WO2019026436A1

WO2019026436A1 - Heat exchanger

Info

Publication number: WO2019026436A1
Application number: PCT/JP2018/022761
Authority: WO
Inventors: 秀哲立野井; 芳裕波良; 青木　泰高; 将之左海
Original assignee: 三菱重工サーマルシステムズ株式会社
Priority date: 2017-08-02
Filing date: 2018-06-14
Publication date: 2019-02-07
Also published as: EP3647711B1; CN110998215A; EP3647711C0; CN110998215B; JP6946105B2; JP2019027727A; EP3647711A1; ES2955923T3; EP3647711A4

Abstract

The purpose is to ensure evaporation capacity by suppressing heat transfer loss when there is deviation in frost formation progressing from a front row and deviation in the distribution of refrigerant from a header to flat tubes. A heat exchanger 1 comprises a plurality of flat tubes 11, fins 12 provided on the flat tubes 11, and a header 13 (or 23) standing in the vertical direction D1 in which the flat tubes 11 are stacked and connected to the flat tubes 11, and the heat exchanger functions as an evaporator that causes heat to be exchanged between air and refrigerant flowing into the flat tubes 11 through the header and causes the refrigerant to evaporate. A front row heat exchanging element 10 comprising flat tubes 11, fins 12, and the header 13, and a rear row heat exchanging element 20 comprising flat tubes 11, fins 12, and the header 23 are arranged. The cross-sectional area of the flow channel of the front row header 13 positioned in the front row F is smaller than the cross-sectional area of the flow channel of the rear row header 23 positioned in the rear row R so that the flow rate of the refrigerant flowing in the front row header 13 is larger than the flow rate of the refrigerant flowing in the rear row header 23.

Description

Heat exchanger

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

A heat exchanger in which a refrigerant flows through a plurality of stacked flat tubes is used in devices such as an air conditioner and a refrigerator, and constitutes a refrigerant circuit of the devices.
A heat exchanger is configured by assembling a plurality of flat tubes with plate-shaped or corrugated fins and a pair of headers. Each flat tube 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 tube. The refrigerant flowing through the flat tubes and the air flowing into the gap between the fins and the flat tubes from the direction orthogonal to the flow of the refrigerant are heat exchanged.

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 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 distribution state of the refrigerant to each flat tube tends to be uneven.
In the header and the flat tube, the refrigerant in the header or the flat tube is obtained so that the heat transfer amount is made uniform throughout the laminate including the flat tube and the fins including the uniformity of the distribution state of the coolant. Various contrivances have been made on the setting of paths that can flow efficiently, the structure of the header, the shape of the fins, and the like.

By the way, in order to secure a heat transfer area necessary for a predetermined heat exchange performance, a plurality of rows of heat exchange elements (an assembly including a flat tube and a fin) may be arranged in a direction connecting windward and windward (for example, , Patent Document 1).
In Patent Document 1, there are no separate headers on the windward side (front row) and the windward 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. A number of horizontal dividers are installed. In the same section partitioned by these horizontal partition plates, the flat tubes in the front row and the flat tubes in the rear row in the same step in the flat tube stacking direction communicate with each other. The refrigerant flowing from the refrigerant piping into each section in the header flows through the flat tubes in the front row and the rear row for each stage.

Patent No. 5840291

If a large number of partition plates are installed inside the header, although it is possible to suppress the heat transfer loss due to the uneven distribution of the refrigerant, the number of parts increases. Even when the headers in the front row and the rear row are combined into one as in Patent Document 1, it is also necessary to have a partition plate for the number of stages, and the number of parts is large. .

Moreover, in the heat exchanger which functions as an evaporator in winter, since frost formation proceeds from the front row where the temperature difference with air is large, it is not possible to avoid the deviation of the frosted state between the front row and the rear row. Therefore, if the air passage is blocked due to frost formation on the front row and the air volume in the rear row is reduced, the heat exchange amount is still small and even the heat exchangeable rear row does not function early.

From the above, according to the present invention, the heat transfer loss can be suppressed and the evaporation performance can be ensured in the presence of the uneven distribution of frost advancing from the front row and the uneven distribution of the refrigerant from the header to the flat tubes. The purpose is to provide a switch.

A first heat exchanger according to the present invention comprises: a plurality of flat tubes to be stacked; a fin provided to the flat tube; and a header to be erected in the stacking direction to be stacked and to be connected to the flat tubes. A heat exchanger, comprising: a heat exchange element that functions as an evaporator that exchanges heat between the refrigerant flowing into the flat tube through the header and the air and evaporates the refrigerant, and the heat exchange element including the flat tube, fins, and the header The rear row is the header of 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 arranged including the front row located upstream of the air flow and the rear row located downstream of the air flow The flow passage cross-sectional area in the front row header is smaller than the flow passage cross-sectional area in the rear row header so as to be greater 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 part is provided which extends in the stacking direction and partitions at least one of the front row header and the rear row header, and the channel cross-sectional area is set by the partition.

