Resistance reducing fin of printed circuit board heat exchanger

Abstract

The invention provides a printed circuit board heat exchanger resistance reducing fin which comprises a plurality of fins discontinuously arranged on a heat exchange plate, the windward side of the head of each fin is a concave curved surface, the middle of each fin is a smooth straight surface, and a streamline curved surface of the tail of a traditional wing-shaped fin is reserved at the tail of each fin. According to the fin, resistance loss caused by fin head stagnation points and fin middle-rear part negative pressure gradient and flow separation can be greatly reduced, the flow resistance and pressure loss of the heat exchanger are remarkably reduced, and the comprehensive heat exchange capacity of the printed circuit board heat exchanger is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fins of microchannel heat exchangers, and particularly relates to a drag-reducing fin for a printed circuit board heat exchanger. Background Art

[0002] Driven by the pursuit of higher energy conversion efficiency, a highly efficient and compact printed circuit board heat exchanger (PCHE) based on chemical etching and diffusion welding technologies has broken through the performance bottleneck of traditional heat exchangers. Its core structure is composed of multiple stacked heat exchange plates. After millimeter-scale microchannels are etched on the heat exchange plates, the cold and hot side heat exchange plates are alternately welded into a whole through vacuum diffusion welding technology. The printed circuit board heat exchanger PCHE has an extremely high compactness with a specific surface area of 2500m 2 / m 3 and excellent high and low temperature (-200°C to 900°C) and high pressure (>30 MPa) resistance performance, making it of important application value in advanced energy systems such as solar power generation, very high temperature gas-cooled reactors, and nuclear fusion reactor cooling.

[0003] The existing research divides the channel structures of the printed circuit board heat exchanger PCHE into two categories:

[0004] (1) The continuous structure channels (such as straight channels and wavy channels) have a continuous flow path and relatively low pressure loss, but the relatively thick boundary layer will limit the heat transfer performance.

[0005] (2) The discontinuous structure channels (such as wing-shaped ribs, quasi-rhombus, and S-shaped ribs) disrupt the flow boundary layer through periodically arranged discontinuous fins, enhance the fluid mixing effect, and improve the heat transfer efficiency, but at the same time increase the flow resistance. In current research, the wing-shaped fins and quasi-rhombus fins with relatively good comprehensive performance have relatively large negative pressure gradients and flow separations at the leading stagnation points and sharp inflection points in the middle of the fins, and further optimization of their fin structures is required to overcome the large flow resistance and pressure loss and improve the comprehensive heat transfer performance of the channels of the printed circuit board heat exchanger PCHE.

[0006] It should be specifically noted that the above technical information is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as an admission or an indication in any form that the above technical information constitutes the prior art known to those skilled in the art. Summary of the Invention

[0007] In view of the deficiencies in the above-mentioned background art, the present invention optimizes the existing wing-shaped fins and rhomboid-like fin structures, and proposes a drag-reducing fin for a printed circuit board heat exchanger, which greatly reduces the flow resistance and pressure loss caused by the stagnation point at the fin head and the negative pressure gradient and flow separation in the middle and rear parts of the fin, and improves the comprehensive heat transfer capacity of the printed circuit board heat exchanger.

[0008] The technical solution of this application is as follows:

[0009] A drag-reducing fin for a printed circuit board heat exchanger includes a plurality of fins discontinuously arranged on a heat exchange plate. The windward surface of the fin head is a concave curved surface, the middle part is a smooth straight surface, and the tail part retains the streamline curved surface of the tail of the traditional airfoil fin.

[0010] Furthermore, the fin is formed by cross-combining two NACA00 series airfoil fins with the same size and chord length along the axis of symmetry in the length direction of the airfoil fin, and retaining the tail part. Two symmetric vertices B are formed at the cross-combining part. The convex curved surface of the fin head is turned into a concave curved surface along the axis of symmetry connecting the two symmetric vertices B and the vertex A of the fin head, and then the sharp inflection point B at the cross-combining part is replaced by a smooth straight surface, and the tail part maintains the streamline curved surface of the original NACA00 series airfoil fin.

[0011] Furthermore, the length L of the fin c is 4.0 - 16.0 mm, the width L of the fin w is 0.8 - 3.2 mm, and the height L of the fin h is 1.5 - 2 mm.

[0012] Furthermore, the fins are arranged staggered at intervals on the heat exchange plate. The vertical spacing L between adjacent fins t is 1.6 - 6.4 mm, the horizontal spacing L between adjacent fins z is 4.0 - 16 mm, and the staggered spacing L between adjacent fins k is 4.0 - 16 mm.

