JP6946105B2 - Heat exchanger - Google Patents

Description

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

Heat exchangers in which refrigerant flows through a plurality of stacked flat tubes are used in equipment such as air conditioners and refrigerators, and constitute a refrigerant circuit for these equipment.
A heat exchanger is constructed by assembling a plurality of flat tubes with plate-shaped or corrugated fins and a pair of headers. Each flat pipe is connected to a pair of headers at both ends, and the refrigerant introduced into the header from the piping of the refrigerant circuit is distributed to each flat pipe. The refrigerant flowing through each flat pipe and the air flowing into the gap between the fins and the flat pipe from a direction orthogonal to the flow of the refrigerant exchange heat.

When the heat exchanger functions as an evaporator, a gas-liquid two-phase flow refrigerant flows into the header. Inside the header, the distribution of the vapor phase refrigerant and the liquid phase refrigerant having a higher density than the vapor phase refrigerant tends to be biased in the stacking direction of the flat tubes. Therefore, the distribution state of the refrigerant to each flat pipe tends to be biased.
Including the uniform distribution of the refrigerant, the amount of heat transfer is made uniform throughout the laminate consisting of the flat pipe and fins, so that the required performance can be sufficiently obtained. Various ideas have been made for the setting of the path, the structure of the header, the shape of the fins, etc.

By the way, in order to secure the heat transfer area required for a predetermined heat exchange performance, a plurality of rows of heat exchange elements (assemblies including flat tubes and fins) may be arranged in the direction connecting the windward and the leeward (for example). , Patent Document 1).
In Patent Document 1, there are no separate headers on the leeward side (front row) and the leeward side (rear row), and the flat pipes in the front row and the flat pipes in the back row are connected to a single header. A large number of horizontal dividers are installed. In the same section partitioned by these horizontal partition plates, the flat pipes in the front row and the flat pipes in the rear row of the same stage in the flat pipe stacking direction communicate with each other. The refrigerant that has flowed from the refrigerant pipe into each section in the header flows through the flat pipes in the front row and the back row for each stage.

Patent No. 5840291

If a large number of partition plates are installed inside the header, heat transfer loss due to uneven distribution of the refrigerant can be suppressed, but the number of parts increases. Even when the headers in the front row and the back row are combined into one as in Patent Document 1, a partition plate for the number of stages is still required and the number of parts is large, so it is desirable to avoid finely partitioning the inside of the header with the partition plate. ..

Further, in a heat exchanger that functions as an evaporator in winter, frost formation proceeds from the front row, which has a large temperature difference with air, so that a bias in the frost formation state between the front row and the back row is unavoidable. Therefore, if the air passage is blocked by frost on the front row and the air volume in the rear row decreases, even the rear row, which can exchange heat because the amount of frost is still small, does not function at an early stage.

Based on the above, the present invention can suppress heat transfer loss and ensure evaporation performance in the presence of uneven frost formation that progresses from the front row and uneven distribution of refrigerant from the header to each flat tube. The purpose is to provide a exchanger.

The first heat exchanger of the present invention comprises a plurality of stacked flat tubes, fins provided on the flat tubes, and a header standing in the stacking direction in which the flat tubes are laminated and connected to the flat tubes. A heat exchanger provided, which functions as an evaporator that exchanges heat between air and a refrigerant flowing into a flat tube through a header to evaporate the refrigerant, and a heat exchange element composed of a flat tube, fins, and a header. The front row located on the upstream side of the air flow and the back row located on the downstream side of the air flow are arranged including the front row, and the flow velocity of the refrigerant flowing through the front row header, which is the header of the front row, is the back row, which is the header of the back row. The flow path cross-sectional area in the front row header is smaller than the flow path cross-sectional area in the back row header so as to be larger than the flow velocity of the refrigerant flowing through the header.

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

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

The first heat exchanger of the present invention preferably includes two or more heat exchange elements connected in series, with the most downstream heat exchange element located in the front row.

The first heat exchanger of the present invention preferably includes three or more heat exchange elements connected in series, with the most upstream heat exchange element located in the front row.

The second heat exchanger of the present invention comprises a plurality of stacked flat tubes, fins provided on the flat tubes, and a header standing in the stacking direction in which the flat tubes are laminated and connected to the flat tubes. A heat exchanger provided, which functions as an evaporator that exchanges heat between the refrigerant flowing into the flat tube through the header and air to evaporate the refrigerant, and a heat exchange element composed of the flat tube, fins, and header. The front row located on the upstream side of the air flow and the back row located on the downstream side of the air flow are arranged including the front row, and the flow velocity of the refrigerant flowing through the front row header, which is the header of the front row, is the back row, which is the header of the back row. It is characterized by including a flow rate adjusting unit that adjusts the flow rate of the refrigerant introduced into at least one of the front row header and the back row header so as to be larger than the flow velocity of the refrigerant flowing through the header.

The third heat exchanger of the present invention comprises a plurality of stacked flat tubes, fins provided on the flat tubes, and a header standing in the stacking direction in which the flat tubes are laminated and connected to the flat tubes. A heat exchanger provided, which functions as an evaporator that exchanges heat between air and a refrigerant flowing into a flat tube through a header to evaporate the refrigerant, and a heat exchange element composed of a flat tube, fins, and a header. The position of the introduction part, which is arranged including the front row located on the upstream side of the air flow and the back row located on the downstream side of the air flow, and introduces the refrigerant into the section internal to the header of the front row, and the position of the rear row. and the position of the inlet portion for introducing a refrigerant into compartment inherent in header, differently in the laminating direction, a heat exchange element of the front row, and the back row of heat exchange elements disposed shifted in the stacking direction, from the inlet portion The section into which the refrigerant is introduced is characterized in that at least two flat tubes are arranged .

