JP2005090798A - Heat transfer pipe for condenser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat transfer pipe for a condenser, capable of reducing the pressure loss of the fluid circulated inside, preventing the corrosion of an inner face, having high heat transferring performance, and reducing a mass, with respect to the heat transfer pipe for the condenser using water as a refrigerant. <P>SOLUTION: A plurality of quadrangular pyramid-shaped projections 3 are spirally formed on an outer face of a pipe main body 2. On a cross-section in parallel with a pipe axis, a minimum width of groove parts 4a is 0.30-0.80 mm, and an arrangement pitch of the projections 3 is 0.70-1.42 mm. On a cross-section orthogonal to the pipe axis, a width of a bottom part of the groove parts 4b is 0.12-0.38 mm, and an arrangement pitch of the projections 3 is 0.45-0.65 mm. Further a height h of the projections 3 is 0.18-0.50 mm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a heat transfer tube for a condenser incorporated in a shell-and-tube or shell-and-coil condenser, and is particularly suitable for a condenser that uses a refrigerant having high viscosity and surface tension such as water (H ₂ O). It relates to a heat exchanger tube for a condenser.

  Cooling liquid such as water or brine is flowed into the heat transfer tube and the refrigerant vapor is brought into contact with the outer surface of the heat transfer tube on the condenser of the absorption refrigerator and the condenser of the boiler, etc. A heat exchanger that condenses the refrigerant vapor into a refrigerant liquid is used. In such a heat exchanger, a shell-and-tube or shell-and-coil condenser is used. The brine is a coolant generally used in a heat exchanger, and is, for example, a calcium chloride or ethylene glycol aqueous solution.

  FIG. 7 is a cross-sectional view showing an example of a shell-and-tube condenser. As shown in FIG. 7, the shell-and-tube condenser 51 is provided with a cylindrical body 52, and tube plates 53 are provided at both ends of the body 52, respectively. A sealed space is formed by 52 and the tube plate 53. The trunk | drum 52 is arrange | positioned so that an axial direction may turn into a horizontal direction. A refrigerant vapor inlet 54 is provided at the upper part of the body part 52, and a refrigerant liquid outlet 55 is provided at the lower part.

  Further, a lid portion 56 is connected to one end of the body portion 52, and a lid portion 57 is connected to the other end of the body portion 52. A plurality of heat transfer tubes 58 are arranged in the body portion 52. Both ends of the heat transfer tubes 58 are supported by the tube plates 53, and the heat transfer tubes 58 are arranged in parallel to each other so that the axial direction thereof is parallel to the axial direction of the trunk portion 52, that is, the horizontal direction. One end of each heat transfer tube 58 communicates with the lid portion 56, and the other end communicates with the lid portion 57.

  The lid portion 56 is divided into three chambers 60 to 62 by two partition plates 59, and the chambers 60 to 62 communicate with different heat transfer tubes 58. The chamber 60 is provided with a coolant inlet 63 communicating with the outside, and the chamber 62 is provided with a coolant outlet 64 communicating with the outside. On the other hand, the lid portion 57 is partitioned into chambers 66 and 67 by a single partition plate 65, and the chambers 66 and 67 communicate with different heat transfer tubes 58.

  In the shell-and-tube condenser 51 configured in this way, a cooling liquid (not shown), for example, water or brine is supplied from the cooling liquid inlet 63 to the chamber 60 in the lid portion 56, and this cooling liquid is It flows through the heat transfer tube 58 communicated with the chamber 60 and is introduced into the chamber 66 of the lid portion 57. Then, the coolant flows through the heat transfer tube 58 communicated with the chamber 66 and the chamber 61 and flows into the chamber 61, and then flows through the heat transfer tube 58 communicated with the chamber 61 and the chamber 67. The refrigerant flows into the chamber 67, circulates through the heat transfer pipe 58 communicated with the chamber 67 and the chamber 62, reaches the chamber 62, and is discharged from the cooling liquid outlet 64 to the outside of the condenser 51. At this time, a refrigerant vapor (not shown) is introduced into the barrel 52 from the refrigerant vapor inlet 54, and the refrigerant vapor condenses on the surface of the heat transfer pipe 58 and becomes a refrigerant liquid at the bottom of the barrel 52. The liquid is dropped and discharged out of the body 52 from the refrigerant liquid outlet 55. In this way, heat exchange occurs between the refrigerant and the coolant via the heat transfer tube 58, and the heat of the refrigerant vapor is transmitted to the coolant.

