JP7684588B2 - heat exchanger - Google Patents

Description

The present invention relates to a heat exchanger used in a heat transfer medium circuit.

Heat exchangers are known that are used in various industrial fields such as refrigeration and air conditioning to exchange heat between a heat medium circulating in a heat medium circuit and an external fluid. Such heat exchangers are installed as equipment that constitutes part of the heat medium circuit through which the heat medium circulates, and are used to heat the external fluid by passing a high-temperature, high-pressure heat medium compressed by a compressor through a heat exchanger in a condenser or gas cooler, or to cool the external fluid by passing a low-temperature, low-pressure heat medium decompressed by an expansion valve through a heat exchanger in an evaporator.

In heat exchange between the heat medium passing through such a heat exchanger and an external fluid, the thermal energy must pass not only through the inner walls of the pipes of the heat medium flow path that constitute the heat medium circulation path, but also through the temperature boundary layer or viscous sublayer. The faster the flow speed, the thinner the temperature boundary layer and viscous sublayer become, so it is essential to keep the flow speed of the heat medium flowing through the heat medium flow path at a specified speed or higher.

For example, the heat exchanger shown in Patent Document 1 is configured by connecting a header connected to the upstream side of a heat medium circulation path and a header connected to the downstream side by multiple heat medium pipes arranged in parallel. The cross-sectional area of the heat medium pipes is designed to keep the flow rate of the heat medium flowing through the heat medium pipes at a predetermined value or higher. This allows each heat medium pipe to efficiently exchange heat with an external fluid.

JP 2004-317056 A (page 2, figure 2)

In this way, in a heat exchanger such as that described in Patent Document 1, the heat medium that flows into the upstream header is distributed by multiple heat medium pipes, improving the heat exchange efficiency of the heat medium per given mass that flows into the header.

However, when the volume of the heat medium passing through the heat exchanger changes in response to temperature changes caused by heat exchange with an external fluid, the flow rate through the pipes also changes. Therefore, if the cross-sectional area of the heat medium piping is designed to match the flow rate upstream of the heat exchanger, the heat exchange efficiency downstream will decrease, and vice versa. This meant that there was room for further improvement.

The present invention was developed to address these problems, and aims to provide a heat exchanger with high heat exchange efficiency.

In order to solve the above problems, the heat exchanger of the present invention comprises:
A heat exchanger having a heat medium flow path that constitutes a heat medium circulation path,
The heat transfer medium passage is characterized in that one of the upstream and downstream cross-sectional areas is larger than the other.
According to this feature, the flow cross-sectional area is changed in accordance with the change in volume of the heat medium passing through the heat exchanger, so that the flow rate of the heat medium can be maintained at a certain level or higher, thereby improving the heat exchange efficiency.

The heat medium passage includes a first passage and a plurality of branch passages branched from the first passage.
According to this feature, the total value of the cross-sectional areas of the branched flow paths can be made larger than the cross-sectional area of one flow path, making it possible to easily configure a heat transfer medium flow path in which one of the cross-sectional areas on the upstream side and the downstream side is larger than the other.

The one flow path is characterized in that there is one.
According to this feature, the heat transfer medium can be divided or merged approximately evenly.

The one flow path and the multiple branch flow paths are characterized in that they are arranged in the same row among the rows of the heat medium flow paths that are arranged in a direction in which an external fluid that exchanges heat with the heat exchanger passes through.
According to this feature, the heat transfer medium can be divided or merged in a location where a sudden temperature change is unlikely to occur.

The one flow path is disposed between the two branch flow paths and is connected in a T-shape or a Y-shape.
According to this feature, the branch flow paths are unlikely to affect each other.

One of the upstream and downstream cross-sectional areas is characterized in that it is twice as large as the other.
According to this feature, excessive changes in flow velocity can be suppressed.

The heat exchanger is characterized by cooling carbon dioxide, which is a heat medium.
According to this feature, the cross-sectional area of the flow can be reduced according to the volume of carbon dioxide, which decreases significantly with a decrease in temperature. This makes it possible to increase the flow rate of the carbon dioxide, the volume of which decreases with a decrease in temperature, and thereby increase the heat transfer coefficient.

