CN110998215B

CN110998215B - Heat exchanger

Info

Publication number: CN110998215B
Application number: CN201880050493.6A
Authority: CN
Inventors: 立野井秀哲; 波良芳裕; 青木泰高; 左海将之
Original assignee: Mitsubishi Heavy Industries Thermal Systems Ltd
Current assignee: Mitsubishi Heavy Industries Thermal Systems Ltd
Priority date: 2017-08-02
Filing date: 2018-06-14
Publication date: 2021-09-14
Anticipated expiration: 2038-06-14
Also published as: WO2019026436A1; EP3647711A4; EP3647711B1; ES2955923T3; JP6946105B2; EP3647711A1; EP3647711C0; CN110998215A; JP2019027727A

Abstract

When there is unevenness of frost formation from the front row or unevenness of refrigerant distribution from the header to the flat tubes, heat transfer loss is suppressed and evaporation performance is ensured. A heat exchanger (1) is provided with a plurality of flat tubes (11), fins (12) provided on the flat tubes (11), and headers (13) (or (23)) that stand in the vertical direction (D1) in which the flat tubes (11) are stacked and are connected to the flat tubes (11), and functions as an evaporator that exchanges heat between the refrigerant flowing into the flat tubes (11) through the headers and air to evaporate the refrigerant. A front row of heat exchange units (10) composed of flat tubes (11), fins (12), and headers (13), and a rear row of heat exchange units (20) composed of flat tubes (11), fins (12), and headers (23) are arranged. The flow path cross-sectional area in the header 13 in the front row is smaller than the flow path cross-sectional area in the header 23 in the rear row so that the flow speed of the refrigerant flowing through the header 13 in the front row F is larger than the flow speed of the refrigerant flowing through the header 23 in the rear row R.

Description

Heat exchanger

Technical Field

The present invention relates to a heat exchanger used in, for example, an air conditioner, a refrigerator, a transport refrigerator, a water heater, and the like.

Background

Heat exchangers in which a refrigerant flows through each of a plurality of stacked flat tubes are used in equipment such as air conditioners and refrigerators, and constitute refrigerant circuits of the equipment.

The plurality of flat tubes are assembled with plate-shaped or corrugated fins and a pair of headers to constitute a heat exchanger. Each flat tube is connected at both ends to a pair of headers, and the refrigerant introduced from the pipe of the refrigerant circuit into the header is distributed to each flat tube. The refrigerant flowing through each flat tube exchanges heat with air flowing into the gaps between the fins and the flat tubes from a direction perpendicular to the flow of the refrigerant.

When the heat exchanger functions as an evaporator, a two-phase gas-liquid refrigerant flows into the header. In the header, the distribution of the gas-phase refrigerant and the liquid-phase refrigerant having a higher density than the gas-phase refrigerant tends to be uneven in the stacking direction of the flat tubes. Therefore, the refrigerant distribution condition to each flat tube tends to be uneven.

In order to achieve uniform heat transfer across the entire stacked body including the flat tubes and the fins, and to achieve uniform distribution of the refrigerant as described above, it is possible to sufficiently obtain necessary performance, and various studies have been made on the setting of passages through which the refrigerant can efficiently flow in the header and the flat tubes, the structure of the header, the shape of the fins, and the like.

However, in order to secure a heat transfer area necessary for a predetermined heat exchange performance, a plurality of rows of heat exchange units (assemblies including flat tubes and fins) may be arranged in a direction connecting the windward and leeward (for example, patent document 1).

In patent document 1, there are no separate headers on the windward side (front row) and the leeward side (rear row), and the flat tubes in the front row and the flat tubes in the rear row are connected to a single header, and a plurality of horizontal partition plates are provided inside the header. The flat tubes in the front row and the flat tubes in the rear row of the same layer in the direction in which the flat tubes are stacked communicate with each other in the same region partitioned by the horizontal partition plates. The refrigerant flowing from the refrigerant pipe into each region in the header flows through the flat tubes in the front row and the flat tubes in the rear row for each layer.

Prior art documents

Patent document

Patent document 1: japanese patent No. 5840291

Disclosure of Invention

Problems to be solved by the invention

If a plurality of partition plates are provided inside the header, the number of components increases even if heat transfer loss due to uneven refrigerant distribution can be suppressed. Even when the front and rear headers are combined into one header as in patent document 1, the number of partitions is still required by the number of layers, and since the number of components is large, it is desirable to avoid the header from being divided finely by the partitions.

In addition, in the heat exchanger functioning as an evaporator in winter, since frost is formed from the front row where the temperature difference with the air is large, it is impossible to avoid unevenness in the state of frost formed between the front row and the rear row. Therefore, if the wind path is blocked by the frost formation in the front row and the air volume in the rear row is decreased, the amount of frost formation is still small, and therefore, the air duct does not function as early as possible even in the rear row where heat exchange is possible.

In view of the above, an object of the present invention is to provide a heat exchanger capable of suppressing heat transfer loss and ensuring evaporation performance in the case where there is unevenness in frost formation from the front and unevenness in distribution of refrigerant from a header to each flat tube.

Means for solving the problems

A first heat exchanger according to the present invention includes a plurality of stacked flat tubes, fins provided on the flat tubes, and headers erected in a stacking direction of the stack of flat tubes and connected to the flat tubes, and is characterized in that the heat exchanger functions as an evaporator that exchanges heat between refrigerant flowing into the flat tubes through the headers and air to evaporate the refrigerant, and heat exchange units including the flat tubes, the fins, and the headers are arranged so as to include a front row located on an upstream side of the flow of the air and a rear row located on a downstream side of the flow of the air, and a flow path cross-sectional area in the header in the front row, which is a header in the front row, is smaller than a flow path cross-sectional area in the header in the rear row, which is a header in the rear row, such that a flow velocity of the refrigerant flowing through the header in the front row is larger than a flow velocity of the refrigerant flowing through the header in the rear row.

In the first heat exchanger according to the present invention, it is preferable that the heat exchanger includes a partition portion extending in the stacking direction and partitioning an interior of at least one of the front-row header and the rear-row header, and the flow path cross-sectional area is set by the partition portion.

