JPWO2019021364A1 - Refrigeration apparatus and method of operating refrigeration apparatus - Google Patents

Abstract

In a refrigeration system using a non-azeotropic mixed refrigerant having a temperature gradient, it is an object to prevent a decrease in the COP of the refrigeration system and a decrease in the refrigeration capacity of the refrigeration system by preventing eccentric frost. A compressor, a condenser, a decompression device, and an evaporator are connected by a refrigerant pipe, and a refrigeration cycle in which the refrigerant circulates is provided.The refrigerant is a non-azeotropic mixed refrigerant in which a plurality of types are mixed. The apparatus is characterized in that the pressure in the pipeline during the evaporation process is reduced along the flowing direction of the refrigerant in accordance with the temperature gradient of the non-azeotropic mixed refrigerant.

Description

  The present invention relates to a refrigeration apparatus, and more particularly to a refrigeration apparatus to which a non-azeotropic mixed refrigerant is applied and an operation method of the refrigeration apparatus.

  2. Description of the Related Art Conventionally, a refrigerating apparatus having a refrigerating cycle in which an evaporator, a compressor, a condenser, and a decompression device are respectively connected by pipes through which a refrigerant circulates, and circulates the refrigerant is known.

  In a refrigerating device such as an air conditioner or a refrigerator, a heat exchanger acting as an evaporator is opposed to a heat exchange air flowing direction and a refrigerant flowing direction in opposite directions, and the heat exchange air and the refrigerant are opposed to each other. Is known in which the flow rate is reduced to reduce the heat exchange loss to improve the performance (for example, see Patent Document 1).

  On the other hand, a non-azeotropic mixed refrigerant in which a plurality of types of refrigerant are mixed may be used as a refrigerant used in a refrigeration apparatus (for example, see Patent Document 2). Counterflow can also be achieved for an evaporator of a refrigeration system using a non-azeotropic mixed refrigerant. In particular, the temperature of the non-azeotropic refrigerant mixture changes due to a phase change under the same pressure. That is, since the non-azeotropic mixed refrigerant has a temperature gradient in the evaporation process, for example, in the case of an evaporator, the temperature of the upstream side is lower than that of the downstream side in the evaporation process. Therefore, the temperature difference between the refrigerant and the heat source medium such as air or water can be reduced, and the coefficient of performance (COP) is improved.

JP-A-2015-14109 JP-A-7-208822

  However, in low-temperature equipment whose saturation temperature is below the freezing point, frost is formed on the evaporator. When a non-azeotropic refrigerant mixture is used in the evaporation process of a low-temperature device in which frost is generated, frost formation in the evaporator is biased. In other words, at the inlet side of the evaporator having a low temperature of the non-azeotropic refrigerant mixture having a temperature gradient such that the refrigerant temperature changes by the phase change under the same pressure as described above, the cooling of the air is promoted, and the frost amount is reduced. At the outlet side of the evaporator where the temperature of the refrigerant is high, cooling of the air does not proceed and the amount of frost is reduced. As described above, when the frost is unevenly formed in the evaporator, the space between the fins on the inlet side of the evaporator is quickly formed even if the entire amount of frost is the same as compared to the case where the frost is uniform. Clogging due to frost reduces the heat exchange rate. Therefore, the influence of the deterioration of the heat exchange rate due to deviated frost is greater than the improvement of the heat exchange rate due to the counterflow of the refrigerant and the heat source medium, the evaporation pressure in the evaporator is reduced, and the COP of the refrigerating device and the refrigerating device are reduced. However, there was a problem that the refrigerating capacity of the steel was reduced.

  The present invention relates to a refrigeration system using a non-azeotropic mixed refrigerant having a temperature gradient, by preventing localized frost, thereby preventing a reduction in the COP of the refrigeration system and the refrigeration capacity of the refrigeration system. It is intended to provide a driving method.

  The refrigeration apparatus according to the present invention includes a refrigeration cycle in which a compressor, a condenser, a decompression device, and an evaporator are connected by a refrigerant pipe and a refrigerant circulates therein, and the refrigerant is a mixture of a plurality of types. The refrigerant is a non-azeotropic mixed refrigerant, and the evaporator reduces a pressure in a pipe in an evaporation process along a flowing direction of the refrigerant in accordance with a temperature gradient of the non-azeotropic mixed refrigerant.

  According to the present invention, with the configuration described above, in a refrigeration apparatus using a non-azeotropic mixed refrigerant having a temperature gradient, the refrigerant temperature in the evaporator can be made substantially uniform, and the frost formation of the evaporator can be biased. It is an object of the present invention to obtain a refrigeration apparatus that suppresses a decrease in COP and refrigeration capacity of the refrigeration apparatus.

