US20080296002A1

US20080296002A1 - Heat exchanger core, heat exchanger, and evaporator of refrigeration cycle apparatus

Info

Publication number: US20080296002A1
Application number: US12/156,215
Authority: US
Inventors: Tatsuhiko Nishino; Norimasa Baba; Hironobu Fujiyoshi
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2007-06-01
Filing date: 2008-05-30
Publication date: 2008-12-04
Also published as: CN101315231A; DE102008026120A1; JP2008298391A

Abstract

A heat exchanger core includes a first tube, a second tube, a first fin, a second fin, and a connection member. The second tube is provided upstream of the first tube in a direction of air flow. The first fin is coupled to an outer surface of the first tube for facilitating heat exchange of the first tube. The second fin is coupled to an outer surface of the second tube for facilitating heat exchange of the second tube. The second fin is located upstream of the first fin to define a clearance therebetween. The connection member connects peaks of the first and second fins or connects valleys of the first and second fins.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and incorporates herein by reference Japanese Patent Application No. 2007-146619 filed on Jun. 1, 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a heat exchanger core, a heat exchanger, and an evaporator for a refrigeration cycle apparatus. For example, in each of the above apparatuses, first tubes are located upstream of second tubes in an air flow direction.
2. Description of Related Art
Conventionally, an evaporator for an air conditioning system has a heat exchanger core member that includes a first group of multiple flat tubes and a second group of multiple flat tubes. The first group of flat tubes and the second group of flat tubes are arranged in an direction of air flow. Each tube of the first group of flat tubes is arranged in a direction perpendicular to the air flow direction, and each tube of the second group of flat tubes is arranged in the direction perpendicular to the air flow direction. An outer surface of each tube of the first group of flat tubes is coupled with a first corrugated fin, and an outer surface of each tube of the second group of flat tubes is coupled with a second corrugated fin (see, for example, JP-A-2000-179988 corresponding to U.S. Pat. No. 6,308,527).
In the above technique, there is formed a clearance between the first corrugated fins on an airflow upstream side and the second corrugated fins on an airflow downstream side, and the clearance separates the first and second corrugated fins. As a result, even when condensate is generated at the first corrugated fins on the airflow upstream side, the condensate is not carried by blown air to the second corrugated fins on the airflow downstream side, however, the condensate falls through the clearance. Due to the above, the condensate is limited from being blown away or shed from the evaporator toward the airflow downstream side.
Recently, more evaporators for the air conditioning system have tubes with thinner walls in order to efficiently achieve weight reduction and to improve performance of heat exchange. As a result, rigidity of the heat exchanger core member is decreased. Therefore, a noise value of a sound of passing refrigerant, which sound is made while the refrigerant passes through the tube, has further been increased disadvantageously.

SUMMARY OF THE INVENTION

The present invention is made in view of the above disadvantages. Thus, it is an objective of the present invention to address at least one of the above disadvantages.
To achieve the objective of the present invention, there is provided a heat exchanger core that includes a first tube, a second tube, a first fin, a second fin, and a connection member. The first tube is configured to carry a first fluid flowing therethrough to cause heat exchange between the first fluid and air. The second tube is provided upstream of the first tube in a direction of air flow, and the second tube carries a second fluid flowing therethrough to cause heat exchange between the second fluid and air. The first fin is coupled to an outer surface of the first tube for facilitating heat exchange of the first tube, and the first fin has a series of corrugations to have a peak and a valley. The second fin is coupled to an outer surface of the second tube for facilitating heat exchange of the second tube, and the second fin has a series of corrugations to have a peak and a valley. The second fin is located upstream of the first fin in the airflow direction and apart from the first fin to define a clearance therebetween. The connection member is configured to connect the first fin and the second fin. The connection member connects the peak of the first fin with the peak of the second fin or connects the valley of the first fin with the valley of the second fin.
To achieve the objective of the present invention, there is also provided a heat exchanger that includes the above heat exchanger core, a plurality of first tubes, a plurality of second tubes, a first tank, a second tank, a third tank, and a fourth tank. The first tank is configured to distribute fluid to each of the plurality of first tubes. The second tank is configured to collect fluid flowing out of each of the plurality of first tubes. The third tank is configured to distribute fluid to each of the plurality of second tubes. The fourth tank is configured to collect fluid flowing out of each of the plurality of second tubes. The plurality of first tubes is in fluid communication with the first and second tanks. The plurality of second tubes is in fluid communication with the third and fourth tanks.
To achieve the objective of the present invention, there is also provided an evaporator for a refrigeration cycle apparatus, which evaporator includes the above heat exchanger. The first and second tubes carry refrigerant as fluid flowing therethrough, and the refrigerant evaporates by absorbing heat from air.
To achieve the objective of the present invention, there is also provided a heat exchanger core that includes a first tube, a second tube, a first fin, a second fin, and a plurality of connection members. The first tube is configured to carry a first fluid flowing therethrough to cause heat exchange between the first fluid and air. The second tube is provided upstream of the first tube in a direction of air flow, and the second tube carries a second fluid flowing therethrough to cause heat exchange between the second fluid and air. The first fin is coupled to an outer surface of the first tube for increasing a heat exchange contact area of the first tube with air, and the first fin has a series of corrugations to form a plurality of fin crests. The second fin is coupled to an outer surface of the second tube for increasing a heat exchange contact area of the second tube with air, and the second fin has a series of corrugations to form a plurality of fin crests. The second fin is spaced away from the first fin in the airflow direction to define a clearance therebetween. Each of the plurality of connection members is configured to connects the first and second fins to span the clearance. Each of the plurality of connection members connects one of the plurality of fin crests of the first fin with an adjacent one of the plurality of fin crests of the second fin. The plurality of connection members is arranged at predetermined intervals.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with additional objectives, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which:

