EP3754284A1

EP3754284A1 - Heat exchanger and refrigeration cycle device

Info

Publication number: EP3754284A1
Application number: EP20158255.8A
Authority: EP
Inventors: Kazuki KOISHIHARA; Kazuhiko Machida; Yuki YAMAOKA
Original assignee: Panasonic Intellectual Property Management Co Ltd
Current assignee: Panasonic Intellectual Property Management Co Ltd
Priority date: 2019-05-31
Filing date: 2020-02-19
Publication date: 2020-12-23
Anticipated expiration: 2040-02-19
Also published as: JP2020197311A; JP7129602B2; EP3754284B1

Abstract

The present invention provides a heat exchanger (32) including: an inner pipe (1); an insertion body (2) inserted into the inner pipe (1); and at least one or more outer pipes (3) provided around an outer periphery of the inner pipe (1) and through which second fluid flows, wherein the insertion body (2) is formed from a shaft (21) and a projection (22) formed on an outer surface of the shaft (21), first fluid flows through a spiral flow path (23) formed from at least an inner surface of the inner pipe (1) and the projection (22), and a plurality of thickness projections (22b) are provided on the spiral flow path (23) at predetermined intervals in a flowing direction of the first fluid, and a flow path area of the spiral flow path (23) is made small at the predetermined intervals in the flowing direction of the first fluid by each of the thickness projections (22b). According to this, the heat exchanger (32) can suppress the local precipitation of scale by simple means and heat exchanging efficiency can be enhanced.

Description

[TECHNICAL FIELD]

The present invention relates to a heat exchanger which exchanges heat between low temperature liquid and high temperature liquid.

[BACKGROUND TECHNIQUE]

A heat exchanger of this kind heats water by refrigerant and produces high temperature water in many cases. It is known that if water becomes high temperature, solubility of gas (oxygen or nitrogen) existing in water is lowered, and the gas is precipitated into water as air bubble.
If the precipitated air bubble adheres to a heat-transfer surface, since this hinders heat exchange between water and refrigerant, heat exchanging efficiency of the heat exchanger is deteriorated.
Further, if air bubble adheres to the heat-transfer surface, a micro layer where ion concentration is generated is formed on a boundary face between the air bubble and the heat-transfer surface. Hence, as compared with a surface to which air bubble is not adhered, scale nucleus which becomes a point of origin of scale is largely precipitated locally.
It is possible to remove the scale which is precipitated in this manner by applying shearing stress.
Hence, to suppress the growth of the scale, secondary side liquid which is to be heated to which preset pressure is applied is made to flow into the heat exchanger at preset timing. According to this, shearing stress which can remove the precipitated scale is applied to a contact surface between the heat-transfer surface and the secondary side liquid which is to be heated in the heat exchanger (see patent document 1 for example).

[PRIOR ART DOCUMENT]

[Patent Document]

[Patent Document 1] PCT International Publication No.2017/158938

[SUMMARY OF THE INVENTION]

[PROBLEM TO BE SOLVED BY THE INVENTION]

According to the conventional configuration, however, parts such as a pressure sensor, a solenoid valve and the like are required, and a configuration of a flow path becomes complicated. Further, there is a problem that costs are increased.
The present invention has been accomplished to solve the conventional problem, and it is an object of the invention to provide a heat exchanger having high heat exchanging efficiency and capable of suppressing local precipitation of scale by simple means.

[MEANS FOR SOLVING THE PROBLEM]

To solve the conventional problem, the present invention provides a heat exchanger including: an inner pipe; an insertion body inserted into the inner pipe; and at least one or more outer pipes provided around an outer periphery of the inner pipe and through which second fluid flows, wherein the insertion body is formed from a shaft and a projection formed on an outer surface of the shaft, first fluid flows through a spiral flow path formed from at least an inner surface of the inner pipe and the projection, and a plurality of thickness projections are provided on the spiral flow path at predetermined intervals in a flowing direction of the first fluid, and a flow path area of the spiral flow path is made small at the predetermined intervals in the flowing direction of the first fluid by each of the thickness projections.
According to this, in the spiral flow path, flow speed and shearing stress of the first fluid can be increased at predetermined intervals. Therefore, it becomes easy to wash away air bubble which is precipitated on and adhered to a wall surface of the spiral flow path.
In addition, since centrifugal force is applied to the first fluid which flows through the spiral flow path, air bubble having smaller density than that of the first fluid is washed away relatively toward the shaft. Therefore, it is possible to restrict the air bubble from again adhering to the inner surface (heat-transfer surface) of the inner pipe.
For this reason, it is possible to restrict scale from locally precipitating by adhesion of air bubble to the inner surface (heat-transfer surface) of the inner pipe, and it is possible to prevent the inhibition of heat exchanging by scale.
Further, in the spiral flow path, it is possible to increase the flow speed of the first fluid at the predetermined intervals, and a stirring effect can be enhanced by centrifugal force. Therefore, flow of the first fluid can be disturbed and heat exchanging efficiency of the heat exchanger can be enhanced.