  FIG. 8 is a sectional view showing an example of a shell-and-coil condenser. As shown in FIG. 8, the shell and coil type condenser 71 is provided with a chamber 72, a refrigerant vapor inlet 73 is provided at the upper part of the chamber 72, and a refrigerant liquid outlet 74 is provided at the lower part. ing. A cooling liquid inlet 75 and a cooling liquid outlet 76 are provided on the side surface of the chamber 72. In addition, a heat transfer tube 77 wound in a coil shape is provided inside the chamber 72, and one end of the heat transfer tube 77 is communicated to the outside via a coolant inlet 75, and the other end is connected to the coolant. It communicates with the outside through an outlet 76.

  In the shell-and-coil condenser 71 configured as described above, a cooling liquid (not shown), for example, water or brine is supplied from the cooling liquid inlet 75 into the heat transfer pipe 77 and flows through the heat transfer pipe 77. Thereafter, the liquid is discharged to the outside through the coolant outlet 76. At this time, refrigerant vapor (not shown) is introduced into the chamber 72 from the refrigerant vapor inlet 73, and this refrigerant vapor condenses on the surface of the heat transfer tube 77, becomes a refrigerant liquid, and drops on the bottom of the chamber 72. The liquid is discharged from the liquid outlet 74 to the outside of the chamber 72. In this way, heat exchange occurs between the refrigerant and the coolant via the heat transfer tube 77, and the heat of the refrigerant vapor is transmitted to the coolant.

  Conventionally, smooth tubes have been used for the heat transfer tubes of these condensers, that is, the heat transfer tube 58 shown in FIG. 7 and the heat transfer tube 77 shown in FIG. However, recently, in order to improve the heat exchange performance of the condenser, a corrugated tube in which irregularities are spirally formed on the inner and outer surfaces of the tube has been used. FIG. 9 is a side sectional view showing the corrugated tube. As shown in FIG. 9, in the corrugated tube 81, a groove 82 is formed in a spiral shape on the outer surface of the tube. In addition to corrugated tubes, many heat transfer tubes with fins or protrusions formed on the outer surface have been proposed as heat transfer tubes for condensers (see, for example, Patent Documents 1 and 2).

Japanese Patent No. 3415013 JP-A-11-257888

  However, the conventional techniques described above have the following problems. When a corrugated tube is used as the heat transfer tube, the heat transfer performance inside the tube is improved, but there is a problem that the pressure loss of the coolant flowing through the tube increases. Further, since the corrugated tube has a large flow resistance of the fluid flowing in the pipe and a large frictional force is generated between the fluid and the inner surface of the pipe, corrosion tends to proceed. In particular, the convex portion 83 on the inner surface of the tube shown in FIG. 9 is susceptible to attack by a fluid, and corrosion tends to progress to easily generate holes. Further, in the corrugated tube, there is a problem that residues are likely to be accumulated in the concave portion 84 on the inner surface of the tube, and this residue becomes a film, and heat transfer resistance is increased, or the potential is changed and corrosion is likely to proceed. As a result, the life of the heat transfer tube is shortened. Furthermore, as shown in FIG. 9, a groove 82 is formed on the outer surface of the corrugated tube 81, but the condensate easily forms a film on the outer surface of the tube, and there is a limit to improving the heat transfer performance.

