JP2002318086A - Heat exchanger tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve heat transfer efficiency more than conventionally by reducing the area of a zone with a slow flow velocity, since a fluid diameter D is in proportion to the area of a hole and in inverse proportion to the length of the periphery of the hole to cause differences in the flow velocity and the like of refrigerant flowing inside and the heat exchange efficiency in some shapes of the hole even in the same fluid diameter. SOLUTION: In the perforated type flat tube of a heat exchanger, the fluid diameter of the hole of the flat tube is 0.6 mm to 1.1 mm, and a plurality of ribs projecting on the inner peripheral surface of the hole are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger tube used for a heat exchanger such as a condenser.

[0002]

2. Description of the Related Art Generally, a heat exchanger such as a condenser is provided with a heat exchanger tube for circulating a high-pressure heat exchange fluid in a heat exchange section. For example, Japanese Patent Application Laid-Open No. H06-21
The one disclosed in Japanese Patent No. 3534 is known.

As a heat exchanger using such a heat exchanger tube, a multi-flow type condenser is known. That is,
The flat tubes and the radiating fins are stacked and arranged between the header tanks arranged to face each other. In each header tank, a separator is provided at a predetermined position, and the refrigerant flows in a meandering manner between the header tanks through the flat tubes.

[0004] This type of flat tube is formed by integrally extruding a flat tube having multiple holes. The size and numerical value of this hole are set within a predetermined range (FIG. 8). Increasing the number of holes increases the number of partition walls between the holes, which is effective in preventing deformation of the flat tube. However, manufacturing becomes difficult because the size of one hole is small. At the same time, the pressure loss inside the tube increases, so that the refrigerant pressure decreases, and the condensing temperature of the refrigerant decreases accordingly. As a result, the temperature difference between the outside air temperature and the refrigerant decreases, and the heat exchange efficiency decreases.

On the other hand, when the number of holes in the flat tube is reduced, the number of partition walls is reduced, resulting in insufficient strength.
The flat tube is deformed. At the same time, when the flow rate of the refrigerant decreases, the heat transfer coefficient inside the tube decreases, and the performance decreases due to the decrease in the area inside the tube.

[0006] From these, there should be an appropriate number and size of holes. It has been proposed to set the fluid diameter (D) obtained from the relationship between the hole area (S) and the length around the hole (L) to an appropriate value. D = 4 × S / L For example, in Japanese Patent Application Laid-Open No. 06-213534, 0.6
It discloses that 0 mm <D <1.15 mm is set and the length of the path pipe that flows meandering between the flat tubes is set.

[0007]

However, the fluid diameter D is proportional to the hole area from the relation of D = 4 × S / L.
Although it is inversely proportional to the perimeter of the hole, even if the fluid diameter is the same, depending on the hole shape, such as a round shape or a polygonal shape, the flow velocity distribution of the refrigerant flowing inside is different and the heat exchange efficiency should be different.

For example, when the shape of each hole of the flat tube is rectangular, as shown in FIG. 6, the flow velocity is high in the central part and the flow velocity is low in the square part, so that the heat transfer efficiency is poor. The hatched portion in FIG. 6 indicates an area where the flow velocity is low. Even if the shape of the hole is triangular, the flow velocity is slow at three corners and the heat transfer efficiency is poor, as shown by hatching in FIG. In particular, in these shapes, the area of the region where the flow velocity is low in the square or triangular portion is large, resulting in poor heat transfer efficiency.

It is an object of the present invention to improve the heat transfer efficiency as compared with the prior art by reducing the area of the region where the angular flow velocity is low. To solve such a problem,
An object of the present invention is to form a protrusion protruding into the inside of a hole wall of a flat tube, reduce the flow velocity difference between the central part of the hole and the periphery, and reduce the area of a region where the flow velocity is low.

[0010]

According to a first aspect of the present invention, there is provided a multi-well flat tube of a heat exchanger, wherein the fluid diameter of the hole of the flat tube is 0.6 mm to 1.1 mm, and This is a configuration in which a plurality of ribs protruding from the peripheral surface are provided, and a heat exchanger excellent in heat exchange efficiency can be obtained.