FIG. 1 is an appearance view of an evaporator for a refrigeration cycle apparatus according to a first embodiment of the present invention;

FIG. 2 is a diagram illustrating an internal configuration of the evaporator for the refrigeration cycle apparatus shown in FIG. 1;

FIG. 3 is a cross-sectional view of a fin shown in FIG. 1;

FIG. 4 is a perspective view of tubes and part of connected fins shown in FIG. 1;

FIG. 5 is a cross-sectional view of the fin for explaining a connection dimension;

FIG. 6 is a development illustrating the fins shown in FIG. 1;

FIG. 7 is a diagram illustrating an experimental result for examining rigidity of a heat exchanger core shown in FIG. 1;

FIG. 8 is a diagram illustrating another experimental result for examining a noise value of the heat exchanger core shown in FIG. 1;

FIG. 9 is a diagram illustrating another experimental result for examining a blown-away critical wind velocity of the heat exchanger core shown in FIG. 1;

FIG. 10 is a development illustrating one example of the fins shown in FIG. 1;

FIG. 11 is a development illustrating fins of an evaporator for a refrigeration cycle apparatus according to a second embodiment of the present invention;

FIG. 12 is a perspective view of tubes of an other embodiment of the present invention; and

FIG. 13 is a perspective view illustrating of a modification of tubes according to a third embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