1 is a schematic diagram illustrating an entire configuration of a refrigeration apparatus according to Embodiment 1 of the present invention. FIG. 2 is a schematic diagram illustrating a configuration of an evaporator of the refrigeration apparatus according to Embodiment 1 of the present invention. FIG. 2 shows a Mollier diagram of a non-azeotropic refrigerant mixture used in the refrigeration apparatus according to Embodiment 1 of the present invention. FIG. 2 is a control flow chart of the refrigeration apparatus according to Embodiment 1 of the present invention. FIG. 7 shows a Mollier diagram of a non-azeotropic refrigerant mixture used in a refrigeration apparatus according to Embodiment 2 of the present invention. FIG. 6 is a schematic diagram illustrating a configuration of an evaporator of a refrigeration apparatus according to Embodiment 2 of the present invention.

Embodiment 1 FIG.
FIG. 1 is a schematic diagram illustrating an entire configuration of a refrigeration apparatus 100 according to Embodiment 1 of the present invention. In the drawings, the same or corresponding parts are denoted by the same reference numerals. In a refrigeration apparatus 100 according to the first embodiment, a compressor 1, a condenser 2, a decompression device 3, and an evaporator 4 are sequentially connected by a refrigerant pipe 5 as shown in FIG. The refrigeration apparatus 100 has a refrigeration cycle in which a refrigerant circulates in the order of the compressor 1, the condenser 2, the decompression device 3, the evaporator 4, and the compressor 1. The control unit 60 controls each device constituting the refrigeration device 100.

(Compressor 1)
The compressor 1 sucks in a refrigerant, compresses it, and discharges it in a high-temperature and high-pressure gas state. The compressor 1 may be configured such that the number of revolutions is controlled by, for example, an inverter circuit, and the amount of refrigerant discharged can be adjusted by controlling the number of revolutions.

(Condenser 2)
The refrigerant compressed into the high-pressure and high-pressure gas state by the compressor 1 flows into the condenser 2, and performs heat exchange between the refrigerant and the heat source to cool the refrigerant to a low-temperature and high-pressure liquid state. Examples of the heat source include air, water, and brine. In the first embodiment, the heat source of the condenser 2 is outside air, which is outdoor air. The condenser 2 performs heat exchange between the outside air and the refrigerant. Further, in the first embodiment, in order to promote heat exchange of the condenser 2, the condenser blower 6 that blows outside air to the condenser 2 when the refrigerant is circulating in the refrigeration apparatus 100 is provided. The condenser blower 6 may be configured to be capable of adjusting the air volume.

(Decompression device 3)
The decompression device 3 receives the low-temperature and high-pressure liquid refrigerant cooled by the condenser 2 and decompresses and expands the refrigerant to a low-temperature and low-pressure liquid state. The pressure reducing device 3 is configured by, for example, a refrigerant flow control unit such as an electronic expansion valve or a temperature-sensitive expansion valve, or a capillary tube (capillary tube).

(Evaporator 4)
The evaporator 4 receives the refrigerant in a low-temperature and low-pressure liquid state that has been decompressed and expanded by the decompression device 3, performs heat exchange between the refrigerant and the object to be cooled, absorbs the heat of the object to be cooled by the refrigerant, and To cool. The refrigerant evaporates and becomes a high-temperature low-pressure gas state when cooling the object to be cooled. In the first embodiment, the object to be cooled is indoor air. That is, the evaporator 4 performs heat exchange between indoor air and the refrigerant. Furthermore, in the first embodiment, in order to promote heat exchange between the indoor air and the refrigerant in the evaporator 4, the evaporator blows the indoor air to the evaporator 4 when the refrigerant is circulating in the refrigeration apparatus 100. It has a blower 7. The evaporator blower 7 may be configured to be capable of adjusting the air volume.

  A specific configuration of the evaporator 4 will be described with reference to FIG. The evaporator 4 is a plate-fin tube heat exchanger composed of 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 the heat transfer tubes 41 is five and the number of the fins 42 is 28. However, the number and the number are only examples, and the present invention is not limited to this number and the number.

  FIG. 2 is a schematic diagram illustrating a configuration of the evaporator 4 of the 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. First, the low-temperature and low-pressure liquid state refrigerant decompressed and expanded by 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 to a plurality of outlets of the refrigerant distributor 43, and flows from the respective outlets of the refrigerant distributor 43 to the heat transfer tubes 41. The refrigerant flowing into the heat transfer tubes 41 flows along the axial direction of the heat transfer tubes 41. The surfaces of the heat transfer tubes 41 and the fins 42 come into contact with indoor air to be cooled, which is blown by the blower 7 provided in the evaporator 4. The indoor air blown toward the fins 42 of the evaporator 4 flows in a direction opposite to the flow of the refrigerant flowing inside the evaporator 4. The refrigerant flowing inside the heat transfer tube 41 exchanges heat with indoor air in contact with the heat transfer tube 41 and the fins 42 to absorb heat of the indoor air. The refrigerant that has exchanged heat with indoor air in the heat transfer tube 41 flows in from the inlet of the header 44, merges in the header 44, and flows from the outlet of the header 44 to the compressor 1.

