HEAT EXCHANGER

TECHNICAL FIELD

The present disclosure relates to a heat exchanger.

BACKGROUND ART

A condenser includes multiple tubes stacked with each other. Refrigerant is flowing through the tubes. Air is flowing through gaps between adjacent ones of the tubes. Inner fins are housed inside the tubes.

SUMMARY

A heat exchanger according to one aspect of the present disclosure has multiple tubes stacked with each other and is configured to perform heat exchange between a first fluid flowing inside of the tubes and a second fluid flowing around the tubes. The heat exchanger includes multiple fins each housed in a respective one of the tubes. Each of the fins includes a connecting portion and a non-connecting portion. The connecting portion is formed by corrugating the each of the plurality of fins for a predetermined fin pitch to have a peak that is joined to an inner surface of a wall of each of the plurality of tubes. The non-connecting portion has a length longer than the predetermined fin pitch. The non-connecting portion is not joined to the inner surface of the wall of the each of the tubes. The wall of the each of the tubes includes a protrusion to face the non-connecting portion.

Further, a heat exchanger according to another aspect of the present disclosure has multiple tubes stacked with each other and is configured to perform heat exchange between a first fluid flowing inside the tubes and a second fluid flowing around the tubes. The heat exchanger includes multiple fins each housed in a respective one of the tubes. Each of the fins includes a connecting portion and a non-connecting portion. The connecting portion is formed by corrugating the each of the fins for a predetermined fin pitch to have a peak that is joined to an inner surface of a wall of each of the tubes. The non-connecting portion has a length longer than the predetermined fin pitch. The non-connecting portion is not joined to the inner surface of the wall of the each of the tubes. The non-connecting portion includes a protrusion.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view showing a front structure of a heat exchanger of a first embodiment.

FIG. 2 is a cross-sectional view showing a cross-sectional structure taken along a line II-II of FIG. 1.

FIG. 3 is a cross-sectional view showing a cross-sectional structure of a tube of the first embodiment.

FIG. 4 is a perspective view showing a cross-sectional perspective structure of the tube of the first embodiment.

FIG. 5 is a graph showing a relationship between the Reynolds number Re of a cooling water and heat transfer coefficient α.

FIG. 6 is a cross-sectional view showing a cross-sectional structure of a tube of a first modification of the first embodiment.

FIG. 7 is a perspective view showing a cross-sectional perspective structure of a tube of the first modification of the first embodiment.

FIG. 8 is a cross-sectional view showing a cross-sectional structure of a tube of a second embodiment.

FIG. 9 is a cross-sectional view showing a cross-sectional structure of a tube of a first modification of the second embodiment.

FIG. 10 is a cross-sectional view showing a cross-sectional structure of a tube of the first modification of the second embodiment.

FIG. 11 is a perspective view showing a cross-sectional perspective structure of a tube of a second modification of the second embodiment.

FIG. 12 (A) is a cross-sectional view showing a cross-sectional structure around a protrusion of the tube of the second modification of the second embodiment.

FIG. 12 (B) is a cross-sectional view showing a cross-sectional structure around a protrusion in the tube of the second modification of the second embodiment.

FIG. 13 is a schematic diagram showing a flow mode of cooling water in the tube of the heat exchanger of the second modification of the second embodiment.

FIG. 14 is a perspective view showing a cross-sectional perspective structure of a tube of a third modification of the second embodiment.

FIG. 15 (A) is a cross-sectional view showing a cross-sectional structure around a protrusion of the tube of the third modification of the second embodiment.

FIG. 15 (B) is a cross-sectional view showing a cross-sectional structure around a protrusion of the tube of the third modification of the second embodiment.

FIG. 16 is a perspective view showing a cross-sectional perspective structure of a tube of a fourth modification of the second embodiment.

FIG. 17 (A) is a cross-sectional view showing a cross-sectional structure around a protrusion of the tube of the fourth modification of the second embodiment.

FIG. 17 (B) is a cross-sectional view showing a cross-sectional structure around a protrusion of the tube of the fourth modification of the second embodiment.

FIG. 18 is a cross-sectional view showing a cross-sectional structure of a tube of another embodiment.

