Vortex-variable synergistic micro-channel heat exchange method and heat exchanger thereof

Abstract

The invention discloses a variable vortex synergistic micro-channel heat exchange method which comprises the following steps: firstly, determining the position of a transverse vortex, performing numerical simulation analysis on a micro-channel structure with a turbulent flow element, and determining the direction of a rotating shaft and the position of a rotating core of the transverse vortex; and secondly, optimizing the micro-channel structure: by changing the direction of the channel at the position of the rotating core, realizing alignment between a main flow direction and a rotating shaft direction, realizing conversion from a transverse vortex to a longitudinal vortex, finally analyzing the performance of the optimized micro-channel structure, and comparing and analyzing the thermal hydraulic performance of the micro-channel structure before and after optimization. And the runner length with the optimal heat transfer optimization effect is determined. The transverse vortex generated by the turbulent flow element is optimized into the longitudinal vortex through flow channel steering, so that the heat exchange performance is obviously improved on the premise that the flow resistance is slightly increased, and the optimized structure obtained through the method is low in machining cost and machining technical requirements and can be better applied practically in production and life.

Description

Technical Field

[0001] The invention relates to the field of heat exchanger performance optimization, and in particular to a microchannel design method for optimizing an eddy current field and a heat exchanger thereof. Background Art

[0002] Printed circuit heat exchangers, also known as microchannel heat exchangers, are widely used in nuclear energy, solar energy, waste heat recovery and other fields because of their high temperature resistance, high pressure resistance, high heat exchange performance and high compactness. Improving the performance of microchannel heat exchangers can reduce energy consumption in industrial processes, reduce carbon dioxide emissions and other environmental pollutants, and reduce energy costs, which helps to reduce the negative impact on the environment and is in line with the principle of sustainable development. Further improving the performance of microchannel heat exchangers is of great significance to improving the economy and saving resources. Summary of the invention

[0003] 1. Technical issues to be resolved

[0004] In view of the shortcomings of the prior art, the present invention provides a microchannel heat exchange method and heat exchanger with variable vortex efficiency, so as to further improve the heat exchange performance, flow resistance performance and compact performance of the microchannel. In addition, a microchannel heat exchanger structure with variable vortex efficiency is created and developed according to the design method.

[0005] (II) Technical solution

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0007] A microchannel heat exchange method for variable vortex flow efficiency enhancement comprises the following steps:

[0008] S1. First, determine the position of the lateral vortex, perform numerical simulation analysis on the microchannel structure with the spoiler element, and determine the rotation axis direction and the rotation core position of the lateral vortex;

[0009] S2. Optimization of microchannel structure: By changing the direction of the channel at the position of the rotating core, the alignment between the main flow direction and the rotation axis direction has been achieved to realize the conversion of transverse vortex to longitudinal vortex;

[0010] S3. Analyze the performance of the optimized microchannel structure and conduct comparative analysis. Based on the simulation software Ansys fluent, the numerical simulation method is used to analyze the variation law of the heat transfer performance of the optimized microchannel structure along the flow direction, so as to determine the flow channel length with the best heat transfer optimization effect.

[0011] A heat exchanger for a microchannel heat exchange method with variable vortex efficiency enhancement includes a heat exchange core, with hot and cold fluid inlet boxes and hot and cold fluid outlet boxes, hot fluid plates and cold fluid plates connected to the two sides of the heat exchange core respectively. The heat exchange core is formed by alternately welding the hot fluid plates and the cold fluid plates. The hot fluid and the cold fluid enter the heat exchange core from the hot and cold fluid inlet boxes and exchange heat in reverse flow, and flow out of the heat exchange core from the hot and cold fluid outlet boxes. The hot and cold fluids flow in opposite directions in the heat exchange core.

[0012] Furthermore, the hot fluid plate includes an inlet section, a core zigzag heat exchange channel and an outlet section, and the structure of the cold fluid plate is completely consistent with that of the hot fluid plate.

[0013] Furthermore, the core zigzag heat exchange flow channel places the same or multiple spoiler elements at intervals of optimal period length along the flow direction, the flow channel streamline is multi-period zigzag, the zigzag point is located at the optimal distance behind the spoiler element, and the bending angle is 60 to 90 degrees.

[0014] Furthermore, the spoiler element is one or a combination of the following structures: a cylindrical spoiler element, a pit spoiler element and a vortex fin spoiler element.

[0015] Furthermore, the optimal distance is the distance between the lateral vortex core and the geometric center of the spoiler element in step S1; and the optimal cycle length is the optimal flow channel length in step S3.

