heat exchanger

Abstract

To provide a heat exchanger that can suppress the increase in pressure loss caused by the heat exchanger while improving the performance of heat exchange. [Solution] In this heat exchanger, a plurality of circular tubes are arranged in parallel in a direction parallel to the direction of airflow.

Description

Technical Field

[0001] This invention relates to a heat exchanger.

Background Art

[0002] Conventionally, a heat exchanger for an aircraft that performs heat exchange with an air flow and has a plurality of circular tubes through which a fluid to be heat-exchanged flows is known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Generally, the pressure loss (pressure drop) of the air supplied around a plurality of heat transfer tubes of a heat exchanger is large. Therefore, in a heat exchanger mounted on an aircraft or the like, there is a problem that it becomes a major factor in reducing flight performance and fuel efficiency.

[0005] This invention has been made to solve the above problems, and one object of this invention is to provide a heat exchanger that can suppress an increase in pressure loss due to the heat exchanger and improve the heat exchange performance.

Means for Solving the Problems

[0006] To achieve the above object, a heat exchanger according to one aspect of this invention is a heat exchanger for an aircraft that performs heat exchange with an air flow, has a plurality of circular tubes through which a fluid to be heat-exchanged flows, and the plurality of circular tubes are arranged in parallel in a direction parallel to the flow direction of the air flow.

Effects of the Invention

[0007] According to the present invention, it is possible to provide a heat exchanger that can suppress the increase in pressure loss caused by the heat exchanger while improving the performance of heat exchange. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view showing the main components of a heat exchanger according to Embodiments 1 to 3 of the present invention. [Figure 2] This is a cross-sectional view showing the main components of a heat exchanger according to Embodiment 1 of the present invention. [Figure 3] This is a cross-sectional view showing the main components of a heat exchanger according to Embodiment 2 of the present invention. [Figure 4] This is a cross-sectional view showing the main components of a heat exchanger according to Embodiment 3 of the present invention. [Figure 5] This graph shows the simulation results of the pressure loss of a heat exchanger according to Embodiments 1 to 3 of the present invention. This is the case with two circular tubes. [Figure 6] This graph shows the simulation results of the pressure loss of a heat exchanger according to Embodiments 1 to 3 of the present invention. This is the case with three circular tubes. [Figure 7] This graph shows the simulation results of the heat dissipation amount of a heat exchanger according to Embodiments 1 to 3 of the present invention. This is the case with two circular tubes. [Figure 8] This graph shows the simulation results of the heat dissipation amount of a heat exchanger according to Embodiments 1 to 3 of the present invention. This is the case with three circular tubes. [Figure 9] This is a distribution diagram of Mach numbers showing the simulation results of the heat dissipation amount of a heat exchanger according to Embodiment 1 of the present invention. This case has no flattened tubes and three circular tubes. [Figure 10] This is a distribution diagram of Mach numbers showing the simulation results of the heat dissipation amount of a heat exchanger according to Embodiment 1 of the present invention. This case has flattened tubes and three circular tubes. [Figure 11] This is a distribution diagram of heat flux values ​​showing the simulation results of the heat dissipation amount of a heat exchanger according to Embodiment 1 of the present invention. This case has no flattened tubes and three circular tubes. [Figure 12]This is a distribution diagram of heat flux values showing the simulation results of the heat dissipation amount of the heat exchanger according to Embodiment 1 of the present invention. It has flat tubes and there are three circular tubes. [Figure 13] This is a graph showing the simulation results of the pressure loss of the heat exchanger according to Embodiment 1 of the present invention. There are three circular tubes, and the influence of the gap distance between the circular tubes is shown. [Figure 14] This is a graph showing the simulation results of the pressure loss of the heat exchanger according to Embodiment 2 of the present invention. There are three circular tubes, and the influence of the gap distance between the circular tubes is shown. [Figure 15] This is a graph showing the simulation results of the pressure loss of the heat exchanger according to Embodiment 3 of the present invention. There are three circular tubes, and the influence of the gap distance between the circular tubes is shown.

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described based on the drawings. In the following, the same reference numerals will be used for the same configurations, and the description thereof may be omitted.

[0010] FIG. 1 is a cross-sectional view showing the main part configuration of the heat exchanger unit of the present invention, and is a schematic diagram of the basic heat exchanger 20.

[0011] The heat exchanger 20 is an air heat exchanger that performs heat exchange between the internal fluid flowing through the internal heat transfer tubes 30 and air. Examples of the internal fluid flowing through the heat transfer tubes 30 include hydrogen, fluorocarbon, hydrocarbon, or water.

