JPH1019389A - Controlling equipment of degree of superheating of capillary tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To meet an increase and decrease of the degree of superheating, by providing a heat pipe whereby a first vessel so provided that it can exchange heat with a capillary tube and a second vessel so provided that it can exchange heat with an evaporator outlet pipe are made to communicate with each other and by providing a third vessel so that a branch pipe branching from an outlet of the capillary tube can exchange heat with the evaporator outlet pipe. SOLUTION: A first vessel 5 is so provided as to enclose a capillary tube 3. A second vessel 7 is provided in a state of being in contact with an evaporator outlet pipe 6 so that it can exchange heat with this pipe. A first connecting pipe 8 making the first vessel 5 and the second vessel 1 communicate with each other in the upper parts thereof is provided. This pipe is put in a hermetically sealed state and a medium is sealed therein so that a heat pipe 10 be constructed. Besides, a branch part 12 for a refrigerant is provided at an outlet part 11 of the capillary part 3, i.e., an inlet part of an evaporator, and it is connected, by a second connecting pipe 14, with the lower part of a third vessel 13 so provided as to enclose the evaporator outlet pipe 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to superheat control using a capillary tube which is a fixed throttle for decompression and expansion of a medium used in a small freezing and refrigeration system such as a home refrigerator and vending machine. Related to the device.

[0002]

2. Description of the Related Art Conventionally, in a small-sized freezing and refrigeration system used for a home refrigerator or a vending machine, a capillary tube as a fixed throttle is used as an inexpensive refrigerant decompression and expansion device. As shown in FIG. 5, the refrigeration circuit using the capillary tube sends the refrigerant sent from the compressor 31 through the condenser 32 to the capillary tube 33, decompresses and expands the refrigerant, and divides the refrigerant into the evaporator 3
4 to perform a freezing and cooling operation, and return to the compressor 31.

In a refrigeration system using such a capillary tube, the flow rate of the refrigerant sent to the evaporator is:
Basically, it is determined by the inner diameter of the capillary tube and the length of the capillary tube, and the self-controllable flow rate fluctuation is determined by the amount of refrigerant charged into the device, the condensation pressure, and the degree of subcooling at the capillary tube inlet. Once determined, this system does not allow for evaporative pressure or intrinsic evaporator control.

[0004]

In a refrigeration system using a capillary tube as described above, the inherent control of the evaporator cannot be performed, and the flow rate cannot be controlled under load conditions or the like. In a refrigeration system using tubes, the temperature of the condenser,
It is desirable to control the flow rate in response to changes in the evaporator outlet temperature, so that the condenser is in a supercooled state and the evaporator outlet temperature returns to the compressor in a moderately overheated state. It is.

[0006] As a countermeasure, as shown in FIG.
And a refrigerating device has been proposed in which the branch pipe 36 is communicated to the bottom of an evaporator outlet pipe that connects the evaporator 34 and the compressor, that is, the refrigerant amount adjusting container 38 provided so as to surround the suction pipe 37. I have. In this refrigeration apparatus, when the load is reduced and the evaporator outlet temperature is reduced, the refrigerant is condensed in the refrigerant amount adjusting container 38 due to the lowering of the suction pipe 37, the circulating refrigerant amount is reduced, and the refrigerant at the inlet of the capillary tube 33 is reduced. Because the degree of supercooling also decreases, the flow rate of the refrigerant passing through the capillary tube decreases, and the flow rate of the refrigerant corresponding to the decrease in the load is controlled.When the load increases, the flow rate of the refrigerant is controlled by the operation opposite to the above, The flow rate of the refrigerant corresponding to the load is controlled.

In the apparatus shown in FIG. 6, the inside of the refrigerant amount adjusting container 38 is usually occupied by the liquid refrigerant, so that it hardly performs the function of adjusting the refrigerant amount with respect to the normal load fluctuation, and particularly the low load state. In order to eliminate the disadvantage that a liquid bag sometimes occurs in the compressor, a refrigerating apparatus described in Japanese Patent Publication No. 62-40631 as shown in FIG. 7 has been proposed. In this refrigeration apparatus, the basic configuration is the same as that of the apparatus shown in FIG. 6, and a pipe 39 connecting the condenser 32 and the capillary tube 33 is penetrated into the refrigerant amount adjustment container 38, and the inside of the refrigerant amount adjustment container 38 Is controlled by the temperature of both the suction pipe 37 and the pipe 39.