[0016] Furthermore, the cross-section of the core zigzag heat exchange flow channel is one of a rectangle, a semicircle, or a trapezoid, the turbulence generator is located on the long side of the cross-section, and the turbulence generators in the core zigzag heat exchange flow channel of the cold fluid and the core zigzag heat exchange flow channel of the hot fluid are arranged symmetrically along the flow direction.

[0017] (III) Beneficial effects

[0018] The present invention provides a microchannel heat exchange method and heat exchanger with variable vortex efficiency, which have the following beneficial effects:

[0019] (1) The present invention optimizes the lateral vortex generated by the spoiler element into a longitudinal vortex by flow channel steering, so as to achieve a significant improvement in heat exchange performance with less increase in flow resistance. The optimized structure obtained by this method has a low processing cost and low requirements on processing technology, and can be better applied in production and life.

[0020] (2) The variable vortex efficiency-enhancing microchannel heat exchanger structure of the present invention is developed based on a microchannel design method for optimizing the vortex field. Compared with a conventional microchannel heat exchanger, its heat transfer performance is improved by 99.3%, and its compactness is significantly improved.

[0021] (3) The microchannel heat exchanger of the present invention can adjust the flow channel size, the size of the spoiler element and the number of the spoiler elements according to the usage scenario and the types of fluids on the cold and hot sides to achieve sufficient matching of heat exchange, thereby further improving the heat exchange efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The transverse eddy flow field formed by adding a spoiler element in the microchannel of the present invention;

[0023] Figure 2 The longitudinal eddy current field optimized according to the proposed design method of the present invention;

[0024] Figure 3 A three-dimensional model diagram of the microchannel heat exchanger of the present invention;

[0025] Figure 4 The hot fluid plate in the microchannel heat exchanger of the present invention;

[0026] Figure 5 It is a partial enlarged schematic diagram of the core tortuous flow channel of the microchannel heat exchanger of the present invention;

[0027] Figure 6 This is a schematic diagram of the power supply unit division result of the present invention;

[0028] Figure 7 A partial view of a cylindrical spoiler element of the present invention;

[0029] Figure 8 A partial view of a pit spoiler element of the present invention;

[0030] Fig. 9 This is a comparison diagram of heat transfer performance of the microchannel heat exchanger of the present invention;

[0031] Fig.10 This is a comparison chart of the flow resistance performance of the microchannel heat exchanger of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Research and development concept:

[0034] Adding a turbulent element to a microchannel can generate eddies to increase the turbulence intensity of the fluid, strengthen the mixing between the cold fluid and the hot fluid, and thus enhance the performance. However, due to the small size and limitations of processing conditions, the turbulent elements used in microchannels have a simple structure and a small size, and a large part of the eddy field formed is a transverse eddy. Previous studies have shown that under the same pressure loss conditions, longitudinal eddies have better enhanced heat transfer effects than transverse eddies. The difference between transverse eddies and longitudinal eddies is that the flow direction of the fluid in the transverse eddy is perpendicular to the eddy rotation axis, while the flow direction of the fluid in the longitudinal eddy is parallel to the eddy rotation axis. The present invention proposes a microchannel design method for optimizing the eddy field.

[0035] This embodiment provides a microchannel heat exchange method with variable vortex flow efficiency enhancement, comprising the following steps:

[0036] Firstly, the position of the transverse vortex is determined, and the numerical simulation analysis of the microchannel structure with the spoiler is carried out to determine the rotation axis direction and the rotation core position of the transverse vortex;

[0037] Secondly, the microchannel structure is optimized: by changing the direction of the channel at the position of the rotating core, the alignment between the main flow direction and the rotation axis direction is achieved to realize the conversion of transverse vortex to longitudinal vortex;

[0038] Finally, the performance of the optimized microchannel structure is analyzed, the thermal-hydraulic performance of the microchannel structure before and after optimization is compared and analyzed, and the flow channel length with the best heat transfer optimization effect is determined. The comparative analysis is based on the simulation software Ansys fluent, and the numerical simulation method is used to analyze the change law of the heat transfer performance of the optimized microchannel structure along the flow direction, so as to determine the flow channel length with the best heat transfer optimization effect.

[0039] like Figure 1 , adding spoiler elements in the microchannel forms a transverse eddy flow field effect diagram, such as Figure 2 The microchannel design method for optimizing the eddy flow field successfully optimizes the transverse eddy flow field in the microchannel into a longitudinal eddy flow field by turning the flow channel.