[EFFECT OF THE INVENTION]

According to the present invention, it is possible to provide a heat exchanger having high heat exchanging efficiency and capable of suppressing local precipitation of scale by simple means.

[BRIEF DESCRIPTION OF THE DRAWINGS]

Fig. 1 is a circuit diagram of a refrigeration cycle device using a heat exchanger of an embodiment of the present invention;
Fig. 2 is a perspective view of the heat exchanger;
Fig. 3(a) is a sectional view of the heat exchanger taken along a surface A thereof, and Fig. 3(b) is a sectional view of the heat exchanger taken along a surface B thereof;
Fig. 4(a) is a conceptual diagram of flow speed distribution of a first fluid taken along the surface A of the heat exchanger, and Fig. 4(b) is a conceptual diagram of flow speed distribution of the first fluid taken along the surface B of the heat exchanger; and
Fig. 5(a) is a conceptual diagram of air bubble adhered to an inner surface of an inner pipe in the embodiment of the invention which is a grooved pipe, and Fig. 5(b) is a conceptual diagram of air bubble adhered to an inner surface of an inner pipe which is a flat pipe.

[MODE FOR CARRYING OUT THE INVENTION]

A first invention provides a heat exchanger including: an inner pipe; an insertion body inserted into the inner pipe; and at least one or more outer pipes provided around an outer periphery of the inner pipe and through which second fluid flows, wherein the insertion body is formed from a shaft and a projection formed on an outer surface of the shaft, first fluid flows through a spiral flow path formed from at least an inner surface of the inner pipe and the projection, and a plurality of thickness projections are provided on the spiral flow path at predetermined intervals in a flowing direction of the first fluid, and a flow path area of the spiral flow path is made small at the predetermined intervals in the flowing direction of the first fluid by each of the thickness projections.
According to this, in the spiral flow path, flow speed and shearing stress of the first fluid can be increased at predetermined intervals. Therefore, it becomes easy to wash away air bubble which is precipitated on and adhered to a wall surface of the spiral flow path.
In addition, since centrifugal force is applied to the first fluid which flows through the spiral flow path, air bubble having smaller density than that of the first fluid is washed away relatively toward the shaft. Therefore, it is possible to restrict the air bubble from again adhering to the inner surface (heat-transfer surface) of the inner pipe.
For this reason, it is possible to restrict scale from locally precipitating by adhesion of air bubble to the inner surface (heat-transfer surface) of the inner pipe, and it is possible to prevent the inhibition of heat exchanging by scale.
Further, in the spiral flow path, it is possible to increase the flow speed of the first fluid at the predetermined intervals, and a stirring effect can be enhanced by centrifugal force. Therefore, flow of the first fluid can be disturbed and heat exchanging efficiency of the heat exchanger can be enhanced.
According to a second invention, especially in the first invention, the thickness projections are formed by making a thickness of the projection in its axial direction at predetermined intervals in a circumferential direction of the projection thicker than other portions.
With this, in the spiral flow path, flow speed and shearing stress of the first fluid can be increased at predetermined intervals by simple means. Therefore, it becomes easy to wash away air bubble which is precipitated on and adhered to a wall surface of the spiral flow path.
According to a third invention, especially in the first or second invention, a line connecting length centers of the plurality of thickness projections in a circumferential direction thereof is in parallel to a center line of the insertion body in its axial direction.
With this, since the thickness projections provided on the spiral flow path are opposed to each other in the axial direction, a flow path area can be made especially small in the spiral flow path.
With this, in the spiral flow path, flow speed and shearing stress of the first fluid can be increased at predetermined intervals. Therefore, it becomes easy to wash away air bubble which is precipitated on and adhered to a wall surface of the spiral flow path.
According to a fourth invention, especially in any one of the first to third inventions, an axial thickness of a root of the thickness projection is thicker than that of a tip end of the thickness projection.
With this, flow speed of the first fluid can be increased at predetermined intervals without reducing a heat-transfer area on the side of the first fluid, i.e., a heat-transfer area between the inner pipe and the first fluid. Hence, it is possible to suppress the local growth of scale while maintaining performance of the heat exchanger.
According to a fifth invention, especially in any one of the first to fourth inventions, an axial thickness of a root of the thickness projection is the greatest.
According to this, in the spiral flow path, flow speed and shearing stress of the first fluid can be increased at predetermined intervals. Therefore, it becomes easy to wash away air bubble which is precipitated on and adhered to a wall surface of the spiral flow path.
In addition, it is possible to suppress the increase in flow sound as small as possible by suppressing abrupt variation of the flow speed of the first fluid as small as possible.
According to a sixth invention, especially in any one of the first to fifth inventions, the inner pipe is an inner surface grooved pipe.
