EP3230664B1 - No-frost refrigerator - Google Patents

Description

The present invention relates to a refrigeration device, in particular a household refrigeration device, with an automatically defrosting evaporator. Such refrigeration devices are also known as "no-frost refrigeration devices".

Since the evaporator always forms the coldest point in the storage chamber of a refrigeration device, moisture that is given off by the refrigerated goods or that enters the storage chamber with the ambient air when a door is opened is deposited on the evaporator. The layer of ice that forms in this way hinders the exchange of heat between the evaporator and the rest of the storage chamber and must therefore be removed from time to time in order to ensure energy-efficient operation of the refrigeration device.

Most conventional no-frost refrigeration devices have an electric heater attached to the evaporator for this purpose. Although this solution is simple and inexpensive to manufacture, it impairs the energy efficiency of the refrigeration device because, on the one hand, a large amount of heating energy has to be used to thaw the ice and, on the other hand, the evaporator and its surroundings return to operating temperature after defrosting need to be cooled down. If the distribution of the heating power is not precisely matched to the distribution of the ice, the areas of the evaporator that are defrosted first are uselessly heated to well above freezing point by the heater, which also impairs energy efficiency.

Out US 2014/0260364 A1 a refrigeration device with a multi-channel coextruded evaporator is known, in which a main channel is provided to carry a refrigerant and a defrosting fluid can circulate between a secondary channel of the evaporator and an external heat source.

CA 894 525 A describes a refrigeration device with a refrigeration machine, the evaporator of which is arranged above the condenser and in which the evaporator and condenser can be connected in a standstill phase of the compressor in such a way that liquid refrigerant flows from the evaporator to the condenser and at the same time refrigerant vapor rises from the condenser to the evaporator. By keeping condensation in the Evaporation and evaporation take place in the condenser, heat is transported from the condenser to the evaporator and the evaporator is defrosted.

The object of the invention is to create a refrigeration device that enables even more energy-efficient defrosting.

The object is achieved by a refrigeration device with the features of claim 1. With the help of the thermosiphon, a large amount of heat can be transported to the evaporator in a short time, which is taken from the condenser serving as a heat reservoir and therefore does not affect the energy balance of the refrigeration device. If the refrigeration machine was still in operation immediately before the start of the defrosting process, the condenser is significantly warmer than the more distant surroundings, and its high temperature enables rapid heat transfer to the evaporator. After the defrosting process, the condenser can be colder than the more distant surroundings, which in turn improves the efficiency of the refrigeration machine when it resumes operation after defrosting. The cooling that the condenser experiences through the defrosting of the evaporator of the first storage chamber can, however, also be made immediately usable again during the defrosting to cool the second storage chamber.

A passage, hereinafter referred to as the first passage, between an inner area in thermal contact with the evaporator and an outer area of the thermosiphon in thermal contact with the heat reservoir should be able to be shut off by a valve in order to prevent heat transfer to the evaporator outside the defrosting phases To suppress refrigeration device.

According to the invention, a control unit is provided in order to estimate an amount of ice that has accumulated on the evaporator and to open the valve if the estimated amount of ice exceeds a limit value. Such control units are known per se, but are conventionally mostly used to switch an electrical defrost heater instead of the valve. The heating power that the thermosiphon can supply to the evaporator is heavily dependent on the temperature of the heat reservoir, so that the duration of a defrosting process can vary. To end a defrosting process, the control unit should therefore be equipped with a temperature sensor on the inner area of the thermosiphon or be connected to the evaporator and set up to close the valve when the temperature detected by the temperature sensor exceeds a limit value.

Preferably, the first passage extends downward from a lower end of the inner region to the outer region. A heat transfer medium that condenses in the inner area of the thermosiphon during defrosting and collects at the lower end of the inner area can reach the outer area driven by gravity and evaporate there again.

A second passage is preferably also provided between the inner and outer area, so that heat carrier vapor can return from the outer area to the inner area via a different passage than the one through which the liquid heat carrier flows. In this way, the flows between the inner and outer areas do not interfere with each other, and a high heat transfer rate can be achieved without the need for forced circulation of the heat transfer medium.

The second passage should run at least in sections from the outer area downwards to the inner area. If the first passage is blocked by the valve and the inner area is considerably colder than the outer area, a stable temperature stratification can be achieved in the passage, which minimizes the flow of heat into the storage chamber via the second passage.

In order to achieve efficient heat transfer to the ice layer on the evaporator, the inner area of the thermosiphon preferably comprises a heat transfer line that runs through the evaporator itself.

If the evaporator is a lamellar evaporator, such a heat transfer line can - in the same way as usually a refrigerant line - cross the lamellar evaporator.

If the evaporator is a plate evaporator, a refrigerant line and the heat transfer line can run next to one another on this.

Furthermore, the evaporator can comprise a multi-channel tube, one channel of the multi-channel tube carrying the refrigerant of the refrigerating machine and another channel carrying the heat transfer medium of the thermosiphon.

