CN110914608A - Refrigeration device and method for operating refrigeration device - Google Patents
Refrigeration device and method for operating refrigeration device Download PDFInfo
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- CN110914608A CN110914608A CN201780093104.3A CN201780093104A CN110914608A CN 110914608 A CN110914608 A CN 110914608A CN 201780093104 A CN201780093104 A CN 201780093104A CN 110914608 A CN110914608 A CN 110914608A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B1/00—Compression machines, plants or systems with non-reversible cycle
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B39/00—Evaporators; Condensers
- F25B39/02—Evaporators
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Abstract
The purpose of the present invention is to prevent uneven frost formation in a refrigeration apparatus using a non-azeotropic refrigerant mixture having a temperature gradient, thereby preventing a COP of the refrigeration apparatus and a decrease in the refrigeration capacity of the refrigeration apparatus. The refrigeration cycle is characterized by comprising a refrigeration cycle in which a compressor, a condenser, a pressure reducing device, and an evaporator are connected by refrigerant pipes, wherein a refrigerant circulates inside the refrigeration cycle, the refrigerant is a non-azeotropic mixed refrigerant in which a plurality of types are mixed, and the evaporator reduces the pressure in a pipeline during evaporation in the direction in which the refrigerant flows, in accordance with the temperature gradient of the non-azeotropic mixed refrigerant.
Description
Technical Field
The present invention relates to a refrigeration apparatus, and more particularly to a refrigeration apparatus using a non-azeotropic refrigerant mixture and a method for operating the refrigeration apparatus.
Background
Conventionally, there is known a refrigeration apparatus having a refrigeration cycle in which an evaporator, a compressor, a condenser, and a pressure reducing device are connected to each other via a pipe through which a refrigerant circulates.
In a refrigeration apparatus such as an air conditioner or a refrigerator, a structure is known in which a heat exchanger functioning as an evaporator is opposed to a heat exchanger in which a refrigerant flows in a direction in which heat-exchanged air flows and a direction in which the refrigerant flows are opposite to each other, and the heat-exchanged air and the refrigerant are convected to reduce a heat exchange loss and improve performance (for example, see patent document 1).
On the other hand, as a refrigerant used in a refrigeration apparatus, there is a case where a non-azeotropic refrigerant mixture is obtained by mixing a plurality of refrigerants (for example, see patent document 2). Convection can be achieved even in an evaporator of a refrigeration apparatus using a non-azeotropic refrigerant mixture. In particular, in the case of a non-azeotropic refrigerant mixture, the temperature of the refrigerant changes due to phase change at the same pressure. That is, since the zeotropic refrigerant mixture has a temperature gradient during the evaporation, for example, in the case of an evaporator, the temperature on the upstream side becomes lower than the temperature on the downstream side during the evaporation. Therefore, the temperature difference between the refrigerant and the heat source medium such as air or water can be further reduced, and the coefficient of performance (COP) can be improved.
Patent document 1: japanese laid-open patent publication (JP 2015-141009)
Patent document 2: japanese laid-open patent publication No. 7-208822
However, in low temperature equipment where the saturation temperature is below freezing, the evaporator produces frost. When a non-azeotropic refrigerant mixture is used in the evaporation process of a low-temperature device in which frost is formed, the frost formation of the evaporator becomes uneven. That is, the cooling of air is promoted on the inlet side of the evaporator where the temperature of the non-azeotropic refrigerant mixture having a temperature gradient such as a change in the refrigerant temperature due to the phase change at the same pressure as described above is low, and the frost formation amount increases, whereas the cooling of air does not progress on the outlet side of the evaporator where the temperature of the refrigerant is high and the frost formation amount decreases. In this way, when the evaporator has uneven frost formation, the space between the fins on the inlet side of the evaporator is clogged with frost at an early stage, even if the entire frost formation amount is the same, compared to the case of even frost formation, and the heat exchange rate is lowered. Therefore, there is a problem that the influence of the deterioration of the heat exchange rate due to the uneven frost formation becomes larger than the improvement of the heat exchange rate due to the convection between the refrigerant and the heat source medium, the evaporation pressure in the evaporator is lowered, and the COP of the refrigeration apparatus and the refrigeration capacity of the refrigeration apparatus are lowered.
Disclosure of Invention
An object of the present invention is to provide a refrigeration apparatus using a non-azeotropic refrigerant mixture having a temperature gradient, in which uneven frost formation is prevented, thereby preventing a decrease in COP of the refrigeration apparatus and a decrease in refrigeration capacity of the refrigeration apparatus, and a method for operating the refrigeration apparatus.
The refrigeration apparatus according to the present invention is characterized by comprising a refrigeration cycle in which a compressor, a condenser, a pressure reducing device, and an evaporator are connected by refrigerant pipes, and in which a refrigerant circulates, wherein the refrigerant is a non-azeotropic mixed refrigerant in which a plurality of types are mixed, and wherein the evaporator decreases a pressure in a pipe during evaporation in a direction in which the refrigerant flows in accordance with a temperature gradient of the non-azeotropic mixed refrigerant.
According to the present invention, with the above configuration, it is possible to obtain a refrigeration apparatus using a non-azeotropic refrigerant mixture having a temperature gradient, in which the refrigerant temperature in the evaporator is substantially equalized, thereby suppressing unevenness in frost formation in the evaporator and suppressing a decrease in COP and refrigeration capacity of the refrigeration apparatus.
Drawings
Fig. 1 is a schematic diagram showing the overall configuration of a refrigeration apparatus according to embodiment 1 of the present invention.
Fig. 2 is a schematic diagram showing the configuration of an evaporator of a refrigeration apparatus according to embodiment 1 of the present invention.
