CN214065351U

CN214065351U - Thermoelectric cooling unit for refrigerator and refrigerator with thermoelectric cooling unit

Info

Publication number: CN214065351U
Application number: CN202021341024.0U
Authority: CN
Inventors: 安东·伦德奎斯特; 约瑟夫·纳吉
Original assignee: Dometic Sweden AB
Current assignee: Dometic Sweden AB
Priority date: 2019-07-10
Filing date: 2020-07-09
Publication date: 2021-08-27
Anticipated expiration: 2030-07-09
Also published as: DE102019210190B4; DE102019210190A1

Abstract

The invention relates to a thermoelectric cooling unit for a refrigerator, comprising a peltier element having a cold side and a hot side during operation. The cold side of the peltier element is destined to be in thermal communication with the interior of the refrigerator and the hot side of the peltier element is destined to be in thermal communication with the environment. The thermoelectric cooling unit further comprises a heat sink thermally coupled to the cold side of the peltier element for increasing the heat exchange with the interior of the refrigerator. The thermoelectric cooling unit further comprises a boiler and a heat pipe thermally coupled to the hot side of the peltier element for increasing the heat exchange with the environment. The boiler is connected to the hot side of the peltier element. The boiler has a discharge port and a return port. The heat pipe connects the discharge port and the return port, thereby forming a closed loop. The present invention further provides a refrigerator equipped with the thermoelectric cooling unit of the present invention.

Description

Thermoelectric cooling unit for refrigerator and refrigerator with thermoelectric cooling unit

Technical Field

The present invention relates to a thermoelectric cooling unit for a refrigerator, such as, for example, a micro-refrigerator, and to a refrigerator having such a thermoelectric cooling unit.

Background

Refrigerators are generally equipped with a compressor type cooling unit. Wherein the refrigerant circuit travels from the inside to the outside of the refrigerator and returns again, thereby dissipating heat energy from the inside to the outside of the refrigerator. The corresponding working principle is well known and compressor type cooling units have several drawbacks. Since the refrigerant circuit also passes through the inside of the refrigerator and the refrigerant evaporates therein, damage to the evaporator may occur (particularly during defrosting of the evaporator), and the refrigerant may leak to the inside of the refrigerator. In addition, the compressor produces noise that can be disturbing, especially in hotel rooms equipped with refrigerators in the form of micro-refrigerators.

Another cooling method is based on the thermoelectric effect, or more specifically the Peltier effect. The peltier effect is based on the contact of two semiconductors having different conduction band energy levels (p-type or n-type conduction). If current is conducted through two successive contact points of these materials, thermal energy must be absorbed at one contact point so that electrons can reach the higher energy conduction band of the adjacent semiconductor material, resulting in cooling. At the other contact point, the electrons drop from a higher energy level to a lower energy level, so that energy is released here in the form of heat.

Since n-doped semiconductors have a lower conduction band energy level, cooling occurs at the point where electrons are transferred from the n-doped semiconductor to the p-doped semiconductor (the technical current flow from the p-doped semiconductor to the n-doped semiconductor).

Peltier elements are essentially composed of two or more small blocks each made of p-doped and n-doped semiconductor material (e.g. bismuth telluride and silicon germanium), which are alternately connected at the top and bottom by metal bridges. The metal bridges also form thermal contact surfaces and are electrically insulated by the overlying foil or ceramic plate. Two different cuboids are always connected to each other in such a way that they form a series connection. The supplied current flows through all the cuboids one by one. Depending on the strength and direction at hand, the upper connection will cool down, while the lower connection heats up. Thus, the current pumps heat from one side to the other and creates a temperature difference between the two plates.

A common form of peltier element comprises two generally square plates made of alumina ceramic with edges of length 20mm to 90mm and a distance of 3mm to 5mm, between which the semiconductor block is welded. For this purpose, the ceramic surfaces are provided with weldable metal surfaces on their facing surfaces.

If the hot side is cooled, for example by means of a radiator with a fan, the cold side becomes colder. Depending on the element and the current, the temperature difference between the two sides may be up to about 70 kelvin.