With this, since the inner pipe is the inner surface grooved pipe, a contact area between the pipe wall of the inner pipe and precipitating and adhering air bubble is reduced as compared with that of the flat pipe. Therefore, air bubble which adheres to the inner surface of the inner pipe can easily separate from the pipe wall. Hence, it becomes easier to wash away air bubble which adheres to the pipe wall of the inner pipe, and it is possible to suppress the local growth of scale.
In addition, since the inner surface area of the inner pipe is increased as compared with that of the flat pipe, the heat-transfer area on the side of the first fluid, i.e., the heat-transfer area between the inner surface of the inner pipe and the first fluid is increased, and flow of water which is first fluid flowing in a spiral form can further be disturbed by the inner surface grove. Therefore, the performance of the heat exchanger can further be enhanced.
A seventh invention provides a refrigeration cycle device formed by annularly connecting, to one another, a compressor, a decompressor, an evaporator and the heat exchanger according to any one of the first to sixth inventions.
With this, it is possible to provide a refrigeration cycle device having a heat exchanger capable of suppressing local precipitation of scale by simple means, and capable of realizing high heat exchanging efficiency.
An embodiment of the present invention will be described below with reference to the drawings. The invention is not limited to the embodiment.
Fig. 1 is a circuit diagram of a refrigeration cycle device using a heat exchanger of the embodiment of the present invention.
The refrigeration cycle device 36 is formed by annularly connecting, to one another, a compressor 31 for compressing refrigerant which is second fluid, a heat exchanger 32 to which high temperature refrigerant compressed by the compressor 31 radiates heat and for heating water which is low temperature first fluid, a decompressor 33 for decompressing, to low pressure, high pressure refrigerant compressed by the compressor 31, and an evaporator 34 for absorbing heat by air flow generated by a blower 35.
In the heat exchanger 32, water and refrigerant flow in directions opposed to each other and exchange heat therebetween. Low temperature water is conveyed to the heat exchanger 32 by a conveying device 37, the water is heated by refrigerant and becomes hot water. A warm water circuit 38 is connected to the heat exchanger 32, the heated hot water is supplied or utilized for heating a room, or the hot water is stored.
Fig. 2 is a perspective view of the heat exchanger of the embodiment of the invention.
In Fig. 2, the heat exchanger 32 is composed of an inner pipe 1 through which water flows, an insertion body 2 inserted into the inner pipe 1, and at least one or more outer pipes 3 which come into tight contact with an outer periphery of the inner pipe 1. Refrigerant (carbon dioxide) flows through the outer pipes 3.
The outer pipe 3 is spirally wound around the outer periphery of the inner pipe 1 at a predetermined pitch.
The insertion body 2 is composed of a cylindrical shaft 21 and a projection 22 which is spirally provided on an outer periphery of the shaft 21. Water flows through a spiral flow path 23. The spiral flow path 23 has a substantially rectangular cross section formed by an inner surface of the inner pipe 1 and a projection 22 which is adjacent to an outer surface of the shaft 21.
Fig. 3(a) is a sectional view of the heat exchanger of the embodiment taken along a surface A of the heat exchanger. The projection 22 of the insertion body 2 in the cross section taken along the surface A is a standard projection 22a formed by a standard thickness.
Fig. 3(b) is a sectional view of the heat exchanger of the embodiment taken along a surface B of the heat exchanger. The projection 22 of the insertion body 2 in the cross section taken along the surface B is thickness projections 22b which are thicker than the standard projection 22a in the axial direction.
The thickness projections 22b are formed thicker than the standard projection 22a in the axial direction at predetermined intervals in a circumferential direction of the thickness projections 22b.
A line which connects length centers of the plurality of thickness projections 22b in the circumferential direction is in parallel to a center line of the cylindrical shaft 21 of the insertion body 2 in the axial direction.
Hence, the thickness projections 22b provided in the spiral flow path 23 are opposed to each other in the axial direction. Therefore, a flow path area of the spiral flow path 23 becomes smaller at predetermined intervals in a flowing direction of water.
A thickness of the thickness projection 22b gradually becomes thicker in the axial direction from a tip end to a root of the thickness projection 22b in its height direction, and a length center of the root in the circumferential direction has the greatest thickness in the axial direction.
In the embodiment of the invention, the thickness projections 22b are formed in the circumferential direction around an axis of the cylindrical shaft 21 of the insertion body 2 at predetermined intervals of 180°.
That is, water flowing through the spiral flow path 23 collides against the thickness projections 22b at every half around.
This is because when the insertion body 2 is made of resin material, since an axial thickness of a length center of the root of the thickness projection 22b in the circumferential direction is formed most thick, the insertion body 2 can be produced such that two lines connecting length centers of the roots of the plurality of thickness projections 22b in the circumferential direction are formed as dividing surface (PL) of a mold.
