HEAT EXCHANGER
A heat exchanger includes a heat transfer tube group in which a plurality of first heat transfer tubes (3) through which a first fluid flows and a plurality of second heat transfer tubes (4) through which a second fluid that exchanges heat with the first fluid flows are arranged alternately while being in contact with each other. The heat transfer tube group is formed in a spiral shape by being wound in X direction perpendicular to Y direction in which the first heat transfer tubes (3) and the second heat transfer tubes (4) are arranged. A plurality of concave portions (3a) are provided on both sides, in the X direction, of an outer circumferential surface (31) of each of the first heat transfer tubes (3), along an extending direction of the first heat transfer tube (3). The plurality of concave portions (3a) form convex portions on an inner circumferential surface of the first heat transfer tube (3).
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The present invention relates to a heat exchanger for exchanging heat between a first fluid and a second fluid, particularly to a heat exchanger suitable for heat pump type water heaters.
BACKGROUND ARTIn conventional heat pump type water heaters, air conditioners, floor heating devices, etc., a heat exchanger for exchanging heat between two kinds of fluids (water and a refrigerant, or air and a refrigerant, for example) is used.
For example, Patent Literature 1 discloses a heat exchanger 10 as shown in
PTL 1: JP 2006-162204 A
SUMMARY OF INVENTION Technical ProblemWith a configuration in which the circular water tube 11 and the circular refrigerant tubes 12 are wound while being in contact with each other as in the heat exchanger 10 disclosed in Patent Literature 1, it is possible to ensure a large length of contact among the tubes in a small occupation area. Therefore, the heat exchanger 10 can be downsized more than other heat exchangers having comparable performances. However, even this type of heat exchanger is required to be downsized further.
Under such circumstances, the present invention is intended to provide a heat exchanger that can be downsized further.
Solution to ProblemThe present invention provides a heat exchanger including a heat transfer tube group in which a plurality of first heat transfer tubes through which a first fluid flows and a plurality of second heat transfer tubes through which a second fluid that exchanges heat with the first fluid flows are arranged alternately while being in contact with each other. The heat transfer tube group is formed in a spiral shape by being wound in a perpendicular direction perpendicular to an arrangement direction in which the first heat transfer tubes and the second heat transfer tubes are arranged. A plurality of concave portions are provided on both sides, in the perpendicular direction, of an outer circumferential surface of each of the first heat transfer tubes, along an extending direction of the first heat transfer tube. The plurality of concave portions form convex portions on an inner circumferential surface of each first heat transfer tube.
Advantageous Effects of InventionIn the above-mentioned configuration, since both of the first heat transfer tube and the second heat transfer tube constituting the spiral-shaped heat transfer tube group are provided plurally, small-size tubes can be used as these heat transfer tubes. This makes it possible to reduce the minimum bend radius of the heat transfer tube group. Moreover, since the first heat transfer tubes and the second heat transfer tubes are arranged in a direction perpendicular to the direction in which the heat transfer tube group is wound, the width of the row of these tubes also can be kept small. Furthermore, since the first heat transfer tubes and the second heat transfer tubes are arranged alternately while being in contact with each other, a heat transfer tube of one type is sandwiched between heat transfer tubes of the other type, except for the heat transfer tubes located at both side ends. Thus, it is possible to ensure a large contact area between each first heat transfer tube and second heat transfer tube, and accordingly it is possible to shorten the entire lengths of the first heat transfer tube and the second heat transfer tube. With such a configuration, the heat exchanger of the present invention can be downsized further compared to conventional heat exchangers having comparable performances.
Furthermore, in the present invention, concave portions are provided on both sides, in a direction perpendicular to an arrangement direction in which the first heat transfer tubes are arranged, of an outer circumferential surface of each of the first heat transfer tubes, along an extending direction of the first heat transfer tube. The concave portions form convex portions on an inner circumferential surface of each first heat transfer tube. Therefore, the first fluid flows through the first heat transfer tube while colliding with the convex portions, so that the flow of the first fluid is disturbed. This makes it possible to improve the in-plane temperature uniformity of the first fluid and enhance the heat exchanging efficiency between the first fluid and the second fluid. As a result, the heat exchanger can be downsized further.