  FIG. 3 shows a Mollier diagram of the non-azeotropic mixed refrigerant used in refrigeration apparatus 100 according to Embodiment 1 of the present invention. The non-azeotropic mixed refrigerant is a mixture of two or more refrigerants having different boiling points, and in a gas-liquid two-phase state, the pressure saturation temperature of the refrigerant changes according to the degree of dryness even under a constant pressure. That is, when the refrigerant in the evaporator 4 is evaporated along the line with a constant pressure indicated by the dotted line A in FIG. 3, the temperature of the inlet of the evaporator 4 decreases and the temperature of the outlet increases. Therefore, as shown by the dotted line B in FIG. 3, the temperature of the non-azeotropic mixed refrigerant flowing through the evaporator 4 can be made uniform by continuously lowering the pressure inside the evaporator 4 at a predetermined gradient. . By keeping the inlet temperature and the outlet temperature of the evaporator 4 uniform, it is possible to suppress the uneven formation of frost generated in the evaporator 4.

  When the pressure inside the evaporator 4 is gradually reduced, a pressure difference occurs between the inlet and the outlet of the evaporator 4. The relationship between the pressure of the refrigerant flowing inside the evaporator 4 and the saturation temperature 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 temperature is made uniform at the inlet and the outlet of the evaporator 4 is uniquely determined according to the composition of the refrigerant. For this reason, in the actual refrigerating apparatus 100, the pressure difference of the refrigerant between the inlet and the outlet of the evaporator 4 is set to the value of the refrigerant at the inlet and the outlet of the evaporator 4 when the temperature of the refrigerant flowing through the evaporator 4 is made uniform. By making the same as the pressure difference, it is possible to suppress the uneven formation of frost on the evaporator 4.

  As means for continuously lowering the pressure of the refrigerant inside the evaporator 4 at a predetermined gradient, there is a means for changing the inner diameter of the heat transfer tube 41 through which the refrigerant passes stepwise. The heat transfer tube 41 constituting the evaporator 4 is usually a tube having a uniform inner diameter. For example, the cross-sectional area of the heat transfer tube 41 is gradually reduced from the inlet to the outlet of the evaporator 4 so that the refrigerant flowing inside the tube is reduced. Pressure can be reduced. Alternatively, for example, the cross-sectional area of the heat transfer tube 41 may be reduced stepwise from the inlet to the outlet of the evaporator 4.

  Alternatively, a resistance may be provided in the pipe of the heat transfer tube 41, and the pressure of the refrigerant flowing inside may be reduced by the pipe resistance. For example, by providing irregularities on the inner wall surface of the heat transfer tube 41, the pipe resistance can be increased, and the pressure loss of the refrigerant flowing inside the heat transfer tube 41 can be increased.

  Further, it is also possible to take measures such as lengthening the heat transfer tube 41 to increase the pressure loss due to the line resistance, and 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 applied non-azeotropic refrigerant mixture.

  Further, by controlling the flow rate of the refrigerant passing through the evaporator 4 such as by providing a flow control valve at the inlet of the evaporator 4 or controlling the operation speed of the compressor 1, the operating state and the applied non- Regardless of the type of the boiling mixed refrigerant, the pressure inside the evaporator 4 can be continuously reduced at a predetermined gradient.

  As described above, when a refrigerant having a temperature gradient is used in the evaporation process, the refrigerant pressure in the evaporator 4 is substantially reduced by configuring the pipe pressure loss in the evaporator 4 to be substantially the same as the temperature gradient of the refrigerant. It can be uniform. Accordingly, it is possible to prevent the performance of the refrigeration apparatus 100 from deteriorating due to the formation of frost on the inlet side of the evaporator 4 into which the refrigerant flows.

(Control of refrigeration system 100)
FIG. 4 is a control flowchart of the refrigeration apparatus 100 according to the first embodiment of the present invention. The refrigeration apparatus 100 is used for a plurality of applications such as a unit cooler and a showcase. 1 is a cooler 50, and the cooler 50 corresponds to a unit cooler or a showcase. Parts other than the broken line shown in FIG. 1 are so-called heat source units. In particular, when the cooler 50 cannot be directly controlled by the control unit 60, the control unit 60 controls the operation of the refrigeration apparatus 100 by acquiring the pressure, temperature, and operating conditions of each unit of the heat source unit.

(Step i)
In step i, a refrigerant circulation amount Gr circulating in the refrigeration apparatus 100 is calculated. First, the suction pressure Ps of the compressor 1 is detected by a pressure sensor 20 provided in a pipe on the suction side of the compressor 1. Further, a suction temperature Th of the compressor 1 is detected by a temperature sensor 30 provided in a pipe on a suction side of the compressor 1. Note that the refrigerant circulation amount Gr is calculated by the following equation.
Gr = F × Vst × ηv × ρs × 3600 × 10 ⁻⁶
Here, F [Hz]: operating frequency of the compressor 1, Vst [cc]: displacement of the compressor 1, ηv: volumetric efficiency of the compressor 1, ρs [kg / m ³ ]: suction gas of the compressor 1 Density. F can be obtained from the operation data of the refrigeration apparatus 100 as the operating frequency of the compressor. Vst and ηv are values unique to the compressor 1 and may be stored in the control unit 60 in advance. ρs takes a unique value for each refrigerant type, and can be obtained from the suction pressure Ps and the suction temperature Th. Step i is referred to as a refrigerant circulation amount calculation step.

