HEADER PLATELESS TYPE HEAT EXCHANGER

Abstract

In a header plateless type heat exchanger, to suppress temperature rise at an apical portion of a tube into which exhaust gas at high temperatures or the like flows, to thereby improve durability. A recessed groove portion 4c recessed inward with narrow width is formed on outer face side of each of a pair of plates, in parallel to a swelling portion 4 and in the approximately same length.

Claims

1. A header plateless type heat exchanger, the heat exchanger comprising a flat tube that has a pair of plates each including a pair of side walls on both sides raised up to be formed in a groove-like shape wholly and swelling portions with narrow width formed outside in a thickness direction at edges on both open sides of a groove bottom orthogonal to the side wall, and these plates fitted while facing each other in an opposite direction; and a heat exchanger core in which plural flat tubes are stacked each other at swelling portions and respective plates are brazed and joined each other, in which a first fluid flows from each front edge of the swelling portions of flat tubes into the inside thereof, and a second fluid circulates on the outside thereof, wherein a recessed groove portion that is recessed inward with narrow width is formed on an outer face side of each of plates, in parallel to the swelling portion and in the approximately same length, and a projecting part that is inverse to the same is formed on an inner face side thereof.

2. The header plateless type heat exchanger according to claim 1, wherein each width of the swelling portions of the respective plates is formed so as to be width wide portions with wide width at both end portions in a longitudinal direction of the swelling portions and to be width narrow portions with narrow width in intermediate portions other than those, and, at the both end portions, the brazed and joined portions in a flat triangle or a curved plane, whose portion lying nearer to the side wall is wider, are included.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0020] FIG. 1 is a principal part plan view of a heat exchanger core of the present invention.

[0021] FIG. 2 is an II-II arrow-seen cross-sectional view in FIG. 1.

[0022] FIG. 3 shows a principal part perspective view (A) of a flat tube 7 for use in the heat exchanger core, and a principal part vertical section perspective view (B) of a heat exchanger core 15 composed of a stacked body of the flat tubes 7.

[0023] FIG. 4 is an exploded perspective view of a heat exchanger having the heat exchanger core 15.

[0024] FIG. 5 is a principal part plan view of a conventional type flat tube 16a.

[0025] FIG. 6 is a principal part vertical cross-sectional view of a core composed of a stacked body of the flat tubes 16a, and is a arrow-seen cross-sectional view in FIG. 5.

[0026] FIG. 7 shows a principal part perspective view of the flat tube 16a, and a principal part vertical section perspective view of a heat exchanger core 15a composed of a stacked body of the flat tubes 16a.

DESCRIPTION OF EMBODIMENTS

[0027] Next, embodiments of the present invention will be explained on the basis of drawings.

[0028] The heat exchanger of the present invention is optimal mainly as an EGR cooler. In this explanation of the embodiments, exhaust gas corresponds to a first fluid 10, and cooling water corresponds to a second fluid 11.

[0029] In this heat exchanger, as shown in FIG. 4, many flat tubes 7 are stacked to form a heat exchanger core 15, and the outer circumference of the heat exchanger core 15 is fitted with a casing 12. Then, the exhaust gas (first fluid) 10 is circulated on the inner face side of respective flat tubes 7, and the cooling water (second fluid) 11 is circulated on the outer face side thereof.

[0030] As shown in FIGS. 1-3, each of the flat tubes 7 forming the heat exchanger core 15 is composed of one in which a pair of plate 5, plate 6, each of which has a pair of side walls 1 raised at both ends to be formed in a groove-like shape as a whole, are fitted facing each other in the opposite direction.

[0031] At each of edges on both open sides (sides on which open ends of the flat tube 7 are formed) of respective plate 5, plate 6, a swelling portion 4 with narrow width is formed outward in the thickness direction.

[0032] Moreover, an inner fin 9 is inserted in the inside of each flat tube 7.

[0033] At least one side of each of parts to be joined each other is preferably covered or coated with a brazing material.

[0034] Meanwhile, the casing 12 is formed of a casing main body 12a in a box shape and a lid 12b. In addition, a pair of pipes 13 for the exhaust gas (first fluid) 10 are arranged on both ends in the longitudinal direction of the casing 12, and a pipe 14 for the cooling water (second fluid) 11 is arranged to the casing 12 so that cooling water is circulated through a water channel 17 of the heat exchanger core 15. Then, respective parts are brazed integrally in a furnace at high temperatures to form a heat exchanger.

(Characteristics of Invention)

[0035] The characteristic of the present invention here is the shape of the swelling portion 4 shown in FIG. 1, FIG. 2.

[0036] The swelling portion 4 is swelled in the thickness direction on open sides of the plate 5, plate 6.

[0037] In this example, the swelling portion 4 is formed so that the width thereof is wider at both end portions and is narrower in another place, in FIG. 1. In other words, in the intermediate portion, a width narrow portion 4a has a width L1, and at both end portions, a width wide portion 4b thereof has a width L2. Here, L2>L1. The width wide portion 4b has a shape of a flat triangle or a shape of a curved plane whose width of a portion lying nearer to both sides of the side wall 1 is wider.

