HEAT EXCHANGER
The outer surface of a core pipe 31 is pressed so as to form projections 313 on the inner surface of the core pipe 31, and a winding pipe 32 is helically wound around the outer circumference of the core pipe 31. Subsequently, the core pipe 31 and the winding pipe 32 are bent together, and brazing is performed. As a result, the outer surface of the winding pipe 32 is in contact with the outer surface of the core pipe 31 without any gap therebetween at a bending center portion (D), and the outer surface of the winding pipe (32) is bonded to the outer surface of the core pipe (31) by a brazing material (33) at the bending center portion (D) of the bent part C-C.
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The present invention relates to a heat exchanger. More specifically, the present invention relates to a heat exchanger that includes a core pipe having projections that are formed on an inner surface thereof by pressing the outer surface of the core pipe, and a winding pipe that is wound around the outer surface of the core pipe.
BACKGROUND OF THE INVENTIONSome heat exchangers used for air conditioners, water heaters, and the like are provided with a core pipe that forms a passage of a first fluid, a winding pipe that is wound around the outer surface of the core pipe and forms a passage of a second fluid, and a heat exchanger that exchanges heat between the first fluid and the second fluid. For example, a double pipe heat exchanger is used as a heat exchanger for a water heater such as a heat pump water heater. Such a heat exchanger is formed by two pipes: a core pipe through which water flows and a winding pipe through which the refrigerant flows. These two pipes are spirally wound into an oval shape and used as one heat exchanger unit, and a main body of the heat exchanger is formed by mutually superposing and connecting a number of such heat exchanger units to each other. For forming a main body of a heat exchanger, a technology has been proposed in which a heat exchanger is formed by spirally winding a winding pipe around the outer circumference of a jig that corresponds to a core pipe, pulling out the jig so as to form a winding pipe body, and inserting a core pipe into the winding pipe body. In addition, another technology has been proposed to improve the heat transfer performance of a core pipe used in a heat exchanger. With this technology, projections are provided on the inner surface of the core pipe by pressing the outer surface of the core pipe so as to improve the heat transfer performance (See JP-A Publication No. H06-70556).
SUMMARY OF THE INVENTIONHowever, when a heat exchanger is formed by spirally winding a winding pipe around the outer circumference of a jig, pulling out the jig so as to form a winding pipe body, and inserting a core pipe into the winding pipe body, there is a possibility that a poor contact may be formed between the core pipe and the winding pipe, consequently reducing the heat transfer performance. In particular, when a core pipe having projections that are formed on the inner surface thereof by pressing the outer surface of the core pipe is used as a core pipe of a heat exchanger, since a cross-section at a bent part of such a core pipe has an irregular shape because of the projections, there is a risk that a poor contact may be formed between the core pipe and the winding pipe, consequently reducing the heat transfer performance.
Therefore, an object of the present invention is to overcome the above problem and to improve the heat transfer performance of a heat exchanger that includes a core pipe having projections that are formed on the inner surface thereof by pressing the outer surface of the core pipe, and a winding pipe that is wound around the outer surface of the core pipe. The present invention also aims to provide a method for manufacturing a heat exchanger that has a good heat transfer performance.
A heat exchanger according to a first aspect of the present invention includes a core pipe having projections that are formed on the inner surface thereof by pressing the outer surface of the core pipe and a winding pipe that is wound around the outer surface of the core pipe, wherein the core pipe has a linear part and a bent part; the outer surface of the winding pipe is in contact with the outer surface of the core pipe without any gap therebetween at a bending center portion of the bent part; and the outer surface of the winding pipe is bonded to the outer surface of the core pipe by a brazing material at the bending center portion of the bent part.
Here, the core pipe of the heat exchanger has projections that are formed on the inner surface of the core pipe. Accordingly, the heat transfer coefficient is improved because of the projections provided inside the pipe, which consequently improves the overall performance of the heat exchanger. On the other hand, when the winding pipe is wound around the core pipe and then the core pipe is spirally wound into an oval shape, since a cross-section at the bent part of the core pipe has an irregular shape because of the projections, there is a risk that a poor contact may be formed between the core pipe and the winding pipe, consequently reducing the heat transfer performance. However, with the heat exchanger of the present invention, the outer surface of the winding pipe is in contact with the outer surface of the core pipe without any gap therebetween at the bending center portion of the bent part, and also, the outer surface of the winding pipe is bonded to the outer surface of the core pipe by the brazing material at the bending center portion of the bent part. Therefore, improved contact between the core pipe and the winding pipe is formed at least at the bending center portion of the bent part, which consequently improves the heat transfer performance.
A method for manufacturing a heat exchanger according to a second aspect of the present invention is a method for manufacturing a heat exchanger having a core pipe and a winding pipe, the method including the steps of: pressing the outer surface of the core pipe so as to form projections on the inner surface; winding the winding pipe around the outer surface of the core pipe; bending the core pipe with the winding pipe being wound around the outer surface of the core pipe; and brazing the outer surface of the winding pipe to the outer surface of the core pipe by a brazing material.
