JPS62248962A - Refrigerator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of industrial application' The present invention relates to a refrigeration system using a compressor, and particularly to a refrigeration system for obtaining extremely low temperatures using a non-azeotropic mixture of multiple types of refrigerants. be.

(Example) Conventional technology Conventionally, mechanical refrigeration equipment used in freezers used in physical and chemical laboratories and the like to preserve biological cells has had a limit of obtaining a low temperature of about -80°C.

Although cryopreservation of cells is achieved at such low temperatures, as time passes, the nuclei of ice crystals within the frozen cells recombine and the size of the ice crystals expands, causing cell destruction. . This is called recrystallization of ice, but it is known that this recrystallization of ice does not occur in an environment lower than -130° C., which is the recrystallization point. That is -130℃
Permanent preservation of cells can be achieved at lower ultra-low temperatures.
There have been high expectations for a refrigeration system that can obtain such ultra-low temperatures.

In this type of refrigeration system, especially one using a compressor, the high temperature gaseous refrigerant discharged from the compressor flows into the condenser and is liquefied by exchanging heat with air or water, and the pressure is adjusted by a pressure reducing device. After that, it flows into an evaporator and is evaporated. At this time, the cooling effect is achieved by absorbing the heat of vaporization from the surroundings, but in a refrigeration system using a single refrigerant, in the case of a normal compressor, -4
The limit is to achieve a minimum temperature of about 0°C.

There is also a so-called dual refrigeration system that uses two independent refrigerant closed circuits, connects them in cascade, and seals a low boiling point refrigerant in the refrigerant closed circuit on the side that achieves the low temperature, thereby achieving a low temperature. However, when using a normal compressor, the temperature is limited to about -80°C.

October 3, 1973 as a solution to these problems.
As in U.S. Pat. No. 3,768,273, a mixed refrigerant of multiple types with different boiling points is used, and the refrigerant with a lower boiling point is successively condensed by evaporating the refrigerant with a higher boiling point in an intermediate heat exchanger. There is also a so-called mixed refrigerant refrigeration system in which the refrigerant with the lowest boiling point is evaporated in the final stage evaporator and a low temperature is obtained using a single compressor.

Further, U.S. Pat. No. 3,733, dated May 22, 1973.
There is also a system, such as No. 845, in which two independent refrigerant closed circuits are connected in cascade, and the refrigerant closed circuit on the low temperature side uses the above-mentioned mixed refrigerant refrigeration system to achieve an extremely low temperature. According to this, it is possible to achieve extremely low temperatures lower than -130°C using a commonly used compressor (for example, about 1.5 HP).

(c) Problems to be Solved by the Invention In such a mixed refrigerant refrigeration system using a refrigerant closed circuit, the final temperature reached is extremely low, below -130°C, as described above, and therefore the external temperature of the cooling device is Because the refrigerant easily evaporates in the final stage pressure reducer due to the intrusion of heat from the evaporator, a sufficient amount of liquid refrigerant cannot be supplied to the evaporator, resulting in insufficient cooling.

In order to prevent this kind of situation, the area near the evaporator of the cooling system is particularly tightly insulated, but there are limits to this, and such insufficient cooling can also be caused by an imbalance in the amount of refrigerant charged. occur.

In other words, if the amount of refrigerant charged is too large, the refrigerant will not be completely evaporated in the evaporator and will return to the intermediate heat exchanger in the final stage as a liquid, causing the intermediate heat exchanger to be at a temperature close to that of the evaporator. It will be cooled down to. When this happens, the refrigerant that passes through and exchanges heat becomes supercooled and begins to evaporate in the final stage pressure reducer due to heat entering from the outside. This obstructs the flow of refrigerant within the pressure reducer, and no refrigerant is supplied to the evaporator, resulting in insufficient cooling.

On the other hand, even if the amount of refrigerant charged is too small, sufficient evaporation of refrigerant in the evaporator will not occur, resulting in insufficient cooling.

The present invention has been made to solve these problems.

(d) Means for solving the problems The present invention will be explained in detail with reference to embodiments. The low-temperature side refrigerant circuit (3) includes an electric compressor (10), a cascade condenser (25A>(25B), an evaporation pipe (47), and first, second, and third intermediate heat exchangers (32), (42), 44).Each intermediate heat exchanger is equipped with an evaporation pipe (47).
They are connected in series so that the return refrigerants of (44), (42), and (32) flow in the order of (44), (42), and (32). The refrigerant circuit (3) is filled with a mixture of multiple types of refrigerants with different boiling points (that is, different evaporation temperatures), and is connected to cascade condensers (25A) (25B>) and intermediate heat exchangers (32) (42) (44). The refrigerant with a high boiling point condensed in multiple pressure reducers (36) (40) (46)
The pressure is reduced at the intermediate heat exchanger (32) and (42) to condense the uncondensed refrigerant, and the R50 refrigerant with the lowest boiling point is evaporated via the final stage pressure reducer (46). It flows into the pipe (47) and is allowed to evaporate, obtaining an extremely low temperature of -150°C.

At this time, the temperature of the refrigerant flowing into the pressure reducer (46), that is, the temperature of the pressure reducer (46) inlet part (P,), and the temperature of the refrigerant after leaving the pressure reducer (46), that is, the temperature of the evaporation pipe (47) inlet part ( P,)
is larger than 10"C, and the difference between the temperature of the cascade condenser (25A) (25B) (-50°C) and the temperature of the evaporation pipe (47) (-150"C) is 100"C.
The value obtained by dividing ℃ by the number of pressure reducers (36) (40) (46) 3
The refrigerant is sealed so that the temperature is lower than 3°C.

(e) When the temperatures of the action point (Pl) and point (P2) are close, the amount of refrigerant charged is too large and a large amount of liquid refrigerant is flowing into the third intermediate heat exchanger (44); When the temperature difference is large, the amount of refrigerant charged is too small and evaporates only in the vicinity of the evaporator vibrator (47) containing 10. Therefore, by setting the temperature between 10℃ and 33℃, the appropriate amount can be sealed. As a result, pulsations in the temperature of the evaporating vibrator (47) and insufficient cooling can be prevented, stable cooling performance can be exhibited, and the refrigeration system (R) can have high reliability and a long life.

(f) Example The invention will now be described in detail with reference to the drawings.

