WO2016034446A1

WO2016034446A1 - Refrigeration appliance and refrigerating machine therefor

Info

Publication number: WO2016034446A1
Application number: PCT/EP2015/069282
Authority: WO
Inventors: Andreas BABUCKE; Stefan Holzer; Matthias Mrzyglod
Original assignee: BSH Hausgeräte GmbH
Priority date: 2014-09-04
Filing date: 2015-08-21
Publication date: 2016-03-10
Also published as: DE102014217672A1

Abstract

A refrigerating machine for a domestic refrigeration appliance comprises a compressor (1) as well as a first and a second evaporator (13, 14) which are placed in parallel branches (9, 10) of a refrigerant circuit (4) along with one upstream capillary (11, 12) each. A valve (18) for blocking a refrigerant flow from the first evaporator (13) to the second evaporator (14) is placed in a downstream portion of the refrigerant circuit (4), between outlets of the evaporators (13, 14) and an inlet (3) into the compressor (1). A stop valve (7) is placed in an upstream portion of the refrigerant circuit (4), between an outlet (2) of the compressor (1) and inlets into the evaporators (13, 14). A control unit (19) is designed to operate the compressor (1) with the stop valve (7) in the closed position at the end of a cooling operating phase of at least one of the two evaporators (13, 14).

Description

Refrigerating appliance and chiller for it

The present invention relates to a refrigeration appliance, in particular a domestic refrigeration appliance, and more particularly to the construction of a refrigerator which can be used in such a refrigeration appliance. Domestic refrigerators with two held at different operating temperatures storage compartments such as a freezer and a normal refrigerated compartment and a

Chillers, each having a first evaporator for cooling the first storage compartment and a second evaporator for cooling the second storage compartment in mutually parallel branches of a refrigerant circuit, are known per se. To one

It is to enable energy-efficient operation of such a refrigerator

desirable that prevail in the evaporators, at least during their cooling operating phases different, each adapted to the operating temperature of the compartment to be cooled from them evaporating temperatures. For this it is necessary that different pressures can be set in the evaporators.

At high ambient temperature or other reasons increased refrigeration demand of the freezer compartment can after a cooling phase of the freezer in its

Evaporator stored refrigerant amount to be greater than under normal

Operating conditions, so that in a subsequent cooling phase of the

Normal refrigeration compartment, the amount of circulating refrigerant is reduced. The resulting inappropriately low evaporation temperature affects the efficiency of the chiller.

However, if the different pressures in the evaporators persist outside of the cooling operating phases, they will drive refrigerant displacements between the evaporators resulting in undesirable heat transfer from the evaporator of the evaporator

Normal cooling compartment to go to the evaporator of the freezer compartment. Although valves may be provided to prevent the pressure equalization between the evaporators outside the cooling operating phases, a lack of tightness of such a valve is hardly noticeable to a user of the refrigeration appliance and also reduces efficiency. Object of the present invention is to provide a refrigerator with evaporators in mutually parallel branches of a refrigerant circuit, which allows reliable energy-efficient operation.

The object is achieved by, in a refrigerating machine with a compressor, a first and a second evaporator, which are arranged together with a respective upstream capillary in parallel branches of a refrigerant circuit, wherein in a downstream part of the refrigerant circuit between outputs of the evaporator and an input of the compressor a valve for locking a

Refrigerant flow is arranged from the first evaporator to the second evaporator, in an upstream part of the refrigerant circuit, between an output of the compressor and inputs of the evaporator, a stop valve is arranged and a control unit is arranged, at the end of a cooling phase of operation of at least one of the two evaporators, the compressor when it is closed Stop valve to operate. The effect of this measure varies, depending on which evaporator it affects.

If the affected evaporator is the first evaporator, by continuing to operate the compressor with the stop valve closed, the pressure in the first evaporator can be lowered and brought close to the pressure prevailing in the - generally colder - second evaporator. The resulting reduced pressure difference between the two sides of the valve for blocking the flow of refrigerant also reduces any leakage of refrigerant vapor from the first to the second evaporator and a heating caused in particular by condensation of this refrigerant vapor in the second evaporator.