According to a second aspect of the present invention, in the heat exchanger tube according to the first aspect, the number of ribs per hole is 4 to 10.
It is possible to obtain a heat exchanger having more heat exchange efficiency.

According to a third aspect of the present invention, in the heat exchanger tube according to the first or second aspect, the flat tube is constituted by an extruded tube, and the rib protruding into the hole is formed at the same time when the flat tube is extruded. It can be manufactured without increasing manufacturing man-hours and costs.

In the present invention, the fluid diameter of the hole is set in the range of 0.6 mm to 1.1 mm in view of the heat exchange efficiency. The reason for this is that if it is smaller than 0.6 mm, the hole shape becomes too small. Therefore, heat exchange efficiency is reduced due to an increase in pressure loss in the pipe and a decrease in condensation temperature. Also, it is very difficult to make a hole in a flat tube. When the fluid diameter of the hole is larger than 1.1 mm, the hole becomes large and the number of holes is reduced. Therefore, the performance is deteriorated due to a decrease in the heat transfer coefficient inside the tube and a decrease in the area inside the tube due to a decrease in the flow rate of the refrigerant.

The number of ribs is preferably in the range of 4 to 10. If the number is less than four, it is necessary to reduce the area of the hole in order to obtain a hole of the same fluid diameter. Owing to the small number of ribs, the number of regions near the inner surface area where the flow velocity is slow increases, and the heat transfer coefficient inside the tube decreases.

On the other hand, if the number of ribs is more than 10,
To obtain the same fluid diameter, the rib height must be reduced. If the diameter is too small, the effect of reducing the region where the flow velocity is low near the inner surface area by the rib is weakened, and the heat transfer coefficient inside the tube is reduced.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the multi-flow condenser 10 of this embodiment includes a plurality of flat tubes 11.
Are laminated via the radiating fins 12 for heat radiation. Side plates 13 and 14 are provided above and below the laminated flat tube 11 and corrugated fin 12. The open ends of the plurality of flat tubes 11 are inserted into insertion holes (not shown) formed in the header tanks 15 and 16 on both sides. Although not shown, upper and lower openings of the header tanks 15 and 16 are closed by lid members.
A partition plate is provided at a predetermined position of each of the header tanks 15 and 16.

Further, one header tank 15 has an inlet connection 18 and the other header tank 16 has an outlet connection 19.
Is provided. The heat exchange fluid flowing from the inlet connection 18 is supplied to the header tanks 15 and 16 and the flat tube 1.
The fluid flows in a meandering manner a plurality of times and flows out of the outlet connection portion 19. In this embodiment, the inlet connection portion 18 and the outlet connection portion 19 are provided in separate header tanks 15 and 16, however, a flow path may be formed so as to be provided in the same header tank.

Each of the flat tubes 11 is shown in FIGS.
As shown in FIG.
The heat exchange fluid flows through each of the holes 22 partitioned by 1. Ribs 23 facing the upper and lower surfaces of the inner peripheral surface of the hole 22 are formed. In the embodiment, three ribs 23 are provided on the upper and lower surfaces, respectively, in FIG. 4 and five in FIG.

Next, a method of manufacturing a flat tube will be described. A flat tube having five holes and having ribs on the upper and lower surfaces of each hole is simultaneously formed by extrusion. Compared to the conventional case of forming a flat tube without ribs, it can be manufactured without much difference in the number of manufacturing steps.

The heat release ratio (%) was measured for a flat tube in which the number of ribs inside the hole was changed and the fluid diameter was also changed. Core size: core width = 603 mm, core height = 29
7 mm, core thickness = 18 mm Number of tubes: 26, fin pitch is 1.4, tubes are the following samples a to h
Eight types of extrusion tubes were manufactured. a: 14 holes 6 ribs b: 8 holes 10 ribs c: 6 holes 8
Rib d: 7 hole 4 rib e: 18 hole 0 rib f: 10 hole 2 rib g: 9 hole 2
Rib h: 8 holes 0 ribs The experimental conditions were as follows: the air temperature at the condenser inlet was 37 ° C, the condenser inlet pressure was 1.74 MPa, the superheat was 25 ° C at the condenser inlet, the subcool was 5 ° C at the condenser outlet,
1.5m / s wind velocity at the inlet of condenser, HFC used
-134a was adopted.

