Refrigerant mixture applied to ultralow-temperature refrigerating system and refrigerating system

Abstract

According to the refrigerant mixture applied to the ultralow-temperature refrigerating system and the refrigerating system, the refrigerant mixture composed of R600a, R1150 and R50 with the preset mass ratio is configured, the air suction pressure and the air exhaust pressure of a compressor are controlled, the structure of an evaporator is improved, the inner diameter of a capillary tube is controlled, and therefore the refrigerant mixture can be applied to the ultralow-temperature refrigerating system. R600a and R1150 in a gaseous refrigerant mixture are converted into liquid through the first refrigeration pipeline, and the temperature of the refrigerant mixture is firstly reduced to-45 DEG C through throttling and pressure reduction of the capillary tube with the inner diameter of 0.75 mm, so that the ultralow-temperature overall control time is shortened. And the gaseous R50 is converted into the liquid state through the second refrigeration pipeline and multiple times of suction and exhaust circulation of the compressor, so that the refrigerant mixture of-45 DEG C can be rapidly reduced to about-85 DEG C. By means of the evaporator with the improved structure, consumption of gap air on cooling capacity is reduced, it is ensured that the evaporator can accurately control the temperature of a refrigerant mixture of about-85 DEG C to about-82 DEG C, and the requirement for rapid control over the ultralow temperature of-80 DEG C in a small-size refrigerator is met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ultra-low temperature refrigeration, in particular to a refrigerant mixture applied to an ultra-low temperature refrigeration system and a refrigeration system. BACKGROUND

[0002] It is a major technical problem in the field to achieve and maintain the temperature in a small-sized refrigerator (such as a household refrigerator, a freezer, etc.) at below -80℃ in a normal temperature environment (such as 25℃). An evaporator is an important cooling device in a refrigerator, and to achieve a temperature of below -80℃ in the refrigerator means that the evaporation temperature should be below -85℃, which brings higher difficulty to the ultra-low temperature control in the refrigerator.

[0003] Currently, the ultra-low temperature control technology for small-sized refrigerators focuses on the following two directions: 1. Improving the refrigeration performance of each device in the refrigerator, such as improving the performance of the evaporator, the heat exchanger, etc. by changing the structure and direction of the pipeline to improve the refrigeration effect.

[0004] 2. Improving the refrigerant ratio so that the refrigerant mixture has the ability to achieve a temperature of -80℃ in the refrigerator.

[0005] However, the above two technical directions have the following two problems: 1) Due to the limited space in the small-sized refrigerator, it is almost impossible to achieve a temperature of below -80℃ in the refrigerator by only changing the internal pipeline structure and direction. Moreover, there is currently a lack of evaporators and other devices that can achieve a temperature of -80℃ in the small-sized refrigerator.

[0006] 2) The improvement process of the refrigerant ratio is very complex, and there is little research on the refrigerant ratio for the ultra-low temperature control of -80℃ in small-sized refrigerators. The main difficulties are as follows: (1) The production cost should be taken into account. For example, currently, ordinary freezers generally use R600a (isobutane C4H10) refrigerant, and the boiling point temperature of R600a at one standard atmosphere is -11.75℃. The evaporator temperature can reach about -35℃, and the temperature in the refrigerator can only reach about -33℃, which is far from -80℃. However, R600a has low use cost, and if it can continue to be applied in the ultra-low temperature control of -80℃, it can effectively ensure the low cost of refrigerator production.

[0007] (2) In the ultra-low temperature control research of -80℃ for small-sized refrigerators, if only the refrigerant mixture is relied on to play a role, the refrigeration time will be greatly increased, which is not conducive to quickly reducing the temperature in the refrigerator from normal temperature to -80℃ in a short time. Moreover, even if such a refrigerant mixture is developed, the cost will most likely be high, which is not conducive to controlling the production cost of the refrigerator. SUMMARY

[0008] The application is based on the two technical directions of the above-mentioned-80℃ ultra-low temperature control research on small-sized refrigerators, on the basis of improving the physical structure in the box to facilitate the maintenance of-80℃ ultra-low temperature control, mixing and matching the conventional refrigerant to jointly play a role in achieving the-80℃ ultra-low temperature control requirement in the box in a short time, and improving the physical structure to reduce the difficulty of mixed refrigerant matching, shorten the ultra-low temperature control time, and improve the precision of maintaining-80℃ ultra-low temperature. A refrigerant mixture and a refrigeration system applied to an ultra-low temperature refrigeration system are provided.

