WO2002077543A1

WO2002077543A1 - Freezing system using non-azeotropic type mixed refrigerant

Info

Publication number: WO2002077543A1
Application number: PCT/JP2001/002440
Authority: WO
Inventors: Toshio Seino
Original assignee: Dairei Co.,Ltd.
Priority date: 1999-09-30
Filing date: 2001-03-27
Publication date: 2002-10-03
Also published as: JP2001099498A

Abstract

A freezing machine system using a non-azeotropic type mixed refrigerant containing two or more refrigerant components, wherein by means of low temperature working fluid which is present in a circulation passageway extending through a compressor (1), a condenser (2), a throttle valve (4) and an evaporator (5) to return to the compressor and which returns from the evaporator to the compressor, working fluid present in a region extending from the condenser to the throttle valve is cooled by a heat exchanger (10), thereby lowering the temperature and vapor pressure of the refrigerant, thereby further lowering the temperature and pressure in the compression and condensation steps, thereby lowering the freezing machine system working pressure, promoting the condensation and liquefaction of the high vapor pressure, low boiling refrigerant components. Therefore, it is possible to lower the working pressure for the freezing machine system and to easily realize cryogenic temperatures using a high critical pressure, low critical temperature refrigerant as a mixed refrigerant component.

Description

Specification

Refrigeration system using non-azeotropic mixed refrigerant

The present invention relates to a refrigeration system such as a refrigerator unit. Background art

CFCs have been widely used as refrigerants for freezers and refrigerators because of their excellent properties.However, CFCs containing chlorine destroy the ozone layer in the upper atmosphere, and many CFCs are greenhouse gases. These fluorocarbons are becoming internationally regulated and unusable because of their influence on dani. In response, attempts have been made to use so-called alternative chlorofluorocarbons that do not cause depletion of the ozone layer and are less affected by the greenhouse effect, and the development of new hydrocarbon-based refrigerants to replace these chlorofluorocarbon-based refrigerants has been promoted. ing.

However, when used as a refrigerant, it must be chemically stable and non-toxic, have good compatibility with lubricating oil, and have a sufficiently low standard boiling point in relation to the intended refrigeration temperature. It is required to have a high critical temperature because it operates in a room temperature environment. Generally, the ratio of the standard boiling point to the critical temperature on the absolute temperature scale (to the critical boiling point value) is about 0.6 to 0.7. Therefore, it is difficult to obtain a refrigerant that can operate at room temperature and significantly lower the freezer interior, especially for ultra-low-temperature refrigerators that maintain an interior temperature of 150 ° C or less. In addition to the low critical temperature, the pressure required for liquefaction is high, so it is difficult to construct a new refrigeration system with practical use.

For this reason, attempts have been made to adjust the properties such as the boiling point of a mixed refrigerant composed of two or more components by selecting the mixed composition. In this case, the composition of the non-azeotropic refrigerant mixture and the type of each component substance can be selected widely, but the phase change characteristics of the non-azeotropic refrigerant mixture are constant at a dew point curve and a boiling point curve separated from each other. Liquefaction under the conditions of The start temperature and the liquefaction end temperature or the gasification start temperature and the vaporization end temperature are different.

Therefore, if the composition of each gas-liquid phase changes in the condenser under constant pressure and the cooling capacity is increased by increasing the refrigerant charge, etc., the refrigerating machine system will remain with wet refrigerant gas remaining from the evaporator. Circulation will reduce the efficiency of the refrigerator system.

In addition, the cryogenic refrigerator system uses a non-azeotropic refrigerant mixture composed of two or more components, and the liquefaction of components with a low boiling point and a low critical temperature is necessary for the ability of the condenser to operate at room temperature. Because of the difficulty, a multi-component system that condenses in multiple stages for each component refrigerant is used.

Fig. 3 shows an example of this, in which a mixed refrigerant consisting of three types of refrigerants with different boiling points was used, and the mixed refrigerant compressed by one compressor (compressor) 1 was released through a condenser 2 Later, the first refrigerant having a higher boiling point is used for condensing a second refrigerant having a lower boiling point, and the second refrigerant is used for condensing a refrigerant having a lower boiling point which achieves a desired cooling temperature. In the first and second refrigerants, the first and second refrigerants are separated by gas-liquid separators 6 and 8, respectively, are passed through a throttle valve 4, and are cooled by heat exchange 7 and 9. To condense. The third refrigerant having the lowest boiling point is vaporized by the evaporator 5 via the throttle valve 4 and cools the inside of the cooling tank (freezer) 50 to a desired temperature.