[0013] The specific beneficial effects of the present invention include:

[0014] 1. In the present invention, the windward surface of the fin head uses a concave curved surface to replace the convex curved surface of the traditional fin. Numerical studies show that in the range of mass flow rate from 1.057 to 4.017 g / s, the pressure loss at the fin head is reduced by 10.89% -

[0015] 13.21% and 3.28% - 5.26% respectively compared with the existing airfoil fins and rhomboid-like convex curved surface fins;

[0016] 2. In the present invention, the middle part of the fin uses a smooth straight surface to replace the tip inflection point. At a mass flow rate of 1.057 -

[0017] In the range of 4.017 g / s, numerical studies have shown that compared with the existing airfoil fins and rhomboid-like fins with middle tip inflection points, the negative pressure gradients of the fins are reduced by 57.14% - 76.53% and 14.29% - 25.00% respectively;

[0018] 3. Considering the above optimization effects of the fin structure, the comprehensive heat transfer performance (the ratio of the heat transfer factor to the friction factor j / f) of the printed circuit board heat exchanger of the present invention is increased by 5.19% - 9.20% and 1.90% - 2.65% respectively compared with the existing airfoil fins and rhomboid-like fins. This effectively reduces the flow resistance and pressure loss of the heat transfer fluid and improves the comprehensive heat transfer capacity of the heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0020] Figure 1 Schematic diagram of the fins on the heat transfer plate in the present invention;

[0021] Figure 2 Cross-sectional view of the NACA00 series airfoil fins;

[0022] Figure 3 Cross-sectional view and side view of the fins in the present invention;

[0023] Figure 4 Arrangement diagram of adjacent fins on the heat transfer plate in the present invention;

[0024] Figure 5 Stereoscopic schematic diagram of the core structure of the supercritical fluid printed circuit board heat exchanger in the embodiment using the fins of the present invention.

[0025] Explanation of the reference numerals in the drawings:

[0026] 1. Fins;

[0027] 2. Heat transfer plate;

[0028] 10. First heat transfer plate;

[0029] 20. Second heat transfer plate;

[0030] 30. First heat transfer fluid channel;

[0031] 40. Second heat transfer fluid channel. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the core concept of the present invention and the following embodiments, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0033] These embodiments are provided in this application to make this application thorough and complete, and to fully convey the scope of this application to those skilled in the art. It should be noted that: unless otherwise specifically stated, the relative arrangements of components and steps, the components of materials, numerical expressions and values described in these embodiments should be construed as merely exemplary, rather than as limitations.

[0034] A drag-reducing fin for a printed circuit board heat exchanger, as Figures 1 - 3 shown, includes a plurality of fins 1 arranged discontinuously on the heat exchange plate 2. The windward surface of the head of the fin 1 is a concave curved surface, the middle part is a smooth straight surface, and the tail retains the streamline curved surface of the tail of the traditional airfoil fin.

[0035] Specifically, the fin 1 is composed of two NACA00 series airfoil fins with the same size and chord length. They are cross-combined along the axis of symmetry in the length direction of the airfoil fin, and the tail part is retained. Two symmetric vertices B are formed at the cross-combination. See Figure 2 , and along the axis of symmetry connecting the two symmetric vertices B and the vertex A of the fin head, the convex curved surface of the fin head is turned into a concave curved surface, and then the sharp inflection point B at the cross-combination is replaced with a smooth straight surface, and the tail retains the streamline curved surface of the original NACA00 series airfoil fin to form, as shown in Figure 3 .

[0036] Specifically, the NACA00 series airfoil fin is a prior art and is a series of airfoils developed by the National Advisory Committee for Aeronautics (NACA) of the United States. The code name of each airfoil consists of the four letters "NACA" and a string of numbers, where the numbers represent the geometric parameters of the airfoil.

[0037] As an implementation manner, as Figure 5 shown, in the printed circuit board heat exchanger core formed by alternately stacking the heat exchange fluid one channel 30 and the heat exchange fluid two channel 40, supercritical CO2 working medium is introduced into the heat exchange fluid one channel 30 as the heat fluid. A plurality of non-continuous and staggered fins 1 are etched on the heat exchange plate one 10 by chemical etching. The length L c of the fin 1 is 4.0 mm, the width L w is 0.8 mm, the height L h is 1.5 mm. The fins 1 are arranged at staggered intervals on the heat exchange plate one 10, and the vertical spacing L between adjacent fins 1t is 1.6 mm, and the horizontal pitch L between adjacent fins 1 z is 4.0 mm, and the staggered pitch L between adjacent fins 1 k is 4.0 mm; The heat exchange fluid two-channel 40 serves as a cold fluid channel to cool the supercritical CO2 fluid in the above-mentioned heat exchange fluid one-channel 30. The heat exchange plate two 20 can select an appropriate channel structure form according to the fluid type and heat exchange process.