  Conventionally, Freon has been frequently used as a refrigerant applied to a condenser. That is, by introducing CFC vapor to the outside of the heat transfer tube, condensing it on the outer surface of the heat transfer tube, and using it as CFC liquid, heat exchange is performed with the coolant. However, due to recent Freon regulations, water is often used as a refrigerant instead of Freon. However, the conventional heat transfer tube is designed to have the highest heat transfer performance when using chlorofluorocarbon as a refrigerant, and is not optimized for the case where water is used as the refrigerant. Table 1 shows the values of viscosity and surface tension of water and Freon. Each value shown in Table 1 is a value at a pressure at which the condensation temperature is 45 ° C.

  As shown in Table 1, the viscosity of water is about 4 times that of Freon, and the surface tension is about 12 times that of Freon. For this reason, when water is used as a refrigerant and a conventional heat transfer tube designed for chlorofluorocarbon as a heat transfer tube is used, the condensed refrigerant liquid (water) stays between the fins, and the wetting and spreading of the refrigerant liquid and The detachability from the heat transfer tube is reduced. For this reason, the film | membrane of a refrigerant | coolant liquid becomes heat resistance and heat transfer performance becomes low. Further, in the heat transfer tube for chlorofluorocarbon, a relatively high fin is formed on the outer surface, but in order to form a high fin, it is necessary to use a tube having a large thickness as a raw tube. For this reason, there also exists a problem that the mass of a heat exchanger tube becomes large.

  The present invention has been made in view of such problems, and in a heat transfer tube for a condenser that uses water as a refrigerant, the pressure loss of the fluid flowing through the inside is small, the inner surface is hardly corroded, and the heat transfer performance is low. It aims at providing the heat exchanger tube for condensers which is high and can reduce mass.

  The condenser heat transfer tube according to the present invention includes a tube body and a plurality of protrusions arranged on the outer surface of the tube body and arranged in a direction orthogonal to or inclined with respect to the tube axis direction, and water or brine is contained in the tube. In the heat transfer tube for a condenser that causes heat exchange between the water vapor and the water or brine by bringing the water vapor into contact with the outer surface of the tube and condensing the water vapor, the arrangement pitch of the protrusions in the tube axis direction is 0.70 to 1.42 mm, the arrangement pitch of the projections in the tube circumferential direction is 0.45 to 0.65 mm, and the width of the groove formed between the projections in the tube axis direction is 0.30 to 0 .80 mm, the width of the groove in the pipe circumferential direction is 0.12 to 0.38 mm, and the height of the protrusion is 0.18 to 0.50 mm.

  In the present invention, by forming a plurality of protrusions on the outer surface of the tube and defining the shape and arrangement method of the protrusions as described above, high heat transfer performance can be obtained when water is used as the refrigerant. Further, by defining the height of the protrusion within the above range, the thickness of the tube can be reduced, and the mass of the tube can be reduced. Further, in the heat transfer tube of the present invention, unlike the corrugated tube, the inner surface of the tube is inevitably formed with irregularities, so the pressure loss of the fluid flowing in the tube is reduced and the corrosion of the inner surface of the tube proceeds. Can be suppressed. The shape of the protrusion is preferably a quadrangular pyramid or a quadrangular prism, and more preferably a quadrangular prism.

  According to the present invention, by forming a plurality of protrusions on the outer surface of the tube and appropriately defining the shape and arrangement method of the protrusions, excellent heat transfer performance is obtained in the heat transfer tube for a condenser that uses water as a refrigerant. be able to.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a partial perspective view showing a heat transfer tube according to the present embodiment, FIG. 2 is a tube axis parallel sectional view including a tube axis showing the heat transfer tube, and FIG. 3 is a tube axis orthogonal cross section showing the heat transfer tube. FIG. The heat transfer tube according to this embodiment is a heat transfer tube for a condenser that is incorporated in a shell and tube type or shell and coil type condenser.