[0040] Reference Figure 3 to Figure 4 A heat exchanger for a microchannel heat exchange method with variable vortex efficiency enhancement is provided, comprising a heat exchange core 1, with hot and cold fluid inlet boxes 21 and hot and cold fluid outlet boxes 22, hot fluid plates 3 and cold fluid plates 4 connected to both sides of the heat exchange core 1, respectively. The heat exchange core 1 is formed by alternately welding the hot fluid plates 3 and the cold fluid plates 4, the hot fluid and the cold fluid enter the heat exchange core 1 from the hot and cold fluid inlet boxes 21, and exchange heat in a reverse flow, and flow out of the heat exchange core 1 from the hot and cold fluid outlet boxes 22, the hot and cold fluids flow in opposite directions in the heat exchange core, the hot fluid flows in from the H port and flows out from the h port; the cold fluid flows in from the C port and flows out from the c port.

[0041] The hot fluid plate 3 includes an inlet section 31, a core zigzag heat exchange channel 32 and an outlet section 33. The structure of the cold fluid plate 4 is completely consistent with that of the hot fluid plate 3. The channels of the inlet section 31 and the outlet section 33 are both straight, and the hot fluid channels are arranged equidistantly at certain intervals.

[0042] The core zigzag heat exchange flow channel 32 places the same or multiple spoiler elements at intervals of optimal period length along the flow direction. The flow channel streamline is multi-period zigzag, and the zigzag point is located at the optimal distance behind the spoiler element. The bending angle is 60-90°. The optimal period length is obtained by numerical simulation and varies with the type of spoiler element. For cylindrical spoiler elements, the optimal period length is 8mm, for pit spoiler elements, the optimal period length is 25mm, and for vortex fin spoiler elements, the optimal period length is 20mm. The optimal distance is obtained by numerical simulation and is the distance between the core position of the lateral vortex field and the geometric center of the spoiler element. For different spoiler elements, the calculated optimal distances are different. The optimal distance of the vortex fin spoiler element is 0.5mm; the optimal distance of the cylindrical spoiler element is 1mm, and the optimal distance of the pit spoiler element is 0.8mm.

[0043] Reference Figure 5 The core zigzag flow channels in the cold and hot fluid plates correspond to each other along the long sides of the cross-section, which can further increase the primary heat exchange area between the cold and hot fluids and thus enhance the heat exchange performance. In the core zigzag heat exchange flow channel 32, along the flow direction, the spoiler elements are distributed at the optimal distance in front of the inner wall surface 51 of the turning position 5. Because the cold and hot fluids have different flow directions, the spoiler elements are placed in opposite positions.

[0044] The spoiler element is one or a combination of the following structures: a cylindrical spoiler element, a pit spoiler element and a vortex fin spoiler element.

[0045] The optimal distance is the distance between the lateral vortex core and the geometric center of the spoiler element in step S1; the optimal cycle length is the optimal flow channel length in step S3.

[0046] The cross section of the core zigzag heat exchange channel 32 is one of a rectangle, a semicircle, or a trapezoid. The turbulence generator is located on the long side of the cross section. The turbulence generators in the core zigzag heat exchange channel 32 of the cold fluid and the core zigzag heat exchange channel 32 of the hot fluid are arranged symmetrically along the flow direction.

[0047] See attached Fig. 9 and Fig.10, respectively demonstrated the flow resistance performance and heat transfer performance of the traditional microchannel structure O-PCHE, the microchannel structure V-PCHE with added spoiler elements, and a variable vortex-enhanced microchannel heat exchanger structure VT-PCHE under different inlet mass flow conditions. When the inlet mass flow rate is 0.0005kg / s, the heat transfer performance of VT-PCHE increases by 99.3% compared with O-PCHE and 50.5% compared with V-PCHE heat exchanger. The flow resistance of VT-PCHE increases by 0.71KPa compared with O-PCHE and 0.48KPa compared with V-PCHE. The pressure drop increment is less than 1KPa, which has little effect on the heat exchanger and the entire system. The economy of VT-PCHE increases by 34.7% compared with O-PCHE heat exchanger and 20.98% compared with V-PCHE heat exchanger.

[0048] In summary, the variable vortex efficiency-enhanced microchannel heat exchanger structure VT-PCHE of the present invention achieves a significant improvement in heat transfer performance, a slight increase in flow resistance, and improved economy.

[0049] Embodiment 2

[0050] See attached Figure 6 The flow-disturbing element is a vortex fin flow-disturbing element, which is composed of a pair of symmetrical inclined vortex fins, with a fin inclination angle of 30-45°, a thickness of 0.05-0.1mm, a length of 0.3-0.6mm, a distance between the two fin heads 61 of 0.2-0.4mm, and a fluid flows from the fin head 61 to the fin tail 62. Compared with a smooth flow channel without a flow-disturbing element, the heat transfer performance is improved by 36.0%. The heat transfer performance is the best among the three flow-disturbing elements of vortex fins, cylinders and pits.

