JP4028994B2 - Refrigeration equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of a refrigeration apparatus. More specifically, the present invention relates to a refrigeration apparatus that prevents a large amount of refrigeration oil from accumulating in an evaporator and enables stable refrigeration performance. It belongs to the technical field.
[0002]
[Prior art]
As a compressor, in the refrigerating device including a oil-cooled subscription Interview compressors, refrigerant containing refrigerating machine oil from the oil-cooled type screw compressor is discharged. If the refrigerant contains refrigeration oil, the cooling performance will be adversely affected, so an oil separator is interposed between the oil-cooled screw compressor and the condenser, and this oil separator removes the refrigeration oil. The refrigerant is sent to the condenser.
[0003]
However, the refrigeration oil in the refrigerant cannot be completely separated only by the oil separator. For this reason, the amount of refrigerating machine oil staying in the evaporator gradually increases and the heat exchange efficiency of the evaporator decreases, so that there is a problem that the intended refrigeration performance cannot be exhibited. In order to solve such a problem, a refrigeration apparatus equipped with an oil return mechanism that removes a small amount of oil from a refrigerant that has passed through an oil separator is, for example, a refrigeration air conditioning manual (Japan Refrigeration Association) Basic Edition 5th edition (1993). Year). The outline of the two proposed examples will be described below.
[0004]
As shown in FIG. 3 of the schematic system diagram of the refrigeration apparatus according to Conventional Example 1, a part of the refrigerant liquid in the low-pressure receiver is continuously extracted, and the high-pressure liquid flowing into the low-pressure receiver Heat is exchanged in a heat exchanger to increase the degree of supercooling of the high-pressure liquid and evaporate the extracted refrigerant liquid. And it is comprised so that the isolate | separated refrigeration oil may be returned to a compressor via a suction line by suction gas speed. In this refrigeration apparatus, chlorofluorocarbon that dissolves lubricating oil well is used as a refrigerant. For example, divided into two types of liquid solubility of the oil that Do different at low temperatures in R22, because the liquid tends gather in the upper layer which is dissolved a number refrigerating machine oil by the difference in specific gravity, as shown in the figure, the low pressure receiver The refrigerant liquid is extracted from near the liquid level of the liquid in the vessel.
[0005]
Refrigerant refrigeration system according to the conventional example 2, as shown in FIG. 4 of the schematic system diagram, darken the sump tank refrigerant containing oil collected in the low pressure receiver, including oil in the oil reservoir tank Overheat with a heater. The refrigerant is evaporated and sucked into the compressor, while only the oil is returned to the compressor by the oil pump. In addition, in this oil sump tank, in order to expel the refrigerant | coolant in oil completely, it heats so that it may become a temperature of about 40 degreeC. Therefore, part of the liquid refrigerant in the low-pressure receiver is evaporated in order to remove the superheated refrigerant vapor returning from the oil reservoir tank.
[0006]
[Problems to be solved by the invention]
Any of the refrigeration apparatuses according to the conventional examples 1 and 2 is considered to be 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 the refrigerating machine oil flows into the evaporator. Even though the refrigerant evaporates due to the difference in boiling point between the refrigerating machine oil and the refrigerant, the refrigerating machine oil does not evaporate. There is a possibility that will not be able to demonstrate.
[0007]
Further, in the refrigeration apparatus according to Conventional Example 1, the amount of refrigerant liquid extracted from the low-pressure receiver and the amount of high-pressure liquid from the receiver also change depending on various factors such as the load state. The amount of heat exchanged may also change. Therefore, in order to perform desired heat exchange, delicate adjustments according to the operating conditions of the refrigeration apparatus are 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 in the compressor. Absent.
[0008]
In the refrigeration apparatus according to Conventional Example 2, since power must be supplied to the heater, there is an economic problem that the running cost of the refrigeration apparatus is disadvantageous. Further, when this heater is an electric heater, there is a risk of overheating that is more than necessary, which would cause problems with the electric heater itself. Further, when this heater is a steam heater, there is a risk of corrosion due to steam water associated with long-term use. That is, a highly reliable refrigeration apparatus that can avoid various problems is desired.