[0009] To achieve this purpose, the following technical solutions are adopted in the application: An ultra-low temperature refrigeration system is provided, comprising: A compressor for controlling the suction and / or discharge pressure of the refrigerant mixture flowing in the pipeline within a preset pressure range; A heat exchanger for heat exchanging the refrigerant mixture flowing under the condition of the preset pressure range, to obtain liquid R600a and liquid R1150, so as to reduce the temperature of the heat-exchanged refrigerant mixture to a preset first threshold temperature range; A main capillary tube with a preset inner diameter for throttling and reducing the pressure of the refrigerant mixture flowing out of the heat exchanger, so as to reduce the temperature of the refrigerant mixture to a preset second threshold temperature range and deliver it to the evaporator; An evaporator, which is flattened and bonded to the inner tank of the refrigerator after the copper tube in the evaporator is flattened, for absorbing heat of the refrigerant mixture in the second threshold temperature range to maintain the temperature in the box within a preset third threshold temperature range.

[0010] Preferably, the refrigerant mixture comprises R600a, R1150 and R50, and the mass ratio of R600a and R1150 is 1.78:1~1.85:1, and the mass ratio of R1150 and R50 is 22.8:1~23.5:1.

[0011] Preferably, the mass proportion of R600a, R1150 and R50 is 65±2%, 35±1% and 2±0.5% respectively.

[0012] Preferably, the suction pressure range of the compressor is 0.8-0.9 Kgf / cm^2, and the discharge pressure range of the compressor is 15-16 Kgf / cm^2.

[0013] Preferably, the temperature of the refrigerant mixture is controlled in the first threshold temperature range by a first refrigeration pipeline, and the first refrigeration pipeline comprises: The compressor is used to discharge the refrigerant mixture composed of R600a, R1150 and R50 with a set mass ratio into the anti-dew pipe at an exhaust pressure in a set exhaust pressure range; The anti-dew pipe is connected with the compressor by a pipeline, at Prevent ice from forming around the door of the refrigerator when the refrigerator is powered for a long time, and prevent ice from sticking to the door seal, causing the door to be unable to be opened; The condenser is connected with the anti-dew pipe by a pipeline, and is used to release heat from the refrigerant mixture flowing out of the anti-dew pipe and then deliver the refrigerant mixture to the dry filter; The dry filter is connected with the condenser by a pipeline, and is used to dry and filter the refrigerant mixture flowing in; The vapor-liquid separator is connected with the dry filter by a pipeline, and is used to separate the refrigerant mixture flowing in into a liquid phase and a gas phase to obtain liquid R600a with a mass ratio of 95% of gaseous R600a discharged by the compressor.

[0014] Preferably, the first refrigeration pipeline further comprises: The sub-capillary tube is used to throttle and depressurize the liquid R600a flowing from the vapor-liquid separator and then deliver the liquid R600a to the heat exchanger; The heat exchanger is connected with the sub-capillary tube and the compressor by a pipeline, and is used to exchange heat between the liquid R600a flowing out of the sub-capillary tube and the refrigerant mixture composed of gaseous R1150 and gaseous R50, and between the gaseous R600a flowing out of the vapor-liquid separator and the refrigerant mixture composed of gaseous R1150 and gaseous R50, to obtain liquid R600a, liquid R1150 and gaseous R50; The gaseous R600a, gaseous R1150 and gaseous R50 obtained by exchanging heat from the refrigerant mixture composed of liquid R600a, gaseous R1150 and gaseous R50 return to the compressor through the return pipe under a suction force of 0.8-0.9 Kgf / cm^2 of the compressor.

[0015] Preferably, the inner diameter of the main capillary tube and / or the sub-capillary tube is 0.74-0.76 mm; and the heat exchanger comprises a plate-type heat exchanger.

[0016] Preferably, the temperature of the refrigerant mixture is controlled within the second threshold temperature range by a second refrigeration pipeline, and the second refrigeration pipeline comprises: The main capillary is connected to the output end of the heat exchanger, and is used to throttle and depressurize the refrigerant mixture composed of liquid R600a, liquid R1150 and gaseous R50 flowing out of the heat exchanger, and convert it into liquid R600a, liquid R1150 and liquid R50, and then flow into the evaporator, so as to control the inlet temperature of the evaporator to be within the second threshold temperature range. The evaporator is connected to the output end of the main capillary and the output end of the auxiliary capillary, and is used to heat the refrigerant mixture composed of liquid R600a, liquid R1150 and liquid R50 flowing in, control the temperature of the refrigerant mixture to be within the third threshold temperature range, and then flow into the auxiliary capillary and return to the compressor through the return pipe.

