Domestic refrigeration device with two evaporators

Abstract

A domestic refrigeration appliance (10) with a first storage area (15) with a first setpoint temperature and a second storage area (16) with a second setpoint temperature lower than the first setpoint temperature, has a refrigerant circuit comprising a first evaporator (20, 20', 20") for cooling the first storage area and a second evaporator (30) for cooling the second storage area, the second evaporator (30) being connected in series with the first evaporator (20, 20', 20") in the refrigerant circuit. The first evaporator (20, 20', 20") has a refrigerant-side surface for heat exchange with refrigerant circulating in the refrigerant circuit and an air-side surface for heat exchange with the first storage area (15).The ratio of refrigerant-side surface area to air-side surface area of ​​the first evaporator (20, 20', 20") is in the range of 0.12 to 0.25, where the first evaporator (20, 20', 20") is a plate evaporator on a rear wall (19) of the first storage area (15). The air-side surface area of ​​the first evaporator (20, 20', 20") is less than 60% of the area available on the rear wall (19) of the first storage area (15). The refrigerant pipe cross-section is less than 18 mm².

Description

[0001] The present invention relates to a domestic refrigeration appliance with a first storage area having a first setpoint temperature and a second storage area having a second setpoint temperature that is lower than the first setpoint temperature, and with a refrigerant circuit comprising a first evaporator for cooling the first storage area and a second evaporator for cooling the second storage area, the second evaporator being connected in series with the first evaporator in the refrigerant circuit. A refrigeration appliance with multiple temperature zones is known from DE 10 2016 224 434. Further refrigeration appliances are described in JP 2009 074769 A, DE 10 2016 224434 A1, CN 102 519 201 A, DE 17 51 070 A1 and EP 3 599 434 A1.

[0002] The object of the present invention is to create a household refrigeration appliance with two storage areas and evaporators assigned to the storage areas, wherein the second evaporator is assigned to the compartment with a lower setpoint temperature than the first compartment and is connected in series with the first evaporator in a refrigerant circuit, in which the storage area with higher temperature has improved temperature stratification and whose evaporator requires little effort.

[0003] The problem is solved by a household refrigeration appliance according to claim 1. The invention relates to a household refrigeration appliance with a first storage area with a first setpoint temperature and a second storage area with a second setpoint temperature that is lower than the first setpoint temperature, a refrigerant circuit comprising a first evaporator for cooling the first storage area and a second evaporator for cooling the second storage area, wherein the second evaporator is connected in series with the first evaporator in the refrigerant circuit in the direction of refrigerant flow. Each evaporator has a refrigerant-side surface for heat exchange with refrigerant circulating in the refrigerant circuit and an air-side surface for heat exchange with the storage area associated with the evaporator. The ratio of refrigerant-side surface area to air-side surface area of ​​the first evaporator is in the range of 0.12 to 0.25.

[0004] The first evaporator is a plate evaporator located on a rear wall of the first storage area and has a refrigerant pipe with a cross-sectional area of ​​less than 18 mm². The first storage area includes an upper sub-storage area where the domestic refrigeration appliance is not equipped with storage trays, and the air-side surface area of ​​the first evaporator is less than 75% of the surface area available on the rear wall of the upper sub-storage area.

[0005] The plate evaporator has a continuous downward slope in the direction of refrigerant flow. This assists the refrigerant flow through gravity.

[0006] A household refrigeration appliance is specifically one in which typical household quantities of food are stored in different compartments at varying temperatures and may undergo temperature treatment. Evaporators operating at different temperatures allow the storage compartments to be maintained or operated at these varying temperatures.

[0007] While the aforementioned prior art in a refrigeration unit with two storage areas with serially arranged evaporators provides good cooling performance and good heat transfer in the warmer compartment with little effort for the upstream evaporator, this invention aims at a further improved temperature stratification by designing the heat transfer at different heights of the warmer compartment.

[0008] The refrigerant-side surface area is the inner surface area of ​​the refrigerant tube and, for a round tube cross-section, can be determined from the inner diameter and length of the tube on the evaporator plate. The air-side surface area is the area of ​​the evaporator plate.

