Adopt streamlined finless microtube heat exchanger

Abstract

The application discloses a finless micro-pipe heat exchanger with streamline. The application comprises oppositely arranged working medium inflow cavities, working medium outflow cavities and capillary heat exchange pipe components, the working medium inflow cavities and the working medium outflow cavities are communicated through the capillary heat exchange pipe components, and the capillary heat exchange pipe components comprise a plurality of parallel arranged capillary heat exchange pipes. The capillary heat exchange pipe is a metal cylindrical pipe, the vertical section thereof is a special-shaped section, and the contour line of the special-shaped section is a closed curve formed by two inner concave curves and one outer convex curve. The two upper and lower inner concave curves are asymmetric, and the outer convex curve comprises two circular arc lines and an elliptical arc line. After flowing through one of the heat exchange pipes, the fluid streamline outside the pipe to the subsequent heat exchange pipe is smoother than that of other schemes, thereby effectively reducing the pressure drop, reducing the influence of air resistance, and improving the heat exchange effect.

Description

Technical Field

[0001] This invention belongs to the field of heat exchanger technology, specifically relating to a finless microtube heat exchanger with a streamlined cross-section. Background Technology

[0002] Microtube heat exchange technology has garnered widespread attention. Typical microtube heat exchangers consist of microtubes and fins, with fins enhancing heat transfer. However, the presence of fins increases the cost of the device, and the fin surface is prone to contamination and frost buildup, which can actually hinder heat transfer. Finless microtube heat exchangers, on the other hand, are constructed by welding together numerous bundles of microtubes with diameters less than 1 mm, offering better heat transfer performance and reducing overall weight. Current design goals for heat exchangers aim for even better heat transfer performance and lower pressure loss. Summary of the Invention

[0003] The purpose of this invention is to provide a streamlined, finless microtube heat exchanger with better heat exchange performance.

[0004] The present invention includes a working fluid inflow chamber, a working fluid outflow chamber, and a capillary heat exchange tube component arranged opposite to each other. The working fluid inflow chamber is provided with a working fluid inlet, and the working fluid outflow chamber is provided with a working fluid outlet. The working fluid inlet and the working fluid outlet are diagonally opposite each other. The working fluid inflow chamber and the working fluid outflow chamber are connected by the capillary heat exchange tube component, which includes multiple capillary heat exchange tubes arranged in parallel.

[0005] The capillary heat exchange tube is a metal cylindrical tube with an irregular cross-section. The outline of the irregular cross-section is a closed curve composed of two concave curves and one convex curve.

[0006] Of the two concave curves, the equation of the complete curve containing the upper concave curve is (x 2 +y 2 ) 2 -2·x(x 2 +y 2 )+n·y 2 =0, 2≥x≥0, y≥0, n=6~8; the equation of the complete curve containing the concave curve in the lower half is (x 2 +y 2 ) 2 -2·x(x 2 +y 2 )+m·y 2=0, 2≥x≥0, y≤0, m=5~7, n<m; The endpoints of the two complete curves are the same, with the left endpoint being the origin A(0,0) and the right endpoint being the farthest point B(2,0); The point at coordinates (0.5,0) is the center O of the circle with a radius of 0.5. The intersection point with the upper concave curve is C, and the intersection point with the lower concave curve is D; Curve segment AC is the upper concave curve, curve segment AD is the lower concave curve, and the origin A is the tip and tail of the closed curve;

[0007] The convex curve consists of two circular arcs and one elliptical arc. The upper arc is centered at point (1,0) with a radius R equal to the distance from point O' to point C. Its highest point is E, and arc CE is the upper arc. The lower arc is centered at point (1,0) with a radius r equal to the distance from point O' to point D. Its lowest point is F, and arc DF is the lower arc.

[0008] The semicircle of a regular ellipse with the line connecting E and F as its minor axis a is taken as the elliptical arc in the outwardly convex curve. The major axis of the regular ellipse is b = k·a, and the ratio of the major axis to the minor axis is k = 1.2 to 1.5.

[0009] The maximum diameter L of the metal cylindrical tube is the distance from the tip end A to the farthest point G of the elliptical arc, L = 1.5~1.8mm, and the overall outline is a closed curve ACEGFDA.

[0010] This invention employs capillary heat exchange tubes with an asymmetrical streamlined cross-section. The fluid flow path outside the tubes after passing through one tube is smoother than that of other designs, reducing pressure loss. This invention offers advantages such as compact structure, ease of maintenance and upgrades, low cost, and reliable operation. It effectively reduces pressure drop, minimizes wind resistance, and improves heat exchange efficiency. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of the present invention;

[0012] Figure 2 A schematic diagram of the complete curve containing the concave curve of the capillary heat exchanger cross-section profile.

[0013] Figure 3 A schematic diagram of the concave curve of the cross-sectional outline of a capillary heat exchanger tube;

[0014] Figure 4 A schematic diagram of the convex curve of the cross-sectional outline of a capillary heat exchanger tube;

[0015] Figure 5 A schematic diagram showing the complete outline of a capillary heat exchanger cross-section;

[0016] Figure 6 This is a schematic diagram of one arrangement of capillary heat exchange tubes in a capillary heat exchange tube assembly.