Property that liquid adheres to a surface of a solid object is called "wettability". Here, a length of the inner surface of the inner pipe 1 which forms a cross section of a flow path of the spiral flow path 23 through which water flows is defined as a wetting length of a heat-transfer surface.
At this time, a wetting length Lb of the heat-transfer surface of the thickness projection 22b is about the same as a wetting length La of a heat-transfer surface of the standard projection 22a, and the inner surface of the inner pipe 1 is an inner surface grooved pipe which is finely grooved.
The heat exchanger 32 configured as described above is mounted in a CO₂ heat pump hot water supply system. Operation and effects of the heat exchanger 32 will be described below.
The heat exchanger flows, in opposed directions, high temperature carbon dioxide flowing through the outer pipe 3 and low temperature water flowing through the spiral flow path 23 formed between the inner pipe 1 and the insertion body 2, exchanges heat between the carbon dioxide and the low temperature water, and produces high temperature hot water.
Since centrifugal force is applied to the first fluid which flows through the spiral flow path 23, secondary flow is generated on a surface which intersects with a flowing direction at right angles like a bent pipe.
According to this, the flow of water is disturbed, and temperature distribution of water on the surface which intersects with the flowing direction at right angles is improved. Therefore, even when flow speed of water is slow as in the CO₂ heat pump hot water supply system, it is possible to enhance the heat exchanging efficiency of the heat exchanger 32.
As described above, in the CO₂ heat pump hot water supply system using carbon dioxide as refrigerant, heating temperature of water can be made high.
On the other hand, at an outlet of the heat exchanger 32 where temperature of water becomes high, since solubility of existing gas (such as oxygen and nitrogen) is lowered, there is a problem that precipitation appears on a wall surface of the spiral flow path 23 as air bubble, and scale is locally precipitated and heat exchanging is hindered.
In the embodiment of the invention, the projection 22 of the insertion body 2 has the thickness projections 22b which are thick in the axial direction at predetermined intervals as shown in Figs. 3(a) and 3(b).
Hence, in Fig. 3(a), the spiral flow path 23 through which water flows is formed by the inner surface of the inner pipe 1, the outer surface of the shaft 21 and the outer surface of the standard projection 22a.
In Fig. 3(b), the spiral flow path 23 is formed by the inner surface of the inner pipe 1 and the outer surface of the thickness projection 22b.
In this manner, since the thickness of the projection 22 in the axial direction is formed such that the thickness of the thickness projection 22b is greater than that of the standard projection 22a, a cross section of the flow path through which water flows becomes smaller when water passes through the thickness projection 22b.
Therefore, the thickness projections 22b are provided on the spiral flow path 23 at predetermined intervals in the flowing direction of water, and the cross section of the flow path is made small by narrowing a width of the flow path on the side of the outer surface of the shaft 21 instead of a width of the flow path on the side of the inner surface of the inner pipe 1.
That is, as shown in Fig. 3(a), the spiral flow path 23 through which water flows is formed by the inner surface of the inner pipe 1, the outer surface of the shaft 21 and the outer surface of the standard projection 22a. That is, a cross section of the flow path formed on the cross section A is defined as S1.
On the other hand, as shown in Fig. 3(b), the spiral flow path 23 through which water flows is formed by the inner surface of the inner pipe 1 and the outer surface of the thickness projection 22b. That is, a cross section formed on the cross section B is defined as S2.
At this time, a relation between the flow path cross section S1 and the flow path cross section S2 is S1>S2.
The thickness of the thickness projection 22b in the axial direction from the tip end to the root in the height direction gradually becomes thicker, and the axial thickness of the length center of the root in the circumferential direction is formed greatest.
The wetting length Lb of the heat-transfer surface of the thickness projection 22b is about the same as the wetting length La of the heat-transfer surface of the standard projection 22a.
According to this, the cross section of the flow path can be varied without varying the length of the inner surface of the inner pipe 1 which forms the cross section of the flow path of the spiral flow path 23 through which water flows.
Therefore, when the heat-transfer areas of water and the inner surface of the inner pipe 1 are the same and the spiral flow path 23 is formed by the thickness projections 22b, the flow speed of water can be made greater by reducing the cross section area of the flow path as compared with a case where the spiral flow path 23 is formed by the standard projection 22a.
Fig. 4(a) is a conceptual diagram of flow speed distribution of the first fluid taken along the surface A of the heat exchanger of the embodiment of the invention. The projection 22 of the insertion body 2 in the cross section taken along the surface A is the standard projection 22a having a standard thickness.