First Embodiment

A first embodiment of the present invention is described with reference to accompanying drawings of an evaporator for a refrigeration cycle apparatus of the first embodiment of the present invention. FIG. 1 is a perspective view illustrating an appearance of the evaporator of the present embodiment, and FIG. 2 is a schematic perspective view illustrating an internal configuration of the evaporator.
The evaporator is mounted inside a case of an air-conditioning unit for an air conditioning system for a vehicle. The evaporator receives air that is blown by an air blower (not shown) in a direction (air flow direction) indicated by an arrow X, and heat is exchanged between the blown air and the refrigerant.
The evaporator includes a connection block 1 as shown in FIG. 1, and the connection block 1 includes a refrigerant inlet 8 a and a refrigerant outlet 8 b. Refrigerant flows from an expansion valve (not shown) into the evaporator through the refrigerant inlet 8 a and flows out of the evaporator through the refrigerant outlet 8 b toward a compressor (not shown). The evaporator forms a known refrigeration cycle apparatus together with the expansion valve and the compressor.
The evaporator includes tubes 2, 3, 4, 5 as shown in FIGS. 1 and 2, and the multiple tubes 2 are arranged or spaced away from each other in a direction perpendicular to the air flow direction X, and the multiple tubes 3 are arranged in a direction (direction B in FIG. 2) identical with the arrangement direction the tubes 2.
The multiple tubes 4 are spaced away from each other in a direction parallel with the tubes 2 and are positioned upstream of the tubes 2 in the air flow direction X. The multiple tubes 5 are also spaced away from each other in a direction parallel with the tubes 3 and are positioned upstream of the tubes 3 in the air flow direction X.
Thus, the tubes 2, 3, 4, 5 are arranged such that a first row having the tubes 2, 3 is located downstream of a second row having the tubes 4, 5 in the air flow direction X to form two rows as shown in FIG. 2.
The evaporator includes multiple tank members 8, 9, 11, 12. The tank member 8 is connected with one longitudinal end portions of the tubes 2, 3. The tank member 8 is divided by a partition wall 14 into a distribution tank chamber 81 on the tube 2 side and a collection tank chamber 82 on the tube 3 side. Also, the tank member 11 is divided into a distribution tank chamber 110 and a collection tank chamber 111 by a partition wall 15.
The refrigerant flows from the refrigerant inlet 8 a of the connection block 1 through an inlet 6 (see FIG. 2), and then the distribution tank chamber 81 distributes or delivers the above refrigerant to each of the multiple tubes 2. In the multiple tubes 2, the refrigerant flows in a direction indicated by an arrow Ra shown in FIG. 2. The tank member 9 causes the refrigerant flowing out of each of the multiple tubes 2 to merge together or to be collected together. It should be noted that, the refrigerant corresponds to first and second fluids, which fluids are mutually identical with one another.
In the tank member 9, the refrigerant flows in a direction indicated by an arrow Rb, and the refrigerant is distributed to each of the multiple tubes 3. In the multiple tubes 3, the refrigerant flows in a direction indicated by an arrow Rc. The refrigerant is merged together in the collection tank chamber 82 of the tank member 8.
The collection tank chamber 82 and the distribution tank chamber 110 of the tank member 11 are communicated with each other through multiple communication holes 18. The merged refrigerant at the collection tank chamber 82 flows into the distribution tank chamber 110 of the tank member 11 and is distributed into the multiple tubes 5 at the distribution tank chamber 110.
The multiple tubes 5 causes the refrigerant to flow therethrough in a direction indicated by an arrow Re. Then, the refrigerant merges together at the tank member 12 and flows in a direction indicated by an arrow Rf thorough the tank member 12. Then, the refrigerant is distributed into the multiple tubes 4. In the multiple tubes 4, the refrigerant flows in a direction indicated by an arrow Rg, and the refrigerant merges together at the collection tank chamber 111 of the tank member 11. The refrigerant flows in a direction indicated by an arrow Rh and flows out of the collection tank chamber 111 through an outlet 7. Then, the refrigerant is discharged through the refrigerant outlet 8 b of the connection block 1 (see FIG. 1).
Each of the above tubes 2, 3, 4, 5 has a refrigerant passage that has a flat cross sectional shape, and the refrigerant absorbs heat from air to evaporate in the tubes 2, 3, 4, 5. In the present embodiment, the tubes 2 to 5 are made of aluminum, and the tubes 2 to 5 are inner-fin-type tubes, which are made by folding a sheet material and by placing inner fins between the folded sheet material. Then, in the above state, both end portions of the sheet material are brazed to be joined with each other.
The evaporator includes corrugated fins 19, 20 arranged as shown in FIG. 2, and each of the corrugated fins 19, 20 is made of an aluminum sheet material to have a tortuous shape or a series of corrugations as shown in FIG. 3. FIG. 3 is a cross-sectional view of the corrugated fin 19 (20).
Specifically, the corrugated fin 19 is made by folding the sheet material such that intervals fp between peaks 31 are identical with each other. Alternatively, the sheet material may be folded such that intervals fp between the valleys 30 are similar to each other. In the above, the peaks 31 project in a direction opposite to a projection direction of the valleys 30 as shown in FIG. 3. Also, the corrugated fin 20 is made by folding a sheet material such that intervals fp between peaks 31 are similar to each other. Alternatively, the corrugated fin 20 may be made by folding the sheet material such that intervals fp between valleys 30 are identical with each other. In the present specification, a dimension between the peaks 31 or a dimension between the valleys 30 is defined as a fin pitch fp.
In the present embodiment, the fin pitches fp of the corrugated fin 19 are identical with the fin pitches fp of the corrugated fin 20. Also, a fin height A of the corrugated fin 19 is configured to be identical with a fin height A of the corrugated fin 20. The fin height A corresponds to a dimension between and end of the peak 31 and an end of the valley 30 in the projection direction of the peaks 31 or the valleys 30.
The corrugated fin 19 is joined to an outer surface of each of the tubes 2, 3 by brazing at the peaks 31 or at the valleys 30, and the corrugated fin 20 is joined to an outer surface of each of the tubes 4, 5 by brazing at the peaks 31 or at the valleys 30. The corrugated fins 19 are arranged relative to the corrugated fins 20 in the air flow direction X. In other words, the corrugated fins 19 are disposed downstream of the corrugated fins 20. The corrugated fin 19 (20) has side surface portions 32, part of which is cut and raised to form a louver 32 a thereon.
