JP5119060B2 - Refrigeration cycle - Google Patents

Description

  The present invention relates to a refrigeration cycle, and more particularly to a refrigeration cycle that can optimally separate refrigerant and oil when a new refrigerant is used and can be operated with high efficiency.

  For example, a refrigeration cycle used in a vehicle air conditioner or the like has a basic configuration as shown in FIG. In FIG. 7, a refrigeration cycle 101 includes a compressor 102 that compresses refrigerant, a condenser 103 that condenses the compressed refrigerant, an expansion valve 104 that depressurizes and expands the condensed refrigerant, An evaporator 105 that evaporates the expanded refrigerant is provided, and the refrigerant is circulated through the refrigeration cycle 101 while changing its state. In such a refrigeration cycle 101, in order to improve the durability of the compressor 102 and the like, lubricating oil (for example, oil made of PAG [polyalkylene glycol]) may be included in the refrigerant used. is there. When refrigerant and oil are used, an oil separator is provided at an appropriate position in the cycle in order to suppress heat transfer inhibition due to oil adhesion in the heat exchanger (eg, evaporator 105) during the cycle. A method is known in which oil separated from refrigerant is not introduced into a heat exchanger as much as possible, and is returned to a compressor that requires lubrication. However, R134a can be cited as a typical present refrigerant, and since the compatibility between the R134a refrigerant and PAG oil is good, in most cases, no oil separator is installed.

Research and development of new refrigerants have been conducted with the aim of further improving the global warming potential (GWP) and the like with respect to R134a as a typical refrigerant as described above (for example, Non-Patent Document 1). Recently, R1234yf has been announced as a new refrigerant aiming at such improvements, and it has become possible to conduct tests and research on application to refrigeration cycles used in, for example, vehicle air conditioners. .
Frozen March 2008 Issue 83 Volume 965

  However, when the new refrigerant R1234yf is used, R1234yf is less compatible with PAG oil than R134a, and there is a problem that the liquid refrigerant and oil are separated particularly on the high-pressure side in the refrigeration cycle. That is, when the new refrigerant R1234yf is used in the refrigeration cycle as shown in FIG. 7, for example, as shown in FIG. 6 as an example of certain operating conditions at a relatively high load, R1234yf and PAG oil Although compatible (compatibility region), the high-temperature and high-pressure side tends to be a two-phase separation region where the refrigerant and oil are separated, and there is a problem that the refrigerant and oil are separated particularly in this region. If the oil is separated from the refrigerant in the middle of the refrigerant circulation path, the oil may not return to the compressor in particular, so that the durability of the compressor remains uneasy.

  In addition, in a vehicle air conditioner using R134a refrigerant, a sight glass is usually attached to the liquid line in the refrigeration cycle, and it is possible to determine the excess or deficiency of the refrigerant by the refrigerant behavior that can be observed through the sight glass. Met. However, when the new refrigerant R1234yf is used, there is the above-mentioned problem that the liquid refrigerant and oil are separated in the middle of the refrigerant circulation path, and the sight glass becomes dirty or cloudy with the separated oil. In most cases, it may not be possible to determine whether the refrigerant is excessive or insufficient.

  Therefore, an object of the present invention is to focus attention on the problems in the case of using the new refrigerant R1234yf as described above, and to force the refrigerant and oil to be properly forced at an appropriate position even when the refrigerant is changed to the new refrigerant R1234yf. Operates with high efficiency as a whole refrigeration cycle by preferentially returning the separated oil to parts that require lubrication, such as compressors, and avoiding supply to heat exchangers where oil supply is not desirable. It is to make it possible.

  In addition, another object of the present invention is that when a sight glass is provided in the liquid line in the refrigeration cycle, even when the new refrigerant R1234yf is used, it is possible to accurately determine the excess or deficiency of the refrigerant through the sight glass. There is to do.