In the first heat exchanger of the present invention, the width in the air flow direction of the flat tubes in the rear row is preferably wider than the width in the air flow direction of the flat tubes in the front row.

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

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

A second heat exchanger according to the present invention includes a plurality of flat tubes to be stacked, fins provided to the flat tubes, and a header that is erected in the stacking direction to be stacked and connected to the flat tubes. A heat exchanger, comprising: a heat exchange element that functions as an evaporator that exchanges heat between the refrigerant flowing into the flat tube through the header and the air and evaporates the refrigerant, and the heat exchange element including the flat tube, fins, and the header The rear row is the header of 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 arranged including the front row located upstream of the air flow and the rear row located downstream of the air flow The apparatus is characterized by comprising a flow rate adjustment unit that adjusts the flow rate of the refrigerant introduced into at least one of the front row header and the rear row header so as to be higher than the flow rate of the refrigerant flowing through the header.

A third heat exchanger according to the present invention comprises a plurality of flat tubes to be stacked, fins provided on the flat tubes, and a header that is erected in the stacking direction to be stacked and connected to the flat tubes. A heat exchanger, comprising: a heat exchange element that functions as an evaporator that exchanges heat between the refrigerant flowing into the flat tube through the header and the air and evaporates the refrigerant, and the heat exchange element including the flat tube, fins, and the header The position of the introduction section which is arranged including the front row located upstream of the air flow and the rear row located downstream of the air flow, and which introduces the refrigerant into the section inherent to the header of the front row, and the rear row The heat exchange elements in the front row and the heat exchange elements in the rear row are arranged shifted in the stacking direction so that the position of the introduction portion for introducing the refrigerant into the section inherent to the header is different in the stacking direction It features.

The third heat exchanger of the present invention preferably comprises two heat exchange elements stacked in the stacking direction in the front row and two heat exchange elements stacked 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 rear row. It is possible to avoid the decrease in heat exchange performance due to the uneven distribution of refrigerant even without the refrigerant distribution, and switch to the defrost operation while leaving the heat exchange capacity at least on the lower side of the rear row even in the operating condition where frost formation occurs. You can delay the time until

It is a perspective view which shows the heat exchanger concerning a 1st embodiment typically. It is a schematic diagram for demonstrating the difference in the flow velocity of the refrigerant | coolant which flows through the front row | line header shown in FIG. 1, and a back row | line header. (A) to (c) are graphs showing distribution states of the liquid phase refrigerant to the respective flat tubes in the front and rear rows for each degree of the refrigerant flow rate. It is a schematic diagram for demonstrating the effect | action of the heat exchanger shown in FIG. It is a schematic diagram which shows the front row | line | column header which concerns on the modification of 1st Embodiment, and a back row | line header. It is a schematic diagram which shows the heat exchange element of the front row which concerns on the other modification of 1st Embodiment, and the heat exchange element of a rear row. (A) is a schematic diagram which shows the heat exchanger which concerns on 2nd Embodiment. (B) is a schematic diagram which shows the heat exchanger which concerns on the modification of 2nd Embodiment. (C) And (d) is a figure which shows liquid phase refrigerant distribution in, when dryness is high. (A) is a schematic diagram which shows the heat exchanger which concerns on 3rd Embodiment. (B) is a schematic diagram which shows the modification of 3rd Embodiment. Each of (a) and (b) is a schematic view showing a heat exchanger according to a fourth embodiment. The illustration of the fins is omitted.

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 rear row heat exchange element 20. The heat exchanger 1 constitutes a refrigerant circuit such as an air conditioner, a refrigerator, or a water heater. The refrigerant circuit includes a compressor, a condenser, a pressure reducing unit, and the heat exchanger 1 which is an evaporator.

According to the heat exchanger 1 of the present embodiment, as described later, the deterioration of the heat exchange performance is suppressed while accepting the uneven distribution of the refrigerant from the

headers

13 and 23 to the flat tubes 11 and the uneven distribution of frost. Do.

(Heat exchange element)
The front row heat exchange element 10 includes a plurality of flat tubes 11 (tubes) to be stacked, a plurality of fins 12, and a pair of front row headers 13 (13 A and 13 B) connected to the flat tubes 11.
The front row heat exchange element 10 is provided between the refrigerant flowing into the flat tubes 11 through the front row header 13 (13A) and the air flowing into the gap between the fins 12 and the flat tubes 11 from the direction orthogonal to the flat tubes 11. , Heat exchange.