There is formed a clearance between the corrugated fins 19, 20. However, the corrugated fins 19, 20 are integrally formed by being connected through multiple connection members 40 in order to limit the number of components from increasing. Each of the connection member 40 has a connection dimension C that is greater than the fin height A. The connection dimension C corresponds to a dimension of a part of the connection member 40, by which dimension the connection member 40 connects the corrugated fins 19, 20. The connection member 40 provides connection between the peak 31 of the corrugated fin 19 and the adjacent peak 31 of the corrugated fin 20 or provides connection between the valley 30 of the corrugated fin 19 and the adjacent valley 30 of the corrugated fin 20 as shown in FIG. 4. In other words, each of the valley 30 and peak 31 may be both named as a fin crest 30, 31, and the connection member 40 provides connection between the fin crest of the corrugated fin 19 and the adjacent fin crest of the corrugated fin 20, for example. FIG. 4 is a perspective view of the tubes 2, 4 and the part of the fins 19, 20 that are connected by the connection member 40 at the corresponding peaks 31 as an example. Also, FIG. 5 is a cross-sectional view of the fin 19 or 20 for illustrating the connection dimension C that spans one side surface portion 32 to the adjacent surface portion 32 when the fin 19 or 20 is corrugated. In other words, the connection member 40 is provided to the fin 19 (20) and extends from a part of the side surface portion 32 of the fin 19 (20) to a part of the adjacent side surface portion 32 of the fin 19 (20) to span the fin crest, for example. For example, the first fin 19 includes a plurality of side surface portions 32, and each of which is integrally coupled to an adjacent side surface portions 32 through a corresponding fin crest 30 or 31 to form the corrugation of the first fin 19. Also, the second fin 20 includes a plurality of side surface portions 32, and each of which is integrally coupled to an adjacent side surface portions 32 through a corresponding fin crest 30 or 31 to form the corrugation of the second fin 20. Each of the plurality of connection members 40 is configured to have a shape or a U-shape cross section (see FIG. 5) such that the shape of the connection member 40 matches the corrugation or a shape of the first fin 19 and the corrugation or a shape of the second fin 20 as show in FIG. 5.
It is noted that the corrugated fins 19, 20 and the tubes 2, 3, 4, 5 constitutes a heat exchanger core.
FIG. 6 is a development of the corrugated fins 19, 20. The multiple connection members 40 are arranged by constant dimensions B, and a ratio of the connection dimension C relative to the constant dimension B is set equal to or less than 0.3. Note that the constant dimension B is named as a connection pitch B.
Then, an experimental result for examining effects of the present embodiment is described below.
FIG. 7 is a diagram illustrating a result of a vibration response test under a condition of the fin height A of 5 mm and the connection pitch B of 60 mm. In FIG. 7, an ordinate axis indicates a rigidity G of the heat exchanger core, and an abscissa axis indicates a connection dimension C. The rigidity G of the heat exchanger core is indicated by a percentage and corresponds to a normalized rigidity of the heat exchanger core relative to a reference rigidity of the heat exchanger core. Note that the reference rigidity is defined under a condition, where the connection dimension C is 2 mm in the present embodiment.
A dotted line S1 corresponds to a rigidity under a condition, where the side surface portions 32 of the corrugated fin 19 are connected with the side surface portions 32 of the corrugated fin 20, and a dotted line S2 corresponds to a rigidity under another condition, where the valleys 30 of the corrugated fin 19 are connected with the valleys 30 of the corrugated fin 20, or where the peaks 31 of the corrugated fin 19 are connected with the peaks 31 of the corrugated fin 20.
As the dotted lines S1, S2 apparently show, the rigidity under the condition, where the valleys 30 (or the peaks 31) of the corrugated fins 19, 20 are mutually connected with each other is greater than the rigidity under the condition, where the side surface portions 32 of the corrugated fins 19, 20 are mutually connected with each other.
FIG. 8 is a diagram illustrating a comparison of noise values between two cases. In one of the two cases, the side surface portions 32 of the corrugated fins 19, 20 are connected with each other under a condition of the connection dimension C=2 mm and the fin height A=5 mm. In the other one of the two cases, the valleys 30 (or the peaks 31) of the corrugated fins 19, 20 are connected with each other under a condition of the connection dimension C=6 mm and the fin height A=5 mm.
At each of vibration frequencies of each of 4.5 kHz, 6.5 kHz, and 7.8 kHz, a noise value under the connection dimension C of 6 mm is smaller compared with a noise value under the connection dimension C of 2 mm.
FIG. 9 is a chart having an ordinate axis indicating a blown-away critical wind velocity (m/s) and an abscissa axis indicating a connection dimension C/a constant dimension B by a unit of %. In an region, where C/B exceeds 30% (see FIG. 10), the blown-away critical wind velocity starts descending. The blown-away critical wind velocity corresponds to a wind velocity, at which the condensate starts to be blown away or shed as droplets of water from the corrugated fin 20 toward the downstream side. FIG. 10 illustrates a development of the corrugated fins 19, 20 when C/B=30%.
According to the above present embodiment, the connection member 40 connects the valley 30 of the corrugated fin 19 and the valley 30 of the corrugated fin 20. Alternatively, the connection member 40 connects the peak 31 of the corrugated fin 19 and the peak 31 of the corrugated fin 20. As a result, the rigidity of the heat exchanger core is limited from decreasing. Thus, the sound of passing refrigerant is limited from being generated.
Also, in the present embodiment, the ratio of the connection dimension C relative to the constant dimension B is set equal to or smaller than 0.3. Thus, the condensate is limited from being blown away as water droplet from the corrugated fin 20 toward the downstream side.
In a case, where tubes and tanks are integrally formed by using a plate material, thickness of the tubes is required to be thinner in order to improved performance of heat exchange, but thickness of the tanks is required to be a certain amount in order to maintain compressive strength.
In the present embodiment, the tank members 8, 9, 11, 12 and the tubes 2, 3, 4, 5 are separately formed in advance and are connected with by brazing. As a result, the tank members 8, 9, 11, 12 are enabled to more effectively have wall thickness different from wall thickness of the tubes 2, 3, 4, 5.