Fig. 3 shows a mollier diagram of a zeotropic refrigerant mixture used in the refrigeration apparatus according to embodiment 1 of the present invention.
Fig. 4 is a control flowchart of the refrigeration apparatus according to embodiment 1 of the present invention.
Fig. 5 shows a mollier diagram of a zeotropic refrigerant mixture used in a refrigeration apparatus according to embodiment 2 of the present invention.
Fig. 6 is a schematic diagram showing the configuration of an evaporator of a refrigeration apparatus according to embodiment 2 of the present invention.
Detailed Description
Embodiment mode 1
Fig. 1 is a schematic diagram showing the overall configuration of a refrigeration apparatus 100 according to embodiment 1 of the present invention. In the drawings, the same or corresponding portions are denoted by the same reference numerals. As shown in fig. 1, the refrigeration apparatus 100 according to embodiment 1 is formed by connecting a compressor 1, a condenser 2, a pressure reducing device 3, and an evaporator 4 in this order via a refrigerant pipe 5. The refrigeration apparatus 100 is configured as a refrigeration cycle in which a refrigerant circulates in the order of the compressor 1, the condenser 2, the pressure reducing device 3, the evaporator 4, and the compressor 1. The control unit 60 controls each device constituting the refrigeration apparatus 100.
(compressor 1)
The compressor 1 sucks a refrigerant, compresses the refrigerant into a high-temperature and high-pressure gas state, and discharges the gas state. The compressor 1 may be configured by, for example, an inverter circuit or the like that can control the rotation speed and adjust the discharge amount of the refrigerant by controlling the rotation speed.
(condenser 2)
The condenser 2 is supplied with a refrigerant compressed to a high-temperature and high-pressure gas state in the compressor 1, and performs heat exchange between the refrigerant and a heat source to cool the refrigerant to a low-temperature and high-pressure liquid state. The heat source may be air, water, brine, or the like, and in embodiment 1, the heat source of the condenser 2 is outdoor air, that is, outside air. The condenser 2 performs heat exchange between outside air and refrigerant. In embodiment 1, a condenser blower 6 is provided, and the condenser blower 6 blows outside air to the condenser 2 when the refrigerant circulates in the refrigeration apparatus 100 in order to promote heat exchange in the condenser 2. The condenser fan 6 may be constituted by a device capable of adjusting the air volume.
(pressure reducing device 3)
The decompression device 3 receives the low-temperature high-pressure liquid refrigerant cooled by the condenser 2, and decompresses and expands the refrigerant to a low-temperature low-pressure liquid state. The decompression device 3 is configured by, for example, a refrigerant flow rate control unit such as an electronic expansion valve or a thermal expansion valve, or a capillary tube (capillary tube).
(evaporator 4)
The evaporator 4 is configured to allow the refrigerant in a low-temperature low-pressure liquid state decompressed and expanded by the decompression device 3 to flow therein, exchange heat between the refrigerant and the object to be cooled, absorb heat of the object to be cooled by the refrigerant, and cool the object to be cooled. When cooling the object to be cooled, the refrigerant evaporates to become a high-temperature low-pressure gas state. In embodiment 1, the cooling target is indoor air. That is, the evaporator 4 exchanges heat between indoor air and the refrigerant. Further, embodiment 1 includes an evaporator blower 7, and the evaporator blower 7 blows indoor air to the evaporator 4 when the refrigerant circulates in the refrigeration apparatus 100, in order to promote heat exchange between the indoor air and the refrigerant in the evaporator 4. The evaporator blower 7 may be constituted by a device capable of adjusting the air volume.
A specific structure of the evaporator 4 will be described with reference to fig. 2. The evaporator 4 is a plate-fin tube heat exchanger including a plurality of heat transfer tubes 41, a plurality of fins 42, a refrigerant distributor 43, and a header 44. In fig. 2, the number of heat transfer tubes 41 is 5, and the number of fins 42 is 28, but these numbers and numbers are merely examples, and the present invention is not limited to these numbers and numbers.
Fig. 2 is a schematic diagram showing the configuration of evaporator 4 of refrigeration apparatus 100 according to embodiment 1 of the present invention. Fig. 2 schematically shows the evaporator 4. Here, the flow of the refrigerant in the evaporator 4 will be described with reference to fig. 2. First, the low-temperature low-pressure refrigerant in a liquid state decompressed and expanded in the decompression device 3 flows in from the inlet of the refrigerant distributor 43. The refrigerant flowing from the inlet of the refrigerant distributor 43 is distributed into a plurality of refrigerant distribution holes at the outlet of the refrigerant distributor 43, and flows from each outlet of the refrigerant distributor 43 to the heat conducting pipe 41. The refrigerant flowing into the heat transfer pipe 41 flows in the axial direction of the heat transfer pipe 41. The surfaces of heat transfer pipe 41 and fins 42 contact the indoor air to be cooled blown by blower 7 provided in evaporator 4. The indoor air blown toward the fins 42 of the evaporator 4 flows in a direction opposite to the flow direction of the refrigerant flowing inside the evaporator 4. The refrigerant flowing through the inside of heat transfer pipe 41 exchanges heat with indoor air in contact with heat transfer pipe 41 and fins 42, and absorbs heat of the indoor air. The refrigerant that has exchanged heat with indoor air at the heat transfer tubes 41 flows in from the inlet of the header 44, is collected by the header 44, and flows into the compressor 1 from the outlet of the header 44.
