WO2014023689A1 - Refrigeration device and operating method therefor - Google Patents

Description

 Refrigeration appliance and operating method for it

The present invention relates to a refrigerator, in particular a household refrigerator, and an operating method thereof.

Combination refrigerators have two or more cooling zones with different ones

Target temperatures. Usually, each of these cooling zones is assigned its own evaporator, and the multiple evaporators are with a common compressor in one

Refrigerant circuit connected.

In the simplest case, the multiple evaporators in the refrigerant circuit are connected in series, so that they can only be supplied with refrigerant at the same time. Although such refrigerators are simple and inexpensive, but have the disadvantage that the proportion of the cooling capacity, which accounts for each storage zone, is fixed by arrangement and dimensioning of the evaporator. Due to the different setpoint temperatures, however, the ratio of the required cooling capacities of the storage zones shifts with changing ambient temperatures. Therefore, such refrigerators achieve high energy efficiency only in a limited ambient temperature interval. In order to enable energy-efficient operation even with changing ambient temperatures, a refrigerant circuit is required, which makes it possible to selectively cool at least one of the storage zones, if only in this storage zone actually requires cooling. Such selective cooling can be realized by means of a refrigerant circuit with two parallel branches and a switching valve which makes it possible to supply either one of the two branches with refrigerant in each case.

The performance of the compressor in a modern refrigeration appliance is such that it is just sufficient at a given maximum ambient temperature to meet the cooling requirements of all storage zones of the device. If the maximum permissible ambient temperature is actually reached, therefore, the compressor

Run continuously to maintain the set temperature. At a high ambient temperature, therefore, there is a high probability that cooling demand occurs simultaneously in two storage zones. But this need can not be satisfied at the same time. Conventionally, one manages by the

Refrigerant flow is switched between the evaporators. Since the life of the switching valves limited and the switching is associated with a possibly disturbing for the user noise, it is traditionally sought to minimize the number of valve actuations, and it is only switched from the first evaporator to the second when the supply of the first Evaporator has led to a measurable cooling of the cooled by him storage compartment, or under normal

Operating conditions, i. if not, e.g. accidentally a door of the storage compartment has been left open, a measurable cooling should have led. This is

typically after a service life of about 20 minutes the case.

The object of the present invention is to improve the energy efficiency and / or the cooling capacity of a refrigeration device or an operating method for a refrigeration device.

The object is achieved on the one hand by having a refrigeration device, in particular a household refrigerator, with a refrigerant circuit having a compressor, a switching valve and two outgoing from the switching valve branches, a first and a second storage compartment, which are cooled by the refrigerant circuit, wherein the first storage compartment is cooled solely over the first branch, and being in an alternating one

 Operating mode, the switching valve with a running compressor between a first

Switching state in which the first branch is open and the second is locked, and is switchable to a second switching state in which the first branch is disabled and the second branch is open, the residence time of the switching valve in the first switching state is shorter than 5 minutes.

The consequence of this measure is that cooling of the first storage compartment is interrupted at the latest after 5 minutes. This time is significantly shorter than the compressor run time normally desired in a refrigerator - this is usually done as long as possible, typically 20 minutes or more, to minimize efficiency losses associated with turning the compressor on and off. with the result that an evaporator of the first branch, which cools the first storage compartment, during the time spent in the first switching state by far does not cool as much as at a residence time of 20 minutes or more. After the transition to the second switching state, this evaporator has time to heat up again, so that even at a later renewed switching to the first switching state, no low temperature of the evaporator is achieved. The evaporator therefore operates on average at a higher temperature than it would do in continuous operation. The temperature gradient between the evaporator and the environment of the refrigerator is therefore relatively low, and accordingly, the heat flow from the outside to the evaporator is low. In addition, the relatively high evaporation temperature leads to an increased pressure in the evaporator, and consequently the mass of the refrigerant circulated at a given volumetric flow rate of the compressor is correspondingly high. This also has a positive effect on energy efficiency and cooling capacity. By simulation calculations it can be shown that the resulting from the alternate supply of the two branches average increase in temperature of the first evaporator, the energy consumption for the cooling of the first storage compartment can be reduced by several percent or the cooling capacity of the device can be increased.