In this device, the amount of refrigerant that can be stored in the refrigerant amount adjusting container can be arbitrarily selected at the time of the design load condition by the above configuration. The size of the refrigerant amount adjusting container is determined so that the amount adjusting function can be performed. In particular, by adjusting the amount of the refrigerant at a low load, it is possible to prevent the liquid from returning to the compressor.

However, in the above-mentioned apparatus, since the take-out part 35 of the refrigerant amount adjusting container is located at the intermediate position of the capillary tube, not only the drawback that the state of the refrigerant becomes unstable, but also the device is controlled by the temperature of the refrigerant amount adjusting container. Since the amount of circulating refrigerant is controlled, the degree of superheat at the evaporator outlet is not controlled. Further, in this apparatus, control is performed in a direction to decrease the degree of subcooling of the refrigerant at the inlet of the capillary tube, but control in the reverse direction is insufficient.

As another countermeasure, in a refrigeration system using a capillary tube, a heat exchanger for cooling the capillary tube, a control valve, and a control valve, utilizing the fact that the flow rate varies depending on the degree of subcooling at the inlet of the capillary tube. It has been proposed to control the evaporator by a microcomputer using a sensor for detecting the degree of superheat, but such a device can only cope with the limited flow rate control region of the capillary tube. However, the use of the above-described apparatus for the effect thereof increases the cost and has a drawback in reliability.

Therefore, the present invention provides a refrigeration circuit using a capillary tube while maintaining its characteristics and reliability by using the capillary tube.
Without using special control equipment, it is possible to feed back the state of the evaporator, which is the original control target in the control of the refrigerant circuit, and it is possible to respond to the increase and decrease of the degree of superheat,
It is an object of the present invention to provide a superheat control device for a capillary tube.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is to control the degree of superheat of a capillary tube of a refrigeration system in which a refrigerant circuit is formed by sequentially connecting a compressor, a condenser, a capillary tube, and an evaporator. The apparatus comprises a heat pipe in which a first container provided for heat exchange with a capillary tube, an evaporator outlet tube, and a second container provided for heat exchange are communicated at the upper portions of both containers, and a medium is sealed therein. A superheat control device for a capillary tube provided with a third container provided with a branch vessel branching from the capillary tube outlet so as to exchange heat with the evaporator outlet tube.

Since the present invention is configured as described above, when the outlet temperature of the capillary tube is lower than the evaporator outlet temperature, that is, in the overheated state, the medium in the heat pipe exchanges heat with the evaporator outlet tube. Evaporates in the second container, condenses and drops into the first container provided with heat exchange with the capillary tube, cools the capillary tube when it accumulates in the first container, and the refrigerant passing through the inside is cooled. It acts in the direction of increasing the refrigerant flow rate. At this time, since the temperature in the third container is high and in an overheated state, if the refrigerant is stored in the third container, the refrigerant returns to the refrigerant circuit from the outlet portion of the capillary tube, and the amount of circulating refrigerant increases to increase synergistically. The cooling effect is increased. When all of the liquid refrigerant in the third container evaporates, the amount of circulating refrigerant no longer changes, but the cooling action by the capillary tube is performed.

On the other hand, when the evaporator outlet temperature is low in the liquid back state, the medium in the heat pipe evaporates in the first container by heat exchange with the capillary tube and can exchange heat with the evaporator outlet tube. Condensed and dropped into the second container provided in
Since the capillary tube is stored in the container, the capillary tube is not cooled and acts in a direction to reduce the flow rate of the refrigerant. At this time, since the temperature in the third container is also low, the refrigerant in the refrigerant circuit is stored in the third container from the outlet of the capillary tube,
The amount of circulating refrigerant decreases, and the cooling action decreases synergistically. When the entire medium in the first container evaporates, the cooling action on the capillary tube is lost, but the refrigerant is stored in the third container.

