JP2003262411A - Refrigerating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerating device capable of preventing refrigerator oil from remaining in an evaporator in a large amount having adverse affect on cooling performance, at reduced running cost. <P>SOLUTION: The refrigerating device 1 has a circulating fluid passage 8 which communicates with a suction opening 2b of a compressor 2 from a discharge opening 2a of the compressor 2 to constitute a refrigerating cycle, with an oil separator 3, a condenser 4, a liquid receiver 5, an expansion valve 6, and an evaporator 7 mounted in the fluid circulation passage 8 in that order. A discharge port 7a through which to discharge the internal liquid is provided in the shell of the evaporator 7 and communicated with the circulating fluid passage 8 via a liquid return line 10 in which a flow control valve 11, a flowmeter 12, and a selector valve 13 are inserted, to return the liquid in the evaporator 7 to the compressor 2. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a refrigerating apparatus, and more particularly, to a large amount of refrigerating machine oil which can be prevented from accumulating in an evaporator and stably exhibit refrigerating performance. The present invention belongs to the technical field of refrigerating devices.

[0002]

2. Description of the Related Art In a refrigerating apparatus having an oil-cooled screw compressor as a compressor, a refrigerant containing refrigerating machine oil is discharged from the oil-cooled screw compressor. If refrigerating machine oil is contained in the refrigerant, it will adversely affect the cooling performance.Therefore, an oil separator is installed between the oil-cooled screw compressor and the condenser, and the refrigerating machine oil is removed by this oil separator. The refrigerant is sent to the condenser.

However, the oil separator alone cannot completely separate the refrigerating machine oil in the refrigerant. Therefore, the refrigerating machine oil that accumulates in the evaporator gradually increases, and the heat exchange efficiency of the evaporator decreases, so that the desired refrigeration performance cannot be exhibited. In order to solve such a problem, a refrigerating apparatus provided with an oil return mechanism for removing a small amount of oil from the refrigerant that has passed through an oil separator is, for example, the Refrigeration and Air Conditioning Handbook (Japan Refrigeration Association), 5th edition (Basic Edition). Year)
Have been proposed in. The outlines of the two proposed examples will be described below.

As shown in FIG. 3 of the schematic system diagram, the refrigerating apparatus according to the conventional example 1 continuously extracts a part of the refrigerant liquid in the low-pressure receiver and supplies it to the low-pressure receiver. The high-pressure liquid is heat-exchanged with a heat exchanger to increase the degree of supercooling of the high-pressure liquid and evaporate the extracted refrigerant liquid. The separated refrigerating machine oil is then returned to the compressor via the suction line at the suction gas velocity. In addition, in this refrigerating apparatus, Freon which dissolves lubricating oil well is used as a refrigerant. For example, in R22, the solubility of oil is different at low temperatures and it is divided into two types of liquid, and the liquid in which a large amount of refrigerating machine oil is dissolved due to the difference in specific gravity tends to collect in the upper layer, so as shown in FIG. The refrigerant liquid is extracted from near the liquid surface of the liquid inside.

In the refrigerating apparatus according to the conventional example 2, as shown in FIG. 4 of the schematic system diagram, the refrigerant containing the oil component accumulated in the low pressure receiver is dropped into the oil reservoir tank, and the oil component in the oil reservoir tank is dropped. The refrigerant containing is overheated by the heater. Then, while the refrigerant is evaporated and sucked into the compressor, only the oil is returned to the compressor by an oil pump. In addition,
In this oil sump tank, in order to completely expel the refrigerant in the oil, it is heated to a temperature of about 40 ° C. Therefore, a part of the liquid refrigerant in the low-pressure receiver is evaporated to remove the superheat of the refrigerant vapor returning from the oil sump tank.

