JP2020060355A - Flat tube for heat exchanger - Google Patents

Abstract

To improve heat-transfer property of an inner fin, in a flat tube for a heat exchanger in which a corrugated inner fin is stored so as to cause a gas to circulate inside thereof.SOLUTION: In a flat tube inside which a corrugated inner fin 4 is installed, the inner fin 4 is formed with a number of louvers 6 so as to be cut and raised from a standing upper surface 4a and a standing lower surface 4b.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a heat exchanger in which a corrugated inner fin is provided inside a flat tube and a gas flows therein, and a large number of louvers are cut and raised in the inner fin.

Some flat tubes used for charge air coolers and condensers have an offset inner fin or a corrugated inner fin inserted therein for stirring gas.
In the case of the corrugated inner fin, the ridgeline of the wave is arranged in the axial direction of the flat tube.

The flat tube having the corrugated inner fins has a feature that the flow resistance of the gas flowing inside is relatively small.
However, as compared with the flat tube having the offset type inner fin, there are drawbacks that the effect of stirring the gas is small and the heat transfer coefficient is small.
Therefore, an object of the present invention is to provide a flat tube for a heat exchanger having a corrugated inner fin, which has a high heat transfer coefficient and a high gas stirring effect.

According to the present invention as set forth in claim 1, a flat tube 3 having a pair of flat portions 1 facing each other and a pair of side portions 2 connecting the flat portions 1 with each other, and each wave parallel to the axial direction of the flat tube 3. And a corrugated inner fin 4 in which the ridgeline 8 is arranged, and a flat tube for a heat exchanger in which gas flows in the flat tube 3,
In the inner fin 4, a large number of louvers 6 are formed by cutting and raising on the rising surface 4a and the rising surface 4b of the wave, which are orthogonal to the axis and are separated in the gas flow direction. It is a flat tube.

  In the present invention according to claim 2, louvers 6a and 6b are formed on the inner fin 4 so as to be separated from each other in the amplitude direction of the wave so as to be vertically cut in two steps, and the direction of cutting and raising the louver 6a in the lower step portion 6c. The flat tube for a heat exchanger according to claim 1, wherein the louver 6b of the upper step portion 6d is cut and raised in the opposite direction.

  In the present invention according to claim 3, the louvers 6a and 6b have a cut-raised height H of H ≧ 0.2 mm and a cut-raised length L of L ≧ 1.0 mm. It is a flat tube for heat exchangers as described in 2.

According to the present invention as set forth in claim 4, the flat tube 3 has a ratio AR of a width dimension to an inner height of a cross section thereof,
The flat tube for a heat exchanger according to claim 2, wherein 1 <AR ≦ 7.

According to the invention described in claim 1, the ridge lines of the inner fins 4 are arranged in parallel with each other in the axial direction in the flat tube 3, and the louvers 6 are formed by cutting and raising on the upright surface 4a and the upright surface 4b. .
Due to the leading edge effect of the louver 6 that has been cut and raised, heat exchange between the gas inside the tube and the fluid outside the tube is improved.

In the invention according to claim 2, louvers 6a and 6b are formed on the inner fin 4 so as to be separated from each other in the amplitude direction of the wave and cut and raised in two steps, and the direction in which the louver 6a of the lower step portion 6c is cut and raised. The louver 6b of the upper step portion 6d is formed in a direction opposite to the cut and raised direction.
The flow deflected by the louvers 6a and 6b is reversed at the side surface of the flat tube to form a large swirl flow passing through the upper and lower cut-and-raised parts of the inner fin 4, and the swirl flow causes the fluid in the flat tube 3 to flow. Is gently stirred and mixed to reduce the imbalance of the temperature distribution inside the gas without significantly increasing the pressure loss, and to further improve the heat exchange between the gas and the fluid outside the tube. improves.

According to the third aspect of the invention, the cut-raised height H of the louvers 6a and 6b is H ≧ 0.2 mm and the cut-raised length L is L ≧ 1.0 mm.
As a result, the deflection effect of the louvers 6a and 6b is sufficiently exerted, so that the effect of the swirling flow can be surely obtained.

In the invention according to claim 4, the ratio AR (aspect ratio) of the width dimension to the inner height of the cross section of the flat tube 3 is set to 1 <AR ≦ 7.
As a result, the swirling cycle of the swirling flow is prevented from becoming excessively large, and the swirling flow is prevented from flowing in the flat tube without being sufficiently generated, so that the effect of the swirling flow is sufficiently exhibited.