If the affected evaporator is the second evaporator, then, by continuing the operation of the compressor, the amount of refrigerant left in the second evaporator after the cooling operation phase thereof can be reduced as necessary to ensure that a sufficient refrigerant amount for energy-efficient operation also is available in a subsequent cooling operation phase of the first evaporator. The time between the closing of the stop valve and the end of the cooling operation phase can be 30-120 s in both cases.

In order, in particular, if the affected evaporator is the second evaporator, to make a decision on the need for a closed-loop compressor, a temperature sensor can be arranged at an outlet of the second evaporator, and the control unit can be set up to reduce the time between the closing of the second evaporator Stop valve and the end of the cooling phase of the second evaporator based on the temperature detected by the temperature sensor to regulate. A low temperature indicates a large amount of refrigerant stored in the evaporator; the lower the detected temperature, the longer the time between the closing of the stop valve and the end of the cooling operation phase can be suitably selected. An overflow in case of overfilling of the second evaporator can be avoided. The time between the closing of the stop valve and the end of the cooling operation phase may be a continuous function of the temperature or may be switchable between a small number of discrete values. It can take the value zero.

Since the temperature sensor at the output of the second evaporator is cumbersome to install, according to an alternative embodiment, the time between the closing of the stop valve and the end of the cooling operation phase also, for. B. on the basis of an empirically optimized for a given model of refrigeration device context, based on the ambient temperature and / or the time elapsed since the beginning of the cooling phase operating time to be controlled based on the assumption that these two factors a conclusion on the amount of in the second evaporator allow accumulated liquid refrigerant.

It may also be useful to open the stop valve before beginning a cooling operation phase of the first evaporator. In particular, if the first evaporator has been sucked empty in a preceding cooling operation phase of the second evaporator, opening the stop valve simultaneously with the beginning of the aspiration would result in the evaporation of the fresh into the first evaporator taking place at an inappropriately low temperature and taking a long time, until a to desired evaporation temperature adjusts the appropriate pressure in the first evaporator. By previously opening the stop valve, such a pressure can be set even before the start of the suction, and the evaporation is from the beginning at or near the desired temperature. The time between the opening of the stop valve and the beginning of the suction can be several tens of seconds, typically about 60 seconds.

Since the compressor usually takes a certain amount of time to start up and reach its nominal compression capacity at startup, but the refrigerant flow is very rapid when opening the stop valve, the compressor can start at the same moment and the stop valve can be opened , the influx of refrigerant into the evaporator cause a temporary increase in pressure in the evaporator. If this is strong enough to prevent immediate evaporation of refrigerant entering the evaporator, then there is an input of heat into the evaporator. In order to avoid this, it makes sense that at the beginning of a cooling operation phase of the second evaporator, the control unit opens the stop valve only after a start of the compressor.

In order to control the time offset between the start of the compressor and the opening of the stop valve, the control unit may be configured to wait for the stop valve to open until a desired speed of the compressor has been reached. In particular, in speed-controlled compressors representative of the current speed signal is often on the compressor or to an inverter, which supplies the compressor with electrical energy, can be tapped. It is simpler to pre-program a fixed waiting time between the start of the compressor and the opening of the stop valve in the control unit.

In order to be able to store refrigerant in the high pressure region of the refrigerant circuit at the end of a cooling operation phase, with the stop valve already closed, a refrigerant collector may be provided on the refrigerant circuit between an outlet of the compressor and the stop valve. The refrigerant collector may be formed by a chamber inserted into the refrigerant pipe; however, components of the refrigerant circuit which usually serve another purpose may additionally be used as collectors, for example by using tubes of large cross-section for refrigerant lines in the upstream part of the refrigerant circuit or by making a dryer with a larger volume than required for the drying function. Such a dryer will generally only be partially filled with desiccant in order to be able to absorb liquid refrigerant in large quantities.

Subject of the invention is also a refrigerator, in particular a household refrigerator with a refrigerator as described above and with two cooled by the evaporators of the refrigerator storage compartments.