[0017] The application also provides a refrigerant mixture applied to the ultra-low temperature refrigeration system, wherein the refrigerant mixture comprises R600a, R1150 and R50, the mass ratio of R600a to R1150 is 1.78:1-1.85:1, and the mass ratio of R1150 to R50 is 22.8:1-23.5:1.

[0018] Preferably, the compressor discharges the refrigerant mixture composed of R600a, R1150 and R50 with mass ratios of 65±2%, 35±1% and 2±0.5% respectively into the ultra-low temperature refrigeration system at an exhaust pressure of 15-16 Kgf / cm^2.

[0019] The application has the following beneficial effects: 1. By configuring the refrigerant mixture composed of R600a, R1150 and R50 with a preset mass ratio, it is possible to achieve ultra-low temperature control of-80℃ in a small-sized refrigerator. The mass ratio relationship between R600a, R1150 and R50 takes into account the effects of the liquid addition sequence of R600a, R1150 and R50, the exhaust pressure and suction pressure of the compressor, the working voltage, current and power of the refrigeration system, the environmental temperature and other factors on the real-time monitoring temperature at positions such as the vapor-liquid separator, the condenser inlet, the condenser outlet, the exhaust pipe, the right side of the refrigerator liner, the top of the refrigerator liner, the left side of the refrigerator liner, the back of the refrigerator liner, the inside of the refrigerator, the heat exchanger inlet, the heat exchanger outlet, the evaporator inlet, the middle of the evaporator, the evaporator outlet, the return inlet and the return outlet. These influencing factors are directly related to the duration, energy consumption and temperature control accuracy of-80℃ ultra-low temperature control.

[0020] 2. The gaseous refrigerant mixture is first converted into a refrigerant mixture composed of liquid R600a, liquid R1150, and gaseous R50 through the first refrigeration pipeline, and the temperature of the refrigerant mixture can reach -45℃ after throttling and pressure reduction through the capillary tube with an inner diameter of 0.75 mm, so as to reduce the control time length and control difficulty of subsequent -85℃ ultra-low temperature control.

[0021] 3. The gaseous R50 is further converted into liquid through the second refrigeration pipeline and multiple compressor suction and exhaust circulation, and the refrigerant mixture with -45℃ can be quickly reduced to about -85℃ through further throttling and pressure reduction of the main capillary tube.

[0022] 4. The evaporator with improved structure reduces the consumption of cold energy by air gap, and ensures that the evaporator can accurately control the temperature of the refrigerant mixture at about -85℃ to about -82℃, so as to realize the requirements of -80℃ ultra-low temperature control and accurate temperature control in a small-sized refrigerator.

[0023] 5. The structure of the first refrigeration pipeline and the second refrigeration pipeline is improved, and the improved pipeline structure together promotes the conventional refrigerant with a preset mass ratio to achieve the requirement of -85℃ ultra-low temperature control in a small-sized refrigerator with space limitation, so as to reduce the difficulty of refrigerant mixture ratio, and realize the technical combination of pipeline structure improvement and refrigerant mixture ratio in the -80℃ ultra-low temperature control of a small-sized refrigerator. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0025] Figure 1 is a structural schematic diagram of the refrigeration system pipeline provided by the embodiments of the present application; Figure 2 is a schematic diagram of the adhesion of the copper tube in the conventional evaporator and the inner liner of the refrigerator; Figure 3 is a schematic diagram of the adhesion of the copper tube in the evaporator in the embodiments of the present application and the inner liner of the refrigerator. DETAILED DESCRIPTION

[0026] The technical solutions of the present application will be further described below by combining the drawings and through specific embodiments.

