CN113432326A

CN113432326A - Cascade compression refrigeration system and refrigeration equipment with same

Info

Publication number: CN113432326A
Application number: CN202010208889.8A
Authority: CN
Inventors: 赵向辉; 刘煜森; 孙永升; 陶瑞涛; 冯茹丹
Original assignee: Qingdao Haier Smart Technology R&D Co Ltd; Haier Smart Home Co Ltd
Current assignee: Qingdao Haier Smart Technology R&D Co Ltd; Haier Smart Home Co Ltd
Priority date: 2020-03-23
Filing date: 2020-03-23
Publication date: 2021-09-24

Abstract

The invention provides a cascade compression refrigeration system and a refrigeration device with the same, wherein the cascade compression refrigeration system comprises: a high-temperature-stage refrigeration cycle including a first refrigerant that flows through the interior thereof; the low-temperature-stage refrigeration cycle includes a second refrigerant that flows through the interior thereof. The absolute pressure range of the high-pressure side of the low-temperature refrigeration circulation loop in a stable operation state is configured to be 2-11 bar, and the absolute pressure range of the low-pressure side of the low-temperature refrigeration circulation loop in the stable operation state is configured to be 0.2-1.1 bar. The low-temperature stage compressor has lower suction pressure and lower discharge pressure, can be formed by replacing lubricating oil on the basis of the conventional R600a compressor, can effectively reduce noise generated during operation, has higher energy efficiency, and can be suitable for household small refrigeration equipment.

Description

Cascade compression refrigeration system and refrigeration equipment with same

Technical Field

The invention relates to the field of refrigeration, in particular to a cascade compression refrigeration system and refrigeration equipment with the same.

Background

A cascade compression refrigeration system generally includes two separate refrigeration cycles, which are called a high-temperature stage refrigeration cycle (referred to as a high-temperature portion) and a low-temperature stage refrigeration cycle (referred to as a low-temperature portion), respectively. The high temperature portion uses a first refrigerant having a relatively high normal boiling point, and the low temperature portion uses a second refrigerant having a relatively low normal boiling point. And the condensation evaporator is used for condensing the second refrigerant vapor discharged by the compressor of the low-temperature part by utilizing the cold energy prepared by the first refrigerant of the high-temperature part, and is an evaporator of the high-temperature part and a condenser of the low-temperature part.

In the prior art, due to the fact that the noise of the cascade compression refrigeration system is too large, normal work and rest of a user are affected, and the cascade compression refrigeration system cannot be applied to household small refrigeration equipment.

Therefore, how to reduce the operation noise of the cascade compression refrigeration system becomes a technical problem to be solved by those skilled in the art.

Disclosure of Invention

An object of the present invention is to provide a cascade compression refrigeration system and a refrigeration apparatus having the same that at least partially solve the above problems.

It is a further object of the present invention to reduce operational noise of a cascade compression refrigeration system.

A further object of the present invention is to improve the freshness retaining ability of a small household refrigeration appliance having a cascade compression refrigeration system.

It is a further object of the present invention to reduce the compression ratio of the low temperature stage compressor in the low temperature stage refrigeration cycle.

The invention provides a cascade compression refrigeration system and refrigeration equipment with the same, comprising: a high-temperature-stage refrigeration cycle including a first refrigerant that flows through the interior thereof; a low-temperature-stage refrigeration cycle including a second refrigerant that flows through the interior thereof; the low-temperature-stage refrigeration circulation loop is also internally provided with a condensing part for promoting the heat exchange between a second refrigerant flowing through the condensing part and a first refrigerant flowing through an evaporation part in the high-temperature-stage refrigeration circulation loop; the absolute pressure range of the high-pressure side of the low-temperature refrigeration circulation loop in a stable operation state is configured to be 2-11 bar, and the absolute pressure range of the low-pressure side of the low-temperature refrigeration circulation loop in the stable operation state is configured to be 0.2-1.1 bar.

Optionally, the absolute pressure range of the high-pressure side of the low-temperature stage refrigeration cycle loop in a stable operation state is configured to be 2-9 bar; the value range of the lower limit value of the absolute pressure of the low-pressure side of the low-temperature stage refrigeration cycle loop in a stable operation state is configured to be 0.2-0.8 bar, or 0.2-0.6 bar, or 0.2-0.5 bar, or 0.2-0.4 bar.

Alternatively, the evaporation temperature range of the second refrigerant on the low-pressure side in the low-temperature stage refrigeration cycle in the steady operation state is configured to be-111 to-35 ℃.

Optionally, the evaporation temperature range of the second refrigerant on the low-pressure side in the low-temperature stage refrigeration cycle in the steady operation state is configured to be-80 to-35 ℃ or-75 to-40 ℃.

Optionally, the second refrigerant is a pure working medium refrigerant or an azeotropic refrigerant, and the standard boiling point range of the second refrigerant is set to-60 to-30 ℃, or-55 to-35 ℃, or-50 to-35 ℃.

Alternatively, the evaporation temperature range of the second refrigerant on the low-pressure side in the low-temperature stage refrigeration cycle in the steady operation state is configured to be-111 to-50 ℃.

Optionally, the second refrigerant is a non-azeotropic refrigerant, wherein the second refrigerant comprises the first component; the standard boiling point range of the first component is-60-0 ℃, or-50-0 ℃, or-45-0 ℃, or-15-0 ℃; the mass fraction of the first component in the second refrigerant is set to 20% to 80%.

Optionally, the ODP value of the second refrigerant is set to 0, and GWP of the second refrigerant₁₀₀The value is configured to be 200 or less.

Optionally, the evaporation temperature range of the first refrigerant at the low-pressure side of the high-temperature stage refrigeration cycle loop in a stable operation state is configured to be-40 ℃ to 0 ℃, or-35 ℃ to-10 ℃, or-30 ℃ to-15 ℃.

Optionally, under the condition that the suction temperature range is 10-38 ℃ and the suction superheat degree range of a low-temperature stage compressor in the low-temperature stage refrigeration cycle loop is 80-95K, the exhaust temperature of the low-temperature stage compressor is configured to be less than or equal to 110 ℃; or the exhaust temperature of the low-temperature stage compressor is set to be less than or equal to 100 ℃ under the conditions that the suction temperature range is 15-35 ℃ and the suction superheat degree range of the low-temperature stage compressor is 80-85K.

Optionally, the cylinder volume of the low-temperature stage compressor in the low-temperature stage refrigeration cycle loop is configured to be 4-20 ml, or 5-15 ml, or 8.5-13.5 ml.

Optionally, the low temperature stage refrigeration cycle comprises: a low temperature stage compressor; the low-temperature stage throttling device and the low-temperature stage evaporator are arranged between the condensing part and the suction inlet of the low-temperature stage compressor, and the low-temperature stage throttling device is arranged at the upstream of the low-temperature stage evaporator; a heat exchange device, comprising: a heat release part arranged between the condensing part and the low-temperature stage throttling device; and a heat absorption part disposed between the low-temperature-stage evaporator and the suction port of the low-temperature-stage compressor, the heat absorption part being configured to cause the second refrigerant flowing therethrough to absorb heat of the second refrigerant flowing through the heat release part.

According to another aspect of the present invention, there is also provided a refrigerating apparatus including: a box body; the cascade compression refrigeration system of any one of the above mentioned is arranged in the box body.

The invention discloses a cascade compression refrigeration system and refrigeration equipment with the same, wherein the cascade compression refrigeration system comprises a high-temperature-level refrigeration circulation loop, a first refrigerant, a low-temperature-level refrigeration circulation loop and a second refrigerant. The absolute pressure range of the high pressure side of the low-temperature stage refrigeration circulation loop in a stable operation state is configured to be 2-11 bar, and the absolute pressure range of the low pressure side of the low-temperature stage refrigeration circulation loop in the stable operation state is configured to be 0.2-1.1 bar, so that a low-temperature stage compressor in the low-temperature stage refrigeration circulation loop can have lower suction pressure and lower exhaust pressure when the low-temperature stage refrigeration circulation loop operates, noise generated during operation can be effectively reduced, and the low-temperature stage refrigeration circulation loop can be suitable for household small refrigeration equipment.

Further, the cascade compression refrigeration system and the refrigeration equipment with the cascade compression refrigeration system are characterized in that the evaporation temperature of the second refrigerant circulating in the low-temperature stage refrigeration circulation loop at the low-pressure side in the low-temperature stage refrigeration circulation loop can reach below-60 ℃ or even below-80 ℃, so that the cascade compression refrigeration system can be used for creating low temperature of about-60 ℃ or even-80 ℃ for the storage chamber in the household small refrigeration equipment, and the fresh-keeping capacity of the household small refrigeration equipment is improved.

Further, the cascade compression refrigeration system and the refrigeration equipment with the cascade compression refrigeration system are provided with a heat exchange device in the low-temperature stage refrigeration circulation loop, wherein the heat exchange device comprises a heat release part arranged between the condensation part and the low-temperature stage throttling device and a heat absorption part arranged between the low-temperature stage evaporator and the suction inlet of the low-temperature stage compressor, and the heat absorption part is configured to promote the second refrigerant flowing through the heat exchange device to absorb the heat of the second refrigerant flowing through the heat release part, so that the second refrigerant is condensed in multiple sections and evaporated in multiple sections, the second refrigerant flowing through the condensation part can be continuously condensed in the heat release part, the second refrigerant flowing out of the heat release part can be fully condensed, the second refrigerant flowing out of the low-temperature stage evaporator can be continuously evaporated in the heat absorption part, the compression ratio of the low-temperature stage compressor is reduced to a certain extent, and the loss of cold energy caused by over-low suction temperature can be reduced or avoided, the refrigeration efficiency is improved, and condensation or frost formation near the suction inlet of the low-temperature stage compressor is avoided.