However, cooling the hot side with a fan again involves the generation of noise-generating electrically powered components. In addition, dirt and dust may accumulate through the ventilation, which is also undesirable.

Disclosure of Invention

The present invention relates to this subject and aims to provide a cooling unit for refrigerators, such as for example micro-refrigerators, which does not have the above-mentioned drawbacks.

To solve this problem, the invention provides a thermoelectric cooling unit for a refrigerator having a peltier element having a cold side and a hot side during operation. The cold side of the peltier element is designated for heat exchange with the interior of the refrigerator. The hot side of the peltier element is designated for heat exchange with the environment. The thermoelectric cooling unit further comprises a heat sink thermally coupled to the cold side of the peltier element for increasing the heat exchange with the interior of the refrigerator.

According to the invention, the thermoelectric cooling unit further has a boiler and a heat pipe. The boiler and the heat pipe are thermally coupled to a hot side of the peltier element for increasing heat exchange with the environment, wherein the boiler is connected to the hot side of the peltier element. The boiler has a discharge port and a return port. The heat pipe connects the discharge port and the return port, thereby forming a closed loop.

A central aspect of the invention therefore relates to cooling the hot side of a peltier element using the heat pipe principle, which is thus known for providing efficient heat conductors.

The working principle of the invention is that the liquid refrigerant inside the boiler starts to boil due to the thermal energy provided by the hot side of the peltier element. The refrigerant evaporates and the vapor or vapor passes through the heat pipe, condenses within the heat pipe again into a liquid thereby dissipating thermal energy into the environment, and flows back into the boiler.

Thus, the boiler and heat pipe together represent a form of heat sink coupled to the hot side of the peltier element.

However, as mentioned above, the heat sink arranged at the cold side of the peltier element works in reverse. Thus, in the strict meaning of the term "heat sink", the "heat sink" used in the framework of the present invention represents a heat sink for the interior of the refrigerator, which conducts heat from the interior of the refrigerator to the cold side of the peltier element.

Also within the framework of the invention, the expression "during operation" refers to the situation in which the refrigerator is working as intended.

Further, whenever the "installation state" of the thermoelectric cooling unit is mentioned, this means a state in which the thermoelectric cooling unit is easily installed to the refrigerator and the refrigerator is ready for use.

In the framework of the present invention, the term "refrigerator" also includes freezers, in addition to any kind of refrigerator or micro-refrigerator.

Terms referring to orientation of, for example, component parts (such as "top," "bottom," "upward," "downward," "vertical," "horizontal," and the like) are with respect to the ground, unless another specific reference is explicitly made in the corresponding context.

In a preferred embodiment of the thermoelectric cooling unit according to the invention, the heat pipe is one single continuous pipe without any branches. This results in fewer parts and thus in less production and assembly costs. In addition, high efficiency can be ensured since any unforeseen effects on the vapor convection within two or more parallel tubes are eliminated.

According to a preferred aspect of the invention, the heat pipe is provided with a plurality of wires on its outside. This improves the efficiency of condensing and cooling the refrigerant within the heat pipe.

According to a further preferred aspect of the invention, in the mounted state, the discharge port is located at the top side of the boiler and the heat pipe is directed away from the discharge port and upwards. This takes advantage of gravity as the hot steam rises and this promotes the flow of steam in the circuit.

According to a further preferred aspect of the invention, the heat pipe extends at least partially in a serpentine manner. Thus, a long heat pipe requiring little space can be realized.

According to a further preferred aspect of the invention, the return port is located at the bottom side of the boiler in the mounted state, and the heat pipe is directed away from the return port and downwards. This takes advantage of gravity as the condensed and cold liquid with the highest density enters the boiler from below and this promotes the flow of refrigerant within the circuit.

According to a further preferred aspect of the invention, the heat pipe extends mainly in one plane or at least two parallel planes. In particular, the serpentine section of the heat pipe is disposed primarily within the plane(s). This arrangement is space-saving.

According to a further, more preferred aspect of the invention, in the mounted state, the heat pipe is arranged vertically with one plane or at least two parallel planes extending mainly within it. This makes the entire refrigerator compact.