In the first heat exchanger according to the present invention, it is preferable that the width of the flat tubes in the rear row in the air flow direction is wider than the width of the flat tubes in the front row in the air flow direction.

Preferably, the first heat exchanger of the present invention includes two or more heat exchange units connected in series, and the most downstream heat exchange unit is located in the front row.

Preferably, the first heat exchanger of the present invention includes three or more heat exchange units connected in series, and the most upstream heat exchange unit is positioned in the front row.

The second heat exchanger of the present invention includes a plurality of flat tubes stacked, fins provided on the flat tubes, and headers erected in the stacking direction of the stack of flat tubes and connected to the flat tubes, characterized in that the heat exchanger functions as an evaporator for exchanging heat between the refrigerant flowing into the flat tubes through the headers and air to evaporate the refrigerant, the heat exchange unit composed of the flat tubes, the fins, and the headers is arranged so as to include a front row located on an upstream side of the flow of the air and a rear row located on a downstream side of the flow of the air, the heat exchanger is provided with a flow rate adjustment portion, the flow rate adjusting part adjusts the flow rate of the refrigerant introduced into at least one of a front row header which is a header in a front row and a rear row header which is a header in a rear row, so that the flow rate of the refrigerant flowing in the header in the front row is larger than the flow rate of the refrigerant flowing in the header in the rear row.

A third heat exchanger according to the present invention is a heat exchanger including a plurality of stacked flat tubes, fins provided on the flat tubes, and headers erected in a stacking direction of the stack of flat tubes and connected to the flat tubes, the heat exchanger functioning as an evaporator that causes a refrigerant flowing into the flat tubes through the headers to exchange heat with air to evaporate the refrigerant, wherein heat exchange units including the flat tubes, the fins, and the headers are arranged so as to include a front row located on an upstream side of a flow of the air and a rear row located on a downstream side of the flow of the air, and the heat exchange units in the front row and the heat exchange units in the rear row are arranged at positions shifted in the stacking direction so that an introduction portion of a region where the refrigerant is introduced into the header in the front row and an introduction portion of a region where the refrigerant is introduced into the header in the rear row are different in the stacking direction.

Preferably, the third heat exchanger of the present invention includes two heat exchange units stacked in the stacking direction in the front row and two heat exchange units stacked in the stacking direction in the rear row.

Effects of the invention

According to the present invention, as described later, since the balance of the heat transfer amount in the stacking direction (vertical direction) of the flat tubes can be achieved as a whole of the front row and the rear row, even if the partition plate is not provided in order to make the refrigerant distribution uniform, it is possible to avoid the decrease in the heat exchange performance due to the uneven refrigerant distribution, and also, even in an operation condition in which frost is generated, it is possible to delay the time for switching to the defrosting operation while retaining the heat exchange performance at least on the lower layer side of the rear row.

Drawings

Fig. 1 is a perspective view schematically showing a heat exchanger of a first embodiment.

Fig. 2 is a schematic view for explaining a difference in flow rate of the refrigerant flowing in the front header and the rear header shown in fig. 1.

Fig. 3 (a) to (c) are graphs showing distribution conditions of the liquid-phase refrigerant to the flat tubes in the front row and the rear row, respectively, for each refrigerant flow rate.

Fig. 4 is a schematic diagram for explaining the operation of the heat exchanger shown in fig. 1.

Fig. 5 is a schematic diagram showing a front row header and a rear row header of a modification of the first embodiment.

Fig. 6 is a schematic view showing a heat exchange unit in the front row and a heat exchange unit in the rear row of another modification of the first embodiment.

Fig. 7 (a) is a schematic view showing a heat exchanger of the second embodiment. Fig. 7 (b) is a schematic diagram showing a heat exchanger according to a modification of the second embodiment. Fig. 7 (c) and (d) are diagrams showing the distribution of the liquid-phase refrigerant in the case where the dryness is high.

Fig. 8 (a) is a schematic diagram showing a heat exchanger of the third embodiment. Fig. 8 (b) is a schematic diagram showing a modification of the third embodiment.

Fig. 9 (a) and (b) are schematic views each showing a heat exchanger according to the fourth embodiment. Illustration of the fins is omitted.

Detailed Description

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

[ first embodiment ]

The heat exchanger 1 shown in fig. 1 includes a front row heat exchange unit 10 and a rear row heat exchange unit 20. The heat exchanger 1 constitutes a refrigerant circuit of an air conditioner, a refrigerator, a water heater, or the like. The refrigerant circuit includes a compressor, a condenser, a decompression section, and a heat exchanger 1 as an evaporator.

According to the heat exchanger 1 of the present embodiment, as will be described later, the uneven distribution and the uneven frost formation of the refrigerant from the

headers

13 and 23 to the flat tubes 11 are received, and the reduction of the heat exchange performance is suppressed.

(Heat exchange Unit)

The front row heat exchange unit 10 includes a plurality of stacked flat tubes 11 (tubes), a plurality of fins 12, and a pair of front row headers 13(13A, 13B) connected to the flat tubes 11.

The front row heat exchange unit 10 exchanges heat between the refrigerant flowing into each flat tube 11 through the front row header 13(13A) and the air flowing into the gaps between the fins 12 and the flat tubes 11 from the direction perpendicular to the flat tubes 11.

The rear row heat exchange unit 20 includes a plurality of stacked flat tubes 11, a plurality of fins 12, and a pair of rear row headers 23(23A, 23B) connected to the flat tubes 11, as in the front row heat exchange unit 10, and exchanges heat between the refrigerant flowing into each flat tube 11 through the rear row header 23(23A) and the air.

The flat tubes 11 and the fins 12 of the front row heat exchange unit 10 are the same constituent units as the flat tubes 11 and the fins 12 of the rear row heat exchange unit 20.

Here, the direction in which the flat tubes 11 are stacked (stacking direction) is referred to as a vertical direction D1.

In the flow of air that exchanges heat with the refrigerant flowing through the flat tubes 11, the upstream side is referred to as "front" and the downstream side is referred to as "rear". It is preferable that the air sucked by the fins and the like not shown is supplied to the entire region of the heat exchanger 1.