Analogous to the structure of the inner area of the thermosiphon described above, the outer area of the thermosiphon can include a heat transfer line that runs through the condenser.

Fig. 1

ein Blockdiagramm eines erfindungsgemäßen Kältegeräts;

Fig. 2

schematisch die Anordnung von inneren und äußeren Bereichen des Thermosiphons an einer Wand des Kältegeräts;

Fig. 3

ein Bruchstück eines Plattenwärmetauschers zur Verwendung in dem erfindungsgemäßen Kältegerät;

Fig. 4

ein Bruchstück eines Drahtrohrwärmetauschers;

Fig. 5

einen Lamellen-Wärmetauscher; und

Fig. 6

ein Bruchstück eines Wärmetauschers mit einem Mehrkanalrohr.

Further features and advantages of the invention emerge from the following description of exemplary embodiments with reference to the accompanying figures. Show it:

Fig. 1

a block diagram of a refrigeration device according to the invention;

Fig. 2

schematically the arrangement of inner and outer areas of the thermosiphon on a wall of the refrigerator;

Fig. 3

a fragment of a plate heat exchanger for use in the refrigeration device according to the invention;

Fig. 4

a fragment of a wire tube heat exchanger;

Fig. 5

a fin heat exchanger; and

Fig. 6

a fragment of a heat exchanger with a multi-channel pipe.

Fig. 1 is a schematic representation of the refrigeration device according to the invention. In a body 1, each surrounded by a thermal insulation layer 2, two compartments, here a freezer compartment 3 and a normal refrigerator compartment 4, are cut out. Evaporators 5, 6 of the two compartments 3, 4 are connected to a compressor 8 via a common suction line 7. A condenser 9 is connected to an output of the compressor 8. A line 10 emanating from the condenser 9 branches off at a directional control valve 11 into two capillaries 12, 13, each of which leads back to one of the evaporators 5, 6.

The temperature of the freezer compartment evaporator 5 is permanently below 0 ° C., so that a layer of ice can form on it. A thermosiphon 14 for defrosting this layer of ice comprises an inner area 15 inside the freezer compartment 3 and an outer area 16 outside the thermal insulation layer 2. The inner area 15 is formed by a heat transfer line 17 which runs through the evaporator 5; the outer region 16 is formed by a heat transfer line 18 in the condenser 9.

The outer area 16 is at least partially lower than the inner area 15, so that refrigerant condensed in the evaporator 5, which converges at a lowest point 19 of the heat transfer line 17 in the evaporator 5, is driven from there solely by gravity via a first passage 20 through the Thermal insulation layer 2 can flow to the condenser 9, provided that a valve 21 arranged in the first passage 20 is open.

A second passage 22, which leads from the outer area 16 through the thermal insulation layer 2 back to the inner area 15, is always open, but since this second passage 22 connects to a highest point 23 of the heat transfer line 17, no liquid heat transfer medium can pass through it from the inside Area 15 to reach outer area 16.

The thermosiphon 14 enables heat to be transported to the evaporator 5 only as long as the valve 21 is open. An electronic control unit 24 is used to control the valve 21, which is designed to measure the amount of ice on the basis of various criteria known per se, such as the running time of the compressor 8 since the last defrosting process, the frequency of door openings in the freezer compartment 3 since the last defrosting process, etc. To estimate the evaporator 5 and to open the valve 21 as soon as the estimated amount of ice exceeds a limit value.

A temperature sensor 25 is attached to the evaporator 5 adjacent to the lowest point 19. As soon as the temperature detected by this temperature sensor 25 rises above 0 ° C. in the course of a defrosting process, it can be assumed that the evaporator 5 is free of ice; then the control unit 24 closes the valve 21 again.

Fig. 2 shows a schematic section through the thermal insulation layer 2 of the refrigeration device with the evaporator 5 arranged on the side of the freezer compartment 3 and the condenser 9 exposed on the outside. The passage 20 slopes down its entire length to the outer area 16 of the heat siphon 14, on the condenser 9 so that heat transfer medium which condenses in the inner area 15 can automatically flow off to the outer area 16 when the valve 21 is open. When the valve 21 is closed, condensed heat transfer medium can accumulate in the inner area 15 and in the passage 20 above the valve 21, but does not get into the outer area 16. In the case of the second passage 22, it is sufficient if only part of it is sloping towards the inner area 15 so that a temperature gradient can form in this part when the valve 21 is closed, which prevents any exchange of heat transfer medium between the areas 15, 16 via the passage 22.

The inner and outer areas 15, 16 of the thermosiphon 14 can, as in FIG Fig. 2 indicated, in the form of hollow plates which are in intimate thermal contact with the evaporator 5 or the condenser 9 on one of their main surfaces. However, a structure is preferred in which the regions 15, 16 of the heat siphon each form integral components of the evaporator 5 and the condenser 9, respectively. A first example of such a structure is shown Fig. 3 using the example of a rollbond heat exchanger. On a base plate 26 tubes are side by side Heat transfer line 17 and a line 27 for the refrigerant circulated by the compressor 8 are laid.