[0038] Furthermore, in a range of this width narrow portion 4a, a recessed groove portion 4c is formed in parallel to the width narrow portion 4a. As shown in FIG. 2, this recessed groove portion 4c is formed on the outer face sides of plate 5, plate 6, and is recessed with a narrow width. In addition, the recessed groove portion 4c is formed in parallel to the width narrow portion 4a and in the approximately same length thereof.

[0039] Meanwhile, in this example, as shown in FIG. 1, FIG. 2, the length of the recessed groove portion 4c is formed to be the approximately same length as the length of the width narrow portion 4a, but, instead, it may also be capable to form the recessed groove portion 4c along the swelling portion 4, and to make the length of the recessed groove portion 4c the same as the total length of the swelling portion 4.

[0040] When seen from the inner face side of each of plate 5, plate 6, the recessed portion 4c is formed in an elongated projection. This recessed groove portion 4c may also be used for positioning of an inner fin.

[0041] Then, each of flat tubes 7 is stacked at the swelling portion 4 and, on the inner face side of the flat tube 7, a gas channel 16 into which the exhaust gas (first fluid) 10 flows is formed. In the gas channel 16, the inner fin 9 is internally mounted.

[0042] Moreover, the water channel 17 is formed on the outer face side of the flat tube 7 and the cooling water (second fluid) 11 is supplied thereto. On the water channel 17 side, the recessed groove portion 4c works as a guide channel of the cooling water (second fluid) 11. That is, through the recessed groove portion 4c, the cooling water (second fluid) 11 can be guided more smoothly to the width narrow portion 4a, to cool effectively the apical portion of the flat tube.

(Action)

[0043] In the heat exchanger as described above, the exhaust gas (first fluid) 10 flows through the open end on an inlet side of each flat tube 7 into the inside thereof. On the outer face side of the flat tube 7, the cooling water (second fluid) 11 having flowed from the pipe 14 on one side is supplied to each flat tube 7.

[0044] On the outer face side of each of plates 5, 6 composing the flat tube 7, the recessed groove portion 4c that is recessed inward and has narrow width is formed in parallel to and in the approximately same length as the width narrow portion 4a, and therefore the flow rate of the cooling water (second fluid) 11 flowing near the width narrow portion 4a on the outer face side of the flat tube 7, that is, in the recessed groove portion 4c increases.

[0045] Moreover, with the formation of the recessed groove portion 4c, a crossing angle on the outer face side of the stacking part of the flat tube 7 is expanded, and therefore the flow rate of the cooling water (second fluid) 11 near the width narrow portion 4a increases. As the result of these, cooling of the apical portion of the flat tube 7 is promoted to suppress temperature rise at the apical portion, and therefore degradation of the heat exchanger due to a heat cycle is prevented.

[0046] Furthermore, since the recessed groove portion 4c functions as a reinforcing rib against bending in the longitudinal direction of the width narrow portion 4a, it becomes capable to reduce the width of the width narrow portion 4a, and as the result, distance from the cooling water to the front edge of the flat tube 7 becomes shorter. This also promotes cooling of the apical portion to suppress temperature rise at the apical portion, and therefore degradation of the heat exchanger due to a heat cycle is prevented.

[0047] Moreover, the recessed groove portion 4c functions as a component of elastic deformation for expansion and contraction in the axis direction of the flat tube 7 to absorb difference in thermal expansion in the direction, and therefore degradation of the heat exchanger due to a heat cycle is also prevented.

[0048] Numerical analysis was performed about one example in order to confirm the effect of the present invention, in which the maximum value of apical portion temperature of the flat tube of the conventional type heat exchanger core shown in FIG. 5, FIG. 6, FIG. 7 was 358 C. and, in contrast, the maximum value of apical portion temperature of the flat tube of the heat exchanger core of the present invention was 265 C. Thus a remarkable temperature fall effect was confirmed.

INDUSTRIAL APPLICABILITY

[0049] The present invention is optimal for EGR coolers, and is also applicable to other heat exchangers such as exhaust heat recovering devices.

REFERENCE SIGNS LIST

[0050] 1: side wall [0051] 3: groove bottom [0052] 4: swelling portion [0053] 4a: width narrow portion [0054] 4b: width wide portion [0055] 4c: recessed groove portion [0056] 5: plate [0057] 6: plate [0058] 7: flat tube [0059] 8: dimple [0060] 9: inner fin [0061] 10: first fluid (exhaust gas) [0062] 11: second fluid (cooling water) [0063] 12: casing [0064] 12a: casing main body [0065] 12b: lid [0066] 13: pipe [0067] 14: pipe [0068] 15: heat exchanger core [0069] 15a: heat exchanger core [0070] 16: gas channel [0071] 16a: flat tube [0072] 16b: swelling portion [0073] 17: water channel