  As shown in FIG. 1, in the heat transfer tube 1 according to the present embodiment, a tube main body 2 is provided, and a plurality of quadrangular pyramid-shaped protrusions arranged in a spiral form on the outer surface of the tube main body 2. 3 is formed. Between the adjacent projections 3 in the direction orthogonal to the arrangement direction of the projections 3 is a groove 4a, and between the adjacent projections 3 in the arrangement direction of the projections 3 is a groove 4b. Moreover, the inner surface of the pipe body 2 is smooth. The heat transfer tube 1 is made of, for example, copper or a copper alloy, and is, for example, a low phosphorus deoxidized copper tube defined by JIS H3300 C1201Ts-1 / 2H. The outer diameter of the heat transfer tube 1 is, for example, about 7 to 35 mm, for example, about 16 mm, and the bottom wall thickness is, for example, 0.3 to 0.7 mm, for example, 0.55 mm. On the outer surface of the tube body 2, an angle θ formed by the line 6 extending in the direction in which the protrusions 3 are arranged and the line 7 extending in the pipe circumferential direction is 0 ° or more and less than 90 °. When the angle θ is 0 °, the protrusions 3 are arranged in an annular shape. In addition, on the outer surface of the heat transfer tube 1, the protrusions 3 are arranged in a grid, for example. However, the protrusions 3 may be arranged in a staggered manner. That is, the positions of the protrusions 3 in the arrangement direction of the protrusions 3 may be shifted from each other between the rows of the protrusions 3 adjacent to each other.

As shown in FIG. 2, cross-section (hereinafter, referred to as the tube axis parallel cross section) including the tube axis at the minimum width of the groove 4a, i.e. the width _{W 1} of the bottom is 0.30 to 0.80 mm. The arrangement period (pitch) P ₁ of the protrusions 3 is 0.70 to 1.42 mm. Further, the height h of the protrusion 3 is 0.18 to 0.50 mm.

As shown in FIG. 3, in the cross section perpendicular to the tube axis, the width _{W 2} of the bottom of the groove 4b is 0.12 to 0.38 mm. The arrangement period _{P 2} of the projection 3 in the cross section perpendicular to the tube axis is 0.45 to 0.65 mm. The arrangement period P ₂ of the width W ₂ and the projections 3 of the bottom of the groove 4b are both linear length rather than the arc length.

  Next, the operation of the condenser heat transfer tube according to the present embodiment configured as described above will be described. FIG. 4 is a diagram illustrating an operation in which the condensed refrigerant liquid is detached from the heat transfer tube in the present embodiment. In FIG. 4, the projection 3 and the grooves 4a and 4b are not shown for convenience. Moreover, although the dry area | region and the area | region covered with the liquid film of the refrigerant | coolant liquid are formed in the surface of the heat exchanger tube 1, illustration of these area | regions is abbreviate | omitted in FIG. The condenser heat transfer tube 1 according to this embodiment is incorporated into a shell and tube type condenser as shown in FIG. 7 or a shell and coil type condenser as shown in FIG. 8, for example. And while circulating water or a brine in the heat exchanger tube arrange | positioned in a condenser, water vapor | steam is introduce | transduced as a refrigerant | coolant vapor | steam in a condenser, and heat exchange is performed between water or a brine and a refrigerant | coolant. At this time, this heat exchange is generally performed through the following process.

  (1) The heat transfer tube 1 is cooled by water or brine flowing through it. Thereby, the refrigerant vapor (water vapor) condenses on the surface of the projection 3 on the outer surface of the heat transfer tube 1 and becomes a refrigerant liquid (condensed water) 5 (condensation of water vapor). At this time, the refrigerant liquid 5 gives heat of condensation to the heat transfer tube 1, and this heat is transmitted to water or brine flowing in the tube.

  (2) After the refrigerant liquid (condensed water) 5 temporarily stays in the grooves 4a and 4b, the refrigerant liquid (condensed water) flows in the direction of the lower portion of the heat transfer tube 1 through the groove when the amount of stay in the grooves reaches a predetermined amount (condensed water). Move).

