JP7803702B2 - heat exchanger - Google Patents

Description

An embodiment of the present invention relates to a fin-tube heat exchanger that uses flat tubes.

Conventionally, fin-tube heat exchangers have been known in which multiple notches are provided in the fins and flat tubes extending in the direction of the fins are inserted into the notches.

When an air conditioner using this heat exchanger is operating in heating mode, water vapor contained in the outside air becomes drainage and adheres to the heat exchanger. When the drainage is cooled by the outside air, it turns into frost, which can cause frost to form on the heat exchanger.
Therefore, after a certain period of time has elapsed since the heating operation, the defrosting operation is performed.

WO-A1-2019/175973

When defrosting is performed, the frost that has formed on the heat exchanger melts and becomes drainage, which is then discharged. However, drainage may not be properly drained during defrosting because the drainage may stagnate at the top of the flat tubes.
Furthermore, if heating operation is resumed without draining the drain, there is a risk that the drain stagnating at the top of the flat pipes will refreeze.

The problem that this invention aims to solve is to provide a heat exchanger that prevents drainage generated during defrosting operation from stagnating at the top of the flat tubes, thereby improving the heat exchange rate.

In order to solve the above problems, the heat exchanger of the present invention comprises plate-shaped fins having a plurality of notches formed at regular intervals in the longitudinal direction, which is the direction of gravity on the downwind side, a plurality of flat tubes attached to the plurality of notches, a communicating protrusion protruding in the longitudinal direction on the upwind side of the plate-shaped fin, and a plurality of protrusions that are arranged below the uppermost flat tube among the plurality of flat tubes and protrude from the flat portion of the plate-shaped fin on the downwind side of the communicating protrusion.
This protrusion has an upper end portion that is located downwind of the windward end portion of the flat tube and above the height of the upper surface of the flat tube, and a lower end portion that is located upwind of the windward end portion of the flat tube and below the height of the lower surface of the flat tube , and is close to the connecting protrusion.
Furthermore, the upper end of the protrusion is located above the upper end of other protrusions that are located below this protrusion in the direction of gravity, and the lower end of the protrusion is located below the upper end of the other protrusions.

1 is a schematic diagram of a refrigeration cycle of an air conditioner according to a first embodiment. FIG. 2 is a plan view of an outdoor heat exchanger according to the air conditioner of the first embodiment. FIG. 2 is a plan view of a plate-shaped fin according to the outdoor heat exchanger of the first embodiment. FIG. 3 is a cross-sectional view of the plate fin taken along line A-A' according to the first embodiment. FIG. 4 is a plan view of a plate-shaped fin according to a first modified example of the first embodiment. FIG. 10 is a plan view of a plate-shaped fin according to a second modified example of the first embodiment. FIG. 10 is a plan view of a plate-shaped fin according to a second embodiment of the outdoor heat exchanger. Cross-sectional view 1 of a plate-shaped fin taken along line t-t' according to the second embodiment. Cross-sectional view 1 of a plate fin according to a second embodiment taken along line x-x'. Cross-sectional view 2 of a plate-shaped fin taken along line t-t' according to the second embodiment. Cross-sectional view 2 of a plate fin taken along line x-x' according to the second embodiment. FIG. 10 is a plan view of a plate-shaped fin according to a first modified example of the second embodiment. FIG. 10 is a plan view of a plate-shaped fin according to a second modified example of the second embodiment. FIG. 10 is a plan view of a plate-shaped fin according to a third modified example of the second embodiment. FIG. 10 is a plan view of a plate-shaped fin according to a third embodiment.

The following describes an embodiment of the invention.

(First embodiment)
A heat exchanger according to a first embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic diagram of a refrigeration cycle of an air conditioner 1 according to the first embodiment.

(Air conditioner)
The air conditioner 1 of this embodiment is composed of a compressor 2, a four-way valve 3, an outdoor heat exchanger 4, an outdoor fan 4', an expansion valve 5, an indoor heat exchanger 6, an indoor fan 6', and refrigerant piping 7 connecting these elements, forming a refrigeration cycle 10.
The compressor 2 includes a compressor main body 2 a and an accumulator 2 b. The accumulator 2 b separates the refrigerant into gas and liquid and sends the gas refrigerant to the compressor main body 2 a. The compressor main body 2 a compresses the gas refrigerant supplied from the accumulator 2 b to generate high-temperature, high-pressure gas refrigerant.
In addition, by switching the flow path of the four-way valve 3, the refrigeration cycle 10 is switched between cooling operation, heating operation, etc.

