WO2017212380A1

WO2017212380A1 - Method for operating a household refrigeration device and household refrigeration device

Info

Publication number: WO2017212380A1
Application number: PCT/IB2017/053271
Authority: WO
Inventors: Francisco Javier Aleman Ezcaray; Jose Maria BORDES COSTA; Luis Lecumberri Bruna; Santiago MARTINEZ BALLESTER; Jordi OLCINA LLOPIS
Original assignee: BSH Hausgeräte GmbH
Priority date: 2016-06-09
Filing date: 2017-06-02
Publication date: 2017-12-14
Also published as: ES2646332B1; ES2646332A1

Abstract

The invention relates to a method for operating a household refrigeration device (1), wherein during a first period of time (25) air cooled down by an evaporator (5) of a heat pump (4) of the household refrigeration device (1) is introduced into a refrigeration compartment (2) and into a freezer compartment (3) of the household refrigeration device (1). During a second period of time (26) the air is introduced only into the freezer compartment (3). During the first period of time (25) a compressor (6) of the heat pump (4) is initially operated at a first speed (29). Before the air is introduced into the freezer compartment (3) only, the compressor (6) is operated at a second speed (31) for a predetermined timespan (32) within the first period of time (25), wherein the second speed (31) is higher than the first speed (29). The invention further relates to a household refrigeration device (1).

Description

METHOD FOR OPERATING A HOUSEHOLD REFRIGERATION DEVICE AND HOUSEHOLD REFRIGERATION DEVICE

The invention relates to a method for operating a household refrigeration device. Herein, during a first period of time, air cooled down by an evaporator of a cooling circuit, also called heat pump, of the household refrigeration device is introduced into a refrigeration compartment and into a freezer compartment of the household refrigeration device. During a second period of time the air is introduced only into the freezer compartment. The invention further relates to a household refrigeration device. In household refrigerators which are equipped both fresh food cabinet, i.e. a refrigeration compartment, and freezer cabinet, i.e. a freezer compartment, different air temperatures are maintained in both cabinets or compartments. In such a refrigerator an evaporator of a heat pump is located at the freezer compartment. An inlet of a unit comprising the evaporator fluidly communicates with the refrigeration compartment on the one hand and with the freezer compartment on the other hand. During a first period of time the refrigeration device is operated in an operation mode in which the evaporator receives air coming from both the refrigeration compartment and the freezer compartment. In this operation mode the air which has been cooled down by the evaporator is blown into the refrigeration compartment and into the freezer compartment. This operation mode is chosen when the refrigeration compartment needs to be cooled down.

When the refrigeration compartment does not need to be cooled down, a damper is closed. This prevents the air which has been cooled down by the evaporator from entering the refrigeration compartment. Consequently, the air having passed through the evaporator is blown only into the freezer compartment. In this operation mode the inlet of the unit comprising the evaporator is only provided with return air which is coming from the freezer. The first operation mode with opened damper is also known as FD mode, and the second operation mode, in which the damper is closed, is also called FZ mode. In the FD mode the air which is provided to the inlet of the evaporator comes from the refrigeration compartment and from the freezer compartment. Therefore the return air is much warmer in the FD mode than in the FZ mode. When the operation changes from the FD mode to the FZ mode, a transient occurs in the refrigerant conditions. The negative effects of these transient phenomena on the energy consumption of the household refrigeration device have been extensively studied and described. One of the phenomena is called the refrigerant migration. The refrigerant migration consists in a change of the refrigerant mass distribution within the heat pump system, i.e. the refrigerant mass located in each component of the heat pump. For each operating condition the refrigerant has a certain distribution within the circuit of the heat pump. Also, for each condition there is an optimum distribution. When there is a change from one operating mode to another operating mode, a transient process occurs, in which the refrigerant is moving or migrating, and another mass distribution is achieved. Until steady conditions are reached in the new operation mode, the heat pump is not operating in optimal conditions. This leads to an increase in energy consumption compared to a system in which the refrigerant could migrate instantaneously to achieve the new, optimum mass distribution of the refrigerant. The increase in energy consumption during the refrigerant migration in the transition from the FD mode to the FZ mode leads to an overall increase of the energy consumption of the household refrigeration device.

