EP3599434A1 - Single circuit refrigerator - Google Patents

Abstract

In a single-circuit refrigerator (10) with a first and a second storage zone (12, 14), a compressor (24) follows one another along a refrigerant line between a pressure connection (26) and a suction connection (28): one condenser (30), one Throttle point (32), a first evaporator (34) for cooling the first storage zone (12) and a second evaporator (36) for cooling the second storage zone (14). A thermal mass (56) is predominantly arranged on a downstream region of the condenser (30) in contact with the condenser (30).

Description

The present invention relates to a single-circuit refrigerator with two storage zones to be kept at different operating temperatures, such as a normal refrigerator compartment and a freezer compartment. In such a refrigeration device, evaporators of the two temperature zones are connected in series in a refrigerant circuit, so that the mass flow of the refrigerant through the two evaporators is the same. In such a refrigerator, different operating temperatures of the two storage compartments can result from different dimensions of the two evaporators and from the fact that only the refrigerant that has passed through the first evaporator in liquid form can evaporate in the second evaporator.

A known disadvantage of such single-circuit refrigeration devices is that the distribution of the available cooling capacity over the various storage zones can hardly be changed, but that the ratio of the cooling capacities that are required for maintaining the operating temperatures in the two storage zones depends on the ambient temperature. If this decreases, this affects the cooling capacity requirement of the warmer temperature zone more than that of the colder one, and there is a risk that if the refrigeration is regulated on the basis of the temperature of the warmer temperature zone, insufficient refrigeration will be generated to cool the colder one to keep the two temperature zones at their operating temperature.

A common approach to solving this problem is to install a heat source in the warmer temperature zone that can be operated at a low ambient temperature in order to ensure a longer compressor runtime, which is also sufficient for sufficient cooling of the colder storage compartment. The operation of such a heat source inevitably affects the energy efficiency of the refrigerator.

Out WO 2013/013997 A1 A single-circuit refrigeration device is known in which a thermal mass is attached to the refrigerant line of a condenser in order to absorb heat that is released during the condensation of the refrigerant when the compressor is running and to release it to the environment during a standstill phase of the compressor. Furthermore, the free cross section of the refrigerant line is by deforming or inserting of a foreign body is narrowed to reduce the amount of liquid refrigerant stored in the condenser.

The object of the invention is to provide a single-circuit refrigeration device in which the heat source can be dispensed with or at least the frequency with which the heat source must be operated is reduced, or the range of the ambient temperature in which the refrigeration device can be operated without that the heat source is needed is enlarged.

The object is achieved in a single-circuit refrigeration device with a first and a second storage zone, in which a compressor follows one another along a refrigerant line between a pressure connection and a suction connection: a condenser, a throttle point, a first evaporator for cooling the first storage zone and a second evaporator for cooling the second storage zone, and with a thermal mass arranged in contact with the condenser, the thermal mass is predominantly arranged at a downstream region of the condenser.

To achieve condensation of the refrigerant in the condenser, the pressure in the condenser must be higher than the vapor pressure of the refrigerant at the temperature that the refrigerant has reached at the evaporator outlet. Consequently, the condensation of the refrigerant takes place predominantly in an upstream region of the condenser, while it cools down to the boiling temperature corresponding to the prevailing pressure; In comparison, in a downstream area of the condenser, through which the refrigerant then passes, only a little heat is released. At high ambient temperatures, the thermal mass has little influence on the liquid refrigerant, because the amount of liquid refrigerant that collects in the downstream area of the condenser and can give off heat to the thermal mass decreases on average with increasing ambient temperature. At low ambient temperatures, however, the increased heat emission in contact with the thermal mass leads to the boundary between the part of the condenser in which the condensation takes place and the part where the supercooling takes place being shifted upstream and thus the amount of liquid refrigerant at the downstream end of the condenser. In the context of the present invention, this allegedly undesirable effect leads to the amount of refrigerant available in the evaporators being reduced and thereby making it possible for the Distribution of the liquid refrigerant - and thus the distribution of the cooling capacity - to the evaporators of the two storage zones depending on the ambient temperature.

A low ambient temperature means that the cooling capacity requirement in the warmer of the two storage zones decreases proportionally more than in the colder one. If the compressor is controlled by a temperature sensor located in the warmer of the two storage zones, this can result in the colder storage zone not being cooled sufficiently. However, if this is the first of the two storage zones, a reduced supply of the evaporator with liquid refrigerant at a low ambient temperature will result in enough liquid refrigerant only after an extended compressor runtime (or, in the case of a speed-controlled, continuously running compressor, at an increased delivery rate) reaches the second evaporator to keep the second storage zone at its operating temperature. This means that more liquid refrigerant is available for the first evaporator, and the interval of the ambient temperatures in which both temperature zones can be kept at their operating temperatures without heating of the second temperature zone being increased.

