WO2007029390A1

WO2007029390A1 - Control system for refrigerating machine employing non-azeotropic refrigerant

Info

Publication number: WO2007029390A1
Application number: PCT/JP2006/311961
Authority: WO
Inventors: Susumu Kurita; Nobuyoshi Kurita
Original assignee: Dairei Co., Ltd.; Nihon Freezer Co., Ltd.
Priority date: 2005-09-08
Filing date: 2006-06-14
Publication date: 2007-03-15
Also published as: EP1923645A4; US20080302116A1; JP2007071468A; TW200710355A; TWI310827B; EP1923645A1; CN101128707A; KR20080042035A

Abstract

[PROBLEMS] To improve the initial pulling-down performance of a refrigerating machine employing a non-azeotropic refrigerant immediately after starting when the chamber temperature is high. [MEANS FOR SOLVING PROBLEMS] A single-stage refrigerating machine which employs a non-azeotropic refrigerant and has a compressor (1), a condenser (2), and an evaporator (10), and in which heat exchange (3) is conducted between the refrigerant returned from the evaporator and the high-pressure refrigerant flowing from the condenser toward the evaporator is controlled in the following manner. When a high load is imposed as just after starting, capillary tubes (6-1) to (6-5) serving as expansion valves for the evaporator are made fully open with electromagnetic valves (5-1) to (5-5). As the internal temperature of the chamber declines, the tubes are successively closed. Thus, the pressure and flow amount of the refrigerant gas are regulated. When the internal temperature of the chamber is high and the condensation of a low-boiling ingredient does not proceed, the refrigerating ability of a high-boiling refrigerant can be exhibited in the highest degree.

Description

Specification

Refrigerator control system using non-azeotropic refrigerant

Technical field

[0001] The present invention, in a refrigeration system using a non-azeotropic refrigerant mixture, has a large scale, particularly in a freezer warehouse, and therefore requires a large capacity for starting up to a predetermined freezer temperature or The present invention relates to a freezer for a freezer having a large fluctuation in the internal temperature due to the necessity of opening the door widely when taking in and out the contents.

Background art

[0002] As a freezer that can maintain the freshness of meat, seafood, etc. for a relatively long time without deterioration, freezers that achieve ultra-low temperatures of 50 ° C or less are used at production ports, fishing ports and distribution bases. However, in the past, refrigeration systems that achieve these ultra-low temperatures are refrigerators that use low-boiling refrigerants with boiling points in these regions and refrigerations that use high-boiling refrigerants that operate at room temperature. A two-stage refrigerator system consisting of two compressors and a condenser has been used.

In contrast, the present inventors have achieved a very low temperature by a simple single-stage compressor by combining a low boiling point refrigerant that realizes an ultra low temperature and a high boiling point refrigerant that can be condensed in a room temperature environment. We have proposed a refrigerator system to be realized. (Patent Document 1)

In these ultra-low temperature refrigerator systems, heat is exchanged between the return refrigerant gas discharged from the evaporator at a low temperature and the high pressure refrigerant gas directed to the evaporator, and the heat of vaporization of the high boiling point refrigerant in the return refrigerant gas. By condensing the low-boiling point refrigerant in the high-pressure refrigerant gas, the conditions for completing the condensation and vaporization cycle of the non-azeotropic refrigerant before and after the evaporator are established, and a single refrigerant is used using the non-azeotropic refrigerant. Alternatively, ultra-low temperature was achieved by a single-stage simple refrigeration system consisting of a single compressor and condenser similar to the case of using an azeotropic refrigerant.

Patent Document 1: Japanese Patent Laid-Open No. 11 99498

[0003] When such a refrigerator system using a non-azeotropic refrigerant is applied to a so-called stocker having a relatively small capacity, the door is generally placed on the upper surface of the freezer because of its small heat capacity. Because it opens and closes flatly, the amount of cool air in the cabinet is small when the storage is taken in and out, so the temperature fluctuation in the cabinet is small and it is possible to maintain a relatively stable operating state. For example, if the storage capacity of the storage becomes large for business use, such as storage without storage, etc. Due to the necessity of space allocation for these operations and storage, etc., the vertical door opening and closing method has been adopted, and only the improvement in capacity at start-up due to volume expansion is required. The amount of ventilation with the outside air when taking in and out the work is also increased.To this end, it is necessary to maintain the inside temperature, to speed up the power of the elevated temperature to the storage temperature, and to return to the storage temperature. became.