Similar to the front row heat exchange element 10, the rear row heat exchange element 20 includes a plurality of flat tubes 11 to be stacked, a plurality of fins 12, and a pair of rear row headers 23 (23A, 23B) connected to the flat tubes 11. And heat exchange 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 are components common to the front row heat exchange element 10 and the rear row heat exchange element 20.

Here, the direction in which the flat tubes 11 are stacked (stacking direction) is referred to as the vertical direction D1.
Further, in the flow of air heat-exchanged with the refrigerant flowing through the flat tube 11, the upstream side is referred to as "front", and the downstream side is referred to as "rear". It is preferable that air taken in by a fan or the like (not shown) be supplied to the entire area of the heat exchanger 1.
The front row heat exchange element 10 and the rear row heat exchange element 20 are arranged in the air flow direction (indicated by an open arrow). In each figure, the front row is indicated by "F" and the rear row by "R".

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

The heat exchanger 1 is provided with

heat exchange elements

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

heat exchange elements

10 and 20.

(Flat tube)
The flat tube 11 is a flat tube in which the refrigerant flows inside, and linearly extends at a predetermined length. Both ends of the flat tube 11 are respectively connected to the header 13 (or the header 23). The

header

13, 23 is formed with an insertion hole (not shown) for receiving the end of the flat tube 11 into the inside of the

header

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 inside of the header 13 (or the header 23).

(fin)
The fins 12 of this embodiment have a substantially rectangular plate-like (plate-like) outer shape, and are provided on the flat tube 11 in order to expand 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 respectively inserted. The shapes of the fins 12 in the front row F and the fins 12 in the rear row R may be different.

In FIG. 1, both the front row F and the rear row R show only some of the fins 12. In fact, in any of the front row F and the rear row R, a large number of fins 12 are provided in the laminate of the flat tubes 11 at intervals in the longitudinal direction of the flat tubes 11.

Instead of the plate-like fins 12, other types of fins can be provided on the flat tube 11. For example, a corrugated corrugated fin can be provided between the flat tubes 11 adjacent in the vertical direction D1.

The members such as the flat tube 11, the fins 12, the front row header 13, and the rear 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 components using a bonding material such as a brazing material.

(Previous column header)
Each of the pair of front row headers 13 is erected in the stacking direction (D1) of the flat tubes 11 of the front row F. The flat tubes 11 of the front row F are connected to these front row headers 13.
The pair of front row headers 13 are each formed in a tubular shape, and the upper end and the lower end are closed.
The refrigerant flows into each flat tube 11 through one (13A) of the pair of front row headers 13, and the refrigerant flows out from each flat tube 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 inside of the front row header 13 from refrigerant piping 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 portion 131 flows upward.
As long as the introduction portion 131 is located below the flat tube 11 disposed at the lowermost position in the front row header 13A, any flat tubes 11 in the front row F including the lowermost flat tube 11 It is preferable because the gas-phase refrigerant floating from the introduction portion 131 and the liquid refrigerant lifted with the gas-phase refrigerant can be made to flow.

The refrigerant introduced into the inside of the front row header 13A is distributed and flows into the flat tubes 11 of the front row F. Then, while the refrigerant flows through the respective flat tubes 11 (the arrow of the broken line in FIG. 1), the air passing through the gap (air path) between the fins 12 and the flat tubes 11 and the refrigerant inside the flat tube 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 the flat tubes 11 merges inside the front row header 13B, and flows out from the front row header 13B to a refrigerant pipe or the like outside the heat exchanger 1. Alternatively, when the heat exchanger 1 includes another heat exchange element connected to the front row header 13B, the refrigerant flows out from the front row header 13B to the other heat exchange element.

(Back column header)
The rear row header 23 is configured in the same manner as the front row header 13 except that the front row header 13 and the flow passage cross-sectional area are different, and therefore will be briefly described.
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 of the flat tubes 11 of the rear row R to the other (23B) of the pair of rear row headers 23. Do.

The rear 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 rear row header 23.
The refrigerant introduced into the inside of the rear row header 23A through the introduction portion 231 is distributed to the flat tubes 11 of the rear row R and flows in. The refrigerant having flowed through the flat tubes 11 in the rear row R is heat-exchanged with the air passing through the front row F, and then joins inside the rear row header 23B, and the refrigerant piping outside the heat exchanger 1 from the rear row header 23B or , To other heat exchange elements.

