 4 are approximately rectangular, but the outwardly facing side is rounded. The channels 4 are in Example 1, 5 mm long and 0.5 mm wide.

As can be seen from Fig. 2, in the condenser with collecting tubes 9, these are connected by a plurality of pairs of lines 1 arranged in parallel one above the other, the pairs each extending on a horizontal plane and being spaced apart by the spacers 8 (see Fig. 3). The arranged on adjacent levels pairs of lines 1 are each offset in the flow direction to each other (not shown).

With the condenser with headers can virtually no pressure loss affecting the efficiency occur because on each level 26 channels 2 are parallel and thus a very large flow area for the refrigerant is provided.

In the condenser without manifolds (see Fig. 4), the line 1 is three-dimensional meandering bent. The bending radii are approx. 1, 5 cm. The parallel lines 1 each have a distance of about 3 to 8 cm, that is, they are relatively dense arranged (see Fig. 4). Due to the large number of parallel fenden channels a large flow cross-section for the refrigerant is provided so that even with a large length of the line 1, the pressure loss of the refrigerant is kept low.

Again, each of the line sections, which form superimposed turns of the meander, offset in the flow direction to each other. The condenser is particularly simple and inexpensive to produce, since no welding of components is necessary.

In both embodiments, a large surface of the condenser is achieved by the flat, band-like shape of the lines 1 and their dense, parallel or meandering arrangement. Due to the staggered arrangement of the profile tubes 1 takes place on the long sides of all profiles, each a restart of the air flow. As a result, the insulating, laminar boundary layer is kept thin there and ensures effective heat transfer.

The surface of the condenser can be further increased with the same tube length by profile tubes 1 are used with rib structure.

Due to the closely spaced channels 3, 4 and the good thermal conductivity of the aluminum, the entire surface of the condenser is set in the operation of the refrigerator in a very short time at the same temperature.

The condensers are simple and inexpensive to produce, since the extruded aluminum profile tubes cost standard components are used. The cleaning of the condenser is easily possible, whereby their constancy of performance can be ensured.

Both versions of the condenser achieve up to 15% higher heat output than conventional condenser with the same area. On the other hand, with equal heat output, the area of the condenser could be reduced by about 15%. List of reference numbers used

1st line / profile tube

2nd refrigerant

3. internal channel

4. external channel

5th rounded side

6th entry

7. Exit

8. Spacers

9. collecting pipe

Claims

Palentansprüche

1. Condenser for refrigerators with free correction, in particular Haushaltskäl- tegeräte, having at least one line for the refrigerant, characterized in that the line (1) is formed like a strip, their width is at least twice their thickness, they at least two separate In the intended use, it runs upright and largely nearly parallel to the lower edge of the refrigeration appliance, wherein the upper edge of the preceding one to the lower edge of the subsequent line section is arranged in succession in the flow direction of the same or different lines offset parallel in the flow direction.

2. Condenser according to claim 1, characterized in that said collecting pipes (9) at the inlet and outlet (6, 7), which connected with the intended use edgewise and each other in the vertical parallel lines (1) for the refrigerant are, wherein the lines (1) extend either straight or horizontally wavy or meandering curved.

3. Condenser according to claim 2, characterized in that a plurality of lines (1) are arranged horizontally spaced apart.

4. Condenser according to claim 2 and 3, characterized in that in each case two lines (1) lie in a horizontal plane and are mutually parallel spaced.

5. Condenser according to claim 2 to 4, characterized in that between the lines (1) spacers (8) are mounted with a large surface, which serve as secondary heat exchanger surfaces.

6. Condenser according to claim 1, characterized in that the line for the refrigerant in at least one flat-shaped layer spirally, helical, helical, helical or three-dimensional curved meandering.

7. Condenser according to claim 1 to 6, characterized in that the line sections (1) are arranged offset in the flow direction.

8. Condenser according to claim 1 to 7, characterized in that the line sections are tilted at an angle between 0 and 45 °.

9. Condenser according to claim 1 to 8, characterized in that the conduit (1) has a cross-sectional area of 3 to 30 mm ² .

10. Condenser according to claim 1 to 9, characterized in that the channels (3,4) have hydraulic diameters of 0.1 to 3 mm.

11. Condenser according to claim 1 to 10, characterized in that the line (1) is an extruded aluminum profile tube.

12. Condenser according to claim 1 to 11, characterized in that the line (1) is provided with a coating, for example a black paint, which has a high emission coefficient for thermal radiation.

13. Condenser according to claim 1 to 12, characterized in that the line (1) on the outside of a surface enlargement, for example, a rib structure having.

14. Condenser according to claim 1 to 13, characterized in that the line (1) at the inlet and outlet (6, 7) of the refrigerant has molded connections.

15. Condenser according to claim 1 to 14, characterized in that in the connection piece of the refrigerant outlet, a filter dryer is integrated.

For this 2 sheets of drawings