[0051] Embodiment 3

[0052] See attached Figure 7 The flow spoiler is a cylindrical flow spoiler 7, the radius of the cylinder is 0.1-0.3mm, and it is located on the inner wall surface 51 before the turning point. Compared with the smooth flow channel without a flow spoiler, the heat transfer performance is improved by 31.7%. The heat transfer performance optimization effect is the best among the three flow spoilers. The economic efficiency is the best among the three flow spoilers of vortex fins, cylinders and pits.

[0053] Embodiment 4

[0054] Participate in the Figure 8 The flow disturbance element is a concave flow disturbance element 8, the radius of the concave is 0.1-0.3mm, and it is located on the inner wall surface 51 before the turning point. Compared with the smooth flow channel without a flow disturbance element, the heat transfer performance is improved by 25.97%. Among the three flow disturbance elements of vortex fins, cylinders and concave pits, the flow performance is the best.

[0055] The above description is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application.

Claims

1. A microchannel heat exchange method with variable vortex efficiency enhancement, characterized in that: The steps include: S1. First, determine the position of the lateral vortex, perform numerical simulation analysis on the microchannel structure with the spoiler element, and determine the rotation axis direction and the rotation core position of the lateral vortex; S2. Optimization of microchannel structure: By changing the direction of the channel at the position of the rotating core, the alignment between the main flow direction and the rotation axis direction has been achieved to realize the conversion of transverse vortex to longitudinal vortex; S3. Analyze the performance of the optimized microchannel structure, compare and analyze the thermal and hydraulic performance of the microchannel structure before and after optimization, and determine the flow channel length with the best heat transfer optimization effect.

2. A microchannel heat exchange method with variable vortex flow efficiency enhancement according to claim 1, characterized in that: The comparative analysis in S3 is based on the simulation software Ansys fluent, and a numerical simulation method is used to analyze the variation of the heat transfer performance of the optimized microchannel structure along the flow direction.

3. A heat exchanger used in the microchannel heat exchange method with variable vortex efficiency enhancement as claimed in claim 1 or 2, characterized in that: The heat exchanger comprises a heat exchange core (1), and the heat exchange core (1) is respectively connected to a hot and cold fluid inlet box (21) and a hot and cold fluid outlet box (22), a hot fluid plate (3) and a cold fluid plate (4). The heat exchange core (1) is formed by alternately welding the hot fluid plates (3) and the cold fluid plates (4). The hot fluid and the cold fluid enter the heat exchange core (1) from the hot and cold fluid inlet box (21) and exchange heat in a countercurrent flow, and flow out of the heat exchange core (1) from the hot and cold fluid outlet box (22).

4. The heat exchanger of the microchannel heat exchange method with variable vortex flow efficiency enhancement according to claim 3 is characterized in that: The hot fluid plate (3) comprises an inlet section (31), a core zigzag heat exchange channel (32) and an outlet section (33), and the structure of the cold fluid plate (4) is completely consistent with that of the hot fluid plate (3).

5. The microchannel heat exchanger with variable vortex flow efficiency enhancement according to claim 4 is characterized in that: The core zigzag heat exchange flow channel (32) has the same or multiple flow disrupting elements arranged at intervals of optimal period length along the flow direction, and the flow channel streamline is multi-periodic zigzag, with the zigzag point located at the optimal distance behind the flow disrupting element and the bending angle being 60 to 90 degrees.

6. The microchannel heat exchanger with variable vortex flow efficiency enhancement according to claim 5 is characterized in that: The spoiler element is one or a combination of the following structures: a cylindrical spoiler element, a pit spoiler element and a vortex fin spoiler element.

7. The microchannel heat exchanger with variable vortex flow efficiency enhancement according to claim 5 is characterized in that: The optimal distance is the distance between the lateral vortex core and the geometric center of the spoiler element in step S1; the optimal cycle length is the optimal flow channel length in step S3.

8. The microchannel heat exchanger with variable vortex flow efficiency enhancement according to claim 5 is characterized in that: The cross section of the core zigzag heat exchange channel (32) is any one of rectangular, semicircular and trapezoidal, and the turbulence generator is located on the long side of the cross section.

9. The microchannel heat exchanger with variable vortex flow efficiency enhancement according to claim 8 is characterized in that: The positions of the turbulence generators in the core zigzag heat exchange channel (32) of the cold fluid and the core zigzag heat exchange channel (32) of the hot fluid are symmetrically arranged along the flow direction.

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