Refrigeration unit with heating and cooling compartment

Description

[0001] The present invention relates to a refrigeration appliance, in particular a household refrigeration appliance, with at least one storage compartment which can be optionally heated or cooled.

[0002] Such a refrigeration device is known, for example, from DE 10 2016 032 986 A. In this known refrigeration device, heat exchangers of the heatable and coolable compartment and of a first cooled compartment, each with an upstream and a downstream expansion valve, are arranged in parallel pipe lines of the refrigerant circuit, and both lines open onto the evaporator of a second cooled compartment.

[0003] DE 1 0 201 3 226341 A1, WO 03 / 052331 A1, JP 2001 133112 A and WO 2017 / 140494 A1 disclose refrigeration devices with several storage chambers and at least one expansion valve.

[0004] One object of the present invention is therefore to provide a refrigeration device with a heatable and coolable storage compartment that is simpler in design and can therefore be implemented cost-effectively. A further object is to provide an operating method for such a refrigeration device.

[0005] The object is achieved, on the one hand, in a refrigeration appliance, in particular a household refrigeration appliance, having at least a first, a second and a third storage chamber, a refrigerant circuit in which the following are connected in series between a pressure connection and a suction connection of a compressor: a condenser, a first expansion valve, a first heat exchanger of the first storage chamber, a second expansion valve, and a second heat exchanger of the second storage chamber; a third heat exchanger associated with the third storage chamber and a control circuit for controlling the operation of the compressor and the expansion valves, the control circuit being configured to maintain a higher storage temperature in the third storage chamber than in the second storage chamber.

[0006] Although this design still requires two expansion valves to adjust the mass flow through the first heat exchanger and the pressures in the first and second heat exchangers, the temperature of the third storage chamber can be controlled without recourse to expansion valves by allowing only refrigerant vapor or vapor and liquid refrigerant in variable proportions to pass from the second heat exchanger to the third heat exchanger, as required. Overflow of the second heat exchanger does not lead to malfunctions and does not need to be suppressed by control technology; rather, it is part of the normal operation of the refrigeration unit, enabling the supply of liquid refrigerant to the third heat exchanger.

[0007] The speed of the compressor can be adjusted to a variety of values, preferably continuously, so that temporal fluctuations in the temperature in the storage chambers and the additional consumption of electrical energy associated with these fluctuations can be minimized by uninterrupted operation of the compressor.

[0008] The control circuit is configured to increase the speed of the compressor when the temperature of the second storage chamber is above a setpoint and / or to decrease the speed when the temperature of the second storage chamber is below a setpoint. By increasing the compressor speed, the pressure in a suction line leading to the compressor and, via this, also the pressure in the second and third heat exchangers can be reduced. Since the cooling effect of the third heat exchanger is largely not based on the evaporation of liquid refrigerant therein but on vapor flowing through it from the second heat exchanger, the change in speed influences the cooling effect of the third heat exchanger at most slightly; however, the pressure reduction has a direct effect on the evaporation of the refrigerant taking place in the second heat exchanger.

[0009] The connection between the second and third heat exchangers does not require an additional expansion valve; on the contrary, this connection should be as free as possible from throttling points that would hinder the transfer of refrigerant to the third heat exchanger or promote a pressure difference between the second and third heat exchangers.

[0010] Preferably, the smallest free cross-section of a refrigerant line connecting the heat exchangers is essentially the same size, but in any case at least half the size, of an average free cross-section of lines of the heat exchangers.

[0011] The above-mentioned setpoints can be identical; however, they can also define the limits of an interval within which the speed of the evaporator remains unchanged.

