EP3230664A1

EP3230664A1 - No-frost refrigeration appliance

Info

Publication number: EP3230664A1
Application number: EP15801445.6A
Authority: EP
Inventors: Niels Liengaard; Matthias Mrzyglod
Original assignee: BSH Hausgeraete GmbH
Current assignee: BSH Hausgeraete GmbH
Priority date: 2014-12-08
Filing date: 2015-11-27
Publication date: 2017-10-18
Anticipated expiration: 2035-11-27
Also published as: EP3230664B1; DE102014225102A1; CN107003058A; WO2016091621A1

Abstract

A refrigeration appliance includes a storage compartment (3) surrounded by a thermal insulation layer (2) as well as a refrigeration machine comprising an evaporator (5), which cools the storage compartment (3), and a compressor (8) which allows refrigerant to circulate through the evaporator (5). A thermosiphon (14) is in thermal contact with the evaporator (5) and to a heat reservoir outside the thermal insulation layer (2).

Description

No-frost refrigerating appliance

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

Since the evaporator always forms the coldest point in the storage chamber of a refrigeration device, moisture that is emitted by the refrigerated goods or that enters the storage chamber when opening a door with the ambient air, settles on the evaporator. The ice layer thus formed obstructs the heat exchange between the evaporator and the remaining storage chamber and must therefore be eliminated from time to time to ensure energy-efficient operation of the refrigeration device.

Most conventional no-frost refrigerators have an electric heater attached to the evaporator for this purpose. Although this solution is simple and inexpensive to manufacture, but it affects the energy efficiency of the refrigerator, since on the one hand a large amount of heating energy must be expended to thaw the ice, and on the other after defrosting the evaporator and its surroundings back to operating temperature must be cooled. If the distribution of the heating power is not precisely matched to the distribution of the ice, the first defrosted areas of the evaporator are heated by the heater useless far beyond the freezing point, which additionally affects the energy efficiency.

One known technique that allows defrosting with better energy efficiency is hot gas defrosting. In this technology, adiabatically heated refrigerant is fed directly into the evaporator in the compressor, without first giving off its heat via a condenser and without being expanded at a throttle point. The improved energy efficiency results from the fact that the refrigerant, which is fed warm into the evaporator, preferably condenses at its coldest point. When the evaporator is partially defrosted, the heat is primarily in the still iced areas, and the heating of the already ice-free areas remains low. However, the heat introduced by the refrigerant into the evaporator stems primarily from the compression work performed in the compressor and from the waste heat of the compressor Compressor forth and must therefore be supplied to the refrigerator in the form of electrical energy as in the electric defrost heater.

The object of the invention is to provide a refrigeration device that allows an even more energy efficient defrost.

The object is achieved by having a thermosyphon in thermal contact with the evaporator and with a refrigeration device with a thermal barrier layer surrounded by a storage chamber and a refrigerator, which comprises a storage chamber cooling evaporator and a circulation of refrigerant through the evaporator driving compressor Heat reservoir is outside the thermal barrier coating. Using the thermosyphon, a large amount of heat can be transported to the evaporator in a short time, which is taken from the heat reservoir and therefore does not affect the energy balance of the refrigerator. A passage, hereinafter referred to as a first passage, between an inner portion in thermal contact with the evaporator and an outer portion of the thermosyphon in thermal contact with the heat reservoir should be closable by a valve to allow heat transfer to the evaporator outside of the defrost phases of the thermosyphon To suppress the refrigerator.

A control unit should be provided to estimate an amount of ice accumulated on the evaporator and to open the valve when the estimated amount of ice exceeds a threshold. Such control units are known per se, but conventionally are usually used to switch an electric defrost heater instead of the valve. The heat output which the thermosyphon can supply to the evaporator is highly dependent on the temperature of the heat reservoir, so that the duration of a defrosting operation may vary. Therefore, to end a defrost operation, the control unit should be connected to a temperature sensor at the inner portion of the thermosyphon or to the evaporator and configured to close the valve when the temperature sensed by the temperature sensor exceeds a threshold.

Preferably, the first passage extends from a lower end of the inner portion downwardly to the outer portion. So can a heat transfer medium, which during the Defrosting condenses in the inner area of the thermosyphon and collects at the lower end of the inner area, gravity driven to reach the outer area and re-evaporate there.

Preferably, a second passage is further provided between the inner and outer regions, so that heat transfer steam can return from the outer region via another passage into the inner region than that through which the liquid heat carrier flows. Thus, the flows between inner and outer areas do not interfere with each other, and it can be achieved a high heat transport performance, without a forced circulation of the heat carrier is needed.

The second passage should extend at least in sections from the outer area down to the inner area. Thus, when the first passage through the valve is shut off and the inner portion is significantly colder than the outer, a stable temperature stratification in the passage can be achieved which minimizes heat input into the bearing chamber through the second passage.

In order to achieve efficient heat transfer to the ice layer on the evaporator, the inner region of the thermosyphon preferably comprises a heat carrier line which runs through the evaporator itself.