When a part provided with the projections is bent, since a cross-section at the bent part of the core pipe has an irregular shape because of the projections, there is usually a risk that a poor contact may be formed between the core pipe and the winding pipe, consequently reducing the heat transfer performance. However, with the present invention, the outer surface of the core pipe is pressed so as to form the projections on the inner surface, and the winding pipe is wound around the outer surface of the core pipe, and then, with the winding pipe being wound around the outer surface of the core pipe, the core pipe and the winding pipe are bent together using a jig or like in order to bend the core pipe. Such a method allows the outer surface of the winding pipe to be in contact with the outer surface of the core pipe without any gap therebetween at least at the bending center portion of the bent part that comes into contact with a jig. Therefore, at least at the bending center portion of the bent part, improved contact between the core pipe and the winding pipe is formed, which consequently improves the heat transfer performance.
In addition, when a part provided with the projections is bent, a large deformation and breakage may occur at a concave portion on the outer surface of the core pipe during the bending process. Therefore, conventionally, the bent part is not provided with the projections, and thus improvement of the heat transfer performance by means of the projections has not been achieved at the bent part. However, when the core pipe and the winding pipe are bent together with the winding pipe being wound around the outer surface of the core pipe, the overall strength increases so that it is possible to prevent a large deformation and breakage at a concave portion on the outer surface of the core pipe during the bending process, even if the bent part is provided with the projections.
Further, it is possible to improve the heat transfer performance by brazing the outer surface of the winding pipe to the outer surface of the core pipe by the brazing material in order to bond the core pipe to the winding pipe in the brazing process.
A heat exchanger according to a third aspect of the present invention is the heat exchanger according to the first aspect of the present invention, the heat exchanger including the core pipe having the projections that are formed on the inner surface thereof by pressing the outer surface of the core pipe, the winding pipe that is wound around the outer surface of the core pipe, and the brazing material by which the outer surface of the winding pipe is brazed to the outer surface of the core pipe, wherein the core pipe includes a bent part that is formed by bending the core pipe with the winding pipe being wound around the outer surface of the core pipe.
In this aspect of the invention, the core pipe has a linear part and a bent part. In addition, the bent part is formed by bending the core pipe with the winding pipe being wound around the outer surface of the core pipe, so that it is possible to wind the winding pipe such that the outer surface of the winding pipe comes into contact with the outer surface of the core pipe without any gap therebetween at the bending center portion of the bent part.
The heat exchanger according to the first aspect of the present invention is provided with the projections on the inner surface of the core pipe of the heat exchanger. Accordingly, the heat transfer coefficient will improve because of the projections provided inside the pipe, and the overall performance of the heat exchanger will consequently improve. In addition, when the winding pipe is wound around the core pipe and then the core pipe is spirally wound into an oval shape, since a cross-section at the bent part of the core pipe has an irregular shape due to the projections, there is a risk that a poor contact may be formed between the core pipe and the winding pipe, consequently reducing the heat transfer performance. However, with the heat exchanger of the present invention, the winding pipe is wound such that the outer surface of the winding pipe comes into contact with the outer surface of the core pipe without any gap therebetween at the bending center portion of the bent part, and also, the outer surface of the winding pipe is bonded to the outer surface of the core pipe by the brazing material at the bending center portion of the bent part. Therefore, a poor contact between the core pipe and the winding pipe will not be formed at least at the bending center portion of the bent part, which consequently improves the heat transfer performance.
The method for manufacturing a heat exchanger according to the second aspect of the present invention includes: pressing the outer surface of the core pipe so as to form the projections on the inner surface; winding the winding pipe around the outer surface of the core pipe; and, with the winding pipe being wound around the outer surface of the core pipe, bending the core pipe and the winding pipe together using a jig or like in order to bend the core pipe. Such a method allows the outer surface of the winding pipe to be in contact with the outer surface of the core pipe without any gap therebetween at least at the bending center portion of the bent part that comes into contact with a jig in the bending process. Therefore, at least at the bending center portion of the bent part, improved contact between the core pipe and the winding pipe is formed, which consequently improves the heat transfer performance.
In addition, when a part provided with the projections is bent, a large deformation and breakage may occur at a concave portion on the outer surface of the core pipe during the bending process. Therefore, conventionally, the bent part is not provided with the projections, and thus improvement of the heat transfer performance by means of the projections has not been achieved at the bent part. However, when the core pipe and the winding pipe are bent together with the winding pipe being wound around the outer surface of the core pipe, the overall strength increases so that it is possible to prevent a large deformation and breakage at a concave portion on the outer surface of the core pipe during the bending process, even if the bent part is provided with the projections.