[0012] The heat exchanger 20 has a plurality of heat transfer tubes 30. In the following description, the plurality of heat transfer tubes 30 may be referred to as heat transfer tubes 30A, 30B, 30C, 30D, and 30E in order from the left in FIG. 1.

[0013] The plurality of heat transfer tubes 30 are arranged in parallel with each other. The parallel direction of the plurality of heat transfer tubes 30 is, for example, a direction (x direction) parallel to the air flow direction. Here, it is set that the air flows from the minus direction of x to the plus direction, that is, from the left to the right in the figure. The same applies hereinafter.

[0014] Also, the parallel direction of the plurality of heat transfer tubes 30 is perpendicular to the extending direction (z direction) of the heat transfer tubes 30. The plurality of heat transfer tubes 30 are sandwiched by a pair of headers. One end of each heat transfer tube 30 is connected to one header, and the other end of each heat transfer tube 30 is connected to the other header. The longitudinal direction of each header is the same direction as the parallel direction of the plurality of heat transfer tubes 30. The heat transfer tubes 30 are preferably formed using a metal material having high thermal conductivity such as aluminum, copper, or brass.

[0015] (Embodiment 1) FIG. 2 is a cross-sectional view showing a main part configuration of the heat exchanger 20 according to Embodiment 1 of the present invention.

[0016] In the present embodiment, a flat tube having a flat cross-sectional shape in one direction is used as the heat transfer tube 30.

[0017] In the heat exchanger 20 according to Embodiment 1, the flat tube is arranged upstream (front) of the air flow.

[0018] (Embodiment 2) FIG. 3 is a cross-sectional view showing a main part configuration of the heat exchanger 20 according to Embodiment 2 of the present invention.

[0019] In the heat exchanger 20 according to Embodiment 2, the flat tubes are arranged both upstream (front) and downstream (rear) of the air flow.

[0020] (Embodiment 3) FIG. 4 is a cross-sectional view showing a main part configuration of the heat exchanger 20 according to Embodiment 3 of the present invention.

[0021] In the heat exchanger 20 according to Embodiment 3, the flat tube is arranged downstream (rear) of the air flow.

[0022] (Simulation results) Figures 5 to 15 show examples of simulation results for a heat exchanger 20 according to embodiments 1 to 3 of the present invention.

[0023] In the simulation, a three-dimensional steady-state calculation of compressibility was performed using the SST-K-ω turbulence model in the Reynolds-meaned Navier-Stokes equations. The simulation conditions assumed air to be an ideal gas. The heat transfer tubes were assumed to be made of aluminum, with a density of 2702.0 kg / m³ and a thermal conductivity of 237.0 W / mK. The internal fluid flowing inside the heat transfer tubes was omitted in this study; that is, the calculation was performed with temperature constraints around the heat transfer tubes.

[0024] Figures 5 to 15 show the simulation results for calculating the pressure loss and heat dissipation from the surface of the circular tube from upstream to downstream. For the air, assuming use in an aircraft flying at high altitude, the static pressure was set to -81060.0 Pa gauge pressure and the ambient temperature to 20°C, and the total temperature and mass flow rate upstream were set according to the Mach number. The Mach number is the ratio of the speed of airflow to the speed of sound. For the heat transfer tube, the temperature was set to 150°C. The predetermined relationship that the pressure loss and heat dissipation in the first to third embodiments must satisfy was derived based on the calculation results of this simulation. The following will explain the calculation results for pressure loss and heat dissipation together.

[0025] The calculations were performed from three perspectives: (Perspective 1) the effect of the presence or absence of flattened tubes on reducing pressure loss, (Perspective 2) the effect of the presence or absence of flattened tubes on increasing heat dissipation, and (Perspective 3) the effect of the gap distance between heat transfer tubes.

[0026] (Perspective 1) Figures 5 and 6 are graphs showing the simulation results of the pressure loss of the heat exchanger 20 according to embodiments 1 to 3 of the present invention. The vertical axis represents the pressure loss reduction rate, and the horizontal axis represents the Mach number. The reduction rate is the ratio of the pressure loss calculated by using the case without flattened pipes as the denominator and the case with flattened pipes as the numerator.

[0027] ● represents Embodiment 1, ▲ represents Embodiment 2, and △ represents Embodiment 3.

[0028] According to Figure 5, in the case of two circular pipes, in Embodiment 3, there was no reduction in pressure loss when the Mach number was 0.3 or less, but in all other cases, a reduction in pressure loss was confirmed at Mach numbers of 0.2 to 0.8. According to Figure 6, in the case of three circular pipes, a reduction in pressure loss was confirmed in all embodiments at Mach numbers of 0.2 to 0.8.