Hereinafter, the embodiments for carrying out the present invention will be described in detail with reference to the drawings. A description will be made below with respect to, as an example, a heat exchanger for exchanging heat between water and a refrigerant, such as carbon dioxide and chlorofluorocarbon alternative, used for an apparatus such as a heat pump type water heater. However, the present invention is not limited to this. For example, the present invention is applicable to a heat exchanger for exchanging heat between water and water (hot water), and an internal heat exchanger for exchanging heat between a high temperature refrigerant and a low temperature refrigerant in a heat pump cycle.
As illustrated in
The first heat transfer tubes 3 and the second heat transfer tubes 4 may be made of metal, such as copper, a copper alloy and SUS, having a satisfactory thermal conductivity. Circular tubes are used suitably as the first heat transfer tubes 3 and the second heat transfer tubes 4.
As shown in
The joining between the first heat transfer tube 3 and the second heat transfer tube 4 may be performed by brazing, soldering, use of a thermally conductive adhesive, etc. When joined using such a joining agent, the first heat transfer tube 3 and the second heat transfer tube 4 has a large joining area therebetween and can ensure an effective heat transfer area sufficiently. It is also possible to join the first heat transfer tubes 3 and the second heat transfer tubes 4 together by bundling collectively the first heat transfer tubes and the second heat transfer tubes 4 with a heat-shrinkable tube.
Here, the first heat transfer tubes 3 have preferably an outer diameter D1 equal to or larger than an outer diameter D2 of the second heat transfer tubes 4 (D2≦D1). The first heat transfer tubes 3 in the present embodiment have an outer diameter and wall thickness larger than those of the second heat transfer tubes 4. For example, in the case of using carbon dioxide (CO2) as the refrigerant, the outer diameter D2 of the second heat transfer tubes 4 is 5.0 mm and the outer diameter D1 of the first heat transfer tubes 3 is 6.0 mm.
The heat transfer tube group 2 is wound in a perpendicular direction (hereinafter referred to as “X direction”) perpendicular to an arrangement direction (hereinafter referred to as “Y direction”) in which the first heat transfer tubes 3 and the second heat transfer tubes 4 are arranged. Specifically, as shown in
Preferably, a gap S (see
As shown in
In the present embodiment, the water flows through the first heat transfer tubes 3 from a peripheral side toward a central side of the spiral shape of the heat transfer tube group 2, and the refrigerant flows through the second heat transfer tubes 4 from the central side toward the peripheral side of the spiral shape of the heat transfer tube group 2. Such a configuration allows the water and the refrigerant to form mutually opposed flows, and thereby the heat is exchanged effectively therebetween.
Specifically, a first outlet member 6 and a second inlet member 7 are disposed on the central side of the spiral shape of the heat transfer tube group 2, and a first inlet member 5 and a second outlet member 8 are disposed on the peripheral side of the spiral shape of the heat transfer tube group 2. The members 5 to 8 have a rectangular parallelepiped shape extending in the Y direction, and have internal spaces 51, 61, 71 and 81, respectively, at one end surface in the longer direction (the end surface illustrated in
Furthermore, in the present embodiment, a plurality of concave portions 3a and 4a as shown in
Specifically, in the specified regions E1 and E2, the plurality of concave portions 3a are provided on both sides, in the X direction, of an outer circumferential surface 31 of each of the first heat transfer tubes 3 at a specified pitch along the extending direction of the first heat transfer tube 3. Also, the plurality of concave portions 4a are provided on both sides, in the X direction, of an outer circumferential surface 41 of each of the second heat transfer tubes 4 at a specified pitch along the extending direction of the second heat transfer tube 4. As shown in
In the present embodiment, the concave portions 3a provided on one side, in the X direction, of the outer circumferential surface 31 of each of the first heat transfer tubes 3 and the concave portions 3a provided on the other side, in the X direction, of the outer circumferential surface 31 of each of the first heat transfer tubes 3 are disposed alternately along the extending direction of the first heat transfer tube 3. Likewise, the concave portions 4a provided on one side, in the X direction, of the outer circumferential surface 41 of each of the second heat transfer tubes 4 and the concave portions 4a provided on the other side, in the X direction, of the outer circumferential surface 41 of each of the second heat transfer tubes 4 are disposed alternately along the extending direction of the second heat transfer tube 4. Furthermore, in the present embodiment, the concave portions 3a provided on each first heat transfer tube 3 and the concave portions 4a provided on each second heat transfer tube 4 are linear recesses extending in a direction parallel to the extending direction of the first heat transfer tube 3 or the second heat transfer tube 4.