(Step ii)
In step ii, the pressure loss ΔP between the inlet and the outlet of the evaporator 4 is calculated from the refrigerant circulation amount Gr obtained in step i. ΔP is calculated by the following equation.
ΔP = α × f × (l / d) × (ρu ² / 2g)
Here, l [m]: pipe length, d [m]: pipe diameter, ρ [kg / m ³ ]: liquid density, u [m / s]: refrigerant flow rate, f: friction loss coefficient, α: correction coefficient ,. Note that α, f, l, d, and g are fixed values. It can be seen from the equation that as the refrigerant flow velocity u and the refrigerant density ρ increase, the pressure loss ΔP increases. The refrigerant flow velocity u is obtained from the refrigerant circulation amount Gr. As the pressure loss ΔP, the value of ΔP obtained from the relationship between the refrigerant density ρ and the refrigerant circulation amount Gr may be stored in the control unit 60 in advance. The relationship between the pressure loss ΔP, the refrigerant density ρ, and the refrigerant circulation amount Gr may be stored in the control device in advance as a look-up table. Step ii is called a 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 from Pein = Ps + ΔP. In addition, the steps i to iii are collectively referred to as a detection step of detecting a pressure in a pipe at an inlet of the evaporator and an outlet of the evaporator.

(Step iv)
The saturation temperature Tein at the inlet of the evaporator 4 is converted from Pein. Further, the saturation temperature Teout at the outlet of the evaporator 4 is converted from the suction pressure Ps. The conversion is obtained from a saturation pressure conversion table specific to the type of refrigerant. Step iv is referred to as a temperature gradient detection step of finding a temperature gradient between the inlet of the evaporator 4 and the outlet of the evaporator 4.

(Step v)
The compressor operating frequency F is controlled so that the difference ΔTe = Teout−Tein between the saturation temperature at the evaporator inlet and the saturation temperature at the evaporator outlet becomes zero, and the refrigerant circulation amount Gr is changed. For example, when ΔTe> 0, the compressor operating frequency F is increased, and when ΔTe ≦ 0, the compressor operating frequency F is decreased. As ΔTe approaches zero, the pressure loss becomes parallel to the temperature gradient. Step v is called a flow rate changing step of changing the operating frequency F of the compressor 1 and changing the flow rate u of the refrigerant flowing through the refrigeration cycle. Step iv and step v are collectively referred to as a pressure adjustment step. In step v, instead of changing the operating frequency F of the compressor 1, the opening degree of the flow control valve provided on the inlet side of the evaporator 4 is changed to change the flow velocity u of the refrigerant flowing through the refrigeration cycle. Is also good. The flow regulating valve may be the pressure reducing device 3. This control is performed when the control unit 60 can control the cooler 50.

(1) According to the refrigeration apparatus 100 according to the first embodiment, the compressor 1, the condenser 2, the decompression device 3, and the evaporator 4 are connected by the refrigerant pipe 5, and the refrigeration in which the refrigerant circulates inside. Provide a cycle. The refrigerant is a non-azeotropic mixed refrigerant in which a plurality of types are mixed, and the evaporator 4 adjusts the pressure in the pipeline during the evaporation process to the refrigerant in accordance with the temperature gradient of the isotherm in the gas-liquid two-phase region of the non-azeotropic mixed refrigerant. Characterized in that it is lowered along the direction in which
With such a configuration, the refrigeration apparatus 100 can suppress the difference in the temperature of the refrigerant between the inlet side and the outlet side of the evaporator 4. Therefore, the amount of frost on the inlet side and the outlet side of the evaporator 4 is averaged, so that it is possible to prevent the heat exchange performance of the evaporator 4 from deteriorating due to uneven frost formation.

(2) According to the refrigeration apparatus 100 according to Embodiment 1, the heat transfer tube 41 of the evaporator 4 has a reduced cross-sectional area along the direction in which the refrigerant flows.
(3) According to the refrigeration apparatus 100 according to the first embodiment, the heat transfer tube 41 of the evaporator 4 includes a resistance unit serving as a resistance to the flow of the refrigerant in the pipe.
(4) According to the refrigeration apparatus 100 according to the first embodiment, the pressure in the pipeline in the evaporation process is reduced by controlling the flow rate of the refrigerant passing through the evaporator 4.
With such a configuration, the refrigeration apparatus 100 can suppress the temperature difference between the inlet and the outlet of the evaporator 4 by causing the non-azeotropic mixed refrigerant to flow through the evaporator 4 at a predetermined flow rate. In addition, by appropriately combining the above-described means (2) to (4), the pressure loss applied to the refrigerant flowing in the evaporator 4 can be appropriately controlled according to the refrigerant used in the refrigeration apparatus 100.

(5) According to the operation method of the refrigeration apparatus 100 according to Embodiment 1, the refrigerant is a non-azeotropic mixed refrigerant in which a plurality of types are mixed. The method includes a detecting step of detecting an in-pipe pressure at the outlet, and a pressure adjusting step of adjusting a difference in the in-pipe pressure between the inlet and the outlet to a temperature gradient of the refrigerant.
By operating as described above, the refrigeration apparatus 100 can obtain the effect described in the above (1).

