JP2005282914A - Evaporator for heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an evaporator for a heat exchanger capable of improving cooling performance of the heat exchanger. <P>SOLUTION: This evaporator for the heat exchanger comprises a refrigerant flow channel 3 for circulating the refrigerant, and a heat transfer face 2a kept into contact with the refrigerant in the refrigerant flow channel 3, and the phase of at least a part of the refrigerant kept into contact with the heat transfer face 2a is changed from liquid to gas. The heat transfer face 2a has an uneven surface 13 having specific surface area of 15cm<SP>2</SP>or more per 1cm<SP>2</SP>, and surface roughness Ry of 30μm or more. The heat transfer face 2a has the uneven surfaces 13 linearly formed along the circulating direction of the refrigerant and an even surface 14 linearly formed between the uneven surfaces 13, 13. The total area of the uneven surface 13 is wider than the total area of the even surface 14. The heat transfer face 2a is made out of an aluminum member, and the uneven surface 13 is formed by etching the aluminum member. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an evaporator for a heat exchanger that changes a phase of at least a part of a refrigerant from a liquid to a gas.

  2. Description of the Related Art Conventionally, there is known an evaporator for a heat exchanger that includes a refrigerant flow path through which a refrigerant flows and a heat transfer surface that contacts the refrigerant in the refrigerant flow path. In the heat exchanger evaporator, heat is transferred from the heat transfer surface to the refrigerant by the phase change of the refrigerant in contact with the heat transfer surface from a liquid to a gas.

  In the heat transfer, bubbles are generated when the refrigerant undergoes a phase change from a liquid to a gas. Generally, the bubbles are not generated at the boiling point of the refrigerant, but bubble nuclei are generated at a temperature below the boiling point, Bubble nuclei grow into bubbles. Therefore, in order to improve the cooling capacity of the heat exchanger, it is effective to lower the temperature at which bubble nuclei are generated. For this reason, the heat transfer surface is uneven as nucleation sites where bubble nuclei are generated. Provision is made (see, for example, Patent Document 1).

The unevenness may be 0.1 mm or more by machining or the like. However, development of a technique that can further improve the cooling capacity of the heat exchanger is desired.
JP 2000-18867 A JP-A-7-198290

  An object of this invention is to provide the evaporator for heat exchangers which eliminates this inconvenience and can improve the cooling capacity of a heat exchanger.

  In order to achieve such an object, the present inventors have repeatedly studied, and in order to improve the cooling capacity of the heat exchanger, the unevenness formed on the heat transfer surface is further reduced, and the It has been found that it is effective that the unevenness has a specific surface area in a specific range and a surface roughness in a specific range, and the present invention has been achieved.

Accordingly, the present invention includes a refrigerant flow path through which a refrigerant flows and a heat transfer surface in contact with the refrigerant in the refrigerant flow path, and at least a part of the refrigerant in contact with the heat transfer surface is formed from a liquid. In the evaporator for a heat exchanger for changing the phase to gas, the heat transfer surface has a specific surface area of 15 cm ² or more per 1 cm ² , and the average of unevenness measured between any two points on the heat transfer surface The surface roughness Ry shown by the sum Rp + Rv of the maximum height Rp and the maximum depth Rv with respect to the average value when the value is used as a reference is provided.

  In the evaporator for a heat exchanger according to the present invention, the concavo-convex surface acts as a nucleation site, so that bubble nuclei are easily generated. Therefore, according to the evaporator for heat exchangers of the present invention, the bubble nuclei can be generated at a lower temperature, and the cooling ability of the heat exchanger can be improved.

  By the way, if bubble nuclei are easily generated as described above, the bubble generation density on the heat transfer surface increases, and the flow of the refrigerant downstream may be hindered. In this case, a hot spot is generated on the heat transfer surface, and heat transfer becomes uneven.