[0014]

Embodiments of the present invention will be described with reference to the drawings. The basic configuration of the refrigeration circuit is the same as that of the conventional one shown in FIG. 5, and the refrigerant from the compressor 1 passes through the condenser 2, the capillary tube 3, and the evaporator 4 and returns to the compressor 1 through the refrigerant circuit. Have.

On the other hand, as shown in FIG. 1, a first container 5 is provided so as to surround the capillary tube 3, and a second container 7 is provided in contact with the evaporator outlet pipe 6 so as to be able to exchange heat. A first connection pipe 8 that connects the first container 5 and the second container 7 to each other at the upper portion thereof is provided to be in a sealed state, and a medium is sealed therein to constitute a heat pipe 10. CF ₃ CHCl ₂ (refrigerant number R-12)
3), such as CF ₃ CH ₂ F (refrigerant number R-134a),
A refrigerant having a larger specific volume and a larger latent heat than the working refrigerant is sealed. Further, the amount of the medium forming the heat pipe is set to be smaller than the inner volumes of the first container 5 and the second container 7. The first container does not need to surround the entire capillary tube 3, and it is sufficient that the first container can exchange heat with at least a part thereof.

The outlet portion 1 of the capillary tube 3
1, that is, a refrigerant branch portion 12 is provided at the evaporator inlet portion,
In the figure, a lower portion of a third container 13 provided so as to surround the evaporator outlet pipe 6 is connected to a second connecting pipe 14. The third container 13 does not necessarily need to be provided so as to surround the evaporator outlet pipe 6, and it is sufficient that the third container 13 is at least in a heat exchange state. Further, the volume of the third container 13 is set to be larger than the volume of the refrigerant condensed in the condenser. This portion has the same configuration as the conventional one shown in FIG. 6, except that the branch portion 12 is provided at the outlet of the capillary tube 3.

In such a refrigeration circuit using a capillary tube, the length and the inner diameter of the capillary tube are kept constant, and the state when the outside air temperature changes is changed to Pc ₁ , Pc ₂ , Pc _{3 in} ascending order of the outside air temperature. Is displayed,
The flow rate characteristic as shown in FIG. 4 is shown, and as the degree of supercooling ΔT of the refrigerant at the inlet of the capillary tube increases, the flow rate G of the refrigerant flowing therethrough tends to increase, and the pressure Pc at the capillary tube inlet, which is the condenser outlet pressure. Is larger, the flow rate flowing therethrough tends to increase.

In the apparatus having the above-mentioned structure, when the refrigerant in the evaporator outlet pipe 6 is overheated, that is, when the capillary tube outlet temperature, ie, the evaporator inlet temperature TE is lower than the evaporator outlet temperature TS, FIG. As described above, the medium in the heat pipe 10 is cooled and condensed at the outlet temperature TE of the capillary tube 3 which is the lowest temperature part, and drops and accumulates in the first container 5. By repeating this cycle, the capillary tube 3 is cooled, the degree of supercooling of the refrigerant for refrigeration passing therethrough increases, and as described above, the larger the degree of supercooling of the refrigerant, the more the flow rate of the refrigerant flowing through the capillary tube increases. As a result, the flow rate of the refrigerant increases, and the cooling action increases.

In the process of the overheating, the third
When the refrigerant is stored in the container, the refrigerant returns from the capillary tube outlet to the refrigerant circuit, and acts in a direction in which the amount of circulating refrigerant increases to increase the degree of supercooling. The cooling effect is increased.
When a complete overheating state is reached, all the liquid refrigerant in the third container evaporates and the amount of circulating refrigerant does not change, but the cooling operation by the heat pipe is performed, and the self-control operation by the capillary tube is continued.

Conversely, when the capillary tube outlet temperature, ie, the evaporator inlet temperature TE is higher than the evaporator outlet temperature TS, that is, in a situation where the liquid is backed up, as shown in FIG. It condenses at the evaporator outlet pipe 6 which is the lowest temperature part, drops and accumulates in the second container 7. By repeating this cycle, the medium accumulates in the second container 7, and the heat recovery in the first container 5 is not performed, and the capillary tube 3 is not cooled, so that the characteristics of the capillary tube and the amount of refrigerant on the condenser side decrease. The reduction in the degree of supercooling due to the above-mentioned effect acts in a direction to reduce the circulation flow rate of the refrigerant. This operation is stopped when all the liquid medium stored in the first container evaporates.

