JP2012013396A - Method of manufacturing heat transfer member, and heat transfer member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an irregular structure on the surface of a material in a short time.SOLUTION: A heat transfer member having the irregular structure on the surface is manufactured by repeating the processing of forming holes 2 by irradiating the surface of the material 1 with the high density energy beam 11 by using a high density energy beam irradiation device 10 in the direction along the surface with pitches larger than a fixed pitch.

Description

  Embodiments described herein relate generally to a heat transfer member manufacturing method and a heat transfer member applied to a heat transfer tube, a heat exchange device, and the like.

  Heat transfer members, such as cooling fins, applied to heat transfer tubes and cooling devices of electronic devices are designed to improve heat transfer by increasing the effective heat transfer area. In order to increase the effective heat transfer area, fine machining is generally performed. Even when fins and grooves are formed in the heat transfer tube, complicated and fine processing is performed (for example, see Patent Document 1).

JP 2009-14304 A

  As described above, conventionally, in order to improve the heat transfer of the heat transfer member, a complicated and fine structure is formed. However, since the processing is difficult, there is a problem that the number of processing steps increases.

  In view of the above circumstances, it is desired to provide a technique for forming a concavo-convex structure on the material surface in a short time.

  According to the embodiment, the process of irradiating the surface of the material with the high-density energy beam irradiation device to form the holes using the high-density energy beam irradiation apparatus is repeatedly performed at a certain pitch in the direction along the surface. By this, the manufacturing method of the heat-transfer member characterized by manufacturing the heat-transfer member which has an uneven structure on the surface is provided.

The figure which shows an example of the manufacturing method of the heat-transfer member which concerns on one Embodiment of this invention. The figure which shows the example which arrange | positions an irradiation spot in a permutation on the surface of a material. The figure which shows the example which arrange | positions an irradiation spot at random on the surface of material. The graph which shows the relationship between an electric current (mA) and a frequency (Hz). The table | surface which shows the data of "hole diameter (mm)", "depth (micrometer)", "hole diameter / depth", and "heat transfer ratio" for every test piece. 6 is a graph showing the relationship between “hole diameter / depth” and “heat transfer coefficient increase rate” based on the data of FIG. 5. The graph which shows the relationship between "depth" and "heat transfer rate increase rate" based on the data of FIG. The graph which shows the range of the ratio of the diameter and the depth of the hole formed with a high-density energy beam. A table showing data on “void ratio”, “COSθc”, and “contact angle” calculated for each “hole diameter” using Cassie's formula. The table | surface which shows the data of the "void ratio" for every "hole diameter" of each test piece with which the malfunction did not arise. 10 is a graph showing the relationship between “void ratio” and “contact angle (degrees)” based on the data in FIG. 9.

  Embodiments of the present invention will be described below with reference to the drawings.

(Basic items)
Drawing 1 is a figure showing an example of the manufacturing method of the heat transfer member concerning one embodiment of the present invention.

  In the present embodiment, the high density energy beam irradiation apparatus 10 that irradiates the high density energy beam is used to irradiate the surface of the material 1 (such as a plate member made of a metal such as stainless steel) with the high density energy beam 11. The heat transfer member having a concavo-convex structure on the surface is manufactured by repeatedly performing the process of forming the film at a certain pitch (hereinafter referred to as “irradiation pitch”) in the direction along the surface. This heat transfer member is applied to a heat transfer tube, a heat exchange device, or the like.

  In general, in a conventional technique, a high-density energy beam is used for welding, surface modification, mirror finishing, and is used by continuously irradiating an object. That is, processing is performed while overlapping irradiation spots. On the other hand, in the present embodiment, the high-density energy beam is used for manufacturing a heat transfer member having a concavo-convex structure, and is not continuously irradiated onto the material 1 but intermittently at an irradiation pitch. , I.e., by irradiating with irradiation spots spaced apart, a plurality of holes 2 are formed on the surface of the material 1, thereby forming a concavo-convex structure over the entire surface.