In order to solve the above problems, a refrigeration cycle according to the present invention includes a compressor that compresses a refrigerant, a condenser that condenses the compressed refrigerant, a decompression / expansion unit that decompresses / expands the condensed refrigerant, and a decompression / expansion unit. In the refrigeration cycle provided with an evaporator for evaporating the expanded refrigerant in this order in the refrigerant flow direction, R1234yf is used as the refrigerant, and among the regions from the compressor outlet side to the pressure reducing / expanding means, the refrigerant Oil separation means for forcibly separating refrigerant and oil is provided in a two-phase separation region where oil and oil are mixed in a state of being separated without being incompatible , and between the oil separation means and the compressor And an oil return line for returning the oil separated by the oil separating means to the compressor, the oil return line being provided with a pressure reducing device, and the pressure reducing device is connected to the crankcase of the compressor. Consisting of those, characterized in that it is directly connected. Here, the condenser in the present invention is a concept including a so-called subcool condenser having a supercooling region in which a refrigerant is condensed into a supercooled liquid refrigerant in addition to a normal condenser.

  That is, when R134a was used as the refrigerant, it was unnecessary in most cases to install an oil separator, but in the present invention using the new refrigerant R1234yf, a specific region in the refrigeration cycle, That is, oil separation means is provided in the two-phase separation region to forcibly separate the refrigerant and oil. This two-phase separation region is effective as a location for separating oil. In other words, the two-phase separation region is a region where the refrigerant and oil are separated without any special operation, and in the present invention, this region is used in reverse. As described above, it is better not to circulate oil as much as possible in the heat exchanger. However, when the refrigerant is in a gas state, the compatibility with the oil is small even with the current refrigerant, but the gas state region on the inlet side of the condenser. Then, it will be similarly affected by oil. Therefore, in the present invention, the oil separation is particularly performed between the condenser and the decompression / expansion means (between the condenser gas region outlet and the decompression / expansion means inlet) in the two-phase separation region. It is preferable that the oil separation means is provided in this region. In the two-phase separation region, a compressor that requires lubrication without forcing the separated oil to pass through the downstream heat exchanger by forcibly and appropriately separating the refrigerant and oil by various methods as described below. It becomes possible to return to etc. As a result, it is possible to reduce the risk of heat transfer obstruction due to oil adhesion in the heat exchanger, improve the refrigeration capacity and coefficient of performance of the refrigeration cycle, and perform lubrication in the compressor etc. in a good condition at all times. It becomes possible, and it becomes possible to remove the concern about durability.

When the compressor return oil between the oil separating means and the compressor, Ru provided oil return line returning the separated oil in the oil separating means to the compressor. For oil return, for example, a capillary tube is used, and the oil is directly returned by connecting to the crankcase of the compressor .

  In addition, if a sight glass is provided at an appropriate liquid line position downstream in the refrigerant circulation direction from the installation position of the oil separation means, most of the oil has already been separated and removed from the refrigerant passing through the sight glass installation site. In particular, the oil mixed with the refrigerant in a state separated from the refrigerant can be prevented from clouding the sight glass, and the behavior of the refrigerant can be clearly observed through the sight glass. It will be possible to accurately determine the excess and deficiency.

  As the oil, for example, as described above, PAG oil made of polyalkylene glycol can be used. In the two-phase separation region where the oil separation means is provided, particularly in the region between the condenser outlet and the decompression / expansion means inlet, the state of the refrigerant is usually a liquid state, and the specific gravity thereof is, for example, as shown in Table 1 below. In addition, R1234yf refrigerant is smaller than PAG oil. That is, in a state where the oil is forcibly separated, the oil forms a layer below the refrigerant. Therefore, if the separated oil is allowed to flow out from the lower side in the vertical direction and the oil separating means is disposed higher in the vertical direction than the compressor, the separated oil can be easily returned to the compressor. Such a vertical positional relationship between the oil separating means and the compressor is effective when the specific gravity of the oil is larger than the specific gravity of the R1234yf refrigerant, and is particularly effective when the oil is PAG oil.