[0017] Figure 7 This is a schematic diagram of another arrangement of capillary heat exchange tubes in a capillary heat exchange tube assembly.

[0018] Figure 8 The diagram shows the velocity streamlines of the fluid outside a capillary heat exchanger tube with a circular cross-section.

[0019] Figure 9 The diagram shows the velocity streamlines of the fluid outside a capillary heat exchanger tube with a cross-section that is symmetrical vertically.

[0020] Figure 10 This is a streamline diagram of the external fluid velocity in the capillary heat exchanger tube of the present invention.

[0021] Figure 11 This is a schematic diagram showing the temperature difference between the fluid entering and exiting the heat exchanger tubes using capillary heat exchange tubes with different cross-sections.

[0022] Figure 12 This is a schematic diagram showing the pressure difference between the inlet and outlet of the fluid in a heat exchanger using capillary heat exchange tubes with different cross-sections. Detailed Implementation

[0023] The embodiments of the present invention are described in detail below. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0024] like Figure 1 As shown, a streamlined, finless microtube heat exchanger includes a working fluid inlet chamber 1, a working fluid outlet chamber 2, and a capillary heat exchange tube assembly 3 arranged opposite each other. The working fluid inlet chamber 1 is provided with a working fluid inlet, and the working fluid outlet chamber 2 is provided with a working fluid outlet, with the working fluid inlet and outlet diagonally opposite each other. The working fluid inlet chamber 1 and the working fluid outlet chamber 2 are connected by the capillary heat exchange tube assembly 3.

[0025] The capillary heat exchanger tube assembly 3 includes multiple (more than 1000) capillary heat exchanger tubes arranged in parallel, with all capillary heat exchanger tubes connected in parallel. In the figure, solid arrows indicate the direction of fluid flow in and out of the tubes, while dashed arrows indicate the direction of working fluid flow in and out.

[0026] The capillary heat exchange tube is a metal cylindrical tube with an irregular cross-section. The outline of the irregular cross-section is a closed curve composed of two concave curves and one convex curve. The hydraulic diameter of the closed curve is 0.5 to 1 mm.

[0027] like Figure 2 As shown, the equation of the complete curve (the dashed line in the figure) containing the upper part of the two concave curves is (x... 2 +y2 ) 2 -2·x(x 2 +y 2 )+n·y 2 =0, 2≥x≥0, y≥0, n=6~8; the equation of the complete curve (the dotted line in the figure) containing the concave curve in the lower half is (x 2 +y 2 ) 2 -2·x(x 2 +y 2 )+m·y 2 =0, 2≥x≥0, y≤0, m=5~7, n<m. In this embodiment, n=6, m=8. The endpoints of the two complete curves are the same, with the left endpoint being the origin A(0,0) and the right endpoint being the farthest point B(2,0).

[0028] like Figure 3 As shown, the circle with center O and radius 0.5, located at coordinates (0.5, 0), intersects the upper concave curve at point C and the lower concave curve at point D. Curve segment AC is the upper concave curve, curve segment AD is the lower concave curve, and the origin A is the tip / tail of the closed curve.

[0029] A convex curve consists of two circular arcs and one elliptical arc. For example... Figure 4 As shown, the upper arc is centered at point (1,0) with radius R, which is the distance from point O' to point C. The highest point of this circle is E, and arc CE is the upper arc. The lower arc is centered at point (1,0) with radius r, which is the distance from point O' to point D. The lowest point of this circle is F, and arc DF is the lower arc.

[0030] The ellipse is defined by half the circumference of a regular ellipse with the line connecting EF as its minor axis a. The major axis of the regular ellipse is b = k·a, and the ratio of the major axis to the minor axis is k = 1.2 to 1.5.

[0031] The maximum diameter L of the metal cylindrical tube is the distance from the tip A to the farthest point G of the elliptical arc, L = 1.5~1.8mm. The maximum diameter L is adjusted by adjusting the major axis of the ellipse. Figure 5 As shown, the overall contour is a closed curve ACEGFDA. Except for point A, the tangents of adjacent curves at their intersections are the same, ensuring the streamline of the contour.

[0032] The multiple capillary heat exchange tubes constituting the capillary heat exchange tube component are arranged in a matrix (e.g. Figure 6 As shown), or by using a cross arrangement (such as...). Figure 7(As shown). The convex curved portion of the capillary heat exchanger tube faces the direction of fluid entry outside the tube, while the tip and tail face the direction of fluid exit outside the tube, as shown. Figure 1 Solid arrow in the center. This arrangement helps to minimize air resistance.

[0033] When using a heat exchanger with a circular cross-section to exchange heat with fluid air, the air easily forms vortices between the circular tubes after passing through the circular cross-section, resulting in additional pressure loss, such as... Figure 8 As shown. Streamlined heat exchange tubes, with a more slender tail section while maintaining an equivalent hydraulic diameter, make it less likely for air to form vortices, thus reducing pressure loss.