According to a first embodiment of the invention, the second storage compartment is cooled solely via the second branch. In particular, in this case, it is expedient if the residence time of the switching valve in the second state is shorter than 5 minutes in order to achieve the advantages of the high average evaporator operating temperature also with respect to the second storage compartment.

According to a second embodiment, the second storage compartment can be cooled over both branches. For this purpose, the two branches can meet at a junction point of the second storage compartment cooling second evaporator, but they can also run parallel to each other via the second evaporator and unite only between this and a suction port of the compressor.

Surprisingly, no appreciable efficiency improvement or

Cooling performance improvement observed when the residence time of the switching valve in the first and / or in the second switching state is shorter than 1 minute. According to the simulation calculations, the greatest improvement in efficiency or cooling performance is at least in the first case with a residence time

Switching state of between 2 and 4 minutes to be expected.

The alternate operating mode should be active at least when there is a simultaneous need for cooling in both storage compartments.

If cooling demand is detected only for one of the storage compartments, the switching valve should lock the branch assigned to the other storage compartment. In the simplest case, the dwell times of the switching valve in the first and in the second

Switching state determined by a timer. For reasons of simplicity, the residence time, which is predetermined identically from time to time, may be the same for the first and the second switching state. However, it is also conceivable, in principle, to control the residence time in the two switching states with the aid of temperature sensors on the evaporators, which are already present in many refrigeration appliances, by switching to the second (or first) switching state at given switching temperatures of the first (or second) evaporator

is changed. Thus, the temperature gradient between evaporators and the environment can be precisely controlled, but the residence times are not necessarily identical from time to time.

Subject of the invention is also a method for operating a refrigeration device having a refrigerant circuit having a compressor, a switching valve and two of the switching valve, parallel branches, a first and a second storage compartment, which are cooled by the refrigerant circuit, wherein the first storage compartment alone is cooled over the first branch, wherein in an alternating operating mode, the switching valve with the compressor is switched between a first switching state in which the first branch is open and the second is locked, and a second switching state in which the first branch is disabled and the second Branch is open, and the residence time of the switching valve is at least in the first switching state shorter than 5 minutes. Further features and advantages of the invention will become apparent from the following

Description of embodiments with reference to the accompanying figures. From this description and the figures are also features of the

Embodiments, which are not mentioned in the claims. Such features may also occur in combinations other than those specifically disclosed herein. Therefore, the fact that several such features are mentioned in the same sentence or in a different type of textual context does not justify the conclusion that they can occur only in the specific combination disclosed;

instead, it must be assumed that, of several such characteristics, it is also possible to omit or modify individual ones, provided that this is the case

Functionality of the invention is not in question. Show it:

Fig. 1 is a schematic representation of a first invention

 Refrigeration unit; Fig. 2 is a schematic representation of a second invention

 Refrigeration unit;

FIG. 3 is a flowchart of an operating method performed by a control circuit of the refrigerator; FIG. and

Fig. 4 shows an exemplary temporal evolution of

 Evaporator temperatures of the refrigerator of FIG. 1 or 2.

Fig. 1 shows schematically a household refrigerator with a heat-insulating housing 1, the interior of which is divided into two storage compartments with different set temperatures, here a freezer compartment 2 and a normal refrigeration compartment 3. The subdivision here is a wall 4, which is like the subjects 2, 3 surrounding walls of the housing 1 filled with insulating material and strike at the front edge in the figure, not shown doors of the freezer compartment 2 and the normal refrigeration compartment 3 in the closed position.

A refrigerant circuit of the apparatus includes a compressor 7 and one of them

Pressure connection outgoing line, arranged in a conventional manner, for example, attached to a rear wall of the housing 1 condenser 8 and a dryer 9 are. At a directional control valve 16, the line divides into two parallel branches 12, 13. The branch 12 comprises a capillary 10 and a freezer 2 cooling evaporator 5, the branch 13, a capillary 1 1 and the normal cooling compartment 3 cooling evaporator 6. The evaporator 5, 6 are shown here as coldwall evaporators, but there are also other types of evaporators into consideration.

