The present invention relates to a structure of a heat-transfer pipe with internal grooves having grooves in an inner surface of a pipe body.

A heat-transfer pipe in a heat exchanger such as an evaporator, a condenser or the like for an air conditioner is conventionally provided with spiral grooves in an inner surface of the pipe from a viewpoint of improvement in its heat transfer efficiency as shown in Japanese Patent Laid-Open Publication No. Hei 9-42881 so that a heat-transfer area is enlarged and an agitation effect is improved by allowing a refrigerant flowing in the pipe to annularly flow.

In the case of a heat-transfer pipe in this constitution, however, liquid film portions are uniformly distributed generally in the pipe when a condensation action proceeds to some extent and the thickness gradually increases. Consequently, heat resistance and diffusion resistance increase and thereby a heat-transfer performance is deteriorated.

In order to address this problem, there is a proposal that the inner surface of the pipe is divided into a plurality of areas in the circumferential direction, each having a plurality of rows of grooves arranged in V-shaped patterns, for example, which are symmetric with respect to the direction of a pipe axis and have equal widths in the circumferential direction, for example, as shown in Japanese Patent Laid-Open Publication No. Hei 9-42880.

In the case of this constitution, the distribution of the refrigerant flowing in the pipe in the pipe circumferential direction can be made ununiform because of flow merging and dividing actions by the plurality of the grooves arranged in V-shaped patterns provided in the inner surface of the pipe which are symmetric with respect to the pipe axis direction and have equal widths in the circumferential direction as compared with the aforementioned heat-transfer pipe having the spiral grooves. Since high heat transfer efficiency is achieved in areas where the liquid refrigerant becomes a thin film as a result, the heat transfer efficiency at the time of condensation is improved.

However, in the case of the above-described heat-transfer pipe having grooves arranged in V-shaped patterns in the inner surface of the pipe which are symmetric with respect to the pipe axis direction and have equal widths in the circumferential direction,

An object of the present invention is to provide a heat-transfer pipe with internal grooves having a heat transfer performance improved as much as possible by reducing a pressure loss and appropriately controlling refrigerant flows in the pipe to be even when a refrigerant flow rate is low, and a manufacturing method thereof as well as a manufacturing device, by which the above-described problems can be solved.

In order to achieve the above object, each aspect of the present invention has the following means for solving the problems.

In a heat-transfer pipe with internal grooves according to the first aspect of the present invention, a plurality of rows of grooves arranged in V-shaped patterns 3 symmetric with respect to a pipe axis direction are provided on an inner surface 2 of a pipe body 1a; and widths of the plurality of rows of the grooves 3 arranged in the V-shaped patterns are made unequal in a circumferential direction.

Thus, when the plurality of rows of the grooves 3 arranged in V-shaped patterns are provided side by side with unequal widths in the circumferential direction, a component of force in the swirling direction are generated in a refrigerant liquid so that the refrigerant liquid flows in an ununiform manner in the pipe axis direction while repeatedly merging and dividing at edges of respective grooves 3 arranged in the V-shaped patterns. Consequently, an annular flow close to the one obtained by combination of spiral grooves can be obtained. Further, an agitation effect is achieved and thereby a heat transfer performance is improved.

In the heat-transfer pipe with internal grooves according to the second aspect of the present invention, secondary grooves 6 having a prescribed depth are formed from a top 5a side towards a base 5b side at least in part of projected portions 5 formed between respective grooves 3 of the plurality of rows of the grooves 3 arranged in the V-shaped patterns.

Thus, when the secondary grooves 6 having a prescribed depth are formed from the top part 5a side towards the bottom part 5b side at least in part of the projected portions 5 formed between the respective grooves 3 of the plurality of rows of the grooves 3 arranged in V-shaped patterns, the flow resistance of the refrigerant flowing in the pipe is further reduced by the secondary grooves 6 and thereby a heat transfer performance is effectively improved even when a refrigerant flow rate is low.