[0009] The pipe cross-section smaller than 18 mm² is the cross-sectional area enclosed by the pipe wall through which the refrigerant flows. This cross-sectional area is smaller than the typical cross-sectional area of ​​refrigerant pipes in modern household refrigeration appliances.

[0010] Due to the efficient heat transfer of the first evaporator, it is not necessary for the evaporator in the domestic refrigeration appliance to occupy the entire surface of the rear wall of the first storage area, or even of the upper storage area. The air-side surface area of ​​the evaporator is less than 75%, preferably less than 65%, and even more preferably less than 55%, of the surface area available on the rear wall of the upper storage area.

[0011] The household refrigerator may be equipped with storage trays in a lower section of the primary storage area. These trays may be intended for storing vegetables or as a cold storage area. While these storage trays are considered part of the primary storage area in terms of temperature, they may have their own set temperatures that differ from the average set temperature of the primary storage area by a few degrees Celsius.

[0012] Preferably, these optional bearing shells are not cooled by an evaporator located in the rear wall directly behind the shells, but by the first evaporator via a suitable air guide.

[0013] According to one embodiment of the invention, the width of the first evaporator is less than 80% of the width of the first storage area. In the first storage area, typically a refrigerated compartment, a desired temperature distribution can be achieved with a sufficient evaporator height by utilizing the surface area reduction provided by an evaporator that is narrower than the rear wall.

[0014] By selecting a thinner refrigerant tube than usual, preferably with an outer diameter of 5 mm or less, a longer refrigerant tube than usual is required to achieve the required ratio of refrigerant-side surface area to air-side surface area in the first evaporator. This increased tube length is used to cool different areas of the evaporator plate differently by arranging loops of the tube.

[0015] Preferably, the top of the evaporator abuts the ceiling of the first storage area. The ceiling encompasses any possible curve in an edge between the back wall and the ceiling. This allows for intensive cooling of the warmest region of the first storage area under natural convection conditions.

[0016] Preferably, the injection point is arranged to the side of the evaporator, with the advantage of a well-cooled upper corner of the evaporator.

[0017] Preferably, the plate evaporator has an injection point near an upper edge. This assists the flow of the refrigerant through gravity.

[0018] The injection area is preferably inclined in order to impose a clear direction on the very slow refrigerant flow at this point, in addition to gravity.

[0019] In a further embodiment of the invention, the entire pipe path from the injection point of the upstream evaporator to the beginning of the downstream evaporator is designed to slope downwards in order to avoid unintentional refrigerant accumulation in any pipe areas.

[0020] According to a preferred embodiment of the invention, the pipe routing of the first evaporator is denser in a zone in the flow direction shortly after the injection point than in the pipe sections below. With the greater pipe length per evaporator surface shortly after the injection point compared to the lower regions of the evaporator, a nearly homogeneous temperature distribution across the evaporator surface can be achieved, with the further advantage of uniform frost loading of the evaporator.

[0021] The advantage is the pipe routing of the plate evaporator below the zone where the density is steadily reduced.

[0022] Preferably, the pipe routing of the plate evaporator is implemented below the zone with continuously decreasing horizontal width using pipe meanders.

[0023] According to a preferred embodiment of the invention, the continuous downward slope of the pipe in the direction of refrigerant flow is greater than 2°.

[0024] The plate evaporator is preferably a rollbond evaporator, a tube-on-sheet (TOS) evaporator, or a tube-on-foil (TOF) evaporator.

[0025] A bearing shell may be arranged below the first bearing area, wherein a lower edge of the plate evaporator is arranged at least 50 mm above an upper edge of the bearing shell.

[0026] Preferably, the lower edge of the plate evaporator is arranged no more than 200 mm above an upper edge of the bearing shell.

[0027] A preferred embodiment of the invention is a household refrigeration appliance in the form of a refrigerator-freezer combination with a cold storage compartment and a freezer compartment. In this configuration, the first evaporator in the refrigerant circuit (in the direction of flow) is assigned to the cold storage compartment, and the second evaporator in series is assigned to the freezer compartment.