The heat exchanger 1 is basically used by arranging the front row header 13 and the rear row header 23 along the vertical direction D1 (vertical direction). At this time, the flat tube 11 extends in the horizontal direction and is 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 features of this embodiment)
In the present embodiment, the flow passage cross-sectional area Af (FIG. 2) in the front row header 13 is in the rear row header 23 so that the flow velocity of the refrigerant flowing in the front row header 13 becomes higher than the flow velocity of the refrigerant flowing in the rear row header 23. It is mainly characterized in that it is smaller than the channel cross-sectional area Ar (FIG. 2).

The front row header 13 and the rear row header 23 of the present embodiment each have a flow passage having 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 shape of the front row header 13 and the rear row header 23 may be any suitable shape such as a rectangular shape or an elliptical shape.

As shown in FIG. 5, by installing the

vertical partitions

14 and 24 inside the front row header 13 and the rear row header 23, it is also possible to set appropriate channel 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 sheet of FIG. 5 and divides 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 into the section 141 from the introduction section 131 flows into the section 142 through the opening 14A penetrating the lower end portion of the vertical partition plate 14 in the thickness direction, and flows in the section 142 upward while each flat tube 11 To be distributed.

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

The vertical partition plate 14, so that the dimension G2 of the gap between the vertical partition plate 24 and the end of the flat tube 11 is larger than the dimension G1 of the gap between the vertical partition plate 14 and the flat tube 11, When the position 24 is set, a flow passage cross-sectional area Ar larger than the flow passage cross-sectional area Af of the section 142 of the front row header 13 can be given to the section 242 of the rear row header 23.

(Operation according to the present embodiment)
As shown in FIG. 2, the refrigerant having flowed from the piping of the refrigerant circuit into the inside of the front row header 13A through the introduction portion 131 at a predetermined flow rate has a flow velocity Vf corresponding to the flow passage sectional area Af of the front row header 13A. It distributes to each flat tube 11 of front row, flowing toward the inside of the above.

On the other hand, the refrigerant flowing from the refrigerant circuit piping into the rear row header 23A 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 corresponds to the flow passage cross-sectional area Ar of the rear row header 23A. It distributes to each flat tube 11 of a back row, flowing toward the inside of back row header 23A upwards at the flow velocity Vr which carries out.

Here, the flow rates of the refrigerant flowing into the front row header 13 through the introduction portion 131 and the refrigerant flowing into the rear row header 23 through the introduction portion 231 are the same, and the flow passage 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 velocity Vf, Vr.

The refrigerant of the gas-liquid two-phase flow expanded by passing through the pressure reducing portion of the refrigerant circuit flows into the front row header 13A and the rear row header 23A. The gas phase of the refrigerant is referred to as gas phase refrigerant, and the liquid phase is referred to as liquid phase refrigerant. The liquid phase refrigerant is entrained in the floating gas phase refrigerant and carried upward. Since the density of the liquid phase refrigerant is larger 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 uneven in each of the front row header 13A and the rear row header 23A.
The distribution of the gas phase refrigerant and the liquid phase refrigerant is different between the front row header 13A and the rear row header 23A based on the difference between the flow rates Vf and Vr.

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

On the other hand, in the rear row header 23A having a small flow velocity Vr, the liquid phase refrigerant is less likely to be carried upward as compared to the front row header 13A, so the range where the liquid phase refrigerant is sufficiently carried from the introduction portion 231 is the flow path of the rear row header 23A. Stay at the bottom.
Therefore, contrary to the above-described front row header 13A, the ratio of liquid phase refrigerant to gas phase refrigerant is high at the lower portion of the flow path of rear row header 23A, and the ratio of liquid phase refrigerant to gas phase refrigerant at the upper portion of the flow path Is low.

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

FIG. 3 shows the front row F and the rear row R based on the experimental results in the cases where the flow rate of the refrigerant introduced into the heat exchanger 1 is small (a), medium (b) and large (c). The flow rate ratio (flow rate ratio to the gas phase refrigerant) of the liquid phase refrigerant in the refrigerant which has flowed into each of the flat tubes 11 of each is shown. The

numbers

1, 2, 3,... Are sequentially given downward from the flat tube 11 located at the top of each of the front row header 13A and the rear row header 23A. In the experiments for obtaining the data in FIGS. 3 (a) to 3 (c), a front row heat exchange element and a rear row heat exchange element provided with seven flat tubes 11 were used.

