Dual thermal conductivity boiling optimization surface based on embedded epoxy resin square blocks

Abstract

The invention discloses a dual-thermal-conductivity boiling optimization surface based on embedded epoxy resin square blocks. The dual-thermal-conductivity boiling optimization surface comprises latticed epoxy resin arranged on a metal surface and the epoxy resin square blocks located in closed lattices. On the basis of the reticular epoxy resin, the epoxy resin square blocks are embedded in each independent metal area, so that a supplementary path for cold fluid to flow outwards from the center of an independent copper area is increased, the wetting effect of the epoxy resin is enhanced, and a higher boiling heat transfer coefficient h and a higher critical heat flux (CHF) are obtained.

Description

Technical Field

[0001] The invention relates to a technology in the field of boiling experiments, in particular to a dual-thermal conductivity boiling optimization surface based on embedded epoxy resin blocks. Background Art

[0002] A large number of existing studies have shown that changing the hydrophilicity, roughness or porosity of the heat transfer surface can enhance the boiling heat transfer characteristics. Traditional methods include preparing microstructures such as nano-coatings, micro-pillar arrays, etc. on the heating surface. However, these modified structures are often difficult to maintain in practical applications. For example, the coating may peel off or wear, and the microstructure may fail due to dirt accumulation or oxidation. Summary of the invention

[0003] In view of the shortcomings of the prior art, such as complicated steps, high cost and difficulty in long-term maintenance, the present invention proposes a dual thermal conductivity boiling optimized surface based on embedded epoxy resin blocks. On the basis of the mesh epoxy resin, epoxy resin blocks are embedded in each independent metal area, thereby increasing the supplementary path for the cold fluid to flow outward from the center of the independent copper area, strengthening the wetting effect of the epoxy resin, and obtaining a higher boiling heat transfer coefficient h and critical heat flux density (CHF).

[0004] The present invention is achieved through the following technical solutions:

[0005] The invention relates to a dual-thermal conductivity boiling optimization surface based on embedded epoxy resin blocks, comprising: a grid-shaped epoxy resin arranged on a metal surface and epoxy resin blocks located in each closed grid.

[0006] The grid-like epoxy resin is a crisscross stripe structure.

[0007] The present invention relates to a method for preparing the dual thermal conductivity surface, comprising:

[0008] Step 1: After using mechanical processing to make criss-cross stripes and square grooves on the copper block, use acetone, alcohol and deionized water to clean the sample in turn to remove impurities remaining on the sample surface.

[0009] Step 2: Immerse the sample in an alkaline solution and heat it in a water bath at 70° C. for 2 minutes to generate nano-scale copper oxide to enhance the adhesion between copper and epoxy resin. Then, wash the sample with deionized water and dry it in an oven.

[0010] The alkaline solution preferably contains 160 g / L of NaClO 2 and 10 g / L NaOH.

[0011] Step 3: Apply epoxy resin on the surface of the copper block with grooves and cure it at high temperature in an oven to achieve optimal adhesion strength.

[0012] Step 4: Use sandpaper of different meshes to polish from low to high to expose the copper, and finally rinse with deionized water and dry in an oven.

[0013] The present invention relates to the application of the dual thermal conductivity surface, which is carried out under atmospheric pressure and deionized water is selected as the working fluid. During the experiment, the pool boiling phenomenon is observed and recorded in real time by thermocouples and a data acquisition system, specifically including:

[0014] Step a: Turn on the preheater to heat the water to the saturation temperature and keep boiling for 30 minutes to remove non-condensable gases.

[0015] Step b, turn on the DC power supply, and the heating rod starts to heat the sample. When the temperature indicated by the thermocouple fluctuates less than 0.1°C within 1 minute, the working condition is considered stable, record the temperature data and increase the heating power. Repeat this step until the sample reaches the critical heat flux. The criterion for the critical heat flux is that the temperature indicated by the thermocouple rises sharply and cannot be stabilized. Once the critical heat flux is reached, the DC power supply needs to be turned off immediately.