FIG. 19 is a cross-sectional view showing a cross-sectional structure of a tube of another embodiment.

DESCRIPTION OF EMBODIMENT

To begin with, examples of relevant techniques will be described.

A condenser includes multiple tubes stacked with each other. Refrigerant is flowing through the tubes. Air is flowing through gaps between adjacent ones of the tubes. In this condenser, heat exchange is performed between the refrigerant flowing through the tubes and the air flowing around the tubes, so that the refrigerant is condensed. Inner fins are housed inside the tubes. Each of the inner fins is a so-called corrugated fin formed by bending a thin metal plate into a wavy shape. The inner fins have a function of promoting heat exchange between the refrigerant and air by increasing a heat transfer area for the refrigerant.

The structure in which the inner fins are provided inside the tubes is not limited to the condenser, but is effective for a radiator configured to cool a cooling water by releasing heat of the cooling water to air. However, when the structure in which inner fins are provided inside the tubes is adopted for the radiator, there are the following concerns.

In recent years, a vehicle traveling with an electric motor as a power source is sometimes equipped with a radiator for cooling a cooling water circulating through a battery configured to supply power to the electric motor and its peripheral devices, in addition to the radiator for cooling the engine cooling water. Such a radiator is sometimes referred to as a low water temperature radiator because cooling water having a temperature lower than that of the engine cooling water flows through the radiator. In the low water temperature radiator, a flow rate of the cooling water supplied from an electric pump may be less than that of the radiator for engine cooling water. As a result, a flow of the cooling water inside the tubes has a tendency to become the low Re (Reynolds) number flow and heat transfer coefficient of the cooling water may decrease. Therefore, if inner fins are provided inside the tubes, the heat transfer area for the cooling water can be increased, so that the heat transfer coefficient of the cooling water can be improved.

In contrast, when the inner fins are provided inside the tubes, the inner fins serve as obstacles to the flow of the cooling water, so that water flow resistance of the cooling water increases. Further, when the low water temperature radiator is mounted in the vehicle, it may be necessary to reduce the number of stacking stages of the tubes of the low water temperature radiator due to the relationship between space limitation of the vehicle and heat generation amount of the low water temperature radiator. As the number of stacking stages of the tubes decreases, the flow velocity of the cooling water in the tubes increases, so that the water flow resistance of the cooling water further increases. When the water flow resistance of the cooling water increases, it becomes difficult for the cooling water to flow through the tubes, so that the heat transfer coefficient of the low water temperature radiator may decrease. This is one of the factors that the heat transfer coefficient of the low water temperature radiator cannot be improved even if the inner fins are provided inside the tubes.

It should be noted that such an issue is not limited to the low water temperature radiator, but is an issue common to heat exchangers that exchange heat between the fluid flowing inside the tubes and the fluid flowing around the tubes.

It is an object of the present disclosure to provide a heat exchanger capable of both decreasing water flow resistance and improving heat transfer coefficient.

According to this configuration, since the non-connecting portions of the fins are not in contact with the inner surfaces of the tubes, a cross-sectional area of a passage through which the first fluid flows can be secured. Therefore, it is possible to reduce the water flow resistance. Further, since the protrusion formed on the tube increases the heat transfer area of the tube for the first fluid, the heat transfer coefficient of the heat exchanger can be improved.

According to this configuration, since the non-connecting portions of the fins are not in contact with the inner surfaces of the tubes, a cross-sectional area of a passage through which the first fluid flows can be secured. Therefore, it is possible to reduce the water flow resistance. Further, since the protrusion is formed on the non-connecting portion, heat transfer area of the fin for the first fluid is increased and heat transfer coefficient of the heat exchanger can be improved.

According to this configuration, since the non-connecting portions of the fins are not in contact with the inner surfaces of the tubes, a cross-sectional area of a passage through which the first fluid flows can be secured. Therefore, it is possible to reduce the water flow resistance. Further, since the protrusions formed on the tubes and the protrusions formed on the non-connecting portions of the fins increase the heat transfer area of the tubes and fins for the first fluid, the heat transfer coefficient of the heat exchanger can be improved.