FIG. 1 shows a refrigerant circuit (1) of a refrigeration system (R) of the present invention. The refrigerant circuit (1) is composed of a high temperature side refrigerant circuit (2) as a first closed refrigerant circuit and a low temperature side refrigerant circuit (3) as a second closed refrigerant circuit. (4) is an electric compressor using a one-phase or three-phase AC power source that constitutes a high-temperature side refrigerant circuit (2), and a discharge side pipe (4D) of the electric compressor (4) is connected to an auxiliary condenser (5), The auxiliary condenser (5) was further connected to a sheath prevention vibe (6) that heated the opening edge of the freezer storage chamber, which will be described in detail later, and then to an oil cooler (7) of the electric compressor (4). After that, it is connected to the condenser (8). (9) is a blower for cooling the condenser (8). The refrigerant pipe that exits the condenser (8) passes through the dryer (12), and then is connected to the pressure reducer. (13) The first evaporator (
14A) and the second evaporator (14B) to the accumulator (15), the electric compressor (1o) is connected to the electric compressor ( 4) is connected to the suction side piping (4S). The first evaporator (14A) and the second evaporator (14B) are connected in series, and together constitute the evaporator of the high temperature side refrigerant circuit (2).

The high temperature side refrigerant circuit (2) is filled with refrigerants R502 and R12 (dichlorodifluoromethane) having different boiling points, and their composition is, for example, 88.0% by weight of R502 and 12% by weight of R12.
．． It is 0% by weight. The high temperature gaseous refrigerant discharged from the electric compressor (4) is passed through the auxiliary condenser (5) and the sheathed prevention pipe (
6) After condensing and liquefying heat in the oil cooler (7) and condenser (8), the moisture contained in the dryer (12) is removed, and the pressure is reduced in the pressure reducer (13) and the first and second 2
The refrigerant R5 flows into the evaporator (14A) (14B>) one after another.
02 is evaporated, the heat of vaporization is absorbed from the surroundings, and each evaporator (1
4A) (14B> is cooled and returned to the electric compressor (4) via the oil cooler (11) of the electric compressor (1o) of the low temperature side refrigerant circuit (3) from the accumulator (15) as a refrigerant liquid reservoir. take action.

At this time, the capacity of the electric compressor (4) is, for example, 1.5 HP, and the final temperature reached by each evaporator (14A) (14B>) during operation is -50°C. R
12 does not evaporate in each evaporator (14A) (14B>) and remains in a liquid state, so it hardly contributes to cooling, but it is completely absorbed by the lubricating oil of the electric compressor (4) and the dryer (12). It functions to return the mixed water that was not present to the electric compressor (4) in a state in which it is dissolved. That is, R12
The refrigerant is normally formed at the lower end of the pipe that exits the accumulator (15) (inserted into the accumulator (15) from above, bent at the lower end, and the open end facing above the refrigerant liquid level). The oil comes out from the accumulator (15) through the oil return hole and flows into the oil cooler (11) of the low-temperature side refrigerant circuit (3) in a liquid state containing the aforementioned lubricating oil and the like. Here, R12 evaporates due to the high temperature of the electric compressor (10), which causes the electric compressor (10) to evaporate.
10) Prevents seizure and deterioration of lubricating oil. That is, refrigerant R
12 is an electric compressor (
4) and the function of cooling the electric compressor (10) of the low temperature side refrigerant circuit (3).

The discharge side piping (IOD) of the electric compressor (10) constituting the low temperature side refrigerant circuit (3) is connected to the auxiliary condenser (17) and then to the oil separator (18). Oil separator (18)
The oil return pipe (19) returns to the electric compressor (10) and the pipe connects to the dryer (20).
) is connected to the branching three-way pipe (21). Three-way tube (21
) One of the pipes coming out of the low-temperature side refrigerant circuit (3) is wound around the second suction side heat exchanger (22) for heat exchange and then inserted into the first evaporator (14A). It can be connected to the first condensing pipe (23A) as a side pipe. Three-way tube (21
) is similarly wound around the first suction side heat exchanger (24) of the low temperature side refrigerant circuit (3) for heat exchange, and then inserted into the second evaporator (14B). The first evaporator (14A) and the first condensing vibe (23A) and the second evaporator (14B) and the second condensing pipe (23B) are The first and second condensing pipes (23A) and (23B) constitute a cascade condenser (25A) and (25B), respectively.
) are connected by the collecting three-way pipe (27), and then the dryer (2
8) and is connected to the first gas-liquid separator (29). The gas phase pipe (30) coming out of the gas-liquid separator (29) passes through the first intermediate heat exchanger (32) and is connected to the second gas-liquid separator (3).
3). The liquid phase pipe (34) coming out of the gas-liquid separator (29) passes through a dryer (35) and then a pressure reducer (36), and is then connected to a first intermediate heat exchanger (32) and a second intermediate heat exchanger. The connection is completed during (42). The liquid phase pipe (38) coming out of the gas-liquid separator (33) passes through a dryer (39) arranged for heat exchange in the third intermediate heat exchanger (44), and then is transferred to a pressure reducer (40).
) between the second intermediate heat exchanger (42) and the third intermediate heat exchanger (44). The gas phase pipe (43) coming out of the gas-liquid separator (33) is connected to the second intermediate heat exchanger (42)
After passing through the inside, it passes through the third intermediate heat exchanger (44), and passes through the dryer (45), which is also arranged in the third intermediate heat exchanger (44) for heat exchange, and then the pressure reducer. (46). The pressure reducer (46) is an evaporator pipe (47) as an evaporator.
), and the evaporating vibe (47) is further connected to a third intermediate heat exchanger (44). Third intermediate heat exchanger (4
4) is the second (42) and first intermediate heat exchanger (32)
The accumulator (49) is then connected to the first suction side heat exchanger (24), and then the second suction side heat exchanger (24).
22) to the suction side pipe (105) of the electric compressor (10).
). The suction side pipe (105) is further provided with an expansion tank (51) that stores refrigerant when the electric compressor (10) is stopped.
) is connected via a pressure reducer (52).

Four types of mixed refrigerants having different boiling points are sealed in the low temperature side refrigerant circuit (3). That is, R12 (dichlorodifluoromethane), R13B1 (promotrifluoromethane), R
A mixed refrigerant consisting of 14 (tetrafluoromethane) and R50 (methane) is sealed in a premixed state. The composition of each refrigerant is, for example, 4.0% by weight of R50 and 2% by weight of R14.
When combined with 2.0, an explosion occurs, but by mixing with each fluorocarbon refrigerant in the above proportions, the danger of explosion is eliminated.

Therefore, even if a mixed refrigerant leakage accident occurs, an explosion accident will not occur.

Here, in the embodiment, the evaporator of the high temperature side refrigerant circuit (2) is divided into two evaporator parts, namely, a first and second evaporator (14A) (14B).
By dividing the high pressure side piping of the low temperature side refrigerant circuit (3) into the first and second condensing pipes (23A) (23B), two cascade condensers (25A) (25B) are created.
However, the present invention is not limited thereto, and there is no problem in dividing the capacitor into more cascade capacitors without departing from the spirit of the present invention.