In any of FIGS. 3A to 3C, in the front row F, the ratio of the liquid phase refrigerant flowing in is higher as the flat tube 11 is positioned higher, and conversely, in the rear row R, the flat tube 11 is downward. The same tendency as the above-mentioned shows that the ratio of the liquid phase refrigerant which flows in is so high that it is located.
As shown in FIGS. 3A to 3C, 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 as the refrigerant flow rate increases. Also, conversely, the degree of deviation of the flow rate ratio of the liquid phase refrigerant in the vertical direction D1 of the rear row R decreases as the flow rate of the refrigerant increases. This tendency holds qualitatively because the flow passage cross-sectional area of the front row header 13 is smaller than the flow passage cross-sectional area of the rear row header 23.

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

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

The operation of the present embodiment will be described with reference to FIGS. 4 and 2. According to the present embodiment, as each of the front row F and the rear row R, even if there is a bias in the liquid phase flow rate ratio of the refrigerant distributed to each flat tube 11, the heat transfer amount of the heat exchanger 1 as a whole Achieve uniformity, and secure necessary heat exchange performance even when there are restrictions on the heat exchanger capacity.

In the front row header 13 (FIG. 2) where the flow velocity is high, the liquid phase refrigerant is carried sufficiently upward, so the flow ratio of the liquid phase refrigerant in the flat tubes 11 of the front row F to which the refrigerant is distributed from the front row header 13 is While the amount of heat transfer between the refrigerant flowing through the large upper-side flat tube 11 and the air is large, the amount of heat transfer at the lower portion is small.
On the other hand, in the rear 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 transported to the upper side so much, the flat tube 11 of the rear row R to which the refrigerant is distributed from the rear row header 23 While the amount of heat transfer between the refrigerant flowing through the lower flat tube 11 having a large flow ratio of the liquid phase refrigerant and the air is large, the amount of heat transfer at the upper portion is small.

The air flowing along the arrow 1 shown in FIG. 4 passes through the lower side where the heat transfer amount of the front row F is small and the lower side where the heat transfer amount of the rear row R is large. Here, even if the air passing 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 tubes 11 on the lower side of the rear row R flowing following the front row F There is a flow of liquid-phase refrigerant in an amount sufficient to dissipate the air sufficiently.

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

From the above, the heat transfer surface is effectively utilized while avoiding the heat transfer loss over the entire heat exchanger 1 in which the upper and lower sides of the front row F and the upper and lower sides of the rear row R are combined. Even if the exchanger 1 is small, sufficient heat exchange performance can be ensured. As described above, by providing the flow velocity difference to the front row header 13 and the rear row header 23 as in the present embodiment, it is possible to balance the amount of heat transfer in the vertical direction D1 as a whole of the front row F and the rear row R. By doing so, a decrease in heat exchange performance due to uneven distribution of the refrigerant can be avoided, and 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 is avoided, the manufacturing cost of the heat exchanger 1 can be suppressed.

Contrary to the present embodiment, even if the flow passage cross-sectional area is set to Af> Ar so that the flow velocity Vf of the front row header 13 becomes smaller than the flow velocity Vr of the rear row header 23, the refrigerant distribution is uneven From the viewpoint of avoiding the performance degradation, the same effect as that of the present embodiment can be obtained.

Furthermore, in addition to the performance reduction due to the uneven distribution of the refrigerant, the present embodiment also copes with the performance reduction due to frost formation. In the heat exchanger 1 used for the outdoor heat exchanger of the air conditioner, frost formation proceeds from the front row F where the temperature difference with the contacting air is larger than the rear row R when the temperature of the outside air which is the heat source is low during heating operation. Do. Alternatively, frost may occur on the heat exchanger 1 used to cool the heat load, such as a refrigerator / freezer showcase or the like and an internal heat exchanger such as a refrigerator / freezer, etc. Also in this case, the front row F Frost formation progresses from.

From the viewpoint of avoiding the performance decrease 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 becomes larger than the flow velocity Vr of the rear row header 23 as in the present embodiment. It is good to identify. Then, in the present embodiment in which the same flow rate of refrigerant is introduced to the front row F and the rear row R, the channel cross-sectional area is specified as Af <Ar.

Among the front row F where frost formation tends to occur, the air on the upper side with a large liquid phase flow rate is sufficiently cooled by the refrigerant having a large liquid phase flow rate, so it is easy to form frost. The lower side is hard to frost. That is, the same bias of frost formation as the bias (for example, FIG.3 (c)) of the liquid phase flow rate ratio of front row F in the up-down direction D1 is seen.

