REFRIGERATOR

Abstract

A refrigerator (2) comprising a refrigeration system (4) a compartment (6) cooled by the refrigeration system (4) is provided. The refrigeration system (4) comprises a compressor (10), a condenser (12), a first expansion arrangement (14), an accumulator (16) for gaseous and liquid refrigerant, a second expansion arrangement (18), and an evaporator (20). The refrigeration system (4) comprises a first conduit path (22) and a second conduit path (24), the first and second conduit paths (22, 24) extending in parallel from the accumulator (16) towards the compressor (10). The compressor (10) is the only compressor of the refrigeration system (4) and the compressor (10) is a single stage compressor. A flow control device (26) is arranged in the conduit system (8) for alternately directing refrigerant through the first conduit path (22) and the second conduit path (24).

Description

TECHNICAL FIELD

The present invention relates to a refrigerator having a refrigeration circuit comprising an accumulator.

BACKGROUND

A refrigerator comprises a refrigeration system arranged to cool at least one compartment of the refrigerator. The temperature inside the compartment may be either above 0 degrees Celsius or below 0 degrees Celsius. The refrigerator comprises a refrigeration system wherein a refrigerant circulates. The refrigeration system comprises a compressor, a condenser, an expansion arrangement, and an evaporator. Gaseous refrigerant is compressed in the compressor and condenses to liquid phase in the condenser. Passing through the expansion arrangement, the pressure of the liquid refrigerant is reduced. The liquid refrigerant at low pressure evaporates in the evaporator. The evaporator is arranged in thermal communication with the compartment of the refrigerator. Thus, the evaporator cools the compartment. In such refrigeration systems energy losses occur in the expansion arrangement due to fluid flow friction. The fluid flow friction is caused by gaseous refrigerant flowing together with liquid refrigerant through the expansion arrangement and being subjected to a pressure reduction.

Two-stage compression systems comprising an accumulator arranged as a separator between a mid pressure level and a low pressure level are previously known outside the technical field of refrigerators. The accumulator may also be referred to as a flash tank. Two compressors operating at different pressure ratios, or one two-stage compressor with two inlet ports, provide basis for the expansion of the refrigerant to be divided into two steps, the two steps being separated by the accumulator at the mid pressure level. After a first expansion of the refrigerant from a high pressure level downstream of the condenser to the mid pressure level, the refrigerant in a gas/liquid mixture is led into the accumulator where the gaseous refrigerant is separated out and led to a mid pressure inlet of the compressor/s. The liquid refrigerant in the accumulator is subjected to a second expansion, wherein the pressure is lowered to the low pressure level, at which low pressure level the refrigerant evaporates in the evaporator. The evaporated low pressure refrigerant is led to a low pressure inlet of the compressor.

Although energy losses may be reduced in the latter kind of refrigeration systems, production costs and system complexity are higher than desired in some applications, e.g. in domestic refrigerators. Furthermore, suitably sized two-stage compressors for e.g. domestic refrigerators are not readily commercially available.

SUMMARY

An object of the present invention is to provide a refrigerator comprising a refrigeration system having the above mentioned advantage of reduced energy loss but which does at least alleviate the above mentioned drawbacks.

According to an aspect of the invention, the object is achieved by a refrigerator comprising a refrigeration system being at least intermittently flowed through by a refrigerant and a compartment cooled by the refrigeration system. The refrigeration system comprises a conduit system and system components interconnected by the conduit system. The system components comprise a compressor, a condenser, a first expansion arrangement, an accumulator for gaseous and liquid refrigerant, a second expansion arrangement, and an evaporator. The refrigeration system comprises a first conduit path and a second conduit path. The first and second conduit paths extend in parallel from the accumulator towards the compressor. The second conduit path extends, seen in the flow direction of the refrigerant, from the accumulator via the second expansion arrangement to the evaporator. The compressor is the only compressor of the refrigeration system and the compressor is a single stage compressor. A flow control device is arranged in the conduit system for alternately directing refrigerant through the first conduit path and the second conduit path.

Since the flow control device alternatingly directs refrigerant through the first and second conduit paths, one single stage compressor may be used in the system. Thus, a refrigerator of comparatively low complexity is achieved. As a result, the above mentioned object is achieved.