A control unit of this refrigeration device can be set up to cool both compartments successively when cooling is required in one of the compartments, and in this way for a long time

To achieve compressor operating phases.

Preferably, in each of these compressor operating phases, first the second compartment and then the first one is cooled. In this way, since the operating temperature of the second compartment is generally lower than that of the first one, the temperature difference against which the chiller works can be kept smaller than in the opposite order, which in turn contributes to the energy efficiency of the operation.

Whenever cooling is required in one of the two compartments and the other is also cooled, the cooling operation phase of that other compartment generally starts at a lower temperature than that which would determine the cooling requirement of the other compartment. Thus this does not lead to a lowering of the middle

Fachtemperatur and thus in turn leads to increased energy demand is the

Control unit expediently arranged to detect the temperature of the other compartment at the beginning of its cooling operation phase and a temperature of the other compartment in which it terminates this cooling operation phase, based on the detected temperature and a predetermined target temperature of the other compartment, ie individually for each cooling operation phase of the other compartment to set. By making the temperature at which the cooling operation phase ends to be higher, the lower the temperature detected at the beginning of the cooling operation phase of the other compartment, it is possible to keep the mean temperature of the other compartment unchanged. Further features and advantages of the invention will become apparent from the following

Description of embodiments with reference to the accompanying figures. Show it:

Fig. 1 is a schematic representation of the refrigerant circuit of a

Refrigerating appliance according to the invention;

Fig. 2 shows the development over time of electrical power consumption of a

Compressor and evaporation temperature of a normal refrigeration compartment evaporator during operation of the refrigerator of FIG. 1; and

Fig. 3 shows the evolution of the temperature of a compartment of the refrigerator in the course of

Time.

The refrigerant circuit shown in Fig. 1 comprises in a conventional manner

Compressor 1 having a compressed refrigerant outlet 2 and an inlet 3 for sucking refrigerant. At one of the output 2 outgoing

Refrigerant line 4, a condenser 5, a dryer 6, a switchable between an open state and a blocking state stop valve 7 and a directional control valve 8 are arranged in order. Between the condenser 5 and the dryer 8, a frame heater 23 may be inserted into the refrigerant line 4. At the directional control valve 8, the refrigerant line 4 divides into two branches 9, 10.

Deviating from the representation of FIG. 1, the directional control valve 8 can be integrated into the stop valve 7, in that the latter has three instead of two connections and two passage states, wherein in one of the passage states the directional control valve transfers the condenser 5 with the branch 9 and in the other with the branch 10 connects, and in the locked state to none of the branches 9, 10 is a connection.

At the branches 9, 10 are each a capillary 1 1 or 12 and an evaporator 13 and 14 connected in series. Each of the two evaporators 13, 14 cools a compartment 15 or 16 of the refrigeration device. The mean operating temperature of the compartment 15 is higher than that of the compartment 16, for example, the compartment 15 may be a normal refrigerating compartment and the compartment 16 may be a freezing compartment of the refrigerating appliance.

The two branches 9, 10 meet again at a confluence 17. In the branch 10, a check valve 18 is arranged between an outlet of the evaporator 14 and the confluence 17, which allows a flow of refrigerant from the evaporator 14 to the compressor 1, but blocks in the opposite direction.

An electronic control unit 19 is connected to temperature sensors 20, 21 to the

Compartments 15, 16 connected to control the operation of the compressor 1 and the position of the stop valve 7 and the directional control valve 8 based on the temperatures measured there.

The capillary 1 1 of the normal cooling compartment 15 has at a given pressure drop of the

Refrigerant two mass flow rates, a high value for liquid and a low for gaseous refrigerant on. The mass flow rate of Verdichtersl is either, if it is a fixed-speed compressor, given by design or, in the case of a variable speed compressor, through the

Control unit 19 is set to a value which is between the flow rates of the capillary 1 1. As a result, in a cooling operating phase of the evaporator 13, refrigerant vapor accumulates in front of the capillary 11 and condenses. When a drop of the condensate reaches and enters the capillary 11, its mass flow rate increases, and the liquid refrigerant is allowed to pass to the evaporator 13 before a larger amount can accumulate in front of the capillary 11. So change in the course of a

Cooling phase of the evaporator 13 liquid and vapor refrigerant of the capillary 1 1 in rapid succession.