Here, as shown in FIG. 3C, the frost formation on the upper row side of the front row F having a large liquid phase flow rate proceeds, and the air passage is blocked by the frost, so the air volume on the upper row side of the rear row R decreases. I assume. However, at this time, since frost formation has not progressed so much on the lower side of the front row F, the air volume can be maintained at least on the lower side of the rear row R, which is downwind on the lower side of the front row F.
That is, even after the heat exchange capacity on the upper row side is lost including the rear row R due to frost formation, air is sent to the rear row R on the lower row side, and the heat transfer on the lower row side on the rear row R where the frost is not attached Since the heat exchange capacity is left by the surface, the time until switching to the defrosting operation is extended.
According to the present embodiment, by suppressing heat transfer loss due to frost formation, heating operation and the like can be continued without interruption of heating operation and the like due to the defrosting operation.

FIG. 6 shows an example in which a width Dr larger than the width Df of the flat tube 11 of the front row F is given to the flat tube 11 inserted into the rear row header 23 having a larger diameter than the front row header 13. In order to improve the heat transfer area, it is preferable to secure a large width Dr of the flat tube 11 in the air flow direction to the same extent as the diameter of the rear row header 23. By expanding the width Dr of the flat tubes 11 in the rear row R, the capacity of the heat exchanger 1 can be improved without changing the space required for the installation of the heat exchanger 1.
Note that, instead of expanding 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.
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.

FIG. 7A schematically shows the

heat exchange elements

10 and 20, but the

heat exchange elements

10 and 20 are configured in the same manner as the first embodiment (FIG. 1).
That is, the front row heat exchange element 10 is provided with the flat tube 11, the fins 12, and the front row header 13 as shown in FIG. 1. The rear row heat exchange element 20 also comprises a flat tube 11, fins 12 and a rear row header 23. Since the flow passage cross-sectional area Af of the front row header 13 is smaller than the flow passage cross-sectional area Ar of the rear row header 23, 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.
As in the first embodiment, the heat transfer amount in the vertical direction D1 is achieved as a whole in the front row F and the rear row R based on the flow velocity difference, and the time until switching to the defrosting operation at the time of frost formation is delayed. it can.

The rear heat exchange element 20 corresponds to the most upstream first pass P1. The front row heat exchange element 10 corresponds to a second pass P2 following the first pass P1. Here, the second path P2 is the most downstream path.
While the refrigerant flows 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 piping (not shown) to the rear row header 23A (FIG. 1) of the first path P1, the refrigerant is distributed from the rear row header 23A to the flat tubes 11 of the rear row R. The refrigerant flowing through the flat tubes 11 merges inside the rear row header 23B (FIG. 1), and flows into the second path P2 of the front row F through the U-shaped tube 17. Then, the refrigerant is distributed from the inside of the front row header 13B (FIG. 1) of the second pass P2 to the flat tubes 11 of the front row F, and the refrigerant flowing through those flat tubes 11 is the front row header 13A (FIG. 1) Flow out to the refrigerant piping.

Here, when the refrigerant absorbs heat from the air and the dryness increases, the absolute amount of the liquid phase flow rate ratio decreases, so in particular, the liquid phase refrigerant to the flat tube 11 on the upper side facing the inside of the header of the most downstream path P2. It is difficult to make
7 (c) and 7 (d) show the distribution of the liquid phase refrigerant in the case where the dryness of the refrigerant is high based on the experiment, but in (c) and (d), the flow path of the header Cross section is different. FIG. 7 (c) shows the case where the flow passage cross section of the header has a typical size (for example, Am in FIG. 8), and FIG. 7 (d) shows the flow passage cross section of the header is typical. The case where it is smaller than the size is shown. 7C and 7D, since the flow rate of the refrigerant is the same, the flow velocity in the header is larger when the flow passage cross-sectional area is smaller (FIG. 7D). Therefore, in FIG. 7 (d), the liquid-phase refrigerant reaches the flat tube 11 above as compared to FIG. 7 (c) having a relatively low flow velocity.

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

Modification of Second Embodiment
As shown in FIG. 7 (b), when the heat exchanger 2A includes three or more paths connected in series, the fourth path P4 on the most downstream side in the front row is the same as in FIG. 7 (a). It is preferable to arrange in the front row F as well as arrange in the front row F while arranging in the F.
The second pass P2 and the third pass P3 are arranged in the rear row R.

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

Although FIG. 7 (b) also schematically shows the

heat exchange elements

10 and 20, the

heat exchange elements

10 and 20 are configured in the same manner as the first embodiment (FIG. 1).
Based on the flow velocity difference between the front row header 13 and the rear row header 23, as in the first embodiment, the heat transfer amount is 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.