It is therefore the object of the present invention to provide a method of the initially mentioned kind which allows for energy savings and to provide a corresponding household refrigeration device.

This object is solved by a method and by a household refrigeration device having the features of the respective independent claims. Advantageous configurations with convenient further developments of the invention are specified in the dependent claims.

In the method according to the invention for operating a household refrigeration device, air cooled down by an evaporator of a heat pump of the household refrigeration device is introduced into a refrigeration compartment and simultaneously into a freezer compartment of the household refrigeration device during a first period of time. During a second period of time, the air is introduced only into the freezer compartment. During the first period of time, a compressor of the heat pump is initially operated at a first speed. Before the air is introduced into the freezer compartment only, the compressor is operated at a second speed for a predetermined timespan which lies within the first period of time. Herein, the second speed is higher than the first speed. In other words the compressor speed is increased during the predetermined timespan before the operation mode changes mode from the FD mode to the FZ mode. This increase of the compressor speed reduces the energy losses which are due to the refrigerant migration caused by the transition of the operation mode in the first period of time to the operation mode in the second period of time, which follows the first period of time. Therefore, the method allows for energy savings, and the energy efficiency of the household refrigeration device is improved.

The speed of the compressor is increased before the change in the operation mode takes place, i.e. before the air cooled down by the evaporator is blown or introduced into the freezer compartment only and no longer both into the refrigeration compartment and into the freezer compartment. The increase in the speed of the compressor reduces the time during which the system or the heat pump is operating in transient conditions, wherein the transient conditions are due to the change of the operating conditions.

The invention is based on the finding that the conditions, in particular the air inlet temperatures at the evaporator, are very different from each other in the first period of time, i.e. in the FD mode, and in the second period of time, i.e. in the FZ mode. Due to this temperature difference at the inlet of the unit containing the evaporator, the heat pump or refrigerant system suffers a transient process in which the refrigerant is not operating in the designed conditions. The transition of the heat pump operation from a first status with steady conditions to a second status with steady conditions leads to an efficiency loss of the heat pump. This efficiency loss depends on the system design and can range from 2% to 20%.

Due to the increase of the compressor speed to the second speed for the predetermined timespan the length of time is reduced, in which the system or heat pump is operating in less efficient conditions. Therefore, the efficiency loss is less severe. A decrease of the energy consumption of the household refrigeration device of up to 4% can be achieved by the method which comprises the increase of the compressor speed to the second speed during the predetermined timespan. Thus, the global energy efficiency of the appliance or household refrigeration device can be improved. This method requires a different configuration of a control unit of the household refrigeration device which operates both the heat pump and means for preventing the cooled air from entering the refrigeration compartment. However, no new components need to be added. Therefore, energy savings can be obtained in a particularly cost-effective way.

Preferably, the compressor is operated at the second speed immediately before the air is introduced only into the freezer compartment. By such an operation the time during which refrigerant migration takes place can be reduced to a particularly large extent.

Preferably, a temperature within the refrigeration compartment is measured by means of at least one temperature sensor. Herein, the compressor starts to be operated at the second speed, when the temperature within the refrigeration compartment reaches a predetermined value. This allows for a particularly easy operation of the heat pump as only one temperature reading can be utilized to control the speed of the compressor. The temperature value at which the compressor starts to be operated at the second speed, can be experimentally determined, for example as the value which optimizes the energy efficiency of the heat pump at a certain value of the second speed.

A length of the predetermined timespan, during which the compressor is operated at the second speed, can be between 2 minutes and 10 minutes, in particular between 3 minutes and 5 minutes. Thus, the predetermined timespan is significantly shorter than the rest of the first period of time. Further, such a short timespan only marginally increases the energy consumption of the compressor while leading to an overall decrease of the energy loss due to the refrigerant migration at the transition from the first period of time to the second period of time. Preferably, a length of the predetermined timespan is set in dependence on a mass of a refrigerant within the heat pump. In other words the refrigerant charge has an influence on the length of the timespan. This is based on the finding that a larger amount or mass of refrigerant within the heat pump requires more time to reach a new, in particular optimum refrigerant distribution compared to a heat pump or system containing a lower mass of the refrigerant.