However, if we try to cope with these capacity improvements by increasing the capacities of the individual components of the refrigerator, such as compressors and condensers, the increase in the capacity associated with the increase in the capacity of these facilities will not only be a heavy burden, but also the conditions during steady operation. Therefore, it becomes an excessive facility capacity. In addition, the power to cope with these temporary increases in the load by increasing the output of the compressor. The cooling capacity corresponding to the output with poor rise and followability to these temperature changes has not been demonstrated.

In particular, when the contents in the freezer were frequently taken in and out and the temperature inside the warehouse fluctuated significantly, it did not quickly return to the steady state temperature, and it was difficult to maintain a stable inside temperature. As a result of various studies on the cause, the present inventors have found that this is due to the following characteristics specific to non-azeotropic refrigerants.

In other words, it is necessary to fully demonstrate the cooling capacity of the refrigerator, such as when the refrigerator is started up, or when the internal temperature of the refrigerator with a large amount of ventilation is large, but it will be in a steady operation state. In the state in which the internal temperature is high, the temperature of the return refrigerant in the heat exchanger is also high, and even if the condensed high-boiling-point refrigerant component in the non-azeotropic refrigerant is vaporized and the high-pressure side refrigerant is cooled, the temperature is sufficiently high. The low boiling point refrigerant component circulates in the refrigerator without condensing. For this reason, the discharge pressure from the compressor increases, but the low boiling point component does not condense. If the low-boiling components in the non-azeotropic refrigerant are not condensed in this way and are circulated in the refrigerator system in the gaseous state, the evaporator is passed through the condenser power heat exchanger even if compressed to a high pressure by the compressor. Since these low-boiling components remain in a gaseous state until the end of the process, even if the compressor's load increases and the pressure rises due to overload operation of the compressor,

As mentioned above, the amount of heat released from the condenser does not increase, so the overall cooling capacity does not increase, and the internal temperature does not decrease easily. That is, the cooling effect in these transient states is mainly due to the condensation and vaporization of high-boiling components. Therefore, since the circulation amount of these refrigerants cannot be secured, the cooling capacity by these cannot be maintained and exhibited. In these transient states, the low-boiling components are not cooled to a sufficient temperature and cannot exhibit their ultra-low temperature cooling capacity, but they do not condense even when the pressure of the compressor rises, and the entire refrigerant is circulated and thus cooled. This hinders the increase in capacity and the return to steady operation.

Disclosure of the invention

Problems to be solved by the invention

[0005] In a single-stage refrigeration system using a non-azeotropic refrigerant,

Until the condensation of low-boiling components does not proceed at the time of startup or when the internal temperature rises, the refrigerant flow rate in the state is increased to improve the cooling capacity, and the internal temperature decreases to the steady operation state. The load fluctuation during the period is suppressed, and stable operation is possible.

Means for solving the problem

[0006] The present invention relates to a compressor, a condenser, an evaporator, and a single-stage refrigerator using a non-azeotropic mixed refrigerant that performs heat exchange between a return refrigerant from the evaporator and a counter-pressure high pressure refrigerant from the condenser to the evaporator. In

The refrigerant gas pressure and flow rate can be adjusted according to the opening of the evaporator expansion valve. At the time of start-up or in the state where condensation of low boiling components with high internal temperature does not proceed, the evaporator expansion valve is opened to increase the boiling point. Maintain the pressure according to the condensation conditions of the components to improve the cooling capacity of the high-boiling components, and as the internal temperature decreases and the condensation of the low-boiling components proceeds, the evaporator expansion valve is throttled to gradually lower the boiling point. Non-azeotropic refrigerant mixture characterized by being in a steady operation state by setting the pressure to satisfy the condensing conditions of the components Refrigeration system using

In particular, a plurality of capillary tubes are provided in parallel as expansion valves for the evaporator, and the above flow rate is controlled by the number of opening and closing of the tubes.

The invention's effect

[0007] According to the present invention, in a single-stage refrigeration system using a non-azeotropic refrigerant, the low boiling point in the non-azeotropic refrigerant in which the operating temperature of the refrigeration system is high at the time of start-up or when the internal temperature rises. When starting up from a state where the condensation of components is insufficient, it is possible to maximize the cooling capacity, smoothly reduce the internal temperature to a steady state, and the compressor of the refrigeration system The load can be reduced.