Second Embodiment

In the above first embodiment, the corrugated fins 19, 20 are connected with each other using the connection member 40 by a connecting length of the constant width C. However, the present invention is not limited to the above, and in the second embodiment, the connection member 40 may include three connection sections defining two clearances 51 therebetween as shown in FIG. 11 provided that the connection dimension C is greater than the fin height A.
In the above case, a total of connection dimensions C1, C2, C3 (i.e., C1+C2+C3) of the connection member 40 is greater than the fin height A. In the above case, the total of the connection dimensions C1, C2, C3 correspond to the connection dimension C.

Other Embodiment

In the above first embodiment, inner-fin-type tubes are used. However, extrusion-mold tubes, which are formed by extrusion molding, may be alternatively used in place of the inner-fin-type tubes as shown in FIG. 12.
The above first embodiment is described using an example of the evaporator, in which the tubes 4 on the airflow upstream side are spaced away from the tubes 2 on the airflow downstream side, and in which the tubes 5 on the airflow upstream side are spaced away from the tubes 3 on the airflow downstream side. Instead, alternatively, the tubes 4 (5) may be partially connected with the tubes 2 (3), respectively, as shown in FIG. 13.
In the above first embodiment, the tubes 4 (5) corresponding to the second tube are arranged upstream of the tubes 2 (3) corresponding to the first tube in the airflow direction, and a group of tubes 4 (5) is spaced away from the other group of the tubes 2 (3) in the air flow direction. However, the present invention is not limited to the above. For example, three or more groups of tubes may be alternatively arranged side by side in the air flow direction.
In the above first embodiment, a heat exchanger core of the present invention is applied to the evaporator. However, the present invention is not limited to the above. For example, the heat exchanger core of the present invention may be applied to a cooling unit having a condenser for a refrigeration cycle apparatus and a radiator that is integrally formed with the condenser.
In the above configuration, one of the first and second tubes corresponds to a tube of the condenser, through which tube refrigerant flows. The other one of the first and second tubes corresponds to a tube of the radiator, through which tube engine coolant flows. In other words, one of the first and second fluids corresponds to refrigerant, and the other one corresponds to engine coolant. Thus, the first and second fluids are mutually different from each other.
In the above case, fins for the condenser and fins for the radiator are connected by connection members at peaks or connected by connection members at valleys. As a result, rigidity of the heat exchanger core is enabled to be increased.
The tubes 2, 3 correspond to first tubes, the tubes 4, 5 correspond to second tubes, the fin 19 corresponds to a first fin, and the fin 20 corresponds to a second fin. The distribution tank chamber 81 and the tank member 9 correspond to a first tank, and the collection tank chamber 82 and the tank member 9 correspond to a second tank. The distribution tank chamber 110 and the tank member 12 corresponds to a third tank, and the collection tank chamber 111 and the tank member 12 correspond to a fourth tank.
Additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader terms is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described.