In the refrigerator, the first and second conduit paths are kept separated by means of the flow control device such that refrigerant flows either through the first conduit path or through the second conduit path. Accordingly, refrigerant flows alternately through the first conduit path at a mid pressure level and through the second conduit paths, partly at a low pressure level, to the compressor. The compressor has one compression stage only and accordingly, one external inlet and one external outlet.

The refrigerator may be a domestic refrigerator for foodstuffs. The refrigeration system is intermittently flowed through by the refrigerant due to the compressor being switched on and off based on the cooling requirements of e.g. the compartment. Accordingly, the refrigerant circulates in the refrigeration system while the compressor is running. As mentioned above, the refrigerant flows through one of the first and second conduit paths at a time. As the refrigerant circulates, the gaseous refrigerant coming from the compressor is cooled and condenses to a liquid state in the condenser. After the condenser, the liquid refrigerant is subjected to a pressure drop to the mid pressure level in the first expansion arrangement. The refrigerant in a gas/liquid mixture is led into the accumulator, inside which the mid pressure level prevails. The gaseous refrigerant is separated out in the accumulator and is led via the flow control device to the compressor. The liquid refrigerant in the accumulator is subjected to a second pressure drop in the second expansion arrangement, wherein the pressure is lowered to the low pressure level. At the low pressure level the refrigerant evaporates in the evaporator and cools the compartment, the evaporator being in thermal communication with the compartment. The evaporated low pressure gaseous refrigerant is led via the flow control device to the compressor. Accordingly, as the flow control device alternately directs refrigerant through the first conduit path and the second conduit path, gaseous refrigerant is compressed in the compressor alternately from the mid pressure level and the low pressure level.

The refrigerator may comprise a control system, which may be adapted to control the refrigerator, e.g. implementing the method according to aspects and embodiments discussed herein. The control system may be adapted to control e.g. the flow control device and the compressor. The control system may comprise temperature sensors arranged in thermal communication with the compartment, the evaporator, and/or the accumulator. The control system may comprise a pressure sensor arranged e.g. in the accumulator. The control system may be set to maintain the temperature in the compartment above 0 degrees Celsius or below 0 degrees Celsius. The first and second conduit paths may extend in parallel from the accumulator to the flow control device.

Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following detailed description. Those skilled in the art will realize that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention, as defined by the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The various aspects of the invention, including its particular features and advantages, will be readily understood from the following detailed description and the accompanying drawings, in which:

FIGS. 1 and 2 illustrate schematically refrigerators according to embodiments,

FIG. 3 illustrates a refrigerant property diagram representing p—pressure, and h—enthalpy of the refrigeration systems illustrated in FIGS. 1 and 2.

DETAILED DESCRIPTION

The present invention will now be described more fully with reference to the accompanying drawings, in which example embodiments are shown. However, this invention should not be construed as limited to the embodiments set forth herein. Disclosed features of example embodiments may be combined as readily understood by one of ordinary skill in the art to which this invention belongs. Like numbers refer to like elements throughout. Well-known functions or constructions will not necessarily be described in detail for brevity and/or clarity.

FIG. 1 illustrates schematically a refrigerator 2 according to embodiments. The refrigerator 2 comprises a refrigeration system 4 being at least intermittently flowed through by a refrigerant and a compartment 6 cooled by the refrigeration system 4. The refrigeration system 4 comprises a conduit system 8 and system components interconnected by the conduit system 8. The system components comprise a compressor 10, a condenser 12, a first expansion arrangement 14, an accumulator 16 for gaseous and liquid refrigerant, a second expansion arrangement 18, and an evaporator 20. The conduit system 4 extends, in the flow direction of the refrigerant, from the compressor 10 to the condenser 12, from the condenser 12 to the first expansion arrangement 14, and from the first expansion 14 arrangement to the accumulator 16. The refrigeration system 4 comprises a first conduit path 22 and a second conduit path 24. The first and second conduit paths 22, 24 extend in parallel from the accumulator 16 to a flow control device 26. The compressor 10 is the only compressor of the refrigeration system 4 and the compressor 10 is a single stage compressor. The flow control device 26 is arranged in the conduit system 8 and alternately directs refrigerant through the first conduit path 22 and the second conduit path 24. The flow control device 26 is arranged upstream of the compressor 10 and downstream of the accumulator 16. The first conduit path 22 and the second conduit path 24 meet upstream of the compressor 10 and downstream of the accumulator 16 and the evaporator 20. The first conduit path 22 extends from the accumulator 16 to the flow control device 26. The second conduit path 24 extends, seen in the flow direction of the refrigerant, from the accumulator 16 via the second expansion arrangement 18 to the evaporator 20 and to the flow control device 26. The flow control device 26 comprises a 3-way valve 28 interconnecting the first conduit path 22, the second conduit path 24, and the compressor 10.