The longitudinal section explanatory view of the flat tube for heat exchangers which has the inner fin of the present invention. The expanded cross-sectional view of the flat tube (the intermediate portion is omitted). III-III arrow sectional drawing of FIG. 2 (A), and BB arrow sectional schematic drawing of (A). Explanatory drawing of the louver 6 formed in the inner fin of this invention. Explanatory drawing of the louver of the other inner fin of this invention. FIG. 2 is a comparison of the flat tube for heat exchanger having the louver of the present invention and the flat tube for heat exchanger having no louver, in which the horizontal axis represents the air volume and the vertical axis represents the heat transfer coefficient. Comparison of heat transfer coefficient α and pressure loss ΔP with a flat tube having inner fins according to the present invention and a flat tube having no louver when the pitch thereof is 12.4 mm, 6.2 mm and 3.1 mm. Indicates. The comparison between the flat tube having the inner fin of the present invention and the flat tube having no louver, in which the louver length is 1.0 mm, 2.0 mm, and 3.0 mm, the heat transfer coefficient α and the pressure A comparison with the loss ΔP is shown. It is a comparison of heat transfer coefficient α and pressure loss ΔP between a flat tube for a heat exchanger having inner fins having no louver and a flat tube for a heat exchanger having a louver of the present invention, and a height H of the louver is 0. 2 mm and 0.3 mm are shown.

Next, an embodiment of the present invention will be described with reference to the drawings.
1 to 4 show a first embodiment of the present invention, FIG. 1 is a vertical cross-sectional explanatory view of a flat tube for a heat exchanger, FIG. 2 is an enlarged cross-sectional view of the same, and FIG. 3 is a III-III arrow of FIG. FIG. 4A is an explanatory cross-sectional view taken along the line BB in FIG. 4A, and FIG. 4 is an explanatory diagram of the louver 6 in the inner fin 4 in the flat tube.
This flat tube for a heat exchanger can be used, for example, in a charge air cooler or a condenser of a fuel cell.
As shown in FIG. 2, the flat tube 3 has a pair of flat portions 1 facing each other and a pair of side portions 2 connecting the flat portions 1, and the flat tube 3 is internally provided with a corrugated inner fin 4. It is a thing. The ridgeline 8 of each wave of the inner fin 4 is arranged parallel to the axial direction of the flat tube 3.
Further, the inner fin 4 has a plurality of louvers 6 cut and raised on the rising surface 4a and the rising surface 4b of each wave, which are orthogonal to the axis and are separated in the gas flow direction.

In this example, as shown in FIG. 2, louvers 6a and 6b, which are cut and raised in two steps above and below, are formed on the rising surface 4a and the rising surface 4b of the inner fin so as to be separated from each other in the amplitude direction of the wave, and the lower step portion 6c The direction of cutting and raising the louver 6a and the direction of cutting and raising the louver 6b of the upper step 6d are formed in opposite directions.
2, the opening of the louver 6a of the lower step portion 6c faces the downstream side in the axial direction, and the opening of the louver 6b of the upper step portion 6d faces the upstream side in the axial direction. Further, on the upright surface 4b facing the upright surface 4a, the opening of the louver 6a of the lower step portion 6c faces the upstream side in the gas flow direction, and the opening of the louver 6b of the upper step portion 6d faces the downstream side in the gas flow direction. ing.
It is displayed as follows in FIG. 3 (B).
In the lower step portion 6c of FIG. 3B, the opening of the louver 6a faces the downstream side of the gas 9 on the rising surface 4a located at the left end, and the opening of the louver 6b opens on the upstream side of the gas 9 on the rising surface 4a of the upper step portion 6d. Turn to the side.
On the contrary, on the upright surface 4b facing the upright surface 4a, the opening of the louver 6a of the lower step portion 6c faces the upstream side of the gas 9 and the louver 6b of the upper step portion 6d faces the downstream side of the gas 9.

By forming in this way, the gas 9 in the flat tube 3 flows through each louver 6a of the lower step portion 6c, is inverted to one side portion 2 and becomes a reflected flow 7 upward, and the upper step portion 6d. To each louver 6b. On the other side portion 2 (not shown), the gas is reversed to the other side portion 2 to form a downward reflected flow and is again guided to the louver 6a of the lower step portion 6c.
As a result, the gas 9 circulates in the flat tube 3 downstream in the axial direction while swirling in the vertical direction as shown in FIGS. Since the flow of the gas 9 swirls in the vertical direction in addition to meandering and stirring, heat exchange along the inner wall of the tube can be promoted and heat exchange performance can be enhanced.
As an example, cooling water circulates on the outer surface side of the flat tube 3 to exchange heat with the gas 9 inside.