Brief Description of Drawings

FIG. 1 is a conceptual diagram of a refrigeration system of the present invention.

[Fig.2] Cooling rate curve showing the relationship between the number of claws and the cooling rate

Explanation of symbols

[0009] 1 compressor

2 Condenser

3 Heat exchanger

5—:! To 5 — 5 Solenoid valve

6 _1-6 5 Throttle valve (Cabinet-)

7 Freezer

10 Evaporator (Evaporator)

11 Temperature detector

12 Control equipment

BEST MODE FOR CARRYING OUT THE INVENTION

[0010] The refrigerant used in the refrigerator of the present invention is a non-azeotropic refrigerant mixture, and particularly a low boiling refrigerant component having a normal boiling point of 50 ° C or lower in order to achieve an ultra-low temperature of 50 ° C or lower. Condensed in an environment at room temperature and made of a combination of high boiling point refrigerant with high boiling point and low vapor pressure that enables heat dissipation from the condenser, high temperature and high pressure from the condenser to the evaporator Heat is exchanged between the refrigerant in the state and the low-pressure, low-temperature refrigerant from the evaporator toward the compressor, and the high-pressure refrigerant toward the evaporator is cooled below the boiling point under that pressure and sucked into the compressor Operates under conditions that heat the gas above its dew point at that pressure.

In order to achieve the above conditions in the configuration of the refrigerator, a compressor, a condenser, a throttle valve, and an evaporator are used, and a heat exchanger is provided between the condenser and the throttle valve, and between the evaporator and the compressor. Although the replacement conditions are achieved, the opening of the throttle valve can be adjusted, and a sensor that measures the internal temperature and a control mechanism that adjusts the opening of the throttle valve based on the detected temperature are provided.

When the refrigerator is started or when the internal temperature rises above a certain value due to taking in and out of the freezer contents, the opening of the throttle valve is maximized, and the throttle valve When the refrigerant flow rate is reduced by reducing the opening, and the internal temperature falls below the specified temperature, the opening of the throttle valve is minimized.

As a throttle valve for a non-azeotropic refrigerant mixture, more preferably, a plurality of capillary tubes are provided in parallel, and the refrigerant flow rate is controlled by sequentially opening and closing these capillary tubes with solenoid valves according to the internal temperature. To do.

Example

The outline and specifications of the refrigeration system of the embodiment of the present invention are given below.

Fig. 1 is a conceptual diagram of the system configuration of the refrigerator of the present invention.

The refrigerant gas compressed by the compressor 1 is dissipated to the atmosphere by the condenser 2 and then branched into five via the heat exchanger 3, and the capillary valve 6_ :! 1-6_5 is led and expand | swells, it vaporizes within the evaporator 10 arrange | positioned along the freezer inner wall, and the freezer 7 is cooled.

In the evaporator, a part (high-boiling point refrigerant component) is condensed and sent to the heat exchanger along with the return gas according to the internal temperature and pressure. Condenses low-boiling refrigerant components.

The temperature in the freezer is detected by the temperature sensor 11, and the solenoid valve 5— :! to 5—5 is opened / closed according to the temperature preset by the control device 12 to allow the refrigerant to flow through. Control the number of tracks.

At startup and in a state where the internal temperature is higher than a certain level, all the solenoid valves are opened, and the refrigerant is conducted to all the capillary tubes.

When the internal temperature exceeds a certain set temperature, the solenoid valve is sequentially closed and controlled to the refrigerant circulation amount and the compressor discharge pressure according to the internal temperature, and when the internal temperature reaches a preset steady state, It is operated with only one capillary tube.

The specifications of the actual machine are as follows.

Freezer structure: Prefabricated structure with double doors

Freezer volume: 4275 liters

Normal temperature: 1 50 ° C or less, maximum 1 60 ° C

Refrigerant: 4400 g of EP-53P was enclosed and used. Table 1 shows the component gas specifications for the mixed refrigerant. The composition of the non-azeotropic refrigerant EP-53P, HFC_ 23: 40 weight ^_0/0, HFC_ 134a: was used in 60 wt%.