The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments thereof, taken in conjunction with the accompanying drawings.

Drawings

Some specific embodiments of the invention will be described in detail hereinafter, by way of illustration and not limitation, with reference to the accompanying drawings. The same reference numbers in the drawings identify the same or similar elements or components. Those skilled in the art will appreciate that the drawings are not necessarily drawn to scale. In the drawings:

FIG. 1 is a schematic diagram of a refrigeration appliance having a cascade compression refrigeration system according to one embodiment of the present invention;

FIG. 2 is a schematic diagram of a cascade compression refrigeration system according to one embodiment of the present invention;

FIG. 3 is a schematic view of a cascade compression refrigeration system according to one embodiment of the present invention;

FIG. 4 is a schematic view of a cascade compression refrigeration system according to one embodiment of the present invention;

figure 5 is a pressure-enthalpy diagram corresponding to the operation of the low temperature stage refrigeration cycle in the cascade compression refrigeration system of figure 4;

FIG. 6 is a schematic view of a cascade compression refrigeration system according to another embodiment of the present invention;

figure 7 is a schematic diagram of a cascade compression refrigeration system according to another embodiment of the present invention.

Detailed Description

Figure 1 is a schematic diagram of a refrigeration appliance 10 having a cascade compression refrigeration system according to one embodiment of the present invention.

The refrigeration device 10 may be a small household refrigeration device for storing food, medicine, or other items, and may be, for example, a refrigerator, or freezer.

Although the cascade compression refrigeration system is already involved in large-scale refrigeration equipment, the operation noise and the energy consumption of the existing cascade compression refrigeration system are too high, so that the cascade compression refrigeration system in the prior art cannot be applied to small-scale household refrigeration equipment.

The cascade compression refrigeration system of the present embodiment is particularly suitable for use in a small household refrigeration appliance 10.

The refrigeration apparatus 10 in the present embodiment is exemplified by a refrigerator. The refrigeration appliance 10 having the cascade compression refrigeration system may be a refrigerator.

The refrigeration appliance 10 may generally include: a cabinet 110 and a cascade compression refrigeration system provided in the cabinet 110. Wherein, a storage compartment 111 for storing articles is further formed in the case body 110. In this embodiment, the storage compartment 111 may be a plurality of compartments, and may include, for example, a refrigeration compartment, a freezing compartment (which is a normal freezing compartment), a variable temperature compartment, and/or a cryogenic compartment. In other alternative embodiments, the storage compartment 111 may be one, for example, a cryogenic compartment or a temperature-changing compartment. A plurality of evaporator installation cavities for installing evaporators can be formed in the box body 110, and the evaporator installation cavities can be correspondingly arranged on the back, the top, the side or the bottom of the storage compartment 111.

Figure 2 is a schematic diagram of a cascade compression refrigeration system according to one embodiment of the present invention.

The cascade compression refrigeration system may be a two-stage cascade circulation system, a three-stage cascade circulation system, or a four-stage cascade circulation system, where the cascade stage is not specifically limited. The present embodiment is merely exemplary of a cascade compression refrigeration system having a two-stage cascade cycle system, and those skilled in the art should be fully capable of extension in this regard.

The cascade compression refrigeration system may include: the high-temperature-stage refrigeration cycle circuit and the low-temperature-stage refrigeration cycle circuit may further include: a radiator fan 280 and a blower fan 290. The high-temperature refrigeration circulation loop forms a high-temperature refrigeration circulation system, and the low-temperature refrigeration circulation loop forms a low-temperature refrigeration circulation system.

A high-temperature-stage refrigeration cycle includes a first refrigerant that flows through the interior thereof. The high-temperature stage refrigeration cycle circuit further includes: a high-temperature stage compressor 211, a high-temperature stage condenser 212, and an evaporation portion 231. An evaporation unit 231 provided between the high-temperature-stage condenser 212 and the suction port of the high-temperature-stage compressor 211; the evaporation portion 231 serves to cause the first refrigerant flowing therethrough to absorb heat of the second refrigerant flowing through the condensation portion 232 within the low-temperature stage refrigeration cycle circuit.

The low-temperature-stage refrigeration cycle includes a second refrigerant that flows through the interior thereof. The low-temperature stage refrigeration cycle circuit is also provided with a low-temperature stage compressor 251, a condensing part 232, a low-temperature stage throttling device 255, a low-temperature stage evaporator 256 and a heat exchange device.

A low-temperature-stage throttling device 255 and a low-temperature-stage evaporator 256 are provided between the condensing portion 232 and the low-temperature-stage compressor suction port, and the low-temperature-stage throttling device 255 is provided upstream of the low-temperature-stage evaporator 256. The low-temperature-stage evaporator 256 is used to promote the second refrigerant flowing through it to absorb heat in the storage compartment 111, so that the storage compartment 111 is cooled.

Condensing portion 232 may be disposed between a discharge port of low-temperature-stage compressor 251 and low-temperature-stage evaporator 256, for example, between a discharge port of compressor 251 and low-temperature-stage throttling device 255. The condensing portion 232 functions to cause the second refrigerant flowing therethrough to exchange heat with the first refrigerant flowing through the evaporating portion 231 within the high-temperature stage refrigeration cycle.

That is, the high-temperature stage refrigeration cycle may include: the high-temperature stage compressor 211, the high-temperature stage condenser 212, and the evaporation portion 231, and the low-temperature stage refrigeration cycle circuit may include: low-temperature stage compressor 251, condensing unit 232, low-temperature stage throttling device 255, low-temperature stage evaporator 256, and a heat exchange device.

In some alternative embodiments, the condensing portion 232 and the evaporating portion 231 may form a condensing evaporator. The condensing evaporator can be a double-pipe heat exchanger, the double-pipe heat exchanger is a concentric sleeve formed by mutually sleeving and connecting two standard pipes with different sizes, the channel outside is called a shell pass, and the channel inside is called a pipe pass. The two different media can flow in the shell side and the tube side in the opposite directions (or in the same direction) to achieve the effect of heat exchange. The evaporation portion 231 may be a tube side, and the condensation portion 232 may be a shell side.

A heat exchange device, comprising: a heat radiating section 271 and a heat absorbing section 272. The heat radiating unit 271 is disposed between the condensing unit 232 and the low-temperature-stage throttling device 255. The heat absorbing part 272 is arranged between the low-temperature stage evaporator 256 and the suction inlet of the low-temperature stage compressor 251, and the heat absorbing part 272 is configured to promote the second refrigerant flowing through the heat absorbing part to absorb the heat of the second refrigerant flowing through the heat radiating part 271, so that the second refrigerant is condensed in multiple sections and evaporated in multiple sections, and the second refrigerant flowing out of the condensing part 232 can be continuously condensed in the heat radiating part 271, so that the second refrigerant flowing out of the heat radiating part 271 can be fully condensed, and the second refrigerant flowing out of the low-temperature stage evaporator 256 can be continuously evaporated in the heat absorbing part 272, thereby reducing the compression ratio of the low-temperature stage compressor 251 to a certain extent, reducing or avoiding the cold loss caused by too low suction temperature, improving the refrigeration efficiency, and avoiding condensation or frost formation near the suction inlet of the low-temperature stage compressor 251.

The refrigerant, also called refrigerant, usually completes energy conversion by phase change, and is a working substance that circulates in a refrigeration system of the refrigeration equipment 10, and its working principle is: the refrigerant absorbs heat of a substance to be cooled in the evaporator to evaporate, transfers the absorbed heat to ambient air or water in the condenser to be cooled into liquid, and circulates back and forth to achieve the refrigeration effect by means of state change. The refrigerants can be roughly classified into the following three categories, according to the magnitude of the condensation pressure at normal temperature and the magnitude of the evaporation temperature at atmospheric pressure: a high temperature refrigerant, a medium temperature refrigerant, and a low temperature refrigerant. The "high temperature" and the "low temperature" in the "high temperature stage refrigeration cycle circuit" and the "low temperature stage refrigeration cycle circuit" are relative, and the evaporation temperature of the first refrigerant flowing through the high temperature stage refrigeration cycle circuit is higher than the evaporation temperature of the second refrigerant flowing through the low temperature stage refrigeration cycle circuit.

The refrigerant can be classified into the following three groups according to its composition: pure working medium refrigerant, azeotropic refrigerant and non-azeotropic refrigerant. Pure working medium refrigerant, also called single refrigerant, refers to a refrigerant formed by a single component substance. The azeotropic refrigerant is a refrigerant prepared by mixing two or more mutually soluble single-component substances according to a certain mass ratio or volume ratio at normal temperature, the properties of the azeotropic refrigerant are the same as those of a single refrigerant, the azeotropic refrigerant has a constant evaporation temperature under a constant pressure, and the components of a gas phase and a liquid phase are the same. The non-azeotropic refrigerant is a mixed solution of two or more single refrigerants which do not form azeotropic solution, when the solution is heated, the evaporation proportion of the volatile component is large, the evaporation proportion of the non-volatile component is small, the gas-liquid two-phase composition is different, and the temperature of the refrigerant is changed in the evaporation process, and the refrigerant has similar characteristics in the condensation process.

The first refrigerant of the present embodiment may be a medium-temperature refrigerant, and the second refrigerant may be a low-temperature refrigerant.