[0012] In order to regulate the temperature in the third storage chamber, the control circuit is preferably configured to increase the degree of opening of the first expansion valve when the temperature of the third storage chamber is above a setpoint and / or to decrease the degree of opening of the first expansion valve when the temperature of the third storage chamber is below a setpoint. Although the first expansion valve and the third heat exchanger in the refrigerant circuit are separated in one direction by two heat exchangers and the second expansion valve and in the other by the compressor, adjusting the first expansion valve surprisingly has an effect primarily in the third heat exchanger. Opening the first expansion valve initially reduces the throttling effect of the entire refrigerant circuit.However, the pressure in the second and third heat exchangers changes only slightly, because as this pressure increases, the compressor's throughput also increases at a constant speed. Consequently, the main consequence of opening the first expansion valve is an increased flow of liquid refrigerant through the second expansion valve and, consequently, at the latest after the second heat exchanger is completely filled with liquid refrigerant, an increased supply of liquid refrigerant to the third heat exchanger and thus increased cooling of the third storage chamber.

[0013] The control circuit may also be configured to increase the degree of opening of the second expansion valve when the temperature of the third storage chamber is above a setpoint and / or to decrease the degree of opening of the second expansion valve when the temperature of the third storage chamber is below a setpoint.

[0014] A decision as to which of these two options is to be used is conveniently made by comparing the target temperature of the first storage chamber with the ambient temperature.

[0015] In order to control the temperature of the first storage chamber, the control circuit may be configured to increase the degree of opening of the second expansion valve when the temperature of the first storage chamber is above a setpoint and / or to decrease the degree of opening of the second expansion valve when the temperature of the first storage chamber is below a setpoint.

[0016] Alternatively, the control circuit may be configured to increase the degree of opening of the first expansion valve when the temperature of the first storage chamber is below a setpoint and / or to decrease the degree of opening of the first expansion valve when the temperature of the first storage chamber is above a setpoint.

[0017] Here, too, the choice between the alternatives can be made by comparing the target temperature of the first storage chamber with the ambient temperature.

[0018] A third expansion valve, a fourth heat exchanger of a fourth storage chamber, and a fourth expansion valve can be connected in series and in parallel with the first expansion valve, the first heat exchanger, and the second expansion valve. This allows multiple optionally heated or cooled compartments to be created within the refrigeration unit.

[0019] The temperatures in these compartments can be adjusted independently of each other by adjusting the evaporation pressures using the upstream and downstream expansion valves.

[0020] In a refrigeration appliance with a fourth storage chamber as described above, the degree of opening of the third expansion valve can also be increased if the temperature of the third storage chamber is above a setpoint and / or the degree of opening of the third expansion valve can be reduced if the temperature of the third storage chamber is below a setpoint.

[0021] If desired, additional storage chambers can be provided, each with an associated heat exchanger and the expansion valves upstream and downstream of it in a branch of the refrigerant circuit.

[0022] At least one of the heat exchangers can be assigned a fan to drive the air exchange between the heat exchanger and the storage chamber. Such a fan is advantageous for intensifying heat exchange with the storage chamber and thus achieving high exchange efficiency with a compact heat exchanger. They are not absolutely necessary for controlling the cooling of the various storage chambers. Therefore, in the simplest case, such a fan can be operated at an uncontrolled or fixed speed.

[0023] Particularly when a storage chamber is operated in a cooled state, it can be useful to regulate the speed of the fan based on a predetermined temperature difference between the evaporator and the storage chamber in order to adjust the extent to which the air in the storage chamber is dried by condensation on the evaporator or the humidity content of the air.

[0024] The object is further achieved by a method for operating a refrigeration device as described above, comprising the steps of: increasing the degree of opening of the second expansion valve when the temperature of the first storage chamber is above a setpoint, and / or decreasing the degree of opening of the second expansion valve when the temperature of the first storage chamber is below a setpoint. Increasing the speed of the compressor when the temperature of the second storage chamber is above a setpoint and / or decreasing the speed when the temperature of the second storage chamber is below a setpoint; opening the first expansion valve when the temperature of the third storage chamber is above a setpoint and / or decreasing the opening degree of the first expansion valve when the temperature of the third storage chamber is below a setpoint, and by a computer program product comprising instructions which, when executed on a computer, enable the computer to act as a control circuit in a Refrigeration appliance to operate as described above or to carry out the procedure mentioned above.