The heat exchanger is characterized by cooling carbon dioxide in a supercritical state, which is a heat medium.
According to this feature, the cross-sectional area of the carbon dioxide flow can be reduced in accordance with the volume of the carbon dioxide, which decreases significantly with a decrease in temperature while maintaining the supercritical state, thereby increasing the flow rate of the carbon dioxide in the supercritical state and increasing the heat transfer coefficient.

1 is a schematic diagram showing a heat medium circulation path to which a heat exchanger according to a first embodiment of the present invention is applied; 1 is a schematic diagram showing a gas cooler to which a heat exchanger according to a first embodiment of the present invention is applied. 1 is a schematic diagram showing a heat exchanger according to a first embodiment of the present invention. 1 is a diagram showing a main part of a heat exchanger according to a first embodiment of the present invention; 1 is a cutaway view showing a main part of a heat exchanger according to a first embodiment of the present invention. FIG. 6 is a cutaway view showing a main part of a heat exchanger according to a second embodiment of the present invention.

The following describes how to implement the heat exchanger according to the present invention.

The heat exchanger according to the first embodiment will be described with reference to Figs. 1 to 5. In the following description, in addition to the up, down, left and right directions shown in Fig. 2, the front side of the page will be referred to as the front direction, and the back side of the page will be referred to as the rear direction.

As shown in FIG. 1, the heat exchanger 10 of this embodiment is applied to a gas cooler 3 that constitutes part of a refrigeration cycle 1 as a heat transfer medium circulation path.

The refrigeration cycle 1 is used in industrial refrigeration machines and is mainly composed of a compressor 2, a gas cooler 3, an expansion valve 4, an evaporator 5, and a heat medium pipe 8 that connects these and circulates a heat medium inside. In this embodiment, carbon dioxide is circulated as the heat medium. As shown by the solid arrows in Figure 1, carbon dioxide in a supercritical state compressed by the compressor 2 during operation passes through the heat medium pipe 8 in the order of the gas cooler 3, the expansion valve 4, and the evaporator 5, and is circulated by being pumped out again by the compressor 2.

As shown in FIG. 2, the gas cooler 3 is mainly composed of a housing 6, a fan 7 provided on the upper part of the housing 6, and a pair of heat exchangers 10, 10, and is disposed outdoors as a so-called outdoor unit. The pair of heat exchangers 10, 10 are disposed facing each other in a roughly V-shape, inclined away from each other from below to above.

When the fan 7 is driven, as shown by the white arrow in Figure 2, outside air as an external fluid is sucked in through the opening 6a on the side of the housing 6 and discharged from the exhaust port 6b at the top of the housing 6. This allows outside air to be sucked in from two directions and passed through the pair of heat exchangers 10, 10, making it possible for the gas cooler 3 to cool a large amount of heat transfer medium at once.

Returning to FIG. 1, each heat exchanger 10 is mainly composed of multiple fins 11 and a main heat transfer medium pipe 12.

The multiple fins 11 are arranged side by side in a direction approximately perpendicular to the direction in which the outside air passes, with their surface direction aligned with the direction in which the outside air passes.

The main heat transfer medium line 12 is connected in communication with the heat transfer medium pipe 8 downstream of the compressor 2 and the heat transfer medium pipe 8 upstream of the expansion valve 4.

As shown in FIG. 3, the main heat medium pipe 12 is mainly composed of an upstream header 13, a downstream header 14, and eight sets of heat medium pipes 15 as heat medium flow paths.

The upstream header 13 is connected to the heat transfer pipe 8 downstream of the compressor 2.

The downstream header 14 is connected to the heat transfer pipe 8 upstream of the expansion valve 4.

Each of the eight units U1 to U8 has one heat medium pipe 15, which is connected to the headers 13 and 14. As a result, the flow path from the upstream header 13 to the downstream header 14 is branched into eight paths. Note that FIG. 3 is a schematic diagram of the heat exchanger 10 shown on the right side of FIG. 2.

As shown in unit U1 in FIG. 3, one set of heat transfer medium pipelines 15 is composed of two upstream connecting pipes 16, 16', straight pipes 17, 17', 18, 18', 19, 19', 20-37, multiple curved pipes 38, one connecting pipe 39, and one downstream connecting pipe 40.

The upstream connecting pipes 16, 16' are connected to the upstream header 13.