The third heat exchanger of the present invention preferably includes two heat exchange elements laminated in the stacking direction in the front row and two heat exchange elements laminated in the stacking direction in the rear row.

According to the present invention, as will be described later, it is possible to balance the amount of heat transfer in the stacking direction (vertical direction) of the flat tubes as a whole in the front row and the back row, so that a partition plate is installed to make the refrigerant distribution uniform. Even if it is not done, the deterioration of heat exchange performance due to the uneven distribution of the refrigerant can be avoided, and even in the operation situation where frost formation occurs, the operation is switched to the defrosting operation while leaving the heat exchange capacity at least on the lower side of the rear row. You can delay the time until.

It is a perspective view which shows typically the heat exchanger which concerns on 1st Embodiment. It is a schematic diagram for demonstrating the difference in the flow velocity of the refrigerant flowing through the front row header and the back row header shown in FIG. (A) to (c) are graphs showing the distribution status of the liquid phase refrigerant to the respective flat pipes in the front row and the back row for each degree of the refrigerant flow rate. It is a schematic diagram for demonstrating the operation of the heat exchanger shown in FIG. It is a schematic diagram which shows the front row header and the back row header which concerns on the modification of 1st Embodiment. It is a schematic diagram which shows the heat exchange element of the front row and the heat exchange element of a back row which concerns on another modification of 1st Embodiment. (A) is a schematic view showing the heat exchanger according to the second embodiment. (B) is a schematic diagram showing a heat exchanger according to a modified example of the second embodiment. (C) and (d) are diagrams showing the liquid phase refrigerant distribution when the degree of dryness is high. (A) is a schematic view showing the heat exchanger according to the third embodiment. (B) is a schematic diagram showing a modified example of the third embodiment. Both (a) and (b) are schematic views showing the heat exchanger according to the fourth embodiment. The fins are not shown.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[First Embodiment]
The heat exchanger 1 shown in FIG. 1 includes a front row heat exchange element 10 and a back row heat exchange element 20. The heat exchanger 1 constitutes a refrigerant circuit such as an air conditioner, a refrigerator, and a water heater. The refrigerant circuit includes a compressor, a condenser, a decompression unit, and a heat exchanger 1 which is an evaporator.

According to the heat exchanger 1 of the present embodiment, as will be described later, while accepting the uneven distribution of the refrigerant from the headers 13 and 23 to the flat tubes 11 and the uneven frost formation, the deterioration of the heat exchange performance is suppressed. do.

(Heat exchange element)
The front row heat exchange element 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 element 10 is provided between the refrigerant flowing into each flat pipe 11 through the front row header 13 (13A) and the air flowing into the gap between the fins 12 and the flat pipe 11 from the direction orthogonal to the flat pipe 11. , Heat exchange.

Similar to the front row heat exchange element 10, the back row heat exchange element 20 includes a plurality of stacked flat tubes 11, a plurality of fins 12, and a pair of back row headers 23 (23A, 23B) connected to the flat tubes 11. Is provided, and heat is exchanged between the refrigerant flowing into each flat pipe 11 through the rear row header 23 (23A) and the air.
The flat tube 11 and the fin 12 are components common to the front row heat exchange element 10 and the back row heat exchange element 20.

Here, the direction in which the flat tubes 11 are laminated (stacking direction) is referred to as the vertical direction D1.
Further, the upstream side of the air flow that exchanges heat with the refrigerant flowing through the flat pipe 11 is referred to as "front", and the downstream side is referred to as "rear". It is preferable that the air sucked by a fan or the like (not shown) is supplied to the entire region of the heat exchanger 1.
The front row heat exchange element 10 and the back row heat exchange element 20 are arranged in the direction in which air flows (indicated by white arrows). In each figure, the front row is indicated by "F" and the back row is indicated by "R".

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

The heat exchanger 1 includes heat exchange elements 10 and 20 at least in part. The heat exchanger 1 may include other heat exchange elements (not shown) in addition to the heat exchange elements 10 and 20.

(Flatten)
The flat pipe 11 is a flat pipe through which the refrigerant flows, and extends linearly with a predetermined length. Both ends of the flat tube 11 are connected to the header 13 (or the header 23), respectively. The headers 13 and 23 are formed with insertion holes (not shown) for receiving the ends of the flat tubes 11 into the headers 13 and 23.
The plurality of flat tubes 11 are laminated in parallel with each other at predetermined intervals in the vertical direction D1. The end of each flat tube 11 is open to the inside of the header 13 (or header 23).

(fin)
The fin 12 of the present embodiment has a substantially rectangular plate-like (plate-like) outer shape, and is provided on the flat tube 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 shapes of the fins 12 in the front row F and the fins 12 in the back row R may be different.

In FIG. 1, both the front row F and the back row R show only a part of the fins 12. Actually, in both the front row F and the rear row R, a large number of fins 12 are provided in the laminated body of the flat pipe 11 at intervals in the length direction of the flat pipe 11.

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

Members such as the flat tube 11, fins 12, front row header 13, and back row header 23 constituting the heat exchanger 1 are formed of a metal material such as an aluminum alloy or a copper alloy. The heat exchanger 1 is configured by integrating these with a joining material such as a brazing material.