  (3) As shown in FIG. 4, when the amount of the refrigerant liquid (condensed water) 5 reaches a certain amount in the vicinity of the lower portion of the heat transfer tube 1, it is separated from the heat transfer tube 1 as water droplets due to gravity. At this time, not only the condensed water 5 staying at the lowermost part of the heat transfer tube 1 is separated, but is pulled by the condensed water at the lowermost part to be separated, and the condensed water near the lower part of the heat transfer tube 1 is also grooved 4a. And it moves to the lowermost part via 4b, and leaves | separates from the heat exchanger tube 1 (separation of condensed water).

  The above processes (1) to (3) occur continuously. If the condensed water (3) is released, the condensed water is pulled and the condensed water (2) moves. . When the condensed water moves, the liquid film on the outer surface of the tube is removed, and the condensation of water vapor (1) is promoted. And the faster this cycle, the better the heat transfer performance. In order for the water vapor condensation of (1) to occur smoothly, it is desirable that the condensed water condensed by the protrusions 3 is discharged smoothly, and the liquid film does not become too thick at the protrusions 3 and other portions. In addition, in order for the movement of the condensed water (2) to proceed smoothly, it is desirable that the condensed water does not stay in the grooves 4a and 4b between the protrusions 3 and flows quickly downward. Furthermore, in order for the removal of the condensed water (3) to proceed smoothly, it is desirable to regulate the thickness of the liquid film in the vicinity of the lower portion of the heat transfer tube 1 within an appropriate range.

  Gravity that moves the condensed water in the lower part of the heat transfer tube acts on the condensed water. On the other hand, the surface tension and viscosity of the condensed water act as resistance against movement due to gravity. In the above processes (1) to (3), a heat transfer tube capable of adjusting the balance between gravity, surface tension, and viscosity and rotating the cycle quickly is a heat transfer tube excellent in condensation heat transfer performance. The condenser heat transfer tube according to the present embodiment determines the pitch of the protrusions formed on the outer surface of the tube, the width of the groove between the protrusions, and the height of the protrusions so that the cycle proceeds quickly with respect to water vapor. It has achieved excellent condensation performance.

  Hereinafter, the reason for the numerical limitation in each constituent requirement of the present invention will be described.

Arrangement pitch of protrusions in the tube axis direction: 0.70 to 1.42 mm
If the arrangement pitch (P ₁ ) of the projections in the tube axis direction is less than 0.70 mm, the interval between the projections in the tube axis direction becomes small, so that condensed water having a large surface tension is held in the grooves 4 a between the projections 3. The surface of the protrusion 3 is covered with a liquid film. For this reason, it becomes difficult for water vapor to condense. That is, the process (1) is hindered. On the other hand, when the arrangement pitch (P ₁ ) is larger than 1.42 mm, the arrangement interval of the grooves 4a between the protrusions 3 is increased, so that the condensed water is pulled out at the lower part of the heat transfer tube and separated together. The amount of condensed water to be reduced is reduced, and the time required for the condensed water to be released is lengthened, and the condensate discharging performance is reduced. That is, the process (3) is hindered. Accordingly, the arrangement pitch of the protrusions in the tube axis direction needs to be 0.70 to 1.42 mm.

Arrangement pitch of protrusions in the pipe circumferential direction: 0.45 to 0.65 mm
If the arrangement pitch (P ₂ ) of the projections in the tube circumferential direction is less than 0.45 mm, the interval between the projections in the tube circumferential direction becomes small, so that condensed water having a large surface tension is held in the groove 4b between the projections 3. The surface of the protrusion 3 is covered with a liquid film. For this reason, it becomes difficult for water vapor to condense. That is, the process (1) is hindered. On the other hand, when the arrangement pitch (P ₂ ) is larger than 0.65 mm, the arrangement interval of the grooves 4b formed between the protrusions 3 is increased, so that the condensed water is pulled at the bottom of the heat transfer tube. The number of the groove portions 4b in the range where they are separated together is reduced, and the time required for the condensed water to be separated is lengthened, and the condensate drainage is lowered. That is, the process (3) is hindered. Accordingly, the arrangement pitch of the protrusions in the pipe circumferential direction needs to be 0.45 to 0.65 mm.