A suction line 14 extends from outlet ports of the evaporators 5, 6 via a confluence 15 to a suction port of a compressor 7.

A control circuit 17 for switching on and off of the compressor is with

Temperature sensors 18, 19 which are arranged on the freezer compartment 2 and the normal refrigeration compartment 3 spaced from the evaporators 5, 6 are arranged to one for the

Air temperature in the relevant compartment 2, 3 or the temperature of the stored therein refrigerated goods representative measured value to capture. The control circuit 17 is connected to the directional control valve 16 and a not shown

User interface connected to a user in a usual way

Set temperatures of the compartments 2, 3 can adjust. From these setpoint temperatures, the control circuit 17 derives switch-on thresholds T2in, T3on and switch-off thresholds T2off, T3off, each of which defines an interval of predetermined width about the setpoint temperature of each compartment 2, 3.

FIG. 2 shows an alternative embodiment of the refrigeration device in a section analogous to FIG. 1. Corresponding components of the two embodiments are provided in both figures with the same reference numerals and will be described with reference to FIG. 2 only insofar as differences from FIG. 1 are present. The essential difference between the two embodiments is that according to FIG. 2 a

A confluence, at which the two branches 12, 13 reunite, on the evaporator 5, in close proximity to an injection point 20 formed by the downstream end of the capillary 10, is arranged. This arrangement has the consequence that when the temperature sensor 19 detects cooling demand in the normal cooling compartment 3, both evaporators 6, 5 are supplied in series with refrigerant. The operating method reproduced in the flowchart of FIG. 3 is repeated continuously by the control circuit 17 of the refrigerating appliance of FIG. 1 or FIG.

In step S1 it is checked whether, since the previous implementation of the method, the temperature detected by the temperature sensor 19 T3 of the normal cooling compartment 3 the

Switch-on threshold T3 has exceeded. The compressor 7 may be on or off at this time. If the switch-on threshold T3on has not been exceeded, a corresponding check is made for the freezer compartment 2 in step S2.

If, here too, the switch-on threshold T2 has not been exceeded since the previous execution of the method, it is checked in step S3 whether the

 Switch-off threshold T3from the normal refrigeration compartment was undershot. If so, then the compressor 7 must be in operation and is turned off in step S4. If not, a corresponding check is made in step S5 for the freezer compartment 2. If T2 has been undershot, the compressor 7 is also turned off in step S4; otherwise, the method ends without the operating state of the compressor 7 or the directional control valve 16 has been changed.

If, on the other hand, an exceeding of the switch-on threshold T3on is detected in step S1, then first in step S6 the directional control valve 16 becomes that of its two

Shift positions offset in which the branch 13 is open and the branch 12 is disabled before the process goes to step S8.

If, on the other hand, an exceeding of the switch-on threshold T 2 in FIG

Detected freezer compartment 2, then the directional control valve 16 is set in step S7 in the switching position in which the extending over the freezer branch 12 is open and the branch 13 of the normal refrigeration compartment is locked.

In step S8, it is checked whether the compressor 7 is in operation or not. If not, then it is turned on in step S9. Thus, each of the evaporator of that compartment is supplied with refrigerant, has been found in the cooling demand. Following this, the method may end or it may jump to S3 as shown in the figure. However, if the compressor 7 is already in operation at the time of step S8, then this means that one of the two compartments 2, 3 has already been cooled and now the second compartment also has cooling demand. Since step S6 or S7 has been performed immediately before, at the time of step S8, the branch 12 or 13 of the second compartment is already supplied with refrigerant, so that a minimum delay cooling effect is applied in the second compartment.

As a result, in step S10, a timer is started to measure a dwell time Δt. The duration of the residence time At may take two different values, depending on which of the compartments 2, 3 has occurred as a second cooling requirement, or it may be identical for both compartments. Here it is for both subjects 2, 3 three minutes. The residence time Δt is long compared to a possible waiting time between the end of an iteration of the process and the beginning of the subsequent one.

After expiration of the residence time At, the directional control valve 16 is switched over in step S1 1, i. if branch 12 was open during the dwell time of step S9, it is now disabled and branch 13 is opened, and if branch 13 was open during the dwell time of step S9 branch 12 is now opened in its place.