(Front row header)
Each of the pair of front row headers 13 stands upright in the stacking direction (D1) of the flat pipes 11 in the front row F. Each flat tube 11 of the front row F is connected to these front row headers 13.
Each of the pair of front row headers 13 is formed in a cylindrical shape, and the upper end and the lower end are closed.
Refrigerant flows into each flat pipe 11 through one (13A) of the pair of front row headers 13, and the refrigerant flows out from each flat pipe 11 to the other (13B) of the pair of front row headers 13.

The front row header 13A is provided with an introduction unit 131 for introducing the refrigerant into the front row header 13 from a refrigerant pipe or the like (not shown). The inside of the front row header 13A is a flow path through which the refrigerant introduced through the introduction section 131 flows upward.
If the introduction portion 131 is located below the flat tube 11 arranged at the lowest position in the front row header 13A, any of the flat tubes 11 in the front row F including the lowermost flat tube 11 can be used. It is preferable because the gas-phase refrigerant floating from the introduction unit 131 and the liquid refrigerant lifted together with the gas-phase refrigerant can flow in.

The refrigerant introduced into the front row header 13A is distributed and flows into each flat pipe 11 of the front row F. Then, while the refrigerant flows through each of the flat pipes 11 (dashed line arrow in FIG. 1), the air passing through the gap (air passage) between the fins 12 and the flat pipes 11 and the refrigerant inside the flat pipes 11 Heat exchange takes place. At this time, the refrigerant flowing through the flat tube 11 absorbs heat from the air and evaporates.

The refrigerant flowing through each of the flat pipes 11 merges inside the front row header 13B, and flows out from the front row header 13B to the refrigerant pipe or the like outside the heat exchanger 1. Alternatively, if the heat exchanger 1 includes another heat exchange element connected to the front row header 13B, the refrigerant flows out of the front row header 13B to the other heat exchange element.

(Back row header)
The back row header 23 has the same configuration as the front row header 13 except that the flow path cross-sectional area is different from that of the front row header 13, and thus will be briefly described.
Refrigerant flows into each flat pipe 11 of the back row R through one of the pair of back row headers 23 (23A), and the refrigerant flows out from each flat pipe 11 of the back row R to the other (23B) of the pair of back row headers 23. do.

The back row header 23A is provided with an introduction portion 231 for introducing the refrigerant from the refrigerant pipe or the like into the inside of the back row header 23.
The refrigerant introduced into the rear row header 23A through the introduction portion 231 is distributed and flows into each flat pipe 11 of the rear row R. The refrigerant flowing through each of the flat pipes 11 in the back row R is heat-exchanged with the air passing through the front row F, and then merges inside the rear row header 23B. , Flows out to other heat exchange elements.

The heat exchanger 1 is basically used by arranging the front row header 13 and the back row header 23 along the vertical direction D1 (vertical direction). At this time, the flat tube 11 extends in the horizontal direction and is laminated in the vertical direction D1.
However, the front row header 13 and the back row header 23 may be slightly inclined with respect to the vertical direction D1.

(Main features of this embodiment)
In the present embodiment, the flow path cross-sectional area Af (FIG. 2) in the front row header 13 is in the back row header 23 so that the flow velocity of the refrigerant flowing in the front row header 13 is larger than the flow velocity of the refrigerant flowing in the back row header 23. The main feature is that it is smaller than the flow path cross-sectional area Ar (FIG. 2).

Both the front row header 13 and the back row header 23 of the present embodiment have a flow path having a circular cross section, and the inner diameter of the front row header 13 is smaller than the inner diameter of the back row header 23.
The cross-sectional shape of the front row header 13 and the back row header 23 may be an appropriate shape such as a rectangular shape or an elliptical shape.

As shown in FIG. 5, by installing the vertical partition plates 14 and 24 inside the front row header 13 and the back row header 23, it is possible to set appropriate flow path cross-sectional areas Af and Ar. Only one of the vertical partition plates 14 and 24 may be installed.

The vertical partition plate 14 stands up along the vertical direction D1 orthogonal to the paper surface of FIG. 5, and partitions the inside of the front row header 13 into a section 141 on the introduction portion 131 side and a section 142 on the flat tube 11 side. ing.
The refrigerant introduced from the introduction portion 131 into the compartment 141 flows into the compartment 142 through the opening 14A penetrating the lower end portion of the vertical partition plate 14 in the thickness direction, and flows upward in the compartment 142 to each flat pipe 11 Is distributed to.

The vertical partition plate 24 is also configured in the same manner as the vertical partition plate 14 described above, and the inside of the back row header 23 is divided into a compartment 241 on the introduction portion 231 side and a compartment 242 on the flat pipe 11 side. An opening 24A is formed at the lower end of the vertical partition plate 24.

The vertical partition plate 14, When the position of 24 is set, the flow path cross-sectional area Ar larger than the flow path cross-sectional area Af of the section 142 of the front row header 13 can be given to the section 242 of the back row header 23.

(Action according to this embodiment)
As shown in FIG. 2, the refrigerant that has flowed into the front row header 13A from the piping of the refrigerant circuit through the introduction section 131 at a predetermined flow rate has a flow velocity Vf corresponding to the flow path cross-sectional area Af of the front row header 13A and is the front row header 13A. It is distributed to each flat pipe 11 in the front row while flowing upward inside the pipe.