According to another preferred aspect of the invention, the boiler has a first side wall, at least a part of which is in contact with the peltier element, and the boiler is designed such that in the mounted state and when filled with liquid refrigerant, the liquid refrigerant inside the boiler covers the entire part of the first side wall which is in contact with the peltier element. In this context, the term "filled" does not necessarily mean that the boiler is completely filled, but that the boiler may be only partially filled with refrigerant. When the liquid refrigerant covers the inner surface of the first sidewall at least in a region where the opposite outer surface of the first sidewall is in contact with the hot side of the peltier element, the cooling efficiency of the hot side of the peltier element is increased. The terms "inside" and "outside" refer to the inside and outside of the boiler, respectively.

According to a further more preferred aspect of the invention, the boiler is designed such that the boiler can only be partially filled with liquid refrigerant. This ensures that there is a layer of gas above the liquid level inside the boiler, which prevents the liquid from hitting the heat pipes during boiling.

In a particularly preferred embodiment, the boiler is a cuboid, and in the mounted state both the peltier element and the first side wall are mainly flat and arranged in a plane inclined from a vertical plane by 1 ° to 3 ° such that the peltier element and the first side wall are inclined at the top towards the refrigerator. In this configuration, the area of the first side wall in contact with the hot side of the peltier element is completely covered by liquid refrigerant, and boiling refrigerant and vapor bubbles can flow upwards and away from the first side wall along the inclined upper side of the boiler to the vapor zone above the liquid level where the discharge port is located. This configuration provides efficient convection of the liquid refrigerant inside the boiler.

According to a further preferred aspect of the invention, the heat sink is at least partially plate-shaped and is in contact with the peltier element at one side of the plate-shape. This provides a higher heat sink surface, increasing the heat conduction from the interior of the refrigerator to the cold side of the peltier element. The material of the heat sink is not particularly limited, and may be a metal having high thermal conductivity as in known heat sinks.

According to a further preferred aspect of the present invention, the thermoelectric cooling unit further comprises a fixing means for fixing the boiler to the heat sink so as to sandwich the peltier element between the boiler and the heat sink. This represents an easy and stable assembly and provides an efficient transfer of thermal energy from the heat sink to the heat pipe.

According to a further preferred aspect of the invention, there are at least four fixing means which are arranged around the peltier element in a top view on the section of the plate-like shape in contact with the peltier element. This is particularly advantageous for square shaped peltier elements. Thus, one securing element is located near each corner of the peltier element. Due to the temperature difference between the hot and cold sides of the peltier element, the whole component is bent, so that the cold side will be concave and the hot side will be convex. By means of the four fixing means at the corners of the peltier element, the peltier element is pushed back to a plane, thereby ensuring contact and heat transfer over the entire surface of the peltier element.

According to a further preferred aspect of the invention, the fixing means are hooks which protrude from the side of the boiler, pass through holes in the radiator and hook at the other side of the radiator. This provides for a simple installation and a reliable connection.

According to a further preferred aspect of the present invention, the thermoelectric cooling unit further includes a housing portion for housing the peltier element and preventing the peltier element from moving along a surface of the plate-like shape of the heat sink, which is in contact with the peltier element. In principle, the receiving section comprises a wall section laterally enclosing the peltier element. This increases the stability of the assembly. Preferably, the receiving portion or the wall portions have a suitable recess or groove for providing a cable connection to the peltier element.

According to a further preferred aspect of the invention, the fixing means and the receiving portion are integrated with the boiler, which is mainly made of plastic material. Thus, the boiler is a one-piece component and requires no additional mounting parts (such as screws or brackets) to be mounted to the heat sink and to clamp and accommodate the peltier elements between the heat sink and the boiler. This reduces the assembly effort and the manufacturing cost.

According to a further preferred aspect of the invention, the boiler has a first side wall, at least a part of which is in contact with the peltier element, and the boiler comprises an aluminum plate as the first side wall, such that during operation only the aluminum plate is between the hot side of the peltier element and the refrigerant. Thus, the one-piece plastic part for the boiler is open at the side where the peltier element should be located. In this region, the aluminum plate is instead present. The aluminum plate provides a more efficient and effective cooling of the hot side of the peltier elements. The term "aluminum plate" is not intended to limit the material of the aluminum plate to pure aluminum. Instead, the person skilled in the art will understand that a number of suitable materials may be selected for this purpose, most of which possibly contain a large amount of aluminium, which is all the reason why the respective plate is referred to as an aluminium plate. Thus, any material suitable for use as an aluminum plate is included in the term "aluminum plate".