[0028] In this refrigerator, when the refrigerator compartment evaporator is operating, liquid refrigerant flows rapidly through the upstream evaporator, and the freezer compartment evaporator is well filled with liquid refrigerant. Since there is no restrictor between the refrigerator and freezer compartment evaporators, their evaporation pressures and temperatures are approximately the same.

[0029] A preferred configuration of the refrigerator-freezer combination is a so-called bottom freezer with a refrigerated storage compartment at the top and a frozen storage compartment below. Here, the connection between the evaporators can preferably be made with a continuous downward slope, preventing refrigerant accumulation between them. The evaporator tube layout can be designed so that the tube end on the refrigerator compartment evaporator is positioned on the opposite side from the connecting tube. This allows for length compensation through the free routing of the tube, which is helpful during assembly in manufacturing.

[0030] One version of such a refrigeration unit contains the first and second evaporators in series without a refrigerant line connecting them. This design describes a refrigeration unit in which both evaporators always operate simultaneously and are supplied with the same amount of refrigerant. This design avoids branching and requires fewer valves in the refrigerant circuit.

[0031] In this refrigeration unit, only the warmer storage compartment can be equipped with a temperature sensor and controlled. The unit is then typically designed so that the set temperature of the colder compartment is usually only slightly undershot. The invention improves the filling of the downstream evaporator with liquid refrigerant in this refrigeration unit, particularly after a compressor start-up. Since both evaporators are operated simultaneously, thus achieving an energy-efficient utilization of the entire heat exchanger surface area, the unit operates very efficiently.

[0032] A second variant of such a refrigeration unit contains the first and second evaporators in series with a refrigerant pipe inlet between them. This configuration describes a refrigeration unit in which both evaporators in a first circuit are always operated simultaneously and are supplied with the same amount of refrigerant. In a second circuit, only the downstream evaporator is operated.

[0033] In this refrigeration unit, both storage compartments can be equipped with their own temperature sensors and controlled independently. Most of the time, both evaporators operate in series; however, the evaporator of the colder storage compartment can occasionally be operated alone to precisely maintain its target temperature. This further improves energy efficiency, as the colder compartment is always operated at its target temperature.

[0034] When both evaporators are operated in series, fans in one or both bearing areas or on one or both evaporators can be used to slightly adjust the bearing areas with regard to their target temperatures.

[0035] Another embodiment of the first variant of the refrigeration unit features a fan on the evaporator of the upstream compartment, and a control system that reduces the speed of its fan at low ambient temperatures and / or increases its speed at high ambient temperatures.

[0036] Another embodiment of the first version of the refrigeration unit features a fan on the evaporator of the downstream compartment and a controller that regulates its fan speed. This extends the control range within which the target temperatures of both storage areas can be maintained simultaneously in series operation of the evaporators.

[0037] The household refrigeration unit can have a lower storage area with storage trays in the first storage section. The lower storage area, including the trays, is cooled by the first evaporator in the upper storage area. The household refrigeration unit can advantageously be designed so that a cold airflow is created at the rear wall in front of the evaporator, which flows along the rear wall towards the storage trays.

[0038] Further features and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying figures. These show: Fig. 1 a schematic representation of a household refrigeration appliance according to the invention; Fig. 2 a schematic representation of the arrangement of evaporators of a household refrigeration appliance according to the invention; and Fig. 3 a schematic representation of a plate evaporator of a household refrigeration appliance according to the invention.

[0039] In the various embodiments, functionally identical elements are designated with the same reference numerals, similar elements with hyphenated reference numerals.

[0040] In Fig. 1 A household refrigeration appliance 10 is shown as a refrigerator-freezer combination, the heat-insulating housing 11 of which has two first and second storage areas 15, 16, thermally separated from each other by a heat-insulating partition 12, arranged vertically one above the other and closable with separate doors 13 and 14. The uppermost first storage area 15, closable with the door 13, is designed as a refrigerator compartment, which is equipped with shelves 17 arranged vertically above one another for storing refrigerated goods.

[0041] The other storage area 16, located below the cooling compartment and separated from it by the heat-insulating partition 12, is designed as a freezer compartment, which has drawer-like extendable freezer containers 18 for holding frozen goods.