Next, FIGS. 6 to 9 compare the heat transfer coefficient and the pressure loss of the inner fin having the louver of the present invention and the inner fin having no louver by computer simulation.
The setting values of the simulation at this time are as follows. The inner fin has an amplitude of 7 mm, a fin pitch of 4 mm, a fin plate thickness of 0.075 mm, and a flat tube has a short diameter of 7.8 mm, an inner dimension of 7 mm, and a long diameter of 48.5 mm. The dimension is 47.7 mm and the plate thickness is 0.4 mm.
In FIG. 6, the louver 6 has a height H = 0.3 mm, a length L = 1 mm, and a pitch P = 6.2 mm in FIG. When the air flow amount Va flowing into the flat tube on the horizontal axis is 1.39 m / s, 2.77 m / s, 4.16 m / s, 5.54 m / s, 8.31 m / s, there is no louver ( The vertical axis represents the heat transfer coefficient when compared with the inner fin of the (plane).
It is clear from FIG. 6 that the transmissibility α increases with an increase in the air volume, but its value peaks at 5.54 m / s and drops below 8.31 m / s. This is because α increases as the air volume increases, but the internal resistance further increases.

Next, FIG. 7 shows a conventional type in which the louver length L = 1 mm and the height H = 0.3 mm in FIG. 4 and the pitch P is 12.4 mm, 6.2 mm and 3.1 mm. The heat transfer coefficient α and the pressure loss ΔP are compared with those of the inner fin (plate type).
From this graph, it is understood that the heat transfer coefficient α and the pressure loss ΔP increase as the louver pitch P decreases, that is, as the number of louvers 6 increases.

Next, FIG. 8 shows heat transfer when the height H of the louver 6 is 0.3 mm, the pitch P is fixed to 6.2 mm, and the length L of the louver is 1 mm, 2 mm, and 3 mm in FIG. The rate α and the pressure loss ΔP are compared with those of the conventional inner fin (plate type).
It is clear from FIG. 8 that the heat transfer coefficient α is substantially constant regardless of the length L of the louver.
It was also found that the pressure loss ΔP decreases as the length L of the louver increases.

Next, in FIG. 9, when the length L of the louver 6 is fixed to 1 mm and the pitch P is fixed to 6.2 mm in FIG. 4 and the height H is set to 0.2 mm and 0.3 mm, respectively, the conventional inner fin ( It is a simulation of how the heat transfer coefficient α and the pressure loss ΔP of the plane are compared with those of the plain surface.
As a result, when the height H becomes higher, both the heat transfer coefficient α and the pressure loss ΔP become higher.

Next, FIG. 5 shows another embodiment of the louver 6 of the present invention, which is different from that of FIG. 4 in that in the case of FIG. It is a point where both sides of the louver are cut and raised.
You may cut and raise both sides in this way. In this case, the air flow by the louver 6 is further agitated, and the heat transfer coefficient is promoted.

In addition, in the simulations of FIGS. 6 to 9, various sizes of the inner fin and the flat tube are fixed to specific values, but the present invention is not limited thereto. For example, H is 0.2 mm or more, The length L of the louver may be 1.0 mm or more, and the ratio AR of the width dimension to the inner height of the cross section of the flat tube 3 may be 1 <AR ≦ 7.
In these ranges, the effects of the present invention can be achieved.

  Further, in FIG. 3, the louvers 6a and the louvers 6b are alternately arranged in the main flow direction of the gas 9, but even if they are arranged in the main flow direction of the gas 9, the effect of the present invention can be achieved. .

  Further, even if the main flow direction of the gas 9 is reversed, the action and effect of the present invention can be achieved.

  INDUSTRIAL APPLICABILITY The present invention can be applied to a heat exchanger in which gas flows inside a flat tube, such as a charge air cooler or a condenser for a fuel cell.

1 Flat part 2 Side part 3 Flat tube 4 Inner fin 4a Elevated surface 4b Elevated bottom surface 6 Louver 6a Louver 6b Louver 6c Lower step 6d Upper step 7 Reflected flow 8 Ridge line 9 Gas

Claims (4)

A flat tube (3) having a pair of opposed flat portions (1) and a pair of side portions (2) connecting the flat portions (1), and each wave parallel to the axial direction of the flat tube (3). And a corrugated inner fin (4) on which the ridgeline (8) is arranged, and a flat tube for a heat exchanger, in which gas flows in the flat tube (3),
In the inner fin (4), a large number of louvers (6) are formed by cutting and rising on the rising surface (4a) and the rising and falling surface (4b) of the wave, which are orthogonal to the axis and are separated in the gas flow direction. A flat tube for a heat exchanger, which is characterized in that   The inner fin (4) is formed with louvers (6a) (6b) which are cut and raised in two steps vertically separated from each other in the amplitude direction of the wave, and the direction in which the louver (6a) of the lower step (6c) is cut and raised. The flat tube for a heat exchanger according to claim 1, wherein the louvers (6b) of the upper step portion (6d) are formed so that their cut and raised directions are opposite to each other.   The louver (6a) (6b) has a cut-raised height H of H ≧ 0.2 mm and a cut-raised length L of L ≧ 1.0 mm. Flat tube for heat exchanger. In the flat tube (3), the ratio AR of the width dimension to the height inside the cross section is
The flat tube for a heat exchanger according to claim 2, wherein 1 <AR ≦ 7.

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