The absolute pressure range of the high-pressure side of the low-temperature refrigeration circulation loop in a stable operation state is configured to be 2-11 bar, and the absolute pressure range of the low-pressure side of the low-temperature refrigeration circulation loop in the stable operation state is configured to be 0.2-1.1 bar.

Wherein, the high pressure side in the low-temperature stage refrigeration cycle is that: in the flow direction of the second refrigerant, a portion between the discharge port of the low-temperature-stage compressor 251 and the upstream of the suction port of the low-temperature-stage throttling device 255 in the low-temperature-stage refrigeration cycle circuit. The low-pressure side in the low-temperature stage refrigeration cycle is as follows: in the flow direction of the second refrigerant, a portion between the discharge port downstream of the low-temperature-stage throttling device 255 and the suction port of the low-temperature-stage compressor 251 in the low-temperature-stage refrigeration cycle circuit. In general, the high-side absolute pressure of the low-temperature stage refrigeration cycle may be detected at a preset position near the downstream of the discharge port of the low-temperature stage compressor 251, and the low-side absolute pressure of the low-temperature stage refrigeration cycle may be detected at a preset position near the upstream of the suction port of the low-temperature stage compressor 251. In some alternative embodiments, if the low temperature stage compressor 251 is provided with a process port for direct communication with a low pressure cavity inside the low temperature stage compressor 251, the low pressure side absolute pressure can be detected at the process port.

The low-temperature stage refrigeration cycle loop can enter a stable operation state after being started for a certain time. In the embodiment, whether the low-temperature-stage refrigeration circulation circuit is in a stable operation state is judged according to the low-pressure-side absolute pressure of the low-temperature-stage refrigeration circulation circuit. After the low-temperature refrigeration circulation loop is started, the absolute pressure of the low-pressure side of the low-temperature refrigeration circulation loop can be continuously acquired. If the ratio of the highest value of the absolute pressure of the low-pressure side of the low-temperature stage refrigeration circulation loop to the average value of the absolute pressure of the low-pressure side of the low-temperature stage refrigeration circulation loop is smaller than a first preset ratio and the ratio of the lowest value of the absolute pressure of the low-pressure side of the low-temperature stage refrigeration circulation loop to the average value of the absolute pressure of the low-pressure side of the low-temperature stage refrigeration circulation loop is larger than a second preset ratio within a first set time, it is indicated that the low-temperature stage refrigeration circulation loop within the first set time is in a stable operation state. The average value of the low-pressure-side absolute pressure of the low-temperature-stage refrigeration cycle circuit is an arithmetic average value of the highest value of the low-pressure-side absolute pressure of the low-temperature-stage refrigeration cycle circuit and the lowest value of the low-pressure-side absolute pressure of the low-temperature-stage refrigeration cycle circuit within a first set time. The first set time may be any time within a range of 0.25 to 1 hour, for example, 0.25 hour, 0.5 hour, or 1 hour, and preferably, 0.25 hour or 0.5 hour. The first predetermined ratio may be any value in the range of 1 to 1.2, for example, 1, 1.1, or 1.2, preferably 1.1, and the second predetermined ratio may be any value in the range of 0.85 to 0.95, for example, 0.85, 0.9, or 0.95, preferably 0.9. In this embodiment, the absolute pressure of the low-pressure side of the low-temperature refrigeration cycle loop can be acquired after a test pack (GB/T8059) is put into the storage compartment 111 of the refrigeration apparatus 10, so as to monitor the stable operation state of the low-temperature refrigeration cycle loop.

Because the exhaust pressure of the low-temperature stage compressor 251 is set corresponding to the high-pressure side absolute pressure of the low-temperature stage refrigeration cycle, the suction pressure of the low-temperature stage compressor 251 is set corresponding to the low-pressure side absolute pressure of the low-temperature stage refrigeration cycle, and when the low-temperature stage refrigeration cycle runs, the low-temperature stage compressor 251 has lower suction pressure and lower exhaust pressure, which can effectively reduce the noise generated during running, and can also reduce the energy consumption during running, and can be suitable for the household small refrigeration equipment 10.

The absolute pressure range of the high-pressure side of the low-temperature refrigeration cycle loop in a stable operation state can be configured to be 2-9 bar or 2-10 bar. The absolute pressure of the high-pressure side of the low-temperature stage refrigeration cycle in a stable operation state can be any value within 2-11 bar, for example, 2bar, 3bar, 4bar, 5bar, 6bar, 7bar, 8bar, 9bar, 10bar or 11 bar.

The lowest absolute pressure range of the low-pressure side of the low-temperature stage refrigeration cycle loop in a stable operation state can be configured to be 0.2-0.8 bar, or 0.2-0.6 bar, or 0.2-0.5 bar, or 0.2-0.4 bar.

In some optional embodiments, the lower limit of the absolute pressure at the low-pressure side of the low-temperature stage refrigeration cycle loop in the stable operation state may be configured to be 0.2 to 0.8bar, or 0.2 to 0.6bar, or 0.2 to 0.5bar, or 0.2 to 0.4 bar.

The low temperature stage refrigeration cycle loop may be pre-set with multiple refrigeration temperatures, for example, but not limited to, refrigeration temperatures of 5 ℃, -5 ℃, -18 ℃, -40 ℃, -60 ℃ or-80 ℃. The low-temperature refrigeration circulation loop can reach respective stable operation state when operating according to different refrigeration temperatures. The refrigeration temperatures are different, and the absolute pressures of the low-pressure sides of the low-temperature refrigeration circulation loops in the stable operation state can be different. The low-pressure side absolute pressure of the low-temperature stage refrigeration circulation loop in a stable operation state reaches a lower limit value in a set time period before the low-temperature stage refrigeration circulation loop is shut down. The refrigeration temperatures are different, the lower limit value of the absolute pressure of the low-pressure side of the low-temperature stage refrigeration circulation loop in the stable operation state can be different, but the lower limit value of the absolute pressure can be in the range of 0.2-0.8 bar, or 0.2-0.6 bar, or 0.2-0.5 bar, or 0.2-0.4 bar.

The lowest absolute pressure of the low-pressure side of the low-temperature stage refrigeration cycle in a stable operation state can be any value in the range of 0.2-0.8 bar, for example, 0.2bar, 0.3bar, 0.4bar, 0.5bar, 0.6bar, 0.7bar, or 0.8 bar.

The evaporation temperature range of the second refrigerant on the low-pressure side of the low-temperature stage refrigeration cycle circuit in a steady operation state may be configured to be-111 to-35 ℃. The evaporation temperature of the second refrigerant at the low-pressure side in the low-temperature-stage refrigeration cycle circuit may refer to the evaporation temperature of the second refrigerant in the low-temperature-stage evaporator 256. The evaporation temperature of the second refrigerant in the low-temperature-stage evaporator 256 can reach below-60 ℃, or even below-80 ℃, and the second refrigerant can be used for creating a low temperature of about-60 ℃ or even-80 ℃ for the storage compartment 111 in the household small refrigeration equipment 10, so that the fresh-keeping capacity of the household small refrigeration equipment 10 is improved.

In the present embodiment, the evaporation temperature range of the second refrigerant on the low-pressure side of the low-temperature stage refrigeration cycle in the steady operation state may be configured to be-80 to-35 ℃ or-75 to-40 ℃.

The second refrigerant can be pure working medium refrigerant or azeotropic refrigerant, and the standard boiling point range of the second refrigerant can be configured to be-60 to-30 ℃, or-55 to-35 ℃, or-50 to-35 ℃. For example, the second refrigerant may be an R22 refrigerant (normal boiling point may be-40.8 ℃), or may be an R290 refrigerant (normal boiling point may be-42.2 ℃), or may be an R404A refrigerant (normal boiling point may be-46.1 ℃), or may be an R1270 (normal boiling point may be-47.7 ℃), or may be an R410A refrigerant (normal boiling point may be-51.4 ℃), or may be an R32 (normal boiling point may be-51.7 ℃).

The low temperature stage compressor 251 may be an R600a compressor. When the existing R600a compressor is applied to a low-temperature stage refrigeration cycle loop, the low-temperature lubricating oil can be replaced in the R600a compressor, the process is simple, and the cost is low. Since the R600a compressor has low operation noise and high energy efficiency, the noise of the low-temperature stage refrigeration cycle can be reduced and the energy-saving effect can be improved by combining the R600a compressor with the R290 refrigerant.

The type of the low-temperature stage compressor 251 is not limited thereto, and the low-temperature stage compressor 251 may be used as long as the above-described operation performance is provided.

For example, the high-side absolute pressure of the low-temperature stage refrigeration cycle may be 3.022bar and the low-side absolute pressure may be 0.368bar in a steady state operation. The second refrigerant may be R290 refrigerant. The condensation temperature of the second refrigerant at the high-pressure side in the low-temperature-level refrigeration cycle loop can be-12.1 ℃, and the evaporation temperature at the low-pressure side can be-62.8 ℃, so that the low-temperature environment of about-55 ℃ can be created for the storage chamber 111 when the low-temperature-level refrigeration cycle loop operates. The absolute pressure of the low-pressure side of the low-temperature-stage refrigeration circulation circuit in a stable operation state can also be 0.287bar, and the evaporation temperature of the second refrigerant at the low-pressure side in the low-temperature-stage refrigeration circulation circuit can be-67.2 ℃ at the moment, so that a low-temperature environment of about-60 ℃ can be created for the storage chamber 111 during operation of the low-temperature-stage refrigeration circulation circuit.

In some alternative embodiments, the high-side absolute pressure of the low-temperature stage refrigeration cycle may be 3.507bar and the low-side absolute pressure may be 0.287bar at steady state operation. The second refrigerant may be R1270 refrigerant.