Groove width in the tube axis direction: 0.30 to 0.80 mm
When the width (W ₁ ) of the groove portion in the tube axis direction is less than 0.30 mm, the width in the tube axis direction of the groove portion 4a formed between the protrusions 3 is reduced, so that condensed water is held in the groove portion 4a. The surface of the protrusion 3 is covered with a liquid film. For this reason, it becomes difficult for water vapor to condense. That is, the process (1) is hindered. Further, since the condensed water is stably held in the groove 4a, the condensate discharge performance is lowered. That is, the process (3) is hindered. On the other hand, if the width (W ₁ ) of the groove is larger than 0.80 mm, the width of the groove 4a formed between the protrusions 3 increases, and the liquid film formed in the groove 4a overcomes the surface tension and viscosity. It takes a long time to reach a thickness that can flow, and the condensate discharge performance decreases. That is, the process (3) is hindered. In addition, the heat transfer performance is likely to decrease due to the thick liquid film in the groove 4a. That is, the process (1) is hindered. Therefore, the width of the groove in the tube axis direction needs to be 0.30 to 0.80 mm.

Groove width in the pipe circumferential direction: 0.12 to 0.38 mm
If the width (W ₂ ) of the groove in the tube circumferential direction is less than 0.12 mm, the width of the groove 4b becomes small, so that condensed water is held in the groove 4b and the surface of the protrusion 3 is covered with a liquid film. End up. For this reason, it becomes difficult for water vapor to condense. That is, the process (1) is hindered. Further, when the condensed water that has moved to the lower part of the heat transfer tube is separated, the resistance when the condensed water is pulled and moved in the tube axis direction is increased, and the amount of the condensed water that is separated is reduced. In addition, the time required until the condensed water is released becomes longer, and the condensate discharging performance is lowered. That is, the process (3) is hindered. On the other hand, if the width (W ₂ ) of the groove is larger than 0.38 mm, it takes time until the liquid film formed in the groove reaches a thickness that can overcome the surface tension and the viscosity and flow. Emissions will be reduced. That is, the process (3) is hindered. In addition, the heat transfer performance is lowered due to the thick liquid film in the groove. Therefore, the width of the groove portion in the pipe circumferential direction needs to be 0.12 to 0.38 mm.

Projection height: 0.18 to 0.50 mm
When the height (h) of the protrusion is less than 0.18 mm, the entire outer surface of the heat transfer tube is covered with condensed water, so that water vapor is difficult to condense. That is, the process (1) is hindered. On the other hand, if the height (h) of the protrusion is larger than 0.50 mm, the amount of condensed water held in the groove between the protrusions 3 increases, and the condensed water staying in the lower part of the heat transfer tube is condensed when it is released. When the water is pulled and moved in the direction of the tube axis, the resistance increases, and the amount of condensed water that separates decreases. In addition, the time required until the condensed water is released becomes longer, and the condensate discharging performance is lowered. That is, the process (3) is hindered. Furthermore, if the height (h) of the protrusion is larger than 0.50 mm, it is necessary to use a thick pipe with a thick wall when forming the heat transfer pipe. For this reason, the bottom wall thickness of the heat exchanger tube after processing becomes thick, the mass of the heat exchanger tube increases, and the heat transfer performance decreases. Therefore, the height of the protrusion needs to be 0.18 to 0.50 mm.