  Therefore, in the heat exchanger evaporator of the present invention, the heat transfer surface forms a line between the uneven surface formed by forming a line along the flow direction of the refrigerant and the uneven surface. And a non-concave surface formed. As described above, by alternately arranging the uneven surface and the non- uneven surface formed in the form of a line, it is possible to prevent hot spots from being generated on the heat transfer surface and to perform heat transfer uniformly. be able to.

  In addition, as described above, when the uneven surface and the non- uneven surface formed in a line are alternately arranged, the heat transfer surface is prevented from being generated and the heat transfer is made uniform. In order to carry out, it is preferable that the total area of the uneven surface is larger than the total area of the non- uneven surface.

  The heat transfer surface is preferably made of an aluminum-based member such as an aluminum alloy because of its high thermal conductivity. At this time, the uneven surface can be formed by etching the aluminum-based member.

  A technique for improving the hydrophilicity of aluminum fins by etching aluminum fins for heat exchangers is known (see, for example, Patent Document 2). However, this technique improves the hydrophilicity of the aluminum fins, thereby making it easy to remove moisture condensed on the aluminum fins. There is no description or suggestion.

  Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is an explanatory sectional view showing the configuration of the evaporator for heat exchanger of the present embodiment, and FIG. 2 is a graph for explaining the definition of the surface roughness Ry. 3 is a plan view of a configuration example of the heat exchanger evaporator shown in FIG. 1, and FIG. 4 is a plan view of another configuration example of the heat exchanger evaporator shown in FIG.

  As shown in FIG. 1, an evaporator 1 for a heat exchanger according to this embodiment includes an aluminum alloy evaporator body 2 and a fluororesin lid body that is closed by the evaporator body 2 to form a refrigerant flow path 3. 4, and the inner surface side of the evaporator body 2 is a heat transfer surface 2 a. The refrigerant flow path 3 is connected to a flow path inlet 3a for supplying the refrigerant and a flow path outlet 3b for discharging the refrigerant. Further, a ceramic heater 6 is disposed on the outer surface of the evaporator body 2 as a heat source via a copper chip 5, and the ceramic heater 6 is a sheet-type alumel for temperature measurement on the side opposite to the copper chip 5. A chromel thermocouple 7 is provided.

  The evaporator body 2, the lid body 4, the copper chip 5, the ceramic heater 6, and the thermocouple 7 are sandwiched between two silicon rubber sheets 8a, 8b, 9a, and 9b from both outsides, and further, the silicon rubber sheets 8a and 8b. , 9a and 9b are sandwiched between stainless plates 10a and 10b from the outside. The evaporator body 2, the lid 4, the copper chip 5, the ceramic heater 6, and the thermocouple 7 are bolted by bolts 11 that penetrate the stainless steel plates 10 a and 10 b and nuts 12 that are screwed to the bolts 11. The whole is crimped uniformly.

Here, an uneven surface is formed on the heat transfer surface 2 a facing the refrigerant flow path 3. The uneven surface can be formed by etching the heat transfer surface 2a of the evaporator body 2 made of aluminum alloy, the specific surface area per 1 cm ² is 15 cm ² or more, and the surface roughness Ry is 30 μm or more. It has become.

  The specific surface area is a value measured by the BET method determined from the adsorption amount of nitrogen gas. The surface roughness Ry is a value calculated as follows from, for example, the unevenness value measured between any two points on the heat transfer surface 2a by a contact-type surface roughness meter.

  First, when unevenness is measured between two arbitrary points A and B on the heat transfer surface 2a, a graph like a line L shown in FIG. 2 is obtained. Therefore, for the line L, the average value m of the unevenness is calculated. Then, the maximum height Rp and the maximum depth Rv are obtained on the basis of the average value m, and the sum Rp + Rv of both is defined as the surface roughness Ry.

  The etching can be performed by a method known per se. For example, in the case of using a ferric chloride aqueous solution, the conditions may be appropriately set within the range of the treatment liquid concentration of 5 to 30% by weight, the treatment temperature of 15 to 40 ° C., and the treatment time of 1 to 5 minutes.