[0025] Further features and advantages of the invention will become apparent from the description of exemplary embodiments with reference to the accompanying figures. They show: Fig. 1 is a block diagram of a refrigeration device according to the invention; and Fig. 2 is a flowchart of an operating method of the refrigeration device.

[0026] Fig. 1shows a block diagram of a refrigeration device according to the invention. At least three storage chambers 2, 3, 4 are recessed in a heat-insulating housing 1. Each of these storage chambers 2, 3, 4 is assigned a heat exchanger 5, 6, 7. The assignment can consist, for example, in the heat exchanger being embedded in the manner of a cold-wall evaporator between an inner container of the storage chamber and a layer of insulating material surrounding the inner container, or in the heat exchanger 5, 6, 7 being mounted in the inner container 8 of the respective storage chamber 2, 3, 4. In the latter case, a partition wall 9 can be provided in the inner container, which divides the volume of the inner container into the storage chamber 2, 3, 4 and a heat exchanger chamber 10 accommodating the heat exchanger 5, 6, 7.Regardless of how the heat exchanger 5, 6, 7 is assigned to the storage chamber 2, 3, 4, a fan 11 can be assigned to each heat exchanger 5, 6, 7 to intensify the heat transfer between the storage chamber 2, 3, 4 and its heat exchanger 5, 6, 7. The speed or power of such a fan 11 can be fixed or, as explained in more detail below, controllable.

[0027] Each storage chamber 2, 3, 4 is equipped with a temperature sensor 12. Measured values ​​from the temperature sensors 12 are recorded by a control circuit 13.

[0028] A refrigerant circuit comprises, starting from a pressure connection of a compressor 14, in sequence a condenser 15, a pressure line 16, a first expansion valve 17, the heat exchanger 5, a second expansion valve 18, the second heat exchanger 6, the third heat exchanger 7, and a suction line 19 leading to a suction connection of the compressor 14. The expansion valves 17, 18 are of a known type not described here and are designed to maintain a pressure difference between inlet and outlet predetermined by a control signal. The source of the control signals is the control circuit 13. The pressure line 16 and the suction line 19 run in close contact with one another over part of their length, thus forming an internal heat exchanger 22 in which the compressed refrigerant releases residual heat to the vapor in the suction line 19 shortly before reaching the expansion valve 17.

[0029] The pressure differential adjustable at expansion valve 17 is variable within wide limits. On the one hand, expansion valve 17 allows a pressure to be set in heat exchanger 5 that differs only slightly, if at all, from the pressure at the pressure connection of compressor 14, so that condensation of refrigerant occurs in heat exchanger 5 and condenser 15, allowing storage chamber 2 to be operated at a target temperature above the ambient temperature. Refrigerant condensed in condenser 15 and heat exchanger 5 is fed to heat exchangers 6 and 7 via expansion valve 18. The upper limit of the temperature at which storage chamber 2 can be operated should not be below +18°C.

[0030] Less stringent requirements apply to the expansion valve 18: to enable operation of the storage chamber 3 as a freezer compartment, even when the storage chamber 2 is operated as a normal refrigeration compartment, a non-negligible pressure drop across the expansion valve 18 is necessary. The maximum pressure difference across the expansion valve 18 should be sufficient to enable freezer operation of the storage chamber 3 even when essentially the full output pressure of the compressor 14 is present at the inlet of the expansion valve 18.

[0031] There is no significant pressure drop between heat exchangers 6 and 7. In particular, both heat exchangers 6 and 7 and a connecting line can be made of the same type of pipe with consistent cross-sectional dimensions.

[0032] Target temperatures for all three storage chambers 2, 3, 4 can be set at a user interface 20 of the control circuit 13. If one of the storage chambers 2, 3, 4 has a fan 11, the user interface 20 can also provide the option of selecting a humidity value for the respective storage chamber.