Hereinafter, an embodiment of a heat exchanger will be described with reference to the drawings. To facilitate understanding, identical constituent elements are designated with identical symbols in the drawings where possible with the duplicate description omitted.

First Embodiment

First, a heat exchanger 10 of a first embodiment shown in FIG. 1 will be described. The heat exchanger 10 shown in FIG. 1 is mounted on a vehicle equipped with an internal combustion engine and an electric motor as a driving power source. Through the heat exchanger 10, an engine cooling water for cooling the internal combustion engine and a cooling water for cooling the electric motor and its peripheral devices circulate. Since the cooling water for cooling the electric motor and its peripheral devices has a temperature lower than that of the engine cooling water, it will be hereinafter referred to as “a low temperature cooling water”. The heat exchanger 10 is a complex radiator that is configured to cool both the engine cooling water and the low temperature cooling water through a heat exchange between the engine cooling water and air and heat exchange between the low temperature cooling water and air. In the present embodiment, the engine cooling water and the low temperature cooling water correspond to a first fluid, and the air corresponds to a second fluid. Hereinafter, the engine cooling water and the low temperature cooling water are collectively referred to as “a cooling water”. The heat exchanger 10 is arranged in an engine compartment together with a condenser and an evaporator of a vehicular air conditioner. For example, in case of a combination with the evaporator of the vehicular air conditioner, the heat exchanger 10 is arranged at a position closer to a grill opening than the condenser of the vehicular air conditioner is. Air introduced through the grill opening is supplied to the heat exchanger 10.

As shown in FIG. 1, the heat exchanger 10 includes a core portion 20, a first header tank 30, and a second header tank 40.

The core portion 20 includes multiple tubes 21 and multiple outer fins 22.

The multiple tubes 21 are stacked at predetermined intervals in a direction indicated by an arrow Z. The tubes 21 extend in a direction indicated by an arrow X. A cross-sectional shape of each of the tubes 21 perpendicular to the direction shown by the arrow X has a flat tubular shape. The tubes 21 define therein passages extending in the direction show by the arrow X and the cooling water flows through the passages. Air flows through gaps between adjacent ones of the tubes 21 in a direction indicated by an arrow Y.

Hereinafter, the direction indicated by the arrow X is referred to as “a tube longitudinal direction X”, the direction indicated by the arrow Y is referred to as “an airflow direction Y”, and the direction indicated by the arrow Z is referred to as “a tube stacking direction Z”. In the present embodiment, the tube stacking direction Z is a vertical direction, and the tube longitudinal direction X and the airflow direction Y are horizontal directions. Therefore, the heat exchanger 10 of the present embodiment is a so-called cross-flow heat exchanger.

The outer fins 22 are arranged in the gaps between the adjacent ones of the tubes 21. Each of the outer fins 22 are a so-called corrugated fin formed by bending a thin metal plate made of aluminum or the like into a wavy shape. Peaks of bending portions of each of the outer fin 22 are in contact with and brazed to outer surfaces of the adjacent ones of the tubes 21. The outer fins 22 are fixed to the tubes 21 by this joint structure. The outer fins 22 have a function of promoting heat exchange between the refrigerant flowing inside the tubes 21 and the air flowing through the gaps between the adjacent ones of the tubes 21 by increasing a heat transfer area for the air.

The first header tank 30 is connected to one end of each of the tubes 21. The first header tank 30 is formed into a tubular shape. The first header tank 30 includes therein a partition 33 that partitions an internal space of the first header tank 30 into a first distribution passage 31 and a second distribution passage 32. The first header tank 30 defines a first inlet 310 at a portion defining the first distribution passage 31 and a second inlet 320 at a portion defining the second distribution passage 32.

The second header tank 40 is connected to the other end of each of the tubes 21. The second header tank 40 is formed into a tubular shape like the first header tank 30. The second header tank 40 defines therein a partition 43 that partitions the inner space into a first merging passage 41 and a second merging passage 42. The partition 43 of the second header tank 40 is arranged at the same position as the position of the partition 33 of the first header tank 30 in the tube stacking direction Z. The second header tank 40 defines a first outlet 410 at a portion defining the first merging passage 41 and a second outlet 420 at a portion defining the second merging passage 42.