In the conduit system 8 there is arranged a first heat exchanger 30. The first heat exchanger 30 is arranged to transfer heat from liquid refrigerant before the first expansion arrangement 14 to gaseous refrigerant in the first conduit path 22 after the accumulator 16. Accordingly, the refrigeration system 4 comprises a first heat exchanger 30. The first heat exchanger 30 comprising a first passage 32 and a second passage 34. The first passage 32 comprises portions of the first conduit path 22 downstream of the accumulator 16. The second passage 34 is arranged downstream of the condenser 12 and upstream of the first expansion arrangement 14, or the second passage 34 forms part of the first expansion arrangement 14. When refrigerant flows through the first conduit path 22, in the first heat exchanger 30, liquid refrigerant flowing from the condenser 12 to the first expansion arrangement 14, or through the first expansion arrangement 14, is cooled while gaseous refrigerant at the mid pressure level in the first refrigerant path 22 is superheated. Similarly, in the conduit system 8 there is arranged a second heat exchanger 36. The second heat exchanger 36 is arranged to transfer heat from liquid refrigerant in the second conduit path 24 before the second expansion arrangement 18 to gaseous refrigerant in the second conduit path 22 after the evaporator 20. Accordingly, the refrigeration system 4 comprises a second heat exchanger 36. The second heat exchanger 36 comprises a third passage 38 and a fourth passage 40. The third passage 38 comprises portions of the second conduit path 24 downstream of the accumulator 16 and upstream of the second expansion arrangement 18, or the third passage 38 forms part of the second expansion arrangement 18. The fourth passage 40 comprises portions of the second conduit path 24 downstream of the evaporator 20. When refrigerant flows through the second conduit path 24, in the second heat exchanger 36, liquid refrigerant flowing from the accumulator 16 to the second expansion arrangement 18 is cooled while gaseous refrigerant at the low pressure level in the second refrigerant path 24 after the evaporator is superheated. In embodiments where the second passage 34 of the first heat exchanger 30 forms part of the first expansion arrangement 14 as well as in embodiments where the third passage 38 forms part of the second expansion arrangement 18, a capillary tube of an expansion arrangement forms the second passage 34 and the third passage 38, respectively. Alternatively, one or both of the first and second heat exchangers 30, 36 may be omitted from the conduit system 8.

FIG. 2 illustrates schematically a refrigerator 2 according to embodiments. The main differences to the FIG. 1 embodiments are discussed below. In these embodiments the flow control device 28 comprises a first valve 42 arranged in the first conduit path 22 and a second valve 44 arranged in the second conduit path 24. More specifically, the second valve is a check valve 44. The check valve 44 prevents refrigerant from flowing into the second conduit path 24 when the refrigerant flows at mid pressure level through the first conduit path 26. The heat first heat exchanger 30 has been omitted and the second heat exchanger 36 comprising the third passage 38 and the fourth passage 40 is arranged downstream of the condenser 12. The third passage 38 is arranged downstream of the condenser 12 and upstream of the first expansion arrangement 14, or the third passage 38 forms part of the first expansion arrangement 14. The fourth passage 40 comprises portions of the second conduit path 24 downstream of the evaporator 20.

