JPH06174384A - Double tube type heat exchanger - Google Patents

Abstract

PURPOSE:To make a heat exchange efficiency excellent and to improve performance. CONSTITUTION:Fins 22 in an inner tube 12 are formed of outer and inner offset fin plates 24 and 25. The two offset fin plates 24 and 25 are formed to be tubular respectively so that they form concentric-circle-shaped layers. The pitch of the inner offset fin plate 25 is made smaller than that of the outer offset fin plate 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-tube heat exchanger used, for example, for cooling oil of an automatic transmission of an automobile with cooling water of a radiator.

[0002]

2. Description of the Related Art As a heat exchanger of this type, there is known one in which the fins in the inner pipe are formed by flat plate fin plates, as disclosed in, for example, Japanese Patent Laid-Open No. 3-43653. .

[0003]

In the above heat exchanger, the fluid smoothly flows through the inner pipe along the fins, and the temperature boundary layer gradually develops on the fin surface along the flow direction, resulting in pressure loss. Is not so large, but there is a problem that the heat transfer coefficient is not good.

An object of the present invention is to provide a high performance double tube heat exchanger having a high heat transfer coefficient.

[0005]

A double-tube heat exchanger according to the present invention is an outer and inner offset fin plate in which the fins in the inner tube are cylindrically formed so as to form concentric layers. The pitch of the inner offset fin plate is smaller than the pitch of the outer offset fin plate.

[0006]

In the double tube heat exchanger according to the present invention, since the fins in the inner tube are formed by the offset fin plates, the boundary layer formed on the fins is cut off.
The heat transfer coefficient is increased.

Further, since the offset fin plates are outside and inside, and the outside and inside fin plates are respectively formed into cylindrical shapes so as to form concentric layers, turbulent flow is formed by the fin plates. It is generated every time.

Furthermore, since the pitch of the inner offset fin plate is smaller than the pitch of the outer offset fin plate, the magnitude of the turbulent flow generated for each layer is different.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIGS. 1 and 2, the double-tube heat exchanger comprises an outer pipe 11 and an inner pipe made of aluminum extruded pipe which are straightly and horizontally concentrically arranged.
12 and a pair of left and right annular end plates 13 and 14 that close the left and right ends of the gap between the tubes 11 and 12, respectively.

A rearward inverted L-shaped oil inlet pipe 15 is provided at the top of the right end of the outer pipe 11, and a forward inverted L-shaped oil outlet pipe 16 is provided at the bottom of the left end of the outer pipe 11, whereby the outer pipe is provided. An oil passage 17 facing left is formed between the inner pipe 11 and the inner pipe 12. A cooling water inlet pipe 18 is provided at the left end of the inner pipe 12, and a cooling water outlet pipe 19 is provided at the right end of the inner pipe 12 in a straight line. Are formed.

An oil fin 21 is provided in the oil passage 17, and a cooling water fin 22 is provided in the cooling water passage 20. The oil fin 21 is formed of a single aluminum brazing sheet offset fin plate 23 that is bent and formed into a tubular shape. The cooling water fins 22 are formed by an aluminum brazing sheet outer offset fin plate 24 and an inner offset fin plate 25 that are respectively bent and formed in a tubular shape so as to form two concentric layers in the inner and outer directions.

In the offset fin plate, as shown in FIG. 3, a wave having a predetermined height H and a width W has a predetermined pitch P.
Is formed in a concavo-convex shape, and one portion of the substantially U-shaped cross section forming one wave is displaced by a predetermined length l such that half of the width W of the wave is staggered in the direction in which the wave continues. That is, they are offset.

Each of the one oil fin forming offset fin plate 23 and the two cooling water fin forming offset fin plates 24 and 25 has the shape shown in FIG.

Referring to FIG. 4, the pitch P2 of the inner cooling water offset fin plate 25 is smaller than the pitch P2 of the inner cooling water offset fin plate 24.

The oil inlet pipe 15 and the oil outlet pipe 16 are connected to the oil pipe of the automatic transmission. The cooling water inlet pipe 18 and the cooling water outlet pipe 19 are connected to pipes to the radiator.

When the oil flows into the oil passage 17 and the cooling water flows into the cooling water passage 20, respectively, the fins 23 to 24 are respectively supplied.
Although a thermal boundary layer is formed along the surface, the boundary layer is cut off by the above offset, so that the boundary layer does not significantly develop and the heat transfer coefficient of the fin becomes extremely high. In particular, since the fins 24 and 25 having different shapes are arranged in two layers in the cooling water passage 20, turbulent flows having different sizes are generated in each layer, so that the heat transfer coefficient can be further improved.

5 and 6 show another embodiment. The outer pipe 11 and the inner pipe 12 of the heat exchange pipe shown in FIG. 1 were straight, but in the one shown in FIG. 5, the outer pipe 31 and the inner pipe (not shown) are bent into a substantially S shape, In the structure shown in FIG. 6, the outer pipe 41 and the inner pipe 32 are bent into a substantially U shape. The bending ratio R is preferably R> 3D when the outer diameters of the outer pipes 31 and 41 are D. If the bending R is up to this level, the outer pipe and the inner pipe are bent. Flattening of the tube is avoided.

By bending the outer pipes 31 and 41 and the inner pipe as described above, it is possible to avoid the heat exchanger from interfering with other things due to the mounting position of the vehicle, the space, etc. Can be effectively used.

[0020]

According to the present invention, since the boundary layer formed on the fins is cut off, the heat transfer coefficient increases, and turbulent flows of different sizes are generated for each layer formed by the fin plates. Therefore, it is expected that the heat transfer coefficient will be further improved, and a high performance double tube heat exchanger will be provided.

[Brief description of drawings]

FIG. 1 is a front view including a crushed cross section of a heat exchanger according to the present invention.

FIG. 2 is a side view including a crushed cross section of the heat exchanger.

FIG. 3 is a perspective view of a fin used in the heat exchanger.

FIG. 4 is a partial cross-sectional view showing details of fins in the inner pipe.

FIG. 5 is a front view corresponding to FIG. 1 showing a modified example of the heat exchanger.

FIG. 6 is a front view corresponding to FIG. 1 showing another modified example of the heat exchanger.

[Explanation of symbols]

 11 Outer tube 12 Inner tube 21 Oil fin 22 Cooling water fin 24 Offset fin plate 25 Offset fin plate P1 fin pitch P2 fin pitch

Claims (1)

[Claims] 1. The fins 22 in the inner tube 12 are formed by outer and inner offset fin plates 24, 25 respectively formed in a cylindrical shape so as to form concentric layers, and the pitch of the outer offset fin plates 24 Double-pipe heat exchanger in which the pitch P2 of the inner offset fin plate 25 is smaller than P1.