The capillary 12 has a much smaller mass flow rate than the capillary 1 1 at the same pressure drop. The throughput of the capillary 12 is even lower for liquid refrigerant than the throughput of the compressor 1, so that the rate at which refrigerant condenses in the condenser 5, is higher than that with which it can flow through the capillary 12. In order to provide space for the liquid refrigerant, which accumulates in a cooling operation phase of the evaporator 14 in front of the capillary 12, here is the dryer 6 as a

Refrigerant collector 22 is formed, that is, the housing of the dryer 6 is only one Part filled with absorber material, the rest is empty to provide space for the liquid refrigerant.

The control unit 19 can operate according to different methods. A first embodiment of a working procedure result in the control unit

set different target temperatures T _target for both subjects 15, 16. From these target temperatures, the control unit initiates switch- _on temperatures T _on by adding a difference value ΔΤ and switch- _off temperatures T _off by subtracting the

Difference value ΔΤ from: T _on = T _ta rget + AT, T _off = T _ta rget - AT. Cooling demand in one of the

Tray 15, 16 is detected when the tray 15 or 16 associated

Temperature sensor 20 or 21 indicates a temperature greater than T _on . If this is the case, the compressor 1 is turned on, and the temperature in the respective compartment 15 or 16 gradually decreases. If that subject is 15 or 16 on his

Switch-off temperature T _off is cooled, the stop valve closes 7. If it is in the relevant art to the normal refrigerating compartment 15, subsequently, the compressor 1 is still running long enough to to lower the pressure in the evaporator 13 in the vicinity of that pressure, for same time prevails in the directional valve 8 and the check valve 18 disconnected from the circulation of the refrigerant evaporator 14. Thus, even if the check valve 18 does not close perfectly, possibly change a small amount of refrigerant vapor from the evaporator 13 to the evaporator 14 and there release heat by recondensation; on the one hand, because due to the reduced pressure drop at the check valve 18, the amount of leaking steam is low, on the other hand, because at the time of turning off the compressor 1, the amount of refrigerant that is still stored in the evaporator 13, is reduced and therefore not much Refrigerant is available, which could go into the evaporator 14.

If the subject compartment is the freezer compartment 16, then by continuing to operate the compressor 1 after closing the stop valve 7, the amount of refrigerant which could leak through the check valve 18 during the subsequent stoppage phase of the compressor can not be substantially reduced; It can be assumed that after a cooling operation phase of the freezer compartment 16, the evaporator 13 of the

Normal cooling compartment 15 is empty. In this case, the continued operation of the Compressor 1 ensures that the amount of liquid refrigerant that is stored when closing the stop valve 7 in the evaporator 14, and instead refrigerant in the high-pressure region of the refrigerant pipe 4, in particular in the refrigerant collector 22, cached so that it is immediately available when the stop valve 7 is opened due to cooling demand in one of the compartments 15, 16 again.

Alternatively, the compressor 1 could also be switched on at the time when the control unit detects cooling demand of the normal cooling compartment 13, first to fill up the refrigerant collector 22, and only then open the stop valve 7 so that the refrigerant flows into the evaporator 13 in a surge-like manner and the pressure corresponding to a suitable for the normal refrigeration compartment 14 evaporation temperature just below 0 ° C, is achieved in a short time.

In a second, preferred embodiment, the control unit 19 switches on the compressor 1 as soon as it is in one of the compartments 15, 16 that applies to this compartment

Switching temperature T _{on is} exceeded, but then controls, regardless of in which of the compartments 15, 16, the cooling demand has occurred, the directional control valve 8 to connect the capillary 12 with the condenser 5, and so to cool the freezer compartment 16. At this time, the condenser is still at ambient temperature, and the temperature difference between the evaporator 16 and the condenser 5 to be overcome is relatively low.

As can be seen in the lower diagram of FIG

Compressor 1 at time tO first from the temperature T in the evaporator 13, as sucked by the operation of the compressor 1 refrigerant from the evaporator 13 and thereby its evaporation temperature is lowered.