However, such a refrigerator system has a complicated structure and unavoidable large-scale equipment. Therefore, the production cost is increased, the power and maintenance are difficult, and the maintenance cost is increased. It also has restrictions in the.

Therefore, it is desired to easily realize a high-efficiency refrigeration system, particularly a cryogenic refrigerator system, with a simple system configuration using a non-azeotropic mixed refrigerant. Disclosure of the invention

The present invention relates to a refrigeration system using a non-azeotropic mixed refrigerant containing two or more refrigerant components, wherein evaporation in a circulation path returning to the compressor via a compressor, a condenser, a throttle valve, and an evaporator. This is a refrigeration system characterized by cooling the working fluid from the condenser to the throttle valve with a low-temperature working fluid that returns from the compressor to the compressor to promote liquefaction of low-boiling components.

In addition, a low-temperature working fluid that cools the working fluid between the evaporator and the throttle valve, The cooling ability is effectively improved by making the liquid high boiling point component wet, and the working fluid from the condenser to the throttle valve is cooled by the low-temperature working fluid returning from the evaporator to the compressor. By cooling, the discharge pressure of the working fluid from the compressor can be reduced.

In addition, since the critical temperature of at least one component of the non-azeotropic mixed refrigerant is substantially equal to or lower than room temperature, it is possible to easily realize a refrigerator system capable of achieving an extremely low temperature. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a configuration diagram schematically showing a refrigerator system of the present invention, FIG. 2 is a comparative example showing a prior art of the present invention, and FIG. Three-way system) Indicates a refrigerator system. BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a conceptual diagram of one embodiment of a refrigerator system of the present invention, in which a working fluid composed of a non-azeotropic mixed refrigerant adiabatically compressed by a compressor 1 radiates heat in a condenser 2. The liquid is cooled to approximately room temperature and liquefied, passed through the drier 3 and sent to the evaporator 5 through the throttle valve 4 to expand and absorb, absorb the heat in the freezer, and return to the compressor again. During normal operation, the working fluid returning to the machine is at a low temperature, which is approximately the same as the internal temperature.Therefore, a heat exchanger 10 is installed in the path between the dryer and the throttle valve shown in the figure to mix before entering the throttle valve 4. The refrigerant can be effectively cooled to lower the temperature to a temperature equal to or lower than room temperature.

Such a refrigerator system having a heat exchanger between the compressor and the evaporator has been often used in the past (for example, “Refrigeration and Air Conditioning” by Haruo Yamada, Yokendo Co., Ltd.) In this case, the seventh edition was issued on June 10, 1965, p. 77) .In this way, the gas coming from the evaporator was heated by the liquid high-temperature refrigerant and entered the compressor, while the liquid was deflected. The high-temperature refrigerant is supercooled well below the saturation temperature and enters the throttle valve without any residual gas mixed therein, and both the compressor and the evaporator can operate smoothly. However, these are performed in a single-component refrigerant, and are nothing more than the use of sensible heat to smooth the operation cycle of such a refrigerator.

However, in the non-azeotropic mixed refrigerant composed of two or more components as in the present invention, when the cooling is performed effectively in this manner, the boiling point curve and the dew point curve are separated as described above. The cooling in the step shifts the composition of the liquid phase toward the low-boiling-point refrigerant side, and the decrease in the vapor pressure due to the cooling suppresses the temperature rise during adiabatic compression, thereby further promoting this effect. On the other hand, the boiling point differs depending on the composition of the liquid phase, and the boiling point of the mixed refrigerant on the lower boiling point side is lower. Thus, the refrigerant which has shifted to the lower boiling point side composition has the maximum refrigeration capacity in the evaporation process. Can be demonstrated. Further, the refrigerant thus cooled in the condensing process has a reduced vapor pressure in accordance with the temperature thereof, so that the condensing process proceeds quickly at a lower pressure, and the operation of the entire refrigerator system is performed at a relatively low pressure. In «It is possible.

That is, conventionally, when the pressure in the condensation process is increased to liquefy the low-boiling-point refrigerant side composition, the discharge pressure of the compressor can be reduced, and the load can be reduced.