The straight tubes 17 to 37 extend linearly and penetrate each fin 11 in a direction perpendicular to its surface.

The curved pipe 38 connects the longitudinal ends of two adjacent straight pipes.

The connecting pipe 39 connects the longitudinal ends of the three straight pipes 19, 19', and 20.

The downstream connecting pipe 40 is connected to the downstream header 14.

Each of the tubes 16-40 is made of a metal with high thermal conductivity such as copper or aluminum, and each of the tubes 16-40 has a substantially circular cross section, and the cross-sectional area S (see FIG. 5) of each of the tubes 16-40 is substantially the same. The relative positions of the tubes 16-40 will be described below.

The two upstream connecting pipes 16, 16' shown by solid lines in Figure 3 have their upstream ends welded to the upstream header 13 and their downstream ends welded to the forward end of one of the straight pipes 17, 17'.

The straight pipes 17 to 37 are arranged approximately parallel to each other, and are arranged in six vertical rows, with four rows in each row. In more detail, in the order in which the heat transfer medium flows from the upstream header 13 side to the downstream header 14 side, there are the first row in which the straight pipes 17, 17', 18, 18' are arranged, the second row in which the straight pipes 19, 19', 20, 21 are arranged, the third row in which the straight pipes 22, 23, 24, 25 are arranged, the fourth row in which the straight pipes 26, 27, 28, 29 are arranged, the fifth row in which the straight pipes 30, 31, 32, 33 are arranged, and the sixth row in which the straight pipes 34, 35, 36, 37 are arranged, and the odd-numbered rows and even-numbered rows are arranged in a staggered pattern.

In FIG. 3, the curved pipe 38 connects the downstream end of the upstream straight pipe with the upstream end of the downstream straight pipe, and is formed in a roughly U-shape. The curved pipe 38 shown by the solid line is welded to the front end of each straight pipe, and the curved pipe 38 shown by the dashed line is welded to the rear end of each straight pipe.

The connecting pipe 39 shown by the dashed line in FIG. 3 is arranged along the second row in which the straight pipes 19, 19', 20, and 21 are arranged, and is welded and fixed to the rear ends of the straight pipes 19, 19', and 20.

As shown in FIG. 4, the connecting pipe 39 connects the downstream ends 19a, 19a' of the upstream straight pipes 19, 19' to the upstream end 20a of the downstream straight pipe 20, and is formed in a rounded, approximately E-shape.

The connecting pipe 39 has connecting ends 39a, 39a' that are connected to the ends 19a, 19a' of the straight pipes 19, 19' and extend linearly, curved sections 39b, 39b' that extend in a quarter-circle arc shape continuing from the connecting ends 39a, 39a', straight sections 39c that extend linearly continuing from the curved sections 39b, 39b', and an orthogonal section 39d that extends approximately parallel to the connecting ends 39a, 39a' and perpendicular to the axial center of the straight section 39c. The cross-sectional area S (see FIG. 5) of each of the above-mentioned parts of the connecting pipe 39 is approximately the same. As shown in FIG. 4 and FIG. 5, the straight pipes 19, 19', 20 and the connecting pipe 39 are welded to each other at the welded section W.

Returning to FIG. 3, the downstream connecting pipe 40 shown by the dashed line has its upstream end welded to the rear end of the straight pipe 37, and its downstream end welded to the downstream header 14.

Next, we will explain the flow of the heat medium in the heat medium pipe 15. In this explanation, we will omit the description of each curved pipe 38 to make the flow order of the heat medium easier to understand.

As shown in FIG. 3, the heat medium pumped from the compressor 2 and flowing into the header 13 is distributed to a total of 16 upstream connecting pipes 16, 16', ... in the heat medium pipes 15 of each of the eight sets of units U1 to U8. That is, in one set of heat medium pipes 15, the heat medium flows from the two upstream connecting pipes 16, 16' into the straight pipes 17, 17'. Since the flow of the heat medium in the heat medium pipes 15 of each of the units U1 to U8 is the same, the flow of the heat medium in the heat medium pipes 15 of unit U1 will be described below.