[0006]

It is considered that the refrigerating apparatus according to the above-mentioned conventional example 1 or 2 is useful as such. However, since the refrigerating machine oil cannot be completely removed from the liquid in the low pressure receiver, the refrigerant containing a small amount of refrigerating machine oil flows into the evaporator. Due to the difference in the boiling points of the refrigerating machine oil and the refrigerant, the refrigerating machine oil does not evaporate even though the refrigerant evaporates.Therefore, the amount of the refrigerating machine oil in the evaporator gradually increases with the passage of time, and the initial refrigeration performance is also increased. There is a possibility that the situation will not be achieved.

Further, in the refrigerating apparatus according to the conventional example 1, both the amount of the refrigerant liquid extracted from the low pressure receiver and the amount of the high pressure liquid from the receiver change depending on various factors such as the load condition. , The amount of heat exchanged by each other may also change. Therefore, in order to perform the desired heat exchange, delicate adjustment according to the operating condition of the refrigeration system is required. If the desired heat exchange cannot be achieved and the refrigerant exiting the heat exchanger cannot be completely vaporized, the refrigerant is supplied to the compressor in a so-called liquid back state, which may cause a mechanical failure of the compressor. Absent.

In the refrigerating apparatus according to the second conventional example, since electric power must be supplied to the heater, there is an economical problem that the refrigerating apparatus has a disadvantage in terms of running cost. Further, when this heater is an electric heater, there is a risk of excessive heating that may cause a malfunction to the electric heater itself. If this heater is a steam heater, there is a risk of corrosion due to steam water due to long-term use. In other words, a highly reliable refrigeration system that can avoid various problems is desired.

Therefore, an object of the present invention is to prevent the refrigerating machine oil from having a bad influence on the cooling performance from accumulating in the evaporator so that the initial refrigerating performance can be exhibited, and the running cost is inexpensive and reliable. It is to provide a refrigerating apparatus having high property.

[0010]

The present invention has been made in view of the above circumstances, and therefore, in order to solve the above problems, the means adopted by the refrigerating apparatus according to claim 1 of the present invention is as follows. The discharge port of the compressor communicates with the suction port, and a fluid circulation flow path that constitutes a refrigeration cycle is provided. In the installed refrigeration system, a discharge port for discharging the internal liquid is provided in the body of the evaporator, and the compressor is provided with the discharge port through a liquid return line in which at least an on-off valve is installed. It is characterized in that it is connected to the suction port of.

The means adopted by the refrigerating apparatus according to claim 2 of the present invention is the refrigerating apparatus according to claim 1, wherein the discharge port is provided at a position lower than the liquid surface of the liquid in the evaporator. It is characterized by becoming.

The means adopted by the refrigerating apparatus according to claim 3 of the present invention is the refrigerating apparatus according to any one of claims 1 and 2, wherein a flow meter is provided in the liquid return line. It is characterized in that it is provided with a flow rate control valve which is controlled so that the flow rate of the liquid detected by the flow meter becomes constant.

The means adopted by the refrigerating apparatus according to the fourth aspect of the present invention comprises a fluid circulation passage which communicates from the discharge port of the compressor to the suction port and constitutes a refrigeration cycle. An oil separator, a condenser, a liquid receiver, an expansion means, and an evaporator are provided in this order, and either CO ₂ or NH ₃ is used as a refrigerant, and an oil compatible with the refrigerant is used as a refrigerating machine oil. A refrigeration apparatus to be used, wherein a low-pressure liquid receiver is interposed between the expansion means of the fluid circulation flow path and the evaporator, and the liquid pool portion of the low-pressure liquid receiver of the fluid circulation flow path and the It is characterized in that the evaporator and the evaporator are communicated with the suction port of the compressor through a liquid return line having at least an opening / closing valve.

The means adopted by the refrigerating apparatus according to claim 5 of the present invention is the refrigerating apparatus according to claim 4, wherein the refrigerating machine oil is a polyol ester oil when the refrigerant is CO ₂ . When the refrigerant is NH ₃ , it is a polyalkylene glycol oil.