The front and rear

heat exchange units

10 and 20 are arranged in the flow direction of air (indicated by hollow arrows). In each figure, the front column is denoted by "F" and the rear column by "R".

The front row heat exchange unit 10 and the rear row heat exchange unit 20 are connected in parallel to the piping of the refrigerant circuit. The same flow rate of refrigerant flows in the front and rear

heat exchange units

10 and 20.

The heat exchanger 1 includes

heat exchange units

10 and 20 at least in part. The heat exchanger 1 may include other heat exchange means not shown in the drawings in addition to the heat exchange means 10 and 20.

(Flat tube)

The flat tubes 11 are flat tubes through which the refrigerant flows, and extend linearly with a predetermined length. Both end portions of the flat tubes 11 are connected to the header 13 (or the header 23), respectively. The

headers

13, 23 are formed with insertion holes (not shown) for accommodating the end portions of the flat tubes 11 in the

headers

13, 23.

The plurality of flat tubes 11 are stacked in parallel with each other at a predetermined interval in the vertical direction D1. The end of each flat tube 11 opens into the header 13 (or the header 23).

(fins)

The fins 12 of the present embodiment have a substantially rectangular plate-like outer shape, and are provided on the flat tubes 11 in order to increase the surface area in contact with air. The fins 12 are formed with a plurality of notches 121 into which the flat tubes 11 are inserted. The shape of the front row F fins 12 and the rear row R fins 12 may be different.

In fig. 1, the front row F and the rear row R each show only a part of the fins 12. In fact, in any of the front row F and the rear row R, a plurality of fins 12 are provided at intervals in the stack of flat tubes 11 in the longitudinal direction of the flat tubes 11.

Instead of the plate-like fins 12, other types of fins may be provided in the flat tubes 11. For example, corrugated fins may be provided between the flat tubes 11 adjacent to each other in the vertical direction D1.

The flat tubes 11, the fins 12, the header 13 on the front row, and the header 23 on the rear row constituting the heat exchanger 1 are made of a metal material such as an aluminum alloy or a copper alloy. The heat exchanger 1 is configured by integrating these components using a bonding material such as a brazing material.

(prostate header)

The pair of header pipes 13 in the front row F are each erected in the stacking direction (D1) of the flat tubes 11 in the front row F. The header pipes 13 are connected to the flat tubes 11 in the front row F.

The pair of header pipes 13 are each formed in a cylindrical shape, and have closed upper and lower ends.

The refrigerant flows into the flat tubes 11 through one (13A) of the pair of front row headers 13, and the refrigerant flows out from the flat tubes 11 to the other (13B) of the pair of front row headers 13.

The front row header 13A is provided with an introduction portion 131 for introducing the refrigerant into the front row header 13 from refrigerant piping or the like, not shown. The header 13A has a flow path through which the refrigerant introduced through the introduction portion 131 flows upward.

If the introduction portion 131 is located below the flat tubes 11 arranged at the lowermost position in the header 13A, the gas-phase refrigerant floating from the introduction portion 131 and the liquid refrigerant rising together with the gas-phase refrigerant can be made to flow into any of the flat tubes 11 in the front row F including the lowermost flat tubes 11, which is preferable.

The refrigerant introduced into the header 13A in the front row is distributed to flow into the flat tubes 11 in the front row F. While the refrigerant flows through each flat tube 11 (dashed arrows in fig. 1), the air passing through the gaps (air passages) between the fins 12 and the flat tubes 11 exchanges heat with the refrigerant inside the flat tubes 11. At this time, the refrigerant flowing through the flat tubes 11 absorbs heat from the air and evaporates.

The refrigerant flowing through each flat tube 11 merges into the interior of the header 13B, and flows out from the header 13B to the refrigerant piping outside the heat exchanger 1, for example. Alternatively, when the heat exchanger 1 includes another heat exchange unit connected to the header 13B, the refrigerant flows out from the header 13B to the other heat exchange unit.

(rear tube)

The following header 23 is configured similarly to the header 13 except that the flow path cross-sectional area is different from that of the header 13, and therefore, the description will be made briefly.

The refrigerant flows into the flat tubes 11 of the rear row R through one (23A) of the pair of rear row headers 23, and the refrigerant flows out from the flat tubes 11 of the rear row R to the other (23B) of the pair of rear row headers 23.

The rear header 23A includes an introduction portion 231 for introducing the refrigerant into the rear header 23 from a refrigerant pipe or the like.

The refrigerant introduced into the interior of the rear row header 23A through the introduction portion 231 is distributed to flow into the flat tubes 11 of the rear row R. The refrigerant flowing through each flat tube 11 in the rear row R exchanges heat with the air having passed through the front row F, then merges into the rear row header 23B, and flows out from the rear row header 23B to the refrigerant pipe outside the heat exchanger 1 or another heat exchange unit.

The heat exchanger 1 is basically disposed and used such that the front row header 13 and the rear row header 23 are along the vertical direction D1 (vertical direction). At this time, the flat tubes 11 extend in the horizontal direction and are stacked in the vertical direction D1.

However, the front row header 13 and the rear row header 23 may be slightly inclined with respect to the vertical direction D1.

(Main feature of the present embodiment)

The main feature of the present embodiment is that the flow path sectional area Af (fig. 2) in the header 13 in the front row is smaller than the flow path sectional area Ar (fig. 2) in the header 23 in the rear row so that the flow speed of the refrigerant flowing through the header 13 in the front row is larger than the flow speed of the refrigerant flowing through the header 23 in the rear row.

The front row header 13 and the rear row header 23 of the present embodiment each have a flow path with a circular cross section, and the inner diameter of the front row header 13 is smaller than the inner diameter of the rear row header 23.

The cross-sectional shapes of the front row header 13 and the rear row header 23 may be appropriate shapes such as a rectangle and an ellipse.

As shown in fig. 5, the appropriate flow path cross-sectional areas Af, Ar may be set by providing the

vertical partition plates

14, 24 inside the front row header 13 and the rear row header 23. Only one of the

vertical partition plates

14 and 24 may be provided.