Further, it is possible to improve the heat transfer performance by brazing the outer surface of the winding pipe to the outer surface of the core pipe by the brazing material in order to bond the core pipe to the winding pipe in the brazing process.
The heat exchanger according to the third aspect of the present invention enables improvement of the heat transfer performance since a poor contact between the core pipe and the winding pipe will not be formed at least at the bending center portion of the bent part. In addition, when the core pipe and the winding pipe are bent together with the winding pipe being wound around the outer surface of the core pipe, the overall strength increases so that it is possible to prevent a large deformation and breakage at a concave portion on the outer surface of the core pipe during the bending process, even if the bent part is provided with the projections.
The heat exchanger according to the present invention will now be described based on the attached drawings and the embodiments.
Next, the heat pump unit 2 is provided with a refrigerant circulating circuit that includes a compressor 21, the water heat exchanger 30, an expansion valve 23, and an air heat exchanger 24, which are connected sequentially by a winding pipe 32. The refrigerant is compressed to a high pressure by the compressor 21, and is then sent to the water heat exchanger 30. The refrigerant whose heat was exchanged in the water heat exchanger 30 passes through the expansion valve 23, and is supplied to the air heat exchanger 24. The refrigerant absorbs heat from the surroundings, and then circulates back to the compressor 21.
Next the core pipe 31 is described. As shown in
First, the projections 313 are formed on the inner surface of the core pipe 31. Here, as a method for forming the projections, as shown in
Next, the winding pipe 32 is helically wound around the core pipe 31. Subsequently, with the winding pipe 32 being wound around the outer surface of the core pipe 31, the core pipe 31 and the winding pipe 32 are bent together in order to form a bent part by using a jig such as a pipe bender that is usually commercially available. As shown in
Such a method allows the outer surface of the winding pipe 32 to be in contact with the outer surface of the core pipe 31 without any gap therebetween at least at the bending center portion of the bent part that comes into contact with the jig 50. When a part provided with the projections is bent, since a cross-section at the bent part of the core pipe has an irregular shape because of the projections, there is usually a risk that a poor contact may be formed between the core pipe and the winding pipe, consequently reducing the heat transfer performance. However, with the present invention, first the outer surface of the core pipe 31 is pressed so as to form the projections on the inner surface, and after which the winding pipe 32 is wound around the outer surface of the core pipe 31. Therefore, a poor contact will not be formed between the core pipe 31 and the winding pipe 32 at least at the bending center portion of the bent part, which consequently improves the heat transfer performance.
In addition, when a part provided with the projections is bent, a large deformation and breakage may occur at a concave portion on the outer surface of the core pipe during the bending process. Therefore, conventionally, the bent part is not provided with the projections, and thus improvement of the heat transfer performance by means of the projections has not been achieved at the bent part. However, when the core pipe 31 and winding pipe 32 are bent together with the winding pipe 32 being wound around the outer surface of the core pipe 31, the overall strength increases so that it is possible to prevent a large deformation and breakage at a concave portion on the outer surface of the core pipe during the bending process, even if the bent part is provided with the projections.
The final process is brazing. First, as shown in
Claims
1. A heat exchanger comprising:
- a core pipe having projections that are formed on an inner surface thereof by pressing an outer surface of the core pipe; and
- a winding pipe that is wound around the outer surface of the core pipe, wherein
- the core pipe has a linear part and a bent part,
- the outer surface of the winding pipe is in contact with the outer surface of the core pipe without any gap therebetween at a bending center portion of the bent part, and
- the outer surface of the winding pipe is bonded to the outer surface of the core pipe by a brazing material at the bending center portion of the bent part.
2. A method for manufacturing a heat exchanger including a core pipe and a winding pipe, comprising:
- pressing the outer surface of the core pipe so as to form projections on the inner surface thereof,
- winding the winding pipe around the outer surface of the core pipe;
- bending the core pipe with the winding pipe being wound around the outer surface of the core pipe; and
- brazing the outer surface of the winding pipe and the outer surface of the core pipe by a brazing material.
3. A heat exchanger comprising:
- a core pipe having projections that are formed on an inner surface thereof by pressing an outer surface of the core pipe;
- a winding pipe that is wound around the outer surface of the core pipe; and
- a brazing material that brazes the outer surface of the winding pipe to the outer surface of the core pipe,
- wherein
- the core pipe includes a bent part that is formed by bending the core pipe with the winding pipe being wound around the outer surface of the core pipe.
Type: Application
Filed: Apr 28, 2006
Publication Date: Mar 19, 2009
Applicant: Daikin Industries , Ltd. (Osaka-shi ,)
Inventors: Mitsuharu Numata (Osaka), Yutaka Shibata (Osaka)
Application Number: 11/913,408
International Classification: F28F 1/10 (20060101); B21D 53/06 (20060101);