[0038] Use the FLUENT flow and heat transfer numerical simulation software to numerically calculate the pressure loss △P, friction factor f, heat transfer factor j, and the ratio of heat transfer factor to friction factor j / f (reflecting the comprehensive heat exchange performance of the channel) on the supercritical working fluid side of the printed circuit board heat exchanger with fins in the present invention, and compare the calculation results with those of the printed circuit board heat exchanger with NACA0025 airfoil fins under the same chord length and arrangement conditions. Table 1 lists the numerical models and their parameter settings.

[0039] Table 1 Numerical models and parameter settings

[0040]

[0041] Table 2 lists the numerical calculation results of the pressure loss △P, friction factor f, and the ratio of heat transfer factor to friction factor j / f (reflecting the comprehensive heat exchange performance) on the supercritical working fluid side of the printed circuit board heat exchanger with the new structure fins when the outlet pressure is 20 MPa, the inlet temperature is 686 K, and the inlet mass flow rate increases in the range of 1.057 - 4.017 g / s under a fixed cooling load, and the comparison with the corresponding calculation results on the supercritical working fluid side of the printed circuit board heat exchanger with NACA0025 airfoil fins.

[0042] Table 2

[0043]

[0044] It can be seen from Table 2 that compared with the NACA0025 airfoil fins, the reduction range of the pressure loss △P on the supercritical working fluid side of the printed circuit board heat exchanger with the fins in the present invention is 19.47% - 22.37%, the reduction range of the friction factor f is 11.02% - 16.55%, and the increase range of the ratio of heat transfer factor to friction factor j / f of the comprehensive heat exchange performance is 5.19% - 9.20%.

[0045] In summary, the above data shows that the flow resistance and pressure loss of the printed circuit board heat exchanger with the fin structure in the present invention are significantly reduced, and the comprehensive heat exchange capacity of the heat exchanger is significantly improved.

[0046] The details not elaborated in the present invention are all conventional technical means well known to those skilled in the art.

[0047] The above content shows and describes the basic principles, main features and beneficial effects of the present invention. The above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A resistance-reducing fin for a printed circuit board heat exchanger, characterized in that: It includes a number of fins (1) arranged discontinuously on a heat exchange plate (2). The windward surface of the head of the fin (1) is a concave curved surface, the middle part is a smooth straight surface, and the tail part retains the streamline curved surface of the tail of the traditional airfoil fin.

2. The drag reduction fin of the printed circuit board heat exchanger according to claim 1, wherein: The fin (1) adopts two NACA00 series airfoil fins with the same size and chord length, and they are cross-combined along the symmetry axis in the length direction of the airfoil fin, with the tail part retained. Two symmetric vertices B are formed at the cross-combination. The convex curved surface of the head of the fin (1) is inverted into a concave curved surface along the symmetry axis connecting the two symmetric vertices B and the vertex A of the fin head. Then, the sharp inflection point B at the cross-combination is replaced by a smooth straight surface, and the tail retains the streamline curved surface of the original NACA00 series airfoil fin.

3. The drag reduction fin of the printed circuit board heat exchanger according to claim 1, characterized in that: The length L of the fin (1) c is 4.0 - 16.0 mm, the width L w is 0.8 - 3.2 mm, and the height L h is 1.5 - 2 mm.

4. The drag-reducing fin of the printed circuit board heat exchanger according to claim 1, characterized in that: The fins (1) are arranged at staggered intervals on the heat exchange plate (2), and the vertical spacing L between adjacent fins (1) t is 1.6 - 6.4 mm, and the horizontal spacing L between adjacent fins z is 4.0 - 16 mm, and the staggered spacing L between adjacent fins k is 4.0 - 16 mm.

5. The drag reduction fin of the printed circuit board heat exchanger according to claim 1, characterized in that: A printed circuit board heat exchanger using the fin (1) is adopted. Its core is composed of multiple layers of hot and cold fluid heat exchange plates stacked alternately. The heat exchange plates using the fin (1) have several rows and several columns of the fins (1), and the fins (1) in adjacent rows and / or adjacent columns are arranged staggeredly at intervals.

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