Next, to explain the circulation of the refrigerant, the high temperature and high pressure gaseous mixed refrigerant discharged from the electric compressor (10) is transferred to the auxiliary condenser (10).
7), most of the lubricating oil mixed with the refrigerant in the electric compressor (10) is removed from the oil separator (18) through the oil return pipe (19) to the electric compressor (10). After passing through the dryer (20), the refrigerant itself is divided into two parts by a three-way pipe (21). The refrigerant divided into two by the three-way pipe (21) is precooled separately in the suction side heat exchanger (22) or (24), and then transferred to the first (14A) in the cascade condenser (25A) or (25B), respectively. ) or the second evaporator (14B) to condense and liquefy part of the refrigerant with a high boiling point in the mixed refrigerant, and then merge in the three-way pipe (27). At this time, the mixed refrigerant is divided into two parts and cooled in small amounts separately in the cascade condenser (25A) or (25B>), so that sufficient heat exchange is carried out and the condensation effect is well achieved.

The mixed refrigerant that has exited the three-way pipe (27) passes through the dryer (28) and flows into the gas-liquid separator (29) by 4 m. At this point, R14 and R50 in the mixed refrigerant have extremely low boiling points, so they are not condensed yet and are in a gaseous state, and only R12 and R13B1 have been condensed and liquefied, so R14 and R50 are connected to the gas phase piping (
At 30), R12 and R13B1 are separated into liquid phase piping (34). The refrigerant mixture that has flowed into the gas phase pipe (30) exchanges heat with the first intermediate heat exchanger (32) and is completely condensed, before reaching the gas-liquid separator (33).

Here, the first intermediate heat exchanger (32) has an evaporating vibrator (4
7) The low-temperature refrigerant that returns from the pipe flows in, and the R13B1 that flows into the liquid phase pipe (34) passes through the dryer (35) and is depressurized in the pressure reducer (36), and then is transferred to the first intermediate heat exchanger. The temperature of the first intermediate heat exchanger (32) is -so because it contributes to cooling by flowing into the heat exchanger (32) and evaporating there.
Therefore, most of the R14 in the mixed refrigerant that passed through the gas phase pipe (30) is condensed and liquefied, and becomes R50.
has a lower boiling point, so it is still in a gaseous state. Therefore, R1
4 is from the gas-liquid separator (33) to the liquid phase pipe (38), and R
50 is separated into a gas phase pipe (43), and R14 passes through a dryer (39) and is decompressed in a pressure reducer (40), and is then separated into a second intermediate heat exchanger (42) and a third intermediate heat exchanger ( 44) and evaporates in the second intermediate heat exchanger (42). The return low-temperature refrigerant from the evaporation pipe (47) flows into the second intermediate heat exchanger (42), and the evaporation of R14 further contributes to cooling, so the temperature of the second intermediate heat exchanger (42> Furthermore, since the return low-temperature refrigerant from the evaporator vibrator (47) immediately flows into the third intermediate heat exchanger (44), its temperature is about -120'C. Since the temperature is extremely low, the gas phase piping (4) that exchanged heat with the second and third intermediate heat exchangers (42) (44)
The refrigerant R50 having the lowest boiling point passing through 3) is condensed and liquefied, passed through a dryer (45) and reduced in pressure by a pressure reducer (46), and then flows into an evaporation vibrator (47) where it is evaporated.

At this time, the temperature of the evaporation pipe (47) reached -150'C. This is the final temperature reached by the refrigeration system (R) of the present invention, and by arranging this evaporating vibrator (47) in a storage compartment of a freezer described later in a heat exchange manner, the interior of the storage compartment is made into an ultra-low temperature environment of -140°C. It becomes possible to do so. The refrigerant (mostly R50) flowing out from the evaporation pipe (47) is transferred to the third, second, and first intermediate heat exchangers (44) (
42) Each refrigerant R14 flows into and out of (32) one after another,
While merging with R13B1 and R12, the accumulator (4
After separating the unevaporated refrigerant in step 9), the suction side heat exchanger (2
4) After flowing into (22) one after another and being cooled, it is sucked into the electric compressor (10).

Here, the liquid phase piping (34) is connected to the first gas-liquid separator (29).
The R12 that has flowed into the first intermediate heat exchanger (32) flows into the first intermediate heat exchanger (32), but since the temperature is already extremely low, it does not evaporate and remains in a liquid state, so it does not contribute to cooling in any way, but the oil It functions to return residual lubricating oil that could not be separated by the separator (18) and mixed water that could not be absorbed by each dryer to the electric compressor (10) in a dissolved state. When the lubricating oil of the electric compressor (10) circulates in the low-temperature side refrigerant circuit (13), the extremely low temperature causes the lubricating oil to remain in various parts, causing clogging.

Therefore, R12 achieves almost complete return of lubricating oil.

By repeating the above, the refrigerant circuit (1) operates in a steady state to generate an extremely low temperature of -150"C in the evaporator pipe (47), but the electric compressor (4) (to) operates at 1.5H.
It only requires a P level ability, and does not require any particularly great ability.

This is largely due to the good heat exchange between the cascade condensers (25A) and (25B) and the selection of the mixed refrigerant. This achieves noise reduction and power consumption by the electric compressor. Also, by achieving -150°C, it becomes possible to cool biological materials in the freezer to a temperature lower than the recrystallization point of ice, which will be described later, and permanent preservation will be achieved. Furthermore, the refrigerant in the high temperature side refrigerant circuit (2) is transferred from the first evaporator (14A) to the second evaporator (14B>
Since the flow is not divided, both evaporators (14A
> (14B) is disrupted for some reason, a deviation in the refrigerant flow rate may occur.
23B> is achieved, and a good condensation effect is achieved.

Next, FIG. 2 schematically shows a control electric circuit for the refrigeration system (R) of the present invention. (4M) is a motor for driving the electric compressor (4) of the high temperature side refrigerant circuit (2), and is connected between the -phase or three-phase alternating current power source (AC). That is, the motor (4M) is operated continuously as long as the power (AC) is turned on. (IOM> is a motor for driving the electric compressor (10) of the low temperature side refrigerant circuit (3),
It is connected to the power supply (AC) in series with the contact (60A) of the 11L magnetic relay (60). The contact (60A) is energized by the coil (60C) of the electromagnetic relay (60) and closed.
Operate the motor (IOM). (61) is a temperature controller for the freezer storage room, which will be described later, and is a power source (AC) (A
C) is connected between and substantially detects the temperature within the storage chamber;
Set an appropriate differential above and below the set temperature,
A voltage is generated between the output terminals (61A) and (61B) at the upper limit temperature, and is stopped at the lower limit temperature. This set temperature is = 1
The temperature ranges from 45°C to 1150°C. Output terminal (61A) (6
1B), the coil (62C) of the temperature control relay (62) and the contact (63A) of the timer (63) are connected in series.