[0027] In the drawings, only for example, the representation is a schematic diagram, not a physical diagram, and cannot be understood as a limitation of the present application; in order to better illustrate the embodiments of the present application, some components in the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0028] In the drawings of the embodiments of the present application, the same or similar reference numerals correspond to the same or similar components; in the description of the present application, it should be understood that if the terms "upper", "lower", "left", "right", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the terms describing the positional relationship in the drawings are only for example and cannot be understood as a limitation of the present application, for those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0029] In the description of the present application, unless otherwise explicitly specified and limited, if the term "connection" and the like appear to indicate the connection relationship between components, the term should be broadly understood, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two components or the interaction relationship between two components. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0030] The present application develops a refrigeration evaporator adopting a press-fit process, the copper tube in the evaporator is flattened and bonded together with the aluminum plate of the refrigerator liner through the adhesive heat-conducting film, reducing the cold consumption, and by increasing the capillary tube with a preset inner diameter between the evaporator and the heat exchanger, and by controlling the suction and discharge pressure of the compressor, the evaporation temperature of the refrigerant mixture reaching the evaporator can reach about-85℃, thereby ensuring that the temperature in the box can be maintained at about-80℃.

[0031] In the present application, the refrigerant adopts environmentally friendly hydrocarbon refrigerants R600a, R1150, R50, three kinds of refrigerants are matched by a certain mass, which jointly play a role with the control of the suction and discharge pressure of the compressor, the structural improvement of the evaporator, the selection of the inner diameter of the capillary tube, etc., so that after heat exchange through the heat exchanger, liquid R600a and liquid R1150 can be obtained, which is the key to ensuring that the evaporation temperature can reach about-85℃ and the temperature in the box can be maintained at-80℃.

[0032] The following provides a detailed description of the cryogenic refrigeration system provided in this application, and how to prepare the refrigerant mixture for use in the cryogenic refrigeration system: The characteristic parameters of the three refrigerants R600a, R1150, and R50 are shown in Table 1 below: Table 1

[0033] As shown in Table 1 above, the R600a refrigerant used in ordinary freezers has a boiling point of -11.75℃ at one standard atmosphere. When it flows through the evaporator, the evaporation temperature is usually around -35℃, and the internal temperature of the freezer can usually only be maintained at around -33℃. Obviously, this cannot meet the ultra-low temperature control requirement of -80℃ inside the freezer.

[0034] The boiling point of R1150 ethylene at one standard atmosphere is -103.8℃, and the boiling point of R50 methane at one standard atmosphere is -161.5℃. Therefore, theoretically, mixing these three refrigerants in a certain ratio can achieve an evaporation temperature below -85℃ and an internal temperature below -80℃.

[0035] Achieving ultra-low temperature control of -80°C in a small refrigerator or freezer with limited space by preparing a refrigerant mixture in a specific ratio is very difficult and has no precedent. More importantly, it is crucial to ensure that the duration of the -80°C ultra-low temperature control is acceptable; that is, the control time from room temperature to -80°C inside the freezer cannot be too long. To solve this problem, this application modifies the piping of the refrigeration system while preparing the refrigerant mixture. These two modifications work synergistically to ensure that the temperature of the refrigerant mixture after heat exchange in the heat exchanger can be reduced to within a preset first threshold temperature range (around -45°C). This application will be as follows... Figure 1 The refrigeration system piping before heat exchanger 6 is defined as the first refrigeration piping (including compressor 1, anti-condensation pipe 2, condenser 3, cooling fan, dryer filter 4, vapor-liquid separator 5, heat exchanger 6, and auxiliary capillary tube 7). The refrigeration system piping after the heat exchanger is defined as the second refrigeration piping (including main capillary tube 8 and structurally improved evaporator 9). Since the refrigeration time of the first refrigeration piping is relatively controllable, when the temperature of a specially proportioned refrigerant mixture can be reduced to the ideal first threshold temperature range (around -45℃) after passing through the first refrigeration piping, the subsequent second refrigeration piping can significantly shorten the time required to further reduce the temperature of the refrigerant mixture, which is already within the first threshold temperature range, to the ultra-low temperature range of -85℃, and make it more controllable.

[0036] Therefore, the special refrigerant mixture is cooled to the first threshold temperature range by the first refrigeration pipeline and the heat exchanger, which is the first key to achieve the -80℃ ultra-low temperature control in the box. The second refrigeration pipeline is to further reduce the temperature of the refrigerant mixture in the first threshold temperature range to the second threshold temperature range (-85℃ or so), which is the second key. The special proportion of the refrigerant mixture is the third key, which is the most critical technical point. The three technical keys promote each other and work together to achieve the precise control of the -80℃ ultra-low temperature of the small-sized refrigerator or freezer under the premise of acceptable long-term control.

