Patent Description:
PTL <NUM> discloses a plate-fin heat exchanger. The plate-fin heat exchanger includes a plurality of plate fins layered with a gap therebetween. Each of the plate fins includes a first header flow channel, a second header flow channel, and a heat transfer flow channel. The plate fin includes a pair of plates which are brazed to face each other. The plate fin allows a first fluid such as a refrigerant to flow from the first header flow channel to the second header flow channel via the heat transfer flow channel, and promotes heat exchange between the first fluid flowing through the heat transfer flow channel and a second fluid such as air flowing through a gap between the plate fins.

<CIT> discloses a plate-fin heat exchanger according to the preamble of claim <NUM> and describes a heat exchanger comprising a multiplicity of longitudinally extending flattened tube structures disposed in a longitudinal coextensive array with fin structures bonded in abutting relation between adjacent pairs of tube structures. First and second header assemblies are connected with first and second end portions respectively of each tube structure and provide a fluid inlet for receiving a first fluid for passage through the tube structures during the passage of a second fluid through the fin structures. The first fluid passes from the second header assembly through a fluid outlet. Each header assembly is formed of a series of interconnected header structures, each of which comprises a pair of sheet metal plates formed to provide first marginal edge portions sealingly fixed in abutting relation with the exterior periphery of the associated tube structure end portion and wall portions spaced in a direction perpendicular to the longitudinal direction of extent of the tube structures having aligned openings therein. The remainder of the marginal edge portions of the plates are sealingly fixed in abutting engagement which together with the first marginal edge portions surround the openings and define with the spaced portions an enclosed first fluid containing volume communicating the interior of the associated tube structure end portion with the openings. Each spaced portion of each pair of sheet metal plates is sealingly fixed to a spaced portion of an adjacent pair of sheet metal plates along peripheries defining the openings therein.

Other plate-fin heat exchangers are described in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

The present disclosure solves the problems caused by the conventional plate fin configuration, and provides a plate-fin heat exchanger that is lightweight and highly reliable and has high performance, and a refrigeration system using the plate-fin heat exchanger.

A plate-fin heat exchanger according to the present invention is defined in appended claim <NUM>. Among others, it includes a plate fin including a first header flow channel, a second header flow channel, and a heat transfer flow channel connected between the first and second header flow channels, the plate fin including a first header region having the first header flow channel, a second header region having the second header flow channel, and a flow channel region having the heat transfer flow channel, wherein the first and second header regions are each constituted by two joined plates each having a header flow channel opening, the flow channel region is constituted by a single flow channel plate in which the heat transfer flow channel is integrally formed, and the first and second header regions are integrally joined to the flow channel region.

In the plate-fin heat exchanger according to the present invention, the flow channel region is constituted by a single plate in which the heat transfer flow channel is integrally formed due to the above configuration. The joining portions are located only in the first and second header regions, and thus, can be minimized. Therefore, the reliability of the heat exchanger is improved. In addition, the flow channel region constituted by a single plate has reduced weight and reduced thickness as compared with a flow channel region constituted by two joined plates. The reduction in thickness enables reduction in flow resistance of the second fluid flowing between the plate fins. As described above, a plate-fin heat exchanger which is highly reliable, is lightweight, and has high performance and a refrigeration system using the plate-fin heat exchanger are provided.

As disclosed in PTL <NUM>, each of plate fins of a plate-fin heat exchanger includes two plates brazed to face each other. Each plate includes a header flow channel opening and a recessed groove for a heat transfer flow channel. Such a plate fin is likely to cause a joining defect due to a large number of joining portions and the complexity of the flow channel configuration. Therefore, there is a problem that it is necessary to improve reliability by reducing joining defects. Further, since the plate fin includes two joined plates, the plate fin is large in thickness, so that a gap between the plate fins decreases. Therefore, there is also a problem that the flow resistance of a fluid flowing through the gap between the plate fins is increased to deteriorate heat exchange performance, and the weight of the entire heat exchanger increases.

The inventors of the present disclosure have found that there are problems as described above, and arrived at the subject matter of the present disclosure in order to solve the problems.

The present disclosure provides a plate-fin heat exchanger which is highly reliable, is lightweight, and has high performance and a refrigeration system using the plate-fin heat exchanger.