As shown in Figures 3 to 5, the heat transfer medium that flows into the straight pipe 17 passes through the straight pipes 18 and 19 and flows into the connecting pipe 39. Similarly, the heat transfer medium that flows into the straight pipe 17' passes through the straight pipes 18' and 19' and flows into the connecting pipe 39. From the connecting pipe 39, the heat transfer medium flows into the straight pipe 20, passes through the subsequent pipes 21 to 37 and 40, and flows into the downstream header 14.

As described above, each of the tubes 20-37, 40 is a flow path of the present invention, and each of the tubes 16-19 and each of the tubes 16'-19' is a branch flow path of the present invention. Hereinafter, they will be simply referred to as a single flow path 20-37, 40, and may also be referred to as two branch flow paths 16-19, 16'-19'.

In this way, by configuring two branch flow paths 16-19, 16'-19' to merge into one flow path 20-37, 40, the total 2S (2S = S + S) of the flow cross-sectional area S of the branch flow paths 16-19 located upstream and the flow cross-sectional area S of the branch flow paths 16'-19' located downstream can be made twice the flow cross-sectional area S of one flow path 20-37, 40 located downstream. In other words, it is possible to easily configure a heat medium pipe 15 in which the total 2S of the flow cross-sectional area on the upstream side is larger than the flow cross-sectional area S on the downstream side.

Next, we will explain in detail how the flow of the heat transfer medium changes when it merges from the two branch flow paths 16-19, 16'-19' into one flow path 20-37, 40.

First, the heat transfer medium flowing through the branch flow paths 16-19 flows from the straight pipe 19 to the connecting pipe 39 at the connection end 39a and into the curved section 39b (see FIG. 5). Similarly, the heat transfer medium flowing through the branch flow paths 16-19' flows from the straight pipe 19' to the connecting pipe 39 at the connection end 39a' and into the curved section 39b' (see FIG. 5).

As shown by the thin arrows in FIG. 5, the heat medium that flows into the connecting pipe 39 flows from the curved portion 39b to the straight portion 39c. Similarly, the heat medium that flows into the curved portion 39b' also flows from the curved portion 39b' to the straight portion 39c.

Here, the axial length of each of the tubes 16-19 is approximately the same as the axial length of each of the tubes 16'-19'. Also, as described above, the cross-sectional area S (see FIG. 5) of each of the tubes 16-19 is approximately the same as the cross-sectional area S of each of the tubes 16'-19'.

Furthermore, the straight pipes 17, 18 and the straight pipes 17', 18' are arranged in the same first row, and the straight pipes 19, 19', 20, 21 and the connecting pipe 39 are arranged in the same second row. As shown by the white arrows in Figure 3, as the outside air passes through the heat exchanger 10 from the sixth row to the first row, it exchanges heat with the heat medium in the straight pipes of each row in sequence.

Therefore, the temperature of the outside air passing around the straight pipes 19, 19', 20, and 21 and the connecting pipe 39, which are in the same row, is approximately the same. Also, the temperature of the outside air passing around the straight pipes 17 and 18 and the straight pipes 17' and 18', which are in the same row, is approximately the same.

As a result, the volume of the heat medium flowing from curved section 39b to straight section 39c for a given weight is approximately the same as the volume of the heat medium flowing from curved section 39b' to straight section 39c for a given weight, and the flow rate of the heat medium flowing from curved section 39b to straight section 39c is approximately the same as the flow rate of the heat medium flowing from curved section 39b to straight section 39c and the flow rate of the heat medium flowing from curved section 39b' to straight section 39c.

These heat transfer media flow from the opposing directions in the straight line section 39c toward the axial center of the straight line section 39c where the perpendicular section 39d is connected, join together, and flow into the perpendicular section 39d.

As a result, the cross-sectional area of the region through which the heat transfer medium flows is changed from the sum of the cross-sectional area S of the straight section 39c on the curved section 39b side and the cross-sectional area S of the straight section 39c on the curved section 39b' side, 2S, to the cross-sectional area S of the perpendicular section 39d. In other words, the cross-sectional area is reduced by half (2S → S).

As a result, the flow rate of the heat medium flowing from the straight section 39c to the perpendicular section 39d can be increased compared to the flow rate of the heat medium flowing from each curved section 39b, 39b' to the straight section 39c.