The vertical partition plate 14 stands along a vertical direction D1 perpendicular to the paper surface of fig. 5, and partitions the interior of the header 13 in the front row into a region 141 on the introduction portion 131 side and a region 142 on the flat tube 11 side.

The refrigerant introduced from the introduction portion 131 into the region 141 flows into the region 142 through the opening 14A penetrating the lower end portion of the vertical partition plate 14 in the thickness direction, and is distributed to the flat tubes 11 while flowing upward in the region 142.

The vertical partition plate 24 is also configured similarly to the vertical partition plate 14 described above, and divides the interior of the rear row header 23 into a region 241 on the introduction portion 231 side and a region 242 on the flat tube 11 side. An opening 24A is formed in the lower end of the vertical partition plate 24.

When the positions of the

vertical partition plates

14, 24 are set so that the dimension G2 of the gaps between the vertical partition plates 24 and the end portions of the flat tubes 11 is larger than the dimension G1 of the gaps between the vertical partition plates 14 and the flat tubes 11, the flow path cross-sectional area Ar larger than the flow path cross-sectional area Af of the region 142 of the header 13 in the front row can be given to the region 242 of the header 23 in the rear row.

(operation of the present embodiment)

As shown in fig. 2, the refrigerant flowing into the front header 13A from the pipe of the refrigerant circuit through the introduction portion 131 at a predetermined flow rate flows upward in the front header 13A at a flow velocity Vf corresponding to the flow path cross-sectional area Af of the front header 13A, and is distributed to the flat tubes 11 in the front row.

On the other hand, the refrigerant flowing into the interior of the rear row header 23A from the pipe of the refrigerant circuit through the introduction portion 231 at the same flow rate as the refrigerant flowing into the introduction portion 131 of the front row header 13A flows upward in the interior of the rear row header 23A at the flow velocity Vr corresponding to the flow path cross-sectional area Ar of the rear row header 23A and is distributed to the flat tubes 11 in the rear row.

Here, the flow rate of the refrigerant flowing into the front row header 13 through the introduction portion 131 is made equal to the flow rate of the refrigerant flowing into the rear row header 23 through the introduction portion 231, and the flow path cross-sectional area is Af < Ar, so that the flow velocity is Vf > Vr. That is, the flow velocity Vf of the refrigerant flowing in the header 13A is larger than the flow velocity Vr of the refrigerant flowing in the header 23A.

The length of the arrows shown in grey in fig. 2 schematically represents the relative magnitude of the flow rates Vf, Vr.

The gas-liquid two-phase flow refrigerant expanded through the decompression portion of the refrigerant circuit flows into the front header 13A and the rear header 23A. The gas-phase component of the refrigerant is referred to as a gas-phase refrigerant, and the liquid-phase component is referred to as a liquid-phase refrigerant. The liquid-phase refrigerant is entrained into the floating gas-phase refrigerant and conveyed upward. Since the density of the liquid-phase refrigerant is higher than that of the gas-phase refrigerant, the gas-phase refrigerant and the liquid-phase refrigerant tend to be unevenly distributed in the up-down direction D1 in each of the front header 13A and the rear header 23A.

Such distribution conditions of the vapor-phase refrigerant and the liquid-phase refrigerant differ in the front header 13A and the rear header 23A based on the difference in the flow rates Vf, Vr.

In the header 13A of the front row having the large flow velocity Vf, the liquid-phase refrigerant is carried further upward than in the header 23A of the rear row having the relatively small flow velocity Vr. Therefore, the liquid-phase refrigerant has a relatively high ratio to the gas-phase refrigerant in the upper portion of the flow path from the lower end to the upper end of the header 13A, and the liquid-phase refrigerant has a relatively low ratio to the gas-phase refrigerant in the lower portion of the flow path. The liquid-phase refrigerant that is phase-changed to the gas phase during the flow of the flat tubes 11 absorbs heat from the air based on latent heat. If the flow rate ratio of the liquid-phase refrigerant is high, the heat transfer amount between the air and the refrigerant is large.

The width of the gray arrows shown in fig. 2 indicates the ratio of the liquid-phase refrigerant to the gas-phase refrigerant on the basis of the flow rate. The flow rate ratio of the liquid-phase refrigerant gradually increases from below toward above in the header 13A.

On the other hand, in the rear header 23A having a small flow rate Vr, the liquid-phase refrigerant is less likely to be conveyed upward than in the front header 13A, and therefore, the range in which the liquid-phase refrigerant can be sufficiently conveyed from the introduction portion 231 remains at the lower portion of the flow path of the rear header 23A.

Therefore, in contrast to the header 13A in the front row described above, the ratio of the liquid-phase refrigerant to the gas-phase refrigerant is high in the lower portion of the flow passage of the header 23A, and the ratio of the liquid-phase refrigerant to the gas-phase refrigerant is low in the upper portion of the flow passage.

As described above, in either of the distribution condition of the liquid-phase refrigerant distributed from the front row header 13A to the flat tubes 11 in the front row F and the distribution condition of the liquid-phase refrigerant distributed from the rear row header 23A to the flat tubes 11 in the rear row R, the unevenness in the vertical direction D1 is differently observed.

Fig. 3 shows the flow rate ratio (flow rate ratio with respect to the gas-phase refrigerant) of the liquid-phase refrigerant among the refrigerants flowing into the flat tubes 11 in the front row F and the rear row R based on the experimental results in the case (a) where the flow rate of the refrigerant introduced into the heat exchanger 1 is small, the case (b) where the flow rate is medium, and the case (c) where the flow rate is large. The uppermost flat tubes 11 of the front row header 13A and the rear row header 23A are given

numbers

1, 2, 3, respectively, in the order of the lower side. In the experiment for obtaining the data of fig. 3 (a) to (c), the heat exchange unit in the front row and the heat exchange unit in the rear row each including 7 flat tubes 11 were used.

In any of the cases (a) to (c) of fig. 3, the same tendency as described above is shown in which the proportion of the liquid-phase refrigerant flowing in is higher as the flat tubes 11 are located upward in the front row F, and conversely, the proportion of the liquid-phase refrigerant flowing in is higher as the flat tubes 11 are located downward in the rear row R.