According to a further preferred aspect of the invention, the aluminium plate is already integrated into the boiler during the plastic moulding process. This provides a reliable and leak-proof connection between the single-piece plastic boiler and the aluminum plate. For example, in gas-assisted injection molding, an aluminum plate may already be inserted into the molding tool.

According to a further preferred aspect of the invention, the boiler is held in place by the fixing means and the housing in which the receiving portion is integrated. The housing preferably comprises wall portions at least partially closing the boiler at all sides. Here, "at least partially" means that the wall portion may have a free area where the boiler is exposed, for example at the discharge port, the return port and the ports for auxiliary ducts. In the case of a rectangular parallelepiped boiler, the wall portions forming the housing are preferably present at all six sides. The separation of the boiler function and the fixing function achieved by means of the casing has several advantages. First, the boiler is exposed to less mechanical stress. The boiler can be made of different materials like a simple rectangular parallelepiped steel plate. The housing can be designed with only a fixed purpose in mind, which leads to more efficient and effective results.

According to a further preferred aspect of the invention, the accommodation portion at the housing is represented by an open area in the housing, in which open area the peltier element is fitted. In a preferred embodiment, the first side wall is covered only in its edge region by a wall portion of the housing. However, in the central region of the first side wall, the boiler is exposed by the open region. This provides for reliably holding the peltier elements in place while the boiler is closed.

According to a further preferred aspect of the invention, in the region of the open area, the material thickness of the housing is smaller than the thickness of the peltier element. That is, the wall portion of the housing covering the edge of the first side wall is thinner than the peltier element. This ensures direct contact between the heat sink and the peltier element on the one hand and the peltier element and the first side wall of the boiler on the other hand.

According to a further preferred aspect of the invention, the boiler has a first side wall, at least a portion of which is in contact with the peltier element, and the housing comprises a pressing device located in the vicinity of a second side wall of the boiler opposite to the first side wall. By means of the pressing means, the second side wall of the boiler and the corresponding wall portion of the housing are pushed apart, and as the housing is fixed to the heat sink by means of the fixing means, the boiler as a whole is pushed and pressed onto the peltier element, and the peltier element is pushed and pressed onto the heat sink. This represents a simple and efficient configuration in terms of stability and heat transfer.

According to a further preferred aspect of the invention, the pressing means comprise a screw or bolt passing through the casing and acting on the centre of the second side wall of the boiler so as to push the boiler with the first side wall onto the peltier element. Thus, the boiler can be easily pushed from outside the housing to the peltier element by simply driving the screw or bolt. Preferably, the screw can be driven through a threaded hole in the housing and as a result the tip of the screw exerts a corresponding force on the second side wall of the boiler.

According to another aspect of the invention, a refrigerator with a thermoelectric cooling unit according to the invention is provided, wherein, during operation, the cold side of the peltier element is in heat exchange with the interior of the refrigerator via the heat sink and the hot side of the peltier element is in heat exchange with the environment via the boiler and the heat pipe, and wherein the boiler is filled with a liquid refrigerant. The beneficial effects of this solution have been outlined above.

According to a preferred aspect of the present invention, the boiler has a first sidewall, at least a portion of which is in contact with the peltier element, and the liquid refrigerant inside the boiler covers the entire portion of the first sidewall in contact with the peltier element.

According to a further preferred aspect of the invention, the boiler is only partially filled with the liquid refrigerant.

According to a further preferred aspect of the invention, the boiler is a cuboid, and both the peltier element and the first side wall are mainly flat and arranged in a plane inclined from a vertical plane by 1 ° to 3 °, so that the peltier element and the first side wall are inclined at the top towards the refrigerator.