Here, when the flow-down cross-sectional area is reduced by half, the flow rate of the heat medium passing through the perpendicular section 39d is theoretically twice as fast as the flow rate of the heat medium passing through the curved section 39b and the curved section 39b'. However, since a slight pressure loss occurs in the actual flow of the heat medium inside the pipe as described below, the flow rate of the heat medium passing through the perpendicular section 39d is an appropriate flow rate that is slightly more than twice as fast as the flow rate of the heat medium passing through the curved section 39b and the curved section 39b'.

More specifically, the straight pipe 20, which is one flow path, is disposed between the straight pipes 19 and 19', which are branch flow paths, and is connected in a T-shape by the straight portion 39c and the perpendicular portion 39d of the connecting pipe 39.

As a result, the heat transfer medium flowing in from the branch flow paths 16-19 and the heat transfer medium flowing in from the branch flow paths 16'-19' move from both axial ends of the straight section 39c toward the center and collide, i.e., a head-on collision occurs at the axial center of the straight section 39c, causing a pressure loss.

As a result, the flow rate of the heat medium increases slightly just before it flows into the perpendicular section 39d. As a result, compared to when the heat medium passes through the curved section 39b or 39b', the cross-sectional area of the area through which the heat medium flows is reduced to half, but the flow rate of the heat medium becomes an appropriate flow rate that is slightly more than twice as fast.

In addition, as described above, the flow rate of the heat medium flowing through the branch flow paths 16-19 is approximately the same as the flow rate of the heat medium flowing through the branch flow paths 16'-19', so compared to a case where the flow rate of the heat medium in the branch flow paths 16-19 is higher than the flow rate of the heat medium in the branch flow paths 16'-19', for example, it is easier to cause a head-on collision near the axis of the perpendicular portion 39d in the straight portion 39c.

As a result, it is difficult for the heat medium in one of the two branch flow paths 16-19, 16'-19' to flow into the other flow path, or for the heat medium in one flow path to flow preferentially into the orthogonal portion 39d over the heat medium in the other flow path, making it easier for the heat medium to flow approximately evenly from the two branch flow paths 16-19, 16'-19' into one flow path 20-37, 40. In other words, the two branch flow paths 16-19, 16'-19' are less likely to affect each other.

The volume of the heat medium flowing from the straight pipe 19 into the straight section 39c for a given weight is smaller than the volume of the heat medium flowing from the upstream connecting pipe 16 for a given weight due to heat exchange with the outside air. This is also true for the heat medium flowing from the straight pipe 19' into the straight section 39c'. In other words, the flow velocity of the heat medium flowing downstream of the branch flow paths 16-19 and the flow velocity of the heat medium flowing downstream of the branch flow paths 16'-19' are both reduced.

The cross-sectional area S of the heat transfer medium is changed and the flow rate is increased in response to the change in the volume of the heat transfer medium passing through the branch flow paths 16-19 or the branch flow paths 16'-19', so the flow rate of the heat transfer medium can be maintained at a constant level that is faster than a predetermined flow rate. This allows the heat exchanger 10 to increase its heat exchange efficiency.

In addition, as described above, the total value 2S of the flow cross-sectional area S on the upstream side is twice the flow cross-sectional area S on the downstream side, so excessive changes in flow velocity can be suppressed.

In addition, as described above, the temperature of the outside air passing around the straight pipes 19, 19', 20, and 21 arranged in the same row and the connecting pipe 39 is approximately the same, so the heat transfer medium can be merged in a place where sudden temperature changes are unlikely to occur.

For example, in a configuration in which the heat medium is merged at straight pipe 25 arranged in a different row from straight pipes 19, 19', the heat medium is cooled by the colder outside air because it is upstream in the direction of the outside air flow. If a sudden temperature change occurs while the heat medium flow is already disturbed by the merging, there is a risk that the heat medium flow will be further disturbed. In contrast, the heat medium pipe 15 of this embodiment makes it easier to stabilize the flow of the merged heat medium.

Furthermore, the heat transfer medium that is joined at the connecting pipe 39 passes through two straight pipes 20 and 21 arranged in the same row and flows into the straight pipe 22 in the adjacent row, so the flow is more likely to be stabilized before a change in the temperature of the outside air occurs.