In the case of the time tO, the switching on of the compressor 1 was not caused by the refrigeration requirement of the freezer compartment 16 but of the normal refrigeration compartment 15. The temperature of the freezer compartment was therefore not at the time tO at the time

On temperature T _on , but at a lower value TO, as shown in Fig. 3. This temperature TO is recorded by the control unit 19, and the

Cooling phase of the freezer compartment 16 is not until it reaches its

Off temperature T _off ended, but, as seen in Fig. 3, already for Time t1 at a temperature T1, which is around the value

under the

Target temperature Ttarget is. Thus, when due to refrigeration demand of the refrigerating compartment 15, the freezer compartment 16 is cooled beforehand, the temperature of which only varies by a narrow interval around Ttarget, so that the mean temperature of the freezer compartment 16 further coincides with the target temperature Ttarget, which would not be the case As illustrated in FIG. 3 by a dashed curve, the cooling operating phase would only be terminated when T _{off is reached} .

When the cooling operation phase of the freezing compartment 16 ends when T1 is reached, first, as described above, only the stop valve is closed; the compressor continues to run for some 10 seconds to extract refrigerant from the evaporator 14 and into an upstream part of the refrigerant line, between the outlet 2 and the outlet

Relocate stop valve 7.

Due to the low mass flow rate of the capillary 12, liquid refrigerant has accumulated in front of the capillary 12 during the cooling operation of the freezer compartment 16 between tO and t1 (including the compressor follow-up phase after closing the stop valve 7). If at time t1, the directional control valve 8 is switched to connect the capillary 1 1 with the condenser 5, the liquid refrigerant accumulated in the dryer 6 flows rapidly through the capillary 1 1, it comes to a quick

Pressure increase in the evaporator 13 and, accordingly, to a rapid increase of its evaporation temperature. This decreases again as soon as the supply of dammed liquid refrigerant from the capillary 1 1 is consumed and, from the time t2, liquid refrigerant and refrigerant vapor alternate in the capillary 1 1. The reduced from this time t2 average mass flow rate of the capillary 1 1 leads to a low pressure drop and a corresponding

Lowering the evaporation temperature to a value a few degrees below 0 ° C.

If, at time t3, the normal cooling compartment 15 reaches its switch- _off temperature T _off , the control unit 19 first closes the stop valve 7. Within a few 10 seconds, the pressure in the evaporator 13 drops to a value close to that in the evaporator 14.

Then it turns off the compressor 1. Thereupon, the temperature of the evaporator 13 gradually approaches that of the compartment 15 which it has cooled. However, if the evaporator 13 has been essentially sucked empty before being switched off, the latter remains Pressure difference at the check valve low, and any leakage of refrigerant from the evaporator 13 to the colder evaporator 14 has no significant effect on the heat balance of the refrigerator.

At the time t4, the control unit 19 detects cooling demand in the freezer compartment 16. In this case, the evaporator 1 is operated until the switch- _off temperature T _{off of} the freezer compartment is reached at the time t5. In the case shown in Fig. 2 now the stop valve 7th

closed and soon after the compressor 1 is turned off because the temperature sensor 20 of the normal refrigeration compartment 15 has not detected any refrigeration demand. It would also be conceivable to connect a cooling operation phase of the evaporator 13 here in analogy to what has been described above, wherein in turn, as shown in FIG. 3, the temperature of the

Evaporator 13 is detected at the beginning of its cooling phase, and the

Cooling phase is terminated as soon as the temperature detected by the sensor 20 is just below the target temperature T _ta rget of the normal cooling compartment 15, as it has been at the beginning of the cooling operation phase above.

At time T6 in FIG. 2, cooling demand in the normal cooling compartment 15 is detected again, and the procedure described above is repeated.

