JPS587903B2 - Reitou Sochi - Google Patents

Description

Detailed Description of the Invention The present invention maintains the dryness of the refrigerant at the outlet of the evaporator at an appropriate value, and effectively utilizes the evaporator with a high heat transfer rate over almost the entire heat transfer area. The present invention relates to a refrigeration system that can be made smaller and can prevent compressor damage accidents caused by liquid backflow.

Conventionally, various refrigerant control methods have been proposed and put into practical use in refrigeration equipment to control the refrigerant flow rate according to load fluctuations, but one of the representative methods is the evaporator control method to prevent liquid back to the compressor. There is a method in which the degree of superheating at the outlet is set to 5°C.

This system has the disadvantage that the evaporator becomes large because it is not possible to operate the evaporator with a high heat transfer coefficient over substantially the entire heat transfer area for the following reason.

In other words, the heat transfer coefficient with respect to dryness in the evaporator is
The heat transfer coefficient is high while a thin refrigerant liquid film is formed on the inner circumferential wall in the cooling pipe of the evaporator, that is, when the dryness is between 0.3 and 0.9, but when the dryness exceeds 0.9. Most of the refrigerant is gasified, and a refrigerant liquid film is not formed on the inner peripheral wall surface, resulting in a state in which the refrigerant gas comes into contact with the inner peripheral wall surface, and the heat transfer coefficient suddenly decreases.

Therefore, the ability of some of the evaporators (approximately 20% of the total heat transfer area) that is provided from a dryness level of 0.9 to a predetermined superheat degree is the ability to be demonstrated when the dryness level is between 0.3 and 0.9. The heat transfer coefficient is extremely small due to the rapid decrease compared to the above-mentioned heat transfer coefficient.
Since the above-mentioned approximately 20% portion does not operate effectively and only approximately 80% of the remaining total heat transfer area can be effectively utilized, the evaporator becomes larger by that amount.

In order to overcome this drawback, it would be possible to control the evaporator outlet to a wet state, but conventional devices could not control the humidity for the following reasons.

In other words, a temperature-sensitive tube was attached to the suction pipe through which the entire amount of refrigerant evaporated in the evaporator flows, and the expansion valve is structured so that it will not open unless the degree of superheat is set to 0°C or higher. Therefore, it was not possible to control the evaporator outlet to a wet state.

The structure of the expansion valve will be briefly explained below.The expansion valve uses a diaphragm to partition the diaphragm chamber into two upper and lower chambers, and the pressure P1 of the temperature-sensitive cylinder applied to this upper chamber (acts in the direction of opening the valve).
When the resultant force (P2+P3) of the pressure P2 of the pressure equalizing pipe applied to the lower chamber and the pressure P3 of the superheat setting spring (acting in the direction of closing the valve) is balanced, the valve is maintained at a predetermined opening degree. It has become.

For example, if the spring pressure P3 is set so that the degree of superheat is 5°C, when the degree of superheat of the refrigerant flowing through the suction pipe on the evaporator outlet side is 5°C, P1 = P2 + P3, and the expansion valve is set to the specified valve. It is maintained at the open position and an appropriate amount of refrigerant is supplied to the evaporator.

On the other hand, when the degree of superheat of the refrigerant in the suction pipe is 0° C. or less, that is, when the liquid and gas are mixed in a wet state, the relationship between the pressure of the temperature sensing cylinder and the evaporation pressure becomes P1=P2.

Therefore, P1<P2+P3 as a whole.

That is, in the conventional device, when attempting to moisten the refrigerant flowing through the suction pipe, the expansion valve becomes closed.

Therefore, refrigerant no longer flows from the expansion valve to the evaporator, making operation impossible.

On the other hand, in order to flow the refrigerant to the evaporator in a wet state, it is sufficient to remove the superheat degree setting spring and set the expansion valve to the open state. However, in this case, even if the degree of dryness is 0.3, Even in the case of 0.9, the evaporation pressure on the Mollier diagram and the evaporation pressure corresponding to the evaporation temperature are the same, so the opening degree of the expansion valve is constant and the flow rate cannot be adjusted.

Therefore, in any case, the conventional apparatus could not control the refrigerant at the evaporator outlet to an appropriate wet state.

Apart from such a control method, there is also a method in which the expansion valve is adjusted depending on the degree of subcooling at the condenser outlet.

Since this is a secondary control with respect to fluctuations in the evaporator load, there is a problem in that the state of the evaporator outlet gas fluctuates.

Moreover, since this is a control method that seals the condenser outlet and expansion valve inlet with supercooled liquid, it is not possible to install a liquid receiver in the liquid pipe, and therefore it is necessary to adjust the refrigerant amount with an accumulator in the low pressure line. However, there was a drawback that the liquid returned to the compressor.