  As a specific example of the high-density energy beam irradiation apparatus 10, an electron beam irradiation apparatus that irradiates an electron beam or a laser irradiation apparatus that irradiates a laser may be used. In addition, an irradiation apparatus that irradiates arcs, plasmas, ions, millimeter waves, or the like can be applied.

  The high-density energy beam irradiation apparatus 10 automatically scans the high-density energy beam 11 in accordance with CAD data including dimensional data such as individual irradiation positions and irradiation pitches on the surface of the material 1 to be irradiated with the high-density energy beam 11. Irradiation can be performed at the same time, and the irradiation speed can be as high as 10,000 mm / sec. Therefore, the processing time can be extremely shortened, and the concavo-convex structure can be formed on the material surface in a short time.

  The formation of a concavo-convex structure on the material surface in such a short time increases the effective heat transfer area of the material surface and induces separation and self-excited vibration at the concavo-convex portion of the fluid, thereby developing the temperature boundary layer. Is suppressed and heat transfer is promoted.

(Irradiation spot arrangement example 1)
For example, the irradiation spots are arranged in a permutation on the surface of the material 1. In this case, the high-density energy beam irradiation apparatus 10 has a plurality of holes 2 along the surface of the material 1 as shown in FIG. 1 according to CAD data for aligning irradiation spots in a permutation on the surface of the material 1. The high-density energy beam 11 is scanned so as to be arranged in a straight line with a certain pitch. The result of scanning in this way is shown in FIG. Moreover, the cross-sectional shape shown to arrow AA in Fig.2 (a) is shown in FIG.2 (b). As described above, since the plurality of holes 2 are regularly arranged on the surface of the material 1 at a constant pitch, it is possible to promote heat transfer more effectively.

(Irradiation spot arrangement example 2)
As another example, the irradiation spots can be randomly arranged on the surface of the material 1. In this case, the high-density energy beam irradiation apparatus 10 has a plurality of holes 2 randomly formed on the surface of the material 1 according to CAD data for randomly arranging irradiation spots on the surface of the material 1 as shown in FIG. The high-density energy beam 11 is scanned so as to be disposed at the position. By arranging the plurality of holes 2 randomly on the surface of the material 1 in this way, the heat input accompanying the irradiation of the high-density energy beam on the surface of the material 1 becomes random, so that the influence of heat on the material 1 is effective. Can be dispersed. This method is suitable for a thin plate or an elongated material that is easily affected by heat input.

(Range of hole diameter)
The diameter (hole diameter) of the hole 2 formed by the high-density energy beam 11 is desirably in the range of 0.05 mm to 0.5 mm due to the nature of the high-density energy beam. Within this range, the circular hole 2 can be formed without difficulty without breaking the shape. Formation of such a circular hole 2 on the surface of the material 1 induces separation and self-excited vibration at the uneven portion of the fluid, thereby suppressing the development of the temperature boundary layer and promoting heat transfer. The

  In addition, the range of the hole diameter shown here indicates a range that is considered effective at the present stage, and indicates that it is effective at least within this range. Therefore, depending on the results of further studies in the future, it may become clear that the effective range is wider than the range shown here.

(Irradiation pitch, current x frequency range)
In order to appropriately form the circular holes 2 at a set pitch on the surface of the material 1, the relationship between the output current when scanning the high-density energy beam 11 and the scanning speed which is the reciprocal of the frequency is considered. It is important to. That is, if the current value is small and the scanning speed is high, the power necessary for forming the shape of the hole 2 cannot be obtained, and it becomes difficult to form a desired uneven shape. On the other hand, when the output current value is increased and the scanning speed is decreased, the circular shape cannot be formed, and the shape tends to be elliptic.

  Here, the relationship between current (mA) and frequency (Hz) is shown in the flag of FIG. From this graph, it can be seen that it is necessary to set so that the value obtained by multiplying the current (mA) and the frequency (Hz) falls within a certain irradiation condition range 3.