(6) According to the operation method of the refrigeration apparatus 100 according to the first embodiment, the flow rate change that changes the flow rate of the refrigerant flowing through the evaporator 4 to change the pressure difference in the pipe between the inlet and the outlet. With steps.
(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 rate changing step changes the opening degree of the flow control valve installed at the inlet of the evaporator to change the refrigerant flowing through the heat transfer tube 41. Change the flow rate.
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 applied to the refrigerant flowing through the evaporator 4 can be appropriately changed according to the physical properties of the non-azeotropic mixed refrigerant used in the refrigeration apparatus 100. Thereby, the refrigeration apparatus 100 can obtain the effect described in the above (1).

Embodiment 2 FIG.
Refrigeration apparatus 100 according to Embodiment 2 is different from refrigeration apparatus 100 according to Embodiment 1 in that the composition of the refrigerant circulating in refrigeration apparatus 100 is limited. In the second embodiment, the description will be focused on the changes from the first embodiment.

The non-azeotropic refrigerant mixture circulating through the refrigeration apparatus 100 according to Embodiment 2 is a refrigerant mixture of R32, R125, R134a, R1234yf, and carbon dioxide, and the ratio of _R32 X _R32 is 36 wt%, and the ratio of R125. X _R125 is 30 wt%, the proportion _{X R134a} is 14 wt% of R134a, ratio _{X R1234yf} is 14 wt% of the R1234yf, the proportion _{X of co2} carbon dioxide is 6 wt%. By using such a refrigerant, the following effects can be obtained.

  First, each single refrigerant has physical properties that are advantages or disadvantages, but by mixing a plurality of refrigerants, the disadvantages can be reduced and the advantages can be increased. As a physical property of R32, since the operating pressure is high, the effect of performance deterioration due to pressure loss can be reduced, and the refrigerating capacity can be improved even at low temperatures such as a supermarket showcase. As a physical property of R1234yf, the global warming potential is 0, so that the environmental impact can be reduced. Since the physical properties of R125 and R134a are nonflammable, the flammability, which is the characteristic of R32 and R1234yf, can be reduced and safety can be improved. Regarding the physical properties of carbon dioxide, it has a global warming potential of 0 and is a nonflammable natural refrigerant, so it can contribute to both reduction of environmental impact and improvement of safety. Therefore, the above-mentioned non-azeotropic mixed refrigerant can reduce the influence on the global environment and can simultaneously improve safety and performance.

  The mixed refrigerant is a non-azeotropic mixed refrigerant, and the temperature of the non-azeotropic mixed refrigerant changes due to a phase change under the same pressure, and the temperature of the downstream side becomes higher than that of the upstream side in the evaporation process. Therefore, when a non-azeotropic mixed refrigerant is used as the refrigerant of the refrigeration apparatus 100, the temperature of the inlet side of the evaporator 4 becomes lower than that of the outlet side of the evaporator 4. In particular, since the mixed refrigerant containing R32 has an improved refrigerating capacity even when used at a low temperature, the refrigerating apparatus 100 is often used for low-temperature equipment such as a showcase whose saturation temperature is below the freezing point. Therefore, when the mixed refrigerant containing R32 is used in a low-temperature device whose saturation temperature is below the freezing point, frost is formed on the evaporator 4.

  FIG. 5 shows a Mollier diagram of a non-azeotropic refrigerant mixture used in refrigeration apparatus 200 according to Embodiment 2 of the present invention. In the case of the non-azeotropic refrigerant mixture according to Embodiment 2, the composition is as described above, and as shown in FIG. 5, when the non-azeotropic refrigerant mixture undergoes a phase change under a constant pressure in a low temperature range, The temperature gradient of the non-azeotropic refrigerant mixture at the inlet and outlet of the evaporator 4 is -5C. That is, in a low-temperature region, when the refrigerant flowing inside the evaporator 4 is subjected to heat exchange without causing a pressure loss, the temperature difference between the inlet and the outlet of the evaporator 4 is about 5 ° C. For example, the temperature on the inlet side of the evaporator 4 becomes −12 ° C., the temperature on the outlet side of the evaporator 4 becomes −7 ° C., and the temperature on the inlet side of the evaporator 4 drops significantly. Therefore, on the inlet side of the evaporator 4 where the temperature of the refrigerant is lower, the cooling of the air that has touched the heat transfer tubes 41 and the fins 42 is promoted, and the moisture contained in the air is solidified, and frost is easily formed. Is larger than the outlet side of the evaporator 4. Therefore, the influence on the refrigerating performance of the refrigerating apparatus 200 due to the localized frost 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 mixed refrigerant. The refrigerant pressure difference between the inlet and the outlet of the evaporator 4 in the refrigeration apparatus 200 is compared with the pressure difference of the refrigerant at the inlet and the outlet of the evaporator 4 when the temperature of the refrigerant flowing through the evaporator 4 is made uniform. In the same manner, the refrigerant flowing through the evaporator 4 may be provided with a pipe pressure loss.