As described above, the heat exchanger 10 of this embodiment can maintain the flow rate of the heat medium at a constant level or higher, so that the thickness of the temperature boundary layer and the viscous bottom layer can be made sufficiently thin from the upstream to downstream sides of the heat medium pipe 15. This improves the heat exchange efficiency.

In addition, since there is only one flow path 20-37, 40, the heat medium can be merged approximately evenly.

In addition, the straight pipes 20 in each of the flow paths 20-37, 40 are disposed between the straight pipes 19 in the branch flow paths 16-19 and the straight pipes 19' in the branch flow paths 16'-19', so that the distance between the straight pipes 19 and 20 and the distance between the straight pipes 19' and 20 can be made approximately equal and short.

In addition, in the heat exchanger 10, the heat medium that flows into the upstream header 13 is distributed to the heat medium pipes 15 of each of the eight sets of units U1 to U8, and heat exchange occurs in each set of units U1 to U8. This means that the surface area of the area where heat exchange occurs is increased, improving the heat exchange efficiency of the heat medium per given mass that flows into the header 13.

The heat exchanger 10 cools the carbon dioxide in a supercritical state, which is the heat transfer medium, and can reduce the cross-sectional area of the flow in accordance with the volume of the carbon dioxide, which decreases significantly as the temperature decreases while maintaining the supercritical state. This makes it possible to increase the flow rate of the carbon dioxide, whose volume has decreased as the temperature has decreased, and to increase the heat transfer coefficient, compared to a heat exchanger with a constant cross-sectional area of the flow.

In addition, since the heat medium in this embodiment is in a supercritical state, it is prevented from liquefying when passing through the heat exchanger 10. This prevents the heat medium from stagnating even if the heat medium pipe 15 is configured to move back and forth multiple times in the vertical direction. Therefore, it is possible to ensure the axial length of the heat medium pipe 15, and the heat medium efficiency can be improved.

The heat medium in this embodiment is in a supercritical state, and no change in state, i.e., no phase change, occurs when passing through the heat exchanger 10, so it is easy to merge the heat medium in the same row. In this embodiment, it is preferable to design the piping so that multiple branch flow paths merge into one flow path at an appropriate location, such as the middle part of the piping length region where a supercritical state can occur.

Even when using a heat medium that undergoes a phase change, it is preferable to design the piping so that multiple branch flow paths merge into one flow path at an appropriate location, such as the middle part of the piping length region where the phase change of the heat medium can occur. For this reason, it is preferable to design the piping so that multiple branch flow paths merge into one flow path at an appropriate location, such as the middle part of the piping length region where an extremely large volume change, such as a supercritical state or phase change, can occur. Therefore, if they are arranged in the same row, multiple branch flow paths may be merged into one flow path in an appropriate row, taking into account the volume change of the heat medium.

In addition, in this embodiment, a configuration in which one flow path branches into two branch flow paths has been described, but this is not limited to this, and the number of flow paths and the number of branch flow paths may be changed as appropriate depending on the volume change.

Next, the heat exchanger according to the second embodiment will be described with reference to FIG. 6. Note that the description of the same configuration as the first embodiment will be omitted.

The heat exchanger of this embodiment 2 is applied to an evaporator 5 (see FIG. 1) that is provided in the middle of a cold air circulation path that communicates with the inside of a freezer and circulates cold air. The heat exchanger of this embodiment has the same configuration as the heat exchanger 10 (see FIG. 3) of the first embodiment, but differs in that the flow direction of the heat medium is reversed from the flow direction of the outside air, as shown in FIG. 6, although not shown directly.

As a result, in the heat transfer medium pipe 115 of this embodiment, the heat transfer medium flows from one flow path 40, 37-20 (see FIG. 3) into the orthogonal portion 39d of the connecting pipe 39, and is then diverted into two branch flow paths 19-16, 19'-16' (see FIG. 3).

As a result, the cross-sectional area of the region through which the heat transfer medium flows is changed from the cross-sectional area S at the orthogonal section 39d to the sum of the cross-sectional area S at the curved section 39b side of the straight section 39c and the cross-sectional area S at the curved section 39b' side of the straight section 39c, 2S. In other words, the cross-sectional area is doubled (S → 2S).