Drawings

Embodiments of the invention will be described in more detail hereinafter with reference to the accompanying drawings, in which

FIG. 1 shows a side view of an embodiment of a thermoelectric cooling unit;

FIG. 2 shows an enlarged perspective view of the thermoelectric cooling unit of FIG. 1;

FIG. 3 shows a vertical and lengthwise cross-sectional view through the thermoelectric cooling unit of FIG. 1;

FIG. 4 shows a vertical and lengthwise cross-sectional view through a refrigerator equipped with the thermoelectric cooling unit of FIG. 1;

FIG. 5 shows a perspective view of the thermoelectric cooling unit of FIG. 1 without wires;

FIG. 6 shows a perspective view of the boiler and Peltier elements of the thermoelectric cooling unit of FIG. 1;

FIG. 7 shows an exploded view of the boiler and Peltier elements of the thermoelectric cooling unit of FIG. 1;

FIG. 8 shows another perspective view of the boiler of the thermoelectric cooling unit of FIG. 1;

FIG. 9 shows an exploded view of the thermoelectric cooling unit of FIG. 1;

FIG. 10 shows a perspective view of another embodiment of a boiler of a thermoelectric cooling unit;

FIG. 11 shows the boiler of FIG. 10 in another perspective view;

FIG. 12 shows a perspective view of the interior of the boiler of FIG. 10, an

Fig. 13 shows an embodiment of a heat sink.

Detailed Description

A first embodiment of the present invention is described with reference to fig. 1 to 9. As shown in fig. 1 to 4, the thermoelectric cooling unit 1 is composed of a heat sink 8, a peltier element 9, a boiler 2, and a heat pipe 7.

The heat sink 8 should exist inside the refrigerator 100 or the micro refrigerator and be made of metal or another material having high thermal conductivity. As shown in fig. 6, 7 and 9, the heat sink 8 is in contact with the cold side 9a of the peltier element 9 and supplies cold to the cooling chamber 102 of the refrigerator 100. For this reason, the heat sink 8 has a plurality of fins 11 to increase the surface area, which promotes the heat conduction efficiency.

The boiler 2 is directly coupled to the heat sink 8, and the peltier element 9 is interposed between the boiler 2 and the heat sink 8. In particular, the boiler 2 is surrounded by a casing 12, which in turn is substantially constituted by two half-shells 24 and a cover 13. The boiler 2 is further equipped with ports, in particular a discharge port 4 and a return port 5, and with an auxiliary duct 6. The discharge port 4 is located on the top side 2a of the boiler 2. During use of the thermoelectric cooling unit 1, the vapor of the refrigerant is discharged through the discharge conduit 4 and flows upward into the heat pipe 7. The heat pipes 7 are first directed steeply upwards and then step-wise downwards again in a meandering manner. For more efficient heat transfer to the environment, wires 14 are arranged on the heat pipe 7. The vapor of the refrigerant is thus condensed inside the heat pipe 7, flows down the heat pipe 7, and returns to the boiler 2 via the return port 5.

In the shown embodiment of the thermoelectric cooling unit 1, the boiler 2 is made of steel. Regardless of the material of the boiler 2, the boiler 2 is in close contact with the peltier element 9, while at the same time, the peltier element 9 is in close contact with the heat sink 8. All this is achieved by the housing 12 and its fixing means 3. The two half-shells 24 of the housing 12 and the cover 13 are connected to one another by means of cover hooks 15 present at the cover 13, which engage in corresponding undercut portions 16 provided at the half-shells 24. The half shells 24 also engage each other by means of the nose 17 and the groove 18.

As can best be seen from the cross-sectional view shown in fig. 3, the boiler 2 is located inside the housing 12 and is pressed by the pressing means 19 onto the hot side 9b of the peltier element 9. The pressing element 19 comprises a screw 26 which passes through the centre of the cover 13, where a threaded hole 27 is provided. The reaction force of the pressing force pressing the boiler 2 onto the peltier element 9 is transmitted to the heat sink 8 via the cover 13, the half shell 24 and finally via the hook 20. As a result, the peltier element 9 is pressed from both sides only by actuating this one screw 26, and a close contact is ensured for an efficient heat transfer from the peltier element 9 to the heat sink 8 on the one hand and from the peltier element 9 to the boiler 2 on the other hand.