(Cooling operation)
The flow of refrigerant during cooling operation, as indicated by the solid arrows in FIG. 1, will now be described.
The gas refrigerant discharged by the compressor 2 passes through the flow path depicted by the solid line in the four-way valve 3 via the refrigerant piping 7. It then flows into the outdoor heat exchanger 4, where it is condensed as it releases heat to the outside air due to the airflow from the outdoor fan 4'. The condensed liquid refrigerant passes through the refrigerant piping 7 and the expansion valve 5. At this time, the pressure of the refrigerant is reduced. The low-pressure liquid refrigerant evaporates by removing heat from the indoor air via the indoor heat exchanger 6 and the indoor fan 6', thereby performing heat exchange. This evaporated gas refrigerant flows back into the compressor 2.

(Heating operation)
On the other hand, during heating operation, as shown by the dashed arrow in FIG. 1 , the gas refrigerant discharged by the compressor 2 passes through the four-way valve 3 in the dashed line direction and flows into the indoor heat exchanger 6. The indoor heat exchanger 6 and the indoor fan 6' exchange heat with the indoor air, condensing the gas refrigerant by releasing heat to the indoor air and changing into liquid refrigerant. This condensed refrigerant passes through the expansion valve 5 via the refrigerant piping 7. At this time, the pressure of the refrigerant is reduced, and the refrigerant becomes low-pressure liquid refrigerant. This low-pressure liquid refrigerant flows into the outdoor heat exchanger 4, where it absorbs heat from the outdoor air by the airflow of the outdoor fan 4' and changes into gas refrigerant. This evaporated gas refrigerant flows back into the compressor 2.
In this way, the refrigeration cycle 10 is formed, and cooling and heating operations are performed.

(Defrosting operation)
When the air conditioner 1 performs heating operation, the refrigerant evaporates in the outdoor heat exchanger 4 .
At that time, the refrigerant absorbs heat from the outside air and condenses it, causing the water vapor contained in the outside air to turn into water and adhere to the outdoor heat exchanger 4. Furthermore, due to the low temperature of the outside air, the water adhering to the outdoor heat exchanger 4 may freeze and turn into frost, reducing the heat exchange efficiency.
In order to remove this frost, a defrosting operation is performed.

For example, as a method of switching from heating operation to defrosting operation, the amount of frost formed on the outdoor heat exchanger 4 is measured based on the temperature of the outdoor heat exchanger 4, and when the amount of frost formed reaches or exceeds a specified value, the operation is switched from heating operation to defrosting operation.
The defrosting operation is continued until the amount of frost decreases below a specified value or until a specified time has elapsed.
In defrosting operation, the four-way valve 3 is switched from heating operation to cooling operation and the indoor fan 6' and outdoor fan 4' are stopped. This allows high-temperature gas discharged from the compressor 2 to flow into the outdoor heat exchanger 4, melting the frost that has formed on the outdoor heat exchanger 4 and being discharged as drain.

(Outdoor heat exchanger)
FIG. 2 is a plan view of the outdoor heat exchanger 4 of the air conditioner 1 according to the first embodiment.
The outdoor heat exchanger 4 is a fin-tube type heat exchanger, and is mainly made of aluminum.
In Figure 2, the airflow direction to the outdoor heat exchanger 4 is perpendicular to the plane of the page and is indicated by a white arrow. Here, the lower side of the arrow is the front side of the page and the upper side of the arrow is the back side of the page, indicating that the air flows from the front side to the back side of the page. In addition, the refrigerant flow direction perpendicular to the airflow direction is indicated by a solid arrow.
The outdoor heat exchanger 4 has a plurality of plate-shaped fins 41 stacked in the direction of refrigerant flow, a plurality of flat tubes 42 attached to the plate-shaped fins 41 in the direction of gravity, and two headers 43, 44 provided at both ends of the flat tubes 42.

(flat tube)
FIG. 3 is a plan view of the plate-shaped fins 41 of the outdoor heat exchanger 4 of the first embodiment.
The flat tube 42 has a cross section that is generally oval or elliptical, and has, for example, an oval cross section as shown in Fig. 3. The flat tube 42 is a heat transfer tube in which a plurality of fluid passages 45 are provided so as to extend parallel to one another.
The flat tubes 42 are also treated to be water-repellent, for example by applying a water-repellent coating material thereto.

