Patent Application
20220364781
The present invention relates to a refrigeration appliance, in particular a household refrigeration appliance, having at least one storage compartment which can optionally be heated or cooled.
Such a refrigeration appliance is known from DE 10 2016 032 986 A, for instance. With this known refrigeration appliance, heat exchangers of the compartment which can be heated and cooled and of a first cooled compartment with each in case an upstream and a downstream expansion valve are arranged in line sections of the refrigerant circuit which are parallel to one another and ii both sections lead to the evaporator of a second cooled compartment. Since the pressure in the last evaporator is lower than in any of the heat exchangers, the second cooled compartment is inevitably the coldest, i.e. the first cooled compartment is considered to be the normal refrigerator compartment, the second to be the freezer compartment. Four expansion valves are therefore required in order to realize three different temperature zones in the refrigeration appliance; this renders the known refrigeration appliance relatively expensive. Moreover, its refrigerant circuit is sensitive to overflows from the heat exchangers, which necessitates a sensitive and accordingly expensive control.
An object of the present invention is therefore to create a refrigeration appliance with a storage compartment which can be heated and cooled, which is assembled in a simpler manner and can accordingly be realized cost-effectively. A further object is to create an operating method for such a refrigeration appliance.
The object is achieved on the one hand in that, with a refrigeration appliance, in particular a household refrigeration appliance, having at least a first, a second and a third storage chamber, a refrigerant circuit, to which are connected in series one behind the other between a pressure connection and a suction connection of a compressor:
With this setup, two expansion valves are still required in order to adjust the mass flow through the first heat exchanger and the pressures in the first and in the second heat exchanger, but a temperature regulation of the third storage chamber can take place without recourse to expansion valves, by, depending on requirement, only refrigerant vapor or vapor and liquid refrigerant in variable parts being allowed to pass from the second into the third heat exchanger. An overflow of the second heat exchanger does not result here in malfunctioning and need not be suppressed by means of control; instead, it forms part of the normal operation of the refrigeration appliance, by it enabling the third heat exchanger to be supplied with liquid refrigerant.
The connection between the second and third heat exchanger does not require a further expansion valve; on the contrary, this connection should be as free as possible of restrictions which impede the transfer of refrigerant to the third heat exchanger or favor a pressure difference between the second and third heat exchanger. The smallest free cross-section of a refrigerant pipe connecting the heat exchangers is preferably substantially the same size, in any case at least half as large as an average free cross-section of lines of the heat exchangers.
It should be possible to adjust the rotational speed of the compressor, preferably continuously, to a plurality of values, so that as a result of uninterrupted operation of the compressor, temporal fluctuations in the temperature in the storage chambers and the overconsumption of electrical energy associated with these fluctuations can be minimized.
The control circuit is preferably configured to increase the rotational speed of the compressor when the temperature in the second storage chamber is above a target value and/or to reduce the rotational speed when the temperature in the second storage chamber is below a target value. By increasing the rotational speed of the compressor, the pressure in a suction line leading to the compressor and via this also the pressure in the second and third heat exchanger can be reduced. Since the cooling effect of the third heat exchanger is largely not based on the evaporation of liquid refrigerant but instead on through-flowing vapor which originates from the second heat exchanger, the change in rotational speed at the most marginally influences the cooling effect of the third heat exchanger; the drop in pressure by contrast has a direct effect on the evaporation of the refrigerant which takes place in the second heat exchanger.
The afore-cited target values may be identical; they may however also define the limits of an interval within which the rotational speed of the evaporator remains unchanged.
In order to regulate the temperature in the third storage chamber, the control circuit is preferably configured to enlarge the degree of opening of the first expansion valve when the temperature in the third storage chamber is above a target value, and/or to reduce the degree of opening of the first expansion valve when the temperature in the third storage chamber is below a target value. 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, an adjustment of the first expansion valve has a surprising effect above all in the third heat exchanger. Opening the first expansion valve initially brings about a reduction in the choke effect of the entire refrigerant circuit. The pressure in the second and third heat exchanger however only changes a little as a result, since the extent to which this pressure increases causes the throughput of the compressor also to grow with a constant rotational speed. As a result, the main consequence of the opening of the first expansion valve is an increased flow of liquid refrigerant through the second expansion valve and as a result, 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 an increased cooling of the third storage chamber.
The control circuit can also be configured to enlarge the degree of opening of the second expansion valve when the temperature in the third storage chamber is ii above a target value, and/or to reduce the degree of opening of the second expansion valve when the temperature in the third storage chamber is below a target value.
A decision as to which of these two possibilities is followed is expediently made on the basis of a comparison of the target temperature of the first storage chamber with the ambient temperature.
In order to control the temperature in the first storage chamber, the control circuit can be configured to enlarge the degree of opening of the second expansion valve when the temperature in the first storage chamber is above a target value and/or to reduce the degree of opening of the second expansion valve when the temperature in the first storage chamber is below a target value.