According to (a) to (c) of fig. 3, the greater the refrigerant flow rate, the greater the degree of non-uniformity in the flow rate ratio of the liquid-phase refrigerant in the vertical direction D1 of the leading row F. Conversely, the greater the refrigerant flow rate, the smaller the degree of unevenness in the flow rate ratio of the liquid-phase refrigerant in the vertical direction D1 in the rear row R. This tendency is qualitatively established because the flow path cross-sectional area of the front row header 13 is smaller than the flow path cross-sectional area of the rear row header 23.

As the flow rate in fig. 3 (c), a situation where frosting is likely to occur is assumed, for example, the flow rate of the heat exchanger 1 in the heating operation condition of the air conditioner in winter. As described above, when the flow rate is large, the liquid-phase refrigerant becomes highly uneven upward in the front row F as shown in fig. 3 (c). At this time, in the heat exchange unit 10 of the front row F, heat exchange is performed mainly with the upper layer.

(Effect of the present embodiment)

In the present embodiment, as described above, the flow path cross-sectional areas Af, Ar of the front row header 13 and the rear row header 23 are different from each other, so that different distributions are provided to the liquid-phase refrigerant in the front row F and the rear row R. In this way, heat transfer loss is suppressed and heat exchange performance is ensured as the whole heat exchanger 1.

The operation of the present embodiment will be described with reference to fig. 4 and 2. According to the present embodiment, even if the flow rate ratio of the liquid phase of the refrigerant distributed to each flat tube 11 is not uniform in each of the front row F and the rear row R, the heat transfer amount is made uniform in the entire heat exchanger 1, and necessary heat exchange performance is ensured even if there is a limit to the capacity of the heat exchanger or the like.

In the header 13 (fig. 2) of the front row having a large flow velocity, the liquid-phase refrigerant is sufficiently conveyed upward, and therefore, of the flat tubes 11 of the front row F to which the refrigerant is distributed from the header 13, the heat transfer amount between the refrigerant flowing through the upper-layer flat tube 11 having a large flow rate ratio of the liquid-phase refrigerant and the air is large, whereas the heat transfer amount in the lower portion is small.

On the other hand, in the rear row header 23 (fig. 2) having a smaller flow rate than the front row header 13, the liquid-phase refrigerant is hardly carried upward, and therefore, of the flat tubes 11 in the rear row R to which the refrigerant is distributed from the rear row header 23, the heat transfer amount between the refrigerant flowing through the lower-layer flat tubes 11 having a larger flow rate ratio of the liquid-phase refrigerant and the air is large, whereas the heat transfer amount in the upper portion is small.

The air flowing along the arrow 1 shown in fig. 4 passes through the lower layer side of the front row F where the heat conductivity is small and the lower layer side of the rear row R where the heat conductivity is large. Here, even if the heat is not sufficiently dissipated to the refrigerant by the air passing through the lower layer side of the front row F having a low flow rate of the liquid-phase refrigerant, the liquid-phase refrigerant flows through the flat tubes 11 on the lower layer side of the rear row R into which the front row F flows in a sufficient amount to sufficiently dissipate the heat of the air.

The air flowing along arrow 2 shown in fig. 4 passes through the upper layer side of the front row F having a large thermal conductivity and the upper layer side of the rear row R having a small thermal conductivity. Here, in the upper layer side of the front row F, air that has radiated heat to the refrigerant having a high flow rate of the liquid-phase refrigerant flows into the rear row R. Therefore, the amount of the liquid-phase refrigerant flowing into the flat tubes 11 on the upper layer side of the rear row R is sufficient to exchange heat with the air having dissipated heat in the front row F.

As described above, in the entire heat exchanger 1 in which the upper layer side and the lower layer side of the front row F and the upper layer side and the lower layer side of the rear row R are combined, the heat transfer surface is effectively utilized while avoiding the heat transfer loss, and therefore, even if the heat exchanger 1 is small, the heat exchange performance can be sufficiently ensured. By providing a flow velocity difference to the front row header 13 and the rear row header 23 as in the present embodiment, as described above, the heat transfer amount in the vertical direction D1 can be balanced for the entire front row F and the rear row R. In this way, since a decrease in heat exchange performance due to uneven refrigerant distribution can be avoided, it is not necessary to provide horizontal partition plates in the

headers

13, 23 in order to uniformize the refrigerant distribution. Therefore, the increase in the number of components is avoided, and therefore, the manufacturing cost of the heat exchanger 1 can be suppressed.

Even if the flow channel cross-sectional area is set to Af > Ar and the flow velocity Vf of the front row header 13 is made smaller than the flow velocity Vr of the rear row header 23 contrary to the present embodiment, the same effect as that of the present embodiment can be obtained from the viewpoint of avoiding performance degradation due to uneven refrigerant distribution.

In addition, the present embodiment is also capable of coping with performance degradation due to frost formation in addition to performance degradation due to uneven refrigerant distribution. In the heat exchanger 1 used for the outdoor heat exchanger of the air conditioner, when the temperature of the outside air as the heat source is low during the heating operation, frost formation starts from the front row F where the temperature difference with the air in contact is larger than that in the rear row R. Alternatively, frost formation may occur in the heat exchanger 1 for cooling of a heat load, such as an interior heat exchanger for a refrigerator or freezer, for example, a refrigeration showcase, or a refrigerator or the like.

In order to avoid performance degradation due to frost formation, the relationship between the flow rates Vf and Vr of the

headers

13 and 23 may be determined so that the flow rate Vf of the header 13 in the front row is greater than the flow rate Vr of the header 23 in the rear row, as in the present embodiment. In the present embodiment, in which the same flow rate of refrigerant is introduced into the front row F and the rear row R, the flow path cross-sectional area is defined as Af < Ar.

In the front row F where frosting is likely to occur, the upper layer side having a large liquid phase flow rate ratio is sufficiently cooled by the refrigerant having a large liquid phase flow rate ratio, and therefore frosting is less likely to occur even in the lower layer side of the front row F as compared with frosting being likely to occur. That is, the same unevenness of frost formation as the unevenness of the liquid phase flow rate of the front row F in the vertical direction D1 (for example, fig. 3 (c)) was observed.