As a result, the flow rate of the heat medium flowing from the orthogonal portion 39d to the curved portion 39b or curved portion 39b' side of the straight portion 39c can be reduced compared to the flow rate of the heat medium flowing from one of the flow paths 40, 37-20 to the orthogonal portion 39d.

In addition, since one flow path 40, 37-20 is connected to the two branch flow paths 19-16, 19'-16' in a T-shape by the orthogonal portion 39d and the straight portion 39c of the connecting pipe 39, the heat medium that flows from the orthogonal portion 39d to the straight portion 39c collides with the pipe inner wall 39e of the straight portion 39c, which is approximately perpendicular to the axis of the orthogonal portion 39d. This causes a pressure loss.

In addition, the axial length and flow cross-sectional area of the branch flow paths 19-16, i.e., the volume within the flow path, and the volume of the branch flow paths 19'-16' are approximately the same, so the pressure acting toward the branch flow paths 19-16 near the axis of the perpendicular portion 39d in the straight portion 39c can be made approximately the same as the pressure acting toward the branch flow paths 19'-16'.

As a result, the heat medium is less likely to flow biasedly into one of the two branch flow paths 19-16, 19'-16' from the vicinity of the axis of the orthogonal portion 39d in the straight portion 39c, making it easier to divert the heat medium from one flow path 40, 37-20 to the two branch flow paths 19-16, 19'-16' approximately evenly. In other words, the two branch flow paths 19-16, 19'-16' are less likely to affect each other.

However, the volume of the heat medium flowing from one flow path 40, 37-20 into the cross section 39d for a given weight is larger than the volume of the heat medium for a given weight in the upstream connecting pipe 40 due to heat exchange with the cold air. In other words, the flow rate of the heat medium in one flow path 40, 37-20 is increasing.

In this way, the cross-sectional area S of the flow passage is changed according to the change in the volume of the heat medium passing through one of the flow paths 40, 37-20, so that the flow rate of the heat medium is maintained at a certain level or higher, while the total surface area of each of the tubes 39-16 downstream of the orthogonal portion 39d is increased, thereby improving the heat exchange efficiency.

In addition, since there is only one flow path 20-37, 40, the heat medium can be divided approximately evenly.

In addition, as mentioned above, the temperature of the cold air passing around the straight pipes 19, 19', 20, and 21 arranged in the same row and the connecting pipe 39 is approximately the same, so the heat transfer medium can be diverted in a place where sudden temperature changes are unlikely to occur.

The heat exchanger 10 mainly evaporates the heat transfer medium, carbon dioxide, and can increase the cross-sectional area of the flow in accordance with the volume that increases significantly with evaporation. This makes it possible to increase the heat exchange efficiency while keeping the flow rate of carbon dioxide at a constant level or higher, compared to a heat exchanger with a constant cross-sectional area of the flow.

Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention also includes modifications and additions that do not deviate from the gist of the present invention.

For example, in the first and second embodiments, the heat transfer medium circuit is described as a refrigeration cycle applied to a refrigerator, but it is not limited to this and may be a heat pump applied to an air conditioner, or may be modified as appropriate.

In addition, in the above-mentioned Examples 1 and 2, the heat medium is described as being carbon dioxide, but this is not limited thereto and may be changed to any known heat medium as appropriate.

In addition, in the above-mentioned Examples 1 and 2, the external fluid is described as being outside air or cold air, but it is not limited to this and may be other gases or liquids such as water, and may be changed as appropriate.

In addition, in the first and second embodiments, the heat exchanger is described as being of a so-called plate type having fins, but this is not limited thereto, and it may be of a fin tube type, or may be modified as appropriate.

In addition, in the above-mentioned first and second embodiments, the heat transfer medium flow path is described as being composed of eight sets of units that can merge or split the flow of the heat transfer medium, but this is not limited thereto, and one or more sets may be used.

In addition, in the above-mentioned first and second embodiments, the heat transfer medium flow path is described as having two branch pipes connected to one pipe, thereby changing the area on the upstream side and the area on the downstream side. However, this is not limited to this, and the flow path with a large flow cross-sectional area may be connected to a flow path with a small flow cross-sectional area, thereby changing the flow cross-sectional area.

In addition, in the above-mentioned first and second embodiments, the heat transfer medium flow path is described as having two branch pipes connected to one pipe, but this is not limited thereto, and three or more branch pipes may be connected to one pipe. Also, two or more branch pipes may be connected to one pipe, which is more than one pipe.