Fig. 3 shows a mollier diagram of a zeotropic refrigerant mixture used in refrigeration apparatus 100 according to embodiment 1 of the present invention. The zeotropic refrigerant mixture is a refrigerant obtained by mixing two or more refrigerants having different boiling points, and the pressure saturation temperature of the refrigerant changes depending on the dryness even at a constant pressure in a gas-liquid two-phase state. That is, when the refrigerant in the evaporator 4 is evaporated along a line indicated by a broken line a in fig. 3 where the pressure is constant, the temperature at the inlet of the evaporator 4 decreases, and the temperature at the outlet increases. Therefore, as shown by a broken line B in fig. 3, the temperature of the zeotropic refrigerant mixture flowing through the evaporator 4 can be equalized by continuously reducing the pressure inside the evaporator 4 at a certain predetermined gradient. Furthermore, by maintaining the inlet temperature and the outlet temperature of the evaporator 4 at equal levels, the occurrence of uneven frost formation in the evaporator 4 can be suppressed.
If the pressure inside the evaporator 4 is gradually reduced, a pressure difference is generated between the inlet and the outlet of the evaporator 4. The relationship between the pressure and the saturation temperature of the refrigerant flowing through the evaporator 4 is uniquely determined according to the composition of the refrigerant. Therefore, the pressure difference between the inlet and the outlet of the evaporator 4 when the temperatures are equalized at the inlet and the outlet of the evaporator 4 is uniquely determined according to the composition of the refrigerant. Therefore, in the actual refrigeration apparatus 100, the pressure difference between the inlet and the outlet of the evaporator 4 is set to be the same as the pressure difference between the refrigerant at the inlet and the outlet of the evaporator 4 when the temperature of the refrigerant flowing through the evaporator 4 is equalized, and thus the unevenness of frost formation in the evaporator 4 can be suppressed.
As means for continuously reducing the pressure of the refrigerant inside the evaporator 4 at a certain predetermined gradient, there is means for changing the inner diameter of the heat transfer pipe 41 through which the refrigerant passes in stages. Although the heat transfer tubes 41 constituting the evaporator 4 are generally tubes having a uniform inner diameter, for example, the pressure of the refrigerant flowing inside can be reduced by gradually reducing the cross-sectional area of the heat transfer tubes 41 from the inlet to the outlet of the evaporator 4. Alternatively, for example, the cross-sectional area of the heat transfer pipe 41 may be gradually reduced from the inlet to the outlet of the evaporator 4.
Alternatively, resistance may be provided in the pipe passage of the heat transfer pipe 41, and the pressure of the refrigerant flowing inside may be reduced by the pipe passage resistance. For example, the pressure loss of the refrigerant flowing through the inside of the heat transfer tubes 41 can be increased by providing the inner wall surfaces of the heat transfer tubes 41 with irregularities to increase the tube resistance.
Further, the heat transfer pipe 41 may be lengthened to increase the pressure loss due to the pipe resistance, thereby increasing the pressure difference between the inlet and the outlet of the evaporator 4. The above means may be appropriately selected according to the temperature gradient of the zeotropic refrigerant mixture to be used.
Further, by providing a flow rate adjustment valve at the inlet of the evaporator 4, controlling the operating speed of the compressor 1, or the like, and controlling the flow rate of the refrigerant passing through the evaporator 4, the pressure inside the evaporator 4 can be continuously reduced at a certain predetermined gradient, regardless of the operating state or the type of the zeotropic refrigerant mixture used.
Thus, when a refrigerant having a temperature gradient during evaporation is used, the refrigerant temperature in the evaporator 4 can be made substantially uniform by configuring the piping pressure loss in the evaporator 4 to be substantially the same as the temperature gradient of the refrigerant. This can prevent performance degradation of the refrigeration apparatus 100 due to the frost formation on the inlet side of the evaporator 4 into which the refrigerant flows.
(control of the refrigerating apparatus 100)
Fig. 4 is a control flowchart of the refrigeration apparatus 100 according to embodiment 1 of the present invention. The refrigeration apparatus 100 is used for a plurality of purposes such as a cooling unit and a showcase. The dotted line shown in fig. 1 indicates a cooler 50, and the cooler 50 corresponds to a cooling unit or a showcase. The portion other than the dotted line portion shown in fig. 1 is a so-called heat source device. In particular, when the control unit 60 cannot directly control the cooler 50, the control unit 60 obtains the pressure, temperature, and operating conditions of each unit of the heat source unit, and controls the operation of the refrigeration apparatus 100.
(step i)
In step i, a refrigerant circulation amount Gr circulating through the refrigeration apparatus 100 is calculated. First, the suction pressure Ps of the compressor 1 is detected by the pressure sensor 20 provided in the suction-side pipe of the compressor 1. The suction temperature Th of the compressor 1 is detected by a temperature sensor 30 provided in the suction-side pipe of the compressor 1. Further, the refrigerant circulation amount Gr is calculated by the following equation.
Gr＝F×Vst×ηv×ρs×3600×10-6
Here, F [ Hz ]]Is the operating frequency of the compressor 1, Vst [ cc ]]Is the discharge capacity of the compressor 1, η v is the volumetric efficiency of the compressor 1, ρ s [ kg/m ]3]The values Vst and η v are values specific to the compressor 1, and may be stored in the control unit 60 in advance, ρ s can be obtained for each refrigerant type, and obtained from the suction pressure ρ s and the suction temperature Th, and step i is referred to as a refrigerant circulation amount calculation step.
(step ii)
In step ii, the pressure loss Δ P between the inlet and outlet of the evaporator 4 is calculated from the refrigerant circulation amount Gr determined in step i. Δ P is calculated by the following formula.