Here, as shown in fig. 3 (c), the upper side of the front row F having a large liquid phase flow rate ratio is frosted, and the air passage is blocked by the frost, and the air volume on the upper side of the rear row R is decreased. However, since the frost formation on the lower layer side of the front row F does not progress much at this time, the air volume can be maintained at least on the lower layer side of the rear row R which becomes downwind on the lower layer side of the front row F.

That is, after the heat exchange capacity on the upper layer side is lost due to frosting including the rear row R, air is sent to the rear row R on the lower layer side, and the heat exchange capacity remains on the heat transfer surface on the lower layer side of the rear row R to which frost is not attached, so that the time until switching to the defrosting operation is extended.

According to the present embodiment, heat transfer loss due to frost formation is also suppressed, and thus, it is possible to avoid interruption of the heating operation or the like due to the defrosting operation, and to continue the heating operation or the like.

Fig. 6 shows an example in which the flat tubes 11 inserted into the header tubes 23 in the rear row having a larger diameter than the header tubes 13 in the front row are given a width Dr wider than the width Df of the flat tubes 11 in the front row F. In order to increase the heat transfer area, it is preferable that the width Dr of the flat tubes 11 in the direction in which the air flows be increased to the same extent as the diameter of the header 23 in the subsequent row. By increasing the width Dr of the flat tubes 11 in the rear row R, the capacity of the heat exchanger 1 can be increased without changing the space required for installation of the heat exchanger 1.

Instead of increasing the width Dr of the flat tubes 11 in the rear row R, two flat tubes 11 may be arranged in the width direction.

[ second embodiment ]

Next, a second embodiment of the present invention will be described with reference to fig. 7.

In the second embodiment, an application example to a heat exchanger including a plurality of passages connected in series is shown.

The heat exchanger 2 shown in fig. 7 (a) includes

heat exchange units

10 and 20 corresponding to passages connected in series. This point is different from the case where the

heat exchange units

10 and 20 of the heat exchanger 1 according to the first embodiment are connected in parallel to the pipes of the refrigerant circuit.

Fig. 7 (a) schematically shows the

heat exchange units

10 and 20, but the

heat exchange units

10 and 20 are configured similarly to the first embodiment (fig. 1).

That is, as shown in fig. 1, the front row heat exchange unit 10 includes flat tubes 11, fins 12, and a front row header 13. The rear row heat exchange unit 20 also includes flat tubes 11, fins 12, and a rear row header 23. The flow path cross-sectional area Af of the front row header 13 is smaller than the flow path cross-sectional area Ar of the rear row header 23, and therefore the refrigerant flow velocity Vf of the front row header 13 is larger than the refrigerant flow velocity Vr of the rear row header 23.

Based on this flow velocity difference, as in the first embodiment, the heat conduction amount in the vertical direction D1 is balanced for the entire front row F and the rear row R, and the time for switching to the defrosting operation at the time of frost formation can be delayed.

The rear heat exchange unit 20 corresponds to the most upstream first passage P1. The front row heat exchange unit 10 corresponds to the second passage P2 following the first passage P1. Here, the second passage P2 is the most downstream passage.

While the refrigerant flows from the most upstream passage P1 to the most downstream passage P2, the dryness of the refrigerant increases.

When the refrigerant is introduced from a refrigerant pipe (not shown) into the rear row header 23A (fig. 1) of the first passage P1, the refrigerant is distributed from the rear row header 23A to the flat tubes 11 in the rear row R. The refrigerant flowing through these flat tubes 11 merges in the rear header 23B (fig. 1) and flows into the second passage P2 in the front row F through the U-shaped tubes 17. Next, the refrigerant is distributed to the flat tubes 11 in the front row F from the front row header 13B (fig. 1) of the second passage P2, and the refrigerant having passed through these flat tubes 11 flows out from the front row header 13A (fig. 1) to the refrigerant pipes.

Here, if the refrigerant absorbs heat from the air and the dryness increases, the absolute amount of the liquid phase flow rate ratio decreases, and therefore it is difficult to cause the liquid-phase refrigerant to flow into the upper-layer flat tubes 11 facing the inside of the header of the most downstream passage P2 in particular.

Both fig. 7 (c) and 7 (d) show the liquid-phase refrigerant distribution in the case where the dryness of the refrigerant is high based on experiments, but the flow path cross-sectional areas of the headers are different between (c) and (d). Fig. 7 (c) shows a case where the flow channel cross-sectional area of the manifold is a typical size (for example, Am in fig. 8), and fig. 7 (d) shows a case where the flow channel cross-sectional area of the manifold is smaller than the typical size. In fig. 7 (c) and (d), since the refrigerant flow rates are the same, the flow velocity in the header is large when the flow path cross-sectional area is small (fig. 7 (d)). Therefore, in fig. 7 (d), the liquid-phase refrigerant reaches the flat tubes 11 further above than in fig. 7 (c) where the flow velocity is relatively small.

Based on this, as shown in fig. 7 (a), the most downstream passage P2 having the highest dryness is disposed in the front row F. In the header pipe 13 in the front row having a large flow velocity due to a small flow path cross-sectional area, the liquid-phase refrigerant can be sufficiently lifted upward and can flow into the flat tubes 11 located upward. Therefore, the heat transfer surface of the most downstream passage P2 can be also fully utilized to contribute to performance.

[ modification of the second embodiment ]

As shown in fig. 7 (b), when the heat exchanger 2A includes three or more passages connected in series, the downstream-most fourth passage P4 is preferably disposed in the front row F, and the upstream-most first passage P1 is also preferably disposed in the front row F, as in fig. 7 (a).

The second passage P2 and the third passage P3 are disposed in the rear row R.

The heat exchanger 2A includes four passages P1 to P4. The upstream first passage P1 and the downstream second passage P2 are located at the lower portion of the heat exchanger 2A, and the downstream third passage P3 and the downstream fourth passage P4 are located at the upper portion of the heat exchanger 2A.