[0034] By employing a streamlined design with an asymmetric cross-section, the airflow through one heat exchange tube to the next is smoother compared to the airflow in a symmetrical design, further reducing pressure loss. Figure 9 and 10 As shown, Figure 9 This is a streamline diagram of the fluid velocity outside a capillary heat exchanger tube with a symmetrical cross-section. Figure 10 The diagram shows the external fluid velocity streamline of a capillary heat exchanger tube with an asymmetrical cross-section, which is the external fluid velocity streamline diagram of the capillary heat exchanger tube in this embodiment.

[0035] The following simulation analysis is performed on capillary heat exchange tubes with circular cross-sections, symmetrical streamlined shapes, and asymmetrical streamlined shapes. Since the microtube heat exchanger is characterized by the absence of fins on the tube wall, the modeling analysis can be performed in two dimensions. The expansion coefficients n and m of the special curves used in this embodiment are 6 and 8, respectively. To control variables, one experimental group and five control groups are used. The experimental group model is established according to the description of this embodiment. The streamlined control group consists of symmetrical streamlined tube group 1 (n=m=8) and symmetrical streamlined tube group 2 (n=m=6), where the ratio of the major axis to the minor axis of the ellipse in the streamlined shape is k=1.5. The circular tube control group consists of circular tube group 1 (equivalent to streamlined tube group 1), circular tube group 2 (equivalent to streamlined tube group 2), and circular tube group 3 (equivalent to asymmetrical streamlined tube group). During the simulation, the operating conditions were set as follows: the horizontal spacing of the pipe walls was 0.5 mm, the vertical spacing of the pipe walls was 0.5 mm, the air inlet temperature was 27℃, the air inlet velocity was 1~10m / s, the pipe wall temperature was 5℃, and the working pressure was 1atm.

[0036] according to Figure 11 and Figure 12Simulation results show that, with the same equivalent hydraulic diameter, using streamlined microtubes can reduce wind resistance, lower pressure drop, and achieve a lower outlet temperature compared to circular tubes. Furthermore, when using asymmetric tube assemblies, compared to symmetric tube assembly 1, both pressure loss reduction and heat transfer efficiency are better; compared to symmetric tube assembly 2, the pressure drop is 5% lower, while the heat transfer efficiency is only about 1% different. Therefore, using asymmetric tube assemblies can achieve better pressure loss reduction. Details are shown in the table below:

[0037]

[0038] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application. The above are merely preferred embodiments of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this application, and these improvements and modifications should also be considered within the protection scope of this application.

Claims

1. A streamlined, finless microtube heat exchanger, comprising a working fluid inlet chamber, a working fluid outlet chamber, and a capillary heat exchange tube assembly arranged opposite to each other. The working fluid inlet chamber is provided with a working fluid inlet, and the working fluid outlet chamber is provided with a working fluid outlet. The working fluid inlet chamber and the working fluid outlet chamber are connected through the capillary heat exchange tube assembly, wherein the capillary heat exchange tube assembly comprises multiple capillary heat exchange tubes arranged in parallel; characterized in that: The capillary heat exchange tube is a metal cylindrical tube with an irregular cross-section. The outline of the irregular cross-section is a closed curve composed of two concave curves and one convex curve. The equation of the complete curve containing the upper concave curve is: , , , The equation of the complete curve containing the concave curve in the lower half is: , , , The two complete curves have the same endpoints, with the left endpoint being the origin. The right endpoint is the farthest point. ; The point with coordinates (0.5, 0) is the center of the circle. The intersection point of the circle with a radius of 0.5 and the curve containing the concave curve in the upper part is... The intersection point with the curve containing the concave curve in the lower half is ; Curve segment That is, the upper part of the concave curve, the curve segment That is, the lower half of the concave curve, origin. The point is the tip or tail of the closed curve; The convex curve consists of two circular arcs and one elliptical arc; of the two circular arcs, the circle containing the upper arc is centered at the point (1,0). The radius R is Click The distance between the points, and the highest point of the circle. , arc That is, the upper half of the arc; the lower half of the arc is centered at the point (1,0). The radius r is Click The distance between the points, and the lowest point of the circle. , arc That is, the lower half of the arc; by and The connecting line is the minor axis The semicircle of a regular ellipse is taken as the elliptical arc in the outwardly convex curve, and the major axis of the regular ellipse is... Major-minor axis ratio ; Maximum diameter of metal cylindrical tube For the tip end to the farthest point of the elliptical arc The distance, the overall outline is a closed curve .

2. The streamlined, finless microtube heat exchanger as described in claim 1, characterized in that: The hydraulic diameter of the closed curve is 0.5–1 mm; the maximum diameter is adjusted by adjusting the major axis of the ellipse. , .

3. The streamlined, finless microtube heat exchanger as described in claim 1, characterized in that: The multiple capillary heat exchanger tubes that make up the capillary heat exchanger tube component are arranged in a matrix or in a cross arrangement; the convex curve of the capillary heat exchanger tube faces the direction of the fluid entering the tube, and the tip and tail face the direction of the fluid exiting the tube.

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