[0037] The following will explain in detail how the above three technical keys are implemented: For the first technical key, the temperature of the refrigerant mixture is reduced to the first threshold temperature range (-45℃ or so) after flowing through the first refrigeration pipeline. The technical key is that: Figure 1 A large amount of R600a (preferably 99.9% of the amount of R600a discharged by the compressor is converted to liquid), a large amount of R1150 (preferably 99.5% of the amount of R1150 discharged by the compressor is converted to liquid) in the gaseous R600a, R1150, R50 refrigerant mixture discharged by the compressor shown in the above-mentioned is converted from gaseous to liquid.

[0038] To achieve this purpose, the following technical means are adopted in the present application: In the present application, the first refrigeration pipeline includes Figure 1 The compressor 1, the anti-dew pipe 2, the condenser 3, the dry filter 4, the vapor-liquid separator 5, the auxiliary capillary tube 7 and the heat exchanger 6 shown in the above-mentioned.

[0039] First, the mass ratio of R600a and R1150 is controlled to be 1.8:1, and the mass ratio of R1150 and R50 is 23:1. More preferably, the mass ratio of R600a, R1150 and R50 is 63.59%, 34.91% and 1.50% respectively (the third technical key is the premise of realizing the first technical key).

[0040] It should be noted that the mass ratio relationship between R600a, R1150 and R50 takes into account the effects of the order of adding R600a, R1150 and R50, the discharge pressure and suction pressure of the compressor, the working voltage, current, power of the refrigeration system, the environmental temperature and other factors on the real-time monitoring temperature at the positions of the vapor-liquid separator, the condenser inlet, the condenser outlet, the exhaust pipe, the right side of the inner liner of the refrigerator, the top of the inner liner of the refrigerator, the left side of the inner liner of the refrigerator, the back of the inner liner of the refrigerator, the inside of the box, the heat exchanger inlet, the heat exchanger outlet, the evaporator inlet, the middle of the evaporator, the evaporator outlet, the return gas inlet, the return gas outlet and other positions. The above-mentioned effects are obtained through repeated experiments and verification. These factors are directly related to the duration of the -80℃ ultra-low temperature control, the energy consumption and the temperature control accuracy.

[0041] The experimental process for determining the mass ratio of R600a, R1150 and R50 is shown in Tables 2, 3, 4 and 5 as follows: Table 2

[0042] Table 3

[0043] Table 4

[0044] Table 5

[0045] Then, the control Figure 1The compressor 1 shown in the middle discharges the gaseous refrigerant mixture of R600a, R1150 and R50 with mass ratios of 63.59%, 34.91% and 1.50% respectively at an exhaust pressure of 15-16 Kgf / cm^2, more preferably at an exhaust pressure of 15.62 Kgf / cm^2 into the anti-dew pipe 2 (the function of the anti-dew pipe is to prevent the door of the refrigerator from icing up around the door, causing the ice block to stick to the door seal, resulting in the door being unable to be opened when the refrigerator is powered on for a long time) and the condenser 3 (preferably a finned condenser) to release heat, and then passes through the dry filter 4 for filtration. At this time, most of the liquid R600a and a small amount of gaseous R600a are separated in the vapor-liquid separator 5. The liquid R600a is at the lower part of the vapor-liquid separator, and the small amount of gaseous R600a and the gaseous R1150 and R50 are at the upper part of the vapor-liquid separator 5. By controlling the exhaust pressure of the compressor 1 and the mass ratios of R600a, R1150 and R50 to be 63.59%, 34.91% and 1.50% respectively, and passing through the anti-dew pipe, the condenser, the dry filter and the vapor-liquid separator in the first refrigeration pipe, most of the liquid R600a (the mass ratio of the liquid R600a separated in the vapor-liquid separator is preferably 95% of the gaseous R600a discharged by the compressor) is obtained, which is the key to achieving the ideal-45℃ or so in the subsequent heat exchanger, and is also the key to further reducing the temperature to-85℃ through the second refrigeration pipe.