With respect to the samples a to h, three passes and four passes were made as prototypes and their performance was evaluated. The higher performance was selected, the fluid diameter (mm) was plotted on the horizontal axis, and the heat release ratio (%) was plotted on the vertical axis, and the measurement results are shown in FIG. As shown in FIG. 2, even if the fluid diameter is large or small so as to draw a parabola having a peak near the fluid diameter of 0.8 to 0.9, the heat release ratio decreases. Based on the results of this experiment, the fluid diameter should be between 0.6 mm and 1.1 mm.

The parabola has different trajectories in the group having 0 to 2 ribs and the group having 4 to 10 ribs. Group with 0-2 ribs and 4 ribs
Since the performance is divided into groups of 10 to 10, the performance of these two groups was evaluated from another viewpoint. With respect to the samples b and f having substantially the same fluid diameter, the flow velocity in the pipe and the heat transfer coefficient inside the pipe were compared. The result is shown in FIG. Even with the same fluid diameter of 1.1, 10 of sample f
The heat transfer coefficient inside the tube is higher in the structure of 8 holes and 10 ribs of the sample b than in the hole 2 rib. This means that sample b
Means that the heat exchange efficiency is better. This corresponds to 8 ribs of sample b against 10 ribs 2 ribs of sample f.
This is probably because the low-flow area near the inner surface of the hole is smaller in the structure of the hole 10 rib (see FIG. 5). From this experimental result, it has been found that, even with the same fluid diameter, setting the number of ribs in a specific range improves the heat exchange efficiency. In particular, it was found that the number of ribs was preferably 4 to 10.

From these results, it is possible to obtain an optimum heat exchange efficiency when the fluid diameter of the flat tube hole is 0.6 mm to 1.1 mm and the number of ribs per hole is 4 to 10 ribs.

[0024]

According to the present invention, in the multi-well flat tube of the heat exchanger, the fluid diameter of the hole of the flat tube is 0.6 m.
A flat tube for a heat exchanger having excellent heat exchange efficiency can be obtained by providing a plurality of ribs having a length of m to 1.1 mm and protruding from the inner peripheral surface of the hole.

Further, the number of ribs per hole is 4 to 10
When it is used, a flat tube for a heat exchanger having higher heat exchange efficiency can be obtained.

When the flat tube is formed of an extruded tube, the rib protruding into the hole can be formed simultaneously with the extrusion of the flat tube, and can be manufactured without increasing the number of manufacturing steps and costs.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a heat exchanger to which the present invention is applied.

FIG. 2 is a diagram showing a relationship between a fluid diameter and a heat radiation amount ratio.

FIG. 3 is a diagram showing a flow velocity in a pipe and a heat transfer coefficient inside the pipe.

FIG. 4 is a cross-sectional view of a flat tube according to an embodiment of the present invention.

FIG. 5 is a view showing a hole shape of a flat tube according to an embodiment of the present invention.

FIG. 6 is a view showing a hole shape of a conventional flat tube.

FIG. 7 is a view showing another hole shape of a conventional flat tube.

FIG. 8 is a sectional view of a conventional flat tube.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Heat exchanger 11 Flat tube 12 Wavy fin 13 Side plate 14 Side plate 15 Header tank 16 Header tank 18 Inlet connection 19 Outlet connection

Claims (3)

[Claims] 1. A multi-hole flat tube of a heat exchanger,
Fluid diameter of flat tube hole is 0.6mm ~ 1.1mm
A heat exchanger tube comprising a plurality of ribs protruding from an inner peripheral surface of a hole. 2. The heat exchanger tube according to claim 1, wherein the number of ribs per hole is 4 to 10. 3. The heat exchanger tube according to claim 1, wherein said flat tube is an extruded tube.