(header)
2, the headers 43, 44 are each an elongated hollow cylinder into which the flat tubes 42 are inserted at one end, and the upper and lower ends are closed by end caps 43a, 43b, and 44a, 44b. The headers 43, 44 are also provided with a plurality of partition plates (not shown) inside to control the flow of the refrigerant.
One end of a liquid side joint pipe 43c is connected to the header 43. The other end of the liquid side joint pipe 43c is connected to the refrigerant pipe 7 and to the expansion valve 5.
Similarly, one end of a gas side joint pipe 44c is connected to the header 44. The other end of this gas side joint pipe 44c is connected to the refrigerant pipe 7 which is connected to the four-way valve 3.
In this way, during cooling operation, the refrigerant flows through the four-way valve 3, the refrigerant pipe 7, the gas-side joint pipe 44c, the header 44, and the flat tubes 42 in the outdoor heat exchanger 4. The refrigerant then exchanges heat with the plate-like fins 41, passes through the header 43, and flows into the expansion valve 5 via the liquid-side joint pipe 43c and the refrigerant pipe 7.

(fin)
As shown in Figure 3, the plate-shaped fin 41 is formed in an approximately rectangular shape, with the longitudinal side on the downwind side in the direction of gravity being the long side 41a, the upwind side opposite the long side 41a being the long side 41c, the short side above the direction of gravity being the short side 41b, and the lower side opposite the short side 41b being the short side 41d.
The plate-like fins 41 are hydrophilically treated, for example, by applying a hydrophilic coating material.

The direction of wind flow is indicated by a solid arrow.
A plurality of notches 41e are formed at regular intervals on the long side 41a on the downwind side of the plate-like fin 41, and the notches 41e extend in the short direction. The upwind end 41e' of each notch 41e has a substantially semicircular or elliptical shape to match the shape of the end of the flat tube 42, and the flat tube 42 is inserted into the notch 41e.

(Communication part)
FIG. 4 is a cross-sectional view of the plate-shaped fin 41 taken along line AA' as viewed from the direction of the solid arrow.
4, a communicating protrusion 46 is formed on the upwind long side 41c of the plate-shaped fin 41, parallel to the long side 41c. The communicating protrusion 46 is spaced a certain distance from the long side 41c and is provided continuously from the upper end to the lower end of the plate-shaped fin 41 so as to be convex on the surface of the plate-shaped fin 41.

(protrusion)
The plate-like fin 41 is provided with protrusions 400 (400A, ..., ..., 400N).
The cross section of the protrusion 400 is formed to have a semicircular shape, as shown in Fig. 4. The cross section of the protrusion 400 is not limited to a semicircular shape, and may be formed to have a sharp protrusion or a substantially rectangular shape.

The protrusions 400 (400A, ..., ..., 400N) are provided corresponding to the flat tubes 42 (42A, ..., ..., 42N).
More specifically, as shown in FIG. 3, the flat tubes 42 are arranged in the order of flat tube 42A to flat tube 42N at predetermined intervals.
Correspondingly, the protrusions 400 are also formed from protrusion 400A to protrusion 400N.

The upper end 400Aa of the protrusion 400A is located lower than the height of the lower surface 42Ab of the flat tube 42A, and is located downwind of the upwind end 42Bu of the flat tube 42B and higher than the height of the upper surface 42Bt of the flat tube 42B.
Meanwhile, the lower end 400Ab is located higher than the height of the upper surface 42Ct of the flat tube 42C. Furthermore, the lower end 400Ab is located on the windward side of the windward end 42Bu of the flat tube 42B and lower than the height of the lower surface 42Bb of the flat tube 42B.
That is, the protruding portion 400A is formed so as to necessarily have the height of the upper surface 42Bt and the lower surface 42Bb of the flat tube 42B.

Similarly, the upper end 400Ba of the protrusion 400B is located lower than the lower surface 42Bb of the flat tube 42B, and is located downwind of the windward end 42Bu of the flat tube 42B and higher than the upper surface 42Ct of the flat tube 42C. Furthermore, the lower end 400Bb is located upwind of the windward end 42Cu of the flat tube 42C and lower than the lower surface 42Cb of the flat tube 42C.

The positional relationship between protrusion 400A and protrusion 400B is such that the upper end 400Ba of protrusion 400B and the lower end 400Ab of protrusion 400A are aligned in the wind direction at a position lower than the lower surface 42Bb of flat tube 42B, with an overlap of a height a'.
Furthermore, the lower end portion 400Ab is provided at a position close to the communicating protrusion 46.
In this way, the protrusions 400 are arranged in a row from protrusion 400A to protrusion 400N, each having a predetermined height from the other protrusions 400.

With this structure, the drainage water dropping from the flat tubes 42 is discharged into the drainage flow path formed by the protrusion 400 without stagnating on the upper surfaces 42t of the other flat tubes 42.
Furthermore, since the lower end 400b of the protrusion 400 is arranged to approach the communicating protrusion 46, after flowing through the drainage flow path formed by the protrusion 400, it is more likely to be drained into the communicating protrusion 46 due to capillary action.
Furthermore, since the lower ends 400b of the multiple protrusions 400 are formed to converge at the communicating protrusion 46, the drain from one plate-shaped fin 41 is concentrated at the communicating protrusion 46, thereby improving the drainage speed.