In the heat-transfer pipe with internal grooves according to the third aspect of the present invention, the secondary grooves 6 are notched grooves in a spiral direction.

In this case, the flow resistance of the refrigerant flowing in the pipe is effectively reduced by the secondary grooves 6 composed of the notched grooves in the spiral direction. Further, a swirling force is increased in the spiral direction and thereby the heat transfer performance is improved.

In the heat-transfer pipe with internal grooves according to the fourth aspect of the present invention, secondary grooves 7 having a prescribed depth are formed in an outer surface of at least part of projected portions 5 formed between respective grooves 3 of the rows of grooves 3 arranged in the V-shaped patterns.

Thus, when the secondary grooves 7 having a prescribed depth are formed in outer surfaces at least in part of the projected portions 5 formed between the respective grooves 3 of the rows of grooves arranged in the V-shaped patterns, a pressure loss is reduced since the flow resistance of the refrigerant flowing in the pipe is reduced by the secondary grooves 7 and thereby a heat transfer performance is effectively improved even when a refrigerant flow rate is low.

In the heat-transfer pipe with internal grooves according to the fifth aspect of the present invention, the secondary grooves 7 are fine grooves extending from one side surface of the projected portions 5 to the other side surface thereof.

The flow resistance of the refrigerant flowing in the pipe is effectively reduced by the secondary grooves 7 composed of fine grooves extending from one side surface to the other side surface of the projected portions 5 in this case, and therefore the heat transfer performance is improved. Also, even when the pipe is expanded, both sides of the fine grooves are not crushed and thereby the heat-transfer performance is not deteriorated.

In a method for manufacturing a heat-transfer pipe with internal grooves according to the sixth aspect of the present invention, a first marking roll 11 for marking a plurality of rows of grooves 3 arranged in V-shaped patterns in a flat plate-like heat-transfer pipe material 13, a second marking roll 12 for marking secondary grooves 7 at least in part of projected portions 5 formed between respective grooves 3 of the plurality of rows of the grooves 3 arranged in the V-shaped patterns and a roll forming device 17 for forming the flat plate-like heat-transfer pipe material 13 into a cylindrical pipe are used to continuously mark the plurality of rows of the grooves 3 arranged in the V-shaped patterns and the secondary grooves 7 in the flat plate-like heat-transfer pipe material 13 successively by the first and second marking rolls 11, 12 and then form a cylindrical pipe by roll forming by the roll forming device 17.

In this method of manufacturing a heat-transfer pipe with internal grooves, the heat-transfer pipe with internal grooves having the constitutions of the first, fourth and fifth aspects can be easily manufactured only by combining the above-described first and second marking rolls 11, 12 in the direction of the movement of the flat plate-like heat-transfer pipe material 13 to perform continuous markings successively in two stages.

In a device for manufacturing a heat-transfer pipe with internal grooves according to the seventh aspect of the present invention, a first marking roll 11 for marking a plurality of rows of grooves 3 arranged in V-shaped patterns in a flat plate-like heat-transfer pipe material 13, a second marking roll 12 for marking secondary grooves 7 at least in part of projected portions 5 formed between respective grooves 3 of the plurality of rows of the grooves 3 arranged in V-shaped patterns and a roll forming device 17 for forming the flat plate-like heat-transfer pipe material 13 into a cylindrical pipe are provided successively side by side in a direction of movement of the flat plate-like heat-transfer pipe material 13 to continuously mark the grooves 3 arranged in the V-shaped patterns and the secondary grooves 7 successively by the first and second marking rolls 11, 12 and then form a cylindrical pipe by roll forming by the roll forming device 17.

By this device for manufacturing the heat-transfer pipe with internal grooves, the heat-transfer pipe with internal grooves having the constitutions of the first, fourth and fifth aspects can be easily manufactured only by combining the above-described first and second marking rolls 11, 12 in the direction of the movement of the flat plate-like heat-transfer pipe material 13 to perform markings successively in two stages.