  Therefore, in order to form a desired uneven shape, it is necessary to consider an appropriate combination of the current value and the scanning speed in addition to the irradiation pitch. In the present embodiment, the irradiation pitch is set within a range of at least “0.2 mm to 0.8 mm”, and a value obtained by multiplying a current (mA) and a frequency (Hz) for scanning a high-density energy beam is obtained. By setting at least within the range of “200 to 2000”, a power necessary for forming the shape of the hole 2 can be obtained, and a circular hole that does not become an ellipse can be formed. It has been found that an uneven shape can be formed.

  In addition, the range of the irradiation pitch and the range of the current × frequency shown here indicate ranges that are considered to be effective at the present stage, and indicate that they are effective at least within this range. Therefore, depending on the results of further studies in the future, it may become clear that the effective range is wider than the range shown here.

(Range of hole diameter / depth)
In boiling heat transfer, heat transfer is said to be improved by bubbles generated from holes. Even when the depth of the hole is shallow, it contributes to the generation of bubbles. Therefore, in order to investigate the ratio between the hole diameter and the depth for improving the heat transfer, a test was conducted to measure the heat transfer ratio in boiling heat transfer using a plurality of test pieces having different hole diameters and depths. The test results are shown in FIGS.

  FIG. 5 summarizes data of “hole diameter (mm)”, “depth (μm)”, “hole diameter / depth”, and “heat transfer ratio” for each test piece.

  Specimen No. 0 is a flat plate that has not been drilled, and the heat transfer coefficient of this flat plate is 1 (reference). Specimen No. 1-No. No. 6 has different “hole diameters” and “depths”, and as “heat transfer ratio”, different measurement results were obtained as shown in FIG. However, test piece No. 2 and no. Regarding 5, the measurement result of “heat transfer coefficient” could not be obtained because a defect occurred during the test.

  6 is based on the data shown in FIG. 5, “hole diameter / depth” and “heat transfer coefficient increase rate” (“heat transfer ratio when the heat transfer coefficient of the test piece No. 0 which is a flat plate is 1”. ]) In a graph. In addition, the test piece No. in which the defect occurred 2 and no. The data of 5 is not described. For reference, FIG. 7 shows a graph of the relationship between “depth” and “heat transfer coefficient increase rate” based on the data in FIG. 5. Among the graphs of FIG. 5 and FIG. 6, a certain degree of characteristics can be captured particularly from FIG. That is, as shown in FIG. 8, it can be seen that when the “hole diameter / depth” is equal to or greater than a certain value, the “heat transfer coefficient increase rate” can be equal to or greater than a certain value. However, considering the actual actual hole diameter and depth that the high-density energy beam 11 can actually form, the lower limit of “hole diameter / depth” may be “5” and the upper limit may be “12”. It is reasonable. That is, by setting the ratio between the diameter and the depth of the hole formed by the high-density energy beam 11 within a range of at least “5 to 12” as indicated by reference numeral R1 in FIG. It can be seen that improved heat transfer can be achieved.

  The range of the hole diameter / depth shown here indicates a range that is considered effective at the present stage, and indicates that it is effective at least within this range. Therefore, depending on the results of further studies in the future, it may become clear that the effective range is wider than the range shown here.

(Porosity)
In general, it is said that the heat transfer rate is high when the water repellency of the material surface is high. In boiling heat transfer, when the water repellency of the surface on which the holes are formed is high, bubbles are easily detached. This water repellency is related to the ratio of the area occupied by the air region on the material surface. That is, it can be said that the water repellency is related to the void ratio indicating the ratio of the area of the material surface where no hole exists. Examples of the index indicating the degree of water repellency include the contact angle between the material surface and the water droplet when the water droplet is dropped on the material surface. As the contact angle is higher, the water droplet state becomes closer to a spherical shape, so that the water repellency is improved. Therefore, in order to investigate the porosity for improving heat transfer, the relationship between the porosity and the contact angle was examined.

FIG. 9 is a table summarizing data of “void ratio”, “COSθc”, and “contact angle” calculated for each “hole diameter” using Cassie's formula “COSθc = Φc (COSθl + 1) −1”. is there. However, (theta) c shows the contact angle of Cassie and (PHI) c shows a porosity. θl indicates the contact angle without holes, and 65 degrees is applied in this calculation based on the experimental results. The total area is 1 mm ² .