Exemplary embodiments will be described in detail below with reference to the drawings. However, detailed descriptions more than necessary may be omitted. For example, a detailed description of well-known matters, and a duplicate description of substantially identical configurations may not be provided. This is to avoid an unnecessarily redundant description below and to facilitate understanding of a person skilled in the art.

The accompanying drawings and the following description are provided to help those skilled in the art to fully understand the present disclosure and are not intended to limit the subject matter recited in the appended claims.

A first exemplary embodiment will now be described with reference to <FIG>.

As illustrated in <FIG>, heat exchanger <NUM> according to the present exemplary embodiment includes plate-fin layered body <NUM>, end plate 3a joined to an upper surface of plate-fin layered body <NUM>, and end plate 3b joined to a lower surface of plate-fin layered body <NUM>. Plate-fin layered body <NUM> is joined to and integrated with end plates 3a and 3b. End plates 3a and 3b have substantially the same shape as plate-fin layered body <NUM> in planar view. Heat exchanger <NUM> has tube <NUM> and tube <NUM> that are connected to end plate 3a. Tube <NUM> serves as an inlet when heat exchanger <NUM> is used as a condenser and serves as an outlet when heat exchanger <NUM> is used as an evaporator. Conversely, tube <NUM> serves as an outlet when heat exchanger <NUM> is used as a condenser and serves as an inlet when heat exchanger <NUM> is used as an evaporator.

End plates 3a and 3b on both sides of plate-fin layered body <NUM> are joined to plate-fin layered body <NUM> by brazing while sandwiching plate-fin layered body <NUM>. End plates 3a and 3b are connected to each other at both ends in the longitudinal direction of end plates 3a and 3b by fastening means <NUM> to maintain rigidity as a heat exchanger.

As illustrated in <FIG> and <FIG>, plate fin 2a has heat transfer flow channels <NUM> through which a first fluid (hereinafter referred to as a refrigerant) such as a refrigerant flows. In plate-fin layered body <NUM>, a gap through which a second fluid (hereinafter referred to as air) such as air flows is formed between layered plate fins 2a. Plate-fin layered body <NUM> promotes heat exchange between the refrigerant flowing through heat transfer flow channels <NUM> provided in plate fins 2a and air flowing through a gap formed between layered plate fins 2a.

As illustrated in <FIG>, plate fin 2a includes first header region 11a, second header region 11b, and flow channel region <NUM>. First header region 11a has first header flow channel <NUM> connected to tube <NUM>. Second header region 11b has second header flow channel <NUM> connected to tube <NUM>. Flow channel region <NUM> has heat transfer flow channels <NUM> connecting first header flow channel <NUM> and second header flow channel <NUM>. First and second header regions 11a and 11b are integrally joined to flow channel region <NUM>.

First and second header regions 11a and 11b have substantially the same shape. First header region 11a will be described below. In order to avoid redundant description, the description of second header region 11b may be omitted. As illustrated in <FIG>, first header region 11a includes first plate 16a and second plate 16b that are brazed to face each other. First plate 16a includes header flow channel opening 9a (10a), ring-shaped recessed groove <NUM> formed in an outer periphery of header flow channel opening 9a, communication-path recessed groove <NUM> extending from ring-shaped recessed groove <NUM>, and flow channel cover <NUM> connected to communication-path recessed groove <NUM>. Second plate 16b has header flow channel opening 9a (10a) and ring-shaped recessed groove <NUM> formed in an outer periphery of header flow channel opening 9a. In this example, first header region 11a includes connection member <NUM> that connects first plate 16a and second plate 16b. Connection member <NUM> is bent, so that first plate 16a faces second plate 16b.

On the other hand, flow channel region <NUM> is constituted by single flow channel plate <NUM>. Flow channel plate <NUM> is provided with heat transfer flow channels <NUM> that are formed integrally with flow channel plate <NUM> by extrusion process in this example. The left end of flow channel plate <NUM> is held between first plate 16a and second plate 16b of first header region 11a, and is integrated with first header region 11a by brazing. Similarly, the right end of flow channel plate <NUM> is integrated with second header region 11b by brazing.