For example, when carbon dioxide is used as the refrigerant, the concave portions 4a with a length of 5.0 mm are provided on both sides, in the X direction, of each of the second heat transfer tube 4 at a pitch of 10 mm, and the concave portions 3a with a length of 5.0 mm are provided on both sides, in the X direction, of each of the first heat transfer tube 3 at a pitch of 10 mm. The pitch refers to a center-to-center distance between adjacent concave portions on one side in the X direction. The maximum depths (depths at the lowest points located at the deepest positions) of the concave portions 3a and 4a are 5% or more but 20% or less of the outer diameters of the heat transfer tubes 3 and 4, respectively.
In order to form the heat transfer tube group 2 with such a configuration, the first heat transfer tubes 3 and the second heat transfer tubes 4 both of which are straight are stacked alternately, these tubes stacked are joined by the above-mentioned method, and then the concave portions 3a and 4a are formed on both sides, right and left, of the heat transfer tube group 2 by pressing, for example. Thereafter, the heat transfer tube group 2 is bent, on the same plane, into an approximately-rectangular spiral shape. Alternatively, it is also possible to bend individually, on the same plane, the first heat transfer tubes 3 and the second heat transfer tubes on which the concave portions 3a and 4a respectively are formed in advance by pressing, etc. into an approximately-rectangular spiral shape and stack them.
As described above, in the heat exchanger 1 in the present embodiment, since both of the first heat transfer tube 3 and the second heat transfer tube 4 constituting the spiral heat transfer tube group 2 are provided plurally, small-size tubes can be used as these heat transfer tubes. This makes it possible to reduce the minimum bend radius of the heat transfer tube group 2. Moreover, since the first heat transfer tubes 3 and the second heat transfer tubes 4 are arranged in a direction perpendicular to the direction in which the heat transfer tube group 2 is wound, the width of the row of these tubes also can be kept small. Furthermore, since the first heat transfer tubes 3 and the second heat transfer tubes 4 are arranged alternately while being in contact with each other, a heat transfer tube of one type is sandwiched between heat transfer tubes of the other type, except for the heat transfer tubes located at both side ends. Thus, it is possible to ensure a large contact area between each first heat transfer tube 3 and second heat transfer tube 4, and accordingly it is possible to shorten the entire lengths of the first heat transfer tube and the second heat transfer tube. With such a configuration, the heat exchanger 1 of the present invention can be downsized further compared to conventional heat exchangers having comparable performances.
Furthermore, in the heat exchanger 1 in the present embodiment, the concave portions 3a are provided on both sides, in the X direction, of the outer circumferential surface 31 of each of the first heat transfer tubes 3, along the extending direction of the first heat transfer tube 3. The concave portions 3a form the convex portions 3b on the inner circumferential surface 32 of each first heat transfer tube 3. Therefore, the water flows through the first heat transfer tubes 3 while colliding with the convex portions, so that the flow of the water is disturbed. This makes it possible to improve the in-plane temperature uniformity of the water and enhance the heat exchanging efficiency between the water and the refrigerant. As a result, the heat exchanger can be downsized further. In addition, since the concave portions 3a are not provided in the Y direction in which the first heat transfer tubes 3 and second heat transfer tubes 4 are in contact with each other but are provided in the X direction, the above-mentioned effects can be obtained without increasing thermal contact resistance of these tubes.