If the evaporator is a finned evaporator, such a heat carrier line - in the same way as usually a refrigerant line - cross the fins of the finned evaporator. If the evaporator is a plate evaporator, a refrigerant line and the heat carrier line can run side by side on this.

Further, the evaporator may comprise a multi-channel tube, wherein one channel of the multi-channel tube refrigerant of the refrigerator and another channel leads the heat transfer of the thermosyphon.

According to a preferred development, the heat reservoir outside the thermal barrier coating is a condenser of the refrigerator. When the chiller was in operation immediately before the start of the defrosting process, the condenser is significantly warmer than the more distant environment, and its high temperature allows rapid heat transfer to the evaporator. After defrosting, the condenser is generally colder than the more remote environment, which in turn improves the efficiency of the chiller as it resumes its operation after defrosting.

It is particularly advantageous if the chiller comprises a second evaporator for cooling a second storage chamber, which can be acted upon by the compressor with refrigerant while the valve is open. Thus, the cooling, which undergoes the condenser by the defrosting of the evaporator of the first storage chamber, are made directly available for cooling the second storage chamber again.

Analogous to the above-described construction of the inner region of the thermosyphon, the outer region of the thermosyphon can here comprise a heat carrier line which runs through the liquefier.

The invention also provides a method for defrosting an evaporator in a refrigeration appliance, in which the heat required for the evaporator is supplied via a thermosyphon.

Further features and advantages of the invention will become apparent from the following description of embodiments with reference to the accompanying figures. 1 shows a block diagram of a refrigeration device according to the invention;

Fig. 2 shows schematically the arrangement of inner and outer regions of the

Thermosiphons on a wall of the refrigerator; 3 shows a fragment of a plate heat exchanger for use in the refrigerator according to the invention.

Fig. 4 is a fragment of a wire tube heat exchanger; 5 shows a fin heat exchanger; and

Fig. 6 is a fragment of a heat exchanger with a multi-channel tube. Fig. 1 is a schematic representation of the refrigerator according to the invention. In a body 1, each surrounded by a thermal barrier coating 2, two compartments, here a freezer compartment 3 and a normal refrigeration compartment 4, recessed. Evaporators 5, 6 of the two compartments 3, 4 are connected via a common suction line 7 with a compressor 8. At an output of the compressor 8, a condenser 9 is connected. 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 evaporator 5 is permanently below 0 ° C, so that it can form an ice layer on this. A thermosyphon 14 for defrosting this ice sheet comprises an inner area 15 inside the freezer compartment 3 and an outer area 16 outside the thermal barrier coating layer 2. The inner area 15 is formed by a heat carrier line 17 passing through the evaporator 5; the outer region 16 forms a heat carrier line 18 in the condenser 9. The outer region 16 is at least partially deeper than the inner region 15, so that in the evaporator 5 condensed refrigerant, which converges at a lowest point 19 of the heat carrier 17 in the evaporator 5, from there driven solely by gravity can flow through a first passage 20 through the thermal barrier coating 2 to the condenser 9, provided that a arranged in the first passage 20 valve 21 is open.

A second passage 22, which leads from the outer region 16 through the thermal barrier coating 2 back to the inner region 15, is constantly open, but since this second passage 22 connects to a highest point 23 of the heat carrier 17, no liquid heat carrier from the inner Area 15 to reach the outer region 16. The thermosyphon 14 allows heat transfer to the evaporator 5 only as long as the valve 21 is open. To control the valve 21 is an electronic control unit 24 which is designed to various forms known per se, such as the duration of the compressor 8 since the last defrosting, the frequency of door openings of the freezer compartment 3 since the last defrosting, etc., the amount of ice on Estimate evaporator 5 and open the valve 21 as soon as the estimated amount of ice exceeds a threshold.

A temperature sensor 25 is mounted adjacent to the lowest point 19 on the evaporator 5. As soon as the temperature detected by this temperature sensor 25 rises above 0 ° C. in the course of a defrosting operation, 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 schematically a section through the thermal barrier coating 2 of the refrigerator with the arranged on the side of the freezer compartment 3 evaporator 5 and exposed on the outside condenser 9. The passage 20 is over its entire length to the outer region 16 of the heat siphon 14, the condenser 9, sloping, so that heat transfer medium, which condenses in the inner region 15, can flow automatically to the outer region 16 when the valve 21 is open. When the valve 21 is closed, condensed heat carrier may accumulate in the inner region 15 and in the passage 20 above the valve 21, but does not enter the outer region 16. In the case of the second passage 22, it suffices if only a part of it to the inner region 15 downhill, so that in this part with a closed valve 21, a temperature gradient can form, which prevents any exchange of heat transfer between the areas 15, 16 via the passage 22.