  As described above, as in the second embodiment, the refrigerant circulating in the refrigeration apparatus 200 contains 36 wt% of R32, 30 wt% of R125, 14 wt% of R134a, 14 wt% of R1234yf, and 6 wt% of carbon dioxide. Even when an azeotropic mixed refrigerant is used, the temperature of the refrigerant in the evaporator 4 is made substantially uniform by configuring the pipe so that the pipe pressure loss in the evaporator 4 becomes almost the same as the temperature gradient of the refrigerant. In this case, it is possible to prevent the heat exchange performance from deteriorating due to uneven frost. In addition, by using the non-azeotropic mixed refrigerant according to the second embodiment, the refrigeration apparatus 200 can reduce the influence on the global environment and can simultaneously improve safety and refrigeration performance.

In addition, the composition of each refrigerant constituting the non-azeotropic mixed refrigerant of Embodiment 2 may be a refrigerant having a composition ratio of each refrigerant which is different within a range of less than ± 3 wt%. That is, the condition that the ratio X _R32 (wt%) of _R32 is 33 <X _R32 <39, the condition that the ratio X _R125 (wt%) of _R125 is 27 <X _R125 <33, and the ratio X _R134a ( and conditions are wt%) is _{11 <X R134a} <17, the proportion of _{R1234yf X R1234yf (wt%) 11} <X R1234yf < and conditions is 17, the proportion of carbon dioxide _X CO2 (wt%) is _{3 <X R125} <a condition which is _9, and conditions the sum of the _{X R32} and _{X R125} and _{X R134a} and _{X R1234yf} and _{X of co2} is 100 (wt%), may be any refrigerant that satisfies all.

  Note that the refrigerant circulating in the refrigeration apparatus 200 of Embodiment 2 may be any one of R448A, R449A, and R407F. R448A, R449A, and R407F are non-azeotropic refrigerant mixtures, and in any case, the pipe pressure loss applied to the refrigerant in the evaporator 4 is configured to be substantially the same as the temperature gradient of the refrigerant. It is possible to make the temperature of the refrigerant in the evaporator 4 substantially uniform, and to prevent the heat exchange performance from being deteriorated due to the defrosting of the evaporator 4.

  Note that the physical properties of the non-azeotropic mixed refrigerant according to Embodiment 2 are similar to those of R410A, and even if R410A is put into refrigeration apparatus 200 according to Embodiment 2, operation can be performed without any problem. . However, R410A is a pseudo-azeotropic mixed refrigerant and has almost no temperature gradient. That is, in FIG. 5, the isotherm of the refrigerant is substantially horizontal like the isotherm of the pseudo-azeotropic mixed refrigerant shown in the evaporator 4. Therefore, when R410A is used for the refrigeration apparatus 200 including the evaporator 4 designed for the non-azeotropic mixed refrigerant according to Embodiment 2, the outlet side due to pressure loss when the refrigerant flows in the evaporator 4 It is conceivable that the pressure of the refrigeration apparatus 200 decreases and the refrigeration capacity of the refrigeration apparatus 200 decreases.

  Therefore, when R410A is used for the refrigerating apparatus 200, the evaporator 4 needs to be configured so that the pipe pressure loss of the heat transfer tube 41 is reduced in order to reduce the performance degradation when the R410A is used. For example, when the non-azeotropic mixed refrigerant according to Embodiment 2 is used, since the difference in refrigerant saturation temperature between the inlet and the outlet of the evaporator 4 in the low temperature region is approximately 5 ° C., the evaporator 4 corresponds to 5 ° C. Pressure loss to the refrigerant. However, when R410A is used, the pressure loss in the evaporator 4 is set to a temperature gradient of the non-azeotropic refrigerant mixture, which is equivalent to a pressure loss of less than 5 ° C.

  For example, the heat transfer tube 41 of the evaporator 4 according to Embodiment 2 is configured so that the pressure loss is reduced with respect to the refrigerant flowing in the tube at a normal flow rate, and the refrigeration apparatus 200 uses R410A. At this time, the operation is performed such that the refrigerant flows at a normal flow rate. Then, since the refrigerant flowing in the evaporator 4 flows so that the pressure loss becomes less than 5 ° C. in the temperature gradient of the non-azeotropic refrigerant mixture, the refrigerant evaporates at almost the same pressure as indicated by the dotted line C in FIG. It flows out of the vessel 4. On the other hand, when the non-azeotropic mixed refrigerant according to the second embodiment is used, the heat transfer tube 41 is configured so that the refrigerant flows at a higher flow rate than usual and that the pressure loss of the refrigerant in the pipe increases at a high flow rate. I just need. When the flow velocity of the refrigerant is increased, the pressure loss of the refrigerant in the evaporator 4 increases, and as shown by a solid line D in FIG. There is no difference in temperature between the refrigerant at the inlet and the outlet and no frost. By the means as described above, the refrigeration apparatus 200 can use both the non-azeotropic mixed refrigerant and the pseudo-azeotropic mixed refrigerant without lowering the refrigeration capacity.