[0009]
Therefore, the object of the present invention is to prevent the refrigerating machine oil that has an adverse effect on the cooling performance from staying in the evaporator and to exert the initial refrigerating performance, and at a low running cost and high in reliability. It is to provide a refrigeration apparatus.
[0010]
[Means for Solving the Problems]
The present invention has been made in view of the above circumstances. Therefore, in order to solve the above problems, the means adopted by the refrigeration apparatus according to claim 1 of the present invention is from the discharge port of the compressor to the suction port. In a refrigeration system comprising a fluid circulation flow path composing a refrigeration cycle, and an oil separator, a condenser, a liquid receiver, an expansion means, and an evaporator interposed in this fluid circulation flow path in this order. a body of the evaporator, and a lower position than the liquid level of the liquid in the evaporator is provided with a discharge port for discharging the internal liquid of the evaporator, the discharge port, opening closed, the flow rate And a fluid return line in which a flow rate adjusting valve for adjusting the flow rate of the liquid detected by the flow meter to be constant is communicated with the suction port of the compressor. To do.
[0011]
The means adopted by the refrigeration apparatus according to claim 2 of the present invention includes a fluid circulation passage that communicates from the discharge port of the compressor to the suction port and forms a refrigeration cycle, and an oil separator is provided in the fluid circulation passage. , A condenser, a liquid receiver, an expansion means, and an evaporator are disposed in this order, and one of CO _{2 and} NH ₃ is used as a refrigerant, and an oil having compatibility with the refrigerant is used as a refrigerator oil. A low-pressure receiver is interposed between the expansion means of the fluid circulation channel and the evaporator, and the reservoir of the low-pressure receiver of the fluid circulation channel and the evaporator And the suction of the compressor through a liquid return line in which an on-off valve, a flow meter, and a flow rate adjusting valve for adjusting the flow rate of the liquid detected by the flow meter to be constant are interposed. It is characterized by having communicated with the mouth .
[0012]
Means for refrigeration system is adopted according to claim 3 of the present invention is the refrigeration apparatus of the mounting serial to claim 2, between the evaporator and the inlet of the fluid circulation passage, said low pressure receiver It is characterized by being formed through the gas space .
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the refrigeration apparatus according to Embodiment 1 of the present invention will be described with reference to an example in which the compressor is an oil-cooled screw compressor, CO ₂ is used as a refrigerant, and polyol ester is used as refrigeration oil. Will be described with reference to FIG. FIG. 1 (a) is a schematic system diagram of the refrigeration apparatus, and FIG. 1 (b) is an explanatory view of the attachment position of the liquid return line to the evaporator.
[0014]
Reference numeral 1 shown in FIG. 1A is a refrigeration apparatus according to the first embodiment. The refrigeration apparatus 1 includes a fluid circulation channel 8 that forms a refrigeration cycle and communicates from a discharge port 2a of an oil-cooled screw compressor (hereinafter referred to as a compressor) 2 to a suction port 2b. The fluid circulation channel 8 includes an oil separator 3, a condenser 4, a liquid receiver 5, an expansion valve 6 as an expansion means, and an evaporator 7 in that order from the discharge port 2a to the suction port 2b. It is disguised. The oil separator 3 separates and collects refrigerating machine oil from a mixed fluid composed of the refrigerant discharged from the compressor 2 and splashed refrigerating machine oil, and causes the refrigerant after removing the refrigerating machine oil to flow into the condenser 4. It works.
[0015]
By the way, the refrigerating machine oil separated by the oil separator 3 is temporarily stored in an oil reservoir 3a formed in the oil separator 3 and below. The refrigerating machine oil stored in the oil reservoir 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 path (not shown). It is comprised so that it may be supplied to a part.