  Various configurations can be adopted as the configuration of the oil separating means itself. For example, the oil separation means has a centrifugal separation means for separating the refrigerant and the oil by centrifuging the refrigerant and oil, and the oil separation means separates the refrigerant and the oil by colliding the refrigerant and the oil. Or a configuration in which the oil separation means has a capture separation means for separating the refrigerant and the oil by capturing the refrigerant and the oil of the oil.

  Furthermore, the structure which combined the said structure can also be taken. For example, the oil separation means includes a centrifugal separation means that separates the refrigerant and the oil by centrifuging the refrigerant and oil, and a capture separation means that separates the refrigerant and the oil by capturing the refrigerant and the oil of the oil, or The oil separation means may have a configuration including a collision separation means for separating the refrigerant and the oil by colliding the refrigerant and the oil, and a capture separation means for separating the refrigerant and the oil by capturing the refrigerant and the oil of the oil. .

  In particular, if the oil separation means is provided with the capturing and separating means at the lowest position and the oil is captured by the capturing and separating means, the separated oil flows into, for example, the liquid refrigerant suction pipe located above. Can be prevented.

  It is also a preferred embodiment that a temporary oil storage part is provided at the lower part in the vertical direction in the oil separation means. When such a temporary storage portion is provided, the separated oil is returned from the temporarily stored state having a certain amount of oil to a desired destination, so that stable oil return is possible, and this oil Since the return line can be sealed with the oil in the temporary storage portion, an undesirable inflow of the refrigerant into the oil return line is prevented.

  In addition, it is also a preferred embodiment that an oil outlet is provided at the lower end in the vertical direction of the oil separating means. This arrangement of the oil outlet is particularly effective when there is a magnitude relationship between the specific gravity of the oil and the specific gravity of the R1234yf refrigerant as described above.

  Such a refrigeration cycle according to the present invention is basically applicable to any refrigeration cycle in which the new refrigerant R1234yf is to be used, but particularly efficient operation and high durability such as a compressor over a long period of time. It is suitable for a refrigeration cycle used in a vehicle air conditioner for which

  According to the refrigeration cycle according to the present invention, the durability and reliability of the compressor in the refrigeration cycle using the new refrigerant R1234yf can be improved. In addition, oil is no longer circulated to the refrigeration cycle after the oil separation means arrangement portion, and the possibility of causing heat transfer inhibition due to oil adhesion in the heat exchanger on the downstream side is reduced. The coefficient of performance can be improved. Furthermore, the behavior of the refrigerant can be reliably observed by the sight glass provided in the liquid line, and thereby the excess or deficiency of the refrigerant can be reliably determined.

  The present invention will be described below together with preferred embodiments with reference to the drawings. FIG. 1 shows the equipment arrangement of a refrigeration cycle according to an embodiment of the present invention. In the illustrated example, the vertical direction of the figure is the vertical direction X, the upper part of the figure is higher in the vertical direction, and the lower part of the figure is It represents that it is located in the lower vertical direction. As in the basic configuration shown in FIG. 7, the refrigeration cycle 1 includes a compressor 2 that compresses the refrigerant, a condenser 3 that condenses the compressed refrigerant, and a decompression / expansion unit that decompresses and expands the condensed refrigerant. The expansion valve 4 and the evaporator 5 for evaporating the decompressed / expanded refrigerant are provided in this order in the direction of the refrigerant flow (in the direction of the arrow), and further, R1234yf is used as the refrigerant and compression is performed. Of the region from the outlet side of the machine 2 to the inlet of the expansion valve 4, the two-phase separation region (for example, two phases shown in FIG. An oil separator 6 as oil separation means for forcibly separating the refrigerant and oil is provided in the phase separation region). In this embodiment, an oil separator 6 is provided between the condenser 3 and the expansion valve 4 in the two-phase separation region. The oil separator 6 and the compressor 2 are connected by an oil return line 7 that returns the oil forcedly separated by the oil separator 6 to the compressor 2. For example, a capillary tube is used for the oil return line 7, and one end side of the capillary tube is directly connected to, for example, a crankcase of the compressor 2 so that oil can be directly returned into the crankcase. For example, the aforementioned PAG oil is used as the oil.