  Next, the manufacturing method of the heat exchanger tube 1 which concerns on this embodiment is demonstrated. First, a raw tube is prepared. This raw tube is, for example, a low phosphorus deoxidized copper tube having an outer diameter of 16 mm, a wall thickness of 0.7 mm, and a length of 1 to 10 m, which is defined by JIS H3300 C1201Ts-1 / 2H. Then, the raw tube is subjected to a rolling process to form spiral or annular fins at a constant pitch in the tube axis direction. At this time, the space between the fins becomes the groove 4a. The fins may be formed by a method other than the above-described rolling method, for example, a cutting method. Next, a gear disk is brought into rolling contact with the top of the fin, and the top of the fin is pushed in at a constant pitch in the pipe circumferential direction to form independent protrusions 3. At this time, the space between the protrusions 3 becomes the groove 4b. Next, low temperature annealing is performed to improve the fatigue strength of the pipe. The fin molding and the independent protrusion molding may be performed simultaneously or separately.

  As described above, in the present embodiment, a plurality of protrusions are provided on the outer surface of the condenser heat transfer tube. As a result, even when a refrigerant having high viscosity and surface tension such as water is used, when the refrigerant condensed on the outer surface of the heat transfer tube falls from the lowermost part of the heat transfer tube, the surrounding refrigerant is attracted and dropped together. As a result, the detachability of the condensed refrigerant is improved and the heat transfer performance is improved.

  In the present embodiment, the size and arrangement pitch of the protrusions are defined as described above. Specifically, the arrangement pitch of the protrusions is increased and the height of the protrusions is reduced as compared with a conventional heat transfer tube that uses chlorofluorocarbon as a refrigerant. Thereby, when water having higher viscosity and surface tension than Freon is used as the refrigerant, it is possible to improve the wetting and spreading property, the discharge property and the detachability of the refrigerant (water) on the outer surface of the tube. As a result, the cycle shown in the above (1) to (3) circulates smoothly without condensing the condensed water excessively in the groove, and good heat transfer performance can be realized.

  Further, in the present embodiment, the shape of the protrusion is a quadrangular pyramid, but the shape of the protrusion is preferably a quadrangular prism. By making the protrusion shape into a quadrangular prism shape, the condensed refrigerant liquid gathers at the protrusion tip along the side surface of the protrusion at the lowermost portion of the outer surface of the heat transfer tube, and easily falls from the protrusion tip. Thereby, the detachability of the refrigerant is improved.

  Furthermore, since irregularities are inevitably formed on the inner surface of the pipe, the pressure loss of water or brine circulating in the pipe can be reduced, and the progress of corrosion due to the attack of the fluid and accumulation of residues is suppressed. be able to. Furthermore, since the height of the protrusion can be made smaller than that of the heat transfer tube using chlorofluorocarbon as a refrigerant, it is easy to manufacture, and a raw tube with a small thickness can be used as the raw tube. Thereby, while being able to reduce the mass of a heat exchanger tube, heat transfer performance can be improved.

  In this embodiment, the heat transfer tube material is a low phosphorus deoxidized copper tube (JIS H3300 C1201Ts-1 / 2H), but the present invention is not limited to this, and the heat transfer tube material is C1020 of JIS H3300. Or the copper pipe described in C1220 may be sufficient, the pipe | tube consisting of copper alloys, such as cupronickel, and the pipe | tube consisting of other materials, such as aluminum, an aluminum alloy, titanium, and a titanium alloy, may be sufficient. In the present embodiment, the inner surface of the heat transfer tube is smooth, but ribs or the like may be formed in the tube as long as the pressure loss of the fluid flowing in the tube and the progress of corrosion can be suppressed. Furthermore, in the present embodiment, the shape of the protrusion is a quadrangular pyramid, but a quadrangular prism shape is more desirable. However, the protrusion shape is not limited to a quadrangular pyramid shape and a quadrangular prism shape, and may be any shape as long as it has excellent refrigerant condensing performance and is easy to manufacture. For example, it may be a quadrangular pyramid shape, a triangular prism shape, or the like. . When the projection shape is a triangular prism shape, the longitudinal direction is preferably the tube axis direction or the tube circumferential direction. Furthermore, the present invention can be suitably applied to refrigerants having high viscosity and high surface tension other than water. The arrangement direction of the protrusions may be inclined with respect to the tube axis or may be orthogonal. There is no difference in heat transfer performance between the two. Furthermore, the bottom wall thickness is preferably about 0.3 to 0.7 mm. In consideration of heat transfer performance, the bottom wall thickness is preferably as thin as possible, but the bottom wall thickness is preferably set appropriately in consideration of corrosion resistance and workability.

