JP2008122059A - Heat exchanger and refrigeration system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deterioration of heat transfer performance of a heat exchanger due to forming of an oil film on an inner wall surface of a heat transfer tube, in regard to a heat exchanger applied to a refrigeration system carrying out refrigerating cycle of a vapor compression type. <P>SOLUTION: Oil grooves 25 for capturing and distributing oil are formed on an inner circumferential face of the heat transfer tube 22 of the heat exchangers 12, 13 so as to extend in an axial direction of the heat transfer tube 22. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat exchanger applied to a refrigeration apparatus that performs a refrigeration cycle, and a refrigeration apparatus having a heat exchanger, and particularly relates to measures for promoting heat transfer in a heat exchanger.

  Conventionally, a refrigeration apparatus that performs a vapor compression refrigeration cycle is known, and is widely applied to an air conditioner, a water heater, and the like.

  For example, an air conditioner disclosed in Patent Document 1 has a refrigerant circuit to which a compressor, an outdoor heat exchanger, an expander, and an indoor heat exchanger are connected. This refrigerant circuit is filled with carbon dioxide as a refrigerant.

In the cooling operation of the air conditioner, the refrigerant compressed to a critical pressure or higher by the compressor flows through the outdoor heat exchanger. In the outdoor heat exchanger, the refrigerant and the outdoor air exchange heat, and the refrigerant radiates heat to the outdoor air. The refrigerant radiated by the outdoor heat exchanger is depressurized by the expander and then flows through the indoor heat exchanger. In the indoor heat exchanger, the refrigerant and room air exchange heat, and the refrigerant absorbs heat from the room air and evaporates. As a result, the room is cooled. The refrigerant evaporated in the indoor heat exchanger is sucked into the compressor and compressed again.
JP 2001-116371 A

  By the way, in the refrigeration apparatus as described above, lubricating oil (refrigerating machine oil) is used to lubricate each sliding portion of the compressor, and this oil is included in the refrigerant flowing through the refrigerant circuit. For this reason, when the refrigerant flows through a heat exchanger such as an evaporator or a radiator, oil that has not been dissolved in the refrigerant adheres to the inner wall of the heat transfer tube, and an oil film forms over the entire circumference of the inner wall of the heat transfer tube. Sometimes formed. As a result, there has been a problem that the heat transfer between the refrigerant and air is hindered by the oil film and the heat transfer performance of the heat exchanger is lowered.

  In particular, in a refrigeration apparatus that performs a refrigeration cycle using carbon dioxide as a refrigerant as disclosed in Patent Document 1, it is common to use PAG (polyalkylene glycol) as refrigeration oil. However, since this type of oil has low compatibility with carbon dioxide, an oil film as described above is easily formed in the heat transfer tube of the heat exchanger. Therefore, in a heat exchanger applied to a refrigeration apparatus using carbon dioxide as a refrigerant, the heat transfer performance is significantly reduced due to the formation of an oil film.

  The present invention has been made in view of such points, and an object thereof is to form an oil film on the inner wall surface of the heat transfer tube in a heat exchanger applied to a refrigeration apparatus that performs a vapor compression refrigeration cycle. This is to prevent the heat transfer performance of the heat exchanger from deteriorating.

  The first invention is applied to a refrigeration apparatus that performs a vapor compression refrigeration cycle, and presupposes a heat exchanger having a heat transfer tube (22) through which a refrigerant flows. The heat transfer tube (22) of the heat exchanger is characterized in that an oil groove (25) for capturing and circulating oil in the refrigerant is formed on the inner wall surface thereof. .

  In the first invention, an oil groove (25) is formed on the inner wall surface of the heat transfer tube (22) of the heat exchanger for the heat exchanger connected to the refrigerant circuit of the refrigeration apparatus. By forming the oil groove (25) in the heat transfer tube (22) in this way, oil contained in the refrigerant flowing in the heat transfer tube (22) is captured in the oil groove (25), and this oil groove (25 ) Will be distributed.

  Specifically, when the refrigerant flowed in the heat transfer tube (22), the refrigerant flowed closer to the center in the heat transfer tube (22) due to the difference in viscosity and specific gravity, but could not be dissolved in the refrigerant. The oil flows toward the outside in the heat transfer tube (22). That is, since oil flows along the inner wall of the heat transfer tube (22), an oil film is formed on the entire inner wall surface of the heat transfer tube (22). Here, in the present invention, the oil groove (25) is formed in the inner wall surface of the heat transfer tube (22). For this reason, the oil covering the inner wall of the heat transfer tube (22) is drawn into the oil groove (25) by the surface tension and flows through the oil groove (25). As a result, in the present invention, it is avoided that an oil film is formed on the inner wall of the heat transfer tube (22).

  According to a second aspect, in the heat exchanger according to the first aspect, the oil groove (25) extends in an axial direction of the heat transfer tube (22).

  In the second invention, the oil groove (25) is formed on the inner wall surface of the heat transfer tube (22) so as to extend in the axial direction of the heat transfer tube (22). That is, in the present invention, the oil groove (25) is formed to extend in the same direction as the flow of the refrigerant. For this reason, when oil is captured in the oil groove (25) as described above, the oil smoothly flows in the oil groove (25) in the same direction as the refrigerant flowing outside the oil groove (25). . As a result, in the present invention, the oil trapped in the oil groove (25) is prevented from flowing out of the oil groove (25).

  According to a third aspect of the present invention, in the heat exchanger of the second aspect, the plurality of oil grooves (25) are arranged at equal intervals in the circumferential direction on the inner wall surface of the heat transfer tube (22). It is what.

  In the third invention, the plurality of oil grooves (25) extending in the axial direction of the heat transfer tube (22) are arranged at equal intervals in the circumferential direction of the inner peripheral surface of the heat transfer tube (22). For this reason, the oil film formed over the entire inner peripheral surface of the heat transfer tube (22) is easily captured by each oil groove (25). Further, the amount of oil trapped in each oil groove (25) is made uniform, and the oil trapping effect by each oil groove (25) is improved.

  According to a fourth aspect of the present invention, in the heat exchanger of the first aspect, a plurality of oil grooves (25) extending in a V shape are provided on the inner wall surface of the heat transfer tube (22) in the axial direction of the heat transfer tube (22). It is characterized by being arranged.

  In the fourth invention, a plurality of V-shaped oil grooves (25) are formed on the inner wall surface of the heat transfer tube (22). Each oil groove (25) is arranged in the axial direction of the heat transfer tube (22) so that all the oil grooves (25) face one side in the axial direction. When the refrigerant flows through the heat exchanger having the oil groove (25) in the same direction as the direction of the V-shaped tip of the oil groove (25), the refrigerant trapped in the oil groove (25). After collecting at the V-shaped tip side, it flows out from the oil groove (25) and flows in the same direction as the refrigerant. When the oil flows in such a way for each oil groove (25), the oil finally flows on the inner wall surface of the heat transfer tube (22) so as to connect the V-shaped tip of each oil groove (25). That is, in the heat transfer tube (22) of the present invention, an oil flow path is formed so as to connect the V-shaped tip of each oil groove (25), so that the oil smoothly flows in the heat transfer tube (22). Will flow.

  According to a fifth invention, in the heat exchanger according to any one of the first to fourth inventions, a lipophilic layer (27) made of a lipophilic material is formed on the inner wall surface of the oil groove (25). It is characterized by being.

  In 5th invention, the lipophilic layer (27) which has lipophilicity is formed in the inner wall of an oil groove (25). For this reason, the oil in the heat transfer tube (22) is easily drawn into the oil groove (25), so that the oil is efficiently captured in the oil groove (25).

  According to a sixth invention, in the heat exchanger according to any one of the first to fifth inventions, a portion other than the oil groove (25) on the inner wall surface inside the heat transfer tube (22) has oil repellency. An oil repellent layer (28) made of a material is formed.

  In the sixth invention, the oil repellent layer (28) is formed on the inner wall surface outside the oil groove (25) of the heat transfer tube (22). Therefore, in the present invention, the oil outside the oil groove (25) is repelled by the oil repellent layer (28) and easily enters the oil groove (25). As a result, the oil is trapped more efficiently in the oil groove (25).

  According to a seventh aspect of the present invention, in the heat exchanger of the first aspect, the inner wall surface of the heat transfer tube (22) is formed in a spiral shape swirling in the circumferential direction of the heat transfer tube (22) to transfer heat. A plurality of heat transfer promotion grooves (50) for promotion are provided.

  In the seventh invention, the spiral heat transfer promoting groove (50) is formed on the inner wall surface of the heat transfer tube (22). When the heat transfer promoting groove (50) is formed in this way, the surface area of the inner wall surface of the heat transfer tube (22) is enlarged, so that the heat transfer performance of the heat exchanger is improved.

  According to an eighth aspect of the present invention, in the heat exchanger of the seventh aspect, the oil groove (25) extends in the axial direction of the heat transfer tube (22) while intersecting with the heat transfer promotion groove (50). It is characterized by this.

  In the eighth aspect of the invention, the oil groove (25) is formed on the inner wall surface of the heat transfer tube (22) so as to extend in the axial direction so as to intersect with the spiral heat transfer promotion groove (50). That is, the oil groove (25) is formed so as to be connected to the plurality of heat transfer promotion grooves (50). For this reason, even if oil accumulates in each heat transfer promotion groove (50), this oil can be caused to flow into the oil groove (25) through the heat transfer promotion groove (50). Therefore, it is avoided that an oil film is formed in the heat transfer promotion groove (50).

  A ninth invention is the heat exchanger according to the eighth invention, wherein the plurality of oil grooves (25) are arranged at equal intervals in the circumferential direction on the inner wall surface of the heat transfer tube (22). It is what.

  In the ninth invention, the plurality of oil grooves (25) extending in the axial direction of the heat transfer tube (22) are arranged at equal intervals in the circumferential direction of the inner peripheral surface of the heat transfer tube (22). For this reason, the oil film formed over the entire inner peripheral surface of the heat transfer tube (22) is easily captured by each oil groove (25). Further, the amount of oil trapped in each oil groove (25) is made uniform, and the oil trapping effect by each oil groove (25) is improved. Furthermore, since the oil accumulated in each heat transfer promotion groove (50) can be quickly discharged to the oil groove (25), it is further avoided that an oil film is formed in each heat transfer promotion groove (50). It becomes easy to do.

  According to a tenth aspect of the present invention, in the heat exchanger according to any one of the seventh to ninth aspects, the opening width of the oil groove (25) is wider than the opening width of the heat transfer promoting groove (50). It is characterized by being.

  In the tenth aspect of the invention, the opening width of the oil groove (25) is made wider than the opening width of the heat transfer promotion groove (50). For this reason, while it becomes difficult for oil to enter into the heat transfer promotion groove (50), oil becomes easy to enter into the oil groove (25), and the oil trapping effect by the oil groove (25) is improved.

  In an eleventh aspect according to any one of the seventh to tenth aspects, the groove depth of the oil groove (25) is equal to or greater than the groove depth of the heat transfer promoting groove (50). It is a feature.

  In the eleventh invention, since the groove depth of the oil groove (25) is equal to or greater than the groove depth of the heat transfer promotion groove (50), oil accumulated in the heat transfer promotion groove (50) is removed from the oil groove (25). It becomes easy to flow down.

  12th invention presupposes the freezing apparatus provided with the refrigerant circuit (10) which performs a vapor compression type refrigerating cycle. In the refrigerant circuit (10) of the refrigeration apparatus, carbon dioxide as the refrigerant and polyalkylene glycol as the refrigerating machine oil circulate, and any one of the first to eleventh heat exchangers (12, 13). Is provided.

  In the refrigeration apparatus of the twelfth aspect of the invention, carbon dioxide is used as the refrigerant, while polyalkylene glycol (PAG) is used as the refrigeration oil for lubricating the compression mechanism and the like. This PAG has low compatibility with carbon dioxide. Therefore, in the heat exchanger (12, 13), the refrigerant and the oil are easily separated, and an oil film is easily formed over the entire area on the inner wall of the heat transfer tube (22). However, in the present invention, an oil groove (25) for capturing and circulating oil is formed in the inner peripheral wall of the heat transfer tube (22). Therefore, in this refrigeration apparatus, the generation of such an oil film can be avoided in advance, and the heat transfer performance of the heat exchanger (12, 13) can be prevented from being lowered.

  In the present invention, an oil groove (25) for capturing oil is formed on the inner wall surface of the heat transfer tube (22). For this reason, in the case of a conventional heat exchanger, an oil film has been formed on the entire inner wall surface of the heat transfer tube and the heat transfer performance has deteriorated, whereas according to the present invention, the heat transfer tube (22) By capturing the oil on the inner wall surface in the oil groove (25), the formation of the oil film can be suppressed. As a result, in this heat transfer tube (22), since the area where the inner wall surface and the refrigerant come into contact can be widened, heat transfer between the refrigerant and the heat medium can be promoted. Further, when the formation of the oil film is prevented in this way, it is possible to prevent the pressure loss of the heat transfer tube (22) from increasing due to the formation of the oil film.

  Furthermore, in the present invention, the oil trapped in the oil groove (25) flows through the oil groove (25) and quickly flows out of the heat exchanger. For this reason, according to this invention, it can prevent that oil stagnates in a heat exchanger, and can fully secure the oil return amount to a compression mechanism etc.

  In particular, in the second invention, since the oil groove (25) is formed in the axial direction of the heat transfer tube (22), the oil trapped in the oil groove (25) is moved inside the oil groove (25). It will flow smoothly. Therefore, it is possible to avoid the oil once trapped in the oil groove (25) from flowing out of the oil groove (25) and covering the inner wall surface of the heat transfer tube (22). Further, the oil accumulated in the oil groove (25) can be quickly discharged from the heat exchanger through the oil groove (25).

  Furthermore, in the third invention, a plurality of oil grooves (25) are formed at equal intervals in the circumferential direction of the heat transfer tube (22). Therefore, according to the present invention, the oil on the inner wall surface side of the heat transfer tube (22) can easily enter the oil groove (25), and the amount of oil trapped in each oil groove (25) is made uniform. it can. Therefore, the formation of the oil film described above can be prevented more reliably.

  According to the fourth invention, by providing a plurality of V-shaped oil grooves (25), an oil flow path can be reliably formed in the heat transfer tube (22), and the oil is subjected to heat exchange. Can be discharged quickly from the vessel. Therefore, according to the present invention, a sufficient oil return amount to the compression mechanism or the like can be ensured.

  According to the fifth invention, since the lipophilic layer (27) is formed on the inner wall of the oil groove (25), the oil trapping effect by the oil groove (25) can be improved. Therefore, the formation of the oil film can be prevented more reliably. Further, the captured oil can be reliably circulated in the oil groove (25) and allowed to flow out of the heat exchanger.

  According to the sixth aspect of the invention, since the oil repellent layer (28) is formed on the inner wall surface of the heat transfer tube (22), oil that covers the inner wall surface of the heat transfer tube (22) is supplied to the oil groove (25 ) Can be played inward, and the oil trapping effect by the oil groove (25) can be further improved.

  According to the seventh aspect, since the spiral heat transfer promotion groove (50) is formed on the inner wall surface of the heat transfer tube (22), the surface area of the inner wall surface of the heat transfer tube (22) is increased, and the heat transfer tube (22 ) Heat transfer performance can be further improved.

  According to the eighth invention, since the oil groove (25) extends in the axial direction of the heat transfer tube (22) and intersects with the spiral heat transfer promotion groove (50), the heat transfer promotion groove (50) The accumulated oil can be discharged into the oil groove (25). Therefore, since it is possible to avoid the formation of an oil film in the heat transfer promotion groove (50), it is possible to prevent the heat transfer performance of the heat transfer tube (22) from being deteriorated.

  According to the ninth invention, the plurality of oil grooves (25) are formed at equal intervals in the circumferential direction of the heat transfer tube (22). For this reason, according to the present invention, the oil on the inner wall surface of the heat transfer tube (22) can easily enter the oil groove (25), and the amount of oil trapped in each oil groove (25) can be made uniform. . Therefore, the formation of an oil film on the inner wall surface of the heat transfer tube (22) can be more reliably prevented. In addition, since oil accumulated in each heat transfer promotion groove (50) can be quickly discharged to each oil groove (25), an oil film may be formed in each heat transfer promotion groove (50). It can be surely prevented.

  According to the tenth aspect of the invention, since the opening width of the oil groove (25) is wider than the opening width of the heat transfer promotion groove (50), the oil in the heat transfer pipe (22) is positively supplied to the oil groove (25). Can flow into. According to the eleventh aspect of the invention, since the groove depth of the oil groove (25) is equal to or greater than the groove depth of the heat transfer promotion groove (50), the oil accumulated in the heat transfer promotion groove (50) Can flow down into the oil groove (25). Therefore, according to these inventions, the heat transfer promotion effect by the heat transfer promotion groove (50) can be sufficiently exhibited, and the heat transfer performance of the heat transfer tube (22) can be further improved.

  According to the twelfth invention, in the refrigerating apparatus using carbon dioxide as the refrigerant, the PAG having low compatibility with carbon dioxide can be captured in the oil groove (25). That is, according to the present invention, in the case of a conventional refrigeration apparatus in which an oil film is easily formed on the inner wall surface of the heat transfer tube, such oil film formation can be reliably prevented, and a heat exchanger (12 13), sufficient heat transfer performance can be secured.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Embodiment 1 of the Invention
The heat exchanger according to Embodiment 1 of the present invention is applied to a refrigeration apparatus (1) that performs a vapor compression refrigeration cycle. The refrigeration apparatus of Embodiment 1 constitutes an air conditioner (1) that performs switching between indoor cooling and heating.

<Schematic configuration of refrigerant circuit>
As shown in FIG. 1, the air conditioner (1) includes a refrigerant circuit (10) filled with a refrigerant. The refrigerant circuit (10) is filled with carbon dioxide as a refrigerant. In this air conditioner (1), polyalkylene glycol (PAG), which is a polar oil, is used as a lubricating oil (refrigerating machine oil) for lubricating each sliding portion of the compressor (11). Yes. And this PAG flows out into a refrigerant circuit (10) with the refrigerant discharged from the compressor (11). Accordingly, in the refrigerant circuit (10), carbon dioxide as the refrigerant and PAG as the refrigerating machine oil circulate. In the refrigerant circuit, a refrigeration cycle (so-called supercritical cycle) is performed in which carbon dioxide is compressed to a critical pressure or higher.

  The refrigerant circuit (10) is provided with a compressor (11), an outdoor heat exchanger (12), an indoor heat exchanger (13), and an expansion valve (14).

  The compressor (11) is constituted by, for example, a scroll type compressor. Connected to the compressor (11) are a discharge pipe (11a) through which the refrigerant discharged from the compression mechanism flows and a suction pipe (11b) through which the refrigerant drawn from the compression mechanism flows. The outdoor heat exchanger (12) is disposed in the outdoor space. In the outdoor heat exchanger (12), heat is exchanged between the refrigerant flowing inside and the outdoor air. The indoor heat exchanger (13) is disposed in the indoor space. In the indoor heat exchanger (13), heat is exchanged between the refrigerant flowing in the indoor heat exchanger and the indoor air. The outdoor heat exchanger (12) and the indoor heat exchanger (13) are heat exchangers according to the present invention and constitute a cross fin type heat exchanger.

  The expansion valve (14) is connected between the outdoor heat exchanger (12) and the indoor heat exchanger (13). The expansion valve (14) is composed of, for example, an electronic expansion valve. The refrigerant circuit (10) is provided with a four-way switching valve (15). The four-way selector valve (15) has four ports from first to fourth. In the four-way selector valve (15), the first port is connected to the outdoor heat exchanger (12), the second port is connected to the suction side of the compressor (11), and the third port is the discharge side of the compressor (11). And the fourth port is connected to the indoor heat exchanger (13). The four-way selector valve (15) has a first state (solid line state in FIG. 1) in which the first port and the third port are in communication with each other and a second port and a fourth port in communication with each other; The second port can be switched to a second state (a state indicated by a broken line in FIG. 1) in which the third port and the fourth port are simultaneously communicated with each other.

<Configuration of heat exchanger>
As shown in FIGS. 2 and 3, each heat exchanger (12, 13) includes a plurality of fins (21) and a heat transfer tube (22). The plurality of fins (21) are made of aluminum and have a rectangular plate shape. The fins (21) are arranged in parallel with each other at a predetermined interval.

  The heat transfer tube (22) is constituted by a copper tube. The heat transfer tube (22) has a plurality of straight tube portions (22a) and a curved portion (22b) connecting the straight tube portions (22a). Each straight pipe portion (22a) extends straight in the arrangement direction of the fins (21) and penetrates the fins (21). The curved portion (22b) is attached to the front row and the last row fins (21) among the plurality of fins (21, 21, ...), and the ends of the two straight pipe portions (22a) are connected to each other. Curved to connect.

  As shown in FIGS. 4 and 5, a plurality of oil grooves (25) for capturing and circulating oil in the refrigerant are formed in the inner peripheral wall of the heat transfer tube (22) of each heat exchanger (12, 13). Is formed. In Embodiment 1, four oil grooves (25) are formed in the inner peripheral wall of the heat transfer tube (22). In this embodiment, each oil groove (25) is formed in both the straight pipe part (22a) and the curved part (22b), but each oil groove (25 ) May be formed. Each oil groove (25) includes a pair of inclined surfaces (25a, 25a) that expand radially inward, and a bottom surface (25b) formed between both inclined surfaces (25a, 25a). . That is, each oil groove (25) has a trapezoidal longitudinal section in which the opening area widens toward the radially inner side of the heat transfer tube (22).

  Each oil groove (25) is formed extending in the axial direction of the heat transfer tube (22). That is, each oil groove (25) is formed along the flow direction of the refrigerant flowing through the heat transfer tube (22). Further, the oil grooves (25) are arranged at equal intervals in the circumferential direction of the heat transfer tube (22). Specifically, each oil groove (25) is arranged every 90 degrees in the circumferential direction of the heat transfer tube (22). In addition, it is preferable that the ratio (S2 / S1) of the total cross-sectional area S2 of the vertical cross section of the oil groove (25) with respect to cross-sectional area S1 in the vertical cross section of a heat exchanger tube (22) is 0.01 or more and 0.2 or less. .

-Driving action-
Next, the operation of the air conditioner (1) according to Embodiment 1 will be described. In the refrigerant circuit (10) of the air conditioner (1), the refrigerant circulation direction is switched according to the setting of the four-way switching valve (15). Specifically, the four-way selector valve (15) is in the state indicated by the solid line in FIG. 1 in the cooling operation. As a result, in the cooling operation, a refrigeration cycle is performed in which the outdoor heat exchanger (12) serves as a radiator and the indoor heat exchanger (13) serves as an evaporator. On the other hand, the four-way selector valve (15) is in a state indicated by a broken line in FIG. As a result, in the heating operation, a refrigeration cycle in which the outdoor heat exchanger (12) serves as an evaporator and the indoor heat exchanger (13) serves as a radiator is performed. Hereinafter, the cooling operation of such an air conditioner (1) will be described as a representative.

  In the refrigerant circuit (10) shown in FIG. 1, the refrigerant compressed to the critical pressure or higher by the compressor (11) is discharged from the discharge pipe (11a). In addition, from the compressor (11), the oil utilized for lubrication of each sliding part is discharged with a high pressure refrigerant. Thereafter, the refrigerant flows through the outdoor heat exchanger (12). In the outdoor heat exchanger (12), the high-pressure refrigerant radiates heat to the outdoor air. The high-pressure refrigerant that has radiated heat in the outdoor heat exchanger (12) is decompressed when passing through the expansion valve (14), and becomes a low-pressure refrigerant. Thereafter, the refrigerant flows through the indoor heat exchanger (13). In the indoor heat exchanger (13), the refrigerant absorbs heat from the indoor air and evaporates. As a result, the room is cooled. The refrigerant evaporated in the indoor heat exchanger (13) flows through the suction pipe (11b), is sucked into the compressor (11), and is compressed again.

<Operation of oil groove>
By the way, when the refrigerant flows through the outdoor heat exchanger (12) or the indoor heat exchanger (13) in the above-described cooling operation or heating operation, oil that cannot be dissolved in the refrigerant is separated from the refrigerant and transmitted. It may cover the inner wall of the heat pipe (22). For this reason, in the conventional heat exchanger, the oil film was formed in the whole area of the inner peripheral wall of a heat exchanger tube, and the problem that the heat transfer performance of a refrigerant | coolant and air fell occurred. In particular, as in this embodiment, when carbon dioxide is used as the refrigerant and PAG is used as the refrigerating machine oil, the compatibility of the PAG with carbon dioxide is low, so that the refrigerant and the oil are easily separated. An oil film is easily formed. As a result, there is a problem that the heat transfer performance of each heat exchanger is remarkably lowered, and the cooling capacity and heating capacity of the air conditioner are also lowered. Therefore, in the heat exchanger (12, 13) of the present embodiment, in order to prevent a decrease in heat transfer performance due to the formation of such an oil film, an oil groove (25) is formed on the inner peripheral wall of the heat transfer tube (22). The oil is trapped in the oil groove (25).

  Specifically, for example, when the refrigerant containing oil flows through the indoor heat exchanger (13) in the cooling operation described above, the evaporated gas refrigerant (40) is generated in the heat transfer tube (22) as shown in FIG. The refrigerant flows through the center, and the liquid refrigerant (41) flows outside the gas refrigerant (40). Furthermore, the oil (42) having a relatively high viscosity and high density flows outside the liquid refrigerant (41) while being along the inner peripheral wall of the heat transfer tube (22). Here, the above-mentioned oil groove (25) is formed in the inner peripheral wall of the heat transfer tube (22). For this reason, the oil (42) is drawn into the oil groove (25) by the surface tension and is captured in the oil groove (25). As a result, the oil film as described above is hardly formed on the inner peripheral wall of the heat transfer tube (22), and the liquid refrigerant (41) and the inner peripheral wall of the heat transfer tube (22) are in direct contact. Therefore, in the indoor heat exchanger (13), heat transfer between the room air and the liquid refrigerant is promoted, and the liquid refrigerant evaporates efficiently. On the other hand, the oil trapped in each oil groove (25) flows through each oil groove (25) in the same direction as the gas refrigerant (40) and the liquid refrigerant. And this oil flows out of an indoor heat exchanger (13) rapidly with a refrigerant.

-Effect of Embodiment 1-
In the first embodiment, the oil groove (25) for capturing oil is formed on the inner wall surface of the heat transfer tube (22). For this reason, in the case of a conventional heat exchanger, an oil film is formed over the entire inner wall surface of the heat transfer tube, and the heat transfer performance of the heat exchanger has deteriorated. By capturing the oil on the inner wall surface of the heat transfer tube (22) in the oil groove (25), the formation of the oil film can be suppressed, and the deterioration of the heat transfer performance associated with the formation of the oil film can be prevented. . Further, when the formation of the oil film is prevented in this way, it is possible to prevent the pressure loss of the heat transfer tube (22) from increasing due to the formation of the oil film.

  Moreover, in the said Embodiment 1, since the oil groove (25) is formed in the axial direction of the heat exchanger tube (22), the oil trapped in the oil groove (25) smoothly flows in the oil groove (25). Will flow into. Therefore, it is possible to avoid the oil once trapped in the oil groove (25) from flowing out of the oil groove (25) and covering the inner wall surface of the heat transfer tube (22). Further, the oil accumulated in the oil groove (25) can be quickly discharged from the heat exchanger through the oil groove (25). For this reason, it is possible to avoid oil stagnation in the heat exchanger (12, 13), and it is possible to avoid a shortage of oil return in the compressor (11).

  Further, in the first embodiment, the plurality of oil grooves (25) are formed every 90 degrees in the circumferential direction of the heat transfer tube (22). Therefore, according to the first embodiment, the oil on the inner wall surface side of the heat transfer tube (22) can easily enter the oil groove (25), and the amount of oil trapped in each oil groove (25) can be reduced. It can be made uniform. Therefore, the formation of the oil film described above can be prevented more reliably.

<< Embodiment 2 of the Invention >>
The heat exchanger (12, 13) according to the second embodiment of the present invention is different from the first embodiment in the configuration of the heat transfer tube (22). Specifically, as shown in FIG. 7, the heat transfer tube (22) of the second embodiment has a larger number of oil grooves (25) than that of the first embodiment. The oil groove (25) is formed so as to extend in the axial direction of the heat transfer tube (22), as in the first embodiment.

  In Embodiment 2, the bottom surface (25b) of the oil groove (25) is coated with a lipophilic layer (27) made of a lipophilic material. In addition, as a lipophilic material which comprises a lipophilic layer (27), water glass, an acryl, an epoxy resin, polyvinyl alcohol, etc. are mentioned. On the other hand, an oil repellent layer (28) made of an oil repellent material is coated on the entire inner wall surface of the heat transfer tube (22) outside the oil groove (25). The oil repellent material constituting the oil repellent layer (28) includes Teflon, fluorine, paraffin, and silicon materials.

  As shown in FIG. 8, in the heat exchanger (12, 13) of the second embodiment, when the refrigerant flows through the heat transfer tube (22), the oil (42) near the inner wall surface of the heat transfer tube (22) It is bounced by the oil repellent layer (28) and enters the oil groove (25). Furthermore, since the lipophilic layer (27) is formed inside the oil groove (25), the oil is efficiently captured in the oil groove (25). As a result, in the second embodiment, an oil film is hardly formed on the inner wall surface of the heat transfer tube (22), and the oil trapped in the oil groove (25) is quickly exchanged through the oil groove (25). Escape from (12,13).

-Effect of Embodiment 2-
Also in the said Embodiment 2, it can prevent that an oil film will be formed in the inner wall face of a heat exchanger tube (22) by forming an oil groove (25) in a heat exchanger tube (22). Furthermore, an oil repellent layer (27) is formed on the inner wall surface of the oil groove (25), while an oil repellent layer (28) is formed on the inner wall surface of the heat transfer tube (22) other than the oil groove (25). ing. For this reason, according to Embodiment 2, the oil trapping effect by the oil groove (25) can be improved, and the formation of the oil film can be more reliably prevented. Moreover, according to the said Embodiment 2, the captured oil can be reliably distribute | circulated in an oil groove | channel (25), and can be made to flow out from a heat exchanger.

-Modification of Embodiment 2-
Only one of the lipophilic layer (27) and the oil repellent layer (28) of the second embodiment may be provided on the heat transfer tube (22). Further, the oleophilic layer (27) may be formed on the inclined surface (25a) of the oil groove (25). Moreover, you may make it apply the lipophilic layer (27) and oil-repellent layer (28) similar to Embodiment 2 about the heat exchanger (12, 13) of Embodiment 1 mentioned above.

<< Embodiment 3 of the Invention >>
The heat exchanger (12, 13) according to Embodiment 3 of the present invention is different from the above Embodiments 1 and 2 in the configuration of the heat transfer tube (22). Specifically, as shown in FIG. 9, a plurality of oil grooves (25) extending in a V shape are formed on the inner wall surface of the heat transfer tube (22) of the third embodiment. The V-shaped oil groove (25) is formed so that the tip ends of a pair of grooves (25c, 25c) inclined obliquely from the axial direction of the heat transfer tube (22) are connected. The oil grooves (25) are arranged at predetermined intervals in the axial direction of the heat transfer tube (22). In each oil groove (25), the V-shaped tip (25d) to which the pair of grooves (25c, 25c) is connected is formed to face the refrigerant outflow side in the heat transfer tube (22). That is, in each oil groove (25), each V-shaped tip (25d) is directed to one side in the axial direction of the heat transfer tube (22). Furthermore, the row group of each oil groove (25) is connected so as to be continuous with the row group of other oil grooves (25) adjacent in the circumferential direction. A groove is formed.

  As shown in FIG. 10, in the heat exchanger (12, 13) of the third embodiment, when the refrigerant flows through the heat transfer tube (22), the oil (42) near the inner wall surface of the heat transfer tube (22) , Enters each groove (25c, 25c) and flows to the V-shaped tip (25d) side. In this way, in each oil groove (25), the captured oil flows to the V-shaped tip (25d), so that the V-shaped tip ( 25d) is formed as an oil flow path. The oil captured as described above flows out from the heat exchanger (12, 13) through the oil grooves (25) and the oil flow paths connecting the oil grooves (25).

-Effect of Embodiment 3-
Also in the said Embodiment 3, it can prevent that an oil film will be formed in the inner wall face of a heat exchanger tube (22) by forming an oil groove (25) in a heat exchanger tube (22). Further, in the third embodiment, by providing a plurality of V-shaped oil grooves (25), it is possible to reliably form the captured oil flow path, and this oil is removed from the heat exchanger (12, 13). It can be discharged quickly. Therefore, according to the third embodiment, it is possible to reliably avoid the shortage of the oil return amount of the compressor (11).

<< Embodiment 4 of the Invention >>
The heat exchanger (12, 13) according to Embodiment 4 of the present invention is different from the above embodiments in the configuration of the heat transfer tube (22). Specifically, as shown in FIGS. 11 to 14, a plurality of heat transfer promotion grooves (50) for promoting heat transfer are formed on the inner wall surface of the heat transfer tube (22) of the fourth embodiment. Yes. Each heat transfer promotion groove (50) is formed in a spiral shape that turns in the circumferential direction of the heat transfer tube (22), and is parallel to each other. The shape of the longitudinal section of the heat transfer promoting groove (50) is a substantially trapezoidal shape or a substantially triangular shape such that the opening area expands toward the open side.

  On the inner wall surface of the heat transfer tube (22) of the fourth embodiment, four oil grooves (25) are formed in the same manner as in the above embodiments. Each oil groove (25) extends in the axial direction of the heat transfer tube (22), and is arranged every 90 degrees in the circumferential direction of the heat transfer tube (22). The oil groove (25) does not necessarily extend in a straight line, and the twist angle may be in the range of 0 degrees to 5 degrees. Moreover, the shape of the vertical cross section of the oil groove (25) is substantially trapezoidal so that the opening area is expanded toward the open portion side.

  Each oil groove (25) intersects these heat transfer promotion grooves (50) so as to cross the plurality of heat transfer promotion grooves (50). That is, as shown in FIG. 13 (a perspective view in which the inner wall surface of the heat transfer tube is enlarged), both ends in the longitudinal direction of the spiral heat transfer promotion groove (50) are connected to the respective oil grooves (25). .

  Further, as shown in FIG. 14, the opening width W1 of each oil groove (25) is wider than the opening width W2 of each heat transfer promoting groove (50). In addition, the groove depth D1 of each oil groove (25) is the same as the groove depth D2 of each heat transfer promotion groove (50). The groove depth D1 may be larger than the groove depth D2, and it is sufficient that the groove depth D1 is equal to or greater than the groove depth D2. The opening width W1 of the oil groove (25) is preferably in the range of 0.2 mm to 1.0 mm.

  In the heat exchanger (12, 13) of the fourth embodiment, when the refrigerant flows through the heat transfer tube (22), the oil (42) in the heat transfer tube (22) enters the oil groove (25). In the fourth embodiment, the oil (42) may enter the heat transfer promotion grooves (50). The oil (42) passes through the heat transfer promotion grooves (50) to the oil groove (25). It is discharged (see FIG. 13). Therefore, formation of an oil film in each heat transfer promotion groove (50) is prevented. As described above, the oil (42) trapped in the oil groove (25) flows out from the heat exchanger (12, 13) through the oil groove (25).

-Effect of Embodiment 4-
According to the fourth embodiment, since the spiral heat transfer promotion groove (50) is formed on the inner wall surface of the heat transfer tube (22), the surface area of the inner wall surface of the heat transfer tube (22) is increased, and the heat transfer tube (22) The heat transfer performance can be further improved. Also, since the oil groove (25) extends in the axial direction of the heat transfer tube (22) and intersects with the spiral heat transfer promotion groove (50), oil accumulated in the heat transfer promotion groove (50) (25) can be discharged. Therefore, since it is possible to avoid the formation of an oil film in the heat transfer promotion groove (50), it is possible to prevent the heat transfer performance of the heat transfer tube (22) from being deteriorated.

  In the fourth embodiment, four oil grooves (25) are formed at equal intervals in the circumferential direction of the heat transfer tube (22). Thereby, the oil on the inner wall surface of the heat transfer tube (22) can easily enter the oil groove (25), and the amount of oil trapped in each oil groove (25) can be made uniform. Therefore, the formation of an oil film on the inner wall surface of the heat transfer tube (22) can be more reliably prevented. In addition, since oil accumulated in each heat transfer promotion groove (50) can be quickly discharged to each oil groove (25), an oil film may be formed in each heat transfer promotion groove (50). It can be surely prevented.

  Furthermore, in the said Embodiment 4, since the opening width W1 of the oil groove (25) was made larger than the opening width W2 of the heat-transfer acceleration | stimulation groove | channel (50), the oil in a heat-transfer tube (22) is actively made into an oil groove ( 25). Further, since the groove depth D1 of the oil groove (25) is set to be equal to or greater than the groove depth D2 of the heat transfer promoting groove (50), the oil accumulated in the heat transfer promoting groove (50) is surely removed. It can flow down into. Therefore, the heat transfer promotion effect by the heat transfer promotion groove (50) can be sufficiently exhibited, and the heat transfer performance of the heat transfer tube (22) can be further improved.

<< Other Embodiments >>
About the said embodiment, it is good also as the following structures.

  The shape of the oil groove (25) formed in the inner peripheral wall of the heat transfer tube (22) may be other than those described in the above embodiments. That is, the oil groove (25) may be spiral or meandering, and its longitudinal section may be triangular, elliptical, or semicircular.

  The number of the oil grooves (25) is not limited to four. For example, the number of oil grooves (25) may be one or more.

  Further, in each of the above embodiments, the heat exchanger (12, 13) according to the present invention is applied to a refrigeration apparatus that uses carbon dioxide as the refrigerant and PAG as the refrigerating machine oil. Alternatively, the heat exchanger (12, 13) may be applied to a refrigeration apparatus that uses refrigeration oil. Specifically, examples of the refrigerant include R134a, R410a, R407c, and R32, and examples of the refrigerating machine oil include poly-α-olefin, P06, and fluorine-based oil.

  In addition, the above embodiment is an essentially preferable illustration, Comprising: It does not intend restrict | limiting the range of this invention, its application thing, or its use.

  As described above, the present invention is useful for a heat exchanger applied to a refrigeration apparatus that performs a refrigeration cycle.

FIG. 1 is a piping diagram illustrating a schematic configuration of a refrigerant circuit of a refrigeration apparatus according to Embodiment 1. FIG. 2 is a perspective view illustrating a schematic configuration of the heat exchanger according to the first embodiment. FIG. 3 is an elevation view illustrating a schematic configuration of the heat exchanger according to the first embodiment. FIG. 4 is a perspective view showing the inside of the heat transfer tube of the heat exchanger according to the first embodiment. FIG. 5 is a longitudinal sectional view of a heat transfer tube of the heat exchanger according to the first embodiment. FIG. 6 is an explanatory diagram of an oil trapping action in the heat transfer tube of the heat exchanger according to the first embodiment. FIG. 7 is a longitudinal sectional view of a part of the heat transfer tube of the heat exchanger according to the second embodiment. FIG. 8 is an explanatory diagram of an oil trapping action in the heat transfer tube of the heat exchanger according to the second embodiment. FIG. 9 is a perspective view showing the inside of the heat transfer tube of the heat exchanger according to the third embodiment. FIG. 10 is an explanatory diagram of an oil trapping action in the heat transfer tube of the heat exchanger according to the third embodiment. FIG. 11 is a perspective view showing the inside of a heat exchanger tube according to the fourth embodiment by breaking the heat transfer tube. FIG. 12 is a longitudinal sectional view of a heat transfer tube of the heat exchanger according to the fourth embodiment. FIG. 13 is an enlarged perspective view of the inner wall surface of the heat transfer tube of the heat exchanger according to the fourth embodiment. FIG. 14 is an explanatory diagram illustrating the relationship between the dimensions of the oil groove and the heat transfer promotion groove by enlarging the inner wall surface of the heat transfer tube of the heat exchanger according to the fourth embodiment.

Explanation of symbols

1 Air conditioner (refrigeration equipment)
10 Refrigerant circuit
12 Indoor heat exchanger (heat exchanger)
13 Outdoor heat exchanger (heat exchanger)
22 Heat transfer tube
25 Oil groove
27 Lipophilic layer (Lipophilic material)
28 Oil repellent layer (oil repellent material)
50 Heat transfer enhancement groove

Claims (12)

A heat exchanger that is applied to a refrigeration apparatus that performs a vapor compression refrigeration cycle and has a heat transfer tube (22) through which a refrigerant flows,
The heat exchanger is characterized in that an oil groove (25) for capturing and circulating oil in the refrigerant is formed on the inner wall surface of the heat transfer tube (22). In claim 1,
The heat exchanger, wherein the oil groove (25) extends in an axial direction of the heat transfer tube (22). In claim 2,
A heat exchanger in which a plurality of the oil grooves (25) are arranged at equal intervals in the circumferential direction on the inner wall surface of the heat transfer tube (22). In claim 1,
A heat exchanger in which a plurality of oil grooves (25) extending in a V shape are arranged in the axial direction of the heat transfer tube (22) on the inner wall surface of the heat transfer tube (22). In any one of Claims 1 thru | or 4,
A heat exchanger characterized in that a lipophilic layer (27) made of a lipophilic material is formed on the inner wall surface of the oil groove (25). In any one of Claims 1 thru | or 5,
An oil repellent layer (28) made of an oil repellent material is formed on a portion other than the oil groove (25) on the inner wall surface inside the heat transfer tube (22). In claim 1,
The inner wall surface of the heat transfer tube (22) is provided with a plurality of heat transfer promotion grooves (50) that are formed in a spiral shape that rotates in the circumferential direction of the heat transfer tube (22) and promote heat transfer. A heat exchanger characterized by that. In claim 7,
The heat exchanger, wherein the oil groove (25) extends in the axial direction of the heat transfer tube (22) while intersecting with the heat transfer promotion groove (50). In claim 8,
A heat exchanger in which a plurality of the oil grooves (25) are arranged at equal intervals in the circumferential direction on the inner wall surface of the heat transfer tube (22). In any one of Claims 7 thru | or 9,
The heat exchanger characterized in that the opening width of the oil groove (25) is wider than the opening width of the heat transfer promotion groove (50). In any one of claims 7 to 10,
The heat exchanger characterized in that the groove depth of the oil groove (25) is equal to or greater than the groove depth of the heat transfer promotion groove (50). A refrigeration apparatus comprising a refrigerant circuit (10) for performing a vapor compression refrigeration cycle,
In the refrigerant circuit (10), carbon dioxide as a refrigerant and polyalkylene glycol as a refrigerating machine oil circulate, and a heat exchanger (12, 13) according to any one of claims 1 to 11 is provided. A refrigeration apparatus characterized by that.

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