  On the other hand, FIG. 10 is a table summarizing data of “void ratio” for each “hole diameter” of individual test pieces in which the above-mentioned problems did not occur.

  FIG. 11 is a graph showing the relationship between “void ratio” and “contact angle (degrees)” based on the data in FIG. 9. In FIG. 11, data indicated by square dots corresponds to the data of FIG. From this graph, it is possible to capture the characteristic that the “contact angle” can be increased and the water repellency can be increased by decreasing the “void ratio”. It is said that the water repellency is generally improved when the “contact angle” is 90 degrees or more. However, considering the realistic contact angle and porosity that can be actually formed, it is appropriate that the lower limit of the porosity is “0.5” and the upper limit is “0.7”. That is, it can be seen that heat transfer can be improved by setting the porosity on the surface of the material 1 to a range of at least “0.5 to 0.7” as indicated by the symbol R2 in FIG. As a result, among the individual test pieces shown in FIG. 3, no. 4, no. 6 is suitable for improving heat transfer. In FIG. 11, the data indicated by round dots is the test piece No. 3, no. 4, no. This corresponds to 6 data.

  The porosity range shown here indicates a range that is considered effective at the present stage, and indicates that it is effective at least within this range. Therefore, depending on the results of further studies in the future, it may become clear that the effective range is wider than the range shown here.

  As described above in detail, according to the heat transfer member manufacturing method of the present embodiment, a desired uneven structure can be formed on the material surface in a short time, and heat transfer can be further improved.

  The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  DESCRIPTION OF SYMBOLS 1 ... Material, 2 ... Hole, 3 ... Irradiation condition range, 10 ... High density energy beam irradiation apparatus, 11 ... High density energy beam.

Claims (10)

  By irradiating the surface of the material with a high-density energy beam using a high-density energy beam irradiation device to form holes, it is repeatedly performed at a certain pitch in the direction along the surface. The manufacturing method of the heat-transfer member characterized by manufacturing the heat-transfer member which has this.   2. The method of manufacturing a heat transfer member according to claim 1, wherein the high-density energy beam is scanned so that the plurality of holes are linearly arranged at a constant pitch along the surface of the material. Manufacturing method of heat transfer member.   2. The method of manufacturing a heat transfer member according to claim 1, wherein the high-density energy beam is scanned so that the plurality of holes are randomly arranged on the surface of the material.   The method for manufacturing a heat transfer member according to any one of claims 1 to 3, wherein the diameter of the hole formed by the high-density energy beam is in a range of 0.05 mm to 0.5 mm. Manufacturing method of thermal member.   5. The method of manufacturing a heat transfer member according to claim 1, wherein an irradiation pitch is in a range of 0.2 mm to 0.8 mm, and a current (mA) for scanning a high-density energy beam; A method for producing a heat transfer member, characterized in that a value obtained by multiplying a frequency (Hz) is in a range of 200 to 2000.   The method for manufacturing a heat transfer member according to any one of claims 1 to 5, wherein the high-density energy beam is an electron beam.   The method for manufacturing a heat transfer member according to any one of claims 1 to 5, wherein the high-density energy beam is a laser.   In the manufacturing method of the heat-transfer member of any one of Claim 1 thru | or 7, the ratio of the diameter and the depth of the hole formed with a high-density energy beam was made into the range of 5-12. Manufacturing method of heat transfer member.   In the manufacturing method of the heat-transfer member of any one of Claims 1 thru | or 8, the porosity which shows the ratio of the area of the part which does not have a hole in the surface of material is in the range of 0.5-0.7. A method for producing a heat transfer member.   Irregular structures are formed on the surface by repeatedly performing a process of irradiating the surface of the material with a high-density energy beam irradiation device to form holes by using a high-density energy beam irradiation device at a predetermined pitch or more in the direction along the surface. A heat transfer member formed.

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