Moreover, in the present embodiment, the concave portions 4a also are provided on both sides, in the X direction, of the outer circumferential surface 41 of each of the second heat transfer tubes 4, along the extending direction of the second heat transfer tube 4. The concave portions 4a form the convex portions 4b on the inner circumferential surface 42 of each second heat transfer tube 4. Also, the refrigerant flows through the second heat transfer tubes 4 while colliding with the convex portions 4b. Accordingly, the flow of the refrigerant is disturbed as well, so that the heat exchanging efficiency between the water and the refrigerant is enhanced further. As the second heat transfer tubes 4 for the refrigerant, grooved tubes in each of which a plurality of grooves are provided on the inner circumferential surface can be used instead of the circular tubes in each of which the concave portions 4a are provided on the outer circumferential surface 41. However, since such grooved tubes are expensive, the cost may be reduced by using, as in the present embodiment, the circular tubes in each of which the concave portions 4a are provided on the outer circumferential surface 41.
As shown in
Furthermore, since small-size tubes can be used as the first heat transfer tubes 3 and the second heat transfer tubes 4 as described above, it is possible to make the bend radii of the bent portions 2b of the spiral-shape heat transfer tube group 2 smaller and reduce further the dead spaces having the shape of an approximately right-angled triangle that are formed outside the heat exchanger 1 by the bent portions 2b.
Furthermore, in the present embodiment, the first inlet member 5 and the second outlet member 8 are disposed on the peripheral side of the spiral shape of the heat transfer tube group 2, and the first outlet member 6 and the second inlet member 7 are disposed on the central side of the spiral shape of the heat transfer tube group 2. In other words, the relatively low temperature water flows through the first heat transfer tubes 3 from one end located on the peripheral side of the spiral shape toward the other end located on the central side of the spiral shape, and the relatively high temperature refrigerant flows through the second heat transfer tubes 4 from one end located on the central side of the spiral shape toward the other end located on the peripheral side of the spiral shape. That is, when the heat exchanger 1 is observed as a whole, both of the water and the refrigerant flow so that the temperatures thereof increase from the periphery toward the center of the heat exchanger 1, and thereby the high temperature portion from which a large amount of heat is radiated to the outside can be disposed in a small area and the radiation loss can be suppressed more effectively. Moreover, since the viscosity of water lowers as its temperature increases, the configuration in which water flows so that its temperature increases toward the center of the spiral shape is preferable also from the viewpoint of pressure loss.
The inwardly-protruding convex portions 4b of the second heat transfer tubes 4 through which the refrigerant flows have the following effects. Usually, the refrigerant contains an oil, such as PAG (polyalkylene glycol), for lubricating compressors, etc. This causes the flow in each second heat transfer tube 4 to be a two-layer flow, forming an oil film on the inner circumferential surface 42 of the second heat transfer tube 4. In order to maintain a high heat exchanging efficiency, the thickness of the oil film preferably is as small as possible. The convex portions 4b are effective also in reducing the thickness of the oil film. More specifically, the presence of the convex portions 4b increases the flow velocity of the refrigerant near the inner circumferential surface 42, thereby increasing the difference between the velocity of the oil film flowing on the inner circumferential surface 42 and the velocity of the refrigerant. In such a situation, the refrigerant takes away a large amount of the oil from the surface of the oil film, reducing the thickness of the oil film. On the other hand, when the convex portions 4b have an excessively large height, the pressure loss is increased and the performance of the heat exchanger 1 is deteriorated. Therefore, it is preferable to set appropriately the maximum depth of the concave portions 4a and hold the height of the convex portions 4b within a proper range.
For example,
As shown in
The above-mentioned heat exchanger 1 is used suitably for a heat pump type water heater 200.
The present invention is not limited to the above-mentioned embodiment and can be modified variously. For example, the number and the outer diameter of the first heat transfer tubes 3 and the second heat transfer tubes 4 can be selected appropriately according to the performance required for the heat exchanger 1 and the types of the first fluid and the second fluid. In addition, the number of windings that the heat transfer tube group 2 makes and the size of its spiral shape also can be determined appropriately.