A corresponding arrangement of heat transfer line 17 and refrigerant line 27 is shown Fig. 4 However, the lines 17, 27 together with the wires 28 connecting them here form a wire tube heat exchanger which can be used both as an evaporator 5 and as a condenser 9.

Fig. 5 shows a side view of a fin evaporator. The refrigerant line 27 forms, in a manner known per se, an upper and a lower layer 29, 30 of straight sections 34 which cross the lamellae 31 vertically and run in the direction of view of the viewer and which alternate with one another on the side of the evaporator facing the viewer or, in dashed lines shown, on the side facing away from it protruding arches 32 are connected. Another arch 33 protruding beyond the lamellae 31 establishes a row connection between the two layers 29, 30. The heat transfer line 17 also forms an upper and a lower layer 35, 36, but, unlike the layers 29, 30, these lie exactly in one plane so that they are continuously sloping over their entire length. In this way, liquid heat transfer medium, irrespective of where it forms in layers 35, 36, can flow freely in heat transfer line 17 to the lowest point 19 of evaporator 5 and from there to outer area 16 of heat siphon 14.

Fig. 6 shows a fragment of a heat exchanger formed from multi-channel tube 37. The multi-channel pipe 37, extruded from metal, in particular aluminum, has a band-shaped elongated cross section and can easily be bent in an orientation in which its main surfaces 38, 39 form the outer and inner sides of a bend. The channels 40 of the multi-channel pipe 37 each alternately belong to the heat transfer line 17 and the refrigerant line 27 and thus enable extremely rapid heating of the evaporator during defrosting.

REFERENCE MARK

1

Body

2

Thermal insulation layer

3

freezer

4th

Normal refrigerator compartment

5

Evaporator

6th

Evaporator

7th

Suction line

8th

compressor

9

Condenser

10

management

11

Directional control valve

12th

capillary

13th

capillary

14th

Thermosiphon

15th

inner area

16

outer area

17th

Heat transfer line

18th

Heat transfer line

19th

deepest point

20th

Passage

21

Valve

22nd

Passage

23

the highest point

24

Control unit

25th

Temperature sensor

26th

Base plate

27

management

28

wire

29

upper layer

30th

lower layer

31

Lamella

32

arc

33

arc

34

section

35

upper layer

36

lower layer

37

Multi-channel pipe

38

Main surface

39

Main surface

40

channel

Claims (10)

1. Refrigerator with a first storage chamber (3) surrounded by a thermal insulation layer (2), a refrigerating machine, which comprises an evaporator (5) cooling the first storage chamber (3) and a compressor (8) driving the circulation of refrigerant through the evaporator (5), and a thermosiphon (14), which is in thermal contact with the evaporator (5) and with a heat reservoir outside of the thermal insulation layer (2), wherein a first passage (20) between an inner region (15) in thermal contact with the evaporator (5) and an outer region (16) of the thermosiphon (14) in thermal contact with the heat reservoir can be shut off by a valve (21), characterised in that the heat reservoir is a condenser (9) of the refrigerating machine, wherein the refrigerating machine comprises a second evaporator (6) for cooling a second storage chamber (4), to which refrigerant can be applied by the compressor (7), while the valve (121) is open, and a control unit (24) is designed to measure a quantity of ice collected on the evaporator and to open the valve (21) when the measured quantity of ice exceeds a limit value.
2. Refrigerator according to claim 1, characterised in that the control unit (24) is connected to a temperature sensor (25) on the inner region (15) of the thermosiphon (14) or on the evaporator (5) and is designed to close the valve (21) when the temperature detected by the temperature sensor (25) exceeds a limit value.
3. Refrigerator according to claim 1 or 2, characterised in that the first passage (20) runs from a lower end of the inner region (15) downwards towards the outer region (16).
4. Refrigerator according to one of claims 1 to 3, characterised by a second passage (22) between the inner and outer region (15, 16).
5. Refrigerator according to claim 4, characterised in that the second passage (22) runs at least in sections downwards from the outer region (16) to the inner region (15).
6. Refrigerator according to one of claims 1 to 5, characterised in that the inner region (15) of the thermosiphon (14) comprises a heat carrier line (17) which runs through the evaporator (5).
7. Refrigerator according to claim 6, characterised in that the evaporator (5) is a fin evaporator and the heat carrier line (17) intersects the fins (31) of the fin evaporator.
8. Refrigerator according to claim 6, characterised in that the evaporator is a plate evaporator, in which a refrigerant line (27) and the heat carrier line (17) run adjacent to one another on a base plate (26).
9. Refrigerator according to claim 6, characterised in that the evaporator (5) comprises a multichannel pipe (37), wherein one channel (40, 27) of the multichannel pipe (37) conducts refrigerant of the refrigerating machine and another channel (40, 17) conducts a heat carrier of the thermosiphon (14).
10. Refrigerator according to one of the preceding claims, characterised in that the outer region (16) of the thermosiphon (14) comprises a heat carrier line (18) which runs through the condenser (9).

Images