As a result of the above, according to the heat-transfer pipe with internal grooves and the manufacturing method thereof and the manufacturing device according to each aspect of the present invention, a pressure loss, heat resistance in the heat-transfer pipe and diffusion resistance are reduced even in the case of being constituted as a condenser or an evaporator or even in the case where a refrigerant flow rate is low when the pipe is constituted as an evaporator. Consequently, a heat exchanger with sufficiently high heat transfer performance can be provided.

Figs. 1 to 3 show a structure of a heat-transfer pipe with internal grooves according to a first embodiment of the present invention.

First, as shown in Figs. 1 to 3 for example, in the heat-transfer pipe 1 with internal grooves according to this embodiment, first to fifth groups A - E of a plurality of rows of grooves is provided on an inner surface 2 of a pipe body 1a having an electric welded pipe structure. Those groups of grooves are comprised of grooves 3 which are arranged to be symmetric, with respect to a pipe axis direction and to form relatively sharp V-shape patterns, and which are arranged with width of the grooves unequal to each other in the circumferential direction and with a lead angle  of the grooves different from each other, so as to promote a turbulent flow of a refrigerant liquid flowing in the pipe body 1a and to promote the refrigerant liquid to become a thin film because coarse and minute refrigerant liquid portions are formed by dividing and merging the refrigerant liquid flow.

In Fig. 3, reference numeral 5 denotes a projected portion formed between the respective grooves 3 arranged in V-shaped patterns. Reference numerals 5a and 5b denote a top and a base of the projected portion, respectively.

Thus, since the first to fifth groups A - E composed of rows of grooves, which are arranged in V-shaped patterns and have a lead angle  different in next groups, are provided side by side with unequal widths in the circumferential direction, the refrigerant liquid flows ununiformly in the circumferential direction to swirl while repeatedly dividing and merging at edge portions of V-shape patterns of the respective grooves 3. Consequently, the grooves of the present invention can obtain an annular flow close to the one conventionally obtained by combination of spiral grooves even though the grooves arranged in V-shaped patterns are used. Thus, an effective agitation effect is achieved and thereby a heat transfer performance is improved.

Respective grooves 3 in the first to fifth groups A - E are formed with a prescribed lead angle , a prescribed depth H and a prescribed number of grooves N so that the flow resistance of each groove portion is made as small as possible to reduce the pressure loss. Therefore, even when the heat-transfer pipe of the present invention is used for an evaporator at a low refrigerant flow rate, the pressure loss is reduced and thereby the heat transfer performance is improved.

According to the results of experiments conducted by the present inventors, the flow resistance was the smallest and the pressure loss was effectively reduced when the aforementioned lead angle , groove depth H, and number of grooves N are in the range of 5 - 15°, 0.2 - 0.3 mm and 45 - 55, respectively, in the case of a heat-transfer pipe having an outer dimension of  = 7 mm.

As described above, according to the constitution of the heat-transfer pipe with internal grooves of this embodiment, widths of groups A - E composed of rows of grooves 3, which are arranged in V-shaped patterns and have a lead angle  different from each other, are set unequal in the circumferential direction rather than equal. Therefore, the refrigerant in the pipe has swirling flow as in the case of the conventional pipe with spiral grooves. Consequently, the heat transfer promotion effect is not deteriorated even when a refrigerant flow rate is low because the refrigerant is effectively supplied in the circumferential direction of the pipe.

The lead angle , the groove depth H and the groove number N of the grooves 3 formed in the V-shaped patterns, the first to fifth groups A - E of which are arranged in the inner surface of the pile, are set to the values by which the smallest flow resistance is obtained corresponding to the aforementioned experiment results. Therefore, since the flow resistance can be made as small as possible to reduce the pressure loss as a result, a heat-transfer pipe for a heat exchanger having a sufficiently high performance can be obtained.

Figs. 4 to 6 show a structure of a heat-transfer pipe with internal grooves according to a second embodiment of the present invention.