A refrigerant pipe that extends through the condenser from an inlet to an outlet must not be in contact with the thermal mass over its entire length, but should be in contact with the thermal mass over at least a quarter of its length in order to be able to form a sufficiently long supercooling zone.

The quarter can be distributed over several sections of the refrigerant pipe, between which the contact with the thermal mass is interrupted; Such an interruption can, as described in more detail below, be found in particular on the elbows of the refrigerant pipe. Preferably, a single section extends continuously over at least a quarter of the length of the refrigerant tube in contact with the thermal mass.

Conversely, the refrigerant pipe should run at least a quarter of its length without contact with the thermal mass in order to allow the heat of condensation to be released directly to the environment. This quarter is also here Length is preferably formed by a single section of the refrigerant tube which extends continuously without contact with the thermal mass.

If the condenser is in the form of a plate and is installed in the refrigerator in a vertically elongated orientation, then in particular an upper half of the condenser should be free of the thermal mass in order to allow the heat of condensation to be released; the thermal mass, however, should be concentrated in a lower half of the condenser in order to absorb the supercooling heat of the liquid refrigerant collecting there.

A shut-off valve can be provided in the refrigerant line between the condenser and the first evaporator in order to prevent pressure equalization between the condenser and the evaporator during a standstill phase of the compressor. This prevents warm refrigerant from the condenser from reaching the first evaporator towards the end of a pressure equalization; on the other hand, the efficiency of refrigeration increases because the pressure difference between the condenser and evaporator does not have to be rebuilt each time the compressor is started.

If the flow rate of the compressor can be adjusted to several non-vanishing values, i.e. especially if it is a speed-controlled compressor, the throughput of the compressor can be set so that the compressor does not come to a standstill as long as the refrigeration device is not completely switched off. In such a case, the shut-off valve is not required to maintain the pressure difference between the condenser and the compressor.

The thermal mass can comprise bitumen, possibly with fillers such as a mineral powder.

If the thermal mass is plastic at elevated temperature, it can be attached to the condenser in a simple manner by pressing a refrigerant tube of the condenser into the heated thermal mass and allowing the thermal mass to cool.

The thermal mass can be in the form of a rectangular blank, at least one edge length of which is smaller than a corresponding edge length of the condenser, so that when the blank is placed on the plate-shaped condenser, the refrigerant tube of the condenser is only at a part of its length with the thermal Mass can come into contact.

In order to increase the amount of liquid refrigerant bound in the condenser at a low ambient temperature, it is also advisable to select a throttling point with a low throughput. For a household refrigeration appliance of the size customary on the market, this value - measured with nitrogen gas at a pressure difference of 6 bar - should not exceed 150 l / min.

A frame heater can be inserted in the refrigerant line between the condenser and the throttle point; This can also help to collect liquid refrigerant at low ambient temperatures and keep it away from the evaporators.

Fig. 1

eine schematische Darstellung eines erfindungsgemäßen Kältegeräts;

Fig. 2

eine Draufsicht auf den Verflüssiger des Kältegeräts;

Fig. 3

eine Draufsicht auf den Verflüssiger gemäß einer Abwandlung; und

Fig. 4

einen Schnitt durch den Verflüssiger.

Further features and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. Show it:

Fig. 1

is a schematic representation of a refrigerator according to the invention;

Fig. 2

a plan view of the condenser of the refrigerator;

Fig. 3

a plan view of the condenser according to a modification; and

Fig. 4

a section through the condenser.

Fig. 1 shows a single-circuit household refrigeration device 10 with a first, colder storage zone 12, here a freezer compartment and a second, warmer storage zone 14, here a refrigerator compartment. The refrigerator 10 has a heat-insulated housing 16 with housing walls 17 which, together with heat-insulated doors 18, delimit interior spaces 20 of the storage zones 12 and 14.

A refrigerant circuit 22 is arranged on the refrigeration device 10 for cooling the interior 20. This refrigerant circuit 22 comprises a compressor 24 and, along a refrigerant line 27 extending from a pressure connection 26 to a suction connection 28 of the compressor 24, a condenser 30, a throttle point 32 designed as a capillary or as an expansion valve, a first evaporator 34 cooling the first storage zone 12 and a second evaporator 36 that cools the second storage zone 14.