In the following, a region of the core portion 20 connected to the first distribution passage 31 of the first header tank 30 and the first merging passage 41 of the second header tank 40 will be referred to as a first core region A1. Similarly, a region of the core portion 20 connected to the second distribution passage 32 of the first header tank 30 and the second merging passage 42 of the second header tank 40 will be referred to as a second core region A2. As shown in FIG. 1, in the heat exchanger 10 of the present embodiment, the first core region A1 is larger than the second core region A2.

In the heat exchanger 10, the engine cooling water flows into the first inlet 310 of the first header tank 30. The engine cooling water having flowed into the first inlet 310 are distributed to each of the tubes 21 in the first core region A1 of the core portion 20 from the first distribution passage 31 of the first header tank 30. In the first core region A1 of the core portion 20, the engine cooling water is cooled by heat exchange between the engine cooling water flowing inside the tubes 21 and the air flowing around the tubes 21. The engine cooling water cooled by flowing through the tubes 21 merges in the first merging passage 41 of the second header tank 40 and then flows out of the second header tank 40 through the first outlet 410.

Further, in the heat exchanger 10, the low water temperature cooling water flows into the first header tank 30 through the second inlet 320. The low water temperature cooling water having flowed into the second inlet 320 is distributed from the second distribution passage 32 of the first header tank 30 to each of the tubes 21 in the second core region A2 of the core portion 20. In the second core region A2 of the core portion 20, the low water temperature cooling water is cooled by heat exchange between the low water temperature cooling water flowing inside the tubes 21 and the air flowing around the tubes 21. The low water temperature cooling water cooled when flowing through the tubes 21 merge in the second merging passage 42 of the second header tank 40 and then flows out of the second header tank 40 through the second outlet 420.

Next, a structure of the core portion 20 will be specifically described.

As shown in FIG. 2, in the core portion 20, a stacking structure of the tubes 21 are arranged in two rows in the airflow direction Y. The core portion 20 is not limited to a structure having two rows of stacking structures of the tubes 21, and may be a structure having only one row of the stacking structure of the tubes 21.

Inner fins 23 are housed inside the tubes 21. Each of the inner fins 23 is formed by bending a thin metal plate such as aluminum.

As shown in FIGS. 3 and 4, the inner fin 23 has a deformed portion 232 at one end of the inner fin 23. The deformed portion 232 is deformed to be fixed to the tube 21. Due to the deformed portion 232, a thickness of one end of the tube 21 is increased, so that resistance of the tube 21 against stone chipping is secured.

The inner fin 23 includes connecting portions 230a, 230b, and 230c each of which is formed by bending the metal plate into a wavy shape to have a predetermined fin pitch FP. The connecting portion 230a is formed at an inner side of the deformed portion 232, the connecting portion 230b is formed at a center portion of the inner fin 23, and the connecting portion 230a is formed at the other end portion of the inner fin 23. Peaks of the connecting portions 230a to 230c are in contact with an inner surface of the tube 21. A contact portion between the peaks and the inner surface of the tube 21 are brazed to each other. The connecting portions 230a to 230c position the inner fin 23 with respect to the tube 2, secure heat transfer area to the tube 21, and secure rigidity of the tube 21.

The inner fin 23 includes non-connecting portion 231a between the connecting portion 230a and the connecting portion 230b. The non-connecting portion 231a is not joined to the inner surface of the tube 21. Similarly, the inner fin 23 includes a non-connecting portion 231b between the connecting portion 230b and the connecting portion 230c. The non-connecting portions 231a and 231b extend parallel to the inner surface of the tube 21. The non-connecting portion 231a has a length L1 and the non-connecting portion 231b has a length L2. Each of the length L1 and the length L2 is longer than the fin pitch of the connecting portions 230a to 230c.