[0046] The backflow effect of the refrigerant mixture is also the key to ensuring that the heat exchanger reaches-45℃ and shortening the overall ultra-low temperature control time. To improve the backflow effect of the refrigerant mixture, the present application adopts the following technical means: After vapor-liquid separation by the vapor-liquid separator, most of the liquid R600a at the lower part of the vapor-liquid separator enters the Figure 1After throttling and pressure reduction of the sub-capillary tube 7, the gas R600a is circulated to the heat exchanger 6 to absorb heat and is converted into low-temperature and low-pressure (temperature in the range of -5℃ to 0℃, pressure in the range of 0.8-0.9 Kgf / cm^2) gas, and a small amount of gas R1150 and R50 is returned to the compressor through the return pipe under the suction of the compressor (preferably 0.8-0.9 Kgf / cm^2). At the same time, a small amount of gas R600a and most of the gas R1150 and R50 in the upper part of the vapor-liquid separator enter the heat exchanger 6 to release heat and obtain liquid R600a, liquid R1150 and gas R50. Since the heat exchanger 6 exchanges heat with most of the liquid R600a and a small amount of gas R1150 and R50, the temperature of the heat exchanger is greatly reduced, and at this time, the heat release effect of the small amount of gas R600a and most of the gas R1150 and R50 directly circulated from the vapor-liquid separator to the heat exchanger is greatly improved. Through the suction and exhaust operation of the compressor cycle, the temperature of the heat exchanger continues to decrease, and the temperature of the refrigerant mixture is greatly reduced, and finally can reach about -45℃.

[0047] It is emphasized here that controlling the refrigerant mixture to reach about -45℃ in the heat exchanger is a dynamic and comprehensive control process, and cannot be determined by a single factor. First, for R600a, R1150 and R50 with a mass ratio of 63.59%, 34.91% and 1.50%, the discharge pressure range of the compressor is set to 15-16 Kgf / cm^2, and the suction pressure range is 0.8-0.9 Kgf / cm^2. Moreover, the inner diameter of the sub-capillary tube is 0.75 mm, and the liquid R600a in the lower part of the vapor-liquid separator is throttled and pressure reduced, and the liquid and gas R600a and R1150, R50 are simultaneously exchanged in the heat exchanger, and after multiple suction and exhaust cycles, the ideal -45℃ can be achieved.

[0048] For the second technical key, to control the temperature of the refrigerant mixture in the second threshold temperature range (-85℃ or so), the technical key is to convert R50 in the refrigerant mixture composed of liquid R600a, liquid R1150 and gas R50 with a temperature of about -45℃ obtained through the first refrigeration pipeline into liquid state, so as to ensure that the evaporator surface temperature can reach about -85℃. To achieve this purpose, the following technical means are adopted in the present application: 1、Select heat exchanger with better heat exchange effect to ensure that the temperature of the refrigerant mixture composed of liquid R600a, liquid R1150 and gaseous R50 obtained after heat exchange in the heat exchanger can reach about -45℃. The present application preferably adopts a plate type heat exchanger, such as a plate type heat exchanger of B3-12-10 model from Guoxin Heat Exchanger Co., Ltd. The plate type heat exchanger has the advantages of large heat exchange area, high efficiency, reliability and high consistency. At present, the heat exchange disc structure formed by two copper pipes parallelly brazed and then coiled into a mosquito coil form is mostly used in small size refrigerators. The heat exchanger of this heat exchange disc structure form has large discreteness of actual heat exchange effect and poor consistency of heat exchange of products, which cannot meet the ultra-low temperature refrigeration control requirements of the present application.

[0049] 2、The selection and mass ratio of the refrigerant mixture are critical. In the present application, R600a, R1150 and R50 are selected and mixed as the refrigerant mixture with a mass ratio of 63.59%, 34.91% and 1.50%.

[0050] 3、Controlling the flow rate and pressure of the liquid R600a, liquid R1150 and gaseous R50 obtained from the first refrigeration pipeline into the evaporator is critical. The present application selects a main capillary tube with an inner diameter of 0.75 mm to convert the liquid R600a, liquid R1150 and gaseous R50 flowing out of the heat exchanger into a refrigerant mixture composed of liquid R600a, liquid R1150 and liquid R50. After throttling and pressure reduction by the main capillary tube 8, the temperature of the refrigerant mixture at the inlet end of the evaporator can reach about -85℃ (within the second threshold temperature range).

[0051] It should be noted that the temperature at the inlet end of the evaporator reaching -85℃ is achieved through the closed-loop ultra-low temperature control after multiple cycles, i.e.: Figure 1 the exhaust and suction processes of the compressor shown in FIG. 8 under the set exhaust pressure and suction pressure, and is the result of the multiple collaborative refrigeration control of the first refrigeration pipeline and the second refrigeration pipeline on R600a, R1150 and R50 with a mass ratio of 63.59%, 34.91% and 1.50%.