ΔP＝α×f×(l/d)×(ρu2/2g)
Here, [ m ]]Is the length of the piping, d [ m ]]Is the pipe diameter, rho [ kg/m ]3]Is the liquid density, u [ m/s ]]It is the refrigerant flow velocity, f is the friction loss coefficient, α is the correction coefficient, α, f, l, d and g are fixed values, it is understood from the formula that the pressure loss Δ P becomes large as the refrigerant flow velocity u and the refrigerant density ρ become large, the refrigerant flow velocity u can be obtained from the refrigerant circulation amount Gr, the pressure loss Δ P may be obtained by storing in advance the value of Δ P obtained from the relationship between the refrigerant density ρ and the refrigerant circulation amount Gr in the control unit 60, the relationship between the pressure loss Δ P, the refrigerant density ρ and the refrigerant circulation amount Gr may be stored in advance in the control device as a lookup table, and step ii is referred to as the pressure loss detection step of the evaporator 4.
(step iii)
The inlet pressure Pein of the evaporator 4 is calculated. The inlet pressure Pein is calculated by Pein ═ Ps + Δ P. The steps i to iii are collectively referred to as a detection step for detecting the pressure in the pipeline at the inlet of the evaporator and at the outlet of the evaporator.
(step iv)
The saturation temperature Tein at the inlet of the evaporator 4 is converted according to Pein. The saturation temperature Teout at the outlet of the evaporator 4 is also converted based on the suction pressure Ps. The conversion can be obtained from a specific saturation pressure conversion table for each refrigerant type. Step iv is referred to as a temperature gradient detection step of determining a temperature gradient between the inlet of the evaporator 4 and the outlet of the evaporator 4.
(step v)
The refrigerant circulation amount Gr is changed by controlling the compressor operating frequency F so that the difference Δ Te between the saturation temperature at the evaporator inlet and the saturation temperature at the evaporator outlet becomes 0. For example, when Δ Te is greater than 0, the compressor operating frequency F is increased, and when Δ Te is less than or equal to 0, the compressor operating frequency F is decreased. Since Δ Te is close to 0, the pressure loss becomes parallel to the temperature gradient. The step v is referred to as a flow rate changing step of changing the flow rate u of the refrigerant flowing through the refrigeration cycle by changing the operating frequency F of the compressor 1. In addition, step iv and step v are collectively referred to as a pressure adjusting step. In step v, instead of changing the operating frequency F of the compressor 1, the opening degree of a flow rate regulating valve provided on the inlet side of the evaporator 4 may be changed to change the flow velocity u of the refrigerant flowing through the refrigeration cycle. The flow rate adjustment valve may be the pressure reducing device 3. This control is performed when the control unit 60 can control the cooler 50.
(1) The refrigeration apparatus 100 according to embodiment 1 includes a refrigeration cycle in which a refrigerant circulates inside by connecting the compressor 1, the condenser 2, the pressure reducing device 3, and the evaporator 4 via a refrigerant pipe 5. The evaporator 4 is characterized in that the refrigerant is a non-azeotropic refrigerant mixture in which a plurality of types are mixed, and the pressure in the pipe line during evaporation is reduced in the direction in which the refrigerant flows, in accordance with the temperature gradient of the isotherm of the gas-liquid two-phase region of the non-azeotropic refrigerant mixture.
With this configuration, the refrigeration apparatus 100 can suppress a temperature difference between the inlet side and the outlet side of the refrigerant in the evaporator 4. Therefore, the amount of frost formation becomes even at the inlet side and the outlet side of the evaporator 4, and therefore, it is possible to prevent the heat exchange performance of the evaporator 4 from being lowered due to uneven frost formation.
(2) According to refrigeration apparatus 100 of embodiment 1, the cross-sectional area of heat transfer pipe 41 of evaporator 4 decreases in the direction in which the refrigerant flows.
(3) According to the refrigeration apparatus 100 of embodiment 1, the heat transfer tube 41 of the evaporator 4 includes the resistance means that serves as resistance to the flow of the refrigerant in the tube.
(4) According to the refrigeration apparatus 100 of embodiment 1, the flow rate of the refrigerant passing through the evaporator 4 is controlled to reduce the pressure in the pipe during the evaporation.
With this configuration, the refrigeration apparatus 100 can suppress a temperature difference between the inlet and the outlet of the evaporator 4 by causing the non-azeotropic refrigerant mixture to flow through the evaporator 4 at a predetermined flow rate. In addition, by appropriately combining the above-described means (2) to (4) and by appropriately controlling the pressure loss given to the refrigerant flowing in the evaporator 4 according to the refrigerant used in the refrigeration apparatus 100, it is possible to appropriately control the pressure loss.
(5) According to the operation method of the refrigeration apparatus 100 according to embodiment 1, the refrigerant is a non-azeotropic refrigerant mixture in which a plurality of types are mixed, and the operation method of the refrigeration apparatus 100 includes: a detection step of detecting, in the refrigeration apparatus, the in-line pressures at the inlet portion of the evaporator 4 and the outlet portion of the evaporator 4; and a pressure adjusting step of making a difference between the in-line pressures in the inlet portion and the outlet portion coincide with a temperature gradient of the refrigerant.
By operating in this manner, the refrigeration apparatus 100 can obtain the effect described in (1) above.
(6) The method of operating the refrigeration apparatus 100 according to embodiment 1 includes a flow rate changing step of changing the flow rate of the refrigerant flowing through the evaporator 4 to change the difference between the line internal pressures at the inlet and the outlet.
(7) According to the operation method of the refrigeration apparatus 100 according to embodiment 1, the flow rate changing step changes the flow rate of the refrigerant flowing through the evaporator 4 by changing the rotation speed of the compressor 1.