As can best be seen in fig. 1, the curved heat pipe 7 extends in a meandering manner in two parallel planes. The heat sink 8 is also located substantially in a plane, which is however not parallel to the plane of the heat pipe 7. In fact, the plane of the heat pipe 7 is inclined away from the plane of the heat sink 8 by an angle α of 2 °. Now, the thermoelectric cooling unit 1 is mounted on the refrigerator such that the plane of the heat pipe is parallel to the door 101 and the wall of the refrigerator 100 so as to be vertical on a uniform floor. However, the boiler 2, the peltier element 9 and the heat sink 8 are inclined by 2 °. The above-mentioned advantages of this arrangement can be seen in fig. 4, where the liquid level of the refrigerant is indicated. By tilting 2 ° in this case, the liquid refrigerant covers the entire area of the first side wall 2c inside the boiler 2 which is in contact with the hot side 9b of the peltier element. However, in case of further departing from the peltier element 9 in the direction to the second side wall 2d or respectively to the discharge port 4, the space of vapor inside the boiler 2 extends and the distance from the liquid level of the refrigerant to the discharge port increases. This effectively prevents or at least reduces the risk of collision during boiling of the refrigerant.

The serpentine course of the heat pipe 7 is best shown in fig. 5, where the line 14 is not shown. The heat pipe 7 from the discharge port 4 travels first steeply upward and then horizontally stepwise downward. The heat pipes 4 travel alternately in the two parallel planes. When the heat pipes 7 almost reach the liquid level of the boiler 2 again, the winding route is interrupted and the heat pipes 7 run downwards and upwards again into the boiler 2 via the return port 5.

As can be seen from fig. 6, the half shell 24 of the housing 12 has an area in which the boiler 2 is exposed (for example in the area of the

ports

4 and 5 and the auxiliary duct 6). In the region of the first side wall 2c, the housing has an open region 25 which serves as a receiving section 22 for the peltier element 9.

Further in fig. 6, the hook 20 may be identified as a fixation device 3, one at each corner of the open area 25. As mentioned above, this provides for pushing the peltier element back to a plane when the peltier element 9 wants to bend due to thermal gradients during operation. Each two of the hooks 20 point in opposite directions and away from the respective other half-shell 24, in order to simplify the mounting procedure.

As can be seen from fig. 9, the hooks 20 engage with holes 21 in the heat sink 8. The heat sink 8 is planar and uniform at the side to which the boiler is attached to provide efficient heat transfer. At the other side, as can best be seen in fig. 13, the heat sink 8 has a plurality of fins 11 to increase the effective surface area of the heat sink 8 inside the refrigerator 100. The fins are oriented vertically to allow the condensate to be washed.

In fig. 10 to 12, another embodiment of the boiler 2 is shown. This boiler 2 no longer requires a housing, since the fixing means 3 for the peltier elements and the receiving portion 22 are integrated in the boiler 2. In fact, the boiler 2 is made in a single piece from plastic, with the exception of the first side wall 2 c. As the first side wall 2c, an aluminum plate 23 is inserted or more precisely molded into the boiler 2 for providing efficient heat transfer.

In fig. 12, a view of the interior of a one-piece plastic boiler 2 is given. Wherein the return port 5 can be seen on the bottom side of the boiler 2. In this embodiment, incidentally, the auxiliary duct 6 or rather the respective port of the auxiliary duct 6 is at the same side of the boiler 2 as the discharge port 4. Like the aluminum plates 23, the pipe sections of the heat pipes extending from the

respective ports

4 and 5 may also be molded into the boiler 2 by inserting them appropriately into a molding tool.