  The positional relationship in the vertical direction between the oil separator 6 and the compressor 2 is such that the oil separator 6 is higher than the compressor 2 so that the oil separated by the oil separator 6 is smoothly returned to the compressor 2 by its own weight. The compressor 2 is disposed so as to be lower than the oil separator 6.

  The part in the refrigeration cycle from the part where the oil separator 6 is arranged to the expansion valve 4 is usually a liquid line, but the behavior of the internal refrigerant can be observed at an appropriate place in the liquid line. A sight glass 8 is provided.

  Since the oil forcedly separated by the oil separator 6 is returned to the compressor 2 through the oil return line 7, the lubrication state of the compressor 2 is maintained in a sufficiently good state, and durability for a long period is ensured. The In addition, since the oil forcedly separated by the oil separator 6 is not supplied to the refrigeration cycle path after the oil separator 6, the oil adheres to the heat exchanger existing on the downstream side, that is, the evaporator 5 in the illustrated example. The risk of causing heat transfer inhibition due to is reduced, and the refrigeration capacity and the coefficient of performance of the refrigeration cycle 1 are improved. Further, since the oil forcedly separated by the oil separator 6 is not supplied to the sight glass 8 provided in the liquid line, the sight glass 8 is prevented from being clouded by the oil, and the behavior of the internal refrigerant is prevented. Thus, it is possible to reliably determine whether the refrigerant is excessive or insufficient through the refrigerant behavior observation.

  The oil separator 6 can be configured in various structures. 2 to 4 show structural examples in the case where an oil separator is disposed between the compressor 2 and the condenser 3 in the above-described two-phase separation region, for example. FIG. The example of a preferable structure at the time of arrange | positioning the oil separator 6 in the most preferable position shown is shown. These structural examples are merely examples, and for example, as described above, the structures according to any of the examples can be combined.

  In the example shown in FIG. 2, the refrigerant and oil from the compressor 2 are centrifuged by a pipe-like centrifuge 11 as a centrifuge provided in the oil separator 6 a, whereby the refrigerant phase 12 and The oil is forcibly separated into the oil phase 13 temporarily accommodated in the lower oil temporary accommodating portion, and the separated oil is returned to the compressor 2 through the oil return line 7, and the separated refrigerant is condensed. It is sent to the vessel 3.

  In the example shown in FIG. 3, the collision separator 21 is provided in the oil separator 6b as the collision separator 21 serving as a collision separator for separating the refrigerant and the oil by causing the refrigerant and the oil to collide with each other. Is forcibly separated into the refrigerant phase 22 and the oil phase 23 temporarily accommodated in the oil temporary accommodating portion on the lower side, and the separated oil is returned to the compressor 2 through the oil return line 7, The separated refrigerant is sent to the condenser 3.

  In the example shown in FIG. 4, the refrigerant and oil from the compressor 2 are captured and separated as a capture and separation means provided in the oil separator 6c to separate the refrigerant and oil by capturing the refrigerant and oil. The portion 31 is forcibly separated into the refrigerant phase 32 and the oil phase 33 temporarily accommodated in the lower oil temporary accommodating portion, and the separated oil returns to the compressor 2 through the oil return line 7. The separated refrigerant is sent to the condenser 3.

  In the example shown in FIG. 5, the refrigerant and oil from the condenser 3 is a pipe-shaped centrifuge as a centrifugal separator provided in an oil separator 6d (corresponding to the oil separator 6 shown in FIG. 1). Centrifugal separation by the cum suction pipe 41 forces separation into the liquid refrigerant phase 42 and the oil phase 43 temporarily accommodated in the lower oil temporary accommodating portion. Further, an oil capturing / separating section 44 is provided in the section, and the refrigerant sucked up by the centrifugal separator / uptake pipe 41 is further captured and retained so that it does not flow out along with the refrigerant flow. The oil is forcibly separated. The separated oil is returned to the compressor 2 through the oil return line 7, and the separated refrigerant is the supercooling region (in the condenser 3 when the expansion valve 4 or the condenser 3 is the subcool condenser described above) ( Liquid refrigerant).