[0042] Both the refrigerator compartment and the freezer compartment are equipped with evaporators to maintain their intended storage temperature. Evaporator 20 of the first storage area 15 is indicated as a plate evaporator on a rear wall 19 of the first storage area 15. The evaporators are integrated into a refrigeration circuit (not shown) within which a compressor is located that supplies the evaporators with liquid refrigerant.

[0043] The first storage area 15 has an upper partial storage area 28, in which the household refrigeration appliance 10 is not equipped with bearing shells, and a lower partial storage area 29, in which bearing shells 21 are arranged. The bearing shells 21 are closed by a cover 22. The distance 23 from the cover 22 to the lower edge of the evaporator 20 is between 50 and 200 mm.

[0044] The width 24 of the evaporator 20 is less than 80% of the width 25 of the rear wall 19 of the first storage area 15.

[0045] The evaporator plate 27 of the first evaporator 20 faces the first storage area with its air-side surface in order to cool the air of the first storage area. The air-side surface of the evaporator plate 27, or of the first evaporator 20, is less than 60% of the area of ​​the rear wall 19 of the first storage area 15.

[0046] Fig. 2 shows an arrangement of first evaporator 20' and second evaporator 30 of the household refrigeration appliance 10. Fig. 1 .

[0047] The first evaporator 20' is designed as a tube-on-sheet (TOS) evaporator with a refrigerant tube 31 on an evaporator plate 27'. The evaporator plate 20' is arranged on a rear wall 19' of the first storage area 15, wherein the width 24' of the evaporator plate 27' is less than 80% of the width 25' of the rear wall 19'.

[0048] The evaporator 20' can be arranged behind a wall of an inner container with the refrigerant pipe coming from the side facing away from the inner container.

[0049] An injection point 34 is located laterally outside the upper right corner of the evaporator plate 27'. The refrigerant pipe 31 extends beyond the evaporator plate 27' at its upper right corner. The pipe routing on the evaporator plate is more densely implemented in a zone 33 shortly after an injection point 34 than in the subsequent pipe sections.

[0050] A continuous downward slope of the refrigerant pipe 31 is maintained to prevent refrigerant accumulation due to gravity in this pipe section. The continuously descending pipe design generally avoids the need for nested pipe meanders. This results in a relatively simple pipe layout from a manufacturing perspective.

[0051] In the case of the refrigerant pipe 31, a connecting section 37 to the second evaporator 30 is connected to the evaporator outlet 36 and runs at a continuous incline. The refrigerant pipe 31 can have a different diameter in the section on the evaporator plate 27' than in the connecting section 37.

[0052] The evaporator 30 can be a finned evaporator or a coiled evaporator.

[0053] A first capillary 38 runs in an insulating material to the injection point 34.

[0054] In Fig. 2 An optional second capillary 39 is shown, which opens into the refrigerant pipe 31 at the junction 32 and forms an injection point 40 in the refrigerant pipe 31 at the inlet of the second evaporator 30. The optional second capillary 39 enables a two-circuit refrigeration unit with a so-called intermediate injection of refrigerant into the downstream evaporator.

[0055] Fig. 3 shows a further embodiment of the first evaporator 20" with several independent modifications compared to the first evaporator 20'. Fig. 2 .

[0056] The injection point 34' of the refrigerant pipe 31' is now no longer on the side, but above the evaporator plate 27".

[0057] Below zone 33', the pipe layout becomes progressively less dense. On the one hand, the horizontal width of the pipe meanders steadily decreases. On the other hand, the pipe meanders are pulled apart vertically, so that their vertical spacing becomes increasingly larger.