On the other hand, the refrigerant flowing from the piping of the refrigerant circuit into the back row header 23A through the introduction section 231 at the same flow rate as the refrigerant flowing into the introduction section 131 of the front row header 13A corresponds to the flow path cross-sectional area Ar of the back row header 23A. It is distributed to each flat tube 11 in the back row while flowing upward through the inside of the back row header 23A at the flow velocity Vr.

Here, the flow rates of the refrigerant flowing into the front row header 13 through the introduction unit 131 and the refrigerant flowing into the rear row header 23 through the introduction unit 231 are the same, and the flow path cross-sectional area is Af <Ar. The flow velocity is Vf> Vr. That is, the flow velocity Vf of the refrigerant flowing through the front row header 13A is larger than the flow velocity Vr of the refrigerant flowing through the rear row header 23A.
The length of the arrow shown in gray in FIG. 2 schematically represents the relative magnitude of the flow velocities Vf and Vr.

A gas-liquid two-phase flow refrigerant that has expanded through the decompression portion of the refrigerant circuit flows into the front row header 13A and the back row 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 caught in the floating vapor phase refrigerant and carried upward. Since the density of the liquid phase refrigerant is higher than the density of the gas phase refrigerant, the distribution of the gas phase refrigerant and the liquid phase refrigerant in the vertical direction D1 tends to be biased in each of the front row header 13A and the back row header 23A.
The distribution of the gas phase refrigerant and the liquid phase refrigerant differs between the front row header 13A and the back row header 23A based on the difference in the flow velocities Vf and Vr.

In the front row header 13A having a large flow velocity Vf, the liquid phase refrigerant is carried higher than in the back row header 23A having a relatively small flow velocity Vr. Therefore, the ratio of the liquid phase refrigerant to the gas phase refrigerant is relatively high in the upper part of the flow path from the lower end to the upper end of the front row header 13A, and the ratio of the liquid phase refrigerant to the gas phase refrigerant is low in the lower part of the flow path. .. The liquid-phase refrigerant that undergoes a phase transition to the gas phase while flowing through the flat tube 11 absorbs heat from the air based on latent heat. When the flow rate ratio of the liquid phase refrigerant is high, the amount of heat transferred between the air and the refrigerant is large.
The width of the gray arrow shown in FIG. 2 represents the ratio of the liquid phase refrigerant to the flow rate-based gas phase refrigerant. The flow rate ratio of the liquid phase refrigerant gradually increases from the bottom to the top.

On the other hand, in the back row header 23A having a small flow velocity Vr, the liquid phase refrigerant is more difficult to be carried upward than in the front row header 13A. Stay at the bottom.
Therefore, contrary to the above-mentioned front row header 13A, the ratio of the liquid phase refrigerant to the gas phase refrigerant is high in the lower part of the flow path of the back row header 23A, and the ratio of the liquid phase refrigerant to the gas phase refrigerant is high in the upper part of the flow path. Is low.

From the above, the distribution status of the liquid phase refrigerant distributed from the front row header 13A to each flat pipe 11 in the front row F, and the distribution status of the liquid phase refrigerant distributed from the rear row header 23A to each flat pipe 11 in the back row R. In each case, the bias in the vertical direction D1 is recognized in a different manner.

FIG. 3 shows the front row F and the back row R based on the experimental results when the flow rate of the refrigerant introduced into the heat exchanger 1 is low (a), medium (b), and high (c). The flow rate ratio of the liquid-phase refrigerant (flow rate ratio to the gas-phase refrigerant) in the refrigerant flowing into each of the flat tubes 11 of the above is shown. Numbers 1, 2, 3, ... Are given in order from the flat tube 11 located at the uppermost position of the front row header 13A and the back row header 23A, respectively. In the experiment for obtaining the data of FIGS. 3A to 3C, a front row heat exchange element and a back row heat exchange element having seven flat tubes 11 were used.

In all of FIGS. 3A to 3C, in the front row F, the higher the flat tube 11 is located, the higher the proportion of the inflowing liquid phase refrigerant is, and conversely, in the rear row R, the flat tube 11 is downward. The position is higher, the proportion of the inflowing liquid phase refrigerant is higher, showing the same tendency as described above.
From FIGS. 3A to 3C, as the refrigerant flow rate increases, the degree of deviation of the flow rate ratio of the liquid phase refrigerant in the vertical direction D1 of the front row F increases. On the contrary, the degree of deviation of the flow rate ratio of the liquid phase refrigerant in the vertical direction D1 of the rear row R becomes smaller as the refrigerant flow rate increases. 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 back row header 23.

As the flow rate according to FIG. 3C, it is assumed that frost formation is likely to occur, for example, the flow rate of the heat exchanger 1 under the heating operation state of the air conditioner in winter. When the flow rate is large as described above, the uneven distribution of the liquid phase refrigerant upward in the front row F becomes remarkable as shown in FIG. 3C. At this time, in the heat exchange element 10 in the front row F, heat exchange is performed mainly in the upper stage.

(Effect of this embodiment)
In the present embodiment, as described above, by making the flow path cross-sectional areas Af and Ar of the front row header 13 and the back row header 23 different, different distributions are given to the liquid phase refrigerants of the front row F and the back row R. .. By doing so, the heat transfer loss of the heat exchanger 1 as a whole is suppressed and the heat exchange performance is ensured.

The operation of this embodiment will be described with reference to FIG. According to the present embodiment, even if there is a bias in the liquid phase flow ratio of the refrigerant distributed to each flat tube 11 in each of the front row F and the back row R, the heat transfer amount of the heat exchanger 1 as a whole is increased. Aim for uniformity and ensure the required heat exchange performance even when there are restrictions on the capacity of the heat exchanger.