[0052] 4、The evaporator with improved structure absorbs heat from the refrigerant mixture composed of liquid R600a, liquid R1150 and liquid R50 flowing out of the main capillary tube, and maintains the temperature in the box at about -82℃. The method of controlling the heat exchange temperature of the evaporator at about 3℃ in combination with Figure 2 and Figure 3 is explained as follows: As Figure 2As shown in the figure, in a conventional evaporator, the copper tube 10 and the refrigerator liner 20 are bonded to each other by an aluminum foil tape 30. Due to the circular structure of the copper tube, the air wrapped in the bonding gap 40 will consume part of the cold energy, which is not conducive to the precise control of the 3℃ heat exchange temperature. In this application, as shown in the figure, the copper tube 10 is flattened and directly bonded to the refrigerator liner 20 by bonding the heat-conducting film 50, which will not produce a bonding gap and will not consume additional cold energy due to the bonding gap, so as to precisely control the heat exchange temperature at about 3℃, which is conducive to maintaining the temperature in the box at about -82℃ (within the third threshold temperature range) when the temperature of the refrigerant mixture reaches about -85℃. Figure 3

[0053] It should be noted here that the above structural improvement of the evaporator is the key to precisely control the temperature in the box to be maintained at about -82℃, and to control the temperature in the box to be -82℃, it is crucial to reduce the temperature of the refrigerant mixture to about -85℃. Therefore, the above structural improvement of the evaporator is not an isolated technical point, but a related technical point that interacts with the proportion of each type of refrigerant in the mixture, the structure of the first refrigeration pipeline, the second refrigeration pipeline, the return pipeline, the suction and discharge pressure of the compressor, the inner diameter of the capillary tube, etc. These technical points together reduce the temperature of the refrigerant mixture to -85℃, and then rely on the improved evaporator to maintain the temperature in the box at about -82℃.

[0054] In summary, the present application configures a refrigerant mixture composed of R600a, R1150 and R50 with a predetermined mass ratio, controls the suction and discharge pressure of the compressor, improves the structure of the evaporator, controls the inner diameter of the capillary tube, and through the first refrigeration pipeline, first converts the gaseous refrigerant mixture into a refrigerant mixture composed of liquid R600a, liquid R1150 and gaseous R50, which can reach a temperature of -45℃ after being throttled and reduced in pressure by a capillary tube with an inner diameter of 0.75cm, to reduce the control time of subsequent -85℃ ultra-low temperature control. Through the second refrigeration pipeline and multiple compressor suction and discharge cycles, gaseous R50 is further converted into liquid, so that the refrigerant mixture already having a temperature of -45℃ can be quickly reduced to about -85℃. Through the improved structure of the evaporator, the consumption of cold energy by the gap air is reduced, and the evaporator can precisely control the temperature of the refrigerant mixture at about -85℃ to about -82℃, thereby achieving the demand for ultra-low temperature control at -80℃ in a small-sized refrigerator.

[0055] ​It should be noted that the above-mentioned detailed description is only the preferred embodiment of the present application and the technical principle applied. Those skilled in the art should understand that various modifications, equivalent replacements, changes and the like can be made to the present application. However, as long as these changes do not deviate from the spirit of the present application, they should be within the protection scope of the present application. In addition, some terms used in the present application specification and claims are not limited, but only for the convenience of description.

Claims

1. An ultra-low temperature refrigeration system, characterized in that, include: A compressor is used to control the suction and / or discharge pressure of the refrigerant mixture flowing in the pipeline within a preset pressure range; A heat exchanger is used to exchange heat with the refrigerant mixture flowing under the preset pressure range to obtain liquid R600a and liquid R1150, so as to reduce the temperature of the refrigerant mixture after heat exchange to a preset first threshold temperature range. The main capillary tube, with a preset inner diameter, is used to throttle and reduce the pressure of the refrigerant mixture flowing out of the heat exchanger, so as to lower the temperature of the refrigerant mixture to a preset second threshold temperature range before delivering it to the evaporator. An evaporator, in which copper tubes are flattened and glued to the inner liner of a refrigerator, is used to absorb heat from the refrigerant mixture within the second threshold temperature range and maintain the temperature inside the refrigerator within a preset third threshold temperature range.