[0033] Fig. 2 shows a flowchart of an operating procedure of the control circuit 13. In step S1, the temperatures T2, T3, T4 in the storage chambers 2, 3, and 4 are measured using the sensors 12. In step S2, the target temperature T2s set by the user for the storage chamber 2 is compared with the ambient temperature T env . If the ambient temperature T env is lower, i.e., if the storage chamber 2 is cooled, the method proceeds to step S3.

[0034] In step S3, the temperature T2 is compared with the target temperature T2s. If both values ​​T2, T2s agree within a predetermined tolerance interval, the method proceeds directly to step S4. If the measured temperature T2 is significantly lower than T2s, the control circuit reduces the degree of opening of the expansion valve 18 (S5) in order to increase the pressure or boiling point of the refrigerant in the heat exchanger 5. Reducing the degree of opening can here consist of increasing the pressure difference between the heat exchangers 5 and 6 that the expansion valve 18 must maintain. Conversely, in step S6, the degree of opening is increased (or the pressure difference is decreased) if the temperature T2 is significantly higher than T2s.

[0035] The extent to which the pressure difference is changed in step S5 or S6 may be a constant, or it may take into account circumstances such as the magnitude of the difference between T2 and T2s or the length of time that the deviation between T2 and T2s has already lasted in order to minimize the time to restore agreement between T2 and T2s or to minimize control overshoot.

[0036] In step S4, the temperature T3 is compared with the target temperature T3s set by the user for the storage chamber 3. The heat exchanger 6 of the storage chamber 3 always operates as an evaporator; for this purpose, it is continuously supplied with liquid refrigerant during operation, which has either condensed in the condenser 15 and only partially evaporated in the heat exchanger 5, or because condensation has occurred in the heat exchanger 5 in addition to that of the condenser. The heat exchanger 6 is therefore the coldest of the heat exchangers 5, 6, and 7 because, like the heat exchanger 7, it essentially experiences the suction pressure of the compressor 14 and is well supplied with liquid refrigerant. T3 and T3s are normally in a range below -10°C, e.g., around -18°C, typical for a freezer compartment.

[0037] If both values ​​T3, T3s agree within a predetermined tolerance interval, the method proceeds directly to step S7. If the measured temperature T3 is significantly lower than T3s, the control circuit 13 reduces the speed of the compressor 14 (S8) in order to increase the pressure or boiling point of the refrigerant in the heat exchanger 6. Conversely, the speed is increased in step S9 if the temperature T3 is significantly higher than T3s.

[0038] The extent to which the speed is changed in step S8 or S9 may be a constant, or it may take into account circumstances such as the amount of difference between T3 and T3s or the length of time that the deviation between T3 and T3s has already lasted in order to minimize the time to restore agreement between T3 and T3s or to minimize control overshoot.

[0039] In step S7, the temperature T4 is compared with the target temperature T4s set by the user for the storage chamber 4. If both values ​​T4, T4s agree within a predetermined tolerance interval, the method returns to step S1 after a predetermined waiting time (S12). If the measured temperature T4 is significantly lower than T4s, the control circuit reduces the degree of opening of the expansion valve 17 (S10) in order to reduce the mass flow of the refrigerant and thus reduce the amount of liquid refrigerant that reaches the heat exchanger 7. Conversely, in step S11, the degree of opening is increased if the temperature T4 is significantly higher than T4s, so that more liquid refrigerant reaches the heat exchanger 7.

[0040] If, however, it is determined in step S2 that heating operation is selected for the storage chamber 2, ie if T2s>T env, then T2 is subsequently also compared with T2s (S3`), but if T2 is significantly below T2s, the expansion valve 17 is opened further (S5`), or if T2 is significantly above T2s, it is closed further (S6`).

[0041] The steps S4, S8, S9 for temperature control in the storage chamber 3 are identical to those described above for the case of cooling operation in the storage chamber 2.