The length of the predetermined timespan can also be set in dependence on a value of the second speed. Herein, a higher second speed can lead to a quicker establishment of the desired mass distribution of the refrigerant within the system than a lower second speed. Alternatively or additionally, the length of the predetermined timespan can be set in dependence on a design parameter of at least one heat exchanger of the heat pump. In particular, the type of the evaporator and a condenser of the heat pump have an influence on the establishment of the optimum mass distribution of the refrigerant within the heat pump. Therefore, taking into account such design parameters allows for setting an optimum length of the predetermined timespan in order to increase the overall energy efficiency of the household refrigeration device. Preferably, a value of the second speed is set in dependence on a mass of a refrigerant within the heat pump. For example, the higher second speed of the compressor can lead to a quicker re-distribution the refrigerant within the heat pump, if the overall amount or mass of the refrigerant within the heat pump is lower.

Alternatively or additionally, at least one design parameter of at least one heat exchanger of the heat pump can be taken into consideration to set the value of the second speed. Depending on the type of the evaporator and the condenser arranged within the heat pump, a higher second speed or a lower second speed can be beneficial to achieve the desired re-distribution of the refrigerant within the heat pump.

Alternatively or additionally, the value of the second speed can be set in dependence on at least one design parameter of the compressor. This is due to the finding that an efficiency of the compressor in compressing the refrigerant can be different for different speeds of the compressor. Therefore, by taking into account such parameters, the value of the second speed can be set particularly well in order to reduce the energy losses due to refrigerant migration which is due to the transition from the first operation mode (FD mode) in the first period of time to the second operation mode (FZ mode) in the second period of time. Preferably, during the second period of time the compressor is operated at a third speed which is different from the first speed. Further, the third speed can be different from the second speed. For example, the third speed can be higher than the first speed but lower than the second speed. In such a configuration, the higher third speed of the compressor during the second period of time allows for an improved cooling performance as the air coming from the evaporator is circulated through the freezer compartment only. However, if the third speed is lower than the second speed, the energy consumption of the compressor is lower than in a configuration in which the third speed does not differ from the second speed.

Preferably, the second speed at which the compressor is operated during the predetermined timespan is more than 10 %, in particular more than 25 %, higher than the first speed. In particular, the second speed can be more than 50 % higher than the first speed. Such considerable increases of the compressor speed provide for a particularly good reduction of the energy loss due to the refrigerant migration caused by the transition from the operation mode during the first period of time to the operation mode during the second period of time. This is in particular true, if a length of the predetermined timespan is less than 50 %, in particular less than 25 %, of a total length of the first period of time. Preferably, during the second period of time, the air cooled down by the evaporator is prevented from entering the refrigeration compartment by closing a first outlet of an air duct. Herein the air leaves the air duct through a second outlet which leads to the freezer compartment. Such a configuration is particularly reliable in preventing the air from entering the refrigeration compartment during the second period of time.

The household refrigeration device according to the invention comprises at least one refrigeration compartment and at least one freezer compartment. An evaporator of a heat pump of the household refrigeration device is arranged in a space within the freezer compartment. A control unit of the household refrigeration device is configured to operate the heat pump such that during a first period of time air cooled down by the evaporator is introduced into the refrigeration compartment and into the freezer compartment. The control unit is further configured to operate the heat pump such that during a second period of time the air is introduced only into the freezer compartment. Herein, the control unit is configured to operate a compressor of the heat pump initially at a first speed during the first period of time and to operate the compressor at a second speed for a predetermined timespan within the first period of time, before the air is introduced into the freezer compartment only. Herein, the second speed is higher than the first speed. The advantages and preferred embodiments described with respect to the method according to the invention correspondingly apply to the household refrigeration device according to the invention and vice versa.