The tube 21 includes multiple protrusions 210a and 211a protruding into the tubes 21 to face the non-connecting portions 231a and 231b. More specifically, one of an outer surface of the tube 21 facing the non-connecting portion 231a of the inner fin 23 includes multiple first protrusions 210a. The other of the outer surface of the tube 21 facing the non-connecting portion 231a of the inner fin 23 includes multiple second protrusions 211a. The first protrusions 210a are arranged at positions closer to the connecting portion 230a than the connecting portions 230b of the inner fin 23. The second protrusions 211a are arranged at positions closer to the connecting portion 230b than the connecting portions 230a of the inner fin 23. Similarly, outer wall portions 210 and 211 of the tube 21 facing the non-connecting portion 231b of the inner fin 23 includes the first protrusions 210a and the second protrusion 211a. A first space S1 is defined as a space partitioned by the connecting portions 230a and 230b of the inner fin 23, the non-connecting portion 231a, and the outer wall portions 210 and 211 of the tube 21. A second space S2 is defined as a space partitioned by the connecting portions 230b and 230c of the inner fin 23, the non-connecting portion 231b, and the outer wall portions 210 and 211 of the tubes 21. In this case, the first space S1 has substantially the same shape as the second space S2.

Next, an operation example of the heat exchanger 10 of the present embodiment will be described.

In the heat exchanger 10 of the present embodiment, the Reynolds number Re of the cooling water flowing through the tubes 21 and the heat transfer coefficient α of the cooling water change as shown by the solid line L1 in FIG. 5. In FIG. 5, as a reference example, a chain line L2 shows a relationship between the Reynolds number Re and the heat transfer coefficient α of the cooling water in case that the tubes 21 does not include the protrusions 210a and 211a and that the inner fins 23 are not disposed in the tubes 21. Further, in FIG. 5, as a reference example, a chain double dashed line L3 shows a relationship between the Reynolds number Re and the heat transfer coefficient of the cooling water in case that the tubes 21 include the protrusions 210a and 211b and that the inner fins 23 are not disposed in the tubes 21.

As shown in FIG. 5, when the value of the Reynolds number Re is small, the cooling water becomes a laminar flow. Further, when the value of the Reynolds number Re is large, the cooling water becomes a turbulent flow. When the value of the Reynolds number Re is an intermediate value between them, the flow of the cooling water is within a transition zone. The transition zone is a zone in which the flow of the cooling water is transitioned between the laminar flow and the turbulent flow

As shown by the chain double dashed line L3 in FIG. 5, in case that the tubes 21 include the protrusions 210a and 211a and the inner fins 23 are not disposed in the tubes 21, the heat transfer coefficient α of the cooling water can be secured when the cooling water in the transition flow zone or the turbulent flow zone. However, when the cooling water is in the laminar flow zone, there is a possibility that the heat transfer coefficient α of the cooling water cannot be sufficiently secured. Compared the flow rate of the engine cooling water flowing through the first core region A1, the flow rate of the low temperature cooling water flowing through the second core region A2 of the heat exchanger 10 is lower. Thus, the flow of the low-temperature cooling water flowing through the second core region A2 of the heat exchanger 10 tends to be a layer flow. Therefore, the heat transfer coefficient α may not be sufficiently secured only by forming the protrusions 210a and 211b in the tubes 21.

In this regard, in the heat exchanger 10 of the present embodiment, as shown by the solid line L1 in FIG. 5, the heat transfer coefficient α of the cooling water in the laminar flow zone can be improved compared with the reference example shown by the chain double dashed line L3. This is because, in the heat exchanger 10 of the present embodiment, the heat transfer area is increased and the heat transfer can be promoted by the inner fins 23 provided inside the tubes 21.

Further, in the heat exchanger 10 of the present embodiment, the heat transfer coefficient α of the cooling water can be improved in the transition zone as shown in the solid line L1 compared with the reference example shown by the chain double dashed line L3. This is because, in addition to the effects of the protrusions 210a and 211a themselves, the inner fins 23 can increase the heat transfer area and promote heat transfer.

According to the heat exchanger 13 of the present embodiment described above, operations and effects described in the following items (1) to (5) can be obtained.