Furthermore, the heat transfer tube group 2 does not need to be formed in an approximately-rectangular spiral shape. For example, it may be formed in a circular spiral shape, or in a track-wound shape as shown in
In the present embodiment, the first heat transfer tubes 3 and the second heat transfer tubes 4 are arranged so that their centers lie on the same straight line. However, when the outer diameter D1 of the first heat transfer tubes 3 is different from the outer diameter D2 of the second heat transfer tubes 4, the first heat transfer tubes 3 and the second heat transfer tubes 4 may be arranged so that their outermost points on one side in the perpendicular direction perpendicular to the arrangement direction lie on the same straight line, for example. In this case, the centers of the first heat transfer tubes 3 and the centers of the second heat transfer tube 4 lie in a staggered manner.
Although the concave portions 3a provided on one side, in the X direction, of the outer circumferential surface 31 of each of the first heat transfer tubes 3 and the concave portions 3a provided on the other side, in the X direction, of the outer circumferential surface 31 of each of the first heat transfer tubes 3 are disposed alternately along the extending direction of the first heat transfer tube 3 in the above-mentioned embodiment, they may be disposed at positions facing each other in the X direction. However, when the concave portions 3a are parallel to the extending direction of the first heat transfer tube 3, since the concave portions 3a thus disposed elongate narrow portions in the first heat transfer tube 3, the concave portions 3a preferably are disposed as in the above-mentioned embodiment. This is also the case with the concave portions 4a provided on the second heat transfer tubes 4.
Furthermore, as shown in
Furthermore, the shapes and positions of the concave portions 3a and 4a also can be selected appropriately in combination such that the first heat transfer tube 3 is provided with the concave portions 3a parallel to the extending direction whereas the second heat transfer tube 4 is provided with the concave portions 4a inclined with respect to the extending direction, and that the concave portions 3a provided on both sides of the first heat transfer tube 3 are disposed alternately whereas the concave portions 4a provided on both sides of the second heat transfer tube 4 are disposed at the positions facing each other.
The concave portions of the present invention do not need to be linear recesses as long as they form convex portions on the inner circumferential surface of each first heat transfer tube or second heat transfer tube. For example, the first heat transfer tube 3 and the second heat transfer tube 4 may be formed in a wave shape meandering in the X direction so that valley portions of the wave shape may serve as the concave portions. That is, the convex portions of the present invention do not need to reduce the cross-sectional area of a space enclosed by the inner circumferential surface of the first heat transfer tube or the second heat transfer tube. The convex portions may be portions protruding inwardly while maintaining the cross-sectional area. However, from the viewpoint of workability, it is preferable that the concave portions of the present invention are recesses, particularly linear recesses extending in a specified direction, forming the convex portions 3b that reduce the cross-sectional area of a space enclosed by the inner circumferential surface of the first heat transfer tube 3 or the second heat transfer tube 4, as in the above-mentioned embodiments.
INDUSTRIAL APPLICABILITYThe heat exchanger of the present invention is useful as a heat exchanger for a heat pump, particularly as a heat exchanger for a heat pump type water heater. In addition, the present invention is applicable to a heat exchanger for exchanging heat between liquids or between gases.
Claims
1. A heat exchanger comprising a heat transfer tube group in which a plurality of first heat transfer tubes through which a first fluid flows and a plurality of second heat transfer tubes through which a second fluid that exchanges heat with the first fluid flows are arranged alternately while being in contact with each other, the heat transfer tube group being formed in a spiral shape so as to have a shape of a flat rectangular plate by being wound in a perpendicular direction perpendicular to an arrangement direction in which the first heat transfer tubes and the second heat transfer tubes are arranged,
- wherein a plurality of concave portions are provided on both sides, in the perpendicular direction in which the first heat transfer tubes and the second heat transfer tubes are out of contact with each other, of an outer circumferential surface of each of the first heat transfer tubes, along an extending direction of the first heat transfer tube, the plurality of concave portions form convex portions on an inner circumferential surface of the first heat transfer tube.