In addition, in the above-mentioned first and second embodiments, the heat transfer medium flow path is described as being configured so that the cross-sectional area of the flow path is changed only once in each unit, but this is not limited thereto, and the cross-sectional area of the flow path may be changed multiple times.

In addition, in the above-mentioned Examples 1 and 2, the heat transfer medium flow path is described as having two branch pipes connected in a T-shape to one pipe, but this is not limited thereto, and may be, for example, a Y-shape. With such a configuration, when the heat transfer mediums join together as in Example 1, for example, the heat transfer mediums avoid head-on collision with each other, and collide at an angle to each other, thereby suppressing pressure loss.

In addition, in the above-mentioned Examples 1 and 2, the heat transfer medium flow paths are described as merging or splitting in the second row, but this is not limited thereto, and as long as they are arranged in the same row, they may be arranged in an appropriate row taking into consideration appropriate locations such as the middle part in the piping length region where a large volume change of the heat transfer medium may occur.

In addition, in the above-mentioned Examples 1 and 2, the pipes constituting the heat transfer medium passage are described as having the same cross-sectional area, but more specifically, it is sufficient that the average cross-sectional area is the same. Specifically, as described above, the pipes are not limited to a configuration having a single cross-sectional area and a flat continuous inner circumferential surface, but may have a shape in which the inner circumferential surface has some unevenness in the axial direction. In other words, as long as the average cross-sectional area is the same, the cross-sectional shape of the heat transfer medium passage may be changed as appropriate.

In addition, in the above-mentioned first and second embodiments, the straight pipes are described as being arranged in six vertical rows with four columns in each row, but this is not limited thereto, and the arrangement of the straight pipes may be changed as appropriate.

In addition, in the above-mentioned first and second embodiments, the heat transfer medium flow path is described as being connected to a header on its upstream side, but this is not limited thereto, and it may be a distributor, or may be modified as appropriate.

1 Refrigeration cycle (heat medium circulation path)
2 Compressor 3 Gas cooler 4 Expansion valve 5 Evaporator 10 Heat exchanger 11 Fin 12 Heat medium main pipe 15 Heat medium pipe (heat medium flow path)
16-19 Straight pipe (branch flow path)
16' to 19' Straight pipe (branch flow path)
20-37, 40 Straight pipe (one flow path)
39 Connecting pipe 39a, 39a' Connection end 39b, 39b' Curved portion 39c Straight portion 39d Orthogonal portion 115 Heat medium pipe S Flow cross-sectional area 2S Total value of flow cross-sectional areas U1 to U8 Unit

Claims (4)

A heat exchanger including a heat medium flow path constituting a heat medium circulation path, the heat medium in the heat medium flow path being switchable between being heated and being cooled by heat exchange with an external fluid,
The heat medium flow path includes a first flow path and two branch flow paths branched from the first flow path, and a total value of the flow-down cross-sectional area of the two branch flow paths is larger than the flow-down cross-sectional area of the first flow path,
the first flow path is disposed between the two branch flow paths, and each end of the first flow path and the two branch flow paths is connected to a connecting pipe by welding, the first flow path and the two branch flow paths are disposed in the same row among the rows of the heat medium flow paths disposed in a direction in which an external fluid that exchanges heat with the heat exchanger passes,
When the heat medium in the heat medium flow path is heated by heat exchange with an external fluid, the heat medium is divided by the connecting pipe and flows downward from the one flow path on the upstream side toward the two branch flow paths on the downstream side disposed on both sides of the one flow path,
and when the heat medium in the heat medium flow path is cooled by heat exchange with an external fluid, the heat medium flows from the two upstream branch flow paths to join together at the connecting pipe and flow down toward the one downstream flow path disposed between the two branch flow paths. The heat exchanger according to claim 1, characterized in that the total cross-sectional area of the two branch passages is twice the cross-sectional area of the first passage. 3. The heat exchanger according to claim 1 , wherein the heat exchanger cools carbon dioxide, which is a heat medium. 4. The heat exchanger according to claim 1 , wherein the heat exchanger cools carbon dioxide in a supercritical state, which is a heat medium.

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