  In the evaporator 1, the liquid refrigerant supplied from the flow path inlet 3 a and circulated through the refrigerant flow path 3 comes into contact with the heat transfer surface 2 a in the refrigerant flow path 3, and heat input from the ceramic heater 6. The refrigerant is heated by exchanging heat with it, and a part of the refrigerant is vaporized. Then, the heated liquid refrigerant and the vaporized refrigerant vapor are discharged from the flow path outlet 3b.

  At this time, since the uneven surface is formed on the heat transfer surface 2a, the refrigerant can generate bubble nuclei at a lower temperature using the uneven surface as a nucleation site. As a result, when the evaporator 1 is used for a heat exchanger, an excellent cooling ability can be obtained in the heat exchanger.

  In the evaporator 1, as shown in FIG. 2, the uneven surface 13 may be formed on the entire surface of the heat transfer surface 2a as long as the specific surface area and the surface roughness satisfy the above conditions. 3, the uneven surface 13 is formed on the heat transfer surface 2 a as a line along the flow direction of the refrigerant, and the non-concave surface 14 without unevenness is formed between the uneven surfaces 13 and 13. It is preferably formed in a strip. By doing as shown in FIG. 3, it is possible to prevent heat spots from being generated on the heat transfer surface 2a without disturbing the flow of the refrigerant to the downstream side, and to perform heat transfer uniformly.

  Next, examples of the present invention and comparative examples will be described.

  The evaporator 1 for heat exchangers of Examples 1 to 6 has the configuration shown in FIG. 1 and an evaporator main body 2 made of an aluminum alloy (A5052) material of 24 mm × 20 mm × 1 mm, and fluorine of 24 mm × 20 mm × 3.2 mm. A coolant channel 3 was formed between the resin lid 4 and the resin lid 4. A space of 1 mm is provided between the evaporator main body 2 and the fluororesin lid 4. The channel inlet 3a and the channel outlet 3b have an outer diameter of 3.18 mm and an inner diameter of 1.5 mm.

The evaporator main body 2 is polished to a mirror finish by polishing the inner surface side, and then the region that becomes the heat transfer surface 2a facing the refrigerant flow path 3 is etched with a ferric chloride aqueous solution, as shown in FIG. The uneven surface 13 was formed. Uneven surface 13, the conditions of the etching, the treatment liquid concentration from 5 to 30 wt%, treatment temperature 15 to 40 ° C., by adjusting the range of the processing time 1-5 minutes, the specific surface area per 1 cm ² is 15cm ² In addition, the surface roughness Ry is set to be 30 μm or more and has a depth of 118 μm. In addition, the said depth is an average value which measured the depth of ten places along the distribution direction of a refrigerant | coolant in the center part of the width direction of the uneven | corrugated surface 13. FIG.

  Further, a ceramic heater 6 of 10 mm × 20 mm × 1.75 mm is disposed on the outer surface of the evaporator body 2 via a copper chip 5 of 23 mm × 14 mm × 1.5 mm, and the copper chip 5 of the ceramic heater 6 is disposed. A sheet-type alumel-chromel thermocouple 7 having a size of 19.1 mm × 9.4 mm × 0.3 mm was disposed on the opposite side. The copper chip 5 has a contact surface size of 14 mm × 14 mm with respect to the outer surface of the evaporator body 2, and has a central portion along the refrigerant flow direction, 4 mm upstream and downstream from the central portion, respectively. Holes with a diameter of 0.3 mm are drilled at three positions from the side to the center, and the temperature of the center can be measured by inserting thermocouples.

  The evaporator body 2, the lid 4, the copper chip 5, the ceramic heater 6, and the thermocouple 7 are sandwiched between 2 mm thick silicon rubber sheets 8a, 8b, 9a, 9b, and further sandwiched between stainless plates 10a, 10b. The bolt 11 and the nut 12 are bolted together, and the whole is uniformly crimped.

  Next, cooling water as a refrigerant flows through the refrigerant flow path 3 at a flow rate of 2 g / min and an inlet temperature of 95 ° C., and power of 50 W is supplied to the ceramic heater 6 to measure the temperature of the pure copper chip 5 and perform heat exchange. The cooling capacity of the evaporator 1 was evaluated. The results are shown in Table 1.