A connecting and joining configuration for connecting first header region 11a and flow channel region <NUM> will be described in more detail with reference to <FIG> as an example. Flow channel region <NUM> includes heat transfer flow channel formation portions 12a and fin portions 12b. Heat transfer flow channel formation portions 12a are seamless tubes or pipes, and heat transfer flow channels <NUM> are formed therein. Heat transfer flow channel formation portions 12a each have first end part 12ab protruding further to first header region 11a from fin portions 12b. First end part 12ab is sandwiched between flow channel cover <NUM> provided in first plate 16a of first header region 11a and a flat surface portion of second plate 16b, and is connected to first header region 11a by brazing. Second header region 11b is also connected to flow channel region <NUM> by basically the same connecting and joining configuration. As illustrated in <FIG>, heat transfer flow channel formation portions 12a each have second end part 12ac opposite to first end part 12ab. Second end part 12ac is sandwiched between flow channel cover <NUM> provided in first plate 16a of second header region 11b and a flat surface portion of second plate 16b, and is connected to second header region 11b by brazing. With this configuration, a series of paths connecting first header flow channel <NUM> and second header flow channel <NUM> are formed by flow channel cover <NUM> of first plate 16a and first end parts 12ab of heat transfer flow channel formation portions 12a of flow channel plate <NUM>.

First and second header regions 11a and 11b each have protruding ribs <NUM> on the flat surface portion. As illustrated in <FIG>, when plate fins 2a are layered, protruding ribs <NUM> abut on flow channel cover <NUM> of adjacent plate fin 2a and press flow channel cover <NUM> against first end parts 12ab of heat transfer flow channel formation portions 12a.

In addition, as illustrated in <FIG>, heat transfer flow channels <NUM> of flow channel region <NUM> are extruded as a pair of two rows in this example. As shown in <FIG>, flow channel region <NUM> has protrusions 12c for allowing the air flowing through the gap between layered plate fins to meander on the back surfaces of fin portions 12b between heat transfer flow channel formation portions 12a.

Further, the plurality of heat transfer flow channels <NUM> arranged in parallel are connected by auxiliary communication flow paths <NUM> recessed in first and second header regions 11a and 11b, respectively, and turn back between first header flow channel <NUM> and second header flow channel <NUM>.

End plates 3a and 3b and plate fins 2a are made of aluminum or an aluminum alloy.

Next, the operation and effect of the plate-fin heat exchanger configured as described above will be described by taking, as an example, a case where the plate-fin heat exchanger is used as a heat exchanger of an air conditioner.

When heat exchanger <NUM> according to the present exemplary embodiment is used, for example, under a condensation condition, a refrigerant in a gas phase state flows into first header flow channels <NUM> on an inlet side of plate-fin layered body <NUM> through tube <NUM>. The gas-phase refrigerant flowing into first header flow channels <NUM> flows while turning back through heat transfer flow channels <NUM> of plate fins 2a, and flows out through tube <NUM> to a refrigerant circuit of a refrigeration system via second header flow channels <NUM> on the outlet side. The gas-phase refrigerant sequentially transitions into a liquid phase by heat exchange with air passing through the gaps between layered plate fins while flowing through heat transfer flow channels <NUM>.

Here, first and second header regions 11a and 11b each include two plates which are first plate 16a and second plate 16b and which are joined by brazing. Flow channel region <NUM> includes single flow channel plate <NUM> having heat transfer flow channels <NUM> formed therein by extrusion process. Therefore, in heat exchanger <NUM>, the joining portions by brazing are located only in first and second header regions 11a and 11b, and thus can be minimized. Accordingly, the reliability of heat exchanger <NUM> can be significantly enhanced.

On the other hand, flow channel region <NUM> of plate fin 2a is composed of single flow channel plate <NUM> having heat transfer flow channels <NUM> formed therein by extrusion process. The thickness of each fin portion 12b of flow channel region <NUM> is smaller than the total thickness of brazed first and second plates 16a and 16b of header region <NUM>. As illustrated in <FIG>, each of heat transfer flow channel formation portions 12a of flow channel region <NUM> has thickness t. First and second header regions 11a and 11b each are constituted by joined first and second plates 16a and 16b, and have thickness T in communication -path recessed groove <NUM>. Thickness T corresponds to a thickness of a portion having a conventional heat transfer flow channel formed by joining two plates. Thickness t is smaller than thickness T.