(1) Since the non-connecting portions 231a and 231b of the inner fins 23 are not in contact with the inner surfaces of the tubes 21, cross-sectional areas of passages through which the engine cooling water and the low temperature cooling water flow can be secured. Thus, it is possible to reduce water flow resistance. Further, the protrusions 210a and 211a formed on the tubes 21 locally increase heat transfer area between the tubes 21 and the cooling water and improve the heat transfer coefficient of the heat exchanger 10 by having the cooling water around the protrusions flow turbulently.

(2) The protrusions 210a and 211a protrude into the tubes 21. According to such a configuration, it is possible to avoid interference between the protrusions 210a and 211a and the outer fins 22.

(3) The non-connecting portions 231a and 231b extend in parallel to the inner surface of the tubes 21. According to such a configuration, passages having a predetermined width can be secured between the non-connecting portion 231a and 231b of the inner fin 23 and the inner surface of the tube 21, so that a water resistance of the cooling water flowing through the tube 21 can be further reduced.

First Modification

Next, a first modification of the heat exchanger 13 of the first embodiment will be described.

As shown in FIG. 6, the tube 21 of this modification include the protrusions 210a and 211a protruding outward.

According to such a configuration, the air flowing through gaps between the adjacent ones of the tubes 21 collides with the protrusions 210a and 211a, so that the airflow direction around the tubes 21 can be changed. As a result, the air is assisted to flow into louvers formed in the outer fins 22 and the protrusions 210a and 211b can improve heat transfer performance for the air.

Second Modification

Next, a heat exchanger 13 of a second modification of the first embodiment will be described.

As shown in FIG. 7, a shape of each of protrusions 210a and 211a of this modification is not hemispherical but an elongated shape extending in a direction diagonally intersecting the flow direction of the cooling water. According to such a configuration, it is possible to minimize gaps formed between connecting surfaces of the outer fins 22 and the protrusions 210a and 211a. As a result, the connecting area between the tubes 21 and the outer fins 22 are increased and heat transfer performance can be improved for the cooling water and the air.

Second Embodiment

Next, a heat exchanger 13 of a second embodiment will be described. Hereinafter, differences from the heat exchanger 13 of the first embodiment will be mainly described.

As shown in FIG. 8, in the heat exchanger 10 of the present embodiment, each of the non-connecting portions 231a and 231b includes multiple protrusions 232a. The protrusions 232a are formed not to be in contact with the inner surface of the tube 21. An arrangement of the protrusions 232a in the non-connecting portion 231a is substantially the same as an arrangement of the protrusions 232a in the non-connecting portion 231b. As a result, when a first space 51 is defined as a space partitioned by the connecting portions 230a and 230b of the inner fin 23, the non-connecting portion 231a, and the outer wall portions 210 and 211 and a second space S2 is defined as a space partitioned by the connecting portions 230b and 230c, the non-connecting portion 231b, and the outer wall portions 210 and 211, the first space 51 has substantially the same shape as the second space S2.

According to the heat exchanger 10 of the present embodiment described above, the following advantages shown in (4) can be obtained in addition to the advantages shown in (3) above.

(4) Since the non-connecting portions 231a and 231b are not in contact with the inner surface of the tube 21, cross-sectional areas of the passages through which the engine cooling water and the low temperature cooling water flow can be secured. Therefore, it is possible to reduce the water flow resistance. Further, since the protrusions 232a formed on the inner fin 23 increase the heat transfer area of the inner fin 23 with respect to the cooling water, the heat transfer coefficient of the heat exchanger 10 can be improved. Although it is desirable that all of the protrusions 232a be not in contact with the inner surface of the tube 21, a part of the protrusions 232a may be in contact with the inner surface of the tube 21 as long as the same or similar advantages as those of the heat exchanger 10 of the present embodiment can be obtained.

First Modification

Next, a heat exchanger 13 of a first modification of the second embodiment will be described.

As shown in FIG. 9, in the heat exchanger 10 of the present modification, the inner fin 23 includes protrusions 232a which are formed by cutting and bending a part of the non-connecting portions 231a and 231b into a trapezoidal shape. The cut-up shape of the protrusions 232a is not limited to the trapezoidal shape, and may be triangular, for example, as shown in FIG. 10.

According to such a configuration, the protrusions 232a can be easily formed on the inner fin 23.