As is indicated in FIG. 2, the inner and outer regions 15, 16 of the heat siphon 14 may be in the form of hollow plates which are in intimate thermal contact with the evaporator 5 or the liquefier 9 on one of their main surfaces. However, preference is given to a structure in which the regions 15, 16 of the heat siphon each form integral components of the evaporator 5 and the liquefier 9, respectively. A first example of such a construction is shown in FIG. 3 using the example of a rollbond heat exchanger. On a base plate 26 are side by side tubes of the Heat transfer line 17 and a line 27 laid for the recirculated by the compressor 8 refrigerant.

A corresponding arrangement of the heat carrier line 17 and refrigerant line 27 is shown in FIG. 4, but the lines 17, 27 together with wires 28 connecting them 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 finned evaporator. The refrigerant pipe 27 forms in known manner an upper and a lower layer 29, 30 of the blades 31 perpendicular crossing, extending in the viewing direction of the viewer rectilinear sections 34, which alternately on the side facing the viewer of the evaporator or, dashed represented, on the side facing away from him protruding sheets 32 are connected. Another over the blades 31 projecting arc 33 establishes a series connection between the two layers 29, 30 ago. The heat carrier line 17 also forms an upper and a lower layer 35, 36, but they are, unlike the layers 29, 30, exactly in a plane so that they are continuously sloping along its entire length. Thus, liquid heat transfer medium, no matter at which point of the layers 35, 36 it forms, flow freely into the heat transfer line 17 to the lowest point 19 of the evaporator 5 and from there to the outer region 16 of the heat siphon 14.

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

1 corpus

2 thermal barrier coating

3 freezer

4 normal refrigerated compartment

5 evaporators

6 evaporator

7 suction line

8 compressors

9 liquefier

10 line

1 1 way valve

12 capillaries

13 capillaries

14 thermosiphon

15 inner area

16 outer area

17 heat carrier line

18 heat carrier line

19 lowest point

20 passage

21 valve

22 passage

23 highest point

24 control unit

25 temperature sensor

26 base plate

27 line

28 wire

29 upper position

30 lower layer

31 lamella 32 sheets

33 sheets

34 section

35 upper layer

36 lower layer 37 multi-channel tube

38 main surface

39 main surface

40 channel

Claims

Refrigerating appliance having a storage chamber (3) surrounded by a thermal barrier coating (2) and a refrigerating machine comprising an evaporator (5) cooling the storage chamber (3) and a compressor (8) driving the circulation of refrigerant through the evaporator (5) by a thermosyphon (14) which is in thermal contact with the evaporator (5) and with a heat reservoir outside the thermal barrier coating (2).

Refrigerating appliance according to claim 1, characterized in that a first passage (20) between an inner region (15) which is in thermal contact with the evaporator (5) and an outer region (16) of the thermosyphon (14) in thermal contact with the heat reservoir ) by a valve (21) can be shut off.

Refrigeration appliance according to claim 2, characterized in that a control unit (24) is arranged to estimate an amount of ice accumulated on the evaporator and to open the valve (21) when the estimated amount of ice exceeds a threshold value.

Refrigerating appliance according to claim 3, characterized in that the control unit (24) is connected to a temperature sensor (25) on the inner region (15) of the thermosyphon (14) or on the evaporator (5) and is arranged to close the valve (21), when the temperature detected by the temperature sensor (25) exceeds a threshold.

Refrigerating appliance according to one of claims 2 to 4, characterized in that the first passage (20) extends from a lower end of the inner region (15) down to the outer region (16).

Refrigerating appliance according to one of claims 2 to 5, characterized by a second passage (22) between the inner and outer region (15, 16).

Refrigerating appliance according to claim 6, characterized in that the second passage (22) extends from the outer region (16) to the inner region (15) at least in sections downwards.

Refrigerating appliance according to one of claims 1 to 7, characterized in that the inner region (15) of the thermosyphon (14) comprises a heat carrier line (17) which extends through the evaporator (5).

Refrigerating appliance according to claim 8, characterized in that the evaporator (5) is a finned evaporator and the heat carrier line (17) crosses the fins (31) of the finned evaporator.

Refrigerating appliance according to claim 8, characterized in that the evaporator is a plate evaporator, in which a refrigerant line (27) and the heat carrier line (17) on a base plate (26) extend side by side.

Refrigerating appliance according to claim 8, characterized in that the evaporator (5) comprises a multi-channel tube (37), wherein a channel (40, 27) of the multi-channel tube (37) refrigerant of the refrigerator and another channel (40, 17) a heat carrier of the thermosyphon (14) leads.

Refrigerating appliance according to one of the preceding claims, characterized in that the heat reservoir is a condenser (9) of the refrigerator.

Refrigerating appliance according to claim 12, characterized in that the chiller comprises a second evaporator (6) for cooling a second storage chamber (4) which is acted upon by the compressor (7) with refrigerant, while the valve (21) is open.

14. Refrigerating appliance according to claim 12 or 13, characterized in that the outer region (16) of the thermosyphon (14) comprises a heat transfer line (18) passing through the condenser (9). A method for defrosting an evaporator in a refrigeration device, wherein the heat required for the evaporator (5) via a thermosyphon (14) is supplied.