[0016] Step c: In the subsequent data processing process, the heat flux density and boiling heat transfer coefficient are calculated through data such as temperature and heating area, and the boiling enhancement performance of each surface is compared in combination with the visual image. Technical Effects

[0017] By arranging epoxy resin blocks in the center of each closed metal grid surrounded by grid-like epoxy resin, the present invention further optimizes bubble dynamics, increases supplementary paths for cold fluid to flow outward from the center of the independent copper area, and strengthens the wetting effect of the epoxy resin compared to the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 (a) Axonometric view and (b) top view of the dual thermal conductivity sample embedded in an epoxy resin block;

[0019] In the figure: 1 metal surface, 2 grid-shaped epoxy resin, 3 epoxy resin block;

[0020] Figure 2 (a) is a dual thermal conductivity sample without embedding in epoxy resin block;

[0021] Figure 2 (b) Schematic diagram of the cold fluid supplementing the metal surface on the dual thermal conductivity sample embedded in the epoxy resin block;

[0022] Figure 3 (a) Boiling curve and (b) boiling coefficient curve of the block without embedding\embedded with epoxy resin;

[0023] Figure 4 (a) Boiling curve and (b) boiling coefficient curve of the block without embedding\embedded with epoxy resin;

[0024] Figure 5 for Figure 4 The heat flux is 2.3W / cm 2 and 2.7W / cm 2 The boiling image of the time;

[0025] Figure 6 for Figure 3 Boiling image when CHF occurs. DETAILED DESCRIPTION

[0026] like Figure 1 As shown, this embodiment relates to a dual thermal conductivity boiling optimized surface based on embedded epoxy resin blocks, including: a grid-like epoxy resin 2 arranged on a metal surface 1 and epoxy resin blocks 3 located in each closed grid, wherein: the grid-like epoxy resin 2 is a vertical stripe structure, which divides the metal surface into multiple independent metal areas, and epoxy resin blocks are embedded in each independent metal area.

[0027] The role of the epoxy resin block is to add a supplementary path for the cold fluid to flow outward from the center of the independent copper area on the basis of the strip or mesh epoxy resin stripes, thereby strengthening the wetting effect of the epoxy resin. Figure 2 Shown is a schematic diagram of the cold fluid replenishment of the metal surface on (a) a dual thermal conductivity sample (2x2) without epoxy resin blocks embedded and (b) a dual thermal conductivity sample (2x2 mesh structure) embedded with epoxy resin blocks. When there is no epoxy resin block in the center, bubbles are most likely to gather in the center of the copper area with the longest wetting path. When there is an epoxy resin block in the center, the cold fluid replenishes from the center to the outside at the same time, and the wetting effect is stronger. At the same time, since the cold fluid replenishes from multiple directions on the independent annular metal, bubbles are easier to detach, and the boiling heat transfer coefficient h of the dual thermal conductivity surface is also improved.

[0028] like Figure 3 The following are (a) boiling curves and (b) boiling coefficient curves of a 2x2 mesh structure without epoxy resin blocks and a 2x2 mesh structure with epoxy resin blocks. In the experiment, the metal part was copper. In order to control the variables, the copper ratio A of all dual thermal conductivity surface samples was 铜 / A 双热导率表面 Both are 60%. Figure 3 It can be seen that the boiling heat transfer coefficient h and critical heat flux CHF of the 2x2 mesh structure embedded with epoxy resin blocks are improved. Similar conclusions can be seen for the 3x3 mesh structure with more stripes and blocks, such as Figure 4 shown.

[0029] In addition, the wetting effect of the embedded epoxy resin blocks was also verified in the optical high-speed camera images. Figure 5 The heat flux is shown as 2.3W / cm 2 and 2.7W / cm 2 Boiling image of a 3x3 mesh structure. As shown in the figure, when the heat flux density is close, the dual thermal conductivity surface embedded in the epoxy resin block has a stronger wetting effect due to the cold fluid replenishing from the center to the outside at the same time, and the bubbles are easy to detach and the detachment diameter is smaller.