[0016]
The gaseous refrigerant that has flowed out of the oil separator 3 flows into the condenser 4 and is cooled and condensed by heat exchange with the cooling liquid to become 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, is supercooled, and flows into the evaporator 7. The supercooled refrigerant that has flowed into the evaporator 7 is evaporated by exchanging heat with a fluid to be cooled that cools a cooling load (not shown) such as a freezer, and flows out from the evaporator 7 as a gaseous refrigerant. . The gaseous refrigerant that has flowed out of the evaporator 7 is circulated through the fluid circulation flow path 8 so as to exhibit a refrigeration function such that the refrigerant is sucked into the compression space in the compressor 2 through the suction port 2a and compressed. Is configured to do.
[0017]
Further, a discharge port 7 a for discharging the liquid in the evaporator 7, that is, a liquid refrigerant, is provided in the body portion of the evaporator 7. As shown in FIG. 1B, the position where the discharge port 7a is provided is a lower position than the liquid level of the refrigerant in the evaporator 7, and the liquid state in the evaporator 7 due to the liquid head difference of the refrigerant. The refrigerant is discharged from the discharge port 7a.
[0018]
A refrigerant having a high content of refrigerating machine oil can be discharged from the discharge port 7a of the evaporator 7. The reason why the refrigerant in the evaporator 7 contains a large amount of refrigerating machine oil is as follows. That is, as described above, wherein at the refrigerant from the oil recovery unit 3 to the evaporator 7 flows, the refrigeration oil of trace during refrigerant flowing from the oil separator 3, specifically, the usual 100~200ppm Contains a small amount of refrigerating machine oil. This is because the refrigerating machine oil and the refrigerant gas are separated from each other in an incompatible manner, so that the amount of refrigerating machine oil gradually increases in the evaporator 7.
[0019]
It is known that when the content of the refrigerating machine oil in the refrigerant exceeds 4%, the cooling performance of the evaporator 7 decreases. Therefore, in the case of the refrigerating apparatus 1 according to Embodiment 1, the refrigerating machine oil is included while replenishing the refrigerant containing 100 to 200 ppm of refrigerating machine oil so that the content of the refrigerating machine oil is 2% or less. The refrigerant liquid is discharged. 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 rate 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 liquid drainage amount.
[0020]
Further, a liquid return line 10 is interposed between the discharge port 7 a and the evaporator 7 of the fluid circulation channel 8 and the suction port 2 b of the compressor 2. In the liquid return line 10, a flow rate adjusting valve 11, a flow meter 12, and an opening / closing valve 13 are interposed in order from the discharge port 7 a side toward the communicating portion side with the fluid circulation channel 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 is constant. The on-off valve 13 is opened and closed by an electric signal.
[0021]
In the case of the refrigeration apparatus 1 according to the first embodiment, the liquid return line 10 is communicated with the fluid circulation channel 8, but may be directly communicated with the suction port 2 b of the compressor 2. . Further, it is more preferable to provide a configuration in which a viewing window (sight glass) for monitoring the flow of the liquid is provided in the liquid return line 10 and the flow state of the liquid flowing through the liquid return line 10 can be monitored from the viewing window.
[0022]
Hereinafter, the usage mode of the refrigeration apparatus 1 according to the first embodiment will be described. As the operation time of the refrigeration apparatus 1 elapses, due to the difference in boiling point between the refrigerating machine oil and the refrigerant, The content of refrigeration oil gradually increases. When the content of the refrigeration oil in the refrigerant in the evaporator 7 becomes 2% due to further continuation of the operation, the refrigerant discharge amount that the content of the refrigeration oil in the evaporator 7 does not exceed 2% is determined. The on-off valve 13 is opened. When the on-off valve 13 is opened, the flow rate of the refrigerant flowing out from the discharge port 7a is detected by the flow meter 12 due to the liquid head difference of the refrigerant in the evaporator 7 while the refrigeration apparatus 1 is in operation.