(First Modification)
FIG. 5 is a plan view of a plate-shaped fin 41 according to a first modified example of the first embodiment.
In the first embodiment, as shown in FIG. 5, the linear protrusions 400 are provided at an incline, are parallel to each other, and are arranged so that the lengths of the plurality of protrusions 400 are the same. However, in this modification, as shown in FIG. 5, the lengths and inclinations of the plurality of protrusions 400 to 400″ are different from each other.
As long as the protrusions 400 to 400 ″ are inclined from the flat tube 42 toward the communicating protrusion 46 , they do not have to be equal in length to the other protrusions 400 or parallel to the other protrusions 400 .

(Second Modification)
FIG. 6 is a plan view of a plate-shaped fin 41 according to a second modified example of the first embodiment.
As shown in the protrusion 420 of FIG. 6, a lower end 420b of the protrusion 420 may be provided with a parallel portion 420p that is parallel to the communicating protrusion 46.
Furthermore, as shown in the protrusion 430, parallel portions 430p may be provided at both ends of the upper end 430a and the lower end 430b of the protrusion 430.

In this way, the parallel portion has a linear shape, which can improve the drainage speed.
Furthermore, the parallel portions do not have to be the same length as other parallel portions.
Furthermore, as shown in FIG. 6, the protrusion 400 may be formed by combining protrusions that do not have the same shape, such as protrusion 420, protrusion 430, and protrusion 400C.

Second Embodiment
7, 8(a), 8(b), 9(a), and 9(b) are plan and cross-sectional views showing a plate-like fin 41 according to a second embodiment of the present invention.
FIG. 7 is a plan view of the plate-shaped fins 41 of the outdoor heat exchanger 4 of the second embodiment.
Figure 8(a) is a cross-sectional view 1 of the plate-shaped fin 41 of Figure 7 taken along line t-t' as viewed from the direction of the solid arrow, and Figure 8(b) is a cross-sectional view 1 of the plate-shaped fin 41 of Figure 7 taken along line xx' as viewed from the direction of the solid arrow.
Similarly, Figure 9(a) is a cross-sectional view 2 of the plate-shaped fin 41 of Figure 7 taken along line t-t' as viewed from the direction of the solid arrow, and Figure 9(b) is a cross-sectional view 2 of the plate-shaped fin 41 of Figure 7 taken along line xx' as viewed from the direction of the solid arrow.

As shown in FIG. 7, in this embodiment, the protrusion 400A has a shape in which two ribs 401A and 402A are continuously arranged in the air flow direction.
Therefore, compared to the protrusion 400A of the first embodiment, drainage is more likely to flow into the gap formed between the ribs 401A and 402A by capillary action, as shown in FIG. 8A.
Furthermore, since the drainage flow paths are formed by the gaps between the ribs, the drain is more easily guided than in the first embodiment, and the drainage speed is further improved.
8(a) and 8(b), the protrusions 400 are configured to approach the communicating protrusions 46, so that after flowing between the ribs, the drain is drained along the communicating protrusions 46. By configuring the drain adhering to the plate-like fins 41 to be collected at the communicating protrusions 46, the drainage efficiency of the drain is further improved.

The cross-sectional shape of these two ribs 401 and 402 may be a shape in which two semicircular ribs are arranged side by side as shown in Figures 8(a) and 8(b), or a shape in which two ribs with sharp protrusions are arranged side by side as shown in Figures 9(a) and 9(b).
Furthermore, the protrusion 400 is not limited to two ribs, but may be a plurality of ribs arranged in succession.
Furthermore, the first and second modifications of the first example may be combined with the second embodiment.

(First Modification)
FIG. 10 is a plan view showing a plate-shaped fin 41 according to a first modified example of the second embodiment.
As shown in Figure 10, in this embodiment, the protrusion 400A is formed from two ribs 401A and 402A, and is formed so that the upper end 401Aa of the rib 401A on the leeward side is positioned higher than the upper end 402Aa of the rib 402A on the windward side.
This shape allows the drain to more easily flow into the gap formed between the two ribs 401A and 402A by capillary action.