Therefore, gap L, which is an air passage, between flow channel regions <NUM> of layered plate fins illustrated in <FIG> can be made wider as compared with a prior art. Thus, the flow resistance of air can be reduced, and the performance of heat exchanger <NUM> can be enhanced. In addition, heat exchanger <NUM> enables air to meander as indicated by dashed arrow Y by protrusions 12c protruding to gap L between flow channel regions <NUM> of layered plate fins, whereby the performance of heat exchanger <NUM> can be further enhanced.

Further, plate fin 2a is reduced in weight due to reduction in thickness of flow channel region <NUM>. Therefore, the weight of entire heat exchanger <NUM> can be significantly reduced, whereby weight saving can be achieved.

As illustrated in <FIG>, first header region 11a is connected to flow channel region <NUM> such that first end parts 12ab of heat transfer flow channel formation portions 12a are sandwiched between flow channel cover <NUM> provided in first plate 16a of first header region 11a and the flat surface portion of second plate 16b. Similarly, second header region 11b is connected to flow channel region <NUM>. As a result, first and second header regions 11a and 11b can be easily connected to flow channel region <NUM>, and connection by brazing can be ensured with joining defects being suppressed.

In the present exemplary embodiment, each of first and second header regions 11a and 11b has protruding ribs <NUM> on the flat surface portion of second plate 16b. When plate fins 2a are layered, protruding ribs <NUM> press flow channel cover <NUM> of adjacent plate fin 2a. The first fluid applies pressure (plate releasing pressure) in a direction of releasing first plate 16a from second plate 16b at the joint portion between flow channel cover <NUM> and first end parts 12ab of heat transfer flow channel formation portions 12a. Protruding ribs <NUM> can apply pressure against the plate releasing pressure to first plate 16a, so that first and second plates 16a and 16b are kept firmly joined to each other. As a result, the reliability can be further improved by enhancing the airtightness at the joint portion, between flow channel cover <NUM> and first end parts 12ab of heat transfer flow channel formation portions 12a, through which the first fluid flows.

Further, in each of first and second header regions 11a and 11b, first plate 16a and second plate 16b are connected by connection member <NUM>. First plate 16a and second plate 16b are managed as one component, and thus, a number of components can be reduced, and parts management can be facilitated.

In the present exemplary embodiment, first header region 11a includes first header flow channel <NUM>. Second header region 11b has second header flow channel <NUM>. First header region 11a and second header region 11b are located at opposite ends of plate fin 2a, respectively. However, the configuration is not limited thereto, and as shown in <FIG>, plate fin 2a may include header region <NUM>, auxiliary flow channel region <NUM>, and flow channel region <NUM> connected between header region <NUM> and auxiliary flow channel region <NUM>. Header region <NUM> includes first header flow channel <NUM> and second header flow channel <NUM>. Auxiliary flow channel region <NUM> has communication path <NUM> connecting heat transfer flow channels <NUM>. As described above, first header flow channel <NUM> and second header flow channel <NUM> may be provided at one end of plate fin 2a.

The same effects as described above can also be obtained by the configuration described above in which first header flow channel <NUM> and second header flow channel <NUM> are provided at one end of plate fin 2a. In addition, first header flow channel <NUM> and second header flow channel <NUM> are disposed at one end of plate fin 2a, so that tubes of a refrigeration system can be connected to first header flow channel <NUM> and second header flow channel <NUM> at one place.

As described above, the plate-fin heat exchanger according to the present disclosure includes plate fin 2a including first header flow channel <NUM>, second header flow channel <NUM>, and heat transfer flow channel <NUM> connected between first and second header flow channels <NUM> and <NUM>, plate fin 2a including first header region 11a having first header flow channel <NUM>, second header region 11b having second header flow channel <NUM>, and flow channel region <NUM> having heat transfer flow channel <NUM>, wherein first and second header regions 11a and 11b are each constituted by two joined plates 16a and 16b each having a header flow channel opening, flow channel region <NUM> is constituted by single flow channel plate <NUM> in which heat transfer flow channel <NUM> is integrally formed, and first and second header regions 11a and 11b are integrally joined to flow channel region <NUM>.

As a result, flow channel region <NUM> is constituted by single flow channel plate <NUM> in which heat transfer flow channel <NUM> is integrally formed. The joining portions are located only in first and second header regions 11a and 11b. That is, the joining portions by brazing or the like can be minimized. Therefore, the reliability of heat exchanger <NUM> can be enhanced. Flow channel region <NUM> constituted by single flow channel plate <NUM> can reduce the flow resistance of the second fluid due to reduced weight and reduced thickness as compared with a flow channel region constituted by two joined plates. As a result, it is possible to provide a plate-fin heat exchanger that is lightweight, has high performance, and is highly reliable.