The means adopted by the refrigerating apparatus according to claim 6 of the present invention is the refrigerating apparatus according to claim 4, wherein a flow meter is provided in the liquid return line and detection is performed by this flow meter. It is characterized in that a flow rate adjusting valve for adjusting the flow rate of the liquid to be kept constant is interposed.

The means adopted by the refrigerating apparatus according to the seventh aspect of the present invention is the refrigerating apparatus according to any one of the fourth to sixth aspects, wherein the evaporator and the evaporator in the fluid circulation passage are provided. It is characterized in that a space between the suction port and the low pressure liquid receiver is provided.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION A refrigerating apparatus according to Embodiment 1 of the present invention will be described below, in which the compressor is an oil-cooled screw compressor, CO ₂ is used as a refrigerant, and polyol ester is used as a refrigerating machine oil. A case will be described with reference to the accompanying drawings. FIG. 1 (a) is a schematic system diagram of the refrigerating apparatus, and FIG. 1 (b) is an explanatory view of the mounting position of the liquid return line to the evaporator.

Reference numeral 1 shown in FIG. 1A indicates the first embodiment.
It is a refrigerating device according to. This refrigeration system 1 is provided with a fluid circulation flow path 8 that forms a refrigeration cycle, which communicates from a discharge port 2a of an oil-cooled screw compressor (hereinafter referred to as a compressor) 2 to a suction port 2b. An oil separator 3, a condenser 4, a liquid receiver 5, an expansion valve 6 as an expansion means, and an evaporator 7 are sequentially provided in the fluid circulation flow path 8 from the discharge port 2a toward the suction port 2b. It is equipped. The oil separator 3 separates and collects the refrigerating machine oil from a mixed fluid composed of the refrigerant discharged from the compressor 2 and the refrigerating machine oil in the form of droplets,
It serves to allow the refrigerant after removing the refrigerating machine oil to flow into the condenser 4.

By the way, the refrigerating machine oil separated by the oil separator 3 is temporarily stored in an oil reservoir 3a formed below the oil separator 3. The refrigerating machine oil stored in the oil sump 3a is supplied to a compression space (not shown) of the compressor 2, a bearing portion that supports the shafts of a pair of male and female screw rotors, and a shaft seal via an oil supply passage (not shown). Is configured to be supplied to the section.

The gaseous refrigerant flowing out of the oil separator 3 flows into the condenser 4, is cooled by heat exchange with the cooling liquid, is condensed, and becomes a liquid refrigerant. The liquid refrigerant flowing out of the condenser 4 is stored in the liquid receiver 5, and the liquid refrigerant flowing out of the liquid receiver 5 is expanded by the expansion valve 6, supercooled and flows into the evaporator 7. The supercooled refrigerant that has flowed into the evaporator 7 exchanges heat with a fluid to be cooled that cools a cooling load (not shown) (not shown), evaporates, and becomes a gaseous refrigerant and flows out of the evaporator 7. . The gaseous refrigerant flowing out from the evaporator 7 is sucked into the suction port 2a.
Is sucked into the compression space in the compressor 2 and compressed, so as to circulate in the fluid circulation flow path 8 to exert a refrigerating function.

Further, the body of the evaporator 7 is provided with a discharge port 7a for discharging the liquid in the evaporator 7, that is, the liquid refrigerant. As shown in FIG. 1B, the position where the discharge port 7a is provided is lower than the liquid level of the refrigerant inside the evaporator 7, and the liquid head inside the evaporator 7 is changed by the difference in the liquid head of the refrigerant. The refrigerant is configured to be discharged from the discharge port 7a.

From the discharge port 7a of the evaporator 7, it is possible to discharge a refrigerant having a high refrigerating machine oil content. The refrigerant in the evaporator 7 contains a large amount of refrigerating machine oil for the following reason. That is, as described above, the refrigerant flows from the oil recovery device 3 into the evaporator 7, but the oil separator 3
The refrigerant flowing out from the tank contains a very small amount of refrigerating machine oil, specifically, a very small amount of refrigerating machine oil of usually 100 to 200 ppm. This is because the refrigerating machine oil and the refrigerant gas are incompatible and are separated from each other, so that the amount of refrigerating machine oil accumulated in the evaporator 7 gradually increases.