The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of figures and/or shown in the figures alone are usable not only in the respectively specified combination, but also in other combinations or alone, without departing from the scope of the invention. Thus, implementations are also to be considered as encompassed and disclosed by the invention, which are not explicitly shown in the figures or explained, but arise from and can be generated by separated feature combinations from the explained implementations. Therefore also embodiments and feature combinations shall be considered as disclosed, which do not have all the features of an originally formulated independent claim.

Further advantages, features and details of the invention are apparent from the claims, the following description of preferred embodiments as well as based on the drawings in which features having analogous functions are designated with the same reference signs. Therein show:

Fig. 1 schematically a household refrigeration device with a no-frost evaporator and a variable speed compressor, wherein the evaporator is arranged in a freezer compartment of the refrigeration device, and wherein the refrigeration device also comprises a refrigeration compartment;

Fig. 2 a graph in which curves represent the compressor speed during different operation modes of a heat pump of the refrigeration device shown in fig. 1 ; and

Fig. 3 a graph showing the corresponding temperature within the refrigeration compartment of the refrigeration device as a function of the time.

The indications "upper", "lower", "top", "front", "bottom", "floor", "horizontal", "vertical", "depth direction", "width direction", "height direction" and the like refer to the positions and orientations of the device in its intended use position with respect to an observer located in front of the device and regarding towards the device. A household refrigeration device 1 is schematically shown in a front view in fig. 1. The household refrigeration device 1 represented in fig. 1 is a combination of a refrigerator and a freezer. Accordingly, the refrigeration device 1 comprises a refrigeration compartment 2 and a freezer compartment 3. A first door and a second door which are configured to close the refrigeration compartment 2 and the freezer compartment 3, respectively, are not shown in fig. 1. In fig. 1 the refrigeration compartment 2 is shown above the freezer compartment 3. However, the refrigeration compartment 2 can also be below the freezer compartment 3, or the freezer compartment 3 can be located side by side with or within the refrigeration compartment 2.

The refrigeration device 1 comprises a heat pump 4 of which an evaporator 5, a compressor 6, a condenser 7 and an expansion device 8 are very schematically shown in fig. 1. In a manner known as such, the heat pump 4 comprises conducts or pipes (not shown) connecting the evaporator 5 with the compressor 6, the compressor 6 with the condenser 7, the condenser 7 with the expansion device 8 and the expansion device 8 with the evaporator 5. The heat pump 4 contains a refrigerant.

A control unit 9 of the refrigeration device 1 operates the compressor 6 in order to vary a speed of a rotating element of the compressor 6 which leads to the compression of the refrigerant circulating through the heat pump 4. The control unit 9 receives temperature values from a first temperature sensor 1 1 located within the refrigeration compartment 2 and from a second temperature sensor 10 located within the freezer compartment 3. The respective locations of the control unit 9, the compressor 6, the condenser 7, the expansion device 8 and the temperature sensors 10, 1 1 are only schematically in fig. 1. Accordingly, all these components can be arranged at appropriate locations of the refrigeration device 1. However, a unit comprising the evaporator 5 is located in a space within the freezer compartment 3. The evaporator 5 is configured as a no-frost evaporator. Herein, ice which forms on cooling fins of the evaporator 5 is thawed from time to time, and the water thus formed is evacuated from the freezer compartment 3.

A fan 12 provides air to be cooled down by the evaporator 5 to an inlet 13 of the unit comprising the evaporator 5. The air then passes through the evaporator 5 and is therefore cooled down. The fan 12 blows this cooled and dried air into an air duct 14 located downstream of the evaporator 5. In the air duct 14, the cooled down air, which is represented by an arrow 15 in fig. 1 is split into a first airflow 16 which is blown into the refrigeration compartment 2 and a second airflow 17 which is blown into the freezer compartment 3. This operation mode, in which the fan 12 is blowing the air into both compartments 2, 3 through the duct 14 is also called an FD mode, because in the FD mode a damper 18 is open. By closing the damper 18 a first outlet 19 of the air duct 14 is closed, and the air is prevented from entering the refrigeration compartment 2. Thus, the way to the refrigeration compartment 2 is closed by the damper 18, in particular in a situation in which the refrigeration compartment 2 does not need to get colder.