A further development of the operating procedure can result if the cooling requirement of the normal refrigerating compartment 15 or the cooling requirement of the freezing compartment 16 is detected at the time t 0, although the compressor 1 is switched on immediately, but this remains

Stop valve 7 closed for a while, so even if in the

previous standstill phase of the compressor 1 refrigerant vapor over the

Check valve 18 has passed from the evaporator 13 into the evaporator 14, the pressure in both evaporators 13, 14 is again lowered far enough to ensure that refrigerant, which is admitted at the moment of opening the stop valve 7 in the evaporator 14 of the freezer compartment 16, evaporates from the outset at a temperature not higher than the actual temperature of the evaporator 14. REFERENCE NUMBERS

compressor

output

entrance

Refrigerant line

condenser

dryer

stop valve

way valve

branch

capillary

Evaporator

subject

confluence

check valve

control unit

temperature sensor

Refrigerant collector

Rail heat

Claims

Refrigerating machine with a compressor (1), a first and a second

Evaporator (13, 14), which are arranged together with a respective upstream capillary (1 1, 12) in mutually parallel branches (9, 10) of a refrigerant circuit (4), wherein in a downstream part of the refrigerant circuit (4) between outputs of the Evaporator (13, 14) and an input (3) of the compressor (1) a valve (18) for blocking a flow of refrigerant from the first evaporator (13) to the second evaporator (14) is arranged, characterized in that in an upstream part of the Refrigerant circuit (4) between an output (2) of the compressor (1) and inputs of the evaporator (13, 14) a stop valve (7) is arranged and a control unit (19) is arranged, at the end of a cooling phase of at least one of the two evaporators ( 13, 14) to operate the compressor (1) with the stop valve (7) closed.

Chiller according to claim 1, characterized in that the control unit (19) is arranged to close the stop valve (7) 30-120 s before the end of the cooling operation phase.

Chiller according to claim 1 or 2, characterized in that the at least one evaporator is the first evaporator (13).

Chiller according to claim 1 or 2, characterized in that the at least one evaporator is the second evaporator (14).

Chiller according to claim 4, characterized in that at an output of the second evaporator (14), a temperature sensor (21) is arranged and the control unit (19) is arranged, the time period between the

Closing the stop valve (7) and the end of the cooling operation phase of the second evaporator (14) based on the detected by the temperature sensor (21)

Temperature to regulate. A refrigerating machine according to claim 4, characterized in that the control unit (19) is connected to an ambient temperature sensor and is arranged to determine the time span between the closing of the stop valve (7) and the end of the cooling operating phase of the second evaporator (14)

Ambient temperature and / or the time elapsed since the beginning of the cooling operation phase.

Chiller according to one of the preceding claims, characterized

characterized in that the control unit (19) is arranged to open the stop valve (7) before the beginning of a cooling operation phase of the first evaporator (13).

Chiller according to one of the preceding claims, characterized

characterized in that the control unit (19) is arranged to open the stop valve (7) after a start of the compressor (1) at the beginning of a cooling operation phase of the second evaporator (14).

Chiller according to claim 8, characterized in that the control unit (19) is adapted to open the stop valve (7) at the earliest when a fixed waiting time has elapsed since the start of the compressor (1) or the compressor (1) a predetermined speed has reached.

Chiller according to one of the preceding claims, characterized

characterized in that a refrigerant collector (22) is provided on the refrigerant circuit (4) between an outlet of the compressor (1) and the stop valve (7).

Refrigerating appliance, in particular household refrigerating appliance, with a refrigerating machine according to one of the preceding claims and with two storage compartments (15, 16) cooled by the evaporators (13, 14), characterized in that the control unit (19) is set up with cooling demand in one of the storage compartments (15) both

Storage compartments (15, 16) to cool gradually.

Refrigerating appliance according to claim 1 1, characterized in that the control unit (19) is adapted to the temperature (TO) of the other compartment (16) To detect the beginning (tO) of its cooling operation phase and a temperature (T1) of the other compartment (16) at which it terminates this cooling operation phase, based on the detected temperature (TO) and a target temperature (T _ta rget) of the other compartment (16) set.

Refrigerating appliance according to claim 1 1 or 12, characterized in that the

Control unit (19) is arranged, in an operating phase of the compressor (1) first to cool the second compartment (16) and then the first compartment (15).