(Second Modification)
FIG. 11 is a plan view showing a plate-shaped fin 41 according to a second modification of the second embodiment.
As shown in FIG. 11, the lower end 402Ab of the windward rib 402A may be formed so as to be located lower than the lower end 401Ab of the leeward rib 401A.
By using this shape, the drain that flows into the gaps between the ribs passes through the gaps between the ribs and is guided to the lower end 402Ab of the rib 402A, making it easier to guide it to the communicating protrusion 46 and making it easier for water to drain from the lower end 400Ab of the protrusion 400A.

(Third Modification)
Furthermore, FIG. 12 is a plan view showing a plate-shaped fin 41 according to a third modified example of the second embodiment.
As shown in Figure 12, the protrusion 410 (410A, ..., 410N) is composed of multiple ribs (403-405). Adjacent ribs of this protrusion 410 are formed so that the upper end of the rib on the downwind side is higher than the upper end of the rib on the upwind side. In other words, the upper end 404Aa of rib 404 is higher than the upper end 405Aa of rib 405, and the upper end 403Aa of rib 403 is higher than the upper end 404Aa of rib 404.
Similarly, the lower ends of the multiple ribs may be formed so that the lower end of the leeward rib is positioned higher than the lower end of the windward rib of the adjacent rib. That is, the lower end 404Ab of the rib 404 is positioned higher than the lower end 405Ab of the rib 405, and the lower end 403Ab of the rib 403 is positioned higher than the lower end 404Ab of the rib 404.

By using this shape, even when there are multiple ribs, the difference in height between adjacent ends makes it easier for capillary action to occur, making it easier for drain to flow into the protrusion 410.
Furthermore, by providing a plurality of ribs, a plurality of gaps are formed between the ribs, and the drainage of drainage adhering to the flat tubes 42 can be dispersed into a plurality of gaps.
Furthermore, the difference in height between the ribs makes it easier for the fluid to be guided to the communicating protrusion 46 .

(Third embodiment)
FIG. 13 is a plan view showing a plate-shaped fin 41 according to a third embodiment of the present invention.
As shown in Figure 13, in embodiment 3, the flat tubes 42 are structured so that the upwind end 42u is inclined lower than the downwind end 42l in the direction of gravity, that is, the flat tubes 42 are formed so that they are inclined downward to the right in the direction of gravity of the plate-shaped fins 41.
This shape prevents stagnation of drainage on the upper or lower surface of the flat tube 42, and further promotes drainage of drainage from the flat tube 42 to the protrusion 400 or the communicating protrusion 46.
Moreover, the structures described in the first and second embodiments may be combined with the third embodiment.

Although the embodiments of the present invention have been described above, these embodiments have been presented as examples and are not intended to limit the scope of the invention.
In this embodiment, an example in which the heat exchanger is used as an outdoor heat exchanger is shown, but the heat exchanger can be used as various heat exchangers such as an indoor heat exchanger.
This novel embodiment can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention.
The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.

Plate-shaped fin 41, notch 41e, flat tube 42, windward end 42u, upper surface 42t, lower surface 42b, connecting protrusion 46, protrusion 400, upper end 400a, lower end 400b

Claims (6)

a plate-like fin on the leeward side, in which a plurality of notches are formed at regular intervals in the longitudinal direction, which is the direction of gravity;
a plurality of flat tubes attached to the plurality of cutout portions ;
a communicating protrusion provided in the longitudinal direction of the upwind side of the plate-like fin;
A plurality of protrusions are provided below the uppermost flat tube among the plurality of flat tubes, and protrude from the flat surface of the fin on the downwind side of the communicating protrusion,
The protrusion is
An upper end portion of a protrusion located downwind of the windward end portion of the flat tube and above the height of the upper surface of the flat tube;
a lower end portion of a protrusion located upwind of the windward end portion of the flat tube and below the height of the lower surface of the flat tube, the protrusion being close to the communicating protrusion;
an upper end portion of the protruding portion is located higher than an upper end portion of another protruding portion that is provided below the protruding portion in the direction of gravity;
A heat exchanger, wherein a lower end of the protrusion is located lower than an upper end of the other protrusion. The heat exchanger of claim 1, wherein the protrusion has a parallel portion at at least one end thereof that is parallel to the communicating protrusion. A heat exchanger as described in claim 1 or 2, wherein the protrusion is composed of multiple ribs arranged continuously in the direction of air flow. A heat exchanger as described in claim 3, wherein the ribs provided at the windward ends of the plurality of ribs are formed so that their upper ends are positioned higher than the ribs provided at the leeward ends. A heat exchanger as described in claim 3 or 4, wherein the ribs provided at the windward ends of the plurality of ribs are formed so that their lower ends are positioned lower than the ribs provided at the leeward ends. The heat exchanger according to claim 1 , wherein the flat tubes have windward ends positioned lower than leeward ends with respect to the direction of gravity.