In the front row header 13 (FIG. 2) where the flow velocity is large, the liquid phase refrigerant is sufficiently carried upward, so that the flow rate ratio of the liquid phase refrigerant among the flat pipes 11 in the front row F in which the refrigerant is distributed from the front row header 13 is high. The amount of heat transfer between the refrigerant and the air flowing through the large flat tube 11 on the upper stage side is large, while the amount of heat transfer in the lower part is small.
On the other hand, in the back row header 23 (FIG. 2) in which the flow velocity is smaller than that of the front row header 13, the liquid phase refrigerant is not carried so much upward, and therefore, among the flat tubes 11 of the rear row R in which the refrigerant is distributed from the back row header 23, The amount of heat transfer between the refrigerant and the air flowing through the flat tube 11 on the lower stage side where the flow rate ratio of the liquid phase refrigerant is large is large, while the amount of heat transfer in the upper part is small.

The air flowing along the arrow 1 shown in FIG. 4 passes through the lower side where the amount of heat transfer is small in the front row F and the lower side where the amount of heat transfer is large in the rear row R. Here, even if the air that has passed through the lower side of the front row F having a low flow rate ratio of the liquid phase refrigerant is not sufficiently dissipated to the refrigerant, the flat pipe 11 on the lower side of the rear row R that flows in following the front row F. A sufficient amount of liquid-phase refrigerant is flowing in the air to sufficiently dissipate the air.

Further, the air flowing along the arrow 2 shown in FIG. 4 passes through the upper side having a large amount of heat transfer in the front row F and the upper side having a small amount of heat transfer in the rear row R. Here, on the upper side of the front row F, the air that has already been radiated to the refrigerant having a high flow rate ratio of the liquid phase refrigerant flows into the rear row R. Therefore, it is sufficient that a liquid phase refrigerant corresponding to the amount of heat exchange with the air after the heat is dissipated in the front row F flows through the flat tube 11 on the upper stage side of the rear row R that has flowed in.

From the above, the heat transfer surface is effectively utilized over the entire heat exchanger 1 including the upper and lower sides of the front row F and the upper and lower sides of the rear row R, while avoiding heat transfer loss. Even if the exchanger 1 is small, sufficient heat exchange performance can be ensured. By giving a flow velocity difference to the front row header 13 and the back row header 23 as in the present embodiment, as described above, the heat transfer amount in the vertical direction D1 can be balanced as a whole of the front row F and the back row R. By doing so, it is possible to avoid deterioration of the heat exchange performance due to the bias of the refrigerant distribution, so that it is not necessary to install horizontal partition plates in the headers 13 and 23 in order to make the refrigerant distribution uniform. Therefore, since the increase in the number of parts can be avoided, the manufacturing cost of the heat exchanger 1 can be suppressed.

Contrary to the present embodiment, even if the flow path cross-sectional area is set so that Af> Ar and the flow velocity Vf of the front row header 13 is smaller than the flow velocity Vr of the back row header 23, it is due to the bias of the refrigerant distribution. From the viewpoint of avoiding performance deterioration, the same effect of the present embodiment can be obtained.

Further, the present embodiment corresponds to the performance deterioration due to frost formation in addition to the performance deterioration due to the bias of the refrigerant distribution. In the heat exchanger 1 used for the outdoor heat exchanger of an air conditioner, if the temperature of the outside air, which is a heat source, is low during heating operation, frost formation proceeds from the front row F, which has a larger temperature difference from the contacting air than the rear row R. do. Alternatively, frost may also occur in the heat exchanger 1 used for cooling the heat load, such as a refrigerator / freezer showcase or an internal heat exchanger in a refrigerator / freezer, and even in that case, the front row F Frost progresses from.

From the viewpoint of avoiding performance deterioration due to frost formation, the relationship between the flow velocities Vf and Vr of the headers 13 and 23 is set so that the flow velocity Vf of the front row header 13 is larger than the flow velocity Vr of the back row header 23, as in the present embodiment. Good to identify. Then, in the present embodiment in which the refrigerant having the same flow rate is introduced into the front row F and the rear row R, the flow path cross-sectional area is specified as Af <Ar.

Among the front row F where frost is likely to occur, the upper side with a large liquid phase flow rate ratio is easy to frost because the air is sufficiently cooled by the refrigerant with a large liquid phase flow rate ratio, whereas the front row F also tends to frost. The lower side is hard to frost. That is, a bias in the liquid phase flow rate ratio in the vertical direction D1 (for example, a bias in frost formation similar to that in FIG. 3C) can be seen.

Here, as shown in FIG. 3C, frost formation on the upper side of the front row F, which has a large liquid phase flow rate ratio, progressed, and the air passage was blocked by the frost, so that the air volume on the upper side of the rear row R decreased. And. However, at this point, frost formation has not progressed so much on the lower side of the front row F, so that the air volume can be maintained at least on the lower side of the rear row R, which is leeward of the lower side of the front row F.
That is, even after the heat exchange capacity on the upper row side including the rear row R is lost due to frost formation, air is sent to the rear row R on the lower row side, and heat transfer on the lower row side of the rear row R without frost is attached. Since the heat exchange capacity is left on the surface, the time until switching to the defrosting operation is extended.
According to the present embodiment, by suppressing the heat transfer loss due to frost formation, it is possible to avoid interruption of the heating operation or the like due to the defrosting operation and continue the heating operation or the like.