The condensing temperature of the second refrigerant on the high-pressure side in the low-temperature stage refrigeration cycle loop can be-16 ℃, and the evaporating temperature on the low-pressure side can be-72 ℃, so that a low-temperature environment of about-65 ℃ can be created for the storage compartment 111 when the low-temperature stage refrigeration cycle loop operates.

In other alternative embodiments, the evaporation temperature range of the second refrigerant at the low-pressure side of the low-temperature stage refrigeration cycle in the steady operation state may be further configured to be-111 to-50 ℃.

The second refrigerant may be a non-azeotropic refrigerant, wherein the second refrigerant may include the first component. The standard boiling point range of the first component can be set to-60-0 ℃, or-50-0 ℃, or-45-0 ℃, or-15-0 ℃. The mass fraction of the first component in the second refrigerant may be set to 20% to 80%.

For example, the second refrigerant may include R600a refrigerant and R170 refrigerant, wherein the first component may be R600a refrigerant, and the mass fraction of the R600a refrigerant in the second refrigerant may be in the range of 30% to 80%, or 40% to 60%. Or the second refrigerant may include R600 refrigerant and R170 refrigerant, wherein the first component may be R600 refrigerant, and the R600 refrigerant may account for 40% to 80% of the mass fraction of the second refrigerant. Or the second refrigerant may include R600a refrigerant and R1150 refrigerant, wherein the first component may be R600a refrigerant, and the R600a refrigerant may account for a mass fraction in the second refrigerant ranging from 40% to 80%. Or the second refrigerant may include R600 refrigerant and R1150 refrigerant, wherein the first component may be R600 refrigerant, and the R600 refrigerant may account for 50% to 80% of the mass fraction of the second refrigerant. Or the second refrigerant can comprise R290 refrigerant and R170 refrigerant, wherein the first component can be R290 refrigerant, and the mass fraction of the R290 refrigerant in the second refrigerant can be 50-70%. Or the second refrigerant can comprise R290 refrigerant and R1150 refrigerant, wherein the first component can be R290 refrigerant, and the mass fraction of the R290 refrigerant in the second refrigerant can be 70-80%. Or the second refrigerant may include R1270 refrigerant and R170 refrigerant, wherein the first component may be R1270 refrigerant, and the mass fraction of R1270 refrigerant in the second refrigerant may be in the range of 60% to 80%. Or the second refrigerant may include R1270 refrigerant and R1150 refrigerant, wherein the first component may be R1270 refrigerant, and the mass fraction of R1270 refrigerant in the second refrigerant may be in a range of 70% to 80%.

An ODP (Ozone Depletion Potential) value of the second refrigerant may be configured to be 0, and a GWP of the second refrigerant may be configured to be 0₁₀₀(GWP was calculated based on 100 years and is reported as GWP₁₀₀Wherein GWP, which is an abbreviation of Global Warming Potential, for representing Global Warming Potential) value may be configured to be 200 or less.

The evaporation temperature range of the first refrigerant at the low-pressure side of the high-temperature refrigeration cycle loop in a stable operation state can be configured to be-40 ℃ to 0 ℃, or-35 ℃ to-10 ℃, or-30 ℃ to-15 ℃. The condensing temperature of the second refrigerant at the high pressure side in the low temperature stage refrigeration cycle circuit is higher than the evaporating temperature of the first refrigerant flowing through the low pressure side in the high temperature stage refrigeration cycle circuit, for example, the condensing temperature of the second refrigerant at the high pressure side in the low temperature stage refrigeration cycle circuit may range from-25 ℃ to-5 ℃.

The first refrigerant in the high-temperature-stage refrigeration cycle circuit absorbs heat of the second refrigerant in the low-temperature-stage refrigeration cycle circuit flowing through the condensation portion 232 when flowing through the evaporation portion, so that the second refrigerant in the condensation portion 232 is cooled and condensed into a liquid state. That is, the high-temperature-stage refrigeration cycle circuit can provide a pre-cooling function for the low-temperature-stage refrigeration cycle circuit by using the first refrigerant, so that the second refrigerant in the low-temperature-stage refrigeration cycle circuit can be converted from a gaseous state to a liquid state. The second refrigerant is evaporated in the low-temperature stage evaporator 256 by heat absorption, and can absorb a large amount of heat, thereby achieving an effective refrigeration function at a lower temperature.

For example, the first refrigerant may be R600a refrigerant and the high temperature stage compressor 211 may be R600a compressor. In the high-temperature-stage refrigeration cycle, the condensation temperature of the first refrigerant on the high-pressure side is higher than the ambient temperature, and the first refrigerant releases heat on the high-pressure side. The first refrigerant flowing through the evaporation part (low pressure side) of the high temperature stage refrigeration cycle circuit may absorb heat of the second refrigerant flowing through the condensation part 232 (high pressure side) of the low temperature stage refrigeration cycle circuit, so that the second refrigerant flowing through the condensation part 232 is condensed.

In the low-temperature stage refrigeration cycle loop, when the ambient temperature is set to be a common indoor temperature, the common indoor temperature can be any value within a range of 7-40 ℃, the exhaust temperature of the low-temperature stage compressor 251 can be set to be less than or equal to 110 ℃ and the shell temperature of the low-temperature stage compressor 251 can be set to be less than or equal to 110 ℃ under the conditions that the suction temperature of the low-temperature stage compressor 251 is 10-38 ℃ and the suction superheat degree of the low-temperature stage compressor 251 is 80-95K (K is a thermodynamic temperature unit). In other alternative embodiments, in the case where the suction temperature of the low-temperature stage compressor 251 is in the range of 15 to 35 ℃, and the suction superheat degree of the low-temperature stage compressor 251 is 80 to 85K (K is a thermodynamic temperature unit), the discharge temperature of the low-temperature stage compressor 251 may be set to 100 ℃ or less, and the shell temperature of the low-temperature stage compressor 251251 may be set to 100 ℃ or less.

The cylinder volume of the low temperature stage compressor 251 can be configured to be less than or equal to 20ml, for example, the cylinder volume of the low temperature stage compressor 251 can be configured to be 4-20 ml, or 5-15 ml, or 8.5-13.5 ml. Wherein, the low temperature stage compressor 251 may be a piston type.

The low-temperature stage refrigeration cycle circuit is not provided with a jet cooling circuit.

The cascade compression refrigeration system may further comprise: and the heat exchange assembly. The heat exchange assembly can be arranged in the low-temperature-stage refrigeration cycle loop. The heat exchange assembly may include a heat discharging member 241 and a heat absorbing member 242. And a heat releasing material 241 disposed between the low-temperature stage compressor 251 and the condensing unit 232. The heat absorbing member 242 is disposed between the low-temperature stage evaporator 256 and the suction port of the low-temperature stage compressor 251. The heat releasing member 241 and the heat absorbing member 242 may be nested or abutted against each other such that the second refrigerant flowing through the heat releasing member 241 may exchange heat with the second refrigerant flowing through the heat absorbing member 242. The heat absorbing member 242 functions to induce the second refrigerant flowing therethrough to absorb heat of the second refrigerant flowing through the heat discharging member 241. The heat absorbing member 242 may be disposed downstream of the heat absorbing portion 272.

In the heat exchange assembly of the present embodiment, the heat exchange assembly may be two copper pipes attached to each other, wherein one copper pipe is the heat absorbing member 242, and the other copper pipe is the heat releasing member 241. The two copper pipes are arranged in a mutual attaching mode. The contact part between the two copper pipes can be fixed by tin soldering to strengthen the heat transfer. The two copper pipes can be wrapped with aluminum foils.

In the low-temperature stage refrigeration cycle circuit, the second refrigerant temperature in a section between the low-temperature stage evaporator 256 and the suction port of the low-temperature stage compressor 251 is low, and the second refrigerant temperature in a section between the discharge port of the low-temperature stage compressor 251 and the condensing portion 232 is high and higher than the second refrigerant temperature flowing through the heat absorbing member 242.

By arranging the heat exchange component, the second refrigerant flowing through the heat absorbing part 242 absorbs the heat of the second refrigerant flowing through the heat releasing part 241, and the second refrigerant in the low-temperature stage refrigeration cycle loop is heated before flowing into the compressor suction inlet, so that the suction temperature of the low-temperature stage compressor 251 can be increased, the loss of cold energy caused by too low suction temperature can be reduced or avoided, the refrigeration efficiency is increased, condensation or frost formation near the suction inlet of the low-temperature stage compressor 251 can be avoided, a series of problems of wet stroke, liquid impact, oil shortage of the low-temperature stage compressor 251 and the like caused by too low suction temperature can be reduced or avoided, and the operation performance of the cascade compression refrigeration system is improved.

The heat releasing member 241 is disposed between the low-temperature-stage compressor 251 and the condensing portion 232, and the second refrigerant flowing through the heat releasing member 241 transfers heat to the second refrigerant flowing through the heat absorbing member 242 and heats the second refrigerant, so that energy utilization efficiency of the low-temperature-stage refrigeration cycle is improved, and energy utilization efficiency of the entire refrigeration apparatus 10 is further improved.

The low temperature stage refrigeration cycle circuit may further include: low temperature grade radiator 252, low temperature grade drier-filter 254, low temperature grade reservoir 257.

The low-temperature stage throttling device 255 is provided between the condensing unit 232 and the low-temperature stage evaporator 256. The low-temperature stage throttling device 255 may be a capillary tube or an expansion valve. The heat radiating portion 271 may be disposed between the condensing portion 232 and the low-temperature-stage throttling device 255.