In the temperature control relay (62), the coil (62C) is energized and the contact (62A) is closed. (65> is the electric compressor (10) discharge side piping (IOC) of the low temperature side refrigerant circuit (3) in Figure 1
This is a high-pressure switch provided upstream of the auxiliary condenser (17). The high voltage switch (65) is the power source (AC
) (AC) is not connected in series with the timer (63), the pressure on the discharge side of the electric compressor (10) increases and an excessive load is applied to the compressor (10), for example, 26
kg/cm'', the contacts open, and when the pressure drops to a sufficiently safe condition, for example 8 kg/cm'', the contacts close. The timer (63) closes the contact (63A) after 3 to 5 minutes have passed after the contact of the high pressure switch (63) has closed.
The high voltage switch (65) opens and contacts (63A) open.

(66) is a low temperature start thermostat, which is installed to sense the temperature of the accumulator (15) of the high temperature refrigerant circuit (2). The refrigerant evaporated in each evaporator (14A) (14B) and the unevaporated refrigerant flow into the accumulator <15>, so the temperature is almost the same as that of the evaporators (14A) (14B), but the temperature is lower. The starting thermostat (66) closes the contacts when the temperature of the accumulator (15) drops to, for example, -35°C, and opens the contacts when the temperature rises to -10°C. Low temperature start thermostat (66)
consists of a series circuit with the contact (62A) of the temperature control relay (62) and the timer (68) on both sides, and the power supply (AC>(A)
C). The common terminal of the changeover switch (69) of the timer (68) is connected between the timer (68) and the low temperature start thermostat (66), and the electromagnetic terminal is connected between the changeover switch (69) terminal (69A) and the power supply (AC). The coil (60C) of the relay (60) is connected and the terminal (6
9B> and the power source (AC), heaters (70) and (71) provided for heat exchange before and after the pressure reducer (46) in FIG. 1 are connected in parallel. Timer 19 = timer (68) always closes changeover switch (69) to terminal (69A), is energized and integrates, and when this integration reaches, for example, 12 hours, switch (69) is closed to terminal (69A).
9B) for 15 minutes, and then close the terminal (69A) again.

Next, the operation will be explained with reference to the timing chart of FIG. When the refrigeration system (R) is installed and the power (AC) is turned on at time (to), the motor (4M) starts, the electric compressor (4) operates, and the high temperature side refrigerant circuit (
2) Refrigerant begins to circulate inside. At this time, the accumulator (
15) is close to room temperature, the low temperature start thermostat (66) is open, and therefore the temperature regulator (66) is in an open state.
Regardless of 1), the coil (
60C) is not energized and therefore the contact (60A> is open), the motor (IOM) does not start and the electric compressor (10) of the low temperature side refrigerant circuit (3) does not operate. Cooling operation of only the side refrigerant circuit (2) continues,
As the liquid refrigerant accumulates in the first and second evaporators (14A) (14B), the temperature decreases, and the temperature of the accumulator (15) decreases at the time (1,).
When the temperature reaches -35°C, the cold start thermostat (66) closes the contacts. Since the electric compressor (10) is stopped just before this closing operation, it is natural that the high pressure switch (65)
is closed, and since 3 to 5 minutes have naturally passed since the power was turned on, the timer (63) has also closed its contact (63A). Furthermore, since the temperature in the storage chamber is naturally higher than the set temperature, the temperature regulator (61) is also generating an output, so the contact (62A) of the temperature control relay (62) is closed. Therefore, when the cold start thermostat (66) closes, the fill (60C) of the electromagnetic relay (60) is energized and the contact (60C) is energized.
0A) is closed, the motor (IOM) is started, and the mixed refrigerant is discharged from the electric compressor (10) and begins to be circulated within the circuit (3).

At this time, the temperature of each part of the low temperature side refrigerant circuit <3> is still high, and therefore, most of the internal refrigerant is in a gaseous state, so the pressure within the circuit is high. Moreover, since the refrigerant is pushed out from the electric compressor (10), the pressure in the discharge side pipe (10D) increases rapidly. If this is left unchecked, the components of the electric compressor (10) will be damaged by the high pressure, but when the peak value of this pressure rise reaches the permissible limit of 26 kg at time (1,), the high pressure switch (65) will be activated. It senses this and opens the contact, so the contact (63A) opens, which forces the contact (62A) of the temperature control relay (62) to open.
The coil (60C) is de-energized, the contact (60A) opens, and the motor (IOM) stops. This prevents pressure from rising on the discharge side of the electric compressor (10) and prevents damage.

By stopping the electric compressor (10), the discharge side piping (10D
) decreases to 8 kg/cm"!, but due to the presence of a timer (63) to prevent chattering, the contact does not close for 3 to 5 minutes after the high pressure switch (65) closes, and therefore the motor (IOM) does not start.

During this time, the pressure in the low temperature side refrigerant circuit (3) changes from the first or second evaporator (14A) (14B> to the first or second evaporator).
Since the refrigerant cooled in the condensers (23A) (23B> is circulated to some extent and evaporated, the temperature and pressure have decreased since the last startup.The timer (63)
) When the delay time due to ) has elapsed at time (t, ), the contact (63A) is closed again and the motor (10M)
can be started, but the pressure in the discharge side piping (IOC) is 26k
g/cm", the high pressure switch (65) opens again and the motor (10) stops. By repeating the starting and stopping of the motor (IOM) like this, the refrigerant with a high boiling point evaporates. By gradually exerting a cooling effect, the temperature gradually decreases from the first intermediate heat exchanger (32), and when the motor (IOM) is started, the temperature of the discharge side piping (IO
When the peak value of pressure increase in D) no longer reaches 26 kg/cm', the motor (IOM) enters continuous operation.

By continuously operating the electric compressor (10), the refrigerant with a low boiling point is also condensed and gradually begins to exert a cooling effect.
The temperature of each intermediate heat exchanger (32), (42), (44) and evaporation pipe (47) is gradually lowered to reach the aforementioned final temperature. After that, the temperature in the storage room is adjusted using the temperature controller (61).
) When the lower limit temperature set in ) is reached, the output terminal (61A) (
Contact (62A) to stop the generation of output between
opens, and the contact (60A> also opens, so the motor (10A)
M) is stopped, and the cooling operation is stopped. After that, the temperature in the storage room gradually rises and when it reaches the upper limit temperature set by the temperature controller (61), the contact (62A) closes again, and then the contact (60A) closes and the motor (IOM) is started again. Cooling operation fails to start. By repeating the above steps, the storage chamber is maintained at an average set temperature of, for example, -140°C.