[0042] The temperature T4 in the storage chamber 4 is then controlled via the expansion valve 18: if it is determined in step S7' that it is lower than the target temperature T4s, then the degree of opening of the expansion valve 18 is reduced in order to reduce the supply of liquid refrigerant in the heat exchanger 7 (S10'), in the opposite case (S11') the degree of opening is increased.

[0043] If desired, a fan 21 can be arranged on the condenser 15 to blow ambient air over the condenser 15 and thus accelerate the heat dissipation via the condenser 15. The fan 21 can run at a fixed speed. It is also conceivable for the control circuit 13 to vary its speed in the same direction as that of the compressor 14 or with the ambient temperature in order to account for the increased heat generation at the condenser 15 with increased compressor capacity.

[0044] The speeds of the fans 11 are independent of the temperatures in the storage chambers 2, 3, 4 and the environment. They can be fixed; particularly in the case of storage chamber 4 used as a normal refrigeration compartment, it may be expedient to give the user the choice between different power levels or speeds of the fan 11 there at the interface 20. The higher the power of the fan 11, the smaller the temperature difference between the storage chamber 4 and the evaporator 7, which is sufficient to maintain the target temperature T4s of the storage chamber 4. And the higher the temperature of the heat exchanger 7, the smaller the proportion of air humidity from the storage chamber 4 that condenses on the heat exchanger 7 and must be discharged to the outside. Therefore, a high fan power is suitable for storing refrigerated goods sensitive to drying out.For refrigerated goods that are prone to mold formation or similar in high humidity, a lower fan speed can be set.

[0045] The same considerations apply to the control of the fan 11 in the storage chamber 2 when it is used as a normal cooling compartment or in an adjacent temperature range, for example as a fresh cooling compartment.

[0046] In order to create ideal storage conditions for both dry-sensitive and moisture-sensitive refrigerated goods, it may be desirable to use more than the three Fig. 1shown storage chambers in a refrigeration device. For cooling or heating such an additional storage chamber, the refrigerant circuit can have a plurality of line branches, each extending between connection points 23 of the pressure line 16 and 24 of a line connecting the expansion valve 18 to the heat exchanger 6, each of which, analogous to the components 17, 5, 18, has in series an upstream expansion valve, a heat exchanger for the additional storage chamber, and a downstream expansion valve. REFERENCE SYMBOL

[0047] 1 Housing 2 Storage chamber 3 Storage chamber 4 Storage chamber 5 Heat exchanger 6 Heat exchanger 7 Heat exchanger 8 Inner vessel 9 Partition wall 10 Heat exchanger chamber 11 Fan 12 Temperature sensor 13 Control circuit 14 Compressor 15 Condenser 16 Discharge line 17 Expansion valve 18 Expansion valve 19 Suction line 20 User interface 21 Fan 22 Internal heat exchanger 23 Connection point 24 Connection point

Claims

1. Refrigeration appliance, in particular a household refrigeration appliance, having at least a first, a second and a third storage chamber (2, 3, 4), a refrigerant circuit to which connected in series one behind the other between a pressure connection and a suction connection of a compressor (14) are: a condenser (15), a first expansion valve (17), a first heat exchanger (5) of the first storage chamber (2), a second expansion valve (18), and a second heat exchanger (6) of the second storage chamber (3), a third heat exchanger (7) assigned to the third storage chamber (4) and a control circuit (13) for controlling the operation of the compressor (14) and the expansion valves (17, 18), wherein the third heat exchanger (7) is arranged in series downstream of the second heat exchanger (6), characterised in that the control circuit (13) is configured to maintain a higher storage temperature (T4s) in the third storage chamber (4) than in the second storage chamber (3) and that the rotational speed of the compressor (14) can be adjusted to a plurality of values, preferably continuously, and the control circuit (13) is configured to increase the rotational speed when the temperature (T3) of the second storage chamber is above a target value (T3s) and / or to reduce the rotational speed when the temperature (T3) of the second storage chamber is below a target value (T3s).