The low-temperature stage dry filter 254 is provided between the condensing unit 232 and the low-temperature stage throttling device 255, and may be provided between the heat radiating unit 271 and the low-temperature stage throttling device 255, for example. The low-temperature stage filter drier 254 functions to filter impurities in the second refrigerant and prevent the generation of ice blockage.

The low-temperature-stage radiator 252 may be disposed between the discharge port of the low-temperature-stage compressor 251 and the condensing unit 232, for example, between the low-temperature-stage compressor 251 and the heat sink 241. The low-temperature-stage radiator 252 can pre-cool the second refrigerant in the low-temperature-stage refrigeration cycle before flowing to the condensation portion 232, so as to ensure that the second refrigerant can be sufficiently condensed when flowing through the condensation portion 232.

A low temperature stage liquid storage bag 257 is disposed downstream of the low temperature stage evaporator 256 and between the low temperature stage evaporator 256 and the heat absorption return gas pipe segment 258. The low-temperature-stage liquid storage bag 257 can prevent the second refrigerant flowing to the suction port of the low-temperature-stage compressor 251 from carrying liquid second refrigerant, can also adjust the amount of the second refrigerant required by other components in the low-temperature-stage refrigeration cycle circuit, and can prevent the second refrigerant at the low-temperature-stage evaporator 256 from slowly migrating to the suction port of the low-temperature-stage compressor 251 when the low-temperature-stage refrigeration cycle system is stopped.

Figure 3 is a schematic diagram of a cascade compression refrigeration system according to one embodiment of the present invention.

In some alternative embodiments, a return gas pipe segment 258 may be added to the low temperature stage refrigeration cycle loop. The heat absorption low temperature stage refrigeration cycle circuit may further include: the heat absorbing return air pipe section 258. And a heat absorption return pipe section 258 disposed between the low-temperature stage evaporator 256 and the suction port of the low-temperature stage compressor 251. At least part of the heat absorption air return pipe section 258 can be attached to the low-temperature-stage throttling device 255, so that the second refrigerant flowing through the heat absorption air return pipe section 258 absorbs heat of the second refrigerant flowing through the low-temperature-stage throttling device 255, the energy utilization efficiency in the low-temperature-stage refrigeration cycle loop is improved, the energy utilization efficiency of the whole refrigeration equipment 10 is further improved, the temperature of the second refrigerant flowing to the suction port of the low-temperature-stage compressor 251 is favorably improved, and the suction superheat degree of the low-temperature-stage compressor 251 is further improved.

The heat absorbing return piping segment 258 may be disposed between the low temperature stage evaporator 256 and the heat absorbing member 242, for example, may be disposed between the low temperature stage evaporator 256 and the low temperature stage sump 257. The heat absorbing member 242 may be disposed between the heat absorbing return air duct section 258 and the compressor suction inlet. The heat absorbing portion 272 may be disposed between the heat absorbing return 258 and the heat absorbing member 242.

The heat absorption return air pipe section 258, the heat absorption part 272 and the heat absorption part 242 are arranged on the flow path between the low-temperature stage evaporator 256 and the low-temperature stage compressor 251, namely, the flow path between the low-temperature stage evaporator 256 and the low-temperature stage compressor 251 is divided into three different pipe sections, the relative positions of the different pipe sections can be flexibly arranged, the three different pipe sections can respectively exchange heat with different positions in the low-temperature stage refrigeration circulation loop, the air suction temperature of the low-temperature stage compressor 251 is improved, and the energy utilization efficiency of the whole cascade compression refrigeration system is improved.

The heat absorption return gas pipe section 258 may form a double pipe heat exchanger with the low temperature stage throttling device 255, the low temperature stage throttling device 255 may be a pipe pass, and the heat absorption return gas pipe section 258 may be a shell pass. In other alternative embodiments, the heat absorbing return air pipe 258 and the low-temperature-stage throttling device 255 may be two copper pipes abutting against each other, wherein one copper pipe is the heat absorbing return air pipe 258, and the other copper pipe is the low-temperature-stage throttling device 255. The two copper pipes are arranged in a mutual attaching mode. The contact part between the two copper pipes can be fixed by tin soldering to strengthen the heat transfer. The two copper pipes can be wrapped with aluminum foils.

The high-temperature stage refrigeration cycle circuit may further include: an electric switching valve 217, a plurality of cooling branches, a second cooling evaporator 222, an anti-dew pipe 215, and a high temperature stage liquid storage bag. Wherein, the number of the cooling branch can be one or more. The number of the cooling branch circuits of the present embodiment may be plural.

And an electric switching valve 217 having a plurality of valve ports for communicating with one cooling branch line, respectively, the electric switching valve 217 for adjusting a flow path of the first refrigerant therethrough by controllably opening or closing the valve ports. The electrically-operated switching valve 217 serves to switch the flow direction of the first refrigerant so that the first refrigerant flowing therethrough is controllably flowed to the one or more cooling branches. The electrically-operated switching valve 217 may be disposed upstream of the plurality of cooling branches and downstream of the high-temperature stage condenser 212.

A plurality of cooling branches are arranged in parallel, and a branch throttling device 218 is arranged in each cooling branch. The number of cooling branches may be two, three, four or five, or any other number. In this embodiment, the number of the cooling branches may be three, including a first cooling branch, a second cooling branch and a third cooling branch. The bypass restriction 218 may be a capillary tube or an expansion valve, and the arrangement of the restriction is well known to those skilled in the art and will not be described herein.

Wherein, the first cooling branch is provided with a first cooling evaporating pipe 219 and a one-way valve 220 therein. The first refrigerant-cooling evaporation tube 219 serves to promote the first refrigerant flowing therethrough to absorb heat. The first cooling evaporator 219 and the low-temperature stage evaporator 256 are used to cool the same storage compartment 111. For example, first cooling evaporator tube 219 may be used with low temperature stage evaporator 256 for placement within an evaporator installation cavity corresponding to a cryogenic compartment and for cooling the cryogenic compartment. The first cold-supplying evaporator tube 219 and the low-temperature stage evaporator 256 are disposed through the same fin group. The first cooling evaporator 219 and the low-temperature stage evaporator 256 may be disposed adjacent to each other or may be disposed adjacent to each other, but is not limited thereto.

The first cooling evaporation pipe 219 and the low-temperature-stage evaporator 256 are disposed in the same evaporator installation cavity corresponding to one storage compartment 111, and are used for cooling the same storage compartment 111, so that the cooling efficiency of the storage compartment 111 can be improved, and the storage compartment 111 can be cooled rapidly.

When the cascade compression refrigeration system is started to operate, the cooling process of the deep cooling chamber can be divided into an initial stage and a later stage, and the two stages are total. The initial stage can be a process of reducing the temperature of the deep cooling chamber from the ambient temperature to a first preset temperature, and the later stage can be a process of reducing the temperature of the deep cooling chamber from the first preset temperature to a second preset temperature, wherein the first preset temperature is higher than the second preset temperature. The first predetermined temperature may be any value between-10 and-28 deg.C, for example-18 deg.C, and the second predetermined temperature may be any value between-40 and-80 deg.C, for example-55 deg.C. The first cooling evaporator 219 may be used to supply cooling for the early stage and the low temperature stage evaporator 256 may be used to supply cooling for the later stage.

Generally, whether the evaporator is providing cooling is determined by whether the refrigerant circulates therein. For example, whether the first refrigerant flows through the first cooling evaporation pipe 219 or not may be controlled by controlling the electric switching valve 217 (described in detail below), so that whether the first cooling evaporation pipe 219 is cooled or not, and whether the second refrigerant flows through the low temperature stage evaporator 256 or not may be controlled by controlling whether the low temperature stage compressor 251 is turned on or not, so that whether the low temperature stage evaporator 256 is cooled or not may be controlled.

In some alternative embodiments, the first cooling evaporator 219 and the low temperature stage evaporator 256 can also be used to be disposed in an evaporator installation cavity corresponding to the temperature changing compartment and to supply cooling to the temperature changing compartment. The temperature-changing compartment can selectively control the first cooling evaporation pipe 219 or the low-temperature-stage evaporator 256 to supply cooling independently according to actual needs, or control the first cooling evaporation pipe 219 and the low-temperature-stage evaporator 256 to supply cooling together, so that the temperature-changing compartment can obtain different refrigeration effects to meet different refrigeration requirements.

And a check valve 220 disposed downstream of the first cooling evaporation pipe 219, for allowing only the first refrigerant from the first cooling evaporation pipe 219 to flow out in one direction. That is, in the first cooling branch, the check valve 220 serves only to allow the first refrigerant from the upstream thereof to pass therethrough in one direction, and the check valve 220 can function to prevent the first refrigerant downstream of the check valve 220 from passing therethrough in the reverse direction.

When the low-temperature stage compressor 251 is operated, the temperature of the low-temperature stage evaporator 256 is low. Due to the close distance between the low-temperature stage evaporator 256 and the first cooling evaporation pipe 219, the pipe temperature of the first cooling evaporation pipe 219 is also low, and even can be significantly lower than that of other cooling evaporators in the high-temperature stage refrigeration cycle circuit, which are located downstream of the first cooling evaporation pipe 219. The one-way valve 220 arranged at the downstream of the first cooling evaporation pipe 219 is arranged in the first cooling branch, so that the first refrigerant in other cooling evaporators at the downstream of the first cooling evaporation pipe 219 can be prevented from flowing into the first cooling evaporation pipe 219 from the discharge port of the first cooling evaporation pipe 219, the first refrigerant in the high-temperature-stage refrigeration circulation loop can be prevented from flowing reversely, the effective circulation amount of the first refrigerant is ensured, and the overall refrigeration efficiency is improved.