Second Modification

Next, a heat exchanger 13 of a second modification of the second embodiment will be described. In the following, as shown in FIG. 11, one direction in the tube longitudinal direction X is referred to as a X1 direction, and the other direction in the tube longitudinal direction is referred to as a X2 direction. Further, one direction in the airflow direction Y is referred to as a Y1 direction, and the other direction in the airflow direction Y is referred to as a Y2 direction. Further, one direction in the tube stacking direction Z is referred to as a Z1 direction, and the other direction in the tube stacking direction is referred to as a Z2 direction. The X2 direction corresponds to a flow direction of the cooling water.

As shown in FIG. 11, in the heat exchanger 10 of this modification, the inner fin 23 includes protrusions 232b and 232c in the non-connecting portions 232b and 232c.

The protrusions 232b protrude from the non-connecting portions 231a and 231b in the Z2 direction. The protrusions 232b extend in a direction that a component in the X2 direction and a component in the Y2 direction are combined.

The protrusions 232c protrude from the non-connecting portions 231a and 231b in the Z1 direction. The protrusions 232c extend in a direction that a component in the X2 direction and a component in the Y2 direction are combined.

As shown in FIGS. 12A and 12B, each of the protrusions 232b and 232c are formed not to be in contact with the outer wall portions 210 and 211 of the tube 21.

Next, an operation example of the heat exchanger 10 of this modification will be described.

When the protrusions 232c are formed on the inner fin 23, the flow direction of the cooling water flowing inside the tube 21 can be changed as shown by an arrow in FIG. 13, for example. Note that FIG. 13 illustrates a case where the cross-sectional shape of the protrusions 232c is trapezoidal. As shown in FIG. 13, when the cooling water reaches the protrusion 232c, the cooling water flows along an outer surface of the protrusion 232c, so that the flow direction of the cooling water flowing inside the outer wall portion 210 of the tube 21 is changed in the direction Z1. As a result, the cooling water flows toward the inner surface of the tube 21 to collide with the inner wall surface of the tube 21, so that heat exchange is easily performed between the inner wall surface of the tube 21 and the cooling water. The same action and effect are exhibited at the protrusions 232c. As a result, the heat exchange between the air flowing through the outer fins 22 and the cooling water flowing inside the tube 21 can be further promoted, so that the heat transfer coefficient of the heat exchanger 10 can be improved. Although it is desirable that all of the protrusions 232b and 232c be not in contact with the outer wall portions 210 and 211 of the tube 21, a part of the protrusions 232b and 232c may be in contact with the outer wall portions 210 and 211 of the tube 21 as long as the same or similar advantages as those of the heat exchanger 10 in this embodiment can be obtained.

Further, as shown in FIG. 11, the protrusions 232c protruding in the Z2 direction and the protrusions 232c protruding in the Z1 direction are alternately arranged in the X2 direction in the tube 21 of the present modification, in other words, in the flow direction of the cooling water. Thus, the cooling water discontinuously and alternately collides with the inner surface in the Z1 direction and in the Z2 direction. As a result, the heat transfer coefficient of the heat exchanger 10 can be improved while reducing the pressure loss of the cooling water.

Third Modification

Next, a heat exchanger 13 of a third modification of the second embodiment will be described.

As shown in FIGS. 14, 15 (A), and 15 (B), in the heat exchanger 10 of this modification, each of the protrusions 232b and 232c has a so-called fish shadow streamline shape in which a protruding length increases in the X1 direction, i.e., toward an upstream side in the flow direction of the cooling water. The shapes of the protrusions 232b and 232c are also referred to as tilted blade shapes.

Next, an operation example of the heat exchanger 10 of this modification will be described.

When the cooling water flows as shown by arrows in FIG. 13, the cooling water having passed through the protrusion 232b tends to flow separately from the inner fin 23. This is a factor to reduce the heat transfer area of the cooling water in the inner fin 23.

In this regard, if the protrusions 232 are formed in a streamlined shape like the heat exchanger 10 of this modification, the cooling water having passed through the protrusions 232b and 232c tends to flow along the inner fin 23. Thus, it is possible to suppress a decrease in the heat transfer area of the cooling water in the inner fin 23.