Here, the timer (68) integrates the time that the contact (62A) and the low temperature start thermostat (66) are closed, that is, the time that the motor (IOM) is operating, and when this integration reaches 12 hours, the switch is switched. Since the switch (69) is closed to the terminal (69B), operation of the motor (IOM) is prohibited, and the heaters (70) and (71) are energized and generate heat. Here, R50 exiting the third intermediate heat exchanger (44) and flowing into the pressure reducer (46) has reached an extremely low temperature of -120°C or less. Therefore, if an extremely small amount of moisture (this is what gets into the refrigerant during replenishment work, etc.) is mixed into the refrigerant, freezing will occur inside the pipes. By the way, since a pressure reducer is usually constructed of pipes with a small diameter, if ice grows in the pressure reducer (46), clogging will occur and the refrigerant will no longer flow; however, in the present invention, the heater (70) ( Since the pressure reducer (46) is periodically heated by the pressure reducer (46) by the pressure reducer (46), the ice crystals are melted and do not grow, thus preventing such an accident. This heater (70) (71)
The heat generation ends in 15 minutes, and the switch (69) is closed again to the terminal (69A), the motor (IOM) is activated, and the cooling operation of the low temperature side refrigerant circuit (3) is started as described above.

Next, FIG. 4 shows a front perspective view of a freezer (75) to which the present invention is applied, and FIG. 5 shows a sectional view of a main part thereof. Furthermore, the sixth
The figure is a diagram illustrating a specific configuration of a refrigerant circuit (1) of a refrigeration system (R). The freezer (75) is installed in physical and chemical laboratories, etc., and (74) is the storage room (74) with an upward opening.
6), the upper opening of which is openably closed by a heat insulating door (77) rotatably supported on the rear side. A machine room (78) is formed on the side of the main body (74) to house and install a temperature controller (61), an electric compressor (10), etc., and a machine room (78) is formed in the front of the machine room (78) to house and install a temperature controller (61), an electric compressor (10), etc. A self-recording temperature recording needle (79) that senses the temperature of the room and records its time course on recording paper, a common knowledge alarm (80) that issues an alarm in case of abnormally high temperature in the storage room (76), and a temperature controller (61). A setting change knob (81) is provided. Further, (82) is a ventilation slit.

FIG. 5 shows a side sectional view of the main body (74) portion. (
83) is a steel plate outer box with an upward opening, (84) is an aluminum inner box with an upward opening, and the inner box (84) is incorporated into the outer box (83), and both boxes (83) ) Box-shaped external insulation material (85) with independent upward openings between each
A double heat insulating layer consisting of the box and the inner heat insulating material (86) is formed, and the opening edges of both boxes (83) and (84) are connected by a breaker (87). An evaporation pipe (
47) is disposed in a thermally conductive manner and buried in the inner insulation material (86), and a sheath prevention pipe (6) is disposed in a thermally conductive manner on the inner surface of the opening edge of the outer box (76). has been done. The inner insulation material (86) is placed inside the outer insulation material (85) and is completely separated, so even if the inner insulation material (86) contracts due to the cooling action of the evaporation pipe (47), External insulation material (8
5) is not affected to the same extent, therefore, cracking of the heat insulating material does not occur, and sufficient heat insulating performance is maintained. An opening (88) is formed on the back surface of the outer box (83), and a corresponding notch (89>) is formed in the outer heat insulating material (85), and the opening (88) is formed in the notch (89). ), cascade capacitors (25A), (25B), etc. molded with heat insulating material (9o) as described later are covered with a housing cover plate (91). (92) is an inner cover made of styrofoam; (93) is a gasket on the inner peripheral surface of the heat insulating door (77), and (94) is a transport caster.

Next, FIG. 6 shows a specific configuration of the refrigerant circuit (1) of the refrigeration system (R), in which the same reference numerals as in FIG. 1 are the same. The auxiliary condenser (17) of the low temperature side refrigerant circuit (3) is connected to the high temperature side refrigerant circuit (2) with respect to the air suction type blower (9).
) is placed on the windward side of the condenser (8) so that it is cooled at the same time. First and second evaporators (14A) (14
B) has the shape of a hollow tank, into which first and second condensation pipes (23A) and (23B) wound in a spiral manner are respectively inserted from above. (
66A) is a cylindrical body for fixing a low temperature starting thermostat (66) that is welded and fixed to the accumulator (15). (
96) is each intermediate heat exchanger (32) (42) (4) described later.
4), etc., and is molded with a heat insulating material (97) to form a box-like intermediate heat exchanger section. The evaporation pipe (47) is fixed in advance to the outer surface of the inner box (84) in a meandering manner with aluminum tape or adhesive, but in order to reduce the temperature distribution in the storage chamber (76) at no actual cost. The order in which the refrigerant flows is from around the top of the inner box (84) to around the bottom, and finally around the bottom.

FIG. 7 shows the structure of the intermediate heat exchanger section (96). The parts surrounded by dotted lines are the first, second and third intermediate heat exchangers (32)
(42), (44), a second gas-liquid separator (33), a dryer (39), (45), a pressure reducer (40), and an intermediate heat exchanger section (96) that includes an accumulator (49). . Each intermediate heat exchanger (32) (42) (44) consists of relatively large diameter outer pipes (98), (99), and (100) wound spirally in multiple stages to form a flat structure, which are mutually superposed. It has a spiral double pipe structure in which the gas phase pipes (3Q) and (43) pass through as inner pipes at intervals, and in the figure (A> part is the first intermediate The heat exchanger (32), the part (B) becomes the second intermediate heat exchanger (42), and the part (C) becomes the third intermediate heat exchanger (44). second gas-liquid separator (33), dryer (39) (45),
A pressure reducer (4o) and an accumulator (49) are housed to reduce dead space and reduce size.