In view of the above facts, the present invention has been made with the aim of providing a highly stable and economical refrigeration system that can eliminate all the drawbacks of conventional refrigeration systems of this type. For example, the amount of heat exchanged in one pass of an evaporator with a refrigerant branch channel can be increased compared to other passes by increasing the heat exchange area, reducing the flow rate, or exchanging heat with a fluid at a higher temperature than the low-pressure refrigerant. The refrigerant before merging is superheated at the outlet of the first pass, and the degree of opening of the expansion valve is adjusted according to the degree of superheating, so that the dryness of the evaporator outlet can be maintained at a substantially constant level. In addition to controlling the refrigerant branch channels other than the first path to a wet state,
A heat exchange coil is provided in the lower part of the accumulator in the middle of the refrigerant pipe connecting the condenser and the expansion valve to heat and evaporate the low-pressure liquid refrigerant and return dry saturated gas to the compressor. Features.

Further, the present invention will be described with reference to specific embodiments shown in the accompanying drawings.

FIG. 1 is a refrigeration circuit diagram relating to the apparatus of the present invention, in which 1 is a compressor, 2 is a condenser, 3 is a liquid receiver, 4 is an expansion valve, 5 is an evaporator,
Reference numeral 6 indicates a heat exchanger type accumulation rake, and these are formed into the circulation circuit shown in the figure, and heat is radiated to the outdoor air in the condenser 2.
The evaporator 5 absorbs heat from the indoor air.

The accumulator 6 has a U-shaped outlet pipe 6c connected to the suction pipe of the compressor 1, and is erected so that its inlet opens at the upper part of the container body 6a. An oil suction hole and a pressure equalization hole are provided facing the gas phase and gas phase, respectively.

The accumulator 6 has an inlet pipe 6b opened at the top of the main body connected to the evaporator 5, and a heat exchange coil 7 as a heating device installed horizontally in the lower part of the vessel. It is inserted in the middle of a liquid pipe that communicates the outlet of the liquid receiver 3 and the expansion valve 4.

Reference numeral 8 denotes a temperature-sensitive tube for controlling the opening degree of the expansion valve 4, and its placement position is a feature of the present invention, and will be explained below together with the structure of the evaporator 5.

First, the evaporator 5 shown in FIG. 1 is a cross-fin coil type heat exchanger, in which heat exchange tubes are connected in parallel between an inlet side divider and an outlet side header for merging, and multiple paths of refrigerant are generated. A branch channel is formed.

One refrigerant branch channel of the plurality of paths is formed longer than the other refrigerant branch channels, and this length is determined by the heat exchange amount of this one refrigerant branch channel (i.e., the amount of heat exchanged per refrigerant 1 to the surrounding objects to be cooled). The refrigerant at the outlet is determined so that the amount of heat (kcal) transferred from the air (for example, air) is larger than the amount of heat exchanged in other refrigerant branch channels, and the refrigerant at the outlet is in a superheated state.

In order to sense the temperature of the refrigerant in this superheated state, a temperature-sensing tube 8 is disposed at the outlet of the one refrigerant branch flow path up to the outflow side header before merging.

Next, the evaporator 5-1 shown in Fig. 2 is a cross-fin coil type heat exchanger, and heat exchange tubes are connected in parallel between an inlet side flow divider 9a and an outlet side header 9b to form a multiple path refrigerant branch flow path. It is a heat exchanger.

In this embodiment, one refrigerant branch flow path 9c is different from the others, and a heating heater is placed at the inlet immediately after the flow divider 9a.
0 is installed.

Further, the evaporator 5-2 shown in FIG. 3A is formed of a cross-fin coil heat exchanger of the same form as that in FIG. 2, and the evaporator 5-2 shown in FIG. By inserting the resistance tube 11, the refrigerant flow rate is made smaller than in other refrigerant branch channels.

Furthermore, the evaporator 5-3 shown in FIG.
In this configuration, a heating heater 10 is installed on the downstream side of "c" for heat exchange, and the heat generated by the heater 10 brings the refrigerant into a superheated state.

In each of the above examples, by configuring one refrigerant branch passage to increase the amount of heat exchange compared to other refrigerant branch passages,
The structure has various special configurations to overheat the refrigerant at the outlet of the one refrigerant branch flow path.

Of course, all of these are evaporators according to the device of the present invention, but in addition to these examples, one refrigerant branch channel of the evaporator 5 may have a smaller fin pitch to increase the heat absorption area, or Various modifications such as increasing the length of the branch pipe from the vessel are possible, and such modifications are naturally included in the present invention.