Fourth Modification

Next, a heat exchanger 13 of a fourth modification of the second embodiment will be described.

As shown in FIGS. 16, 17 (A) and 17 (B), in the heat exchanger 10 of this modification, cross-sectional shapes of the protrusions 232b and 232c orthogonal to the directions Z1 and Z2 are circular. According to such a configuration, the cooling water easily flows along the periphery of the protrusions 232b and 232c, so that the cooling water is less likely to separate from the protrusions 232b and 232c. As a result, the heat transfer coefficient around the protrusions 232b and 232c of the inner fin 23 can be locally improved.

OTHER EMBODIMENTS

The preceding embodiments may be practiced in the following modes. In the heat exchanger 10 of each embodiment, the first space S1 is defined as the space partitioned by the connecting portions 230a and 230b, the non-connecting portion 231a of the inner fin 23, and the outer wall portions 210 and 211 of the tube 21 and the second space S2 is defined as the space partitioned by the connecting portions 230b and 230c, the non-connecting portion 231b of the inner fin 23, and the outer wall portions 210 and 211 of the tube 21. In this case, a shape of the first space S1 may be symmetrical with the second space S2 with respect to a center line of the tube 21 in the airflow direction Y. According to such a configuration, the cooling water can flow more uniformly in the internal passage of the tube 21.

The inner fin 23 of the first embodiment may have multiple protrusions 210a and 211a formed line-symmetrically with respect to the center line in the airflow direction Y. Further, the multiple protrusions 210a and 211a may be arranged in a staggered pattern or a grid pattern.

The configuration of the heat exchanger 10 of this embodiment can be applied to any heat exchanger. Applicable heat exchangers include, for example, heat exchangers in which only one type of fluid flows, small-sized down-face heat exchangers, medium-sized half-face heat exchangers, and large-sized full-face heat exchangers. Further, the flow direction of the cooling water in the heat exchanger 10 can be changed as appropriate. For example, as the heat exchanger 10, it is also possible to adopt a so-called down-flow type heat exchanger in which the cooling water flows in the vertical direction.

The configuration of the heat exchanger 10 of each embodiment is not limited to the radiator that cools the cooling water, and can be applied to any heat exchanger such as a condenser configured to condense the refrigerant through heat exchange between air and the refrigerant. When the configuration of the heat exchanger 10 of each embodiment is applied to the condenser, the refrigerant corresponds to the first fluid and the air corresponds to the second fluid.

As shown in FIG. 18, in the heat exchanger 10, the protrusions 210a and 211a may be formed on the tube 21 and the protrusions 232a and 232a may be formed on the inner fin 23. Further, the tube 21 may have a structure in which the tip ends of the tube 21 do not hold the inner fin 23.

As shown in FIG. 19, in the heat exchanger 10 of the first embodiment, the protrusions 210a and 211a of the tube 21 may be in contact with the inner fins 23. Further, in the heat exchanger 10 of the second embodiment, the protrusions 232a of the inner fin 23 may be in contact with the inner surface of the tube 21.

The number of protrusions 210a, 211a formed on the tube 21 of the first embodiment and the number of the connecting portions 230a, 230b, and 230c formed on the inner fin 23 can be arbitrarily changed. Further, the number of protrusions 232a, 232b, 232c formed on the inner fin 23 of the second embodiment and the number of the connecting portions 230a, 230b, and 230c can be arbitrarily changed.

The present disclosure is not limited to the specific examples described above. The specific examples described above which have been appropriately modified in design by those skilled in the art are also encompassed in the scope of the present disclosure so far as the modified specific examples have the features of the present disclosure. Each element included in each of the specific examples described above, and the placement, condition, shape, and the like of the element are not limited to those illustrated, and can be modified as appropriate. The combinations of the elements in each of the specific examples described above can be changed as appropriate, as long as it is not technically contradictory.

Number	Date	Country	Kind
2019-045425	Mar 2019	JP	national
2020-021446	Feb 2020	JP	national

	Number	Date	Country
Parent	PCT/JP2020/009030	Mar 2020	US
Child	17404719		US

HEAT EXCHANGER

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