Next, the configuration will be explained. (101) is a pipe connecting the dryer (28) and the first gas-liquid separator (29). The gas phase pipe (3o) exiting upward from the first gas-liquid separator (29) enters the outer pipe (98) through the sealed inlet (INs),
After passing through the interior in a spiral, exit (QUIT>
and enters the second gas-liquid separator (33). Gas phase piping (
During this passage, the gaseous refrigerant flowing down within 30) is condensed by the low temperature refrigerant rising up the gap between the gas phase pipe (30) and the outer pipe (98). The gas phase pipe (43) coming out of the second gas-liquid separator (33) enters the outer pipe (99) through the entrance (IN!). After the liquid refrigerant separated in the first gas-liquid separator (29) is depressurized by the pressure reducer (36), the liquid refrigerant is connected to the outlet (QUIT) of the outer pipe (98) and the inlet (99).
The gaseous refrigerant in the gas phase pipe (30) is condensed together with the refrigerant that flows into the communication pipe (102) connecting the INx), evaporates in the outer pipe (98), and returns from the evaporation pipe (47). Contribute to The gas phase pipe (43) that entered the outer pipe (99) exits from the outlet (outS) and returns to the inlet (I).
It enters the outer pipe (100) from N, ), circulates in a spiral shape, and exits from the outlet (OUTs). The outer piping of each outlet and inlet section is sealed. Second gas-liquid separator (33
) The liquid refrigerant separated by the outer pipe (100) passes through a dryer (39) provided for heat exchange, is depressurized by a pressure reducer (40), and then is transferred to the outlet (OUTa) of the outer pipe (99). The refrigerant flows into the communication pipe (103) connecting the inlets (INs) of (100), evaporates in the outer pipe (99), and returns from the evaporation pipe (47) together with the gas phase pipe (4).
3) Contributes to the condensation of the gaseous refrigerant within. Gas phase piping (43
) The refrigerant R50 flowing down inside the outside pipe (100) is further condensed and almost liquefied when passing through the outside pipe (100).
oo) and a dryer (45) provided for heat exchange, and then a pressure reducer (46). (105) is a pipe that can be connected to the outlet side of the evaporation pipe (47), and is the outlet (O
UTa) and communicates with the outer space of the gas phase pipe (43). In addition, (106) is the inlet (
This is a pipe that communicates between the outer space of the gas phase pipe (30) and the accumulator (49) in the INK). That is, the return refrigerant from the evaporation pipe (47) flows from the pipe (105) into the space between the outer pipe (100) and the gas phase pipe (43), rises there, and flows down inside the gas phase pipe (43). The incoming refrigerant is condensed and merged with the refrigerant from the pressure reducer (40) in the communication pipe (103), and is transferred to the outer pipe (99) and the gas phase pipe (43).
The refrigerant flows into the gap between the two and rises there, condenses the refrigerant in the gas phase pipe (43), and then passes through the communication pipe (102) to the pressure reducer (3).
6), flows into the space between the outer pipe (98) and the gas phase pipe (30), rises there, and flows into the gas phase pipe (30).
After the refrigerant in 30) is condensed, it passes through piping (106) to reach the accumulator (49), and flows into the suction side heat exchanger (24) through piping (108). As described above, the flow of refrigerant flowing down inside the gas phase pipe (30> or (43)),
From the evaporation pipe (47) to the gas phase pipe (30) or (43)
) and the flow of refrigerant rising between the outer pipes (100), (99), and (9B) are mutually opposing flows.

Next, FIG. 8 shows a rear perspective view of the freezer (75), and the procedure for assembling the refrigeration apparatus (R) will be explained. An opening (110) is formed on the back side of the outer box (83) in parallel with the opening (88), and correspondingly, a notch (111) is also formed in the outer insulation material (85).
) is completely formed. Inside the heat insulator (90) are the cascade condensers (25A) (25B), the suction side heat exchanger (23l-2) (24), the accumulator (15) and the dryer (2).
8) Mold. The molding method for the insulation materials (90) and (97) is to house the parts to be molded in a resin bag, place them in a box-shaped foam mold in that state, and fill the bag with foam and mold the urethane insulation material. It is something to do. A pressure reducer (46) and piping (105) are extended from the heat insulating material (97), and welded to the evaporation pipe (47) led out from the lead-out part (112) at the back of the notch (111). Connecting. Pipes such as the pressure reducer (13) extending from the heat insulating material (90) are welded and connected to piping led out from the wall surface of the notch (89) on the machine room (78) side. The first gas-liquid separator (29) and the dryer (35) are located outside the heat insulating material (90), and the insulating materials (90) and (97) are also connected to each other through the notches (
89) (111), fill the gap with glass wool, etc., and then fill the notch (89) and (11) with the cover plate (91).
Complete the installation by covering 1). In addition, electric compressors (4) (10), condenser (8), blower (9), expansion tank (51), etc. are installed in advance in the machine room (78), so that the freezer (75) Complete.

Although the ideal operating conditions of the refrigeration system (R) of the present invention have been described above, the final stage, that is, the third intermediate heat exchanger (44
) to the evaporation pipe (47) is as described above (71J1
Since it is cooled to an extremely low temperature such as <-120°C to -150"C, even with strict insulation as in the above-mentioned configuration, heat intrusion from the surroundings will cause damage to the third intermediate heat exchanger (44).
The liquid refrigerant that has passed through tries to evaporate within the pressure reducer (46). Here, the uncondensed refrigerant from the second gas-liquid separator (33) contains some R14 refrigerant, but is mostly R50 refrigerant. Further, FIG. 9 shows the relationship between the pressure and evaporation temperature of R50 refrigerant. As mentioned above, when the R50 refrigerant evaporates inside the pressure reducer (46), the inside diameter of the pressure reducer (46) is very small (usually 1 ml or less), so the inside of the pressure reducer (46) is immediately filled with gas refrigerant. If the storage chamber (76) becomes full, the passage resistance becomes excessive and the liquid refrigerant cannot flow, and the temperature of the evaporation pipe (47) rises, making it impossible to cool the storage chamber (76) sufficiently.

However, the obstruction of the flow of the liquid refrigerant in the pressure reducer (46) also causes the pressure before entering the pressure reducer (46) to increase by 1, so that the evaporation temperature of the R50 refrigerant increases as shown in FIG. As a result, evaporation in the pressure reducer (46) is no longer performed, and liquid refrigerant is again supplied to the evaporation vibe (47) to perform normal cooling. However, if the temperature drops due to this, the pressure reducer (4
Evaporation begins within 6〉, and this process is repeated. In such a situation, not only will there be insufficient cooling in the storage room (76), but the load applied to the electric compressor (10) will fluctuate drastically, which will not only impair the life of the electric compressor (10) but also cause noise. also becomes larger. Therefore, in this application, the dryer (4
5) is disposed in a third intermediate heat exchanger (44) for heat exchange, and the R50 refrigerant that has passed through the third intermediate heat exchanger (44) is cooled again to reduce the temperature rise due to heat intrusion from the surroundings. is suppressed. This prevents the refrigerant from evaporating within the pressure reducer (46) and eliminates the aforementioned insufficient cooling.