FIG. 6 shows an example in which a flat pipe 11 inserted into the back row header 23 having a diameter larger than that of the front row header 13 is given a width Dr wider than the width Df of the flat pipe 11 in the front row F. In order to improve the heat transfer area, it is preferable to secure a large width Dr of the flat tube 11 in the direction of air flow to the same extent as the diameter of the back row header 23. By expanding the width Dr of the flat tube 11 in the rear row R, the capacity of the heat exchanger 1 can be improved without changing the space required for installing the heat exchanger 1.
Instead of expanding the width Dr of the flat pipe 11 in the back row R, two flat pipes 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.
The second embodiment shows an application example to a heat exchanger having a plurality of paths connected in series.
The heat exchanger 2 shown in FIG. 7A includes heat exchange elements 10 and 20 corresponding to paths connected in series. This point is different from the fact that the heat exchange elements 10 and 20 of the heat exchanger 1 of the first embodiment are connected in parallel with the piping of the refrigerant circuit.

Although the heat exchange elements 10 and 20 are schematically shown in FIG. 7A, the heat exchange elements 10 and 20 are configured in the same manner as in the first embodiment (FIG. 1).
That is, the front row heat exchange element 10 includes a flat tube 11, fins 12, and a front row header 13, as shown in FIG. The back row heat exchange element 20 also includes a flat tube 11, fins 12, and a back row header 23. Since 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 back row header 23, the refrigerant flow velocity Vf of the front row header 13 is larger than the refrigerant flow velocity Vr of the back row header 23.
Based on this flow velocity difference, as in the first embodiment, the heat transfer amount in the vertical direction D1 can be balanced as a whole in the front row F and the rear row R, and the time until switching to the defrosting operation at the time of frost formation can be delayed. can.

By the way, the back row heat exchange element 20 corresponds to the most upstream first pass P1. The front row heat exchange element 10 corresponds to the second pass P2 following the first pass P1. Here, the second pass P2 is the most downstream path.
While the refrigerant flows in from the most upstream path P1 and flows to the most downstream path P2, the dryness of the refrigerant increases.

When the refrigerant is introduced from the refrigerant pipe (not shown) into the rear row header 23A (FIG. 1) of the first pass P1, the refrigerant is distributed from the rear row header 23A to each of the flat pipes 11 in the rear row R. The refrigerants that have flowed through the flat pipes 11 merge inside the back row header 23B (FIG. 1), pass through the U-shaped pipe 17, and flow into the second pass P2 of the front row F. Then, the refrigerant is distributed from the front row header 13B (FIG. 1) of the second pass P2 to each of the flat pipes 11 of the front row F, and the refrigerant flowing through the flat pipes 11 is the front row header 13A (FIG. 1). Flows out to the refrigerant pipe.

Here, when the refrigerant absorbs heat from the air and the dryness increases, the absolute amount of the liquid phase flow rate ratio decreases. Is difficult to inflow.
Both FIGS. 7 (c) and 7 (d) show the liquid phase refrigerant distribution when the dryness of the refrigerant is high based on the experiment, but in (c) and (d), the flow path of the header is shown. The cross-sectional area is different. FIG. 7C shows a case where the flow path cross-sectional area of the header is a typical size (for example, Am in FIG. 7), and FIG. 7 (d) shows a typical flow path cross-sectional area of the header. The case where it is smaller than the size is shown. Since the refrigerant flow rates are the same in both FIGS. 7 (c) and 7 (d), the smaller the flow path cross-sectional area (FIG. 7 (d)), the larger the flow velocity in the header. Therefore, in FIG. 7 (d), the liquid phase refrigerant reaches the flat tube 11 above the flat tube 11 as compared with FIG. 7 (c) where the flow velocity is relatively small.

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

[Modified example of the second embodiment]
As shown in FIG. 7 (b), when the heat exchanger 2A has three or more paths connected in series, the most downstream fourth pass P4 is in the front row as in FIG. 7 (a). It is preferable to arrange it in F and also arrange the most upstream first pass P1 in the front row F.
The second pass P2 and the third pass P3 are arranged in the back row R.

The heat exchanger 2A includes four paths P1 to P4. The first pass P1 and the second pass P2 on the upstream side are located at the lower part in the heat exchanger 2A, and the third pass P3 and the fourth pass P4 on the downstream side are located at the upper part in the heat exchanger 2A.
Since the upstream side of the series circuit in the heat exchanger 2A has more liquid phases than the downstream side where the dryness has increased, the pressure loss in the same flow path cross-sectional area is smaller than that on the downstream side. Therefore, the flow path cross-sectional area of the upstream paths P1 and P2 is suppressed to such an extent that the pressure loss does not become excessive as compared with the downstream paths P3 and P4 (the number of stages (the number of flat pipes 11) is reduced), thereby causing heat. The height of the exchanger 2A is suppressed.

Although the heat exchange elements 10 and 20 are schematically shown in FIG. 7B, the heat exchange elements 10 and 20 are configured in the same manner as in the first embodiment (FIG. 1).
Based on the flow velocity difference between the front row header 13 and the back row header 23, the heat transfer amount of the front row F and the back row R as a whole is balanced as in the first embodiment, and the time until the operation is switched 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 pass P1, the refrigerant is distributed from the front row header 13A to each of the flat pipes 11 in the front row F, and these are distributed. The refrigerants that have flowed through the flat pipes 11 of the above merge with each other inside the front row header 13B (FIG. 1), pass through the U-shaped pipe 181 and flow into the second pass P2 of the back row R. Then, the refrigerant is distributed from the back row header 23B of the second pass P2 to each flat pipe 11, and the refrigerant flowing through each of the flat pipes 11 passes from the back row header 23A to the U-shaped pipe 182 on the upper stage side. It flows into the back row header 23A of the third pass P3. Further, it flows through the flat pipe 11 of the third pass P3, passes through the U-shaped pipe 183, and flows into the front row header 13B of the fourth pass P4. Then, it flows through the flat pipe 11 of the fourth pass P4 and flows out to the refrigerant pipe.