  FIG. 6 is a schematic diagram illustrating a configuration of an evaporator 24 of a 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 give a predetermined pressure loss to the refrigerant flowing in the tube. When the R410A is used, the refrigeration apparatus 200 is configured such that the number of refrigerant flow paths flowing through the evaporator 24, that is, the number of paths is five as shown in FIG. On the other hand, when the non-azeotropic mixed refrigerant according to Embodiment 2 is used, the refrigeration apparatus 200 switches the flow path of the refrigerant flowing through the evaporator 24, and the refrigerant has one pass number as shown in FIG. Through the evaporator 24. In the evaporator 24 shown in FIG. 6, each heat transfer tube 41 is connected by a U-shaped tube 45 at the end of the evaporator 24, and the flow path is elongated by the refrigerant flowing back at both ends of the evaporator 24. . Since the flow path of the refrigerant is long, the pressure of the refrigerant passing through the evaporator 24 is reduced due to the loss of the heat transfer tube 41. With the above configuration, when a pseudo-azeotropic mixed refrigerant such as R410A is used for the refrigeration apparatus 200, the pressure loss of the refrigerant is reduced by shortening the flow path. When a non-azeotropic mixed refrigerant is used for the refrigeration apparatus 200, the pressure loss of the refrigerant can be increased by lengthening the flow path. By the above means, the refrigeration apparatus 200 can use both the pseudo-azeotropic mixed refrigerant and the non-azeotropic mixed refrigerant without lowering the refrigeration capacity.

(9) According to the refrigeration apparatus 200 according to Embodiment 2, the refrigerant is a mixed refrigerant of R32, R125, R134a, R1234yf, and carbon dioxide, and the ratio XR32 (wt%) of _R32 is , 33 wt% <X _R32 <39 wt%, the condition that R125 ratio X _R125 (wt%) is 27 wt% <X _R125 <33 wt%, and the R134a ratio X _R134a (wt%) is 11 wt % <X _R134a <17 wt%, the condition that R1234yf's ratio X _R1234yf (wt%) is 11 wt% <X _R1234yf <17 wt%, and the ratio of carbon dioxide X _CO2 (wt%) is 3 wt% _<X CO2 <and conditions is _{9wt%, X R32, X R125} , X R134a, X R1234yf, and _{X CO} Sum _{X total} of, all satisfied the conditions is 100 wt%, a.
With such a configuration, the refrigeration apparatus 200 has little effect on the global environment and can simultaneously improve safety and refrigeration performance.

(10) According to the refrigeration apparatus 200 according to Embodiment 2, the refrigerant is R448A, R449A, or R407F.
(11) According to the refrigeration apparatus 200 according to Embodiment 2, the refrigeration cycle includes at least one of R32, R125, R134a, R1234yf, and a refrigerant mixture of carbon dioxide, R448A, R449A, and R407F. And R410A can be shared. With such a configuration, the refrigeration apparatus 200 can be used, for example, for low-temperature equipment and other various uses.

(12) According to the operation method of the refrigeration apparatus 200 according to Embodiment 2, the pressure in the pipe between the inlet and the outlet is changed by changing the length of the pipe of the heat transfer tube 41 of the evaporator 24 through which the refrigerant passes. And a pipeline length changing step of changing the difference between the two.
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, since a plurality of types of refrigerants can be used for the refrigeration apparatus 200, the refrigeration apparatus 200 can be used for various applications.

(13) According to the operating method of the refrigeration apparatus 200 according to the second embodiment, the pipeline length changing step changes the number of passes of the refrigerant passing through the evaporator 24 and changes the pressure in the pipeline between the inlet and the outlet. To change the difference.
With such a configuration, the refrigeration apparatus 200 can change the pressure loss applied to the refrigerant flowing in the evaporator 24 even in the evaporator 24 including the normal heat transfer tubes 41. Further, by using the means described in (6) to (8) together, the range of pressure loss applied to the refrigerant flowing in the evaporator 24 is widened, and the pressure difference between the inlet and the outlet of the evaporator 24 is reduced. It is also possible to make appropriate adjustments.

  REFERENCE SIGNS LIST 1 compressor, 2 condenser, 3 decompression device, 4 evaporator, 5 refrigerant pipe, 6 condenser blower, 7 evaporator blower, 20 pressure sensor, 24 evaporator, 30 temperature sensor, 41 heat transfer tube, 42 fin, 43 Refrigerant distributor, 44 header, 45 U-tube, 50 cooler, 60 control unit, 100 refrigeration unit, 200 refrigeration unit, dotted line A, dotted line B, dotted line C, solid line D.