A further possible arrangement of the second heat exchanger 38 may include the second heat exchanger 38 as illustrated in connection with FIG. 1. That is, the second heat exchanger 38 may include two parts, one part arranged between the condenser 12 and the accumulator 16 (as in FIG. 2) and a further part arranged between the accumulator 16 and the evaporator 20 (as in FIG. 1). In such an embodiment refrigerant from the evaporator 12 may flow first through the fourth passage 40 of the heat exchanger part arranged between the accumulator 16 and the evaporator 20, and then through the fourth passage 40 of the heat exchanger part arranged between the condenser 12 and the accumulator 16. Also the first heat exchanger 30 of the FIG. 1 embodiments may be provided in the conduit system 8. In such case, a further possible heat exchanger arrangement may be to integrate the first and second heat exchangers 30, 36 with each other, the second passage 34 and the third passage 38 being arranged downstream of the condenser 12 and upstream of the first expansion arrangement 14, and/or the second and third passages 34, 38 forming part of the first expansion arrangement 14.

FIG. 3 illustrates a refrigerant property diagram representing p—pressure, and h—enthalpy of the refrigeration systems 4 illustrated in FIGS. 1 and 2. The diagram is a schematic representation of pressure and enthalpy changes of a refrigerant circulating in the refrigeration system 4. The diagram is provided to illustrate the gain made by the use of an accumulator 16 as described herein. The curve 50 represents the complete transition of the refrigerant between liquid and gaseous phase, and vice versa. At the left hand end of the curve 50 the refrigerant is in liquid phase and at the right hand end of the curve 50 the refrigerant is in gaseous phase. Within the curve 50 the refrigerant is in both liquid and gaseous phase to various degrees. A horizontal line in the diagram represents an isobar. Moreover, a horizontal line within the curve 50 represents an isotherm. Moving from left to right along an isotherm in the diagram, the refrigerant is evaporating. Conversely, moving from right to left along an isotherm, the refrigerant is condensing.

The lines provided with arrows represent the pressure and specific enthalpy of the refrigerant as it circulates in the refrigeration system 4. The larger box, formed by the lines provided with arrows, represents circulation of refrigerant via the second conduit path 24 comprising the evaporator 20. The smaller box, formed by the lines provided with arrows, represents circulation of refrigerant via the first conduit path 22.

The heat, or energy, Q, transferred by the refrigerant is the difference in specific enthalpy, Δh, times the mass flow, m′, of the refrigerant, i.e. Δh×m′. Δh is represented by a distance along the h-axis in the diagram.

Part of the line 52 represents the condensation of the refrigerant in the condenser 12. At point 54 the refrigerant is subject to a pressure drop in the first expansion arrangement 14. While refrigerant flows through the first conduit path 22, gaseous refrigerant from the accumulator 16 is compressed in the compressor 10. Line 56 represents the mid pressure level in the accumulator 16. Line 58 represents this compression in the compressor 10. As the refrigerant circulates through the refrigeration system via the first conduit path 22, gaseous refrigerants from the accumulator 16 is compressed and condenses to liquid refrigerant in the condenser 12, which in turn flows to the accumulator 16.

When the refrigerant instead circulates in the refrigeration system 4 via the second conduit path 24, the refrigerant is subjected to a first pressure drop at point 54 in the first expansion arrangement 14 to the mid pressure level in the accumulator 16. Liquid refrigerant from the accumulator 16 at the mid pressure level is subjected to a second pressure drop at point 62 in the second expansion arrangement 18 to the low pressure level. Line 64 represents evaporation of the refrigerant in the evaporator 20 at the low pressure level. Line 66 represents compression in the compressor 10 of the refrigerant coming from the low pressure level.

As can be seen from the length of line 64 in the diagram; owing to the use of the accumulator 16, and the alternate flow of refrigerant through the first and second conduit paths 22, 24, the enthalpy available for cooling in the evaporator 20 is more, than if no accumulator 16 would be present and only flow of refrigerant through the second conduit path 24 would take place, i.e. the line 64 would in such case only start vertically below point 54.

A control system of the refrigerator 2 may be arranged to control at least the compressor 10 and the flow control device 26. A temperature of the compartment 6 may be used as a condition for the running 100 of the compressor 10. For instance, at a maximum temperature threshold inside the compartment 6, the compressor 10 is started and at a minimum temperature threshold inside the compartment 6, the compressor 10 is stopped. Alternatively, an average temperature inside the compartment 6 may be decisive for running the compressor 10. The control system may direct the refrigerant alternately through the first conduit path 22 and the second conduit path 24 based on pressure criteria, e.g. in the accumulator 16. Accumulator pressure may e.g. be established directly by a pressure sensor inside the accumulator 16, or indirectly by temperature measurements on the accumulator 16.