When the damper 18 is opened as shown in fig. 1 , the air goes into both compartments 2, 3 in the FD mode. In this case, the airflows 16, 17 are recirculated to the inlet 13 of the evaporator 5 after the air has cooled down the refrigeration compartment 2 and the freezer compartment 3. Corresponding return channels are indicated in fig. 1 by further arrows 20, 21. In the FD mode the air which is coming from the refrigeration compartment 2 can have a temperature between +2°C and +8°C, for example of about +5°C. The air coming from the freezer compartment 3 can have a temperature between -18°C and -22°C, for example of about -20°C. The corresponding return airflows are mixed at the inlet 13 of the evaporator 5.

When the damper 18 is closed, the air is blown into the freezer compartment 3 only. In this case, the air cooled down by the evaporator 5 leaves the air duct 14 through a second outlet 22. In this operation mode, which is also called FZ mode, the recirculated air or return air which arrives at the inlet 13 of the evaporator 5 comes only from the freezer compartment 3. Therefore, the return air is much warmer in the FD mode than in the FZ mode. This difference in temperature affects the evaporation temperature of the refrigerant circulating through the heat pump 4 and the performance of the heat pump 4.

Fig. 2 shows the speed of compressor 6 in the FD mode and the FZ mode of the refrigeration device 1 , respectively. The speed of the compressor 6 is shown on an ordinate 23 as a function of the time which is shown on an abscissa 24. In the FD mode the air is blown into the refrigeration compartment 2 and the freezer compartment 3 during a first period of time 25. During a subsequent second period of time 26, the household refrigeraton device 1 is operated in the FZ mode in which the damper 18 is closed. This means that the air cooled down by the evaporator 5 is only introduced into the freezer compartment 3. After these two periods of time 25, 26, the speed of the compressor 6 is reduced to a value of zero during an off time 27. With other words, the compressor 6 is turned off during the off time 27.

At a transition from the first period of time 25 to the second period of time 26, i.e. at a transition from the FD mode to the FZ mode, a change of operating conditions of the heat pump 4 occurs. This change in the operation mode includes a transient in the refrigerant conditions. These transient phenomena have a negative effect on the energy consumption of the household refrigeration device 1. One of the phenomena is the refrigerant migration, i.e. the refrigerant mass distribution within the heat pump 4. Each operating condition of the refrigerant within the circuit of the heat pump 4 goes along with a certain distribution of the refrigerant within the heat pump 4. When the system changes the operation mode, the system suffers the transient process in which the refrigerant is moving to achieve another mass distribution. Once steady conditions are achieved again, the refrigerant distribution is the optimal one (if the heat pump 4 is designed correctly). However, as long as the heat pump 4 is not in optimal conditions, i.e. as long as the refrigerant mass distribution does not correspond to the optimal mass distribution for a given speed of the compressor 6, the heat pump 4 consumes more energy compared to a system in which the refrigerant could migrate instantaneously to achieve steady conditions.

In fig. 2 a curve 28 illustrates the operation of the compressor 6 for a conventional refrigeration device. Herein, the compressor 6 is operated throughout the whole first period of time 25 at a constant first speed 29. Subsequently, during the second period of time 26, the compressor 6 is operated at another constant speed 30, which is higher than the first speed 29. In order to reduce the impact of the refrigerant migration, the time during which this phenomenon takes place is reduced. This is achieved by increasing the speed of the compressor 6 immediately before the second period of time 26 starts. Herein, the compressor 6 is operated at a second speed 31 which is higher than the first speed 29 during a predetermined timespan 32. The timespan 32 is a last part of the first period of time 25. By increasing the speed of the compressor 6 during this certain timespan 32 or amount of time before changing from the FD operation mode to the FZ operation mode, the energy losses due to refrigerant migration can be reduced. In this way the time during which the efficiency of the refrigeration device 1 is being penalized is reduced. The length of the timespan 32 or the amount of time during which the compressor 6 is operated at the second speed 31 depends on the model of the refrigeration device 1 , wherein important factors are the refrigerant charge, the speed 31 and the types of heat exchangers, i.e. the types of the evaporator 5 and the condenser 7. However, a length of the timespan 32 is preferably about 3 to 5 minutes. During the first period of time 25, i.e. in the FD mode, the compressor 6 is initially operated at the first speed 29 and then at the second speed 31 which is higher than the first speed 29. At the end of the timespan 32, i.e. at the beginning of the second period of time 26, during which the refrigeration device 1 is operated in the FZ mode, the compressor 6 is operated at the third speed 30.