Alternatively, the control circuit can be configured to enlarge the degree of opening of the first expansion valve when the temperature in the first storage chamber lies below a target value and/or to reduce the degree of opening of the first expansion valve when the temperature in the first storage chamber is above a target value.
Here the selection between the alternatives can also be made on the basis of a comparison of the target temperature of the first storage chamber with the ambient temperature.
A third expansion valve, a fourth heat exchanger of a fourth storage chamber and a fourth expansion valve can be connected in series with one another and in parallel with the first expansion valve, the first heat exchanger and the second expansion valve. A number of compartments which can optionally be heated or cooled can therefore be produced in the refrigeration appliance.
The temperatures in these compartments can be adjusted independently of one another by adjusting the vaporization pressures with the aid of the upstream and downstream expansion valves.
With a refrigeration appliance having a fourth storage chamber, as described above, the degree of opening of the third expansion valve can also be enlarged ii when the temperature in the third storage chamber is above a target value, and/or the degree of opening of the third expansion valve can be reduced when the temperature in the third storage chamber is below a target value.
If desired, further storage chambers, in each case with an assigned heat exchanger and the expansion valves arranged upstream and downstream hereof in a branch of the refrigerant circuit, can be provided.
A fan for driving the air exchange between the heat exchanger and the storage chamber can be assigned to at least one of the heat exchangers. Such a fan is advantageous in terms of intensifying the heat exchange with the storage chamber and thus in reaching a high exchanging capacity with a compact heat exchanger. They are not essential in order to control the cooling of the various storage chambers. In the simplest case, such a fan can therefore be operated at an irregular or fixed rotational speed.
In particular when a storage chamber is operated cooled, it may be useful to regulate the rotational speed of the fan on the basis of a predetermined temperature difference between the evaporator and the storage chamber, in order thus to adjust the extent of drying of the air in the storage chamber by condensation on the evaporator or the humidity content of the air.
The object is further achieved by a method for operating a refrigeration appliance, as described above, with the steps:
Further features and advantages of the invention result from the description of exemplary embodiments with reference to the appended figures, in which:
Each storage chamber 2, 3, 4 is equipped with a temperature sensor 12. Measured values of the temperature sensor 12 are detected by a control circuit 13.
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, which leads to a suction connection of the compressor 14. The expansion valves 17, 18 are designed in a manner known per se but not described here, in order to maintain a pressure difference, predetermined by a control signal, between the inlet and outlet. The source of the control signals is the control circuit 13. The pressure line 16 and the suction line 19 run on one part of their length in a contrarotating manner in close contact with one another, in order thus to form an internal heat exchanger 22, in which the compressed refrigerant outputs residual heat to the vapor in the suction line 19 shortly before reaching the expansion valve 17.
The pressure difference which can be adjusted on the expansion valve 17 is to a great extent variable. On the one hand, the expansion valve 17 allows a pressure to be adjusted in the heat exchanger 5, which, if at all, only differs minimally from the pressure at the pressure connection of the compressor 14, so that condensation of refrigerant takes place in the heat exchanger 5 and in the condenser 15, and the storage chamber 2 can be operated at a target temperature above the ambient temperature, and refrigerant condensed in the condenser 15 and heat exchanger 5 is supplied to the heat exchangers 6 and 7 by way of the expansion valve 18. An upper limit of the temperature at which the storage chamber 2 can be operated should not amount to below +18° C.
Less high demands are placed on the expansion valve 18: in order to enable operation of the storage chamber 3 as a freezer compartment, even if the storage compartment 2 is operated as a normal refrigerator compartment, a non-negligible drop in pressure on the expansion valve 18 is required. The maximum pressure difference on the expansion valve 18 should be sufficient to also then enable a freezer compartment operation of the storage chamber 3 if essentially the full output pressure of the compressor 14 is present at the input of the expansion valve 18.
There is no appreciable drop in pressure between the heat exchangers 6 and 7. In particular, both heat exchangers 6, 7 and a line connecting them can be manufactured from the same type of pipe with constant cross-sectional dimensions.
Target temperatures for all three storage chambers 2, 3, 4 can be adjusted on a user interface 20 of the control circuit 13. If one of the storage chambers 2, 3, 4 has a fan 11, the possibility can also be provided on the user interface 20 to select an air humidity value for the relevant storage chamber.
In step S3, the temperature T2 is compared with the target temperature T2s. If both values T2, T2s match within a predetermined tolerance interval, the method moves directly to step S4. If the measured temperature T2 is significantly lower than T2s, then the control circuit reduces the degree of opening of the expansion valve 18 (S5), in order in this way to increase the pressure or the boiling temperature of the refrigerant in the heat exchanger 5. The reduction in the degree of opening can consist here in increasing the pressure difference to be maintained by the expansion valve 18 between the heat exchangers 5 and 6. Conversely, in step S6, the degree of opening is increased (or the pressure difference is reduced) when the temperature T2 is significantly higher than T2s.