Reference numerals

1 thermoelectric cooling unit

2 boiler

2a top side of the boiler

2b bottom side of boiler

2c first side wall

2d second side wall

3 fixing device

4 discharge port

5 Return port

6 auxiliary pipeline

7 heat pipe

8 radiator

9 Peltier element

9a cold side

Hot side of 9b

10 Peltier element cable

11 Heat sink

12 outer cover

13 cover

14 lines

15 cover hook

16 undercut portion

17 nose part

18 grooves

19 pressing device

20 hook part

21 holes

22 receiving portion

23 aluminum plate

24 half shell

25 open area

26 screw

27 threaded bore

100 refrigerator

101 door

102 cooling chamber

Angle alpha

Claims

1. Thermoelectric cooling unit (1) for a refrigerator (100) having a peltier element (9) which during operation has a cold side (9a) and a hot side (9b), wherein the cold side (9a) of the peltier element (9) is destined for heat exchange with the interior of the refrigerator (100) and the hot side (9b) of the peltier element (9) is destined for heat exchange with the environment, the thermoelectric cooling unit (1) further comprising a heat sink (8) which is thermally coupled to the cold side (9a) of the peltier element (9) for increasing the heat exchange with the interior of the refrigerator (100),

it is characterized in that the preparation method is characterized in that,

the thermoelectric cooling unit (1) further comprises a boiler (2) and a heat pipe (7) thermally coupled to the hot side (9b) of the peltier element (9) for increasing the heat exchange with the environment, wherein the boiler (2) is connected to the hot side (9b) of the peltier element (9), the boiler (2) has a discharge port (4) and a return port (5), and the heat pipe (7) connects the discharge port (4) and the return port (5) forming a closed loop.

2. Thermoelectric cooling unit (1) for a refrigerator (100) according to claim 1, characterized in that the heat pipe (7) is only a single continuous pipe without branches.

3. Thermoelectric cooling unit (1) for a refrigerator (100) according to claim 1 or 2, characterized in that the heat pipe (7) is equipped with a plurality of wires (14) on its outside.

4. Thermoelectric cooling unit (1) for a refrigerator (100) according to claim 1 or 2, characterized in that in the mounted state the discharge port (4) is located at the top side (2a) of the boiler (2) and the heat pipe (7) is directed away from the discharge port (4) and upwards.

5. Thermoelectric cooling unit (1) for a refrigerator (100) according to claim 1 or 2, characterized in that the heat pipe (7) extends at least partially in a meandering manner.

6. Thermoelectric cooling unit (1) for a refrigerator (100) according to claim 1 or 2, characterized in that in the mounted state the return port (5) is located at the bottom side (2b) of the boiler (2) and the heat pipe (7) is directed downwards and away from the return port (5).

7. Thermoelectric cooling unit (1) for a refrigerator (100) according to claim 1 or 2, characterized in that the heat pipe (7) extends mainly in one plane or at least two parallel planes.

8. Thermoelectric cooling unit (1) for a refrigerator (100) according to claim 7, characterized in that in mounted state the heat pipe (7) is arranged vertically with one plane or at least two parallel planes extending mainly within it.

9. Thermoelectric cooling unit (1) for a refrigerator (100) according to claim 1 or 2, characterized in that the boiler (2) has a first side wall (2c) at least a part of which is in contact with the peltier element (9), and the boiler (2) is designed such that in the mounted state and when filled with liquid refrigerant, the liquid refrigerant inside the boiler (2) covers the entire part of the first side wall (2c) which is in contact with the peltier element (9).

10. Thermoelectric cooling unit (1) for a refrigerator (100) according to claim 9, characterized in that the boiler (2) is designed such that the boiler (2) can only be partially filled with the liquid refrigerant.

11. Thermoelectric cooling unit (1) for a refrigerator (100) according to claim 10, characterized in that the boiler (2) is a cuboid and in mounted state both the peltier element (9) and the first side wall (2c) are mainly flat and arranged in a plane inclined from a vertical plane by 1 ° to 3 ° so that the peltier element (9) and the first side wall (2c) are inclined at the top towards the refrigerator (100).

12. Thermoelectric cooling unit (1) for a refrigerator (100) according to claim 1 or 2, characterized in that the heat sink (8) is at least partially plate-shaped and is in contact with the peltier element (9) at one side of the plate-shaped form.

13. Thermoelectric cooling unit (1) for a refrigerator (100) according to claim 12, characterized in that the thermoelectric cooling unit (1) further comprises fixing means (3) for fixing the boiler (2) to the heat sink (8) so as to clamp the peltier element (9) between the boiler (2) and the heat sink (8).