From this fact, it is possible to use a mixed refrigerant having a higher vapor pressure and a refrigerant component by using a compressor having the same capacity, and it is possible to improve the capacity of the refrigerator. In addition, the cooling of the mixed refrigerant by the heat exchange lowers the boiling point of the mixed refrigerant and promotes the condensation of the low-temperature component at the critical temperature. This makes it possible to use a refrigerant with a low critical temperature, which could not be directly condensed under the operating environment of the above. Combining a refrigerant with a higher boiling point and a critical temperature with respect to such a refrigerant having a lower boiling point, which can be easily condensed using a condenser operating at room temperature, is composed of two or more refrigerants. By using a mixed refrigerant, it is possible to easily exhibit ultra-low-temperature refrigeration capacity by a single-unit simple-structure refrigerator system using a condenser that operates at room temperature.

In this refrigerating machine system, gas-liquid separation is not performed in the middle of the process compared to the conventional multi-unit system, and the mixed refrigerant in the process of returning to the compressor is extended on the extension of the condensation process immediately before the throttle valve. Cooling and condensing working fluid using latent heat and sensible heat Thus, cooling can be performed very efficiently with a simple configuration. Since the cycle immediately before the throttle valve is an extension of the condensing process, it is promptly reflected in the pressure drop in the compression process, which can suppress the temperature rise in the thermal compression and the latent refrigerant of the mixed refrigerant in the return process. The feedback function works effectively in combination with increasing the cooling capacity using heat and sensible heat, so that a stable state can be maintained during steady-state operation, as well as easy start-up and quick steady state at the start of operation. It is possible to go into operation. Such a feature of the refrigerator system of the present invention is that the temperature of the mixed refrigerant that cools the working fluid in front of the throttle valve and returns to the compressor is increased immediately before the compressor by heat exchange. Nevertheless, it can be seen that both the temperature and pressure at the compressor outlet are decreasing. That is, since the discharge pressure of the compressor is significantly reduced, the temperature rise due to adiabatic compression is suppressed, and such a process is immediately fed back to the refrigeration cycle.

In addition, the mixed refrigerant before entering the compressor is heated by heat exchange to increase the specific volume.The remaining multi-phase liquid phase of the high-boiling components is also absorbed and does not hinder the operation of the compressor. State.

In order to confirm the operation of such a refrigeration system of the present invention, an experiment was conducted in comparison with a conventional refrigeration system without a heat exchanger using return refrigerant before returning to the compressor shown in FIG. Was done.

It is not necessary to analyze the detailed physical properties of the mixed refrigerant for experiments to grasp these characteristics, so it is necessary to confirm the actual operation of the refrigerant, and use a commercially available UN ID AD product for the refrigerator. 1 4 (refrigerator model name: GL 9 9 EJ) used, butane as a mixed refrigerant _{_{(C 4 H W) 5 5}} %, R - 116 (C 6 F 6) using 4 5% of the mixed refrigerant, Temperature and pressure values of each part of the refrigerator system A to G were measured while changing the filling amount to the refrigerator in the range of 200 to 2337 g.

For heat exchange 10, a commercially available double-walled copper pipe was 3 m long, and the outer pipe was returned and used as a refrigerant flow path.

Table 1 shows the pressure and temperature during these actual operation. Table 1: Temperature and pressure of each part of the refrigerator system (butane + R-116)

Example: Discharge pressure and suction pressure are absolute values measured before and after the compressor.

The measurement points of the numerical values in the table are as follows.

Discharge pressure (A), Discharge temperature (A), Suction pressure (B), Return temperature (B), Heat exchange inlet temperature (C), Heat exchange outlet temperature (E), Evaporator inlet temperature (G) Table 1 As shown in the figure, the return refrigerant used for cooling the refrigerant immediately before the throttle valve absorbs the heat of the refrigerant from the condenser and, as shown in the return temperature column, immediately before the compressor, has a 13.2-- Although the temperature rises by 9.4 ° C, the temperature after it is adiabatically compressed by the compressor decreases by 7.2 to 4.2 ° C. At the same time, the discharge pressure drops significantly with the heat exchanger outlet temperature, and the drop in refrigerant temperature immediately before the throttle valve lowers the vapor pressure of the mixed refrigerant, causing the discharge pressure to drop and the discharge temperature to drop. It can be seen that there is a decrease in

This effect has been achieved by increasing the refrigerant charge from 200 g to 237 g.This increase in the refrigerant charge directly enhances the cooling effect of the refrigerant immediately before the throttle valve. However, it can be seen that the temperature at the outlet of the heat exchange m¾ is lowered. Regarding the attained temperature, the slope of the boiling point curve becomes gentler as the condensing temperature decreases, so the difference in the attained temperature becomes smaller near the boiling point of the composition of the filling gas. However, even a predetermined low temperature is effectively achieved.