In this state, the temperature in the third container 13 is lower than the temperature of the branch portion 12, and this temperature difference occurs, so that the refrigerant is condensed in the third container 13. For this reason, the circulating refrigerant flow rate of the refrigeration circuit is reduced, the cooling characteristics are reduced, and
The degree of supercooling at the inlet of the capillary tube decreases, and as shown in the flow rate characteristics of the capillary tube, the flow rate of the refrigerant passing through the capillary tube decreases.
Due to this effect, the flow rate can be significantly reduced until the degree of supercooling at which the inlet of the capillary tube becomes a two-phase flow becomes negative from the relationship between the amount of refrigerant charged and the internal volume of the third container. Particularly, the controllability is remarkable in synergy with the action of the heat pipe 10 as described above.

Further, only the heat pipe 10 is used,
When the configuration of the container is not provided, the controllability in the direction of increasing the degree of supercooling of the capillary tube is good, but the controllability in the case of decreasing the degree of reduction is limited. By adding a pipe connected to the branch portion of the outlet, the drawback can be solved, and the heat pipe 10 which solves the drawback of the conventional one shown in FIG.
Combined with the effect of the method using, the disadvantages of both can be mutually compensated.

[0023]

As described above, according to the present invention, in a refrigeration circuit using a capillary tube, while maintaining the characteristics and reliability of using a capillary tube, the refrigerant can be used without using a special control device. The state of the evaporator, which is the primary control target in the control of the circuit, can be fed back, and it is possible to cope with an increase or decrease in the degree of superheat. Further, since the working refrigerant and the sealed refrigerant in the heat pipe are separated, sufficient heat exchange can be performed, and the cooling and start-up of the refrigeration circuit is quick and energy is saved. Furthermore, there is no overcooling when the operation of the refrigeration circuit is stable,
Further, the evaporator and the condenser can be made smaller. In addition, the control range that cannot be sufficiently achieved by using a heat pipe can be compensated for by using a third vessel that is in a heat exchange state with the evaporator outlet pipe and that is branched and connected to the outlet part of the capillary tube. Also, since the third container is branched and connected to the outlet of the capillary tube,
The state of the refrigerant introduced into the third container is stabilized, and its controllability is improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a refrigeration circuit showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a main part showing the first operation state.

FIG. 3 is a cross-sectional view of a main part showing a second operation state.

FIG. 4 is a graph showing operating characteristics of the refrigeration circuit.

FIG. 5 is a configuration diagram of a basic refrigeration circuit using a capillary tube.

FIG. 6 is a refrigeration circuit configuration diagram showing a conventional example.

FIG. 7 is a configuration diagram of a refrigeration circuit showing another conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 2 Condenser 3 Capillary tube 4 Evaporator 5 1st container 6 Evaporator outlet pipe 7 2nd container 8 1st connection pipe 10 Heat pipe 11 Exit part 12 Branch part 13 3rd container 14 2nd connection pipe

Claims (4)

[Claims] 1. A compressor, a condenser, a capillary tube,
In a superheat degree control device for a capillary tube of a refrigerating device in which an evaporator is connected in order to form a refrigerant circuit, a first container provided for heat exchange with the capillary tube and a second container provided for heat exchange with an evaporator outlet tube. A heat pipe in which a medium is enclosed by communicating the containers at the upper portions of the two containers, and a third container in which a branch pipe branched from the capillary tube outlet is provided in the evaporator outlet pipe so as to be heat-exchangeable is provided. Characteristic superheat control device for capillary tube. 2. Inside the heat pipe 10, R-12 is provided.
3. The superheat degree control device for a capillary tube according to claim 1, wherein a refrigerant having a larger specific volume and a larger latent heat than the working refrigerant, such as R-134a, is sealed. 3. The superheat control device for a capillary tube according to claim 1, wherein the amount of the medium forming the heat pipe is set to be smaller than the internal volumes of the first container 5 and the second container 7. 4. The superheat control apparatus for a capillary tube according to claim 1, wherein the volume of the third container is set to be larger than the volume of the refrigerant condensed in the condenser.