According to the configuration shown in FIG. 7 (b), as in the second embodiment shown in FIG. 7 (a), the most downstream path P4 having the highest dryness is arranged in the front row F. The heat transfer surface of the downstream path P4 can also be fully 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 path P1 in which the refrigerant pressure loss is relatively small, particularly the header 13A at the inlet of the path P1, is small. , It is possible to suppress an increase in evaporation temperature due to refrigerant pressure loss. By suppressing the increase in the evaporation temperature, it is possible to avoid a decrease in the evaporation performance.

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIG.
Similar to the heat exchanger 1 (FIG. 2) of the first embodiment, the heat exchanger 3 of the third embodiment shown in FIG. 8A includes a front row heat exchange element 10 and a back row heat exchange element 20. ing.
In the first embodiment, the front row header 13 is provided with a flow path cross-sectional area Af smaller than the flow path cross-sectional area Ar of the back row header 23 so that the flow velocity Vf of the front row header 13 is larger than the flow velocity Vr of the back row header 23. On the other hand, in the third embodiment, a distributor 15 (flow rate adjusting unit) capable of adjusting the flow rate of the refrigerant introduced into the front row header 13 and the back row header 23 is used.

The distributor 15 including the capillary tube and the like flows in from a refrigerant pipe (not shown) so that the flow rate Rf of the refrigerant flowing into the front row header 13 is larger than the flow rate Rr of the refrigerant flowing into the rear row header 23. The refrigerant is split at a predetermined flow rate ratio.
Then, the front row header 13 is given the flow velocity Vf corresponding to the flow rate Rf and the flow path cross-sectional area Am, and the back row header 23 is given the flow velocity Vr corresponding to the flow rate Rr and the flow path cross-sectional area Am.
In the present embodiment, the flow path cross-sectional area Am of the front row header 13 and the flow path cross-sectional area Am of the back row header 23 are equivalent, so Rf / Rr = Vf / Vr.

According to the present embodiment, by providing the distributor 15, even if the flow path cross-sectional areas of the front row header 13 and the back row header 23 are the same, the flow velocity difference of the refrigerant is given to the front row header 13 and the back row header 23. Based on the distribution of the liquid phase flow rate ratio in the vertical direction D1 due to the difference in the flow velocity, the same effect as that of the first embodiment can be obtained.
Further, by using the same headers having the same diameter, it is possible to prevent a mistake in assembling the front row heat exchange element 10 and the back row heat exchange element 20 at the time of manufacturing the heat exchanger 3.

Instead of the distributor 15, a throttle 16 (flow rate adjusting unit) can be used as shown in FIG. 8 (b). Of the pipelines that are separated from the refrigerant pipes (not shown) at the same flow rate, the throttle 16 is provided on one side of the pipeline that is introduced into the rear row header 23. Since the pressure loss is applied by the throttle 16 to the refrigerant introduced into the back row header 23, the flow rate Rr of the refrigerant introduced into the back row header 23 is smaller than the flow rate Rf of the refrigerant introduced into the front row header 13.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described with reference to FIG.
The heat exchanger 4 of the fourth embodiment includes two heat exchange elements 10 laminated in the vertical direction D1 in the front row F and two heat exchange elements 20 laminated in the vertical direction D1 in the rear row R. ..
In this heat exchanger 4, as shown in FIG. 9, the front row heat exchange element 10 and the back row heat exchange element 20 are arranged so as to be shifted in the vertical direction D1. It is configured to have the same height as the element 20.
Further, the front row heat exchange element 10 and the back row heat exchange element 20 are connected in parallel or in series with the piping of the refrigerant circuit, and the same flow rate of refrigerant flows through the front row heat exchange element 10 and the back row heat exchange element 20.

9 (a) and 9 (b) both show a heat exchanger 4 having the same configuration.
The heat exchanger 4 includes a front row heat exchange element 10 and a back row heat exchange element 20 configured in the same manner as in the first embodiment. However, unlike the first embodiment, the flow path cross-sectional areas of the front row header 13 and the back row header 23 are the same.

Since the front row heat exchange element 10 and the back row heat exchange element 20 are shifted in the vertical direction D1, the position of the introduction portion 131 leading to the front row header 13 and the position of the introduction portion 231 leading to the back row header 23 are up and down. Different in direction D1.

When the flow rate of the refrigerant is low or the dryness is high, the image of the distribution of the liquid phase refrigerant is shown in the headers 13 and 23 by the gray arrow along the vertical direction D1 in FIG. 9A. The flow velocity of each inflowing liquid phase refrigerant is slow. Therefore, the liquid phase refrigerant tends to flow into the flat pipe 11 at the lower part of the headers 13 and 23, that is, the lower stage side.
On the other hand, when the flow rate of the refrigerant is high or the dryness is low, the image of the distribution of the liquid-phase refrigerant is shown by the gray arrow along the vertical direction D1 in FIG. 9 (b). The flow velocity is fast. Therefore, the liquid phase refrigerant tends to flow into the upper part of the headers 13 and 23, that is, the flat pipe 11 on the upper stage side.