In the configuration shown in FIG. 7 (b), when the refrigerant is introduced into the header 13A (FIG. 1) of the first path P1, the refrigerant is distributed from the front row header 13A to the flat tubes 11 of the front row F. The refrigerants flowing through the flat tubes 11 join together in the front row header 13B (FIG. 1), and flow into the second path P2 of the rear row R through the U-shaped tube 181. Then, the refrigerant is distributed to the flat tubes 11 from the rear row header 23B of the second pass P2, and the refrigerant flowing through the flat tubes 11 passes from the rear row header 23A through the U-shaped tube 182 to the upper row side. It flows into the back row header 23A of the third pass P3. Furthermore, it flows through the flat pipe 11 of the third pass P3 and flows into the front row header 13B of the fourth path P4 through the U-shaped pipe 183. 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. 7B, as in the second embodiment shown in FIG. 7A, the most downstream path P4 where the dryness is the highest is arranged in the front row F. The heat transfer surface of the downstream path P4 can also be sufficiently utilized to contribute to the performance.
In addition to that, 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 having a relatively small refrigerant pressure loss, especially the header 13A at the inlet of the path P1 is small. As a result, it is possible to suppress the rise of the evaporation temperature caused by the refrigerant pressure loss. By suppressing the rise of the evaporation temperature, it is possible to avoid the deterioration of the evaporation performance.

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

The distributor 15, which includes capillary tubes and the like, flows 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 diverted at a predetermined flow ratio.
Then, the front row header 13 is provided with the flow velocity Vf corresponding to the flow rate Rf and the flow passage cross sectional area Am, and the rear row header 23 is provided with the flow velocity Rr and the flow velocity Vr corresponding to the flow passage cross sectional area Am.
In the present embodiment, since the flow passage cross-sectional area Am of the front row header 13 and the flow passage cross-sectional area Am of the rear row header 23 are equal, Rf / Rr = Vf / Vr.

According to the present embodiment, by providing the distributor 15, even if the flow passage cross sectional areas of the front row header 13 and the rear row header 23 are equal, the flow velocity difference of the refrigerant is given to the front row header 13 and the rear row header 23. The effect similar to 1st Embodiment can be obtained based on the distribution in the up-down direction D1 of the liquid phase flow rate ratio by the difference in a flow velocity.
In addition, by using the same header having the same diameter, it is possible to prevent the assembly error of the front row heat exchange element 10 and the rear row heat exchange element 20 at the time of manufacturing the heat exchanger 3.

Instead of the distributor 15, as shown in FIG. 8B, a throttle 16 (flow rate adjusting unit) can be used. Among the pipes branched from the refrigerant piping (not shown) at the same flow rate, the throttle 16 is provided on one side introduced into the rear row header 23. Since the pressure loss is given to the refrigerant directed to the rear row header 23 by the throttle 16, the flow rate Rr of the refrigerant introduced to the rear row header 23 is smaller than the flow rate Rf of the refrigerant introduced to the front row header 13.

Fourth Embodiment
Next, a fourth embodiment of the present invention will be described with reference to FIG.
FIGS. 9A and 9B show the heat exchanger 4 of the same configuration. FIGS. 9 (a) and 9 (b) differ only in the image of the distribution of the liquid phase refrigerant.
The heat exchanger 4 according to the fourth embodiment includes two heat exchange elements 10 stacked in the vertical direction D1 in the front row F and two heat exchange elements 20 stacked in the vertical direction D1 in the rear row R. .
In this heat exchanger 4, the front row heat exchange element 10 and the rear row heat exchange element 20 are disposed in such a manner that the front row heat exchange element 10 and the rear row heat exchange element 20 are shifted in the vertical direction D1. The height from the lower end to the upper end is equal.
Further, the front row heat exchange element 10 and the rear row heat exchange element 20 are connected in parallel or in series to the piping of the refrigerant circuit, and the refrigerant having the same flow rate flows through the front row heat exchange element 10 and the rear row heat exchange element 20.

The heat exchanger 4 includes a front row heat exchange element 10 and a rear row heat exchange element 20 configured in the same manner as the first embodiment. However, unlike the first embodiment, the flow passage cross-sectional areas of the front row header 13 and the rear row header 23 are equal.

By shifting the front row heat exchange element 10 and the rear row heat exchange element 20 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 rear row header 23 It differs in the direction D1.

When the flow rate of the refrigerant is small or the dryness is high, as shown by the gray arrows along the vertical direction D1 in FIG. 9A, the image of the distribution of the liquid phase refrigerant is in the

headers

13 and 23. The flow rates of the liquid phase refrigerant flowing into each are slow. Therefore, the liquid-phase refrigerant is likely to flow into the flat tubes 11 on the lower side of the

headers

13 and 23, that is, on the lower side.
On the other hand, when the flow rate of the refrigerant is high or the dryness is low, as shown by the gray arrows along the vertical direction D1 of the liquid phase refrigerant distribution image in FIG. The flow rates are all fast. Therefore, the liquid-phase refrigerant is likely to flow into the upper portions of the

headers

13 and 23, ie, the flat tubes 11 on the upper side.