Fig. 4(b) is a conceptual diagram of flow speed distribution of the first fluid taken along the surface B of the heat exchanger of the embodiment of the invention. The projection 22 of the insertion body 2 in the cross section taken along the surface B is the thickness projection 22b which is thicker in the axial direction than the standard projection 22a.
As shown in Figs. 4(a) and 4(b), flow speed Ub of water when the spiral flow path 23 is formed by the thickness projections 22b is greater than flow speed Ua of water when the spiral flow path 23 is formed by the standard projection 22a. Therefore, velocity gradient near the wall surface of the spiral flow path 23 is greater when the spiral flow path 23 is formed by the thickness projections 22b. $τ = µ \frac{du}{dz}$
In equation 1, τ represents shearing stress of viscose fluid, µ represents viscosity coefficient, and du/dz represents velocity gradient in a direction perpendicular to flow.
As shown in equation 1, the shearing stress τ of viscose fluid is proportional to velocity gradient in the direction perpendicular to flow.
Hence, velocity gradient near the wall surface of the spiral flow path 23 is greater when the spiral flow path 23 is formed by the thickness projections 22b. Therefore, when the spiral flow path 23 is formed by the thickness projections 22b, the shearing stress of water flowing through the spiral flow path 23 is also greater as compared with a case where the spiral flow path 23 is formed by the standard projection 22a.
Therefore, when the spiral flow path 23 is formed by the thickness projections 22b, even if air bubble is precipitated on and adhered to the water surface of the spiral flow path 23, since greater shearing stress is applied to the air bubble, it is possible to wash away the air bubble from the wall surface.
According to this, it is possible to suppress the local growth of scale generated from the air bubble as the point of origin, and it is possible to prevent hindrance of heat transfer caused by air bubble.
Further, since centrifugal force is applied to the first fluid which flows through the spiral flow path 23, air bubble having smaller density than water which is washed away from the wall surface of the spiral flow path 23 is washed away relatively toward the shaft 21. Therefore, it is possible to restrict air bubble from again adhering to the inner surface (heat-transfer surface) of the inner pipe 1.
That is, in the heat exchanger 32 of the embodiment of the invention, as shown in Figs. 3(a) and 3(b), the axial thicknesses of the thickness projections 22b are formed thicker than the standard projection 22a, and the thickness projections 22b are formed around the axis of the cylindrical shaft 21 of the insertion body 2 at predetermined intervals of 180°.
The line which connects length centers of the plurality of thickness projections 22b in the circumferential direction is in parallel to the center line of the cylindrical shaft 21 of the insertion body 2 in the axial direction.
Hence, since the thickness projections 22b provided on the spiral flow path 23 are opposed to each other in the axial direction, the flow path area of the spiral flow path 23 becomes small every half around.
According to this, flow speed of water flowing through the spiral flow path 23 becomes greater at least every half around, and shearing stress also becomes greater.
Therefore, it is possible to more reliably wash away air bubble, and to restrict air bubble from again adhering to the inner surface (heat-transfer surface) of the inner pipe 1. Hence, it is possible to reliably suppress the local growth of scale and hindrance of heat exchanging.
Fig. 5(a) is a conceptual diagram of air bubble adhered to the inner surface of the inner pipe in the embodiment of the invention which is the grooved pipe.
Fig. 5(b) is a conceptual diagram of air bubble adhered to an inner surface of an inner pipe which is a flat pipe to compare with Fig. 5(a).
In the embodiment of the invention, the inner pipe 1 is an inner surface grooved pipe whose inner surface is finely grooved.
As shown in Figs. 5(a) and 5(b), a contact area between the heat-transfer surface and air bubble which adheres to the heat-transfer surface when the inner pipe 1 is the inner surface grooved pipe is smaller than a contact area between the heat-transfer surface and air bubble which adheres to the heat-transfer surface when the inner pipe 1 is a flat pipe.
According to this, since the inner pipe 1 is the inner surface grooved pipe, a contact area between the pipe wall of the inner pipe 1 and air bubble which is precipitates and adhered is reduced as compared with that of the flat pipe, and air bubble adhered to the inner surface of the inner pipe 1 can be separated from the pipe wall more easily. Therefore, it is possible to more easily wash away air bubble adhered to the pipe wall of the inner pipe 1, and to suppress the local growth of scale.
In addition, since an inner surface area of the inner pipe 1 is increased as compared with that of the flat pipe, the heat-transfer area on the side of the first fluid, i.e., the heat-transfer area between the inner surface of the inner pipe 1 and the first fluid is increased, and flow of water flowing in a spiral form can further be disturbed by the inner surface groove. Hence performance of the heat exchanger can further be enhanced.
In the embodiment, carbon dioxide is used as refrigerant which flows in the outer pipe 3, it is possible to use hydrocarbon-based refrigerant or HFC-based (R410A, R32 and the like) refrigerant, or alternative refrigerant thereof.
In this embodiment, the thickness projections 22b are formed around the axis of the cylindrical shaft 21 of the insertion body 2 at predetermined intervals of 180°, but even if other angle is employed, the same effect can be obtained.