The second cooling branch can be internally provided with no cooling evaporator or evaporating pipe for cooling the storage compartment.

A third cooling evaporator 221 may be disposed in the third cooling branch, and the third cooling evaporator 221 may be configured to be disposed in an evaporator installation cavity corresponding to the refrigerating compartment and configured to supply cooling to the refrigerating compartment.

And a second cooling evaporator 222 disposed between the high-temperature-stage condenser 212 and the suction port of the high-temperature-stage compressor 211, for causing the first refrigerant from the plurality of cooling branches to pass to the suction port of the high-temperature-stage compressor 211. The second cooling evaporator 222 is also used for promoting the first refrigerant flowing through the second cooling evaporator to absorb heat, so that the storage compartment 111 where the second cooling evaporator 222 is located is cooled. The second cooling evaporator 222 may be adapted to be disposed in an evaporator installation cavity corresponding to the freezing compartment and to supply cooling to the freezing compartment.

The evaporation portion 231 may be disposed between the high-temperature-stage condenser 212 and the second cooling evaporator 222, and the plurality of cooling branches may be disposed between the high-temperature-stage condenser 212 and the evaporation portion 231. That is, the plurality of cooling branches may be located downstream of the high temperature stage condenser 212 and upstream of the evaporation portion 231, and the second cooling evaporator 222 may be located downstream of the evaporation portion 231 and upstream of the suction port of the high temperature stage compressor 211.

The first cooling evaporator 219 and the third cooling evaporator are disposed between the high-temperature-stage condenser 212 and the evaporation portion 231, the second cooling evaporator is disposed between the evaporation portion 231 and the suction port of the high-temperature-stage compressor 211, and each evaporator or evaporator tube causes the first refrigerant flowing through the evaporator or evaporator tube to evaporate and absorb heat and supply cooling to the storage compartment 111, so that the cooling capacity generated in the high-temperature-stage cooling circulation loop is fully utilized, the energy utilization efficiency of the high-temperature-stage cooling circulation loop is improved, and further the energy utilization efficiency of the whole cooling device 10 is improved.

And the dew prevention pipe 215 is arranged between the high-temperature-stage condenser 212 and the cooling branch and is used for promoting the first refrigerant flowing through the dew prevention pipe to release heat, so that the environmental space where the dew prevention pipe 215 is located is heated. The dew condensation preventing pipe 215 may be used to be disposed at an edge portion around the door body of the refrigeration apparatus 10. When the cascade compression refrigeration system operates, the first refrigerant discharges heat when flowing through the anti-dew pipe 215, so that the anti-dew pipe 215 heats up and generates heat, the phenomenon of dew formation at the edge of the door body of the refrigeration equipment 10 can be reduced or avoided, the edge of the door body of the refrigeration equipment 10 is kept dry, and the problems that the box body 110 is not tightly sealed due to rusting at the edge of the door body and the like can be avoided.

The high temperature stage reservoir may include a high temperature stage first reservoir and a high temperature stage second reservoir 223. The high-temperature-stage first receiver is disposed between the high-temperature-stage condenser 212 and the dew condensation preventing pipe 215, and is configured to adjust an amount of the first refrigerant required by other components (e.g., the high-temperature-stage condenser 212, the evaporation portion 231, or an evaporation pipe or an evaporator for cooling) in the high-temperature-stage refrigeration cycle. The flow rate of the first refrigerant required by each component in the high-temperature stage refrigeration cycle circuit can be different under different working conditions. The high temperature stage first receiver can be controlled to increase the liquid level when the first refrigerant flow required by other components in the high temperature stage refrigeration cycle is reduced. The high temperature stage first receiver may also be controllably adjusted down in liquid level as the first refrigerant flow required by other components within the high temperature stage refrigeration cycle circuit increases. The high-temperature first liquid storage bag is a high-pressure liquid storage bag. When the high-temperature-stage refrigeration cycle system stably operates, the first refrigerant entering the high-temperature-stage first liquid storage bag is usually in a saturated liquid state.

And a high-temperature-stage second reservoir 223 provided between the second cooling evaporator 222 and the suction port of the high-temperature-stage compressor 211. The high-temperature-stage second liquid storage bag 223 can prevent the first refrigerant flowing to the suction port of the high-temperature-stage compressor 211 from carrying the liquid first refrigerant, can also adjust the flow rate of the first refrigerant required by other components in the high-temperature-stage refrigeration cycle circuit, and can also prevent the first refrigerant at the second cooling evaporator 222 from slowly migrating to the suction port of the high-temperature-stage compressor 211 when the high-temperature-stage refrigeration cycle system is stopped.

The high-temperature stage refrigeration cycle circuit may further include: and a high-temperature stage dry filter 216 disposed between the dew condensation preventing pipe 215 and the electric switching valve 217. The high-temperature stage filter drier 216 functions to filter impurities in the first refrigerant and prevent ice blockage.

In this embodiment, in the high-temperature-stage refrigeration cycle loop, the first refrigerant may sequentially flow through the discharge port of the high-temperature-stage compressor 211, the high-temperature-stage condenser 212, the high-temperature-stage first reservoir, the dew prevention pipe 215, the drying filter 216, the electric switching valve 217, the plurality of cooling branches (including the branch throttle 218, the first cooling evaporation pipe 219, the check valve 220, and the third cooling evaporator 221), the evaporation portion 231, the second cooling evaporator 222, the high-temperature-stage second reservoir 223, and the suction port of the high-temperature-stage compressor 211, thereby forming a complete cycle.

In other alternative embodiments, a plurality of cooling branches may also be disposed between the high-temperature stage condenser 212 and the second cooling evaporator 222, for example, the electric switching valve 217 and the cooling branch may be disposed between the high-temperature stage dry filter 216 and the second cooling evaporator 222, and the evaporation portion 231 may be disposed within the second cooling branch. The first cooling branch may be provided with a first cooling evaporating pipe 219 and a check valve 220. Any evaporating pipe or evaporator may not be arranged in the third cooling branch.

A heat dissipation fan 280 for inducing airflow to flow through the low-temperature-stage heat sink 252 after flowing through the high-temperature-stage condenser 212, or inducing airflow to flow through the high-temperature-stage condenser 212 after flowing through the low-temperature-stage heat sink 252, or inducing airflow to flow through the low-temperature-stage heat sink 252 and the high-temperature-stage condenser 212, respectively. The low temperature stage radiator 252 may be disposed adjacent to the high temperature stage condenser 212, and the radiator fan 280 may be disposed at one side of the low temperature stage radiator 252 and the high temperature stage condenser 212. The cooling fan 280 can increase the wind speed and the wind volume flowing through the low-temperature-stage radiator 252 and the high-temperature-stage condenser 212, so as to promote the low-temperature-stage radiator 252 and the high-temperature-stage radiator to quickly dissipate heat, thereby enhancing the heat dissipation effect, and enabling the cascade compression refrigeration system and the refrigeration device 10 with the cascade compression refrigeration system to continuously work within a normal temperature range.

The temperature of the low temperature stage radiator 252 is lower than the temperature of the high temperature stage condenser 212. The low-temperature-stage radiator 252 and the high-temperature-stage condenser 212 are arranged adjacent to each other, and the same heat dissipation fan 280 can promote the formation of air flow which firstly flows through the low-temperature-stage radiator 252 and then flows through the high-temperature-stage condenser 212, so that the heat dissipation effects of the low-temperature-stage radiator 252 and the high-temperature-stage condenser 212 are ensured, the arrangement number of the heat dissipation fans 280 is simplified, the structure miniaturization is facilitated, and the cascade compression refrigeration system of the embodiment can be applied to the household small refrigeration equipment 10.

The air supply blower 290, which may be plural, is respectively disposed corresponding to one evaporator installation cavity, and is used for blowing cool air to each storage compartment 111. The plurality of air supply fans may include a first air supply fan, may be disposed at one side of the first cooling evaporation pipe 219 and the low-temperature stage evaporator 256, and serve to guide the air flow passing through the first cooling evaporation pipe 219 and the low-temperature stage evaporator 256 to the locker room 111.

In some alternative embodiments, the storage compartment 111 of the refrigeration device 10 may be three, and respectively a refrigerating compartment, a freezing compartment and a deep-cooling compartment. The second refrigerant may be a non-azeotropic refrigerant, and may include R600a refrigerant and R170 refrigerant, wherein the first component is R600a refrigerant, and the R600a refrigerant may account for 50% by mass of the second refrigerant. With the cascade compression refrigeration system shown in fig. 3, after the cascade compression refrigeration system is started, the high-temperature stage compression refrigeration cycle loop may be started first. The valve port of the electric switching valve 217 may be simultaneously communicated with the first cooling branch, the second cooling branch, and the third cooling branch. The third cooling evaporator 221 operates and may supply cold to the refrigerating compartment, and the second cooling evaporator 222 operates and may supply cold to the freezing compartment. First cooling evaporator 219 operates and may provide cooling for the cryogenic compartment. When the temperature of the deep cooling chamber reaches a first preset temperature, the valve port of the driving electric switching valve 217 communicated with the first cold supply branch is closed. The first cooling evaporation pipe 219 stops operating. At this point, the low stage refrigeration cycle may be on, and low stage evaporator 256 is running and supplying cold to the cryogenic compartment.