(8) According to the operation method of the refrigeration apparatus 100 according to embodiment 1, the flow velocity changing step changes the opening degree of the flow rate adjustment valve provided at the inlet of the evaporator to change the flow velocity of the refrigerant flowing through the heat transfer pipe 41.
With such a configuration, the refrigeration apparatus 100 can change the flow rate of the refrigerant flowing through the evaporator 24 using the compressor 1 and the flow rate adjustment valve that constitute the refrigeration cycle. Therefore, the pressure loss given to the refrigerant flowing through the evaporator 4 can be appropriately changed according to the physical properties of the zeotropic refrigerant used in the refrigeration apparatus 100. This enables the refrigeration apparatus 100 to obtain the effect described in (1) above.
The refrigeration apparatus 100 according to embodiment 2 is different from the refrigeration apparatus 100 according to embodiment 1 in that the composition of the refrigerant circulating in the refrigeration apparatus 100 is limited. In embodiment 2, a description will be given with a focus on a modification from embodiment 1.
The zeotropic refrigerant mixture circulating through the refrigeration apparatus 100 of embodiment 2 is a refrigerant mixture of R32, R125, R134a, R1234yf and carbon dioxide, and the ratio X of R32 isR3236% by weight, ratio X of R125 R12530 wt%, ratio X of R134aR134a14% by weight, proportion X of R1234yfR1234yf14% by weight, proportion X of carbon dioxideco2Is 6 wt%. The following effects can be obtained by using such a refrigerant.
First, although each single refrigerant has physical properties that are advantages or disadvantages, by mixing a plurality of refrigerants, the disadvantages can be reduced and the advantages can be increased. Since the operating pressure is high as the physical property of R32, the effect of performance degradation due to pressure loss can be reduced, and the refrigeration capacity can be improved even when used at low temperatures such as in supermarket showcases. Since the physical property of R1234yf is that the global warming potential is 0, the environmental impact can be reduced. Since R125 and R134a are nonflammable in physical properties, flammability, which is a characteristic of R32 and R1234yf, can be reduced, thereby improving safety. As the physical properties of carbon dioxide, since carbon dioxide is a natural refrigerant having a global warming coefficient of 0 and is nonflammable, it can contribute to both reduction of environmental impact and improvement of safety. Therefore, the above-mentioned non-azeotropic refrigerant mixture has little influence on the global environment and can improve safety and performance at the same time.
The mixed refrigerant is a non-azeotropic mixed refrigerant, which changes in temperature due to phase change at the same pressure, and the downstream side has a higher temperature than the upstream side during evaporation. Therefore, when a zeotropic refrigerant mixture is used as the refrigerant of the refrigeration apparatus 100, the temperature on the inlet side of the evaporator 4 becomes lower than the temperature on the outlet side of the evaporator 4. In particular, since the mixed refrigerant including R32 can improve the cooling capacity even when used at a low temperature, the refrigeration apparatus 100 is often used in low-temperature equipment such as showcases, in which the saturation temperature is below the freezing point. Therefore, in the case where the mixed refrigerant including R32 is used in a low-temperature apparatus in which the saturation temperature is below the freezing point, frost formation occurs in the evaporator 4.
Fig. 5 shows a mollier diagram of a zeotropic refrigerant mixture used in the refrigeration apparatus 200 according to embodiment 2 of the present invention. In the case of the non-azeotropic refrigerant mixture in embodiment 2, the composition shown above is formed, and when the non-azeotropic refrigerant mixture is subjected to a phase change at a constant pressure in a low temperature region as shown in fig. 5, the temperature gradient of the non-azeotropic refrigerant mixture at the inlet and outlet of the evaporator 4 becomes-5 ℃. That is, in the low temperature region, particularly, when heat exchange is performed without causing pressure loss of the refrigerant flowing inside the evaporator 4, the temperature difference between the inlet and the outlet of the evaporator 4 is about 5 ℃. For example, the temperature at the inlet side of the evaporator 4 is-12 deg.C, the temperature at the outlet side of the evaporator 4 is-7 deg.C, and the temperature at the inlet side of the evaporator 4 is greatly reduced. Therefore, on the inlet side of evaporator 4 where the temperature of the refrigerant is lower, cooling of the air in contact with heat transfer tubes 41 and fins 42 is promoted, moisture included in the air solidifies and is likely to frost, and the amount of frost is larger than on the outlet side of evaporator 4. Therefore, the influence of the uneven frost formation on the cooling performance of the cooling device 200 also increases.
Therefore, also in embodiment 2, the refrigerant saturation temperature difference between the inlet and the outlet of the evaporator 4 is calculated from the physical properties of the non-azeotropic refrigerant mixture. In the refrigeration apparatus 200, the piping pressure loss may be applied to the refrigerant flowing through the evaporator 4 so that the pressure difference between the inlet and the outlet of the evaporator 4 is equal to the pressure difference between the inlet and the outlet of the evaporator 4 when the temperature of the refrigerant flowing through the evaporator 4 is equal to or higher than the other.
As described above, even when a non-azeotropic refrigerant mixture having a composition of 36 wt% R32, 30 wt% R125, 14 wt% R134a, 14 wt% R1234yf, and 6 wt% carbon dioxide is used as the refrigerant circulating in the refrigeration apparatus 200 as in embodiment 2, the refrigerant temperature in the evaporator 4 is made almost equal by configuring the pipe pressure loss in the evaporator 4 to be almost the same as the temperature gradient of the refrigerant, and it is possible to prevent the heat exchange performance from being lowered due to uneven frost formation in the evaporator 4. At the same time, by using the non-azeotropic refrigerant mixture according to embodiment 2, the refrigeration apparatus 200 can reduce the influence on the global environment and can improve both safety and refrigeration performance.