An electronic control unit 38 is connected to a temperature sensor 40 arranged on the cooling compartment 14 in order to control the compressor 24 on the basis of the temperature prevailing in the cooling compartment 14.

The compressor 24 may be speed controlled, i.e. it can be operated at a plurality of non-disappearing speeds, and is preferably operated at a speed at which it covers the cooling requirement of the cooling compartment 14 exactly and can be operated non-stop with small fluctuations.

Alternatively, compressor 24 may be on / off controlled; in this case there is preferably an in between the condenser 30 and the first evaporator 34 Fig. 1 provided with 33 indicated shut-off valve, which is closed by the control unit 38 in a standstill phase of the compressor 24 in order to prevent pressure equalization between the condenser 30 and the evaporators 34, 36.

The throttle point 32 has a low throughput of 120 l / min N ₂ gas at a pressure difference of 6 bar compared to conventional refrigeration devices of the same size. This low throughput favors the build-up of liquid refrigerant in front of the throttle point 32 and at the same time leads to a shortage of the liquid refrigerant behind the throttle point 32. This shortage is greater the lower the ambient temperature, and leads to the fact that liquid refrigerant is already at a low ambient temperature mostly evaporates in the evaporator 34, and the portion that reaches the evaporator 36 and cools the storage zone 14 becomes less and less as the ambient temperature decreases. The result is that a long run time of the compressor 24 (or a high speed of the compressor) are required to achieve a ensure sufficient supply of the evaporator 36, and that in this way there is also sufficient cooling capacity for the colder storage zone 12.

The throttle point 32 can be connected to the condenser 30 or the shut-off valve 33 directly or, as in FIG Fig. 1 indicated by a dashed line, connected via a frame heater 31, in which the refrigerant line 27 extends within the insulating housing walls 17 in each case adjacent to the front edges facing the doors 18.

The condenser 30 is plate-shaped and deviates from the illustration in FIG Fig. 1 , mounted on a rear wall of the housing 16. It comprises a refrigerant tube 42, which is inserted, for example soldered, into the refrigerant line 27 at an inlet 42 and an outlet 44, extends in one piece between the inlet 43 and the outlet 44 and on which a plurality of straight horizontal tube segments 46 and the tube segments 46 extend alternate connecting arches 48.

In the Fig., 2 and 3 In the embodiment shown, the refrigerant tube 42 further comprises a riser tube 50, which connects the inlet 43 facing the compressor 24 housed in a machine room near the bottom of the housing 16 to an apex of the refrigerant tube 42, and the horizontal tube segments 46 and the bends 48 run from the apex to the outlet 44 descending.

The horizontal tube segments 46 are connected in a manner known per se through wires 52 arranged to cross them, in order to stiffen the condenser 30 and to enlarge its heat-emitting surface. The ascending pipe 50 has an arc 54 extending laterally, to which some of the wires 52 are also fastened in order to fix the ascending pipe 50.

In a lower region of the liquefier 30, a rectangularly cut bitumen film or plate is pressed against the refrigerant pipe 42 in the heated state as a thermal mass 56, so that its lowermost horizontal pipe segments 46 and the bends 48 connecting them run in contact with the bitumen without interruption Form section 49. These pipe segments 46 and elbows 48 take up about 30% of the effective length of the condenser (the riser 50 contributes to this Heat dissipation of the condenser 30 less than the proportion proportional to its length, since the crossing wires 52 are missing on a large part of its length). Since they are located in the lower half of the condenser 30, liquid refrigerant collects there from parts of the refrigerant tube 42 located further upstream and undercools there.

The bituminous sheet or plate, which acts as thermal mass 56, extends over the entire width of the horizontal pipe segments 46 and arches 48. At the level of the bituminous sheet or plate there are two shortened horizontal segments 46 'and an inwardly offset sheet 48 to make room for the bend 54 of the ascending pipe 50. This also runs in contact with the bitumen film or plate here, but is too short to noticeably influence the condensation of the refrigerant.

At the in Fig. 3 In the embodiment of the condenser 30 shown, the course of the refrigerant tube 42 and the arrangement of the wires 52 are the same as in FIG Fig. 2 , The width of the bitumen film or plate is reduced, so that the arch 54 of the riser 50 crosses and is attached to some of the wires 52, but does not contact the thermal mass 56. The rectangular shape of the bitumen film or plate means that the arcs 48 facing the riser pipe 50 have no contact with the thermal mass 56 and the part of the refrigerant pipe 42 that is in contact with it disintegrates into several sections, each over one over the other Edge 48 of the thermal mass 56 projecting.