In step S12, it is checked whether the cooling requirement of the normal refrigerating compartment 3 is covered, i. whether T3ein dropped below T3aus. If so, then it means that during the

Dwell At the branch 13 must have been open and now the branch 12 is open, where the freezer compartment 2 is located. The method may therefore end at this point, with the result that the compressor 7 which is still running now supplies the branch 12. If, on the other hand, it is determined in step S12 that the cooling requirement of the freezer compartment 2 is covered, the branch 12 must have been open during the previous residence time Δt, so that, when the process now ends, the refrigerant flows via the branch 13 and the normal refrigeration compartment 3 cools. If, on the other hand, none of the switch-off thresholds T3out, T2off have been undershot, the method returns to step S9 to start a new dwell time Δt. FIG. 4 shows, by way of example, the time evolution of the temperature Tv, which can result from carrying out the method of FIG. 2 on one of the evaporators 5, 6 of the refrigeration device from FIG. 1 or on the evaporator 6 of the refrigeration device of FIG. 2. Of the

For the sake of simplicity, only the case will be considered below in the following: FIG. 4 shows the temperature of the evaporator 6; that in the case of the refrigerator of Fig. 1, a similar course may also occur at the evaporator 5, should be understood by reference to the following explanations immediately.

A time point at which an exceeding of the switch-on threshold T3a is detected (S1) and consequently the compressor 7 is switched on (S9) is designated by t0 in FIG. Since the evaporator 6 belongs to the normal refrigeration compartment 3, the temperature Tv of

 Evaporator 6 (which generally differs from the temperature T3 of the standard refrigerator compartment 3) at this time some degrees above 0 ° C. With the supply of liquid refrigerant to the evaporator 6 via the branch 13, which starts after the compressor 7 has been switched on, the evaporator temperature Tv decreases rapidly and can reach 0 ° C. after just a few minutes. During this time, the method of FIG. 2 is iterated several times.

If there is no refrigeration demand in the other compartment, here the freezer compartment 2, is determined, the evaporator 6 is continuously supplied with refrigerant, and its temperature Tv decreases continuously, as shown by a dashed curve A in Fig. 4. This curve A converges to a saturation temperature which corresponds to the boiling temperature of the refrigerant at the pressure maintained by the compressor 7 in the evaporators 5, 6. This saturation temperature is not reached during operation of the refrigerator, since the normal refrigeration compartment 3 may not be cooled so far. So that the

Evaporator temperature Tv of the saturation temperature approaches to a difference of a few ° C, a continuous supply of the evaporator 6 with refrigerant over a period of 20 minutes or more is required.

If shortly after tO in a further iteration of the method of Fig. 2 in the

Freezer compartment 2, the switch-on threshold T2 is exceeded (S1), the switches

Control unit 17 at time t1, after elapse of the residence time At of step S10, that is, at the earliest 3 minutes after t0, the directional control valve 16 in order to supply the evaporator 5. Since the evaporator 6 is now cut off from the refrigerant supply, its temperature increases by heat exchange with the tray 3 again, as shown in the solid curve B, so that, if after repeated elapse of the Dwell At, at time t2, the directional control valve 16 is switched again, the temperature of the evaporator 6 is significantly higher than at time t1. The height

Temperature provides for a rapid evaporation of the supplied liquid refrigerant, and consequently for a high mass flow rate and a correspondingly good efficiency of the compressor. 7

Periods in which the evaporator 6 is supplied with refrigerant, and those in which it is cut off from the supply, alternate in each case

Time interval At, at times t3, t4, ... from. The regular interruption of the refrigerant supply to the evaporator 6 and the resulting relatively low temperature difference between the evaporator 6 and the compartment 3 cooled by it has the consequence that the time to reach the

Switching off temperature T3 is significantly longer at the time tn than the exclusive supply of the evaporator 6. However, since the evaporator 6 in the times in which it is supplied with refrigerant, has a relatively high temperature and thereby enables efficient operation of the compressor 7, the Part of the period of time [to, tn], in which the evaporator 6 is supplied with refrigerant, shorter than the time period [to, tn '], which is required in continuous supply of the evaporator 6 with refrigerant to reach the switch-off temperature T3aus.