The absolute pressure of the high-pressure side of the low-temperature stage refrigeration cycle in a stable operation state can be 7.8bar, the dew point temperature of the second refrigerant at the absolute pressure can be 18.5 ℃, and the bubble point temperature can be-25.1 ℃. The low-pressure side absolute pressure of the low-temperature stage refrigeration cycle in a stable operation state can be 0.4bar, the dew point temperature of the second refrigerant at the pressure can be-52.7 ℃, and the bubble point temperature can be-97.5 ℃. In the case where the ambient temperature is 32 ℃, the suction temperature of the low temperature stage compressor 251 (corresponding to the temperature at 1 in fig. 3) may be approximately 32 ℃, and the discharge temperature of the low temperature stage compressor 251 (corresponding to the temperature at 2 in fig. 3) may be 90 to 110 ℃. The heat rejection blower 280 may utilize ambient air to reject heat from the low temperature stage heat sink 252. The temperature at the discharge outlet of low temperature stage radiator 252 (corresponding to the temperature at 3 in fig. 3) may be approximately 37 deg.c, and the superheat of the second refrigerant flowing out of the discharge outlet of low temperature stage radiator 252 is high. The temperature of the second refrigerant flowing through the heat discharging member 241 may be lowered, for example, to-1.9 ℃, and the second refrigerant flowing through the discharge port of the heat discharging member 241 may be in a gas-liquid two-phase state. The evaporation temperature of the first refrigerant in the evaporation portion of the high-temperature stage refrigeration cycle circuit may be-25 ℃. The temperature of the second refrigerant after flowing through the condensing portion 232 may be significantly reduced, for example, to-20 ℃, and the second refrigerant flowing through the discharge port of the condensing portion 232 may also be in a gas-liquid two-phase state, but the specific gravity of the liquid second refrigerant is increased. The second refrigerant flowing through the heat radiating portion 271 exchanges heat with the second refrigerant having a lower temperature flowing through the heat absorbing portion 272 to be cooled, and for example, the temperature of the second refrigerant flowing through the discharge port of the heat radiating portion 271 (corresponding to the temperature at 6 in fig. 3) may be reduced to-80 ℃. The second refrigerant flowing through the discharge port of the heat radiating portion 271 may be a supercooled liquid state. The pressure at low-temperature-stage throttling device 255 may be approximately 0.4bar, the temperature of the second refrigerant flowing through the discharge port of low-temperature-stage throttling device 255 may be further reduced, for example, by-96.5 ℃ (corresponding to the temperature at 7 in fig. 3), and the second refrigerant at this time may be a gas-liquid two-phase refrigerant containing a small amount of gaseous refrigerant. The second refrigerant with lower temperature absorbs heat when flowing through the low-temperature stage evaporator 256 and supplies cold for the cryogenic compartment, so that the temperature of the cryogenic compartment can reach-80 ℃. The second refrigerant temperature flowing through the discharge port of the low temperature stage evaporator 256 may be approximately-85 deg.c (gas-liquid two-phase). The temperature of the second refrigerant flowing through the discharge port of the heat absorbing part 272 may be raised to approximately-58.9 c (gas-liquid two-phase). The second refrigerant flowing through the heat absorbing member 242 absorbs heat of the second refrigerant flowing through the heat releasing member 241 to be heated, and the second refrigerant flowing through the discharge port of the heat absorbing member 242 may be in a superheated full gas state, and may have a temperature approximately close to the ambient temperature of 32 ℃.

In other alternative embodiments, the second refrigerant may be replaced. For example, with the cascade compression refrigeration system shown in fig. 3, the second refrigerant may be a non-azeotropic refrigerant consisting of R600a refrigerant and R1150 refrigerant, wherein the first component is R600a refrigerant, and the mass fraction of R600a refrigerant in the second refrigerant may be in the range of 50% to 80%, and preferably, may be 60%.

The absolute pressure of the high-pressure side of the low-temperature stage refrigeration cycle in a stable operation state can be 7.8bar, the dew point temperature of the second refrigerant at the absolute pressure can be 22.8 ℃, and the bubble point temperature can be-39.6 ℃. The low-pressure side absolute pressure of the low-temperature stage refrigeration cycle in a steady operation state may be 0.4bar, the dew point temperature of the second refrigerant at the pressure may be-49.7 ℃, and the bubble point temperature may be-109.4 ℃. In the case where the ambient temperature is 32 ℃, the suction temperature of the low temperature stage compressor 251 (corresponding to the temperature at 1 in fig. 3) may be approximately 32 ℃, and the discharge temperature of the low temperature stage compressor 251 (corresponding to the temperature at 2 in fig. 3) may be 95 to 115 ℃. The temperature at the discharge outlet of low temperature stage radiator 252 (corresponding to the temperature at 3 in fig. 3) may be approximately 37 deg.c, and the superheat of the second refrigerant flowing out of the discharge outlet of low temperature stage radiator 252 is high. The temperature of the second refrigerant flowing through the heat discharging member 241 may be lowered, for example, to-5.7 ℃, and the second refrigerant flowing through the discharge port of the heat discharging member 241 may be in a gas-liquid two-phase state. The evaporation temperature of the first refrigerant in the evaporation portion of the high-temperature stage refrigeration cycle circuit may be-25 ℃. The temperature of the second refrigerant after flowing through the condensing portion 232 may be significantly reduced, for example, to-20 ℃, and the second refrigerant flowing through the discharge port of the condensing portion 232 may also be in a gas-liquid two-phase state, but the specific gravity of the liquid second refrigerant is increased. The second refrigerant flowing through the heat radiating portion 271 exchanges heat with the second refrigerant having a lower temperature flowing through the heat absorbing portion 272 to be cooled, and for example, the temperature of the second refrigerant flowing through the discharge port of the heat radiating portion 271 (corresponding to the temperature at 6 in fig. 3) may be reduced to-80 ℃. The second refrigerant flowing through the discharge port of the heat radiating portion 271 may be a supercooled liquid state. The pressure at low-temperature-stage throttling device 255 may be approximately 0.4bar, the temperature of the second refrigerant flowing through the discharge port of low-temperature-stage throttling device 255 may be further reduced, for example, may be-106.7 ℃ (corresponding to the temperature at 7 in fig. 3), and the second refrigerant at this time may be a gas-liquid two-phase refrigerant containing a small amount of gaseous refrigerant. The second refrigerant with lower temperature absorbs heat when flowing through the low-temperature stage evaporator 256 and supplies cold for the cryogenic compartment, so that the temperature of the cryogenic compartment can reach-80 ℃. The second refrigerant temperature flowing through the discharge port of the low temperature stage evaporator 256 may be approximately-85 deg.c (gas-liquid two-phase). The temperature of the second refrigerant flowing through the discharge port of the heat absorbing part 272 may be increased to approximately-53 c (gas-liquid two-phase). The second refrigerant flowing through the heat absorbing member 242 absorbs heat of the second refrigerant flowing through the heat discharging member 241 to be heated, and the second refrigerant flowing through the discharge port of the heat absorbing member 242 may be in a superheated full gas state, and may have a temperature approximately close to the ambient temperature of 32 ℃, and may flow into the low-temperature stage compressor 251 to perform a cycle.

Figure 4 is a schematic diagram of a cascade compression refrigeration system according to one embodiment of the present invention. Fig. 5 is a pressure-enthalpy diagram corresponding to the operation state of the low-temperature stage refrigeration cycle in the cascade compression refrigeration system shown in fig. 4. The ordinate of the diagram represents absolute pressure and the abscissa represents specific enthalpy.

In some alternative embodiments, the heat exchange means within the low temperature stage refrigeration cycle loop may be omitted.

The first refrigerant becomes a high-temperature high-pressure gaseous first refrigerant under the action of the high-temperature stage compressor 211, then enters the high-temperature stage condenser 212, and is condensed into a high-pressure liquid-containing first refrigerant, the first refrigerant flowing out of the high-temperature stage condenser 212 can flow through the branch throttling device 218, is converted into a low-pressure first refrigerant, then enters the evaporation part 231, the first cooling evaporation pipe 219, the third cooling evaporator 221, and/or the second cooling evaporator 222 to absorb heat, and finally flows into the suction port of the high-temperature stage compressor 211, so that a complete high-temperature stage refrigeration cycle is formed.

In the low-temperature stage refrigeration cycle circuit, the second refrigerant may sequentially flow through a discharge port of the low-temperature stage compressor 251, the low-temperature stage radiator 252, the heat release member 241, the condensation portion 232, the low-temperature stage filter drier 254, the low-temperature stage throttling device 255, the low-temperature stage evaporator 256, the low-temperature stage liquid storage bag 257, the heat absorption return pipe 258, the heat absorption member 242, and a suction port of the low-temperature stage compressor 251 to form a complete cycle.