Further, such an abnormal situation also occurs when the amount of refrigerant that can be filled into the low temperature side refrigerant circuit (3) is not appropriate. That is, Fig. 9 shows the time course of the temperature in the storage room (76) after the power is turned on to the refrigeration system (R), where (Ll) represents the case where the refrigerant charge is appropriate, and (L2) represents the case where the refrigerant filling amount is appropriate. (L,) indicates a case where the amount of refrigerant charged is too large, and (L,) indicates a case where the amount of refrigerant charged is too small. Moreover, FIG. 10 shows the temperature inside the storage chamber (76) when the amount of refrigerant charged is excessive near the final temperature (L2
) and (L, ), which is the temperature when the temperature is too low, are shown.
4) is the temperature of the refrigerant flowing into the pressure reducer (46) when the amount of refrigerant charged is excessive, that is, the temperature of the refrigerant flowing into the pressure reducer (46) inlet part (P
I) temperature, (L6〉 is similarly the pressure reducer in case of excess (
46), that is, the temperature of the refrigerant after leaving the evaporator vibrator (
47) The temperature of the inlet (P2), (L6) is the temperature of the pressure reducer (46) inlet (PI) when the refrigerant charge is too low, and (L,) is the evaporation temperature when the refrigerant charge is too low. The temperature of the inlet part (P, ) of the vibrator (47) is shown.

When the amount of refrigerant charged is excessive, the temperature of the storage chamber (76) decreases at a faster rate from the start of the cooling operation than when the amount of refrigerant charged is normal. However, evaporation vibrator (47)
Since the amount of liquid refrigerant that can be supplied to the storage room (76
) when the temperature inside the evaporator vibrator (4) drops to the reached temperature.
7) A large amount of liquid refrigerant that cannot be completely evaporated in the third intermediate heat exchanger (44) flows into the third intermediate heat exchanger (44) and evaporates there.
The temperature of the intermediate heat exchanger (44) continues to cool down to a value equivalent to that of the evaporator vibrator (47). This allows the pressure reducer (4
6) The temperature at the inlet (P,) also decreases, but since the temperature difference with the surroundings increases, the amount of heat intrusion from the surroundings increases, promoting evaporation of the liquid refrigerant. This allows the pressure reducer (4
The liquid refrigerant starts to evaporate inside the pressure reducer (46), and the flow of the liquid refrigerant is obstructed by the increase in pressure inside the pressure reducer (46), and the supply of liquid refrigerant to the evaporation vibe (47) decreases.
) temperature also rises. Thereby storage room (76)
The temperature inside also rises. When the flow of the liquid refrigerant is obstructed within the pressure reducer (46), the pressure of the liquid refrigerant increases as described above, the evaporation temperature rises, the liquid refrigerant no longer evaporates, and the liquid refrigerant passes through the pressure reducer (46) again. Normal cooling begins to occur, but as a result of subsequent cooling, the liquid refrigerant evaporates into the vibrator (47).
If there is anything left, the same situation will repeat itself over and over again. That is, (Lx)(L4)(t
As shown in 6), each temperature pulsates and becomes unstable. Here, the temperature in the storage chamber (76) is somewhat delayed. When such an upward trend occurs, the temperature inside the storage room (76) periodically exceeds the normal state (1,) as shown in Figure 9, resulting in insufficient cooling.
This causes an increase in vibration noise and abnormal wear of the electric compressor (10).

In such a situation, the temperature of the refrigerant entering the pressure reducer (46) approaches the temperature of the refrigerant after leaving it,
6) The temperature of the inlet part (P,) decreases and the evaporation vibrator (47
) It has been experimentally confirmed that the temperature of the inlet part (P) is too close to the temperature of The refrigerant is charged in such a way that the temperature difference between the two and

Also, together with this, the dryer (45) is connected to the third intermediate heat exchanger (
44) for heat exchange to reduce the influence of heat intrusion, which further stabilizes the temperature.

Next, if the amount of refrigerant charged is too small, the cooling rate will naturally become slow as shown in (L,) in FIG. In addition, since a small amount of refrigerant is circulating in the low temperature side refrigerant circuit (3), a small amount of liquid refrigerant flows from the pressure reducer (46) to the evaporation pipe (47).
) and immediately evaporate, thereby causing the flow in Figure 10 (L
As shown in 7>, the temperature at the inlet part (P,) of the evaporator pipe (47) decreases, but since the amount of liquid refrigerant is small, the evaporation ends immediately, and after that, the gaseous refrigerant flows into the evaporator pipe (47).
7) to the third intermediate heat exchanger (44). As a result, the inside of the storage room (76) becomes insufficiently cooled and the temperature rises, becoming stable at a high value as shown in (L8), and the temperature of the third intermediate heat exchanger (44) also increases.
In order to raise the temperature, a pressure reducer (
46) The temperature at the inlet (P,) also rises as shown in (L6),
The temperature difference between the (p+> point and the (P2) point becomes very large.

Here, in the refrigeration system (R) of the present invention, the difference of 100°C between the temperature (-50°C) of the cascade condensers (25A) (25B) and the temperature (-15°C) of the evaporation pipe (47) is ) (40) and (46) are created in stages by creating a temperature difference before and after each. In other words, the temperature difference between the receivers before and after each pressure reducer (36), (40), and (46) is evenly divided (normally, the temperature difference is set smaller as the temperature decreases to reduce the load as much as possible). .) 33℃, and this temperature difference makes the pressure reducer (46〉
When the temperature difference between the inlet part (PI) and the inlet part (P,) of the evaporation pipe (47) becomes large near the reached temperature, it is abnormal, and the cause is the insufficient amount of refrigerant charged as mentioned above. I can say it. Therefore, in the present invention, the points (PI) and (P,
) By filling the refrigerant so that the temperature difference between the two and

In summary, the temperature of the refrigerant flowing into the pressure reducer (46) and the temperature of the refrigerant after leaving the pressure reducer (46) depend on the temperature of the pressure reducer (46) inlet (Pl) and the temperature of the evaporation pipe (47) inlet (ft). Measure the temperature difference, and if the difference is greater than 10℃ near the final temperature, and if the cascade capacitor (25A
) (25B) and the evaporation pipe (47) using a pressure reducer (
36) By filling the refrigerant in a range smaller than the value divided by the number of (40) and (46), that is, 33°C, an appropriate amount of refrigerant can be charged.