[0029] (Perspective 2) Figures 7 and 8 are graphs showing the simulation results of the heat dissipation amount of the heat exchanger 20 according to embodiments 1 to 3 of the present invention.

[0030] In the case of two circular tubes shown in Figure 7, the heat dissipation effect can be increased in Embodiment 2 when the Mach is 0.4 or higher. In the case of three circular tubes shown in Figure 8, it can be seen that in Embodiments 1 and 2, the amount of heat dissipated can also be increased when the Mach is 0.3 or higher.

[0031] Figures 9-12 show an example of calculation results under the condition of a Mach number of 0.6 when there are three circular pipes in Embodiment 1 of the present invention, comparing the case with and without the flattened pipe. The effect of increased heat dissipation due to the placement of the flattened pipe upstream (forward) of the airflow was observed. Figures 9 and 10 show contours in grayscale for Mach numbers from 0 to 1.0, and from this comparison, it can be seen that the presence of the flattened pipe causes the air with a high Mach number around the circular pipe to approach.

[0032] In the absence of the flattened pipe shown in Figure 9, the airflow appears to separate vertically in the upstreammost circular pipe and then separate from the circular pipe downstream. On the other hand, when the flattened pipe shown in Figure 10 is present, the airflow flows smoothly at the upstreammost point, and a reduction in pressure loss can be inferred, but more importantly, the approach of the airflow to the circular pipe is clearly observed.

[0033] Next, Figures 11 and 12 show the boundary heat flux [W / m^2] at the surface of the circular pipe. The grayscale contours are presented with values ​​from -70,000 to 0, with negative values ​​indicating greater heat dissipation. The amount of heat dissipated from the circular pipe to the air is greater when it is close to -70,000. In Figure 11, since there is no flattened pipe, the amount of heat dissipation is greatest at the surface of the upstream circular pipe, where the value was -53,000 [W / m^2]. On the other hand, in Figure 12, a maximum value of -66,000 [W / m^2] was shown near the side of the upstream circular pipe. In addition, as shown in Figure 12, it was observed that high heat dissipation was also distributed at the surface of the AC circular pipe other than the upstreammost point.

[0034] As seen in Figures 9 to 12, it was observed that the presence of a flattened tube like that in Embodiment 1 resulted in an increase in heat dissipation.

[0035] (Perspective 3) Figures 13-15 are graphs showing the simulation results of the pressure loss and the gap distance of the circular pipe for the heat exchanger 20 according to embodiments 1 to 3 of the present invention. Here, D represents the diameter of the circular pipe.

[0036] Figures 13-15 show that a significant reduction in pressure loss can be achieved when the gap between the three circular pipes is less than 0.25D, or when they are in contact with each other.

[0037] (Effects of the above embodiment) In the above embodiment, the following effects can be obtained.

[0038] According to embodiments of the present invention, by arranging the circular pipes in parallel in a direction parallel to the direction of airflow, pressure loss can be kept low.

[0039] Furthermore, according to embodiments of the present invention, pressure loss can be further reduced by changing the airflow around the circular pipe using flattened pipes installed upstream, downstream, or both of the circular pipe.

[0040] Furthermore, according to the embodiments of the present invention, the amount of heat dissipated by the cylindrical tube can be increased. In other words, the heat exchange performance of the heat exchanger can be improved. [Explanation of symbols]

[0041] 20 Heat exchanger 30(30A, 30B, 30C, 30D, 30E) Heat exchanger tube (circular tube)

Claims

1. A heat exchanger for aircraft that exchanges heat with airflow, It has multiple circular pipes through which the fluid to be subjected to heat exchange flows, A heat exchanger in which the plurality of circular tubes are arranged in parallel in a direction parallel to the direction of airflow.

2. The heat exchanger according to claim 1, wherein a flattened pipe having a flattened cross-sectional shape in a direction parallel to the airflow direction is arranged upstream of the plurality of circular pipes.

3. The heat exchanger according to claim 1, wherein flattened pipes having a flattened cross-sectional shape in a direction parallel to the airflow direction are arranged upstream and downstream of the plurality of circular pipes.

4. The heat exchanger according to claim 1, wherein a flattened pipe having a flattened cross-sectional shape in a direction parallel to the airflow direction is arranged downstream of the plurality of circular pipes.

5. The flattened tube is positioned in contact with one of the plurality of circular tubes. The heat exchanger according to claims 2 to 4, wherein the plurality of circular tubes are arranged such that the gap distance is less than 0.25 times the diameter of the circular tube, or is 0.

6. The heat exchanger according to claims 1 to 5, wherein the number of the plurality of circular tubes is 2.

7. The heat exchanger according to claims 1 to 5, wherein the number of the plurality of circular tubes is 3.

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