On the upstream side of the series circuit in the heat exchanger 2A, the liquid phase is more than on the downstream side where the dryness is increased, and therefore the pressure loss is smaller on the same flow path cross-sectional area than on the downstream side. Therefore, the height of the heat exchanger 2A is suppressed by suppressing the flow path cross-sectional area of the upstream passages P1 and P2 to such an extent that the pressure loss does not become excessively large (by reducing the number of layers (the number of flat tubes 11)) as compared with the downstream passages P3 and P4.

In fig. 7 (b), the

heat exchange units

10 and 20 are also schematically illustrated, but the

heat exchange units

10 and 20 are configured similarly to the first embodiment (fig. 1).

Based on the difference in flow velocity between the front row header 13 and the rear row header 23, as in the first embodiment, the heat transfer amount can be balanced for the entire front row F and the rear row R, and the time for switching to the defrosting operation at the time of frost formation can be delayed.

In the configuration shown in fig. 7B, when the refrigerant is introduced into the header 13A (fig. 1) of the first passage P1, the refrigerant is distributed from the header 13A to the flat tubes 11 in the front row F, and the refrigerant flowing through the flat tubes 11 merges into the header 13B (fig. 1) in the front row and flows into the second passage P2 in the rear row R through the U-shaped tubes 181. Then, the refrigerant is distributed to the flat tubes 11 from the rear row header 23B of the second passage P2, and the refrigerant having flowed through these flat tubes 11 flows from the rear row header 23A through the U-shaped tubes 182 into the rear row header 23A of the third passage P3 on the upper layer side. Then, the fluid flows through the flat tubes 11 of the third passage P3, passes through the U-shaped tubes 183, and flows into the header 13B in the front row of the fourth passage P4. Then, the refrigerant flows through the flat tubes 11 of the fourth passage P4 and flows out of the refrigerant pipes.

According to the configuration shown in fig. 7 (b), as in the second embodiment shown in fig. 7 (a), by disposing the most downstream passage P4 having the highest dryness in the front row F, the heat transfer surface of the most downstream passage P4 can be sufficiently utilized to contribute to the performance.

In addition, since the dryness of the refrigerant flowing into the header 13 is the lowest, the flow path cross-sectional area of the header 13 of the most upstream passage P1, in particular, the header 13A at the inlet of the passage P1, in which the refrigerant pressure loss is relatively small, is small, and thus the increase in the evaporation temperature due to the refrigerant pressure loss can be suppressed. By suppressing the increase in the evaporation temperature, the decrease in evaporation performance can be avoided.

(third embodiment)

Next, a third embodiment of the present invention will be described with reference to fig. 8.

The heat exchanger 3 of the third embodiment shown in fig. 8 (a) includes a front row heat exchange unit 10 and a rear row heat exchange unit 20, as in the heat exchanger 1 (fig. 2) of the first embodiment.

In order to make the flow velocity Vf of the header 13 greater than the flow velocity Vr of the header 23, in the first embodiment (fig. 2), the header 13 is provided with a flow path cross-sectional area Af smaller than the flow path cross-sectional area Ar of the header 23, while in the third embodiment, a distributor 15 (flow rate adjustment portion) capable of adjusting the flow rates of the refrigerant introduced into the header 13 and the header 23 is used.

The distributor 15, which is configured to include a capillary tube or the like, divides the refrigerant flowing into the refrigerant piping, not shown, at a predetermined flow rate ratio so that the flow rate Rf of the refrigerant flowing into the header 13 is greater than the flow rate Rr of the refrigerant flowing into the header 23.

Then, the flow rate Vf corresponding to the flow rate Rf and the flow path sectional area Am is given to the header 13, and the flow rate Vr corresponding to the flow rate Rr and the flow path sectional area Am is given to the header 23.

In the present embodiment, the flow path cross-sectional area Am of the front row header 13 is equal to the flow path cross-sectional area Am of the rear row header 23, and therefore Rf/Rr is equal to Vf/Vr.

According to the present embodiment, even if the flow path cross-sectional areas of the front row header 13 and the rear row header 23 are equal, the flow velocity difference of the refrigerant can be given to the front row header 13 and the rear row header 23 by providing the distributor 15, and the same operational effects as those of the first embodiment can be obtained based on the distribution of the liquid phase flow rate ratio in the vertical direction D1 due to the difference in flow velocity.

Further, by using the same header pipes having the same diameter, it is possible to prevent an assembly error of the front row heat exchange unit 10 and the rear row heat exchange unit 20 from occurring in advance when the heat exchanger 3 is manufactured.

As shown in fig. 8 (b), a throttle unit 16 (flow rate adjustment unit) may be used instead of the distributor 15. In a pipe line branched at an equal flow rate from a refrigerant pipe not shown, the throttle portion 16 is provided at one of the introduction rear row headers 23. By giving a pressure loss to the refrigerant flowing toward the rear header 23 by the expansion portion 16, the flow rate Rr of the refrigerant introduced into the rear header 23 is smaller than the flow rate Rf of the refrigerant introduced into the front header 13.

[ fourth embodiment ]

Next, a fourth embodiment of the present invention will be described with reference to fig. 9.

Fig. 9 (a) and (b) show the heat exchanger 4 having the same configuration. Fig. 9 (a) and (b) are different in the image of the distribution of only the liquid-phase refrigerant.

The heat exchanger 4 of the fourth embodiment includes two heat exchange units 10 stacked in the vertical direction D1 in the front row F and two heat exchange units 20 stacked in the vertical direction D1 in the rear row R.

In the heat exchanger 4, the front row heat exchange unit 10 and the rear row heat exchange unit 20 are disposed offset from each other in the vertical direction D1, and the front row heat exchange unit 10 and the rear row heat exchange unit 20 are configured to have the same height from the lower end to the upper end thereof.

The front row heat exchange unit 10 and the rear row heat exchange unit 20 are connected in parallel or in series to the piping of the refrigerant circuit, and the same flow rate of refrigerant flows through the front row heat exchange unit 10 and the rear row heat exchange unit 20.

The heat exchanger 4 includes a front row heat exchange unit 10 and a rear row heat exchange unit 20 having the same configuration as that of the first embodiment. Unlike the first embodiment, the flow path cross-sectional area of the header 13 in the front row and the header 23 in the rear row are equal.