The composition of each refrigerant constituting the zeotropic refrigerant mixture of embodiment 2 may be a refrigerant having a different composition ratio of each refrigerant within a range of less than ± 3 wt%. That is, any refrigerant may be used as long as it satisfies all of the following conditions: ratio X of R32R32(wt%) 33 < XR32A condition of < 39; ratio X of R125R125(wt%) 27 < XR125A condition of < 33; ratio X of R134aR134a(wt%) 11 < XR134aA condition of < 17; ratio X of R1234yfR1234yf(wt％)11＜XR1234yfA condition of < 17; ratio X of carbon dioxideCO2(wt%) 3 < XR125A condition of < 9; and XR32、XR125、XR134a、XR1234yfAnd Xco2The sum of (a) and (b) is 100 (wt%).
The refrigerant circulating through the refrigeration apparatus 200 according to embodiment 2 may be any one of R448A, R449A, and R407F. R448A, R449A, and R407F are non-azeotropic refrigerant mixtures, and even when any of them is used, the refrigerant temperature in the evaporator 4 is made almost uniform by configuring the refrigerant mixture so that the piping pressure loss applied to the refrigerant in the evaporator 4 is almost the same as the temperature gradient of the refrigerant, and the heat exchange performance can be prevented from being lowered due to uneven frost formation in the evaporator 4.
The physical properties of the zeotropic refrigerant mixture according to embodiment 2 are similar to those of R410A, and even when R410A is charged into the refrigeration apparatus 200 according to embodiment 2, operation can be performed without any problem. However, R410A is a pseudo azeotropic refrigerant mixture and is a refrigerant having almost no temperature gradient. That is, in fig. 5, the isotherm of the refrigerant is substantially horizontal as the isotherm of the pseudo-azeotropic refrigerant mixture present in the evaporator 4. Therefore, when R410A is used in the refrigeration apparatus 200 including the evaporator 4 designed according to the zeotropic refrigerant mixture of embodiment 2, the pressure on the outlet side is reduced by the pressure loss when the refrigerant flows in the evaporator 4, and the reduction in the refrigeration capacity of the refrigeration apparatus 200 is considered to be large.
Therefore, when R410A is used in the refrigeration apparatus 200, the evaporator 4 needs to be configured so that the piping pressure loss of the heat transfer pipe 41 is reduced in order to reduce the performance degradation when R410A is used. For example, when the zeotropic refrigerant mixture according to embodiment 2 is used, the refrigerant saturation temperature difference between the inlet and the outlet of the evaporator 4 in the low temperature region is about 5 ℃, and therefore the evaporator 4 is configured to apply a pressure loss corresponding to 5 ℃ to the refrigerant. However, when R410A is used, the pressure loss in the evaporator 4 is a temperature gradient of the zeotropic refrigerant mixture, and is a pressure loss corresponding to less than 5 ℃.
For example, the heat transfer tubes 41 of the evaporator 4 according to embodiment 2 are configured so that the pressure loss of the refrigerant flowing through the tubes at a normal flow rate is reduced, and the refrigeration apparatus 200 operates so that the refrigerant flows at a normal flow rate when R410A is used. Therefore, the refrigerant flowing through the evaporator 4 flows so that the pressure loss becomes a temperature gradient of the zeotropic refrigerant mixture and is less than 5 ℃, and therefore flows out of the evaporator 4 while maintaining almost the same pressure as the broken line C shown in fig. 5. On the other hand, when the non-azeotropic refrigerant mixture according to embodiment 2 is used, the refrigerant is made to flow at a flow velocity higher than normal, and when the flow velocity is high, the heat transfer tubes 41 may be configured so that the pressure loss of the refrigerant in the tubes becomes large. When the flow rate of the refrigerant is raised, the pressure loss of the refrigerant in the evaporator 4 increases, and the outlet pressure becomes lower than the inlet of the evaporator 4 as shown by a solid line D in fig. 5, so that a temperature difference between the refrigerant at the inlet and the refrigerant at the outlet of the evaporator 4 does not occur, and uneven frost formation does not occur. According to the above-described means, the refrigeration apparatus 200 can use both the non-azeotropic refrigerant mixture and the pseudo-azeotropic refrigerant mixture without reducing the refrigeration capacity.
Fig. 6 is a schematic diagram showing the configuration of the evaporator 24 of the refrigeration apparatus 200 according to embodiment 2 of the present invention. For example, the heat transfer tube 41 of the evaporator 24 according to embodiment 2 is configured to apply a predetermined pressure loss to the refrigerant flowing through the tube. When R410A is used, the refrigeration apparatus 200 is configured such that the number of passages, which is the number of passages of the refrigerant flowing through the evaporator 24, is five as shown in fig. 2. On the other hand, when the zeotropic refrigerant mixture according to embodiment 2 is used, the refrigeration apparatus 200 is configured to switch the flow path of the refrigerant flowing through the evaporator 24, and the refrigerant passes through the evaporator 24 in one path as shown in fig. 6. In the evaporator 24 shown in fig. 6, the heat transfer tubes 41 are connected to the ends of the evaporator 24 by the hairpin tubes 45, and the refrigerant flows while turning back at both ends of the evaporator 24, whereby the flow path becomes long. Since the refrigerant flow path is long, the refrigerant passing through the evaporator 24 is reduced in pressure due to the line loss of the heat transfer pipe 41. With the above configuration, when a pseudo azeotropic refrigerant such as R410A is used in the refrigeration apparatus 200, the pressure loss of the refrigerant is reduced by shortening the flow path. In addition, when a zeotropic refrigerant mixture is used in the refrigeration apparatus 200, the pressure loss of the refrigerant can be increased by extending the flow path. By the above means, the refrigeration apparatus 200 can use both the pseudo-azeotropic refrigerant mixture and the non-azeotropic refrigerant mixture without reducing the refrigeration capacity.