2. The heat exchanger according to claim 1, wherein the concave portions provided on one side, in the perpendicular direction, of the outer circumferential surface of the first heat transfer tube and the concave portions provided on the other side, in the perpendicular direction, of the outer circumferential surface of the first heat transfer tube are disposed alternately along the extending direction of the first heat transfer tube.
3. The heat exchanger according to claim 1, wherein the concave portions provided on one side, in the perpendicular direction, of the outer circumferential surface of the first heat transfer tube and the concave portions provided on the other side, in the perpendicular direction, of the outer circumferential surface of the first heat transfer tube are disposed at positions facing each other in the perpendicular direction.
4. The heat exchanger according to claim 1, wherein a plurality of concave portions also are provided on both sides, in the perpendicular direction, of an outer circumferential surface of each of the second heat transfer tubes, along an extending direction of the second heat transfer tube, and the plurality of concave portions form convex portions on an inner circumferential surface of the second heat transfer tube.
5. The heat exchanger according to claim 4, wherein the concave portions provided on one side, in the perpendicular direction, of the outer circumferential surface of the second heat transfer tube and the concave portions provided on the other side, in the perpendicular direction, of the outer circumferential surface of the second heat transfer tube are disposed alternately along the extending direction of the second heat transfer tube.
6. The heat exchanger according to claim 4, wherein the concave portions provided on one side, in the perpendicular direction, of the outer circumferential surface of the second heat transfer tube and the concave portions provided on the other side, in the perpendicular direction, of the outer circumferential surface of the second heat transfer tube are disposed at positions facing each other in the perpendicular direction.
7. The heat exchanger according to claim 1, wherein the concave portions are linear recesses extending in a specified direction.
8. The heat exchanger according to claim 7, wherein the specified direction is a direction parallel to the extending direction of the first heat transfer tube.
9. The heat exchanger according to claim 7, wherein the specified direction is a direction inclined with respect to the extending direction of the first heat transfer tube.
10. The heat exchanger according to claim 1, wherein the heat transfer tube group is formed in an approximately-rectangular spiral shape that is wound while repeating alternately a straight portion and a bent portion that is bent approximately 90° C. with a uniform bend radius.
11. The heat exchanger according to claim 1, wherein a gap is formed between an outer-located winding portion and an inner-located winding portion adjacent to each other in the heat transfer tube group.
12. The heat exchanger according to claim 1, wherein a heat insulating material is interposed between an outer-located winding portion and an inner-located winding portion adjacent to each other in the heat transfer tube group.
13. The heat exchanger according to claim 1, wherein the first fluid is heated by the second fluid.
14. The heat exchanger according to claim 13, wherein the first fluid is water and the second fluid is a refrigerant.
15. The heat exchanger according to claim 1, wherein both of the first heat transfer tubes and the second heat transfer tubes are circular tubes, and the first heat transfer tubes have an outer diameter equal to or larger than that of the second heat transfer tubes.
16. The heat exchanger according to claim 1, wherein the first fluid flows through the first heat transfer tubes from an peripheral side toward a central side of the spiral shape, and the second fluid flows through the second heat transfer tubes from the central side toward the peripheral side of the spiral shape.
17. The heat exchanger according to claim 4, wherein the concave portions are linear recesses extending in a specified direction.
18. The heat exchanger according to claim 17, wherein the specified direction is a direction parallel to the extending direction of the second heat transfer tube.
19. The heat exchanger according to claim 17, wherein the specified direction is a direction inclined with respect to the extending direction of the second heat transfer tube.
Type: Application
Filed: Jan 19, 2010
Publication Date: Nov 24, 2011
Applicant: PANASONIC CORPORATION (Kadoma-shi, Osaka)
Inventors: Tomoichiro Tamura (Osaka), Kou Komori (Nara)
Application Number: 13/147,743
International Classification: F28D 7/00 (20060101);