2. The cryogenic refrigeration system according to claim 1, characterized in that, The refrigerant mixture includes R600a, R1150 and R50, with the mass ratio of R600a to R1150 being 1.78:1 to 1.85:1, and the mass ratio of R1150 to R50 being 22.8:1 to 23.5:

1.

3. The cryogenic refrigeration system according to claim 1, characterized in that, The mass percentages of R600a, R1150, and R50 are 65±2%, 35±1%, and 2±0.5%, respectively.

4. The cryogenic refrigeration system according to any one of claims 1-3, characterized in that, The compressor has an intake pressure range of 0.8-0.9 kgf / cm² and an exhaust pressure range of 15-16 kgf / cm².

5. The cryogenic refrigeration system according to any one of claims 1-3, characterized in that, The temperature of the refrigerant mixture is controlled within the first threshold temperature range through a first refrigeration pipeline, wherein the first refrigeration pipeline includes: The compressor is used to discharge the refrigerant mixture consisting of R600a, R1150, and R50 in a set mass ratio into the anti-condensation pipe at a discharge pressure within a set discharge pressure range. The condenser, connected to the compressor via piping, is used to release heat from the refrigerant mixture flowing out of the anti-condensation pipe and then deliver it to the dryer filter; The dryer filter, connected in a pipeline to the condenser, is used to dry and filter the incoming refrigerant mixture; A vapor-liquid separator, connected by a pipeline to the dryer filter, is used to separate the incoming refrigerant mixture into vapor and liquid components to obtain liquid R600a, which has a mass percentage of 90%-95% of the gaseous R600a discharged from the compressor.

6. The cryogenic refrigeration system according to claim 5, characterized in that, The first refrigeration pipeline also includes: A secondary capillary tube is used to throttle and depressurize the liquid R600a flowing in from the vapor-liquid separator before it flows to the heat exchanger. A heat exchanger, with piping connecting the secondary capillary tube and the compressor, is used to exchange heat with the refrigerant mixture consisting of liquid R600a, gaseous R1150, and gaseous R50 flowing out from the secondary capillary tube, and simultaneously exchange heat with the refrigerant mixture consisting of gaseous R600a, gaseous R1150, and gaseous R50 flowing out from the vapor-liquid separator, to obtain liquid R600a, liquid R1150, and gaseous R50. The refrigerant mixture consisting of liquid R600a, gaseous R1150, and gaseous R50, after heat exchange, returns to the compressor via the return pipe under the suction force of 0.8-0.9 kgf / cm^2.

7. The cryogenic refrigeration system according to claim 6, characterized in that, The inner diameter of the main capillary tube and / or the secondary capillary tube is 0.74 mm to 0.76 mm; the heat exchanger includes a plate heat exchanger.

8. The cryogenic refrigeration system according to claim 6, characterized in that, The temperature of the refrigerant mixture is controlled within the second threshold temperature range via a second refrigeration pipeline, the second refrigeration pipeline comprising: The main capillary tube, connected to the output end of the heat exchanger, is used to throttle and depressurize the refrigerant mixture consisting of liquid R600a, liquid R1150 and gaseous R50 flowing out of the heat exchanger, converting it into liquid R600a, liquid R1150 and liquid R50 before it flows to the evaporator, so as to control the inlet temperature of the evaporator within the second threshold temperature range; The evaporator, with pipes connecting the output end of the main capillary tube and the output end of the auxiliary capillary tube, is used to absorb heat from the refrigerant mixture consisting of liquid R600a, liquid R1150 and liquid R50 flowing in, control the temperature of the refrigerant mixture within the third threshold temperature range, and then merge with the refrigerant mixture flowing out of the auxiliary capillary tube and return to the compressor through the return pipe.

9. A refrigerant mixture, used in the cryogenic refrigeration system as described in claims 1-8, characterized in that, The refrigerant mixture includes R600a, R1150 and R50, with the mass ratio of R600a to R1150 being 1.78:1 to 1.85:1, and the mass ratio of R1150 to R50 being 22.8:1 to 23.5:

1.

10. The refrigerant mixture according to claim 9, characterized in that, The compressor discharges the refrigerant mixture consisting of R600a, R1150, and R50, with mass percentages of 65±2%, 35±1%, and 2±0.5%, respectively, into the cryogenic refrigeration system at a discharge pressure of 15-16 Kgf / cm^2.

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