The structure of the device of the present invention is as described above, and its operation will now be described with reference to FIGS. 1 and 2.

In the illustrated cooling cycle, the discharge gas 11 passes through the discharge pipe and flows as indicated by the solid line arrow, and exchanges heat with the outside air in the condenser 2, becoming a saturated refrigerant i2 in a flash state with a degree of dryness of 0.05, which is then received. It is temporarily stored in container 3.

Thereafter, in the heat exchange coil 7 section in the accumulator 6, heat is exchanged with the low-pressure refrigerant liquid and supercooled.

This subcooled refrigerant i3 is depressurized and expanded in the expansion valve 4 to become a low-temperature, low-pressure refrigerant i4, and then reaches the evaporator 5 and evaporates.

After merging at the outlet header of the evaporator 5, the refrigerant 17 at the outlet of the evaporator 5 becomes a wet refrigerant with a degree of dryness X≈0.85.

This wet refrigerant 17 is transferred to the heat exchange coil 7 in the accumulator 6.
After exchanging heat with the high-pressure refrigerant 12 inside to become dry saturated gas i8, it is sucked into the compressor 1.

Although the above refrigerant flow is repeated, the device of the present invention is capable of regulating the degree of superheating of the outlet refrigerant in one refrigerant branch flow path of the evaporator 5 to a set value, and the By adjusting the expansion valve 4 in accordance with a control command from the attached temperature-sensitive tube 8, the refrigerant at the outlet of the evaporator 5 after merging at the outlet header is controlled to be in a wet state.

For example, a process in which the outlet refrigerant can be controlled to dryness X=0.85 will be described below.

First, during normal cooling operation, the liquid refrigerant whose pressure has been reduced by the expansion valve 4 is divided into the refrigerant branch channels of each path of the evaporator 5 by the flow divider.

In one refrigerant branch passage formed longer than the other refrigerant branch passages, the low-pressure liquid refrigerant exchanges heat with indoor air and evaporates from the liquid refrigerant to a gas refrigerant (dryness 0→1.0).

Next, this gas refrigerant is heated until the degree of superheat reaches 5° C., and then flows into the outflow side header.

On the other hand, in the other refrigerant branch channels formed shorter than the one refrigerant branch channel, the refrigerant evaporates so that the degree of dryness changes from 0 to 0.84.

After this wet refrigerant flows into the outflow header, it joins and mixes with the superheated gas, and after joining, the dryness is 0.8.
It flows through the suction pipe in a wet state of 5.

Next, when the room temperature rises, the dryness of the refrigerant in the suction pipe increases from 0.85 to 0.88.

In this case, the degree of superheating of the gas refrigerant from the outlet of the one refrigerant branch flow path to the outflow side header increases from 5°C to 10°C,
At the outlet of other refrigerant branch channels, it increases from 0.84 to 0.87.

When the thermosensor tube 8 senses the 10° C. increase in superheating degree, the opening degree of the expansion valve 4 increases, and the amount of liquid refrigerant to be divided into each refrigerant branch flow path of the evaporator 5 increases.

In this way, the degree of superheating of the refrigerant in the one refrigerant branch passage returns from 10°C to 5°C, and the degree of dryness of the refrigerant in each of the other refrigerant branch passages also returns from 0.87 to 0.84.

Then, the degree of dryness after merging returns to 0.85, and the valve opening of the expansion valve 4 remains stable and operation continues.

As described above, by controlling the refrigerant at the evaporator outlet to a wet state with a dryness of 0.85, it is possible to utilize the portion with a high heat transfer coefficient over almost the entire heat transfer area of the evaporator 5. It is possible to measure ability improvement.

Note that the refrigerant 17 at the outlet of the evaporator 5 becomes a wet gas state with a dryness of
After being heated and evaporated by the high-pressure refrigerant in a, it becomes a dry saturated gas (1 in X) and is sucked into the compressor 1.

On the contrary, when the indoor air decreases, the evaporation pressure of the evaporator 5 decreases, and the dryness of the outlet refrigerant 17 becomes X<0.85.

Therefore, the degree of superheating of the refrigerant i5 in the attached part of the thermosensor tube 8 ranges from 5°C to 1°C.
The temperature drops to ℃.

This is detected by the temperature sensing tube 8, and the expansion valve 4 is throttled in order to return the superheat degree from 1°C to 5°C.

Therefore, the amount of liquid refrigerant supplied to the evaporator 5 decreases.

Therefore, the refrigerant 17 leaving the evaporator 5 returns to a wet gas with a dryness of 0.85.

In this state, the opening degree of the expansion valve 4 is stabilized.