[0023]
Then, the opening degree of the flow control valve 11 is controlled so that the flow rate of the refrigerant detected by the flow meter 12 becomes the discharge amount, and the refrigerant containing a certain amount of refrigerating machine oil per hour is passed through the liquid return line 10. It continues to be returned to the suction port 2b of the compressor 2. During discharge of such a refrigerant, the refrigerant containing 100 to 200 ppm of refrigerating machine oil is continuously supplied from the liquid receiver 5 so that the liquid level of the refrigerant in the evaporator 7 is constant. When the operation of the refrigeration apparatus 1 is stopped, the on-off valve 13 is closed to protect the refrigeration apparatus 1, and the supply of refrigerant to the suction port of the compressor 2 is stopped. is there.
[0024]
According to the refrigeration apparatus 1 according to the first embodiment, as described above, the refrigerant liquid containing the refrigeration oil can be returned from the evaporator 7 to the suction port 2b of the compressor 2 by a certain amount per unit time. And it can prevent that the content rate of the refrigerating machine oil in the refrigerant | coolant in the evaporator 7 becomes 2% or more. Therefore, according to the refrigeration apparatus 1 according to Embodiment 1, the following effects can be obtained.
(1) Since the content of the refrigerating machine oil in the refrigerant in the evaporator 7 continues to be maintained at 2% or less and does not become 4% or more which causes a decrease in cooling performance, the expected cooling performance is reduced. Can continue to demonstrate.
(2) Since it is not necessary to provide a heat exchanger or a heater as in the conventional example and the configuration of the liquid return line is simple, the reliability is improved and the running cost of the refrigeration apparatus is advantageous.
[0025]
Next, the refrigeration apparatus according to Embodiment 2 of the present invention is schematically illustrated by taking the case where the compressor is an oil-cooled screw compressor as in the case of the refrigeration apparatus according to Embodiment 1 described above. This will be described with reference to FIG. 2 of the system diagram. By the way, regarding the configuration, the second embodiment is different from the first embodiment in that the low-pressure liquid receiver is provided and the connection position of the base end portion of the liquid return line is different. . Accordingly, the same components as those in the first embodiment and the components having the same functions are denoted by the same reference numerals, and different points will be described.
[0026]
The refrigeration apparatus 1 according to Embodiment 2 also uses CO ₂ as the refrigerant and uses a polyol ester that is compatible with CO ₂ as the refrigerating machine oil. In this refrigeration apparatus 1, a low-pressure liquid receiver 14 is interposed between an expansion valve 6 that is an expansion means of the fluid circulation channel 8 and the evaporator 7. A liquid pump 15 is interposed between the low-pressure receiver 14 and the evaporator 7 in the fluid circulation channel 8, and the evaporator 7 and the suction port of the compressor 2 in the fluid circulation channel 8. 2b is interposed through the gas space 14b of the low-pressure receiver 14. The gas space 14b of the low-pressure receiver 14 may be configured to communicate with the fluid circulation channel 8 via a channel (not shown).
[0027]
And between the liquid pump 15 and the evaporator 7 in the fluid circulation channel 8, the evaporator 7 in the fluid circulation channel 8 and the suction port 2 b of the compressor 2 are connected via a liquid return line 10. Communicating between. As in the case of the first embodiment, the liquid return line 10 is provided with a flow rate adjusting valve 11, a flow meter 12, and an on-off valve 13.
[0028]
An operation mode of the refrigeration apparatus 1 according to the second embodiment will be described. That is, the supercooled refrigerant containing the refrigerating machine oil accumulates in the liquid reservoir 14a of the low-pressure 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, it continues to be returned to the compressor 2 by a predetermined amount via the liquid return line 10, and the polyol ester is continuously recovered by a predetermined amount throughout the operation. .
[0029]
Therefore, in addition to the low concentration of CO ₂ being supplied to the evaporator 7 as a polyol ester, it does not separate from CO ₂ and accumulate in the evaporator unlike incompatible refrigerating machine oil. Therefore, since the heat exchange performance of the evaporator 7 is not lowered by the polyol ester, the second embodiment has the same effect as the first embodiment with respect to the stable maintenance of the cooling performance.