[INDUSTRIAL APPLICABILITY]

As described above, the heat exchanger of the present invention can suppress the local precipitation of scale by simple means and can realize high heat exchanging efficiency. Therefore, the heat exchanger can be applied to an air conditioner, a hot water supply system and the like.

[EXPLANATION OF SYMBOLS]

1: inner pipe
2: insertion body
3: outer pipe
21: shaft
22: projection
22a: standard projection
22b: thickness projection
23: spiral flow path
31: compressor
32: heat exchanger (radiator)
33: decompressor
34: evaporator
36: refrigeration cycle device

Claims

A heat exchanger (32) comprising: an inner pipe (1); an insertion body (2) inserted into the inner pipe (1); and at least one or more outer pipes (3) provided around an outer periphery of the inner pipe (1) and through which second fluid flows, wherein the insertion body (2) is formed from a shaft (21) and a projection (22) formed on an outer surface of the shaft (21), first fluid flows through a spiral flow path (23) formed from at least an inner surface of the inner pipe (1) and the projection (22), and a plurality of thickness projections (22b) are provided on the spiral flow path (23) at predetermined intervals in a flowing direction of the first fluid, and a flow path area of the spiral flow path (23) is made small at the predetermined intervals in the flowing direction of the first fluid by each of the thickness projections (22b).
The heat exchanger (32) according to claim 1, wherein the thickness projections (22b) are formed by making a thickness of the projection (22) in its axial direction at predetermined intervals in a circumferential direction of the projection (22) thicker than other portions.
The heat exchanger (32) according to claim 1 or 2, wherein a line connecting length centers of the plurality of thickness projections (22b) in a circumferential direction thereof is in parallel to a center line of the insertion body (2) in its axial direction.
The heat exchanger (32) according to any one of claims 1 to 3, wherein an axial thickness of a root of the thickness projection (22b) is thicker than that of a tip end of the thickness projection (22b).
The heat exchanger (32) according to any one of claims 1 to 4, wherein an axial thickness of a root of the thickness projection (22b) is the greatest.
The heat exchanger (32) according to any one of claims 1 to 5, wherein the inner pipe (1) is an inner surface grooved pipe.
A refrigeration cycle device (36) formed by annularly connecting, to one another, a compressor (31), a decompressor (33), an evaporator (34) and the heat exchanger (32) according to any one of claims 1 to 6.