Table 1 also shows the specific surface area of the uneven surface 13 measured by the BET method and the surface roughness of the uneven surface 13 measured by a contact-type surface roughness meter.
[Comparative Example 1]
The evaporator 1 for the heat exchanger of Comparative Example 1 was polished except that the inner surface side of the evaporator body 2 was polished to a mirror finish, and then etching was not performed, and the uneven surface 13 was not formed at all on the heat transfer surface 2a. It has the completely same structure as Examples 1-6. Therefore, in this comparative example, the heat transfer surface 2a is in a state of being mirror-finished.

  Next, the cooling capacity of the exchanger evaporator 1 was evaluated in exactly the same way as in Examples 1-6. The results are shown in Table 1.

Table 1 also shows the specific surface area of the heat transfer surface 2a measured by the BET method and the surface roughness of the heat transfer surface 2a measured by the contact-type surface roughness meter.
[Comparative Examples 2 to 5]
Heat exchanger evaporator 1 of Comparative Example 2-5, by adjusting the conditions of the etching, a specific surface area of less than 15cm ² of 1 cm ² per uneven surface 13, or, the surface roughness Ry is more 30μm Except as described above, the configuration is exactly the same as in the first to sixth embodiments.

  Next, the cooling capacity of the exchanger evaporator 1 was evaluated in exactly the same way as in Examples 1-6. The results are shown in Table 1.

  Table 1 also shows the specific surface area of the uneven surface 13 measured by the BET method and the surface roughness of the uneven surface 13 measured by a contact-type surface roughness meter.

表１から、１ｃｍ²当たりの比表面積が１５ｃｍ²以上、かつ、面粗度Ｒyが３０μｍ以上となっている凹凸面１３を備える熱交換器用蒸発器１（実施例１〜６）は、凹凸面１３が形成されていない場合（比較例１）に対してはもちろんのこと、凹凸面１３の１ｃｍ²当たりの比表面積が１５ｃｍ²以上であるが面粗度Ｒyが３０μｍ未満の場合（比較例２，３）、面粗度Ｒyが３０μｍ以上であるが１ｃｍ²当たりの比表面積が１５ｃｍ²未満である場合（比較例４，５）と比較しても、純銅チップ５の各部の温度が低く、優れた冷却能力を備えていることが明らかである。

From Table 1, the heat exchanger evaporator 1 (Examples 1 to 6) including the uneven surface 13 having a specific surface area per 1 cm ² of 15 cm ² or more and a surface roughness Ry of 30 μm or more is an uneven surface. As a matter of course, the case where 13 is not formed (Comparative Example 1), the specific surface area per 1 cm ^{2 of the} uneven surface 13 is 15 cm ² or more, but the surface roughness Ry is less than 30 μm (Comparative Example 2). , 3), even when compared with the case where the specific surface area per but 1 cm ² surface roughness Ry is 30μm or more is less than 15cm ² (Comparative examples 4 and 5), lower temperature of each part of the pure copper chip 5, It is clear that it has excellent cooling capacity.

  In the evaporator 1 for heat exchangers of Examples 7 and 8, the inner surface side of the evaporator main body 2 is polished and mirror-finished, and then a mask having a predetermined shape is masked in the region that becomes the heat transfer surface 2a facing the refrigerant flow path 3. 4 and etching with a ferric chloride aqueous solution, as shown in FIG. 4, the uneven surface 13 forming a line along the flow direction of the refrigerant, and the uneven surface forming a line between the uneven surfaces 13, 13 Except that the surface 14 is formed, the configuration is exactly the same as in the first to sixth embodiments. In addition, the non-concave surface 14 is in a state in which the mirror surface is finished, and is a substantially smooth surface.

  Table 2 shows the width and depth of the uneven surface 13, the number of filaments, and the width of the non-concave surface 14 in the evaporator 1 for heat exchangers of Examples 7 and 8. In addition, the said depth is an average value which measured the depth of ten places along the distribution direction of a refrigerant | coolant in the center part of the width direction of the uneven | corrugated surface 13. FIG.