[0058] The first evaporator 20" has a downwardly tapered evaporator plate 27". REFERENCE MARK LIST

[0059] 10 Household refrigeration appliance 11 Casing 12 Partition wall 13, 14 Door 15 First storage area 16 Second storage area 17 Shelf 18 Freezer compartment 19, 19' Rear wall 20, 20', 20" First evaporator 21 Storage tray 22 Cover 23 Spacing 24, 24', 25 Width 27, 27' Evaporator plate 28 Upper partial storage area 29 Lower partial storage area 30 Second evaporator 31, 31' Refrigerant pipe 32 Inlet 33, 33' Zone 34, 34' Injection point 36 Evaporator outlet 37 Connection section 38 First capillary 39 Second capillary 40 Injection point

Claims

1. Household refrigeration appliance (10) having a first storage area (15) with a first target temperature and a second storage area (16) with a second target temperature, which is lower than the first target temperature, a refrigerant circuit which comprises a first evaporator (20, 20', 20") for cooling the first storage area and a second evaporator (30) for cooling the second storage area, wherein the second evaporator (30) is arranged in series downstream of the first evaporator (20, 20', 20") in the refrigerant circuit, wherein the first evaporator (20, 20', 20") has a surface on the refrigerant side for heat exchange with refrigerant circulating in the refrigerant circuit and a surface on the air side for heat exchange with the first storage area (15), and wherein in the case of the first evaporator (20, 20', 20") the ratio between the surface on the refrigerant side and the surface on the air side lies in a range of 0.12 to 0.25, wherein the first evaporator (20, 20', 20") is a plate evaporator on a rear wall (19) of the first storage area (15) and has a refrigerant pipe (31) with a pipe cross-section, wherein the first storage area (15) has an upper sub storage area (28), in which the household refrigeration appliance (10) is not equipped with bearing shells, and the pipe cross-section of the refrigerant pipe is smaller than 18 mm2, characterised in that the surface, on the air side, of the first evaporator (20, 20', 20") is smaller than 75% of the area available on the rear wall (19) of the upper sub storage area (28), and the first evaporator (20, 20', 20") has a continuous downwards pipe gradient in the direction of flow of the refrigerant.

2. Household refrigeration appliance according to claim 1, characterised in that a width (24) of the first evaporator (20, 20', 20") is smaller than 80% of a width (25) of the first storage area (15).

3. Household refrigeration appliance according to claim 1 or 2, characterised in that the refrigerant pipe (31) of the first evaporator (20, 20', 20") has an external diameter of less than or equal to 5 mm.

4. Household refrigeration appliance according to claim 1, 2, or 3, characterised in that a top side of the first evaporator (20, 20', 20") borders a ceiling of the first storage area (15).

5. Household refrigeration appliance according to one of the preceding claims, characterised in that an injection point (34') of the first evaporator is arranged laterally with respect to the first evaporator (20, 20', 20").

6. Household refrigeration appliance according to one of the preceding claims, characterised in that the first evaporator (20, 20', 20") has an injection point (34, 34') close to an upper edge.

7. Household refrigeration appliance according to one of the preceding claims, characterised in that a pipe guidance of the first evaporator (20, 20', 20") in a zone (33) shortly after the injection point (34, 34') is implemented more tightly than in the pipe sections arranged therebelow.

8. Household refrigeration appliance according to claim 7, characterised in that the guidance of the refrigerant pipe (31) of the first evaporator (20, 20', 20") below the zone (33) is implemented with a continuously decreasing width of pipe meanders.

9. Household refrigeration appliance according to one of the preceding claims, characterised in that the pipe gradient is greater than 2°.

10. Household refrigeration appliance according to one of the preceding claims, characterised in that a bearing shell is arranged below the first storage area and a lower edge of the first evaporator (20, 20', 20") is arranged at least 50 mm above an upper edge of the bearing shell.

11. Household refrigeration appliance according to claim 10, characterised in that the lower edge of the first evaporator (20, 20', 20") is arranged at most 200 mm above an upper edge of the bearing shell.

12. Household refrigeration appliance according to one of the preceding claims, characterised in that the first storage area (15) or the second storage area (16) has a variable-speed fan.

13. Household refrigeration appliance according to one of the preceding claims, characterised in that the second evaporator (30) is arranged in series downstream of the first evaporator (20, 20', 20") in the refrigerant circuit without a junction of a refrigerant pipe arranged therebetween.

14. Household refrigeration appliance according to one of claims 1 to 12, characterised in that the second evaporator (30) is arranged in series downstream of the first evaporator (20, 20', 20") in the refrigerant circuit with a junction (32) of a refrigerant pipe (31) arranged therebetween.

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