A curve 33 illustrated as a dashed line in fig. 2 shows the modification that electronics within the control unit 9 introduce compared to a conventional appliance. Accordingly, at a time 34 before changing form the FD mode to the FZ mode, the speed of the compressor 6 is increased up to the second speed 31. In the example illustrated in fig. 2, the second speed 31 is higher than the first speed 29 and higher than the third speed 30. Also, the third speed 30 is higher than the first speed 29. However, the same concept of increasing the speed of the compressor 6 during the timespan 32 before the start of the second period of time 26 is also applicable if the speeds 29, 30 of the compressor 6 are the same in the FD mode and the FZ mode. The third speed 30 can also be the same as the second speed 31 , or the third speed 30 can be higher than the second speed 31. The value of the second speed 31 also depends on the appliance model, i.e. the design parameters of the refrigeration device 1. In particular, the refrigerant charge, the type of heat exchangers and also the compressor 6 efficiency for each speed are taken into account when setting the value of the second speed 31.

In fig. 3 a temperature measured by the temperature sensor 1 1 located within the refrigeration compartment 2 is indicated on an ordinate 35, while the time is indicated on the abscissa 24. The temperature within the refrigeration compartment 2 is indicated by a curve 36 in fig. 3. Accordingly, during the first period of time 25, i.e. in the FD mode, the temperature within the refrigeration compartment 2 decreases. When the temperature in the refrigeration compartment 2 reaches a lower threshold 37, the damper 18 is closed and the refrigeration device 1 is operated in the FZ mode during the second period of time 26. Accordingly, the temperature within the refrigeration compartment 2 rises. When the temperature reaches an upper threshold 38 upon elapse of the off time 27, the damper 18 is opened again and the compressor 6 is again operated at the first speed 29.

The time 34 at which the compressor 6 starts to be operated at the second speed 31 is determined by the electronics of the control module 9 based on the readings of the first temperature sensor 1 1 located within the refrigeration compartment 2. The moment or time 34 corresponds to the instant in which the measured temperature reaches a predetermined value 39. This value 39 is preferably determined experimentally. The value 39 can be a temperature reading which leads to an optimization of the energy efficiency of the heat pump 4 when the compressor 6 starts to be operated at the second speed 31 at the time 34 which corresponds to the value 39.

The refrigeration device 1 uses the two temperature sensors 10, 1 1 in the freezer compartment 3 and the refrigeration compartment 2. However, for determining the time 34 at which the first speed 29 is increased to the second speed 31 , only the temperature reading of the temperature sensor 11 within the refrigeration compartment 2 is utilized. Preferably, the speed of the compressor 6 is increased, whenever there is a change in the operation mode. As the refrigeration device 1 normally starts in the FD mode, the next change occurs, when the damper 18 is closed, i.e. at the end of the first period of time 25 and the beginning of the second period of time 26 in which the refrigeration device 1 is operated in the FZ mode. Herein, the compressor speed-up operation at the point or time 34 leads to an improved cooling performance and reductions in energy consumption of the refrigeration device 1.