表２から、実施例７，８の熱交換器用蒸発器１では、凹凸面１３の総面積が非凹凸面１４の総面積よりも狭くなっていることがわかる。

From Table 2, it can be seen that in the heat exchanger evaporator 1 of Examples 7 and 8, the total area of the uneven surface 13 is narrower than the total area of the non-uneven surface 14.

  Next, in exactly the same way as in Examples 1 to 6, the cooling capacity of the exchanger evaporator 1 in Examples 7 and 8 was evaluated. The results are shown in Table 3.

  Table 3 also shows the specific surface area of the uneven surface 13 measured by the BET method and the surface roughness of the uneven surface 13 measured by a contact-type surface roughness meter.

表３から、１ｃｍ²当たりの比表面積が１５ｃｍ²以上、かつ、面粗度Ｒyが３０μｍ以上となっている凹凸面１３を冷媒の流通方向に沿って線条をなして形成し、凹凸面１３，１３間に線条をなす非凹凸面１４を形成した熱交換器用蒸発器１（実施例７，８）は、伝熱面２ａとなる領域全てを凹凸面１３とした場合（実施例１〜６）よりもさらに優れた冷却能力を備えていることが明らかである。

From Table 3, the irregular surface 13 having a specific surface area per 1 cm ² of 15 cm ² or more and a surface roughness Ry of 30 μm or more is formed along the flow direction of the refrigerant to form the irregular surface 13. , 13 is a heat exchanger evaporator 1 (Examples 7 and 8) in which a non-concave surface 14 forming a line is formed, when the entire surface to be the heat transfer surface 2a is an uneven surface 13 (Examples 1 to 8). It is clear that the cooling capacity is even better than 6).

  The evaporator 1 for heat exchangers of Examples 9 to 13 has exactly the same configuration as that of Examples 7 and 8, except that the total area of the uneven surface 13 is larger than the total area of the non- uneven surface 14. .

  Table 4 shows the width and depth of the uneven surface 13 in the evaporator 1 for heat exchangers of Examples 9 to 13, the number of filaments, and the width of the non- uneven surface 14. In addition, the said depth is an average value which measured the depth of ten places along the distribution direction of a refrigerant | coolant in the center part of the width direction of the uneven | corrugated surface 13. FIG.

表４から、実施例９〜１３の熱交換器用蒸発器１では、凹凸面１３の総面積が非凹凸面１４の総面積よりも広くなっていることがわかる。

From Table 4, it can be seen that in the heat exchanger evaporator 1 of Examples 9 to 13, the total area of the uneven surface 13 is larger than the total area of the non-uneven surface 14.

  Next, in exactly the same way as in Examples 1 to 6, the cooling capacity of the exchanger evaporator 1 in Examples 9 to 13 was evaluated. The results are shown in Table 6.

Table 6 also shows the specific surface area of the uneven surface 13 measured by the BET method and the surface roughness of the uneven surface 13 measured by a contact-type surface roughness meter.
[Comparative Examples 6-9]
Heat exchanger evaporator 1 of Comparative Example 6-9, by adjusting the conditions of the etching, a specific surface area of less than 15cm ² of 1 cm ² per uneven surface 13, or, the surface roughness Ry is more 30μm Except as described above, the configuration is exactly the same as in Examples 9-12. Table 5 shows the width and depth of the uneven surface 13 in the evaporator 1 for heat exchangers of Comparative Examples 6 to 9, the number of filaments, and the width of the non- uneven surface 14. In addition, the said depth is an average value which measured the depth of ten places along the distribution direction of a refrigerant | coolant in the center part of the width direction of the uneven | corrugated surface 13. FIG.

表５から、比較例６〜９の熱交換器用蒸発器１では、凹凸面１３の総面積が非凹凸面１４の総面積よりも広くなっていることがわかる。

From Table 5, in the evaporator 1 for heat exchangers of Comparative Examples 6 to 9, it can be seen that the total area of the uneven surface 13 is larger than the total area of the non-uneven surface 14.