First, in the heat-transfer pipe 1 with internal grooves according to this embodiment, first to fifth groups A - E of a plurality of rows of grooves is provided on an inner surface 2 of a pipe body 1a having the same electric welded pipe structure as described above. Those groups of grooves are comprised of grooves 3 which are arranged to be symmetric with respect to a pipe axis direction and to form relatively sharp V-shape patterns, and which are arranged with width of the grooves unequal to each other in the circumferential direction and with a lead angle  of the grooves different from each other, so as to promote a turbulent flow of a refrigerant liquid flowing in the pipe body 1a and to promote the refrigerant liquid to become a thin film because coarse and minute refrigerant liquid portions are formed by dividing and merging the refrigerant liquid flow.

In Figs. 5 and 6, reference numeral 5 denotes a projected portion formed between the respective grooves 3 arranged in V-shaped patterns. Reference numerals 5a and 5b denote a top and a base of the projected portion 5, respectively. In this embodiment, secondary grooves 6 are provided and the secondary grooves 6 are composed of notched grooves (chipped grooves) in the spiral direction with a prescribed depth d from the top 5a towards the base 5b. Consequently, the flow resistance of the refrigerant is reduced and the refrigerant is further urged in the swirling direction.

Thus, since the first to fifth groups A - E composed of rows of grooves, which are arranged in V-shaped patterns and have a lead angle  different in next groups, are provided side by side with unequal widths in the circumferential direction, the refrigerant liquid flows ununiformly in the circumferential direction to swirl while repeatedly dividing and merging at edge portions of V-shape patterns of the respective grooves 3. Consequently, the grooves of the present invention can obtain an annular flow close to the one conventionally obtained by combination of spiral grooves even though the grooves arranged in V-shaped patterns are used. Thus, an effective agitation effect is achieved and thereby a heat transfer performance is improved.

Respective grooves 3 in the first to fifth groups A - E are formed with the secondary grooves 6 composed of notched grooves (chipped grooves) in the spiral direction as described above as well as a prescribed lead angle , a prescribed depth H and a prescribed number of grooves as in the first embodiment, so that the flow resistance of each groove portion is made as small as possible to reduce the pressure loss. Therefore, even when the heat-transfer pipe of the present invention is used for an evaporator at a low refrigerant flow rate, the pressure loss is reduced and thereby the heat transfer performance is improved.

According to the results of experiments conducted by the present inventors as described above, the flow resistance was the smallest and the pressure loss was effectively reduced when the aforementioned lead angle , groove depth H, and number of grooves N are in the range of 5 - 15°, 0.2 - 0.3 mm and 45 - 55, respectively, in the case of a heat-transfer pipe having an outer dimension of  = 7 mm.

As described above, according to the constitution of the heat-transfer pipe with internal grooves of this embodiment, widths of groups A - E composed of rows of grooves 3, which are arranged in V-shaped patterns and have a lead angle  different from each other, are set unequal in the circumferential direction. Therefore, the refrigerant in the pipe has swirling flow as in the case of the conventional pipe with spiral grooves. Consequently, the heat transfer promotion effect is not deteriorated even when a refrigerant flow rate is low because the refrigerant is effectively supplied in the circumferential direction of the pipe.

The lead angle , the groove depth H and the groove number N of the grooves 3 formed in the V-shaped patterns, the first to fifth groups A - E of which are arranged in the inner surface of the pile, are set to the values by which the smallest flow resistance is obtained. In addition, the secondary grooves 6 are formed in the projected portions 5 provided between the respective grooves 3 as main grooves in V-shaped patterns and the secondary grooves 6 are notched grooves from the top 5a towards the base 5b of the projected portions 5 and are directed in the spiral direction. Therefore, since the flow resistance can be made as small as possible to reduce the pressure loss and swirling force in the spiral direction can be further increased, a heat-transfer pipe for a heat exchanger having a still higher performance can be obtained.