14. Thermoelectric cooling unit (1) for a refrigerator (100) according to claim 13, characterized in that there are at least four fixing means (3) arranged around the peltier element (9) in a top view on the section of plate-like shape in contact with the peltier element (9).

15. Thermoelectric cooling unit (1) for a refrigerator (100) according to claim 13 or 14, characterized in that the fixing means (3) are hooks (20) protruding from the sides of the boiler (2), passing through holes (21) in the heat sink (8) and hooking at the other side of the heat sink (8).

16. The thermoelectric cooling unit (1) for a refrigerator (100) according to claim 12, characterized in that the thermoelectric cooling unit (1) further comprises a receiving portion (22) for receiving the peltier element (9) and preventing the peltier element (9) from moving along the surface of the plate-like shape of the heat sink in contact with the peltier element (9).

17. Thermoelectric cooling unit (1) for a refrigerator (100) according to claim 13 or 16, characterized in that the fixing means (3) and the housing portion (22) are integrated with the boiler (2) mainly made of plastic material.

18. Thermoelectric cooling unit (1) for a refrigerator (100) according to claim 17, characterized in that the boiler (2) has a first side wall (2c) at least a part of which is in contact with the peltier element (9) and that the boiler (2) comprises an aluminum plate (23) as the first side wall (2c) such that during operation only the aluminum plate (23) is between the hot side (9b) of the peltier element (9) and the refrigerant.

19. Thermoelectric cooling unit (1) for a refrigerator (100) according to claim 18, characterized in that the aluminum plate (23) has been incorporated into the boiler (2) during said plastic molding process.

20. Thermoelectric cooling unit (1) for a refrigerator (100) according to claim 13 or 16, characterized in that the boiler (2) is held in place by a housing (12) in which the fixing means (3) and the receiving portion (22) are integrated.

21. Thermoelectric cooling unit (1) for a refrigerator (100) according to claim 20, characterized in that the accommodation portion (22) at the housing (12) is represented by an open area (25) in the housing (12) in which the peltier element (9) is fitted.

22. Thermoelectric cooling unit (1) for a refrigerator (100) according to claim 21, characterized in that in the region of the open area (25) the material thickness of the housing (12) is smaller than the thickness of the peltier element (9).

23. Thermoelectric cooling unit (1) for a refrigerator (100) according to claim 22, characterized in that the boiler (2) has a first side wall (2c) at least a portion of which is in contact with the peltier element (9) and in that the casing (12) comprises a pressing means (19) located in the vicinity of a second side wall (2d) of the boiler (2) opposite to the first side wall (2 c).

24. Thermoelectric cooling unit (1) for a refrigerator (100) according to claim 23, characterized in that the pressing means (19) comprise a screw (26) or bolt passing through the casing (12) and acting on the center of the second side wall (2d) of the boiler (2) in order to push the boiler (2) with the first side wall (2c) onto the peltier element (9).

25. A refrigerator (100) with a thermoelectric cooling unit (1) for a refrigerator (100) according to any of the preceding claims, characterized in that during operation the cold side (9a) of the peltier element (9) is in heat exchange with the interior of the refrigerator (100) via the heat sink (8) and the hot side (9b) of the peltier element (9) is in heat exchange with the environment via the boiler (2) and the heat pipe (7), and wherein the boiler (2) is filled with liquid refrigerant.

26. A refrigerator (100) according to claim 25, characterized in that the boiler (2) has a first side wall (2c) at least a part of which is in contact with the peltier element (9), and the liquid refrigerant inside the boiler (2) covers the whole part of the first side wall (2c) in contact with the peltier element (9).

27. A refrigerator (100) as in claim 26, characterized by the boiler (2) being only partially filled with the liquid refrigerant.

28. A refrigerator (100) according to claim 27, characterized in that the boiler (2) is a cuboid and both the peltier element (9) and the first side wall (2c) are mainly flat and arranged in a plane inclined from a vertical plane by 1 ° to 3 ° so that the peltier element (9) and the first side wall (2c) are inclined at the top towards the refrigerator (100).