  Next, the cooling capacity of the exchanger evaporator 1 was evaluated in exactly the same way as in Examples 1-6. The results are shown in Table 6.

  Table 6 also shows the specific surface area of the uneven surface 13 measured by the BET method and the surface roughness of the uneven surface 13 measured by a contact-type surface roughness meter.

表６から、１ｃｍ²当たりの比表面積が１５ｃｍ²以上、かつ、面粗度Ｒyが３０μｍ以上となっている凹凸面１３を備える熱交換器用蒸発器１（実施例９〜１３）は、凹凸面１３の１ｃｍ²当たりの比表面積が１５ｃｍ²以上であるが面粗度Ｒyが３０μｍ未満の場合（比較例６，７）、面粗度Ｒyが３０μｍ以上であるが１ｃｍ²当たりの比表面積が１５ｃｍ²未満である場合（比較例８，９）と比較して、純銅チップ５の各部の温度が低く、優れた冷却能力を備えていることが明らかである。

From Table 6, the heat exchanger evaporator 1 (Examples 9 to 13) including the uneven surface 13 having a specific surface area per 1 cm ² of 15 cm ² or more and a surface roughness Ry of 30 μm or more is an uneven surface. 13 has a specific surface area per 1 cm ² of 15 cm ² or more but the surface roughness Ry is less than 30 μm (Comparative Examples 6 and 7), the surface roughness Ry is 30 μm or more but the specific surface area per 1 cm ² is 15 cm. ^As compared with the case of less than ² (Comparative Examples 8 and 9), it is clear that the temperature of each part of the pure copper chip 5 is low and has an excellent cooling capacity.

Further, from Table 6, the uneven surface 13 having a specific surface area per 1 cm ² of 15 cm ² or more and a surface roughness Ry of 30 μm or more is formed in a line along the refrigerant flow direction. Heat exchanger evaporator 1 (Examples 9 to 13) in which a non-concave surface 14 forming a line between 13 and 13 is formed and the total area of the uneven surface 13 is larger than the total area of the non-concave surface 14 ) Is clearly provided with a cooling capacity better than that in the case where the total area of the uneven surface 13 is smaller than the total area of the non-uneven surface 14 (Examples 7 and 8).

Explanatory sectional drawing which shows the structure of the evaporator for heat exchangers of this invention. The graph explaining the definition of surface roughness Ry. The top view of one structural example of the evaporator for heat exchangers shown in FIG. The top view of the other structural example of the evaporator for heat exchangers shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Heat exchanger evaporator, 2a ... Heat-transfer surface, 3 ... Refrigerant flow path, 13 ... Uneven surface, 14 ... Non uneven surface.

Claims (4)

Heat that comprises a refrigerant flow path through which the refrigerant flows and a heat transfer surface in contact with the refrigerant in the refrigerant flow path, and causes a phase change of at least a part of the refrigerant in contact with the heat transfer surface from liquid to gas. In the evaporator for the exchanger,
The heat transfer surface has a specific surface area per cm ² of 15 cm ² or more, and a maximum relative to the average value when the average value of the irregularities measured between any two points on the heat transfer surface is used as a reference. An evaporator for a heat exchanger, comprising an uneven surface having a surface roughness Ry of 30 μm or more indicated by a sum Rp + Rv of a height Rp and a maximum depth Rv.   The heat transfer surface includes the uneven surface formed in a line along the flow direction of the refrigerant, and a non- uneven surface formed in a line between the uneven surface. The evaporator for a heat exchanger according to claim 1.   The evaporator for a heat exchanger according to claim 2, wherein a total area of the uneven surface is larger than a total area of the non-uneven surface.   The said heat-transfer surface is formed of the aluminum-type member, The said uneven | corrugated surface is formed by etching this aluminum-type member, The Claim 1 characterized by the above-mentioned. Evaporator for heat exchanger.

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