Figs. 7 to 9 show a structure of a heat-transfer pipe with internal grooves according to a third embodiment of the present invention and a constitution of a manufacturing device employing a method for manufacturing the heat-transfer pipe, respectively.

First, in the heat-transfer pipe 1 with internal grooves according to this embodiment, first to fifth groups A - E of a plurality of rows of grooves is provided on an inner surface 2 of a pipe body 1a having the same electric welded pipe structure as described above. Those groups of grooves are comprised of grooves 3 which are arranged to be symmetric with respect to a pipe axis direction and to form relatively sharp V-shape patterns, and which are arranged with width of the grooves unequal to each other in the circumferential direction and with a lead angle  of the grooves different from each other, so as to promote a turbulent flow of a refrigerant liquid flowing in the pipe body 1a and to promote the refrigerant liquid to become a thin film because coarse and minute refrigerant liquid portions are formed by dividing and merging the refrigerant liquid flow.

In Figs. 7 and 8, reference numeral 5 denotes a projected portion formed between the respective grooves 3 arranged in V-shaped patterns. Reference numerals 5a and 5b denote a top and a base of the projected portion 5, respectively. In this embodiment, secondary grooves 7 composed of fine grooves having a prescribed depth are formed from one side of an outer surface of the projected portion 5 to the other side thereof to direct toward, for example, the spiral direction. Consequently, the flow resistance of the refrigerant is reduced and the refrigerant is further urged in the swirling direction.

Thus, since the first to fifth groups A - E composed of rows of grooves, which are arranged in V-shaped patterns and have a lead angle  different in next groups, are provided side by side with unequal widths in the circumferential direction, the refrigerant liquid flows ununiformly in the circumferential direction to swirl while repeatedly dividing and merging at edge portions of V-shape patterns of the respective grooves 3. Consequently, the grooves of the present invention can obtain an annular flow close to the one conventionally obtained by combination of spiral grooves even though the grooves arranged in V-shaped patterns are used. Thus, an effective agitation effect is achieved and thereby a heat transfer performance is improved.

Respective grooves 3 in the first to fifth groups A - E are formed with the secondary fine grooves 7 formed from one side of an outer surface of the projected portion 5 to the other side thereof in a prescribed depth to direct toward the spiral direction as well as with a prescribed lead angle , a prescribed depth H and a prescribed number of grooves as in the first embodiment. Consequently, the flow resistance of each groove portion is made as small as possible to reduce the pressure loss. Therefore, even when the heat-transfer pipe of the present invention is used for an evaporator at a low refrigerant flow rate, the pressure loss is reduced and thereby the heat transfer performance is improved. Also, even when the pipe is expanded, the fine grooves on the side portions are not crushed and thereby the heat transfer performance is not deteriorated.

According to the results of experiments conducted by the present inventors as described above, the flow resistance was the smallest and the pressure loss was effectively reduced when the aforementioned lead angle , groove depth H, and number of grooves N are in the range of 5 - 15°, 0.2 - 0.3 mm and 45 - 55, respectively, in the case of a heat-transfer pipe having an outer dimension of  = 7 mm.

As described above, according to the constitution of the heat-transfer pipe with internal grooves of this embodiment, widths of groups A - E composed of rows of grooves 3, which are arranged in V-shaped patterns and have a lead angle  different from each other, are set unequal. Therefore, the refrigerant in the pipe has swirling flow as in the case of the conventional pipe with spiral grooves. Consequently, the heat transfer promotion effect is not deteriorated even when a refrigerant flow rate is low because the refrigerant is effectively supplied in the circumferential direction of the pipe.

The lead angle , the groove depth H and the groove number N of the grooves 3 formed in the V-shaped patterns, the first to fifth groups A - E of which are arranged in the inner surface of the pile, are set to the values by which the smallest flow resistance is obtained. In addition, the secondary grooves 7 composed of fine grooves are formed from one side of an outer surface of the projected portion 5 to the other side thereof to direct toward, for example, the spiral direction. Therefore, since the flow resistance can be made as small as possible to reduce the pressure loss and swirling force in the spiral direction can be further increased, a heat-transfer pipe for a heat exchanger having a still higher performance can be obtained. Also, even when the pipe is expanded, the fine grooves on the side portions are not crushed and thereby the heat transfer performance is not deteriorated.