Furthermore, since CO ₂ existing in the natural world is used as a refrigerant, it is possible to expect an excellent effect of being able to respond to environmental problems, in particular, social demands for defluorocarbons.
[0030]
In the first and second embodiments, an example in which CO ₂ compatible with a polyol ester is used as a refrigerant has been described. However, an oil that uses NH ₃ as a refrigerant and is compatible with the refrigerant, for example, poly Alkylene glycol may be used as the refrigerating machine oil.
[0031]
【The invention's effect】
As described above in detail, according to the refrigeration apparatus according to claims 1 to 3 of the present invention, the content of the refrigerating machine oil in the refrigerant is not increased in the evaporator, and the refrigerating machine oil is separated. Therefore, it is not necessary to use a heat exchanger or a heater as in the conventional example. Therefore, the desired cooling performance can be continuously exhibited, and the configuration of the liquid return line is simple, so that the reliability is improved and the running cost of the refrigeration apparatus is advantageous.
[0032]
Furthermore, according to the refrigeration apparatus according to claim 2 or 3 of the present invention, in addition to the above-described effects, NH ₃ that does not destroy the CO ₂ and ozone layers existing in the natural world and has a small contribution to global warming is used as a refrigerant. Therefore, it is possible to expect an excellent effect of being able to respond to environmental problems, in particular, social demands for chlorofluorocarbon removal.
[Brief description of the drawings]
FIG. 1 relates to Embodiment 1 of the present invention, FIG. 1 (a) is a schematic system diagram of a refrigeration apparatus, and FIG. 1 (b) is an explanatory view of an attachment position of a liquid return line to an evaporator.
FIG. 2 is a schematic system diagram of a refrigeration 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 refrigeration apparatus according to Conventional Example 2.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Refrigeration apparatus, 2 ... Compressor (oil-cooled screw compressor), 2a ... Discharge port, 2b ... Suction port, 3 ... Oil separator, 3a ... Oil reservoir part, 4 ... Condenser, 5 ... Liquid receiver , 6 ... expansion valve, 7 ... evaporator, 7a ... discharge port, 8 ... fluid circulation channel, 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 (3)

A fluid circulation passage that communicates from the discharge port of the compressor to the suction port and constitutes a refrigeration cycle is provided. In this fluid circulation passage, an oil separator, a condenser, a liquid receiver, an expansion means, and an evaporator are arranged in this order. In the interposing refrigeration apparatus, a discharge port for discharging the liquid inside the evaporator is provided at a position lower than the liquid level of the liquid in the evaporator at the body portion of the evaporator. the discharge port, opening closed, flow meter, and suction of the compressor flow rate adjusting valve the flow rate of the liquid to be detected is controlled to be constant through the interposed has been made liquid return line by the flow meter A refrigeration apparatus characterized by communicating with a mouth. A fluid circulation passage that communicates from the discharge port of the compressor to the suction port and constitutes a refrigeration cycle is provided. In this fluid circulation passage, an oil separator, a condenser, a liquid receiver, an expansion means, and an evaporator are arranged in this order. A refrigerating apparatus that uses either CO ₂ or NH ₃ as a refrigerant and uses oil that is compatible with the refrigerant as a refrigerating machine oil, the expansion means of the fluid circulation channel and the A low-pressure receiver is interposed between the evaporator and an opening / closing valve, a flow meter, and the flow meter between the liquid reservoir of the low-pressure receiver of the fluid circulation channel and the evaporator. refrigerating apparatus flow rate of the liquid to be detected characterized in that communicates with the suction port of the compressor via the liquid return line modulate the flow control valve is being interposed so as to be constant. Wherein between said evaporator and said inlet of the fluid circulation passage is serial mounting of the refrigeration apparatus to claim 2, characterized in that through the gas space of the low pressure receiver.

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