In this way, the dryness of the evaporator 5 outlet refrigerant 17 is X≒0.8
5, the amount of refrigerant flowing into the accumulator 6 decreases, the liquid level is maintained at the set level, and after being heated and evaporated by the high-pressure refrigerant inside the container 6a, dry saturated gas (X≒ 1) and is sucked into the compressor 1.

In this way, the outlet of the evaporator 5 can be kept in a wet state regardless of whether the refrigeration load is overloaded or light.

As described above, the present invention provides a refrigeration system including a compressor 1, a condenser 2, an expansion valve 4 having a temperature-sensitive cylinder 8, an evaporator 5, and an accumulator 6, in which the condenser 2 is disposed below the inside of the accumulator 6. A heat exchange coil 7 formed in the middle of the refrigerant pipe connecting the and expansion valve 4 is provided to heat and evaporate the low-pressure liquid refrigerant, while the evaporator 5 is replaced by a heat exchanger having multiple paths of refrigerant branch channels in parallel. and forming the heat exchange amount of one refrigerant branch channel in the plurality of passes to be larger than the heat exchange amount of the other refrigerant branch channel, and before merging at the outlet of the one refrigerant branch channel. By disposing the temperature sensing tube 8 and superheating the refrigerant before merging at the outlet of the one refrigerant branch flow path, and adjusting the opening degree of the expansion valve 4 according to this degree of superheating, the other refrigerant can be heated. The refrigerant branch flow path of the evaporator 5 is controlled to be in a moist state, and the outlet of the evaporator 5 after the merging is controlled to be in a constant moist state, so that the evaporator 5 maintains a high heat transfer coefficient over almost the entire heat transfer area. can be used effectively.

In other words, in the case of a conventional device, for example, in the case of an evaporator having four passes of refrigerant branch channels, the degree of superheat is determined in all four passes of the refrigerant branch channels, but in this device, the degree of superheat is determined by the four passes of refrigerant branch channels. This is a configuration in which the degree of superheat is determined by only one refrigerant branch channel among the branch channels.

Therefore, this device can keep the other three refrigerant branch channels in a wet state up to the outlet, and the evaporator outlet after the merging can be in a wet state.

Therefore, in this device, heat exchange can be performed with a high heat transfer coefficient from the inlet to the outlet of the other refrigerant branch channels except for one refrigerant branch channel.

In this way, the heat exchanger tube part of the evaporator, which was conventionally used to control the degree of superheating, has been improved so that it can effectively exchange heat while maintaining a high heat transfer coefficient, so it can now achieve the same level of performance. Compared to the conventional method, the evaporator can be made smaller by the increase in capacity, resulting in cost reduction and downsizing.

Furthermore, the wet refrigerant at the outlet of the evaporator 5 is separated into liquid gas by the accumulator 6, and the liquid refrigerant is heated and evaporated by the heat exchange coil 7, thereby controlling the dry saturated gas to be returned to the compressor 1. Can be done.

Therefore, damage accidents caused by liquid backing into the compressor can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a piping system diagram of a reference refrigeration circuit according to the device of the present invention;
2 is a schematic structural diagram of the evaporator in FIG. 1; FIG. 3A is a schematic structural diagram of an evaporator according to another embodiment of the present invention;
The opening of the drawing is an enlarged sectional view of the main part in FIG. 3A, and FIG. 4 is a piping system diagram according to an example of the apparatus of the present invention. 1... Compressor, 2... Condenser, 4... Expansion valve, 5... Evaporator, 6... Accumulator, 8... Temperature sensing cylinder.

Claims (1)

[Claims] 1 Compressor 1, condenser 2, expansion valve 4 having a temperature-sensitive cylinder 8,
In a refrigeration system consisting of an evaporator 5 and an accumulator 6, a heat exchange coil 7 formed in the middle of a refrigerant pipe connecting the condenser 2 and the expansion valve 4 is provided below the inside of the accumulation rake 6, and a heat exchange coil 7 is provided in the middle of a refrigerant pipe connecting the condenser 2 and the expansion valve 4. While heating and evaporating,
The evaporator 5 is formed as a heat exchanger having multiple refrigerant branch channels in parallel, and the heat exchange amount in one refrigerant branch channel in the plurality of passes is compared to the heat exchange amount in the other refrigerant branch channels. At the same time, the temperature-sensing tube 8 is disposed at the outlet of the one refrigerant branch flow path before the merging, so that the refrigerant before the merging at the outlet of the one refrigerant branch flow is superheated. By adjusting the opening degree of the expansion valve 4 according to the temperature, the other refrigerant branch flow path is controlled to be in a wet state, and the refrigerant at the outlet of the evaporator 5 after merging is controlled to be in a substantially constant wet state. A refrigeration device characterized by: