JP2016020757A - Manufacturing method for refrigeration cycle device and cross fin tube type heat exchanger used for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve performance improvement of a heat exchanger by reducing contact thermal resistance between a fin and a heat transfer pipe while suppressing crush of a crest part of a fin groove provided inside the heat transfer pipe, and to facilitate assembly work of the heat exchanger.SOLUTION: A refrigeration cycle device is configured by sequentially connecting a compressor, a heat source side heat exchanger 7, an expansion device and a utilization side heat exchanger by refrigerant piping. The heat source side heat exchanger is a cross fin tube type heat exchanger which includes: a heat transfer pipe 30 which is configured by an aluminum-based material and in which a fin groove is formed on an inner surface; and a fin 20 configured by an aluminum-based material and in which a through-hole 20a for passing the heat transfer pipe is formed. The through-hole is formed to have a diameter larger than an outer diameter of the heat transfer pipe, and after the heat transfer pipe is passed through the through-hole, the heat transfer pipe is expanded and joined so that the outer diameter of the heat transfer pipe is larger than the diameter of the through-hole, and a pipe expansion rate becomes below 1.5%, and the joint portion is brazed.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a refrigeration cycle apparatus such as an air conditioner or a refrigerator using a refrigeration cycle, and a method of manufacturing a cross fin tube heat exchanger used therefor, and in particular, a cross fin using an aluminum heat transfer tube. The present invention relates to a refrigeration cycle apparatus equipped with a tube heat exchanger.

  As a conventional heat exchanger used in a refrigeration cycle apparatus such as an air conditioner, a cross fin tube type composed of a plurality of aluminum (hereinafter also simply referred to as aluminum) fins and a plurality of copper heat transfer tubes Heat exchangers are commonly used. In order to improve the performance of this cross fin tube heat exchanger, it is effective to improve the adhesion between the fin and the heat transfer tube and reduce the thermal resistance (contact heat resistance) between the fin and the heat transfer tube. . Further, the cross fin tube type heat exchanger is provided with fin grooves on the inner surface of the heat transfer tube to improve the performance, thereby increasing the heat exchange amount on the refrigerant side.

  On the other hand, a heat exchanger is also known in which the material of the heat transfer tube is changed from copper to aluminum in order to reduce the weight and cost of the cross fin tube heat exchanger. In the cross fin tube heat exchanger composed of the aluminum fins and the aluminum heat transfer tubes, the fins have a cross-sectional area larger than the outer diameter of the heat transfer tubes in order to ensure adhesion between the fins and the heat transfer tubes. A through hole is formed, and the heat transfer tube is passed through the through hole. Then, a ball portion having a diameter larger than the inner diameter of the heat transfer tube is passed inside the heat transfer tube to apply mechanical pressure to expand the heat transfer tube. And the method of sticking the said fin and the said heat exchanger tube by enlarging the outer diameter is known. Examples of this kind of publicly known example include those described in Japanese Patent Application Laid-Open No. 2001-289585 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2011-153823 (Patent Document 2).

  Moreover, what was described in Unexamined-Japanese-Patent No. 8-247678 (patent document 3) is also known as a conventional heat exchanger. The one described in Patent Document 3 is an aluminum heat exchanger composed of a plurality of aluminum fins and a plurality of aluminum flat heat transfer tubes, and the fins are set slightly smaller than the cross-sectional area of the flat heat transfer tubes. The flat heat transfer tube is press-fitted and passed through the slit portion, thereby ensuring the adhesion between the flat heat transfer tube and the fin by the elastic force of the fin. And when adhesiveness is further required, after press-fitting a flat heat exchanger tube into a fin, brazing or adhere | attaching a fin and a heat exchanger tube is described.

JP 2001-289585 A JP 2011-153823 A JP-A-8-247678

  In the above-mentioned Patent Document 1 and Patent Document 2, by devising the shape of the fin groove inside the aluminum heat transfer tube, even if the pipe is expanded by mechanical pressure, the performance degradation due to the collapse of the fin groove is minimized. To be able to.

  However, in order to sufficiently reduce the contact thermal resistance between the fin and the heat transfer tube, it is necessary to set the tube expansion rate so that the fin and the heat transfer tube can be sufficiently adhered to each other. Here, the tube expansion rate is “(diameter of through-hole through which heat transfer tube provided in fin after tube expansion passes / diameter of through-hole through heat transfer tube provided in fin before tube expansion) × 100 [%]” It is. As the pressure applied to the inside of the heat transfer tube increases, the tube expansion rate can be increased. However, as the pressure applied to the inside of the heat transfer tube increases, the crush of the peak portion of the fin groove provided on the inner surface of the heat transfer tube increases.

  Setting the contact thermal resistance to a small value means setting the pipe expansion rate to a large value. In order to sufficiently reduce the contact thermal resistance, it is desirable to set the pipe expansion rate from 1.5% to 3.5%. When such a tube expansion ratio is used, the crushing of the peak portion of the fin groove tends to increase. That is, it can be expected to reduce the contact thermal resistance between the fin and the heat transfer tube, but the crest of the fin groove provided on the inner surface of the heat transfer tube becomes larger, and the amount of heat exchange on the refrigerant side flowing in the heat transfer tube is reduced. Since the reduction occurs, there is a problem that the performance of the heat exchanger cannot be sufficiently improved as a whole.

  In the thing of the said patent document 3, the slit part set slightly smaller than the cross-sectional area of a flat heat exchanger tube is formed in a fin, and the said flat heat exchanger tube is press-fitted through this slit part, By the elastic force of a fin It is described to ensure the adhesion between the flat heat transfer tube and the fin. However, in this Patent Document 3, when manufacturing a heat exchanger, it is necessary to press-fit the flat heat transfer tube through the slit portion in which the cross-sectional area formed in the plurality of fins is set to be slightly small. Therefore, it takes a lot of time to assemble the heat exchanger, and there is a problem that the manufacturability is poor.

  An object of the present invention is to improve the performance of the heat exchanger by reducing the contact thermal resistance between the fin and the heat transfer tube while suppressing the crushing of the peak portion of the fin groove provided in the heat transfer tube, and the heat exchanger It is an object of the present invention to obtain a refrigeration cycle apparatus equipped with a heat exchanger with good manufacturability that can be easily assembled, and a method for producing a cross fin tube heat exchanger used therefor.

  In order to solve the above problems, the present invention provides a refrigeration cycle apparatus configured by sequentially connecting a compressor, a heat source side heat exchanger, an expansion device, and a use side heat exchanger with refrigerant pipes, and the heat source side heat The exchanger includes a heat transfer tube made of an aluminum-based material and having fin grooves formed on the inner surface thereof, and a cross comprising a fin made of an aluminum-based material and having a through hole for passing the heat transfer tube In the fin tube heat exchanger, the through hole of the fin is formed to have a larger diameter than the outer diameter of the heat transfer tube, and after passing the heat transfer tube through the through hole, the outer diameter of the heat transfer tube is The heat transfer tube is expanded and joined so as to be larger than the diameter of the through hole and the tube expansion rate is less than 1.5%, and this joined portion is brazed.

  Another feature of the present invention is a method of manufacturing a cross fin tube heat exchanger used in a refrigeration cycle apparatus, a heat transfer tube that is made of an aluminum material and has fin grooves formed on the inner surface, and an aluminum material. And a fin in which a through-hole having a diameter larger than the outer diameter of the heat transfer tube is formed, and after passing the heat transfer tube through the through-hole of the fin, the outer diameter of the heat transfer tube is increased. The pipe is expanded so that the diameter of the through hole is larger than the diameter and the expansion ratio is less than 1.5%, and then the fin and the heat transfer pipe are brazed and joined.

  According to the present invention, it is possible to improve the performance of the heat exchanger while reducing the contact thermal resistance between the fin and the heat transfer tube while suppressing the crushing of the peak portion of the fin groove provided in the heat transfer tube. There is an effect that it is possible to obtain a refrigeration cycle apparatus equipped with a heat exchanger with good manufacturability that can be easily assembled, and a method of manufacturing a cross fin tube heat exchanger used therefor.

The refrigeration cycle system | strain diagram which shows Example 1 of the refrigeration cycle apparatus of this invention. FIG. 2 is a perspective view of a main part of a cross fin tube type heat exchanger used in the outdoor heat exchanger of FIG. The diagram which shows the relationship between the contact thermal resistance of the fin and heat exchanger tube which were joined only by the pipe expansion, and the pipe expansion rate. The figure explaining the joining state of the fin and heat transfer tube which were joined only by the pipe expansion. It is sectional drawing which shows the principal part of the cross fin tube type heat exchanger in Example 1 of this invention, and is a figure which shows the state before expanding a heat exchanger tube. It is sectional drawing which shows the principal part of the cross fin tube type heat exchanger in Example 1 of this invention, and is a figure which shows the state after expanding a heat exchanger tube. It is sectional drawing which shows the principal part of the cross fin tube type heat exchanger in Example 1 of this invention, and is a figure which shows the state after brazing a fin and a heat exchanger tube. The principal part sectional drawing explaining the principal part of the cross fin tube type heat exchanger in Example 2 of this invention. The figure explaining the state which the water droplet adhered to the fin surface of a cross fin tube type heat exchanger.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. Note that, in each drawing, the portions denoted by the same reference numerals indicate the same or corresponding portions.

A first embodiment of the refrigeration cycle apparatus of the present invention will be described with reference to FIGS.
FIG. 1 is a refrigeration cycle system diagram showing the refrigeration cycle apparatus of the first embodiment. In FIG. 1, 1 is an outdoor unit, 2 is an indoor unit, and these outdoor unit 1 and indoor unit 2 are refrigerant pipes (liquid The side connection pipe 3 and the gas side connection pipe 4) are connected.

  The outdoor unit 1 is provided with a compressor (sealed compressor) 5, a four-way valve 6, an outdoor heat exchanger 7, a first expansion device 8, an accumulator 9, and the like. Further, a liquid blocking valve 10 connected to the liquid side connecting pipe 3 and a gas blocking valve 11 connected to the gas side connecting pipe 4 are provided.

  The indoor unit 2 includes a use-side heat exchanger 12 and a second expansion device 13.

  When performing cooling operation, it operates as follows. That is, the high-temperature and high-pressure gas refrigerant compressed by the compressor 5 is discharged from the compressor 1 together with the refrigerating machine oil, and then flows into the heat source side heat exchanger 7 through the four-way valve 6 where outdoor air or cooling is performed. Heat-condensed with water to condense into liquid. The condensed and liquefied refrigerant passes through the fully expanded first expansion device 8 and is sent to the indoor unit 2 through the liquid blocking valve 10 and the liquid side connection pipe 3. The liquid refrigerant flowing into the indoor unit 2 is decompressed and expanded by the second expansion device 13 and becomes a low-temperature / low-pressure gas-liquid two-phase flow and enters the use-side heat exchanger 12 where indoor air or the like The user-side medium is cooled by exchanging heat with the user-side medium, and evaporates and gasifies itself. Thereafter, the gas refrigerant constitutes a refrigeration cycle in which the gas refrigerant passes through the gas side connection pipe 4 and returns to the compressor 1 through the gas blocking valve 11, the four-way valve 6 and the accumulator 9. Excess refrigerant in the refrigeration cycle is stored in the accumulator 9 so that the operating pressure and temperature of the refrigeration cycle are maintained in a normal state.

  When heating operation is performed, the operation is as follows. That is, the high-temperature and high-pressure gas refrigerant compressed by the compressor 1 is discharged from the compressor 1 together with the refrigerating machine oil, and passes through the four-way valve 6, the gas blocking valve 11, and the gas side connection pipe 4, and the use side heat exchanger of the indoor unit 2. 12, and heat-exchanges with the use side medium such as room air to heat the use side medium, and condensates itself. The condensed and liquefied refrigerant is reduced in pressure by the first expansion device 4 via the liquid side connection pipe 3 and the liquid blocking valve 10, and is evaporated by exchanging heat with a heat source medium such as outdoor air or water in the heat source side heat exchanger 7.・ Gasify. The evaporated and gasified refrigerant constitutes a refrigeration cycle in which the refrigerant returns to the compressor 1 through the four-way valve 6 and the accumulator 9.

  In the present embodiment, the heat source side heat exchanger 7 in the refrigeration cycle apparatus shown in FIG. 1 is composed of a plurality of heat transfer tubes that are made of an aluminum-based material and have fin grooves formed on the inner surface, and an aluminum-based material. And a cross fin tube type heat exchanger provided with a plurality of fins in which through holes for passing the heat transfer tubes are formed. The aluminum material is aluminum or an aluminum alloy.

The configuration of the cross fin tube type heat exchanger used in the outdoor heat exchanger 7 will be described with reference to FIG. FIG. 2 is a perspective view of an essential part of the cross fin tube type heat exchanger.
The configuration of the cross fin tube heat exchanger will be described with reference to FIG. In FIG. 2, 20 is a plurality of fins made of an aluminum-based material, and 30 is a plurality of heat transfer tubes also made of an aluminum-based material. Each fin 20 is formed with a through-hole 20a through which the heat transfer tube 30 passes, and the through-hole 20a is formed to have a diameter larger than the outer diameter of the heat transfer tube 30.

  The cross fin tube heat exchanger is assembled by first passing the heat transfer tube 30 through the through hole 20a of the fin 20 and setting the heat transfer tube 30 in a state where a plurality of fins 20 are laminated. Thereafter, the heat transfer tube 30 was expanded so that the outer diameter of the heat transfer tube 30 was larger than the diameter of the through-hole 20a and the tube expansion rate was less than 1.5%, and the heat transfer tube 30 was laminated. The plurality of fins 20 are joined. After this joining, the fins 20 and the heat transfer tubes 30 are tightly fixed by brazing the joined parts. Thereby, the cross fin tube type heat exchanger which improved the adhesiveness of the said fin 20 and the heat exchanger tube 30 can be obtained.

As the expansion method of the heat transfer tube 30, the rod provided with a sphere having an outer diameter larger than the inner diameter of the heat transfer tube 30 is passed through the heat transfer tube 30 to expand the heat transfer tube 30 from the inside. There are a mechanical pipe expanding system, a hydraulic pipe expanding system in which a spherical portion having an outer diameter larger than the inner diameter of the heat transfer tube 30 is pushed by a fluid hydraulic pressure.
In FIG. 2, 14 is a bottom base of the outdoor unit 1, and 15 is an insulating material provided between the outdoor heat exchanger 7 and the bottom base 14. In addition, the heat transfer tube 30 and the fin 20 are made of different aluminum materials so that the potential of the fin 20 is lower than the potential of the heat transfer tube 30, and the fin 20 is corroded first, so that the corrosion of the heat transfer tube 30 is delayed.

  Next, the relationship between the said pipe expansion rate and the contact thermal resistance of a fin and a heat exchanger tube is demonstrated using FIG.3 and FIG.4. FIG. 3 is a diagram showing the relationship between the contact thermal resistance between the fin and the heat transfer tube joined only by the tube expansion and the tube expansion rate, and FIG. 4 is a diagram for explaining the joining state of the fin and the heat transfer tube joined only by the tube expansion. .

  First, the relationship between the contact thermal resistance and the tube expansion rate will be described with reference to FIG. As described above, the expansion rate is “(the diameter of the through hole through which the heat transfer tube provided in the fin after the expansion passes / the diameter of the through hole through which the heat transfer tube provided in the fin before the expansion is expanded−1) × 100 [%] Is. That is, FIG. 3 shows the relationship between the tube expansion ratio based on the diameter of the through hole 20a of the fin 20 (including the inner diameter of the collar portion 20b) and the contact thermal resistance between the fin 20 and the heat transfer tube 30. It is.

  As shown in FIG. 3, the larger the tube expansion ratio, the smaller the contact thermal resistance. Therefore, the heat exchange performance on the fin side (air side) is increased. In order to sufficiently reduce the contact thermal resistance by expanding the heat transfer tube 30, it is desirable to set the tube expansion rate to 1.5% or more. However, if the tube expansion rate exceeds 3.5%, the fins 20 installed perpendicular to the heat transfer tubes 30 fall down, increasing the ventilation resistance of the outdoor heat exchanger 7, and the outdoor heat exchanger 7. The performance of is reduced. For this reason, it is known that the tube expansion ratio is set to 1.5 to 3.5% in the conventional one.

  However, as the tube expansion ratio is increased, the crest of the fin groove provided on the inner surface of the heat transfer tube 30 tends to increase (hereinafter sometimes referred to simply as the fin groove crush). Since the amount of heat exchange on the refrigerant side flowing through the inner surface of the refrigerant 30 decreases, the larger the pipe expansion rate, the more the heat exchange performance on the refrigerant side decreases.

  In particular, since the aluminum-based material is inferior in mechanical properties to copper, when the heat transfer tube 30 is made of an aluminum-based material, it is necessary to set the wall thickness of the heat transfer tube 30 to be larger than that of the copper heat transfer tube. As the rate increases, the load for expanding the heat transfer tube 30 tends to increase. Therefore, the larger the tube expansion rate, the larger the manufacturing apparatus for expanding the heat transfer tube 30 and the equipment cost.

  FIG. 4 is a diagram for explaining a joined state of the fin 20 and the heat transfer tube 30 that are joined only by the pipe expansion. FIG. 4A is a diagram showing a part of one fin 20 joined to the heat transfer pipe 30 by the pipe expansion. (B) The figure is an enlarged view of the A section in (a) figure.

  The heat transfer tube 30 is expanded by a ball portion (expanded ball) that passes through the inside of the heat transfer tube 30, but the tube expansion rate increases as the pressure to expand (surface pressure acting on the inner surface of the heat transfer tube) increases. However, as the pressure for expanding the pipe increases, the surface pressure acting on the peak of the fin groove installed in the heat transfer tube 30 increases, and the collapse of the fin groove peak increases.

  Moreover, although the fin 20 and the heat transfer tube 30 can be joined by expanding the heat transfer tube 30, the collar part 20b of the fin 20 also expands radially outward by expanding the heat transfer tube 30. At that time, since the collar portion 20b of the fin 20 is thin, it does not completely stick to the outer surface of the heat transfer tube 30 and expands. As shown in FIG. Become. For this reason, a space (air layer) 16 in which the fins 20 and the heat transfer tubes 30 are not in contact is formed, and air exists in the space 16. Since the thermal conductivity of air is 0.024 [W / m · K], which is extremely small, the space 16 has a thermal resistance that hinders heat transfer between the fins 20 and the heat transfer tubes 30.

From the above, it is preferable to set the tube expansion rate as small as possible.
Therefore, in this embodiment, the tube is expanded so that the outer diameter of the heat transfer tube 30 is larger than the diameter of the through hole 20a provided in the fin 20, and the tube expansion rate is less than 1.5%, preferably 1. The pipes are expanded to a degree slightly exceeding 0% (for example, 1.1 to 1.3%), the fins 20 and the heat transfer tubes 30 are joined, and the joined portions are brazed. By doing in this way, since the crush of the peak part of the fin groove provided in the inner surface of the heat transfer tube 30 is minimized and the tube expansion rate is reduced, the manufacturing apparatus for expanding the heat transfer tube 30 can be reduced in size, It can also be suppressed that the fin collar portion 20b has a wavy shape. Furthermore, in this embodiment, since the joint portion of the fin 20 and the heat transfer tube 30 is brazed after the expansion, a sufficient amount of brazing material can be filled between the fin 20 and the heat transfer tube 30, and the space 16 described above. Even if this occurs, the space 16 is filled with a brazing material during brazing. As a result, according to the present embodiment, since an air layer can be prevented from being generated between the fins 20 and the heat transfer tubes 30 and they can be closely fixed, the contact thermal resistance can be greatly reduced.

  Next, an example of the manufacturing method of the said cross fin tube type heat exchanger used for the refrigeration cycle apparatus mentioned above is demonstrated using FIGS. 5 is a cross-sectional view of the main part of the cross fin tube type heat exchanger shown in FIG. 2, showing a state before the heat transfer tube is expanded, and FIG. 6 is a cross sectional view of the main part of the cross fin tube type heat exchanger. FIG. 7 is a cross-sectional view of an essential part of the cross fin tube heat exchanger, and shows a state after the fins and the heat transfer tubes are brazed.

  First, a plurality of heat transfer tubes 30 (heat transfer tubes 30a before being expanded) made of an aluminum material and a plurality of fins 20 made of an aluminum material are prepared. Fin grooves (not shown) are formed on the inner surfaces of the plurality of heat transfer tubes 30, and the plurality of fins 20 have through holes 20a having a diameter larger than the outer diameter of the heat transfer tubes 30a before the tube expansion. And a collar portion 20b forming the through hole 20a.

  As shown in FIG. 5, the fin 20 is a brazing sheet in which a brazing material layer 22 made of an aluminum alloy having a melting point lower than that of the core material 21 is bonded to the surface of a fin core material 21 made of aluminum or an aluminum alloy. And is formed into a fin having a through hole 20a by pressing. The brazing sheet is standardized in Japanese Industrial Standard JIS Z3263.

  Next, as shown in FIG. 5, the heat transfer tubes 30a are passed through the through holes 20a of the fins 20, and a plurality of fins 20 are stacked at a predetermined interval by the collar portions 20b before the heat transfer tubes 30a are expanded. Set to. In this state, a gap 17 is formed between the through hole 20a of the fin 20 and the heat transfer tube 30a.

  Thereafter, the fin 20 is elastically deformed by expanding the tube so that the outer diameter of the heat transfer tube 30 is larger than the diameter of the through hole 20a as shown in FIG. And it joins with the heat exchanger tube 30b after a pipe expansion. In this embodiment, the heat transfer tube 30 is expanded so that the expansion rate of the heat transfer tube 30 is less than 1.5%, and is joined to the plurality of stacked fins 20.

  By doing in this way, it can suppress small that the peak part of the said fin groove formed in the inner surface of the said heat exchanger tube 30 is crushed at the time of pipe expansion, and the fall of the heat exchange amount by the side of the refrigerant | coolant which flows through the inside of a heat exchanger tube is reduced. Can be suppressed.

  Next, when the entire heat exchanger in the state shown in FIG. 6 is placed in a heating furnace (not shown) and heated, the brazing filler metal layer 22 on the surface of the fin core material 21 melts, and as shown in FIG. And the heat transfer tube 30 can be tightly fixed with a molten brazing material 22a.

  That is, in the present embodiment, as described above, since the tube expansion rate is reduced and the joining portion of the fin 20 and the heat transfer tube 30 is brazed, the brazing material 22a is melted by heating and decreases in viscosity. It is pushed out from between the fin 20 and the heat transfer tube 30 by the elastic force of the fin 20. Thereby, the fin 20 and the heat transfer tube 30 are in close contact with each other, as shown in FIG. 4B, even when the space 16 is generated between the fin 20 and the heat transfer tube 30b after the expansion. Since the space 16 is filled with the brazing material 22a, an air layer that hinders heat transfer can be eliminated.

  The heat conductivity of air is 0.024 [W / m · K], whereas the heat transfer coefficient of the brazing material 22a made of aluminum alloy is generally 100 [W / m · K] or more. The thermal conductivity of the brazing material 22a is significantly larger than the conductivity. Therefore, according to the present embodiment, the contact thermal resistance between the fin 20 and the heat transfer tube 30 can be remarkably reduced.

  As a result, the plurality of fins 20 can be tightly fixed so as to be perpendicular to the heat transfer tube 30b after the tube expansion, and the collar portion 20b of the fin 20 is a cross fin in which the plurality of fins 20 are arranged at regular intervals. A tube heat exchanger can be obtained.

  Thus, in this embodiment, after passing the heat transfer tube 30a before the tube expansion through the through hole 20a of the fin 20, the heat transfer tube 30a has an outer diameter larger than the diameter of the through hole 20a and a tube expansion rate. Since the pipe is expanded so that it becomes less than 1.5%, that is, the fin 20 and the heat transfer tube 30 are in contact with each other, the expanded heat transfer tube 30b and the fin 20 are then brazed in the furnace and joined. It is possible to improve the performance of the heat exchanger by reducing the contact thermal resistance between the fins and the heat transfer tubes while suppressing the crushing of the peak portions of the fin grooves provided in the heat tubes.

  Further, in this embodiment, at the time of assembly, the heat transfer tube 30 is passed through the fins 20 having the through holes 20a having a diameter larger than the outer diameter of the heat transfer tube 30a before the expansion, so that the heat exchanger is assembled. The effect that the work can be easily performed is obtained.

  The cross fin tube heat exchanger having the above-described configuration is used as an outdoor heat exchanger 7 installed outdoors. The outdoor heat exchanger 7 acts as an evaporator during heating operation, and therefore the temperature of the fin 20 is lower than the outside air temperature. When the temperature of the fin 20 falls below the dew point of the outside air, moisture in the outside air is condensed on the surface of the fin 20 of the outdoor heat exchanger 7. Further, when the surface temperature of the fin 20 is lowered to 0 ° C. or less, the moisture condensed on the surface of the fin 20 is solidified and changed to ice or frost.

  When the operation of the fin 20 is continued for a certain time in a state where the temperature of the fin 20 is 0 ° C. or less, frost is generated on the entire surface of the fin 20 of the outdoor heat exchanger 7, and this frost becomes a thermal resistance. The heat transfer performance is reduced. Further, since the gap between the fins 20 is also narrowed by frost, the flow resistance of the air flowing through the outdoor heat exchanger 7 is increased, and the flow rate of the air flowing through the outdoor heat exchanger 7 is also reduced. The heat transfer performance of the vessel 7 is reduced. For this reason, the evaporation pressure is reduced, and the pressure on the suction side of the compressor 5 is reduced, so that the density on the suction side of the compressor 5 is also reduced. As a result, the amount of refrigerant circulating through the refrigeration cycle apparatus is reduced, so that the heating capacity on the indoor unit 2 side is reduced.

  Therefore, in the refrigeration cycle apparatus, when the heating operation is continued for a certain time in a state where the outside air temperature is low and the temperature of the fin 20 is 0 ° C. or less, frost attached to the fin 20 of the outdoor heat exchanger 7 is removed. For this purpose, a defrosting operation is performed. In this defrosting operation, the operation is performed so that the temperature of the fin 20 is 0 ° C. or higher, and the attached frost is removed.

  For example, if the outside air temperature exceeds 0 ° C., the compressor 5 is stopped, the refrigerant flowing in the outdoor heat exchanger 7 is stopped, the evaporation pressure is increased, and the temperature of the outdoor heat exchanger 7 is 0 ° C. As described above, the frost attached to the fins 20 is melted.

  Moreover, there exists a reverse cycle defrost system as another defrost system. This is because the refrigeration cycle is temporarily switched to the reverse cycle, that is, the cooling operation, whereby the high-pressure and high-temperature refrigerant discharged from the compressor 1 is caused to flow to the outdoor heat exchanger 7 to condense the outdoor heat exchanger 7. The frost attached to the outdoor heat exchanger 7 is melted. This defrosting method is effective even when the outside air temperature is 0 ° C. or lower.

  When the defrosting operation is performed, the frost adhering to the outdoor heat exchanger 3 melts and changes to water, but this water travels down the fins 20 and falls downward due to gravity, and the outdoor heat exchanger 3 is installed. The outdoor unit 1 flows to the bottom base 14 (see FIG. 2) of the outdoor unit 1 and passes through a water receiver (not shown) provided on the bottom base 14 to the outside of the outdoor unit 1 through a drain hole provided on the bottom base 14. Discharged. At this time, if the amount of the water is large, the water is collected in the water receiver provided on the bottom base 14, and the outdoor heat exchanger 7 and the bottom base 14 are electrically connected through the water.

  Since the material of the bottom base 14 is iron and the heat transfer tube 30 used for the outdoor heat exchanger 7 is an aluminum material, the iron and the aluminum heat transfer tube 30 are electrically connected through water. That is, since dissimilar metals having different potentials are connected via water, the aluminum heat transfer tube 30 having a high ionization tendency is dissolved into water, so that the thickness of the aluminum heat transfer tube 30 is reduced. As a result, the aluminum heat transfer tube 30 is thinned, and eventually, the refrigerant flowing through the heat transfer tube 30 is discharged outside the refrigeration cycle apparatus.

  In order to solve this problem, in this embodiment, as described with reference to FIG. 2, the bottom base 14 of the outdoor unit 1 and the aluminum cross fin tube heat exchanger (outdoor heat exchanger 7) pass water. Insulating material 15 is disposed between bottom base 14 and outdoor heat exchanger 7 so as not to connect.

  Further, in order to improve the performance of the outdoor heat exchanger 7 and the indoor heat exchanger 12, a part of the fin 20 is cut and raised in the fin 20 in a direction perpendicular to the air flow to form a large number of slits. There is a case. That is, by arranging the slits so that the thickness of the temperature boundary layer on the surface of the fin 20 with respect to the air flow is minimized at the front edge of each slit, the heat transfer coefficient at the front edge of the slit is increased. The heat exchanger performance is improved.

  However, in the outdoor heat exchanger 7 that acts as an evaporator during the heating operation, the frost attached to the fins 20 is changed to water in the defrosting operation, and the fins 20 are cut and raised in the direction perpendicular to the air flow. When provided, water remains in the slit due to the surface tension of the water. If the defrosting operation is continued for a long time, the water remaining in the slit is evaporated, and the water on the surface of the outdoor heat exchanger 7 is removed.

  However, since sufficient heating operation cannot be performed on the indoor unit 2 side during the defrosting operation, the temperature in the room in which the indoor unit 2 is installed is lowered and comfort is reduced. Therefore, it is desirable to set the defrosting operation as short as possible. If the frost adhering to the surface of the outdoor heat exchanger 7 melts and the water on the surface of the fin 20 except the inside of the slit is discharged downward by gravity, the inside of the slit is removed. Even if water remains, there is a case where the defrosting operation is terminated and switched to the heating operation.

  When the outdoor heat exchanger 7 acts as an evaporator when the water remains in the slit and the outdoor heat exchanger 7 acts as an evaporator, the water remaining in the slit is reduced when the temperature of the fin 20 becomes 0 ° C. or lower. It freezes and the inside of the slit becomes clogged. In the initial stage when switching from the defrosting operation to the heating operation, if the inside of the slit through which air flows is clogged, the amount of air flow flowing to the outdoor heat exchanger 7 is reduced. The amount of heat exchange decreases and the evaporation pressure decreases. For this reason, since the density of the refrigerant | coolant by the side of the suction of the compressor 1 falls and a refrigerant | coolant circulation amount reduces, a heating capability falls.

  Therefore, when the outdoor heat exchanger 7 acts as an evaporator, it is effective that the fins 20 of the outdoor heat exchanger 7 are slitless fins. Here, the slitless fin is a fin that does not have a slit formed by cutting and raising a part of the fin 20 (a slit formed in a direction substantially perpendicular to the direction of air). Note that fins with notches and slits provided parallel to the air flow can be used for outdoor heat exchangers even if water remains in the notches or slits and the inside of the slits becomes clogged during defrosting operation. 7 has almost the same increase in ventilation resistance, and therefore has the same performance as the slitless fin. Such a fin is also included in the category of the slitless fin in this embodiment.

  A second embodiment of the present invention will be described with reference to FIGS. FIG. 8 is a cross-sectional view of the main part for explaining the main part of the cross fin tube type heat exchanger according to the second embodiment, and shows a joined state after brazing the fin and the heat transfer tube. FIG. 9 is a cross fin tube type. It is a figure explaining the state which the water droplet adhered to the fin surface of a heat exchanger.

  FIG. 8 shows a part of a cross fin tube type heat exchanger used in the refrigeration cycle apparatus of the second embodiment, and is a view showing only one part out of a plurality of fins. is there. In FIG. 8, 23 is a fin, and 31 is a heat transfer tube. Like the first embodiment, after passing the heat transfer tube 31 through the through hole 23a of the fin 23, the heat transfer tube 31 is moved from the diameter of the through hole 23a. And the expansion ratio is less than 1.5%, and then, brazing is performed in a furnace to fix the fins 23 and the heat transfer tubes 31 tightly. In addition, 22a is a brazing material and 23b is a fin collar part.

  In a cross fin tube type heat exchanger using conventional copper heat transfer tubes and aluminum fins, a precoat material in which the surface of an aluminum base material is coated is generally used as the fin. The purpose of using the precoat material is to improve corrosion resistance and hydrophilicity.

  However, when an aluminum-based material is used as the heat transfer tube, the aluminum heat transfer tube has a lower potential than copper and thus is easily corroded. When the heat transfer tube is corroded, the refrigerant flowing inside the heat transfer tube is discharged to the outside of the heat transfer tube. Therefore, it is preferable to design the fin 20 to corrode first and to delay the corrosion of the heat transfer tube 31. If the precoat material is used as a fin as in the prior art, corrosion resistance is improved and corrosion is difficult, so that the corrosion progress of the aluminum heat transfer tube is accelerated.

  Therefore, in the second embodiment, the fin 23 is not a precoat material but a precoatless fin. Further, since the material having a lower potential corrodes first, the potential of the fin 23 and the heat transfer tube 31 is made of a material such that the fin 23 is lower than the heat transfer tube 31.

  Further, in the second embodiment, in order to improve the corrosion resistance of the heat transfer tube 31 on the air side, an aluminum heat transfer tube (clad tube) in which a zinc sacrificial layer 31b is sprayed on the outer surface of the aluminum heat transfer tube portion 31a. 31 is used. The zinc sacrificial layer (zinc rich layer) 31b has a lower potential than the aluminum heat transfer tube portion (aluminum rich layer) 31a, which is the base material, so that the zinc sacrificial layer 31b is selectively corroded. Thus, the corrosion of the aluminum heat transfer tube 31a, which is the base material, can be delayed.

  However, in this Example 2, since the precoatless fin which has not been precoated is used, the hydrophilicity of the fin 23 surface is inferior to that of the precoated fin. If the hydrophilicity is inferior, as shown in FIG. 9A, when a water droplet (condensed water) 18 is condensed on the surface of the fin 23, the contact angle θc of the water droplet 18 is increased. For this reason, the big water droplet 18 stays between the several fin 23, the drainage property of the fin 23 worsens, the said water droplet 18 becomes resistance of an air flow, and there exists a subject that ventilation resistance becomes large.

  However, in the present embodiment, the fin 23 uses a fin provided with a brazing filler metal layer on the fin core as in the first embodiment, and the heat transfer tube portion 31a made of aluminum is inserted into the through hole of the fin 23. The heat transfer tube 31 is expanded through the heat transfer tube 31 sprayed with a sacrificial zinc layer 31b on the surface, the fin and the heat transfer tube 31 are joined, and then brazed in a furnace, so that the fin 23 and the heat transfer tube 31 are in close contact with each other. Since it is fixed, the following effects can be obtained.

  That is, since the heat exchanger manufactured in the second embodiment is manufactured by brazing in a furnace in a heating furnace, the surface state of the fins 23 is as shown in FIG. 9B. That is, by heating the fin 23, the brazing material layer on the surface of the fin 23 is melted, but a part of the brazing material layer remains on the surface of the fin 23. 22 b is a brazing material (residual brazing material) remaining on the surface of the fin 23. Although the residual brazing filler metal 22 b is shown only on a part of the fin 23 in FIG. 9B, it is scattered over the entire surface of the fin 23. And the surface of the fin 23 which has this residual brazing material 22b is a rough surface.

The contact angle θc of the water droplet 18 on the rough surface with respect to the contact angle θ of the water droplet 18 on the flat surface can be obtained from the following Wenzel equation.
cos θc = r · cos θ
Here, θc is the contact angle on the rough surface, r is the area ratio of the rough surface to the plane (r ≧ 1), and θ is the contact angle on the flat surface.

  The contact angle θ on the flat aluminum surface is about 80 °. From the above equation, if θ <90 ° and r> 1, then θc <θ. Therefore, the rougher the surface, the smaller the contact angle θc, the wettability of the fin 23 surface can be improved, and the hydrophilicity is improved. To do. According to the present embodiment, due to the effect of the residual brazing material 22b scattered on the surface of the fin 23, the contact angle θc of the water droplet 18 on the surface of the fin 23 can be set to a contact angle of 10 ° to 20 ° or less of the precoat material. Thus, since the hydrophilicity of the fins 23 can be improved, a heat exchanger having a small ventilation resistance of the fin 23 pipe can be obtained.

  Next, a modification of the above-described second embodiment will be described. In the above-described second embodiment, the example in which the aluminum heat transfer tube (clad tube) 31 in which the zinc sacrificial layer 31b is sprayed on the surface of the aluminum heat transfer tube portion 31a has been described. On the other hand, this modified example is the same in that a clad tube is adopted as the heat transfer tube 31, but the heat transfer tube 31 of this modified example is a heat transfer tube portion (inside the heat transfer tube 31 in which the refrigerant flows) 31a) is made of a copper-based material, and the outer member (31b) of the heat transfer tube 31 is configured as a clad tube made of an aluminum-based material. This heat transfer tube is effective in the following cases.

  As shown in FIG. 1, the copper connection pipes 3 and 4 are used in the refrigeration cycle apparatus. However, the copper pieces generated when the copper connection pipes 3 and 4 are processed and the connection pipes 3 and 4 are used. Foreign matter such as oxide scale (copper oxide) generated when 4 is connected by brazing may be mixed in the refrigeration cycle apparatus. The copper pieces and oxide scale mixed in the refrigeration cycle circulate in the refrigeration cycle together with the refrigerant circulating in the refrigeration cycle, and flow into the heat transfer tube 30 of the outdoor heat exchanger 7. Since the fin groove is formed in the heat transfer tube 30, foreign matter that has flowed into the heat transfer tube 30 may remain in the fin groove. Since electricity flows in the liquid phase state of the refrigerant flowing inside the heat transfer tube 30, when the aluminum heat transfer tube 30 is adopted, it contacts copper, which is a foreign substance, through the liquid phase state of the refrigerant. Since aluminum and copper have a higher ionization tendency, aluminum heat transfer tubes corrode, holes are formed in the heat transfer tubes, and the refrigerant sealed in the refrigeration cycle device can be discharged outside the refrigerant cycle device. There is sex.

  Further, when the refrigerating cycle apparatus is renewed, the existing outdoor unit 1 and the indoor unit 2 are changed using the existing piping used in the old unit. In this case, if the refrigerant used in the old machine is, for example, a refrigerant containing chlorine such as R22, the chlorine in the refrigerant has an extreme pressure action, so that this chlorine is generated at the sliding portion of the compressor 5. Combines with certain bearings and iron to produce iron chloride. Due to deterioration over time, the iron chloride generated at the sliding portion of the compressor 1 may become worn and remain in the existing connection pipes 3 and 4. For this reason, when the renewal is performed, the chlorine-based compound is mixed into the refrigeration cycle apparatus and flows into the heat transfer tube 30 of the outdoor heat exchanger 7. Copper is strong against chlorinated compounds, but aluminum is weak, so when aluminum heat transfer tubes are used, the aluminum heat transfer tubes react with the chlorinated compounds and corrode, and there are holes in the heat transfer tubes as in the above example. May open.

  In such a case, by adopting a clad tube with copper (copper-based material) on the inner side (refrigerant side) and aluminum (aluminum-based material) on the outer side (air side) of the modified example described above as the heat transfer tube, The effect which can prevent corrosion of a heat exchanger tube is acquired.

  According to each embodiment of the present invention described above, the fins and heat transfer tubes of the outdoor heat exchanger shown in FIG. 1 and FIG. 2 are made of an aluminum-based material, so a copper material is adopted as the heat transfer tube. It is particularly effective for a refrigeration cycle apparatus that can be reduced in weight as compared with the case and has a large outdoor heat exchanger. For example, it is a horizontal blow type outdoor unit that blows air that is passed through the outdoor heat exchanger shown in FIG. 1 in parallel (horizontal direction) to the ground, and there are two fans (ventilators) in the vertical direction. This is effective for large outdoor units that have multiple units. Further, in a refrigeration cycle apparatus that generates a large amount of heat in the indoor unit and requires a large amount of heat exchange in the outdoor heat exchanger, the heat transfer area of the outdoor heat exchanger is increased and the outdoor heat exchange is performed. It is necessary to increase the air volume of the air flowing through the unit, so a large-capacity blower (ventilation device) is installed at the top of the outdoor unit housing, and the top-blowing type outdoor unit that blows air upward (such as the indoor unit) It is also suitable for an outdoor unit of a multi-air conditioner for buildings having a large number.

  Further, in this embodiment, the through hole of the fin is formed to have a larger diameter than the outer diameter of the heat transfer tube, and after passing the heat transfer tube through the through hole, the outer diameter of the heat transfer tube is equal to the through hole. Since the heat transfer tube is expanded and joined so that the tube expansion ratio is less than 1.5% larger than the diameter, and this joined portion is brazed in the furnace, the fin and the heat transfer tube are It can be set to the minimum expansion ratio. As a result, it is possible to minimize the crushing of the ridges of the fin groove inside the heat transfer tube due to the expansion, and to make the contact thermal resistance extremely small, so that the performance of the heat exchanger can be greatly improved. Moreover, since the heat transfer tube is expanded after passing the heat transfer tube through the fin, the cross-sectional area of the through hole (heat transfer tube passage portion) provided in the fin can be set larger than the cross-sectional area of the heat transfer tube. Accordingly, since a plurality of fins can be easily passed through the heat transfer tube, a refrigeration cycle apparatus equipped with a highly manufacturable and high-performance heat exchanger that can easily perform heat exchanger assembly work is provided. Can be obtained.

In addition, this invention is not limited to the Example mentioned above, Various modifications are included. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment.
Further, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described.

DESCRIPTION OF SYMBOLS 1 ... Outdoor unit, 2 ... Indoor unit, 3 ... Liquid side connection piping, 4 ... Gas side connection piping,
5 ... Compressor, 6 ... Four-way valve, 7 ... Heat source machine side heat exchanger, 8 ... First expansion device,
9 ... Accumulator, 10 ... Liquid blocking valve, 11 ... Gas blocking valve,
12 ... user-side heat exchanger, 13 ... second expansion device,
14 ... bottom base, 15 ... insulating material,
16 ... space (air layer), 17 ... gap, 18 ... water droplets (condensed water),
20, 23 ... fins, 20a, 23a ... through holes, 20b, 23b ... collar portions,
21 ... Fin core material, 22 ... Brazing material layer, 22a ... Brazing material, 22b ... Residual brazing material,
30 ... Heat transfer tube, 30a ... Heat transfer tube before expansion, 30b ... Heat transfer tube after expansion,
31 ... Heat transfer tube (clad tube),
31a ... Heat transfer tube portion (aluminum rich layer), 31b ... Sacrificial layer (zinc rich layer).

Claims (10)

In a refrigeration cycle apparatus configured by sequentially connecting a compressor, a heat source side heat exchanger, an expansion device, and a use side heat exchanger with refrigerant piping,
The heat source side heat exchanger includes a heat transfer tube made of an aluminum-based material and having fin grooves formed on the inner surface thereof, and a fin formed of an aluminum-based material and formed with a through hole for passing the heat transfer tube. The fin through hole is formed with a diameter larger than the outer diameter of the heat transfer tube, and after passing the heat transfer tube through the through hole, the heat transfer tube The heat transfer tube is expanded and joined so that the outer diameter is larger than the diameter of the through-hole and the expansion rate is less than 1.5%, and the joined portion is brazed. A refrigeration cycle device. The refrigeration cycle apparatus according to claim 1,
The refrigeration cycle, wherein the heat transfer tube and the fin are made of different aluminum materials so that the potential of the fin is lower than the potential of the heat transfer tube in the heat source side heat exchanger. apparatus. The refrigeration cycle apparatus according to claim 1,
The heat source side heat exchanger is installed on a bottom base in a casing of an outdoor unit, and an insulating material is disposed between the outdoor heat exchanger and the bottom base. Refrigeration cycle equipment. In the refrigeration cycle apparatus according to any one of claims 1 to 3,
The refrigeration cycle apparatus, wherein the fin of the heat source side heat exchanger is a slitless fin in which no slit is formed. In the refrigeration cycle apparatus according to any one of claims 1 to 3,
The fin of the heat source side heat exchanger is composed of a precoat-less fin that is not precoated on the surface thereof. In the refrigeration cycle apparatus according to any one of claims 1 to 3,
The refrigeration cycle apparatus, wherein the heat transfer tube of the heat source side heat exchanger is configured by a clad tube in which a sacrificial layer of zinc is sprayed on an outer surface of an aluminum heat transfer tube portion. In the refrigeration cycle apparatus according to any one of claims 1 to 3,
The refrigeration cycle apparatus characterized in that the heat transfer tube of the heat source side heat exchanger is constituted by a clad tube made of a copper-based material on the refrigerant side and an aluminum-based material on the air side. In the refrigerating cycle device according to any one of claims 1 to 3,
The heat source side heat exchanger is installed in an outdoor unit, and the outdoor unit includes a plurality of ventilation devices for passing the heat source side heat exchanger in the vertical direction of the heat source side heat exchanger. A refrigeration cycle apparatus characterized in that air is blown out horizontally. In the refrigerating cycle device according to any one of claims 1 to 3,
The heat source side heat exchanger is installed in an outdoor unit, and the outdoor unit is provided with a ventilating device for ventilating the heat source side heat exchanger, and the ventilating device blows air upward. Refrigeration cycle equipment. In the manufacturing method of the cross fin tube type heat exchanger used in the refrigeration cycle apparatus,
Preparing a heat transfer tube made of an aluminum-based material and having fin grooves formed on the inner surface, and a fin made of an aluminum-based material and having a through-hole having a diameter larger than the outer diameter of the heat transfer tube;
After passing the heat transfer tube through the through hole of the fin, the heat transfer tube is expanded so that the outer diameter is larger than the diameter of the through hole and the expansion rate is less than 1.5%.
Then, the said fin and a heat exchanger tube are brazed and joined. The manufacturing method of the cross fin tube type heat exchanger used for the refrigerating cycle apparatus characterized by the above-mentioned.

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