[table 1]

Non-azeotropic refrigerant composition used and its physical properties

[0013] Table 2 shows the changes in the internal temperature when starting up with one capillary tube in the system configuration of FIG. The internal temperature was measured at the top of the freezer.

The time required to reach a set temperature of 50 ° C from a room temperature of 34 ° C was approximately 5 hours.

[0014] [Table-2] Operating conditions for a single tube (room temperature: 31 34 ° C)

[0015] Next, Table 3 shows changes in the internal temperature of the example using the four tuberary tubes.

The internal temperature is measured in the upper stage of the freezer, and the solenoid valve is sequentially closed at the switching temperature of the four capillary tubes: 0 ° C -10 ° C _ 25 ° C, and the capillary tube 1 is always turned on in the lower temperature range. Drove as. The results are shown in Table 3.

The time required to reach the set temperature of 50 ° C was about 4 hours.

[0016] [Table 3] Operating conditions when using four tubes (room temperature: 31 to 33 ° C)

Compressor discharge Compressor suction Heat exchanger Heat exchanger Operation Compressor discharge Compressor suction

t ik. Pressure Pressure Inlet temperature Outlet temperature Time Temperature (° c) Temperature (° c)

(.C) (Mpa) (MPa) (° C) (° c)

0:00

0:30 -15.3 2.20 0.25 101.0-3.8 78.4 -21.0

1: 00 -30.6 2.40 0.070 1 14.0 15.6 98.0 -33.8

1: 30 -38.2 2.20 0.060 122.1 10.9 105.0 -38.6

2:00 -41.8 2.20 0.060 122.0 10.5 10.4 -39.5

2:30 -45.1 '20.5 0.060 122.0 10.0 104.0 -41.4

3:00 -47.9 20.0 0.050 125.0 10.7 104.0 -42.0

3:30 -48.5 19.0 0.050 123.0 10.2 105.0 -43.3

4:00 -50.2 19.0 0.050 1 19.0 10.6 105.0 -43.2

4:30 -50.0 19.0 0.040 125.0 9.0 1 1 1.0 -44.0

5:00 -50.2 19.0 0.040 120.0 6.2 101.0 -45.1 The above results are shown in Fig. 2 as the internal temperature change with respect to the operating time.

As shown in Fig. 2, when four capillary tubes are closed sequentially according to the internal temperature and the flow rate and pressure of the refrigerant are controlled according to the internal temperature, the internal temperature of the room-temperature force rapidly decreases and the rise is extremely high. I understand that it is big. This large rise, coupled with the short time required to reach the steady operating temperature of _50 ° C, indicates that the response to temperature changes is rapid.

For changes in temperature from the set temperature due to loading and unloading in the steady operation, the inner wall of the container and the storage in the frozen state are already at the set temperature. The greatly elevated interior atmosphere and new contents are subject to cooling. Therefore, the cooling load from the viewpoint of heat capacity is relatively small, but the cooling temperature range is large, and the refrigeration system of the present invention that has a quick response to the temperature change in the refrigerator has the contents in such a freezer. It is possible to quickly return to the steady operating temperature with respect to temperature changes caused by taking in and out, etc., and it is also suitable for the actual usage of the freezer.

Claims

The scope of the claims

[1] In a single-stage refrigerator using a non-azeotropic refrigerant that performs heat exchange between a compressor, a condenser, an evaporator, and a return refrigerant from the evaporator and a high-pressure refrigerant from the condenser to the evaporator.

The refrigerant gas pressure and flow rate can be adjusted according to the opening of the evaporator expansion valve. At the time of start-up or in the state where condensation of low boiling components with high internal temperature does not proceed, the evaporator expansion valve is opened to increase the boiling point. Maintaining the pressure according to the condensing conditions of the components to improve the cooling capacity by the high boiling point components,

As the internal temperature decreases and condensation of low boiling point components proceeds,

A refrigeration system using a non-azeotropic refrigerant, wherein the expansion valve of the evaporator is throttled so that the pressure satisfies the condensation conditions of the low-boiling components in order to achieve a steady operation state.

[2] The refrigerator using the non-azeotropic refrigerant according to claim 1, wherein a plurality of capillary tubes are provided in parallel as expansion valves of the evaporator, and the flow rate is controlled by the number of opening and closing of the tubes. .