Therefore, to see the relationship between the refrigerant charge and their cooling action, Table 2 shows the relationship between the refrigerant temperature and the charge at the heat inlet and outlet. Table 2: Relationship between refrigerant charge, discharge pressure and return refrigerant temperature

Measuring point: Return refrigerant heat exchange Inlet temperature: F, Return refrigerant heat exchange «Outlet temperature: D In other words, if the refrigerant charge increases, the evaporator inlet temperature does not decrease much because it is already an appropriate charge for refrigeration function However, the temperature in the freezer does not drop, but the temperature of the refrigerant at the outlet of the heat exchanger drops significantly.

Here, butane having a high boiling point circulates without being completely evaporated, and the wet gas containing the irreversible benzene reaches the heat exchanger, and the refrigerant from the compressor in the heat exchanger is removed. By vaporizing through heat exchange, it greatly contributes to cooling of the refrigerant. This state often occurs in a refrigerator system that normally uses a non-azeotropic mixed refrigerant, and is in a state called frost. In such a situation, not only does the refrigerator's refrigeration capacity not contribute to the refrigeration capacity, but also the refrigeration unit's operating efficiency decreases, and frost forms around the piping from the evaporator to the compressor, causing damage to the refrigeration equipment. Also.

The present invention not only eliminates this frosting phenomenon, but also significantly reduces the discharge pressure by utilizing the cooling capacity of the return refrigerant component that does not contribute to the refrigeration capacity, thereby reducing the load. Can be improved.

Table 3 shows the physical properties of R-116, butane.

As shown in the table, since the boiling point of butane is 0.5 ° C, the temperature of the refrigerant at -24.6 ° C is added to the latent heat of butane in the case of the above filling amount of 237 g. It can be seen that the large amount is due to the sensible heat of the refrigerant. Table 3 Physical properties of butane and R-6

Chemical formula Boiling point Critical temperature Gas pressure

(.C, l atm) (.c) (atm, 20 ° C) Butane-0.5 1 5 3.2.2.1

R— 1 1 6 CF 3 CF 3-7 8.2 19.8 5 3 0.4 Since the butane-R116 mixed refrigerant has a relatively low vapor pressure of R-116, the actual operation of the refrigerator system can be performed without using the system of the present invention as described above. Because the cooling system effectively reduces the temperature and pressure during the condensation process, high pressure is required during the condensation process under normal room temperature environment, and the refrigerant that cannot be liquefied with the capacity of the conventional refrigerator due to the low critical temperature is used. It can be used to achieve very low temperatures.

Therefore, instead of the butane-Rl 16 mixed refrigerant, the butane-R23 mixed refrigerant was replaced with a refrigerator system model F-14 (manufactured by UN I DAD).

GL99E J) refrigerator and a commercially available copper double tube heat exchanger to freeze a mixed refrigerant of 72% butane (C ₄ H ₁₀ ) and 28% R-23 (CHF ₃ ) as a mixed refrigerant

The temperature and pressure at each part A to H of the refrigerator system were measured while changing the filling amount of the refrigerator in the range of 140 to 270 g.

¾ ~ "4 and 5 show the data and physical properties of butane and R-23. Table 4: Temperature and pressure of each part of refrigerator system (butane + R-23) Discharge pressure Suction pressure Heat exchange Heat exchange Crane Returned refrigerant Returned refrigerant Storage temperature Filling amount

(kg / cm ² ) (cmHg) Inlet temperature Outlet temperature Heat-exchange crane Heat-exchange crane (.C) (g)

(.C) (° C) Inlet Outlet

(° C) (° C)

15.5 20 30.4 24.4 17.9 30.2 -27 140

14.5 5 29.8-0.8 -17.0 29.2 -50 150 11.0 0 29.7 -17.5 -26.7 26.8 -69.7 160

10.0 0 29.8 -22 -26.8 19.3-73.5 170

9.5 0 30.2 -24 1 30.9 -0.9 -74.2 180

9.5 0.1 30.3-23.4 -30.9 -1.9 -73.4 190

9.5 0.2 31.3-23.3-30.2 -4.8 -72.0 200

10.0 0.3 32.9 -22.3 -29.2 -2.6 -70.1 210 Bright 10.5 0.5 34.6 -21.4 -28.9 -0.4 -67.9 220