As a result, 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 can be delayed at the time of frost formation. .
In addition, by using the same headers having the same diameter, it is possible to prevent the assembly error of the front row heat exchange element 10 and the rear 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 rear row header 23 may be divided into a plurality of sections, and an introduction unit for introducing a refrigerant into each section may be prepared. Also 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 shifting the front row heat exchange element 10 and the rear row heat exchange element 20 in the vertical direction D1, Similar effects can be obtained.

In addition to the above, the configurations described in the above embodiment can be selected or changed to other configurations as appropriate without departing from the spirit of the present invention.
For example, the heat exchanger of the present invention may include, in addition to the front row F and the rear row R, one or more middle rows located between the front row F and the rear row R.

In each of the above-described 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 element of the present invention comprises two rows, that is, two flat tube elements aligned in the air flow direction, and these flat tube elements are configured to be connected to the same header May be

1 to 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 portion)
14A Opening 15 Distributor (Flow Adjustment Unit)
16 Throttle (Flow control part)
17 U-shaped tube 20 rear row

heat exchange element

23, 23A, 23B rear row header 24 vertical partition plate (partition portion)
24A Opening 121 Notch 131 Introduction portion 141 Section 142

Section

181, 182, 183 U-shaped tube 231 Introduction section 241 Section 242 Section Af, Ar, Am Channel cross-sectional area D1 Vertical direction Df, Dr Width F Front row G Dimension G2 Dimension P1- P4 path R back row Rf, Rr flow Vf, Vr flow

Claims

A heat exchanger comprising: a plurality of flat tubes to be stacked; a fin provided to the flat tube; and a header rising in a stacking direction in which the flat tubes are stacked and connected to the flat tubes, ,
It functions as an evaporator that exchanges heat between the refrigerant flowing into the flat tube through the header and the air, and evaporates the refrigerant.
Heat exchange elements comprising the flat tubes, the fins and the header are arranged including a front row located upstream of the air flow and a rear row located downstream of the air flow;
The flow rate of the refrigerant flowing through the front row header, which is the header of the front row, is greater than the flow rate of the refrigerant that flows through the rear row header, which is the rear row header.
The flow passage cross-sectional area in the front row header is smaller than the flow passage cross-sectional area in the rear row header,
A heat exchanger characterized by
A partition portion extending in the stacking direction to partition at least one of the front row header and the rear row header;
The flow passage cross-sectional area is set by the partition unit,
The heat exchanger according to claim 1.
The width of the flat tubes in the rear row in the flow direction of the air is:
The width of the flat tubes in the front row in the flow direction of the air is wider than
The heat exchanger according to claim 1 or 2.
Comprising two or more of said 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.
Comprising three or more of said 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 flat tubes to be stacked; a fin provided to the flat tube; and a header rising in a stacking direction in which the flat tubes are stacked and connected to the flat tubes, ,
It functions as an evaporator that exchanges heat between the refrigerant flowing into the flat tube through the header and the air, and evaporates the refrigerant.
Heat exchange elements comprising the flat tubes, the fins and the header are arranged including a front row located upstream of the air flow and a rear row located downstream of the air flow;
The flow rate of the refrigerant flowing through the front row header, which is the header of the front row, is greater than the flow rate of the refrigerant that flows through the rear row header, which is the rear row header.
A flow rate adjusting unit configured to adjust a flow rate of the refrigerant introduced to at least one of the front row header and the rear row header;
A heat exchanger characterized by
A heat exchanger comprising: a plurality of flat tubes to be stacked; a fin provided to the flat tube; and a header rising in a stacking direction in which the flat tubes are stacked and connected to the flat tubes, ,
It functions as an evaporator that exchanges heat between the refrigerant flowing into the flat tube through the header and the air, and evaporates the refrigerant.
Heat exchange elements comprising the flat tubes, the fins and the header are 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 inherent to the header of the front row and the position of the introduction portion for introducing the refrigerant into the section inherent to the header of the rear row are different in the stacking direction ,
The heat exchange elements in the front row and the heat exchange elements in the rear row are disposed shifted in the stacking direction,
A heat exchanger characterized by
Two of the heat exchange elements stacked in the stacking direction in the front row;
The two heat exchange elements stacked in the stacking direction in the rear row;
The heat exchanger according to claim 7.