Alternatively, there is the possibility of cutting a cutout on a narrow side of the bitumen film or plate, on the one hand to make a gapless heat-conducting contact between the downstream end section of the refrigerant tube 42 and on the other hand to avoid such a contact with the bend 54.

Fig. 4 shows a section through a horizontal pipe segment 46 in contact with the bitumen-extending section 49 of the liquefier 30. The bitumen film or plate functioning as a thermal mass 56 is molded onto the raw segment 46 from a side opposite the wires 52 and lies on a part of the latter of its scope. The bitumen film or plate is preferably molded onto the condenser 30 so closely that the bitumen also comes into contact with the wires 52 or even in Gaps between the wires 52 penetrate, so that heat that initially flows out of the refrigerant in the pipe segment 46 to a side facing away from the bitumen film or plate can also be introduced into the thermal mass 56 via the wires 52.

REFERENCE NUMBERS

10

The refrigerator

12

first storage zone (freezer)

14

second storage zone (refrigerator compartment)

16

casing

17

housing wall

18

door

20

inner space

22

Refrigerant circulation

24

compressor

26

pressure connection

27

Refrigerant line

28

suction

30

condenser

31

Rail heat

32

restriction

33

shut-off valve

34

first evaporator

36

second evaporator

38

control unit

40

temperature sensor

42

Refrigerant pipe

43

inlet

44

outlet

46

horizontal pipe section

48

arc

49

section

50

riser

52

wire

54

arc

56

Bitumen film or sheet

Claims (15)

Single-circuit refrigeration device (10) with a first and a second storage zone (12, 14), in which a compressor (24) follows one another along a refrigerant line (27) between a pressure connection (26) and a suction connection (28): a condenser ( 30), a throttle (32), a first evaporator (34) for cooling the first storage zone (12) and a second evaporator (36) for cooling the second storage zone (14), and one in contact with the condenser (30) arranged thermal mass, characterized in that the thermal mass (56) is arranged predominantly on a downstream region of the condenser (30). Single-circuit refrigerator according to claim 1, characterized in that the compressor (24) is controlled by a temperature sensor (40) arranged in the warmer of the two storage zones (14). Single-circuit refrigerator according to claim 1 or 2, characterized in that the first storage zone (12) is the colder of the two storage zones (12, 14). Single-circuit refrigerator according to one of the preceding claims, characterized in that a refrigerant tube (42) extending through the condenser (30) from an inlet (43) to an outlet (44) is in contact with the thermal mass over at least a quarter of its length (56) runs. Single-circuit refrigerator according to Claim 4, characterized in that a section (49) of the refrigerant tube (42) which extends continuously in contact with the thermal mass (56) occupies at least a quarter of the length of the refrigerant tube. Single-circuit refrigerator according to claim 4 or 5, characterized in that the refrigerant tube (42) extends over at least a quarter of its length without contact with the thermal mass (56). Single-circuit refrigerator according to one of claims 4 to 6, characterized in that a continuously without contact with the thermal mass (56) extending portion of the refrigerant tube (42) occupies at least a quarter of the length of the refrigerant tube (42). Single-circuit refrigerator according to one of the preceding claims, characterized in that the condenser (30) is installed in the form of a plate and in a vertically elongated orientation, and in that an upper half of the condenser (30) is free of the thermal mass (56). Single-circuit refrigerator according to one of the preceding claims, characterized in that a shut-off valve (33) is provided in the refrigerant line (27) between the condenser (30) and the first evaporator (34). Single-circuit refrigerator according to one of the preceding claims, characterized in that the throughput of the compressor (30) can be set to a plurality of non-vanishing values. Single-circuit refrigerator according to one of the preceding claims, characterized in that the thermal mass (56) comprises bitumen. Single-circuit refrigerator according to one of the preceding claims, characterized in that the thermal mass (56) is plastic at elevated temperature and a refrigerant tube (42) of the condenser (30) is pressed into the thermal mass (56). Single-circuit refrigerator according to one of the preceding claims, characterized in that the thermal mass (56) is a rectangular blank and that at least one edge length of the blank is smaller than a corresponding edge length of the condenser (30). Single-circuit refrigeration device according to one of the preceding claims, characterized in that the throttle point (32) has a throughput of at most 150 l / h, measured with nitrogen gas at a pressure drop of 6 bar. Single-circuit refrigerator according to one of the preceding claims, characterized in that a frame heater (31) is inserted between the condenser (30) and the throttle point (32) in the refrigerant line (27).

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