Then, as described with reference to FIG. 4, the heat transfer amount in the vertical direction D1 can be balanced as a whole in the front row F and the rear row R, and the time until switching to the defrosting operation at the time of frost formation can be delayed. ..
Further, by using the same headers having the same diameter, it is possible to prevent a mistake in assembling the front row heat exchange element 10 and the back row heat exchange element 20 at the time of manufacturing the heat exchanger 4.

In the fourth embodiment, the inside of the front row header 13 and the back row header 23 may be partitioned into a plurality of compartments, and an introduction portion for introducing the refrigerant may be prepared in each compartment. Even in that case, by shifting the front row heat exchange element 10 and the back row heat exchange element 20 in the vertical direction D1, 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. Similar effects can be obtained.

In addition to the above, as long as the gist of the present invention is not deviated, the configurations listed in the above embodiments can be selected or changed to other configurations as appropriate.
For example, the heat exchanger of the present invention may include one or more intermediate rows located between the front row F and the back row R in addition to the front row F and the back row R.

In each of the above embodiments, the heat exchange elements 10 and 20 each include a row of flat tube elements composed of a plurality of flat tubes 11 stacked in the vertical direction D1. Not limited to this, the heat exchange elements of the present invention include two rows, that is, two flat tube elements arranged in the direction of air flow, and these flat tube elements are configured to be connected to the same header. You may.

1-4 Heat exchanger 10 Front row heat exchange element 11 Flat tube 12 Fins 13, 13A, 13B Front row header 14 Vertical partition plate (partition)
14A Aperture 15 Distributor (Flow rate regulator)
16 Aperture (flow rate adjustment unit)
17 U-shaped tube 20 Back row heat exchange elements 23, 23A, 23B Back row header 24 Vertical partition plate (partition)
24A Opening 121 Notch 131 Introduction 141 Section 142 Section 181, 182, 183 U-shaped tube 231 Introduction 241 Section 242 Section Af, Ar, Am Flow path cross-sectional area D1 Vertical direction Df, Dr Width F Front row G1 Dimension G2 Dimension P1 P4 pass R back row Rf, Rr flow rate Vf, Vr flow velocity

Claims (8)

A heat exchanger comprising a plurality of stacked flat tubes, fins provided on the flat tubes, and a header standing in the stacking direction in which the flat tubes are laminated and connected to the flat tubes. ,
It functions as an evaporator that evaporates the refrigerant by exchanging heat between the refrigerant flowing into the flat tube through the header and air.
A heat exchange element consisting of the flat tube, the fins, and the header is arranged including a front row located upstream of the air flow and a rear row located downstream of the air flow.
The flow velocity of the refrigerant flowing through the front row header, which is the header in the front row, is larger than the flow velocity of the refrigerant flowing through the back row header, which is the header in the back row.
The flow path cross-sectional area in the front row header is smaller than the flow path cross-sectional area in the back row header.
A heat exchanger characterized by that. A partition portion extending in the stacking direction and partitioning the inside of at least one of the front row header and the back row header is provided.
The flow path cross-sectional area is set by the partition.
The heat exchanger according to claim 1. The width of the flat tube in the back row in the air flow direction is
Wider than the width of the flat tube in the front row in the air flow direction,
The heat exchanger according to claim 1 or 2. With two or more of the heat exchange elements connected in series
The most downstream heat exchange element is located in the front row.
The heat exchanger according to any one of claims 1 to 3. With three or more of the heat exchange elements connected in series
The most upstream heat exchange element is located in the front row.
The heat exchanger according to claim 4. A heat exchanger comprising a plurality of stacked flat tubes, fins provided on the flat tubes, and a header standing in the stacking direction in which the flat tubes are laminated and connected to the flat tubes. ,
It functions as an evaporator that evaporates the refrigerant by exchanging heat between the refrigerant flowing into the flat tube through the header and air.
A heat exchange element consisting of the flat tube, the fins, and the header is arranged including a front row located upstream of the air flow and a rear row located downstream of the air flow.
The flow velocity of the refrigerant flowing through the front row header, which is the header in the front row, is larger than the flow velocity of the refrigerant flowing through the back row header, which is the header in the back row.
A flow rate adjusting unit for adjusting the flow rate of the refrigerant introduced into at least one of the front row header and the back row header is provided.
A heat exchanger characterized by that. A heat exchanger comprising a plurality of stacked flat tubes, fins provided on the flat tubes, and a header standing in the stacking direction in which the flat tubes are laminated and connected to the flat tubes. ,
It functions as an evaporator that evaporates the refrigerant by exchanging heat between the refrigerant flowing into the flat tube through the header and air.
A heat exchange element consisting of the flat tube, the fins, and the header is arranged including a front row located upstream of the air flow and a rear row located downstream of the air flow.
The position of the introduction portion for introducing the refrigerant into the section inside the header in the front row and the position of the introduction portion for introducing the refrigerant into the section inside the header in the back row are different in the stacking direction. ,
The heat exchange elements in the front row and the heat exchange elements in the back row are arranged so as to be shifted in the stacking direction .
At least two flat tubes are arranged in the section where the refrigerant is introduced from the introduction portion.
A heat exchanger characterized by that. The two heat exchange elements laminated in the stacking direction in the front row,
The two heat exchange elements laminated in the stacking direction in the back row are provided.
The heat exchanger according to claim 7.

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