  In this way, the oil separation means itself can take various configurations depending on the installation location in the two-phase separation region.

  The refrigeration cycle according to the present invention can be applied to any refrigeration cycle in which the new refrigerant R1234yf is to be used, and is particularly suitable as a refrigeration cycle used in a vehicle air conditioner.

It is an equipment distribution diagram of a refrigerating cycle concerning one embodiment of the present invention. It is a schematic block diagram which shows an example of the oil separation means in this invention. It is a schematic block diagram which shows another example of the oil separation means in this invention. It is a schematic block diagram which shows another example of the oil separation means in this invention. It is a schematic block diagram which shows another example of the oil separation means in this invention. It is a characteristic view which shows an example of the phase state of new refrigerant | coolant R1234yf. It is an equipment distribution diagram of the conventional refrigeration cycle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Refrigeration cycle 2 Compressor 3 Condenser 4 Expansion valve 5 as decompression / expansion means Evaporator 6, 6a, 6b, 6c, 6d Oil separator 7 as oil separation means 7 Oil return line 8 Sight glass 11 Centrifugation means Centrifugal separators 12, 22, and 32 Refrigerant phases 13, 23, 33, and 43 Oil phase 21 Collision separating part 31 as collision separating means Capture and separating part 41 as collecting and separating means Centrifugal part and suction pipe 44 Oil capturing and separating Part

Claims (10)

A compressor that compresses the refrigerant, a condenser that condenses the compressed refrigerant, a decompression / expansion means that decompresses / expands the condensed refrigerant, and an evaporator that evaporates the decompressed / expanded refrigerant in the refrigerant flow direction. In the refrigeration cycle provided in this order, R1234yf is used as the refrigerant, and in the region from the compressor outlet side to the pressure reducing / expanding means, the refrigerant and oil are mixed in a state where they are separated without being mixed. An oil separation means for forcibly separating the refrigerant and the oil is provided in the two-phase separation area, and the oil separated by the oil separation means is returned to the compressor between the oil separation means and the compressor. A refrigeration cycle , wherein a return line is provided, a pressure reducing device is provided in the oil return line, and the pressure reducing device is directly connected to a crankcase of the compressor . The refrigeration cycle according to claim 1, wherein the decompression device comprises a capillary tube, and the oil comprises a polyalkylene glycol oil. The refrigeration cycle according to claim 1 or 2 , wherein the oil separation means is provided between the condenser and the pressure reduction / expansion means.   The refrigeration cycle according to any one of claims 1 to 3, wherein a sight glass capable of observing the behavior of the internal refrigerant is provided downstream of the oil separation means in the refrigerant circulation direction. The refrigeration cycle according to any one of claims 1 to 4 , wherein the oil separation means is disposed higher in the vertical direction than the compressor. The refrigeration cycle according to any one of claims 1 to 5 , wherein the oil separation unit includes a centrifugal separation unit that separates the refrigerant and the oil by centrifuging the refrigerant and the oil. The refrigeration cycle according to any one of claims 1 to 6 , wherein the oil separation unit includes a collision separation unit that separates the refrigerant and the oil by colliding the refrigerant and the oil. The refrigeration cycle according to any one of claims 1 to 7 , wherein a temporary storage portion for oil separated in a lower portion in the vertical direction in the oil separation means is provided. The refrigeration cycle according to any one of claims 1 to 8 , wherein an outlet for separated oil is provided at a lower end in a vertical direction of the oil separating means. The refrigeration cycle according to any one of claims 1 to 9 , which is used in a vehicle air conditioner.

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