It is known that when the content ratio of refrigerating machine oil in the refrigerant exceeds 4%, the cooling performance of the evaporator 7 deteriorates. Therefore, in the case of the refrigerating apparatus 1 according to the first embodiment, the refrigerating machine oil content is set to 10% or less so as to be 2% or less.
Refrigerant liquid containing refrigerating machine oil is discharged while supplementing the refrigerant containing 0 to 200 ppm of refrigerating machine oil. By the way, the content of the refrigerating machine oil in the refrigerant flowing out from the oil separator 3 is known as described above. Therefore, the content ratio of the refrigerating machine oil in the refrigerant in the evaporator 7 can be derived from the operating time of the refrigerating apparatus, the capacity of the refrigerant in the evaporator 7 and the drainage amount.

Further, a liquid return line 10 is provided between the discharge port 7a and the evaporator 7 of the fluid circulation passage 8 and the suction port 2b of the compressor 2. The liquid return line 10 is provided with a flow rate control valve 11, a flow meter 12, and an opening / closing valve 13 in this order from the discharge port 7a side toward the communication section side with the fluid circulation flow path 8. The opening degree of the flow rate control valve 11 is controlled by a controller (not shown) so that the flow rate of the liquid detected by the flow meter 12 becomes constant. The on-off valve 13 is opened and closed by an electric signal.

In the case of the refrigeration system 1 according to the first embodiment, the liquid return line 10 is connected to the fluid circulation flow path 8, but it should be connected directly to the suction port 2b of the compressor 2. May be. Further, it is more preferable that a peep window (site glass) for monitoring the flow of the liquid is provided in the liquid return line 10 so that the flow condition of the liquid flowing through the liquid return line 10 can be monitored through the peep window.

The use mode of the refrigerating apparatus 1 according to the first embodiment will be described below. As the operating time of the refrigerating apparatus 1 elapses, the inside of the evaporator 7 is changed due to the difference in the boiling points of the refrigerating machine oil and the refrigerant. The content rate of the refrigerating machine oil in the refrigerant is gradually increased. When the content of the refrigerating machine oil in the refrigerant in the evaporator 7 becomes 2% due to the continued operation, the evaporator 7
The discharge amount of the refrigerant within which the content rate of the refrigerating machine oil does not exceed 2% is determined, and the opening / closing valve 13 is opened. When the on-off valve 13 is opened, the operation of the refrigeration system 1 is continued and the discharge port 7 is changed due to the difference in the liquid heads of the refrigerant in the evaporator 7.
The flow rate of the refrigerant flowing out from a is detected by the flow meter 12.

The opening of the flow rate control valve 11 is controlled so that the flow rate of the refrigerant detected by the flow meter 12 is equal to the discharge amount, and a constant amount of refrigerating machine oil is contained per hour via the liquid return line 10. The refrigerant to be discharged continues to be returned to the suction port 2b of the compressor 2. During such discharge of the refrigerant, the liquid receiver 5 is controlled so that the liquid level of the refrigerant in the evaporator 7 becomes constant.
Therefore, the refrigerant containing 100 to 200 ppm of refrigerating machine oil is continuously supplied. When the operation of the refrigeration system 1 is stopped, the on-off valve 13 is closed to protect the refrigeration system 1 and the supply of the refrigerant to the suction port of the compressor 2 is stopped. is there.