Example embodiments described above may be combined as understood by a person skilled in the art. It is also understood by those skilled in the art that each one of the first and second expansion arrangements may be e.g. a capillary tube, a thermostatic expansion valve or an electronic expansion valve. The compressor 10 may be of single speed compressor or a variable speed compressor. Although the invention has been described with reference to example embodiments, many different alterations, modifications and the like will become apparent for those skilled in the art. Therefore, it is to be understood that the foregoing is illustrative of various example embodiments and that the invention is defined only the appended claims.

As used herein, the term “comprising” or “comprises” is open-ended, and includes one or more stated features, elements, steps, components or functions but does not preclude the presence or addition of one or more other features, elements, steps, components, functions or groups thereof.

Claims

1. A refrigerator (2) comprising a refrigeration system (4) being at least intermittently flowed through by a refrigerant and a compartment (6) cooled by the refrigeration system (4), wherein the refrigeration system (4) comprises a conduit system (8) and system components interconnected by the conduit system (8), wherein the system components comprise a compressor (10), a condenser (12), a first expansion arrangement (14), an accumulator (16) for gaseous and liquid refrigerant, a second expansion arrangement (18), and an evaporator (20), and wherein the refrigeration system (4) comprises a first conduit path (22) and a second conduit path (24), the first and second conduit paths (22, 24) extending in parallel from the accumulator (16) towards the compressor (10), wherein the second conduit path (24) extends, seen in the flow direction of the refrigerant, from the accumulator (16) via the second expansion arrangement (18) to the evaporator (20), characterized in that the compressor (10) is the only compressor of the refrigeration system (4) and the compressor (10) is a single stage compressor, and wherein a flow control device (26) is arranged in the conduit system (8) for alternately directing refrigerant through the first conduit path (22) and the second conduit path (24).

2. The refrigerator (2) according to claim 1, wherein the conduit system (8) extends, in the flow direction of the refrigerant, from the compressor (10) to the condenser (12), from the condenser (12) to the first expansion arrangement (14), and from the first expansion arrangement (14) to the accumulator (16).

3. The refrigerator (2) according to claim 1, wherein the flow control device (26) is arranged upstream of the compressor (10) and downstream of the accumulator (16), and wherein the first conduit path (22) and the second conduit path (24) meet upstream of the compressor (10) and downstream of the accumulator (16) and the evaporator (20).

4. The refrigerator (2) according to claim 1, wherein the flow control device (26) comprises a 3-way valve (28) interconnecting the first conduit path (22), the second conduit path (24), and the compressor (10).

5. The refrigerator (2) according to claim 1, wherein the flow control device (26) comprises a first valve (42) arranged in the first conduit path (22) and a second valve (44) arranged in the second conduit path (24).

6. The refrigerator (2) according to claim 5, wherein the second valve is a check valve (44).

7. The refrigerator (2) according to claim 1, wherein the refrigeration system (4) comprises a first heat exchanger (30), the first heat exchanger (30) comprising a first passage (32) and a second passage (34), the first passage (32) comprising portions of the first conduit path (22) downstream of the accumulator (16) and the second passage (34) being arranged downstream of the condenser (12) and upstream of the first expansion arrangement (14), or the second passage (34) forms part of the first expansion arrangement (14).

8. The refrigerator (2) according to claim 1, wherein the refrigeration system (4) comprises a second heat exchanger (36), the second heat exchanger (36) comprising a third passage (38) and a fourth passage (40), the third passage (38) comprising portions of the second conduit path (24) downstream of the accumulator (16) and upstream of the second expansion arrangement (18), or the third conduit path forming part of the second expansion arrangement 18, and wherein the fourth passage (40) comprises portions of the second conduit path (24) downstream of the evaporator (20).

9. The refrigerator (2) according to claim 1, wherein the refrigeration system (4) comprises a second heat exchanger (36), the second heat exchanger (36) comprising a third passage (38) and a fourth passage (40), the third passage (38) being arranged downstream of the condenser (12) and upstream of the first expansion arrangement (14), or the third passage (38) forming part of the first expansion arrangement (14), and wherein the fourth passage (40) comprises portions of the second conduit path (24) downstream of the evaporator (20).