Here, the refrigeration device (R) is also affected by the temperature of the surroundings in which it is installed. In other words, assuming a situation where the ambient temperature is high and the refrigerant is filled to exhibit sufficient cooling capacity, when the ambient temperature becomes low, the cascade condensers (25A) (25B) and each intermediate heat exchanger (32
) (42) and (44), so in addition to the refrigerant that should be condensed in each intermediate heat exchanger, a portion of the refrigerant that should be condensed in the subsequent intermediate heat exchanger also condenses.
Since the R50 refrigerant returns to the electric compressor (10), the amount of R50 refrigerant that finally flows into the evaporation pipe (47) decreases, resulting in insufficient cooling. If the amount of refrigerant charged is increased to solve this problem, the above-mentioned pulsation will occur when the ambient temperature is high.

In contrast, according to the present invention, by filling the refrigerant in such a way that the temperature difference between points (P, ) and (P2) is greater than 10°C and smaller than 33°C, the ambient temperature can be changed from high to low. This makes it possible to demonstrate stable cooling capacity.

The self-recording temperature recorder (79) records the temperature inside the storage room (76), and is one of the important components in this type of freezer. By the way, the recorder (79) is generally composed of a well-known Bourdon tube (120) having an Archimesian spiral shape as shown in FIG. 11, and a recording paper (not shown) that is automatically moved as time passes. In FIG. 11, (121) is a temperature sensing part arranged to sense the temperature inside the storage chamber (76), and the Bourdon tube (120) and the temperature sensing part (121) are the thin tubes (122). They are connected in communication. For example, a drive shaft (123) is erected and fixed at the center (0) of the spiral of the Bourdon tube (120).
3) A recording pointer (124) is attached to the tip. The Bourdon tube (120) has a hollow interior, and a temperature-sensitive substance such as ethyl alcohol or n-propyl alcohol is sealed therein in liquid form. Bourdon tube (12
0) is deformed by a change in internal pressure due to a change in temperature around the temperature sensing part (121), causing the drive shaft (123) to rotate around the axial direction.
) is known to be proportional to the pressure change in the Bourdon tube (120), and thereby converts and records the temperature in the storage chamber (76) to the position of the pointer (124).

By the way, general temperature-sensitive substances such as ethyl alcohol and n-propyl alcohol are used at temperatures around -80°C, and they freeze at ultra-low temperatures such as -150"C, which is the subject of the present invention, making it impossible to record temperature. Therefore, as a result of intensive research, in the present invention, we have achieved the ability to record temperatures at extremely low temperatures such as -150@C by enclosing 2-methylpentane (isohexane) as a temperature-sensitive substance. Figure 12 shows the relationship between the temperature (I> around the temperature sensing part (121) and the Bourdon tube (120) when 2-methylpentane is sealed in the Bourdon tube (120).
The relationship between pressure (P) within 0) is shown. As is clear from the figure, the pressure (P) is approximately proportional to the temperature (T) in the temperature range from -150"C to +50"C.Here, the rotation angle (θ) of the pointer (124) is the pressure (P) as described above. Since it is proportional to the temperature (
T), and thereby -150"C to +5
The temperature in the storage chamber (76) can be recorded in the range of 0°C.

In the embodiment, two independent refrigerant circuits are connected in cascade, and the refrigerant circuit on the low temperature side is a mixed refrigerant refrigeration system. The application is also valid.

(G) Effects of the Invention According to the present invention, in a refrigeration system consisting of a refrigerant circuit using a non-azeotropic mixed refrigerant, the temperature of the refrigerant flowing into the final stage pressure reducer and the temperature of the refrigerant after leaving the pressure reducer are By keeping the difference in the appropriate range, which is smaller than the value obtained by dividing the temperature difference between the condenser and evaporator by the number of pressure reducers, and larger than 10℃,
Since the appropriate amount of refrigerant can be charged, it eliminates the pulsation in the temperature of the space to be cooled that occurs when the amount of refrigerant is too high, and the insufficient cooling that occurs when the amount of refrigerant is too low, and also reduces the effects of ambient temperature. Therefore, it is possible to construct a cooling device that exhibits stable performance without being subjected to any damage.

[Brief explanation of drawings]

Figures 1 to 9 show embodiments of the present invention, Figure 1 is a refrigerant circuit diagram of the refrigeration system, Figure 2 is a control electric circuit diagram, and Figure 3 is a timing diagram for explaining the operation of the refrigeration system. chart,
FIG. 4 is a perspective view of the freezer, FIG. 5 is a side sectional view of the freezer body, FIG. 6 is a diagram showing the specific configuration of the refrigerant circuit of the refrigeration system, and FIG. 7 is a perspective view of the intermediate heat exchanger section. Fig. 8 is a rear perspective view of the freezer, Fig. 9 is a diagram showing the time transition from power on inside the storage room, and Fig. 10 is the temperature reached when the refrigerant charge amount in the low-temperature side refrigerant circuit is too much or too little. Figures 11 and 12 are diagrams showing storage room temperatures in the vicinity. Figures 11 and 12 show an example of a self-recording temperature recorder. Figure 11 is a perspective view of a Bourdon tube that constitutes the self-recording temperature recorder. FIG. 3 is a diagram showing the relationship between the internal pressure of a Bourdon tube filled with 2-methylpentane and the temperature of the temperature sensing part. (R)... Refrigeration device, (2)... High temperature side refrigerant circuit, (3)... Low temperature side refrigerant circuit, (4) (10>...
・Electric compressor, (25A) (25B>... Cascade condenser, (32) (42) (44)... Intermediate heat exchanger, (36) (40) (46)... Pressure reducer, (
47)...Evaporation pipe. Applicant Sanyo Gunki Co., Ltd. and one other agent Patent attorney Takuji Nishino and one other person Figure 4 Figure 5

Claims (1)

[Claims] 1. Equipped with a compressor, a condenser, an evaporator, a plurality of intermediate heat exchangers connected in series so as to circulate the return refrigerant from the evaporator, and a plurality of pressure reducers, and a non-azeotropic mixed refrigerant of multiple types. The condensed refrigerant in the refrigerant that has passed through the condenser is made to flow into the intermediate heat exchanger via the pressure reducer, and there, the uncondensed refrigerant in the refrigerant is cooled to gradually lower the boiling point. In a refrigeration system that obtains an extremely low temperature by condensing a refrigerant and causing a refrigerant with the lowest boiling point to flow into the evaporator via a final stage pressure reducer, the refrigerant flowing into the last stage pressure reducer and the refrigerant exiting the last stage pressure reducer are A refrigeration system characterized in that a difference in temperature between the subsequent refrigerant is set in a range smaller than a value obtained by dividing the temperature difference between the condenser and the evaporator by the number of pressure reducers and larger than 10°C.