11.0 0.6 35.0 -21.6 -28.9 1.7 -66.5 230

11.25 0.6 35.3 -22.5 -29.5 2.8 -66.0 240

12.0 0.7 35.8 -24.2 -30.7 3.4 -65.5 250

12.25 0.8 35.6 -24.7 -30.7 3.5 -65.0 260

12.5 0.8 35.3 -25.4 -31.4 3.7 -64.4 270 Example: Discharge pressure and suction pressure are absolute values measured before and after the compressor.

Measurement points: Return refrigerant heat exchanger inlet (F), return refrigerant heat exchanger outlet (D), chamber temperature (H) Table 5: Physical properties of butane, R-23

As shown in Table 5, the boiling point of R23 is lower than that of R-116, and the critical temperature is high. However, the vapor pressure is extremely high, but the temperature and pressure of the condensing process rise even for these mixed refrigerants. Therefore, it is difficult to use with the capacity of the conventional refrigerator.

In the refrigeration system of the present invention, as shown in Table 4 above, the temperature of the return refrigerant in the heat exchange significantly decreases as the refrigerant charge increases, and in conjunction with these, the discharge pressure and the heat exchange β outlet It can be seen that the temperature of the refrigerant drops significantly. In this way, the refrigeration capacity of the butane R23-based refrigerant can be maximized. In this case, as in the case described above, there is an almost constant appropriate range in the cooling capacity of the returned refrigerant from the filling amount, and the refrigeration capacity does not improve even if the filling amount of the refrigerant is further increased.

In the above example, a two-component mixed refrigerant was charged into a commercially available refrigerator, and its operation and effect were confirmed by actual operation.These effects were obtained by combining non-azeotropic mixed refrigerants and these refrigerants. It is clear that the same operation and effect are exhibited when the number of types of refrigerants to be combined is two or more.

That is, the principle of the present invention is that, as seen from the boiling point curve of the gas-liquid equilibrium curve of the mixed refrigerant, the composition of the liquid phase shifts to the low boiling point component side as the temperature decreases in the condensation process of the non-azeotropic mixed refrigerant. In addition, it utilizes the fact that the boiling point of the liquid phase also decreases, thereby making it possible to further lower the refrigeration temperature and significantly reduce the required compression pressure to significantly improve the refrigeration capacity. be able to. In addition, these effects are obtained by using a refrigerant with a low boiling point or a high vapor pressure that cannot be liquefied at room temperature as a mixed refrigerant. The type and number of these refrigerants are selected based on the relationship between the boiling point, critical temperature and critical pressure according to the target refrigerator maintenance temperature and the capacity of the refrigerator compressor, etc. And can be appropriately combined.

In addition, the configuration of the refrigeration system is basically based on the above embodiment, and for a lower temperature use, a heat exchange structure with a larger capacity may be used to promote the condensation process of the low-temperature boiling point refrigerant in the heat exchanger. However, in order to achieve a compact configuration, a spiral tube or a laminated structure may be used instead of the double tube. Industrial availability

As described above, the refrigeration system according to the present invention can achieve an ultra-low temperature efficiently with a simple configuration, and can be widely used in various fields such as preservation of biological tissue for medical use. it can.

Claims

Sought

In a refrigeration system using a non-azeotropic mixed refrigerant containing 1.2 or more refrigerant components, the evaporator power in the circulation path returning to the compressor via the compressor, condenser, throttle valve, and evaporator ^ compression The operation from the condenser to the throttle valve by the cold working fluid returning to the machine

A refrigeration system for cooling a fluid to promote liquefaction of low-boiling components.

2. The refrigeration system according to claim 1, wherein the low-temperature working fluid for cooling the working fluid from the evaporator to the throttle valve is in a wet state by a liquid high-boiling component.

3. The discharge pressure of the working fluid from the compressor is reduced by cooling the working fluid from the condenser to the throttle valve with the low-temperature working fluid returning from the evaporator to the compressor. 3. The refrigeration system according to claim 1 or claim 2.

4. The refrigeration system according to claim 1, wherein the critical temperature of at least one component of the non-azeotropic mixed refrigerant is substantially equal to or lower than room temperature.