The extent to which the pressure difference in step S5 or S6 is changed can be a constant or it can take into consideration circumstances such as for instance the sum of the difference between T2 and T2s or the time taken for the deviation between T2 and T2s, in order to minimize the time until the match is reestablished between T2 and T2s or the controller is overshot.
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 compartment 3 always operates as an evaporator; to this end, during operation it is continuously supplied with liquid refrigerant which is either condensed in the condenser 15 and in the heat exchanger 5 is only evaporated to a small extent, or because in the heat exchanger 5 condensation has taken place in addition to that of the condenser. Since the intake pressure of the compressor 14 essentially prevails in the heat exchanger 6 as in heat exchanger 7 and it is well supplied with the liquid refrigerant, the heat exchanger 6 is therefore the coldest of the heat exchangers 5, 6, 7 and T3, T3s normally lie in a range typical of a freezer compartment which is below −10° C., e.g. approx. −18° C.
If both values T3, T3s match within a predetermined tolerance interval, the method moves directly to step S7. If the measured temperature T3 is significantly lower than T3s, then the control circuit 13 reduces the rotational speed of the compressor 14 (S8), in order in this way to increase the pressure or the boiling temperature of the refrigerant in the heat exchanger 6. Conversely, in step S9, the rotational speed is increased when the temperature T3 is significantly higher than T3s.
The extent to which the rotational speed in step S8 and S9 is changed can be a constant or it can take into consideration circumstances such as for instance the sum of the difference between T3 and T3s or the time taken for the deviation between T3 and T3s, in order to minimize the time until the match is reestablished between T3 and T3s or the controller is overshot.
In step S7, the temperature T4 is compared with the target temperature T4s adjusted for the storage chamber 4 by the user. If both values T4, T4s match within a predetermined tolerance interval, the method moves back to step S1 after a predetermined waiting time (S12). If the measured temperature T4 is significantly lower than T4s, then the control circuit reduces the degree of opening of the expansion valve 17 (S10), in order in this way to reduce the mass flow of the refrigerant and thus to reduce the quantity of liquid refrigerant which reaches the heat exchanger 7. Conversely, in step S11, the degree of opening is increased when the temperature T4 is significantly higher than T4s so that more liquid refrigerant reaches the heat exchanger 7.
If, by contrast, in step S2, it is determined that heating operation is selected for the storage chamber 2, i.e. when T2s>Tenv, then T2 is then likewise compared with T2s (S3′), but when T2 is significantly below T2s, the expansion valve 17 is opened further (S5′) or when T2 is significantly above T2s, it is closed again (S6′).
The steps S4, S8, S9 for the temperature regulation in the storage chamber 3 are identical to those described above for the case of cooling operation in the storage chamber 2.
The temperature T4 in the storage chamber 3 is then regulated by way of the expansion valve 18; when it is determined in step S7′ that this is lower than the target temperature T4s, then the degree of opening of the expansion valve 18 is reduced, in order to reduce the availability of liquid refrigerant in the heat exchanger 7 (S10′); in the opposite case (S11′), the degree of opening is enlarged.
If desired, a fan 21 can be arranged on the condenser 15 in order to blow ambient air via the condenser 15 and thus to accelerate the heat dissipation via the condenser 15. The fan 21 can run at a fixed rotational speed. It is also conceivable for the control circuit 13 to vary its rotational speed in the same direction as that of the compressor 14 or with the ambient temperature, in order to take into account the drop in pressure at the condenser 15 which has increased with an increased compressor power.
The rotational speeds of the fan 11 are independent of the temperatures in the storage chambers 2, 3, 4 and the ambient temperature. They can be fixedly predetermined; particularly in the case of the storage chamber 4 which can be used as a normal refrigeration compartment, it may be expedient to provide the selection between various power stages or rotational speeds of the fan 11 there to the user at the interface 20. The higher the power of the fan 11, the lower therefore 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 therefore the portion of air humidity from the storage chamber 4, which condenses on the heat exchanger 7 and has to be sent into the atmosphere. A high fan power is therefore suited to the storage of refrigerated goods which are sensitive to drying. For refrigerated goods which tend to form mold or suchlike with high humidity, a lower fan power can be adjusted.
The same considerations apply to the control of the fan 11 in the storage chamber 2, when this is used as a normal refrigerator compartment or in a temperature range adjacent thereto, for instance as a fresh refrigerator compartment.
In order to be able to create ideal storage conditions both for refrigerated goods which are sensitive to drying and also to wet, it may be desirable to have more than the three storage compartments shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2019 216 582.6 | Oct 2019 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/079314 | 10/19/2020 | WO |