The front row heat exchange unit 10 and the rear row heat exchange unit 20 are displaced in the vertical direction D1 so that the position of the introduction portion 131 to the front row header 13 and the position of the introduction portion 231 to the rear row header 23 differ in the vertical direction D1.

When the flow rate of the liquid-phase refrigerant is small or when the dryness is high, in fig. 9 (a), the flow velocities of the liquid-phase refrigerant flowing into the

headers

13 and 23 are slow as indicated by gray arrows along the vertical direction D1 in the image of the distribution of the liquid-phase refrigerant. Therefore, the liquid-phase refrigerant easily flows into the lower flat tubes 11 of the

headers

13, 23.

On the other hand, when the flow rate of the liquid-phase refrigerant is large or when the dryness is low, the flow velocity of the liquid-phase refrigerant is high as shown by gray arrows along the vertical direction D1 in the image of the distribution of the liquid-phase refrigerant in fig. 9 (b). Therefore, the liquid-phase refrigerant easily flows into the upper flat tubes 11, which are the upper portions of the

headers

13, 23.

Therefore, as described with reference to fig. 4, the heat conduction amount in the vertical direction D1 can be balanced for the entire front row F and the rear row R, and the time for switching to the defrosting operation at the time of frost formation can be delayed.

Further, by using the same header pipes having the same diameter, it is possible to prevent an assembly error of the front row heat exchange unit 10 and the rear row heat exchange unit 20 from occurring in advance when the heat exchanger 4 is manufactured.

In the fourth embodiment, the interior of the front row header 13 and the rear row header 23 is partitioned into a plurality of regions, and introduction portions for introducing the refrigerant into the respective regions may be prepared. In this case, the height positions of the introduction portion of the front row F and the introduction portion of the rear row R can be made different by displacing the front row heat exchange unit 10 and the rear row heat exchange unit 20 in the vertical direction D1, and therefore, the same operational effects can be obtained.

In addition to the above embodiments, the configurations described in the above embodiments may be selected or appropriately changed to other configurations without departing from the spirit of the present invention.

For example, the heat exchanger of the present invention may include 1 or more columns located midway between the front row F and the rear row R in addition to the front row F and the rear row R.

In each of the above embodiments, each of the

heat exchange units

10 and 20 includes a row of flat tube units each including a plurality of flat tubes 11 stacked in the vertical direction D1. The heat exchange unit of the present invention may be configured to include two rows of two flat tube units arranged in the air flow direction, and the two flat tube units may be connected to the same header.

Description of reference numerals:

1-4. a heat exchanger;

a front row heat exchange unit;

a flat tube;

a fin;

13. a header of a lead line;

a vertical separation plate (partition);

an opening;

a distributor (flow regulator);

a throttling part (flow rate adjusting part);

a U-shaped tube;

a rear row heat exchange unit;

23. 23A, 23b.. rear header;

a vertical separation plate (partition);

an opening;

an incision;

an introduction portion;

a region;

181. 182, 183.. U-shaped tubes;

an introduction portion;

a region;

an area;

af. Ar, Am... flow path cross-sectional area;

a top-bottom direction;

df. Dr.. width;

prostate;

g1... size;

g2... size;

a P1-P4.

R.. the last column;

rf, Rr... flow rate;

vf, Vr..

Claims

1. A heat exchanger including a plurality of stacked flat tubes, fins provided on the flat tubes, and headers erected in a stacking direction of the stacked flat tubes and connected to the flat tubes,

the heat exchanger functions as an evaporator that exchanges heat between the refrigerant flowing into the flat tubes through the header and air to evaporate the refrigerant,

the heat exchange units constituted by the flat tubes, the fins, and the headers are arranged so as to include a front row located on an upstream side of the flow of the air and a rear row located on a downstream side of the flow of the air,

a flow passage cross-sectional area in a header of the front row is smaller than a flow passage cross-sectional area in a header of the rear row so that a flow velocity of the refrigerant flowing through the header of the front row is larger than a flow velocity of the refrigerant flowing through the header of the rear row.

2. The heat exchanger of claim 1,

the heat exchanger includes a partition portion extending in the stacking direction and partitioning an interior of at least one of the front header and the rear header,

the flow path cross-sectional area is set by the partition.

3. The heat exchanger according to claim 1 or 2,

the width of the flat tubes in the rear row in the air flow direction is wider than the width of the flat tubes in the front row in the air flow direction.

4. The heat exchanger according to claim 1 or 2,

the heat exchanger includes two or more heat exchange units connected in series,

the heat exchange unit most downstream is located in the front row.

5. The heat exchanger according to claim 1 or 2,

the heat exchanger includes three or more heat exchange units connected in series,

the most upstream heat exchange unit is located in the front row.

6. A heat exchanger including a plurality of stacked flat tubes, fins provided on the flat tubes, and headers erected in a stacking direction of the stacked flat tubes and connected to the flat tubes,

the heat exchanger includes a flow rate adjustment portion that adjusts a flow rate of the refrigerant introduced into at least one of a front row header that is the header of the front row and a rear row header that is the header of the rear row such that a flow velocity of the refrigerant flowing through the front row header is greater than a flow velocity of the refrigerant flowing through the rear row header,

the flow path cross-sectional area in the front row of manifolds is equal to the flow path cross-sectional area in the rear row of manifolds.

7. A heat exchanger including a plurality of stacked flat tubes, fins provided on the flat tubes, and headers erected in a stacking direction of the stacked flat tubes and connected to the flat tubes,

an introduction portion that introduces the refrigerant into a region in the header of the leading row is provided at a lower end of the header of the leading row,

an introduction portion that introduces the refrigerant into a region within the header of the rear row is provided at a lower end of the header of the rear row,

the heat exchange unit in the front row and the heat exchange unit in the rear row are arranged offset in the stacking direction such that an introduction portion of the refrigerant into a region in the header in the front row and an introduction portion of the refrigerant into a region in the header in the rear row are different in position in the stacking direction.

8. The heat exchanger of claim 7,

the heat exchanger includes two heat exchange units stacked in the stacking direction in the front row, and two heat exchange units stacked in the stacking direction in the rear row.