A development of the temperature similar to curve B shown in FIG. 4 would also be observed on the evaporator 5 of the refrigerator of FIG. 1, if it is supplied alternately with the evaporator 6 with refrigerant in the case of simultaneous refrigeration demand of the compartments 2, 3. In the refrigerator of Fig. 2 is to be expected for the evaporator 5 insofar with a different development of the evaporator temperature Tv, as in the case of simultaneous refrigeration demand of both compartments 2, 3, the evaporator 5 is never completely cut off from the refrigerant supply, but at best temporarily the evaporator 6 in Row is connected downstream. Consequently, cold refrigerant circulates continuously in the evaporator 5 as long as the compressor 7 is running, with the result that the temperature rise of the

Evaporator 5 at the times in which the evaporator 6 is supplied with refrigerant is slowed down compared to the curve B, or, if liquid refrigerant in not

negligible amount reaches the evaporator 5, the temperature at times, in which the evaporator 6 is supplied, continues to fall. Thus, the evaporator reaches 5 shortly after switching on the compressor 7, a required for cooling the freezer compartment 2 low operating temperature.

REFERENCE NUMBERS

1 housing

 2 freezer

3 normal refrigerated compartment

 4 wall

 5 evaporators

 6 evaporator

 7 compressors

8 liquefier

 9 dryers

 10 capillaries

 1 1 capillary

 12 branch

13 branch

 14 suction line

 15 confluence

 16 way valve

 17 control circuit

18 temperature sensors

 19 temperature sensor

 20 injection point

Claims

Refrigerating appliance, in particular household refrigerating appliance, having a refrigerant circuit, which has a compressor (7), a switching valve (16) and two branches (12, 13) extending from the switching valve (16), a first and a second storage compartment (3, 2), which are cooled by the refrigerant circuit, wherein the first storage compartment (3) is cooled solely via the first branch (13), wherein in an alternate operating mode, the switching valve (16) with the compressor (7) between a first switching state in which the first Branch (13) is open and the second (12) is locked, and a second switching state is switchable, in which the first branch (13) is locked and the second branch (12) is open, characterized in that the residence time of the switching valve (16 ) is shorter than 5 min at least in the first switching state. Refrigerating appliance according to claim 1, characterized in that the second storage compartment (2) is cooled solely via the second branch (12). Refrigerating appliance according to claim 1, characterized in that the second storage compartment (2) via both branches (13, 12) is cooled. the two branches (12, 13) meet at a junction point of the second evaporator (5). Refrigerating appliance according to one of the preceding claims, characterized in that the dwell times of the switching valve (16) in the first and in the second  Switching state are longer than 1 min. Refrigerating appliance according to one of claims 1 to 3, characterized in that the residence time of the switching valve (16) is at least in the first switching state between 2 and 4 min. 6. Refrigerating appliance according to one of the preceding claims, characterized in that it operates in the alternating mode of operation, if there is a simultaneous need for cooling in both storage compartments. 7. Refrigerating appliance according to one of the preceding claims, characterized in that if for only one of the storage compartments (2, 3) cooling demand is detected, the switching valve (16) to the respective other storage compartment (3, 2) associated branch (13, 12) locks. 8. Refrigerating appliance according to one of the preceding claims, characterized in that the dwell times of the switching valve (16) in the first and in the second  Switching state are determined by a timer. 9. Refrigerating appliance according to claim 8, characterized in that the residence times in the first and in the second switching state are the same. 10. A method for operating a refrigeration device, in particular a  Household refrigerating appliance, comprising a refrigerant circuit comprising a compressor (7), a switching valve (16) and two parallel branches (12, 13) extending from the switching valve (16), a first and a second storage compartment (3, 2), which are cooled by the refrigerant circuit, wherein the first storage compartment (3) is cooled solely by the first branch (13), wherein in an alternating  Operating mode, the switching valve (16) with the compressor (7) between a first switching state in which the first branch (13) is open and the second (12) is locked, and a second switching state is switched, in which the first branch (13) locked and the second branch (12) is open, characterized in that the residence time of the switching valve (16) at least in the first switching state is shorter than 5 min.