(9) According to the refrigeration apparatus 200 of embodiment 2, the refrigerant is a mixed refrigerant of R32, R125, R134a, R1234yf, and carbon dioxide, and all of the following conditions are satisfied: ratio X of R32R32(wt%) 33 wt% < XR32A condition of < 39 wt%; ratio X of R125R125(wt.%) is 27 wt.% < XR125A condition of < 33 wt%; ratio X of R134aR134a(wt%) 11 wt% < XR134aA condition of < 17 wt%; ratio X of R1234yfR1234yf(wt%) 11 wt% < XR1234yfA condition of < 17 wt%; ratio X of carbon dioxideCO2(wt％)3 wt% < XCO2A condition of < 9 wt%; and XR32、XR125、XR134a、XR1234yfAnd XCO2Sum of (2) XtotalIs 100 wt%.
With such a configuration, refrigerating apparatus 200 has little influence on the global environment, and can improve safety and refrigerating performance at the same time
(10) According to the refrigeration apparatus 200 of embodiment 2, the refrigerant is R448A, R449A, or R407F.
(11) According to the refrigeration apparatus 200 according to embodiment 2, the refrigeration cycle can use R410A in common with a mixed refrigerant of R32, R125, R134a, R1234yf, and carbon dioxide, and at least one of the refrigerants of R448A, R449A, and R407F. With such a configuration, the refrigeration apparatus 200 can be used for various applications such as a low-temperature facility and others.
(12) According to the operation method of the refrigeration apparatus 200 according to embodiment 2, there is provided a tube length changing step of changing the tube length of the heat transfer tube 41 of the evaporator 24 through which the refrigerant passes to change the difference in the tube internal pressures at the inlet and outlet portions.
With such a configuration, the refrigeration apparatus 200 can apply a pressure loss to the refrigerant passing through the evaporator 24 according to the refrigerant used. Therefore, a plurality of types of refrigerants can be used for the refrigeration apparatus 200, and therefore the refrigeration apparatus 200 can be used for various purposes.
(13) According to the operation method of the refrigeration apparatus 200 according to embodiment 2, the conduit length changing step changes the number of passages of the refrigerant passing through the evaporator 24 to change the difference between the conduit internal pressures at the inlet and the outlet.
With such a configuration, refrigeration apparatus 200 can change the pressure loss applied to the refrigerant flowing through evaporator 24 even in evaporator 24 including normal heat transfer pipe 41. Further, by using the means described in (6) to (8) above together, the magnitude of the pressure loss applied to the refrigerant flowing in the evaporator 24 can be increased, and the pressure difference between the refrigerant at the inlet and the refrigerant at the outlet of the evaporator 24 can be appropriately adjusted.
Description of the reference numerals
A compressor; a condenser; a pressure relief device; an evaporator; refrigerant tubing; a condenser blower; an evaporator blower; a pressure sensor; an evaporator; a temperature sensor; a heat conducting pipe; a fin; a refrigerant distributor; a header; 45.. a U-shaped tube; a cooler; a control portion; a refrigeration device; a refrigeration device; a.. dotted line; a dotted line; a dotted line; solid line.
Claims (13)
1. A refrigerating device is characterized in that a refrigerating device is provided,
comprises a refrigeration cycle in which a compressor, a condenser, a pressure reducing device, and an evaporator are connected by refrigerant pipes and in which a refrigerant circulates,
the refrigerant is a non-azeotropic refrigerant mixture in which a plurality of types are mixed,
the evaporator reduces the pressure in the pipe during evaporation in accordance with the temperature gradient of the isotherm of the gas-liquid two-phase region of the non-azeotropic mixed refrigerant in the direction in which the refrigerant flows.
2. A cold appliance according to claim 1,
the sectional area of the heat conductive pipe of the evaporator increases in a direction in which the refrigerant flows.
3. A cold appliance according to claim 1,
the heat transfer pipe of the evaporator includes a resistance unit in a pipe line, and the resistance unit serves as resistance to the flow of the refrigerant.
4. A refrigerating device as recited in any one of claims 1 to 3,
the pressure in the tube during the evaporation is reduced by controlling the flow rate of the refrigerant through the evaporator.
5. A refrigerating device as recited in any one of claims 1 to 4,
the refrigerant is a mixed refrigerant of R32, R125, R134a, R1234yf and carbon dioxide,
and all the following conditions are met:
ratio X of R32R3233 wt% < XR32A condition of < 39 wt%;
ratio X of R125R12527 wt% < XR125A condition of < 33 wt%;
ratio X of R134aR134a11 wt% < XR134aA condition of < 17 wt%;
ratio X of R1234yfR1234yf11 wt% < XR1234yfA condition of < 17 wt%;
ratio X of carbon dioxideCO23 wt% < XCO2A condition of < 9 wt%; and
XR32、XR125、XR134a、XR1234yfand XCO2Sum of (2) XtotalIs 100 wt%.
6. A refrigerating device as recited in any one of claims 1 to 4,
the refrigerant is R448A, R449A, or R407F.
7. A cold appliance according to claim 5 or 6,
the refrigeration cycle is configured such that: corresponds to both a mixed refrigerant of R32, R125, R134a, R1234yf and carbon dioxide, at least one of the refrigerants of R448A, R449A and R407F, and R410A.