Claims

1. A heat exchanger core comprising:

a first tube configured to carry a first fluid flowing therethrough to cause heat exchange between the first fluid and air;

a second tube provided upstream of the first tube in a direction of air flow, the second tube carrying a second fluid flowing therethrough to cause heat exchange between the second fluid and air;

a first fin that is coupled to an outer surface of the first tube for facilitating heat exchange of the first tube, the first fin having a series of corrugations to have a peak and a valley;

a second fin that is coupled to an outer surface of the second tube for facilitating heat exchange of the second tube, the second fin having a series of corrugations to have a peak and a valley, the second fin being located upstream of the first fin in the airflow direction and apart from the first fin to define a clearance therebetween; and

a connection member that is configured to connect the first fin with the second fin, wherein:

the connection member connects the peak of the first fin with the peak of the second fin or connects the valley of the first fin with the valley of the second fin.

2. The heat exchanger core according to claim 1, wherein:

the first and second fins are configured to have an identical fin pitch and an identical fin height with each other; and

the connection member has a connection dimension that is larger than the fin height of the first and second fins.

3. The heat exchanger core according to claim 2, wherein:

the connection member is one of a plurality of connection members that are provided between the first and second fins at intervals of a constant dimension; and

a ratio of the connection dimension relative to the constant dimension is set equal to or less than 0.3.

4. The heat exchanger core according to claim 1, wherein the first fluid flowing through the first tube is identical with the second fluid flowing through the second tube.

5. A heat exchanger comprising:

the heat exchanger core according to claim 1;

a plurality of first tubes;

a plurality of second tubes;

a first tank configured to distribute fluid to each of the plurality of first tubes;

a second tank configured to collect fluid flowing out of each of the plurality of first tubes;

a third tank configured to distribute fluid to each of the plurality of second tubes; and

a fourth tank configured to collect fluid flowing out of each of the plurality of second tubes, wherein:

the plurality of first tubes is in fluid communication with the first and second tanks; and

the plurality of second tubes is in fluid communication with the third and fourth tanks.

6. An evaporator for a refrigeration cycle apparatus comprising:

a heat exchanger according to claim 5, wherein:

the first and second tubes carry refrigerant as fluid flowing therethrough; and

the refrigerant evaporates by absorbing heat from air.

7. A heat exchanger core comprising:

a first fin that is coupled to an outer surface of the first tube for increasing a heat exchange contact area of the first tube with air, the first fin having a series of corrugations to form a plurality of fin crests;

a second fin that is coupled to an outer surface of the second tube for increasing a heat exchange contact area of the second tube with air, the second fin having a series of corrugations to form a plurality of fin crests, the second fin being spaced away from the first fin in the airflow direction to define a clearance therebetween; and

a plurality of connection members, each of which is configured to connects the first and second fins to span the clearance, wherein:

each of the plurality of connection members connects one of the plurality of fin crests of the first fin with an adjacent one of the plurality of fin crests of the second fin; and

the plurality of connection members is arranged at predetermined intervals.

8. The heat exchanger core according to claim 7, wherein:

the first fin includes a plurality of side surface portions, each of which is integrally coupled to an adjacent one of the side surface portions through a corresponding fin crest to form the corrugation of the first fin;

the second fin includes a plurality of side surface portions, each of which is integrally coupled to an adjacent one of the side surface portions through a corresponding fin crest to form the corrugation of the second fin; and

each of the plurality of connection members is configured to have a shape such that the shape of the connection member matches the corrugation of the first fin and the corrugation of the second fin.