2. Refrigeration appliance according to claim 1, characterised in that the second and the third heat exchangers (6, 7) are connected to one another without an intermediate restriction.

3. Refrigeration appliance according to claim 1 or 2, characterised in that the control circuit (13) is configured to enlarge the degree of opening of the first expansion valve (17) when the temperature (T4) in the third storage chamber (4) is above a target value (T4s), and / or to reduce the degree of opening of the first expansion valve (17) when the temperature (T4) in the third storage chamber (4) is below a target value (T4s).

4. Refrigeration appliance according to one of the preceding claims, characterised in that the control circuit (13) is configured to enlarge the degree of opening of the second expansion valve (18) when the temperature (T4) of the third storage chamber (4) is above a target value (T4s), and / or to reduce the degree of opening of the second expansion valve (18) when the temperature (T4) of the third storage chamber (4) is below a target value (T4s).

5. Refrigeration appliance according to one of the preceding claims, characterised in that the control circuit (13) is configured to enlarge the degree of opening of the second expansion valve (18) when the temperature in the first storage chamber (2) is above a target value (T2s), and / or to reduce the degree of opening of the second expansion valve (18) when the temperature (T2) in the first storage chamber (2) is below a target value (T2s).

6. Refrigeration appliance according to one of the preceding claims, characterised in that the control circuit (13) is configured to enlarge the degree of opening of the first expansion valve (17) when the temperature in the first storage chamber (2) is below a target value (T2s), and / or to reduce the degree of opening of the first expansion valve (17) when the temperature (T2) in the first storage chamber (2) is above a target value (T2s).

7. Refrigeration appliance according to one of the preceding claims, characterised in that the control circuit (13) is configured, with a deviation of the temperature (T4) of the third storage chamber (4) from a target value (T4s), to select an expansion valve to be adjusted as a function of whether a target temperature (T2s) of the first storage chamber (2) is above or below an ambient temperature (Tenv).

8. Refrigeration appliance according to one of the preceding claims, characterised in that a third expansion valve, a fourth heat exchanger of a fourth storage chamber and a fourth expansion valve are connected in series with one another and in parallel with the first expansion valve (17), the first heat exchanger (5) and the second expansion valve (18).

9. Refrigeration appliance according to one of the preceding claims, characterised in that a fan (11) for driving the air exchange between the heat exchanger (5, 6, 7) and the storage chambers (2, 3, 4) is assigned to at least one of the heat exchangers (5, 6 7).

10. Refrigeration appliance according to claim 9, characterised in that the control circuit (13) is configured to regulate the rotational speed of at least one fan (11) on the basis of a predetermined temperature difference between the evaporator (5, 6, 7) and the assigned storage chamber (2, 3, 4).

11. Method for the operation of a refrigeration appliance according to claim 1 with the steps: Enlarging (S6) the degree of opening of the first expansion valve (18) when (S3) the temperature (T2) of the first storage chamber (2) is above a target value (T2s), and / or reducing (S5) the degree of opening of the second expansion valve (18) when the temperature in the first storage chamber (2) is below a target value (T2s). - Increasing (S9) the rotational speed of the compressor (14) when (S4) the temperature (T3) in the second storage chamber (3) is above a target value (T3s) and / or reducing (S8) the rotational speed when the temperature (T3) in the second storage chamber (3) is below a target value (T3s); - Enlarging (S1 1) the degree of opening of the first expansion valve (17) when the temperature (T4) in the third storage chamber (4) is above a target value (T4s) and / or reducing (S10) the degree of opening of the first expansion valve (17) when the temperature (T4) in the third storage chamber (4) is below a target value (T4s).

12. Computer program product, which comprises instructions, which, upon execution on a computer, enable this to operate as a control circuit in a refrigeration appliance according to one of claims 1 to 10 or to execute the method according to claim 11.