According to the refrigerating apparatus 1 according to the first embodiment, as described above, the evaporator 7 is connected to the suction port 2b of the compressor 2.
In addition, a constant amount of the refrigerant liquid containing the refrigerating machine oil can be returned per unit time. Then, it is possible to prevent the content rate of the refrigerating machine oil in the refrigerant in the evaporator 7 from becoming 2% or more. Therefore, the refrigeration apparatus 1 according to the first embodiment
According to the above, the following effects can be obtained. Refrigerant oil content in the refrigerant in the evaporator 7 is 2
% Or less, and the cooling performance is not lowered to 4% or more, so that the desired cooling performance can be continued. Unlike the conventional example, it is not necessary to provide a heat exchanger or a heater, and the structure of the liquid return line is simple. Therefore, the reliability is improved and the running cost of the refrigerating apparatus is also advantageous.

Next, as in the case of the refrigerating apparatus according to the first embodiment, the refrigerating apparatus according to the second embodiment of the present invention will be described with an example in which the compressor is an oil-cooled screw compressor. It will be described with reference to FIG. 2 of the schematic system diagram.
With respect to the configuration, the difference between the second embodiment and the first embodiment is that the low-pressure liquid receiver is provided and the connection position of the base end of the liquid return line is different. . Therefore, the same components as those in the first embodiment and components having the same functions are designated by the same reference numerals, and different points will be described.

The refrigerating apparatus 1 according to the second embodiment also has
The CO ₂ with use as a refrigerant, CO ₂ as refrigerating machine oil
It shows the one using a polyester which is compatible with. In this refrigeration system 1, a low-pressure liquid receiver 14 is provided between the evaporator 7 and the expansion valve 6 which is the expansion means of the fluid circulation flow path 8. Further, a liquid pump 15 is provided between the low pressure liquid receiver 14 and the evaporator 7 of the fluid circulation flow path 8, and the evaporator 7 of the fluid circulation flow path 8 and the suction port of the compressor 2 are installed. 2b and the gas space 14 of the low pressure receiver 14
via b. The gas space 14b of the low-pressure liquid receiver 14 may be configured to communicate with the fluid circulation flow path 8 via a flow path (not shown).

Between the liquid pump 15 and the evaporator 7 in the fluid circulation flow path 8 is a suction port of the evaporator 7 and the compressor 2 in the fluid circulation flow path 8 via a liquid return line 10. It communicates with 2b. In the liquid return line 10, as in the case of the first embodiment, the flow rate control valve 1
1, a flow meter 12, and an open / close valve 13 are provided.

The mode of operation of the refrigerating apparatus 1 according to the second embodiment will be described. That is, the supercooled refrigerant containing the refrigerating machine oil is collected in the liquid pool portion 14a of the low-pressure liquid receiver 14. In this case, the refrigerant is CO _2, and the refrigerating machine oil from poliovirus ester which is compatible with respect to CO _2, the polio ester are uniformly dissolved in CO _2. While such a refrigerant is supplied to the evaporator 7 by driving the liquid pump 15, the refrigerant is continuously returned to the compressor 2 in a predetermined amount via the liquid return line 10, and the polyol ester is continuously recovered in a predetermined amount throughout the operation. .

Therefore, in addition to the CO ₂ having a low concentration of polyester being supplied to the evaporator 7, it may be separated from CO ₂ and accumulated in the evaporator as in the case of an incompatible refrigerating machine oil. Absent. Therefore, since the heat exchange performance of the evaporator 7 is not deteriorated by the polyester, the second embodiment has the same effect as the first embodiment with respect to the stable maintenance of the cooling performance and the like. Furthermore, since CO ₂ existing in nature is used as a refrigerant, it is possible to expect an excellent effect that it can respond to environmental problems, especially social demands such as dechlorofluorocarbon.

In the first and second embodiments, an example in which CO ₂ compatible with polyester is used as a refrigerant has been described, but NH ₃ is used as a refrigerant and an oil compatible with it is used. For example, polyalkylene glycol may be used as refrigerating machine oil.

[0035]

As described in detail above, the first aspect of the present invention
According to the refrigerating apparatus according to any one of 7 to 7, the content of the refrigerating machine oil in the refrigerant does not increase in the evaporator, and for separating the refrigerating machine oil, the heat exchanger and the heater unlike the conventional example. Need not be used. Therefore, the desired cooling performance can be continuously exerted, and the structure of the liquid return line is simple, so that the reliability is improved and the running cost of the refrigeration system is improved.