8. A method for operating a refrigeration device provided with a refrigeration cycle in which a compressor, a condenser, a pressure reducing device, and an evaporator are connected by refrigerant pipes and in which a refrigerant circulates,
the refrigerant is a non-azeotropic refrigerant mixture in which a plurality of types are mixed,
it is characterized in that the preparation method is characterized in that,
the method for operating the refrigeration device includes:
a detection step of detecting in-line pressures at an inlet portion of the evaporator and an outlet portion of the evaporator; and
a pressure adjusting step of making a difference between the in-line pressures in the inlet portion and the outlet portion coincide with a temperature gradient of an isotherm of a gas-liquid two-phase region of the refrigerant.
9. The method of operating a refrigeration apparatus according to claim 8,
the method includes a pipe length changing step of changing a pipe length of a heat transfer pipe of the evaporator through which the refrigerant passes, thereby changing a difference between the pipe internal pressures of the inlet portion and the outlet portion.
10. The method of operating a refrigeration apparatus according to claim 8 or 9,
the pressure adjusting step includes a flow rate changing step of changing a flow rate of the refrigerant flowing through the evaporator to change a difference between the in-line pressures in the inlet portion and the outlet portion.
11. The method of operating a refrigeration device according to claim 10,
the flow rate changing step changes the flow rate of the refrigerant flowing through the evaporator by changing the operating frequency of the compressor.
12. The method of operating a refrigeration apparatus according to claim 10 or 11,
the flow rate changing step changes the flow rate of the refrigerant flowing through the evaporator by changing an opening degree of a flow rate regulating valve provided at the inlet of the evaporator.
13. The method of operating a refrigeration device according to claim 9,
the tube length changing step changes the difference between the tube internal pressures in the inlet portion and the outlet portion by changing the number of passages of the refrigerant passing through the evaporator.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/JP2017/026803 WO2019021364A1 (en) | 2017-07-25 | 2017-07-25 | Refrigeration device and refrigeration device operation method |
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| Publication Number | Publication Date |
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| CN110914608A true CN110914608A (en) | 2020-03-24 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
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| CN201780093104.3A Pending CN110914608A (en) | 2017-07-25 | 2017-07-25 | Refrigeration device and method for operating refrigeration device |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JP6765538B2 (en) |
| CN (1) | CN110914608A (en) |
| WO (1) | WO2019021364A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2021070314A1 (en) * | 2019-10-10 | 2021-04-15 | 三菱電機株式会社 | Refrigeration cycle device |
| CN116802442A (en) * | 2021-02-02 | 2023-09-22 | 三菱电机株式会社 | Refrigeration cycle device |
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| JPH06272998A (en) * | 1993-03-18 | 1994-09-27 | Toshiba Corp | Refrigerator |
| CN1143735A (en) * | 1995-08-04 | 1997-02-26 | 三菱电机株式会社 | Refrigerator |
| JPH09133433A (en) * | 1995-11-07 | 1997-05-20 | Sanyo Electric Co Ltd | Heat exchanger |
| CN1598435A (en) * | 2004-07-22 | 2005-03-23 | 春兰(集团)公司 | Method for arranging refrigerant of heat pump air conditioner and air conditioner using said method thereof |
| CN102105761A (en) * | 2008-06-10 | 2011-06-22 | 汉拏空调株式会社 | Vehicle air-conditioning system employing tube-fin-type evaporator using HFO 1234yf material refrigerant |
| CN102947410A (en) * | 2010-06-22 | 2013-02-27 | 阿科玛股份有限公司 | Heat transfer compositions of hydrofluorocarbons and a hydrofluoroolefin |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH08145490A (en) * | 1994-11-17 | 1996-06-07 | Matsushita Refrig Co Ltd | Heat exchanger for heat pump air conditioner |
| US7655610B2 (en) * | 2004-04-29 | 2010-02-02 | Honeywell International Inc. | Blowing agent compositions comprising fluorinated olefins and carbon dioxide |
| WO2017149642A1 (en) * | 2016-03-01 | 2017-09-08 | 三菱電機株式会社 | Refrigeration cycle device |
-
2017
- 2017-07-25 WO PCT/JP2017/026803 patent/WO2019021364A1/en active Application Filing
- 2017-07-25 CN CN201780093104.3A patent/CN110914608A/en active Pending
- 2017-07-25 JP JP2019532244A patent/JP6765538B2/en not_active Expired - Fee Related
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH06272998A (en) * | 1993-03-18 | 1994-09-27 | Toshiba Corp | Refrigerator |
| CN1143735A (en) * | 1995-08-04 | 1997-02-26 | 三菱电机株式会社 | Refrigerator |
| JPH09133433A (en) * | 1995-11-07 | 1997-05-20 | Sanyo Electric Co Ltd | Heat exchanger |
| CN1598435A (en) * | 2004-07-22 | 2005-03-23 | 春兰(集团)公司 | Method for arranging refrigerant of heat pump air conditioner and air conditioner using said method thereof |
| CN102105761A (en) * | 2008-06-10 | 2011-06-22 | 汉拏空调株式会社 | Vehicle air-conditioning system employing tube-fin-type evaporator using HFO 1234yf material refrigerant |
| CN102947410A (en) * | 2010-06-22 | 2013-02-27 | 阿科玛股份有限公司 | Heat transfer compositions of hydrofluorocarbons and a hydrofluoroolefin |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2019021364A1 (en) | 2019-01-31 |
| JP6765538B2 (en) | 2020-10-07 |
| JPWO2019021364A1 (en) | 2020-02-27 |
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