The heat-transfer pipe with internal grooves having the groups A - E of rows of the grooves arranged in V-shaped patterns and secondary grooves 7 described above are easily manufactured by the following method by using, for example, a manufacturing device shown in Fig. 9.

In Fig. 9, reference numeral 11 denotes a first marking roll which has a marking processing surface 11a corresponding to the first to fifth groups A - E of rows of grooves arranged as main grooves in V-shaped patterns. Reference numeral 12 denotes a second marking roll which has a marking processing surface 12a for marking the fine grooves 7 provided to extend, for example, in the spiral direction from one side to the other side of an outer surface of the projected portion 5 formed between the grooves 3 arranged in V-shaped patterns in the first to fifth groups A - E. Reference numeral 13 denotes a flat plate-like heat-transfer pipe material. Reference numeral 16 denotes a heating device for heating and softening the heat-transfer pipe material at the time of roll forming. Reference numeral 14 denotes a first pressure roller for sandwiching and pressing the flat plate-like heat-transfer pipe material 13 with the aforementioned first marking roll 11. Reference numeral 15 denotes a second pressure roller for sandwiching and pressing the flat plate-like heat-transfer pipe material 13 with the aforementioned second marking roll 12. Reference numeral 17 denotes a roll forming device having a roll forming hole 17a for roll-forming into a cylindrical shape the heat-transfer pipe material 13 which has the first to fifth groups A - E of rows of grooves arranged in V-shaped patterns and the secondary grooves 7 formed thereon via the first and second marking rollers 11, 12 and is heated and softened by the heating device 16. The first marking roll 11 and the first pressure roller 14, the second marking roll 12 and the second pressure roller 15, the heating device 16 and the roll forming device 17 are successively provided side by side at predetermined intervals in the movement direction (see the arrow) of the heat-transfer pipe material 13.

Therefore, in the device for manufacturing the heat-transfer pipe with internal grooves, the first marking roll 11 and the first pressure roller 14 are used for marking the first to fifth groups A - E of rows of grooves arranged in V-shaped patterns, the second marking roll 12 and the second pressure roller 15 are used for marking the secondary grooves 7 in part of the projected portions formed between the respective grooves 3 of the first to fifth groups A - E of rows of grooves arranged in V-shaped patterns, and the heating device 16 and the roll forming device 17 are used for forming the flat plate-like heat-transfer pipe material 13 into a cylindrical pipe. The first and second marking rolls 11, 12 are rotatably operated so that the respective grooves 3 of the first to fifth groups A - E and the secondary grooves 7 are successively marked in two stages on the flat plate-like heat-transfer pipe material 13, and then the heat-transfer pipe material 13 can be heated and softened by the heating device 16 and then roll-formed by the roll forming device 17 to form a cylindrical pipe.

That is, in the method and device for manufacturing the heat-transfer pipe with internal grooves, the heat-transfer pipe with internal grooves having a constitution shown in Figs. 7 and 8 can be easily manufactured only by two stage successive marking of the grooves with the above-described first and second marking rolls 11, 12 combined in the direction of the movement of the flat plate-like heat-transfer pipe material 13. Other Embodiments

Although a heat-transfer pipe of a electric welded pipe type is described as an example in the above embodiments, it is needless to say that the internal groove structures of the above embodiments can be also applied to a seam welded type of heat-transfer pipe.

As described above, the heat-transfer pipe with internal grooves and the manufacturing method thereof and the manufacturing device according to the present invention are useful for a heat-transfer pipe of a heat exchanger and particularly suitable for a heat-transfer pipe used for an evaporator or a condenser in an air-conditioner.