The low-temperature stage compressor 251 sucks the second refrigerant (corresponding to point 1 in fig. 4 and 5) at normal temperature and low pressure, and the second refrigerant is changed into a gaseous second refrigerant at high temperature and high pressure by the low-temperature stage compressor 251. The second refrigerant (corresponding to point 2 in fig. 4 and 5) flowing out of the discharge port of the low temperature stage compressor 251 may flow through the low temperature stage radiator 252. After the second refrigerant flows through the low-temperature stage heat sink 252 to dissipate heat (corresponding to point 3 in fig. 4 and 5), the temperature may be close to the ambient temperature but still be a superheated gas, i.e., the superheat of the second refrigerant may be reduced during the flow through the low-temperature stage heat sink 252. The second refrigerant flowing out of the discharge port of the low temperature stage heat spreader 252 may flow through the heat releasing member 241 of the heat exchange assembly and transfer a portion of heat to the second refrigerant in the heat absorbing member 242 in the heat releasing member 241, thereby heating the second refrigerant in the heat absorbing member 242. After the second refrigerant flows through the heat releasing member 241 to release heat (corresponding to point 4 in fig. 4 and 5), the temperature may be close to the ambient temperature but still be a superheated gas, and the degree of superheat of the second refrigerant may be reduced during the process of flowing through the heat releasing member 241. The second refrigerant flowing out of the heat releasing member 241 may enter the condensing portion 232, be condensed into a high-pressure liquid-containing second refrigerant (corresponding to point 5 in fig. 4 and 5), flow through the low-temperature stage throttling device 255, be converted into a low-pressure gas-liquid two-phase second refrigerant (corresponding to point 6 in fig. 4 and 5), and then enter the low-temperature stage evaporator 256 to absorb heat and be evaporated into a low-pressure gaseous second refrigerant. It should be noted that "gaseous" herein means that most of the second refrigerant is in a gaseous state, and does not mean that all of the second refrigerant is in a gaseous state, that is, the second refrigerant after passing through the low-temperature stage evaporator 256 may carry liquid second refrigerant. If the second refrigerant after flowing through the low-temperature-stage evaporator 256 carries the liquid second refrigerant, the low-temperature-stage refrigeration cycle is configured to enhance the heat exchange efficiency between the low-temperature-stage throttling device 255 and the heat-absorbing return-air pipe 258 (i.e., enhance the heat recovery). After the second refrigerant (corresponding to point 7 in fig. 4 and 5) output from the low-temperature stage evaporator 256 enters the heat-absorbing return pipe section 258 and absorbs heat of the second refrigerant flowing through the low-temperature stage throttling device 255 (corresponding to point 8 in fig. 4 and 5), the temperature can be increased but the superheat degree is low. After the second refrigerant enters the heat absorbing member 242 of the heat exchange assembly, the temperature may be raised to approximately ambient temperature with a corresponding increase in superheat. The second refrigerant from the heat absorbing member 242 may flow into the suction port of the low temperature stage compressor 251 to form a complete low temperature stage refrigeration cycle.

Fig. 6 is a schematic view of a cascade compression refrigeration system according to another embodiment of the present invention, wherein the direction of the arrows show the direction of heat transfer.

In other alternative embodiments, the heat exchange assembly may be a double pipe heat exchanger. The heat absorbing member 242 may be a shell side of a double-tube heat exchanger, and the heat releasing member 241 may be a tube side of the double-tube heat exchanger. In alternative embodiments, the heat absorbing member 242 may be tube-side and the heat releasing member 241 may be shell-side.

In another alternative embodiment, the position of the heat emitting member 241 of the heat exchange assembly may be changed. The heat releasing member 241 of the heat exchanging assembly may be disposed in the high-temperature stage refrigeration cycle circuit between the high-temperature stage condenser 212 and the evaporation portion 231, for example, between the high-temperature stage condenser 212 and the plurality of cooling branches. The position of the heat absorbing member 242 of the heat exchange assembly may be constant. The heat absorbing member 242 may be disposed between the low temperature stage evaporator 256 and the low temperature stage compressor 251 suction inlet, for example, between the suction recuperator section and the low temperature stage compressor 251 suction inlet. The heat absorbing member 242 functions to induce the second refrigerant flowing therethrough to absorb heat of the first refrigerant flowing through the heat discharging member 241, so that the second refrigerant in the low-temperature stage refrigeration cycle circuit is warmed before flowing into the compressor suction port, thereby enabling to increase the suction superheat of the low-temperature stage compressor 251.

Since the temperature of the first refrigerant flowing out of the high-temperature-stage condenser 212 is higher than the temperature of the second refrigerant between the low-temperature-stage evaporator 256 and the suction port of the low-temperature-stage compressor 251, the second refrigerant flowing through the heat absorbing member 242 can absorb the heat of the first refrigerant flowing through the heat releasing member 241 to increase the temperature, thereby increasing the supercooling degree of the first refrigerant, and thus improving the energy utilization efficiency of the high-temperature-stage refrigeration cycle.

For the throttling device, the above embodiment is only illustrated by a capillary tube, but the throttling device in the above embodiment should not be regarded as being limited to the capillary tube.

The cascade compression refrigeration system of the present embodiment and the refrigeration equipment 10 having the same, wherein the cascade compression refrigeration system includes a high-temperature-stage refrigeration cycle circuit, a first refrigerant, a low-temperature-stage refrigeration cycle circuit, and a second refrigerant. The absolute pressure range of the high pressure side of the low-temperature stage refrigeration circulation loop in a stable operation state is configured to be 2-11 bar, and the absolute pressure range of the low pressure side of the low-temperature stage refrigeration circulation loop in the stable operation state is configured to be 0.2-1.1 bar, so that the low-temperature stage compressor 251 in the low-temperature stage refrigeration circulation loop can have lower suction pressure and lower exhaust pressure when the low-temperature stage refrigeration circulation loop operates, the noise generated during operation can be effectively reduced, and the low-temperature stage refrigeration circulation loop can be suitable for household small refrigeration equipment.

Thus, it should be appreciated by those skilled in the art that while a number of exemplary embodiments of the invention have been illustrated and described in detail herein, many other variations or modifications consistent with the principles of the invention may be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be understood and interpreted to cover all such other variations or modifications.

Claims

1. A cascade compression refrigeration system comprising:

a high-temperature-stage refrigeration cycle including a first refrigerant that flows through the interior thereof;

a low-temperature-stage refrigeration cycle including a second refrigerant that flows through the interior thereof; the low-temperature-stage refrigeration circulation loop is also internally provided with a condensing part which is used for promoting the heat exchange between the second refrigerant flowing through the condensing part and the first refrigerant flowing through the evaporating part in the high-temperature-stage refrigeration circulation loop;

2. The cascade compression refrigeration system of claim 1 wherein

The absolute pressure range of the high-pressure side of the low-temperature stage refrigeration cycle loop in a stable operation state is configured to be 2-9 bar;

the value range of the lower limit value of the absolute pressure of the low-pressure side of the low-temperature stage refrigeration cycle loop in a stable operation state is configured to be 0.2-0.8 bar, or 0.2-0.6 bar, or 0.2-0.5 bar, or 0.2-0.4 bar.

3. The cascade compression refrigeration system of claim 1 wherein

The evaporation temperature range of the second refrigerant on the low-pressure side of the low-temperature stage refrigeration cycle circuit in a stable operation state is set to-111 to-35 ℃.

4. The cascade compression refrigeration system of claim 3 wherein

The evaporation temperature range of the second refrigerant at the low-pressure side of the low-temperature stage refrigeration cycle loop in a stable operation state is set to be-80 to-35 ℃ or-75 to-40 ℃.

5. The cascade compression refrigeration system of claim 4 wherein

The second refrigerant is pure working medium refrigerant or azeotropic refrigerant, and the standard boiling point range of the second refrigerant is configured to be-60 to-30 ℃, or-55 to-35 ℃, or-50 to-35 ℃.

6. The cascade compression refrigeration system of claim 3 wherein

The evaporation temperature range of the second refrigerant on the low-pressure side of the low-temperature stage refrigeration cycle circuit in a stable operation state is set to-111 to-50 ℃.

7. The cascade compression refrigeration system of claim 6 wherein

The second refrigerant is a non-azeotropic refrigerant, wherein the second refrigerant comprises a first component;

the standard boiling point range of the first component is-60-0 ℃, or-50-0 ℃, or-45-0 ℃, or-15-0 ℃;

the mass fraction of the first component in the second refrigerant is set to 20% to 80%.

8. The cascade compression refrigeration system of claim 1 wherein

The ODP value of the second refrigerant is set to 0, and the GWP of the second refrigerant₁₀₀The value is configured to be 200 or less.

9. The cascade compression refrigeration system of claim 1 wherein

The evaporation temperature range of the first refrigerant at the low-pressure side of the high-temperature stage refrigeration cycle loop in a stable operation state is set to be-40 ℃ to 0 ℃, or-35 ℃ to-10 ℃, or-30 ℃ to-15 ℃.

10. The cascade compression refrigeration system of claim 1 wherein

Under the condition that the suction temperature range is 10-38 ℃ and the suction superheat degree range of a low-temperature stage compressor in the low-temperature stage refrigeration circulation loop is 80-95K, the exhaust temperature of the low-temperature stage compressor is set to be less than or equal to 110 ℃; or

And under the condition that the suction temperature range is 15-35 ℃ and the suction superheat degree range of the low-temperature stage compressor is 80-85K, the exhaust temperature of the low-temperature stage compressor is set to be less than or equal to 100 ℃.

11. The cascade compression refrigeration system of claim 1 wherein

The cylinder volume range of a low-temperature stage compressor in the low-temperature stage refrigeration cycle loop is configured to be 4-20 ml, or 5-15 ml, or 8.5-13.5 ml.

12. The cascade compression refrigeration system of claim 1 wherein the low temperature stage refrigeration cycle comprises:

a low temperature stage compressor;

a low-temperature stage throttling device and a low-temperature stage evaporator, which are arranged between the condensing part and the suction inlet of the low-temperature stage compressor, and the low-temperature stage throttling device is arranged at the upstream of the low-temperature stage evaporator;

a heat exchange device, comprising:

a heat releasing unit disposed between the condensing unit and the low-temperature-stage throttling device;

a heat absorption portion disposed between the low-temperature-stage evaporator and the low-temperature-stage compressor suction port, the heat absorption portion configured to cause the second refrigerant flowing therethrough to absorb heat of the second refrigerant flowing through the heat release portion.

13. A refrigeration appliance comprising:

a box body;

the cascade compression refrigeration system of any one of claims 1-12 disposed within the tank.