Further, the plate-fin heat exchanger according to the present disclosure includes plate fin 2a including first header flow channel <NUM>, second header flow channel <NUM>, and a plurality of heat transfer flow channels <NUM> connected in series between first and second header flow channels <NUM> and <NUM>, plate fin 2a including header region <NUM> having first and second header flow channels <NUM> and <NUM>, flow channel region <NUM> having the plurality of heat transfer flow channels <NUM>, and auxiliary flow channel region <NUM> having communication path <NUM> connecting the plurality of heat transfer flow channels <NUM>, wherein header region <NUM> is integrally joined to a first end of flow channel region <NUM>, and auxiliary flow channel region <NUM> is integrally joined to a second end opposite to the first end of flow channel region <NUM>.

With this configuration, first and second header flow channels <NUM> and <NUM> are gathered near the first end of plate fin 2a of heat exchanger <NUM>. As described above, the weight of the heat exchanger can be reduced, reliability and performance can be improved, and the work of connecting tubes of a refrigeration system to first and second header flow channels <NUM> and <NUM> can be facilitated.

Further, flow channel region <NUM> may have heat transfer flow channel formation portion 12a for forming heat transfer flow channel <NUM>, heat transfer flow channel formation portion 12a may have first end part 12ab and second end part 12ac opposite to the first end part, first end part 12ab may be sandwiched between two plates 16a and 16b of first header region 11a, and second end part 12ac may be sandwiched between two plates 16a and 16b of second header region 11b.

As a result, first and second header regions 11a and 11b can be easily connected to flow channel region <NUM> by brazing, and the brazing can be made robust and secure.

Flow channel region <NUM> may have a plurality of heat transfer flow channel formation portions 12a for forming the plurality of heat transfer flow channels <NUM>, each of the plurality of heat transfer flow channel formation portions 12a may have first end part 12ab and second end part 12ac opposite to first end part 12ab, header region <NUM> may be constituted by two joined plates 16a and 16b, first end part 12ab of each of the plurality of heat transfer flow channel formation portions 12a may be sandwiched between two joined plates 16a and 16b of header region <NUM>, auxiliary flow channel region <NUM> may be constituted by two joined plates 16a and 16b, and second end part 12ac of each of the plurality of heat transfer flow channel formation portions 12a may be sandwiched between two joined plates 16a and 16b of auxiliary flow channel region <NUM>.

As a result, header region <NUM> can be easily connected to flow channel region <NUM> by brazing, and the brazing can be made robust and secure. In addition, auxiliary flow channel region <NUM> and flow channel region <NUM> can be easily connected by brazing, and the brazing can be made robust and secure.

A second exemplary embodiment will be described below with reference to <FIG>.

<FIG> is a diagram illustrating a refrigeration cycle of an air conditioner equipped with the plate-fin heat exchanger according to the first exemplary embodiment, and <FIG> is a schematic sectional view illustrating an indoor unit of the air conditioner.

In <FIG>, the air conditioner includes outdoor unit <NUM> and indoor unit <NUM> connected to outdoor unit <NUM>. Outdoor unit <NUM> is provided with compressor <NUM> for compressing a refrigerant, four-way valve <NUM> for switching a refrigerant circuit during cooling and heating operations, outdoor heat exchanger <NUM> that exchanges heat between the refrigerant and outdoor air, decompressor <NUM> for decompressing the refrigerant, and outdoor blower <NUM>. Indoor unit <NUM> is provided with indoor heat exchanger <NUM> for exchanging heat between the refrigerant and indoor air, and indoor blower <NUM>. Indoor heat exchanger <NUM> is the plate-fin heat exchanger described in the first exemplary embodiment. Compressor <NUM>, four-way valve <NUM>, indoor heat exchanger <NUM>, decompressor <NUM>, and outdoor heat exchanger <NUM> are connected via the refrigerant circuit to define a heat-pump refrigeration cycle.