List of Reference Signs

1 household refrigeration device

2 refrigeration compartment

3 freezer compartment

4 heat pump

5 evaporator

6 compressor

7 condenser

8 expansion device

9 control unit

10 temperature sensor

1 1 temperature sensor

12 fan

13 inlet

14 duct

15 arrow

16 airflow

17 airflow

18 damper

19 first outlet

20 arrow

21 arrow

22 outlet

23 ordinate

24 abscissa

25 first period of time

26 second period of time

27 off time

28 curve

29 first speed

30 speed

31 second speed

32 timespan curve time ordinate curve lower threshold upper threshold value

Claims

1. Method for operating a household refrigeration device (1), wherein during a first period of time (25) air cooled down by an evaporator (5) of a heat pump (4) of the household refrigeration device (1) is introduced into a refrigeration compartment (2) and into a freezer compartment (3) of the household refrigeration device (1), and during a second period of time (26) the air is introduced only into the freezer compartment (2), characterized in that during the first period of time (25) a compressor (6) of the heat pump (4) is initially operated at a first speed (29), and before the air is introduced only into the freezer compartment (3) the compressor (6) is operated at a second speed (31) for a predetermined timespan (32) within the first period of time (25), wherein the second speed (31) is higher than the first speed (29).

2. Method according to claim 1 , characterized in that the compressor (6) is operated at the second speed (31) immediately before the air is introduced only into the freezer compartment (3).

3. Method according to claim 1 or 2, characterized in that a temperature within the refrigeration compartment (2) is measured by means of at least one temperature sensor (1 1), wherein the compressor (6) starts to be operated at the second speed (31), when the temperature within the refrigeration compartment (2) reaches a predetermined value (39).

4. Method according any one of claims 1 to 3, characterized in that a length of the predetermined timespan (32), during which the compressor (6) is operated at the second speed (31), is between 2 minutes and 10 minutes, in particular between 3 minutes and 5 minutes.

5. Method according to any one of claims 1 to 4, characterized in that a length of the predetermined timespan (32) is set in dependence on a mass of a refrigerant within the heat pump (4) and/or a value of the second speed (31) and/or a design parameter of at least one heat exchanger (5, 7) of the heat pump (4).

6. Method according to any one of claims 1 to 5, characterized in that a value of the second speed (31) is set in dependence on a mass of a refrigerant within the heat pump (4) and/or a design parameter of at least one heat exchanger (5, 7) of the heat pump (4) and/or at least one design parameter of the compressor (6).

7. Method according to any one of claims 1 to 6, characterized in that during the second period of time (26) the compressor (6) is operated at a third speed (30) which is different from, in particular higher than, the first speed (29) and/or different from, in particular lower than, the second speed (31).

8. Method according to any one of claims 1 to 7, characterized in that the second speed (31) at which the compressor (6) is operated during the predetermined timespan (32) is more than 10 %, in particular more than 25 %, higher than the first speed (29) and/or a length of the predetermined timespan (32) is less than 50 %, in particular less than 25 %, of a total length of the first period of time (25).

9. Method according to any one of claims 1 to 8, characterized in that during the second period of time (26) the air cooled down by the evaporator (5) is prevented from entering the refrigeration compartment (2) by closing a first outlet (19) of an air duct (14), wherein the air leaves the air duct (14) through a second outlet (22) leading to the freezer compartment (3).

10. Household refrigeration device (1) comprising at least one refrigeration compartment (2) and at least one freezer compartment (3), wherein an evaporator (5) of a heat pump (4) of the household refrigeration device (1) is arranged in a space within the freezer compartment (3), and wherein a control unit (9) of the household refrigeration device (1) is configured to operate the heat pump (4) such that during a first period of time (25) air cooled down by the evaporator (5) is introduced into the refrigeration compartment (2) and into the freezer compartment (3), and during a second period of time (26) the air is introduced only into the freezer compartment (3), characterized in that the control unit (9) is configured to operate a compressor (6) of the heat pump (4) initially at a first speed (29) during the first period of time (25), and to operate the compressor (6) at a second speed (31) for a predetermined timespan (32) within the first period of time (25) before the air is introduced only into the freezer compartment (3), wherein the second speed (31) is higher than the first speed (29).