[0030] like Figure 6 The figure shows the boiling image of the 2x2 mesh structure when CHF occurs. As can be seen from the figure, when CHF occurs, the independent square copper area of ​​the sample not embedded in the epoxy resin block is covered with bubbles, while the sample embedded in the epoxy resin block can be seen to have wetted fluid on the block and bubbles detached upward from the copper area. The wetting enhancement effect of the epoxy resin block improves the CHF of the entire dual thermal conductivity surface.

[0031] In the pool boiling experiment, in order to promote the replenishment of liquid to the burn-out area, in addition to the embedding of epoxy resin in the center mentioned in the present invention to enhance the wetting effect and promote the violent external metal replenishment of cold fluid from epoxy resin to the bubble, micro-columns are prepared in different regions on the boiling surface to enhance the wicking effect or to prepare non-uniform contact angle / wettability surfaces, which are also used to optimize bubble dynamics in a directional manner and promote water replenishment to the burn-out area. However, these modified surfaces are difficult to maintain for a long time during actual application, such as the microstructure may fail due to dirt accumulation or oxidation, and the coating may peel off or wear. In addition, the process of these modified surfaces is complicated and the cost is high.

[0032] After specific practical experiments, on the basis of using grid-like epoxy resin stripes, epoxy resin blocks are set in the center of the closed metal grid, which further improves the wetting effect of the resin, optimizes the bubble dynamics, reduces the bubble detachment diameter and increases the detachment frequency, and improves the boiling heat transfer coefficient and critical heat flux density. Since the surface modification methods used in the present invention are all embedded in the surface, they are insensitive to dirt and oxidation, and can maintain boiling enhancement capabilities for a long time. At the same time, the sample preparation process used in the present invention is simple, the cost is low, and it has application potential.

[0033] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principle and purpose of the present invention. The protection scope of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. Each implementation scheme within its scope shall be subject to the constraints of the present invention.

Claims

1. A dual thermal conductivity boiling optimized surface based on embedded epoxy resin blocks, comprising: A grid-like epoxy resin disposed on the metal surface and epoxy resin blocks located within each closed grid; The grid-like epoxy resin is a crisscross stripe structure.

2. A method for preparing the dual thermal conductivity surface according to claim 1, characterized in that: include: Step 1: After making criss-cross stripes and square grooves on the copper block by mechanical processing, the sample is cleaned with acetone, alcohol and deionized water in turn to remove impurities remaining on the surface of the sample; Step 2, immersing the sample in an alkaline solution and heating it in a water bath at 70°C for 2 minutes to generate nano-scale copper oxide for enhancing the adhesion between copper and epoxy resin, and then washing the sample with deionized water and drying it in an oven; Step 3, coating the surface of the copper block with the grooves with epoxy resin and curing it at high temperature in an oven to achieve optimal adhesion strength; Step 4: Use sandpaper of different meshes to polish from low to high to expose the copper, and finally rinse with deionized water and dry in an oven.

3. The method according to claim 2, characterized in that: The alkaline solution contains 160 g / L of NaClO2 and 10 g / L of NaOH.

4. An application of the dual thermal conductivity surface according to claim 1, characterized in that: The experiment was carried out under atmospheric pressure, deionized water was selected as the working fluid, and the pool boiling phenomenon was observed and recorded in real time by thermocouples and a data acquisition system.

5. The use according to claim 4, characterized in that include: Step a, turning on the preheater to heat the water to the saturation temperature and keeping boiling for 30 minutes to remove the non-condensable gas; Step b, turn on the DC power supply, and the heating rod starts to heat the sample; when the temperature indicated by the thermocouple fluctuates less than 0.1°C within 1 minute, the working condition is considered stable, record the temperature data and increase the heating power, and repeat this step until the sample reaches the critical heat flux density; Step c: In the subsequent data processing process, the heat flux density and boiling heat transfer coefficient are calculated through data such as temperature and heating area, and the boiling enhancement performance of each surface is compared in combination with the visual image.

Images