The refrigeration apparatus according to the present invention includes a refrigeration cycle in which a compressor, a condenser, a decompression device, and an evaporator are connected by a refrigerant pipe and a refrigerant circulates inside the refrigerant, and the refrigerant has a ratio of _R32 X _R32 (wt%) _{is, 33 wt%} <and conditions are X R32 <39wt%, the proportion _X R125 in R125 (wt%) _{is, 27wt%} <X R125 <and conditions is 33 wt%, the percentage of R134a _{X R134a} (wt _{percent), 11 wt% <and} conditions are X R134a <17 wt%, the proportion of R1234yf _{X R1234yf} (wt%) _{is, 11wt% <X} R1234yf _<and conditions is 17 wt%, the proportion of carbon dioxide _X CO2 (wt% ) is _a condition which is a _{3wt% <X CO2 <9wt%} , X R32, X R125, X R134a, X R1234yf, and _{X CO} Total _{X total} is a mixed refrigerant, or R410A which satisfies all the conditions is 100 wt%, and the evaporator is matched to the temperature gradient of the isotherm of the gas-liquid two phase region of the non-azeotropic mixed refrigerant, evaporated In the process, the pressure in the pipeline is reduced along the direction in which the refrigerant flows, and the number of passes of the refrigerant passing through the evaporator is freely changeable so that the refrigeration cycle supports both the mixed refrigerant and R410A. When the refrigerant is the mixed refrigerant, the number of passes of the refrigerant is reduced as compared with the case where the refrigerant is R410A .

Claims (13)

A compressor, a condenser, a decompression device, and an evaporator are connected by a refrigerant pipe, and a refrigeration cycle in which the refrigerant circulates is provided,
The refrigerant is
A non-azeotropic refrigerant mixture of multiple types,
The evaporator is
A refrigerating apparatus, wherein a pressure in a pipe in an evaporation process is reduced along a flowing direction of the refrigerant in accordance with a temperature gradient of an isotherm in a gas-liquid two-phase region of the non-azeotropic mixed refrigerant. The heat transfer tube of the evaporator,
The refrigeration apparatus according to claim 1, wherein a cross-sectional area increases along a direction in which the refrigerant flows. The heat transfer tube of the evaporator,
The refrigeration apparatus according to claim 1, further comprising a resistance unit that serves as a resistance to the flow of the refrigerant in a pipe.   The refrigeration apparatus according to any one of claims 1 to 3, wherein the pressure in the pipeline in the evaporation process is reduced by controlling a flow rate of the refrigerant passing through the evaporator. The refrigerant is
R32, R125, R134a, R1234yf, and a mixed refrigerant of carbon dioxide,
The ratio X _R32 (wt%) of _R32 is
A condition that 33 wt% <X _R32 <39 wt%;
The ratio X _R125 (wt%) of _R125 is
A condition that 27 wt% <X _R125 <33 wt%;
The ratio X _R134a (wt%) of _R134a is
A condition that 11 wt% < _XR134a <17 wt%;
The ratio X _R1234yf (wt%) of _R1234yf is
11 wt% <X _R1234yf <17 wt%;
The ratio of carbon dioxide X _CO2 (wt%)
3 wt% <X _CO2 <9 wt%;
The total X _{total of} X _R32 , X _R125 , X _R134a , X _R1234yf , and X _CO2 is:
The refrigeration apparatus according to any one of claims 1 to 4, which satisfies all conditions of 100 wt%. The refrigerant is
The refrigeration apparatus according to any one of claims 1 to 4, wherein the refrigeration apparatus is R448A, R449A, or R407F. The refrigeration cycle includes:
A mixed refrigerant of R32, R125, R134a, R1234yf, and carbon dioxide, at least one of R448A, R449A, and R407F, and both R410A and R410A. 7. The refrigeration apparatus according to 6. A compressor, a condenser, a decompression device, and an evaporator are connected by a refrigerant pipe, and a refrigeration cycle in which the refrigerant circulates is provided,
The refrigerant is
In a refrigeration apparatus, which is a non-azeotropic mixed refrigerant obtained by mixing a plurality of types,
A detection step of detecting an in-pipe pressure at an inlet of the evaporator and an outlet of the evaporator,
A pressure adjusting step of adjusting a difference between the pressures in the pipeline between the inlet portion and the outlet portion to a temperature gradient of an isotherm in a gas-liquid two-phase region of the refrigerant.   9. A pipe length changing step of changing a pipe pressure difference between the inlet and the outlet by changing a pipe length of a heat transfer tube of the evaporator through which the refrigerant passes. The method for operating a refrigeration apparatus according to claim 1. The pressure adjusting step includes:
The refrigerating apparatus according to claim 8 or 9, further comprising a flow rate changing step of changing a flow rate of the refrigerant flowing through the evaporator to change a difference in pressure in the pipeline between the inlet and the outlet. how to drive. The flow rate changing step,
The operating method of the refrigeration apparatus according to claim 10, wherein the flow rate of the refrigerant flowing through the evaporator is changed by changing an operating frequency of the compressor. The flow rate changing step,
The method according to claim 10, wherein the flow rate of the refrigerant flowing through the evaporator is changed by changing an opening of a flow control valve provided at the inlet of the evaporator. The pipe length changing step includes:
The operating method of the refrigeration apparatus according to claim 9, wherein the number of passes of the refrigerant passing through the evaporator is changed to change a difference in pressure in the pipeline between the inlet and the outlet.

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