In the air conditioner having the above configuration, during cooling operation, four-way valve <NUM> is switched such that the discharge side of compressor <NUM> and outdoor heat exchanger <NUM> communicate with each other. Thus, the refrigerant compressed by compressor <NUM> transitions into a high-temperature high-pressure gas-phase refrigerant and is supplied to outdoor heat exchanger <NUM> through four-way valve <NUM>. Then, the refrigerant dissipates heat by heat exchange with outdoor air to transition into a high-pressure liquid-phase refrigerant, and is supplied to decompressor <NUM>. The refrigerant is decompressed by decompressor <NUM> into low-temperature low-pressure two-phase refrigerant, and supplied to indoor unit <NUM>. In indoor unit <NUM>, the refrigerant enters indoor heat exchanger <NUM>, absorbs heat by heat exchange with indoor air, and evaporates to transition into a low-temperature gas refrigerant. During this cycle, the indoor air is cooled, so that an indoor space is cooled. The refrigerant then returns to outdoor unit <NUM>, and is returned back to compressor <NUM> through four-way valve <NUM>.

During heating operation, four-way valve <NUM> is switched such that the discharge side of compressor <NUM> and indoor unit <NUM> communicate with each other. Thus, the refrigerant compressed by compressor <NUM> transitions into a high-temperature high-pressure refrigerant, and is supplied to indoor unit <NUM> through four-way valve <NUM>. The high-temperature high-pressure refrigerant enters indoor heat exchanger <NUM> and dissipates heat by heat exchange with indoor air to transition into a high-pressure liquid refrigerant. During this cycle, the indoor air is heated, so that the indoor space is heated. Then, the refrigerant is supplied to decompressor <NUM>, is decompressed by decompressor <NUM> to transition into a low-temperature low-pressure two-phase refrigerant, is sent to outdoor heat exchanger <NUM>, evaporates by heat exchange with outdoor air, and then, returns to compressor <NUM> through four-way valve <NUM>.

Since the refrigeration system according to the present disclosure uses the heat exchanger described in the first exemplary embodiment as indoor heat exchanger <NUM>, the refrigeration system is lightweight, has high performance, and is highly reliable.

While the plate-fin heat exchanger and the refrigeration system using the plate-fin heat exchanger according to the present disclosure have been described with reference to the exemplary embodiments described above, the present disclosure is not limited thereto, and various modifications, replacements, additions, omissions, and the like are possible. For example, although the case where the first fluid is a refrigerant and the second fluid is air has been described above, the present disclosure is not limited thereto. Although the air conditioner has been described above as the refrigeration system, the refrigeration system may be a refrigerator, a refrigeration case, or a heat pump water heater using water as the second fluid. That is, the exemplary embodiments disclosed herein are illustrative in all respects and are not restrictive, and the scope of the present disclosure is defined by the claims.

Claim 1:
A plate-fin heat exchanger (<NUM>) comprising
a plate fin (2a) including:
a first header flow channel (<NUM>);
a second header flow channel (<NUM>); and
a heat transfer flow channel (<NUM>) connected between the first and second header flow channels (<NUM>, <NUM>),
the plate fin (2a) including:
a first header region (11a) having the first header flow channel (<NUM>);
a second header region (11b) having the second header flow channel (<NUM>); and
a flow channel region (<NUM>) having the heat transfer flow channel (<NUM>),
wherein the first and second header regions (11a, 11b) are each constituted by two joined plates (16a, 16b) each having a header flow channel opening (9a, 10a),
the flow channel region (<NUM>) is constituted by a single plate in which the heat transfer flow channel (<NUM>) is integrally formed, and
the first and second header regions (11a, 11b) are integrally joined to the flow channel region (<NUM>), wherein
the flow channel region (<NUM>) has a heat transfer flow channel formation portion (12a) for forming the heat transfer flow channel (<NUM>), and
the heat transfer flow channel formation portion (12a) has a first end part (12ab) and a second end part (12ac) opposite to the first end part (12ab),
characterized in that
the first end part (12ab) is sandwiched between a flow channel cover (<NUM>) provided in the first plate (16a) of the first header region (11a) and a flat surface portion of the second plate (16b), and connected to the first header region (11a) by brazing; and
the second end part (12ac) is sandwiched between a flow channel cover (<NUM>) provided in the first plate (16a) of the second header region (11b) and a flat surface portion of the second plate (16b), and connected to the second header region (11b) by brazing.