Further, according to the refrigerating apparatus according to the fourth to seventh aspects of the present invention, in addition to the above effects, NH _{3 which} does not further destroy CO ₂ and the ozone layer existing in nature and contributes little to global warming is NH _3. Because it uses as a refrigerant, environmental problems,
In particular, it can be expected to have an excellent effect of being able to meet the social demand for dechlorofluorocarbons.

[Brief description of drawings]

1 is a schematic system diagram of a refrigerating apparatus according to Embodiment 1 of the present invention, and FIG. 1 (b) is an explanatory view of a mounting position of a liquid return line to an evaporator.

FIG. 2 is a schematic system diagram of a refrigerating apparatus according to Embodiment 2 of the present invention.

FIG. 3 is a schematic system diagram of a refrigeration apparatus according to Conventional Example 1.

FIG. 4 is a schematic system diagram of a refrigerating apparatus according to Conventional Example 2.

[Explanation of symbols]

1 ... Refrigerating device, 2 ... Compressor (oil-cooled screw compressor), 2
a ... Discharge port, 2b ... Suction port, 3 ... Oil separator, 3a ... Oil sump, 4 ... Condenser, 5 ... Liquid receiver, 6 ... Expansion valve, 7 ... Evaporator, 7a ... Discharge port, 8 ... Fluid circulation flow path 10 ... Liquid return line, 11 ... Flow control valve, 12 ... Flow meter, 13 ... Open / close valve, 14 ... Low pressure receiver, 14a ... Liquid reservoir, 14b ... Gas space, 15 ... Liquid pump

Claims (7)

[Claims] 1. A fluid circulation flow path, which communicates from a discharge port of a compressor to a suction port and constitutes a refrigeration cycle, is provided with an oil separator, a condenser, a liquid receiver, an expansion means, In a refrigeration system in which an evaporator is installed in this order, a discharge port for discharging the internal liquid is provided in the body of the evaporator, and the discharge port is provided with a liquid return line including at least an on-off valve. A refrigeration system characterized in that the refrigeration system is communicated with the suction port of the compressor. 2. The refrigerating apparatus according to claim 1, wherein the discharge port is provided at a position lower than a liquid surface of the liquid in the evaporator. 3. The liquid return line is provided with a flow meter and a flow rate control valve which is adjusted so that the flow rate of the liquid detected by the flow meter is constant. The refrigerating apparatus according to any one of claims 1 and 2, characterized in that. 4. A fluid circulation flow path, which communicates from a discharge port of the compressor to a suction port and constitutes a refrigeration cycle, is provided with an oil separator, a condenser, a liquid receiver, an expansion means, An evaporator is interposed in this order, and either CO ₂ or NH ₃ is used as a refrigerant, and an oil compatible with the refrigerant is used as a refrigerating machine oil. A low-pressure liquid receiver is interposed between the expansion means and the evaporator, and at least an on-off valve is interposed between the liquid reservoir of the low-pressure liquid receiver of the fluid circulation channel and the evaporator. A refrigeration system characterized in that it is connected to the suction port of the compressor through a liquid return line. 5. The refrigerating machine oil is a polyester oil when the refrigerant is CO ₂ , and the refrigerant is NH 3.
_When it is ₃ , it is polyalkylene glycol oil, The refrigerating device of Claim 4 characterized by the above-mentioned. 6. The liquid return line is provided with a flow meter and a flow rate control valve that is adjusted so that the flow rate of the liquid detected by the flow meter is constant. The refrigerating apparatus according to claim 4, wherein 7. The gas space of the low-pressure liquid receiver is provided between the evaporator and the suction port of the fluid circulation flow path, according to any one of claims 4 to 6. Refrigerating apparatus according to one of the items.