Hereinafter, the effect of the embodiment of the present invention will be specifically described in comparison with a comparative example that deviates from the scope of the claims. Various heat transfer tubes were produced by the same method as in the above-described embodiment of the present invention, and used as test tubes. Table 2 shows the shapes of the test tubes of Examples and Comparative Examples. As a comparative example, a heat transfer tube having a plurality of protrusions formed on the outer surface of the tube and having protrusions whose dimensions and arrangement pitch are outside the scope of the present invention, a corrugated tube and a smooth tube were prepared. Note that “independent protrusion” in the column of “outer surface shape” in Table 2 refers to a shape in which a plurality of independent protrusions are formed on the outer surface of the tube, and “corrugated” refers to a corrugated tube. “Outer diameter” indicates the maximum outer diameter of the heat transfer tube, that is, the diameter of the envelope circle at the tip of the protrusion, and in the case of a corrugated tube, the outer diameter of the corrugated portion. Furthermore, “bottom wall thickness” indicates the thickness of the heat transfer tube in the groove, and in the case of a corrugated tube, indicates the thickness of the corrugated portion. Furthermore, “tube axis” in “arrangement pitch” and “groove width” refers to a value in the tube axis direction, and “tube circumference” refers to a value in the tube circumferential direction. Furthermore, “P _c ” indicates the arrangement pitch (corrugated pitch) P _c in the tube axis direction of the grooves 82 in the corrugated tube 81 shown in FIG. 9, and “h _c ” indicates the depth of the grooves 82 shown in FIG. (Corrugated depth) h _c .

  Test tube No. shown in Table 2 Reference numerals 1 to 24 are independent protrusion type heat transfer tubes manufactured by rolling, and a low phosphorus deoxidized copper tube (JIS H3300 C1201Ts-1 / 2H) having an outer diameter of 16 mm and a wall thickness of 0.65 mm. It was made using In the present embodiment, the projection height can be made lower than the fin height (0.85 mm) of the heat transfer tube described in Patent Document 1 (Patent No. 3415013) described above, so that the thickness of the material is small. It is possible to process even if is used. Further, the length of the heat transfer tube is set to 1200 mm for the protrusion processing portion including the incompletely formed portion, and the length of the unprocessed portion at the end of the tube, respectively, in order to match the test apparatus for evaluating the heat transfer performance described later. A heat transfer tube having a length of 150 mm and a total length of 1500 mm was produced. In the rolling process, fins are formed by pressing the rolling disk group from three directions at intervals of 120 ° from the outer surface of the pipe. At the same time, the fin formed by the final machining disk of the rolling disk group is grooved on the edge The processed gear disk was pressed to form an independent protrusion. The inclination angle after forming the protrusion, that is, the angle θ (see FIG. 1) formed by the line 6 extending in the direction in which the protrusions 3 are arranged and the line 7 extending in the pipe circumferential direction on the outer surface of the pipe body 2 is 2.1 to The angle was 3.5 °.

After forming independent protrusions on the outer surface of the tube in this manner, the tube was heated to a temperature of about 350 ° C. to remove residual stress and to heat and degrease the residual oil on the tube surface. The tensile strength of the heat transfer tube after heating was 275 N / m ² on average. Thereafter, liquid chlorofluorocarbon (HCFC-141b) was applied to the outer surface of the tube, and after collecting the liquid chlorofluorocarbon, the residue was evaporated to remove the residue on the outer surface of the tube. As a result of measuring the amount of residue on the outer surface of the tube after the residue removal treatment with liquid chlorofluorocarbon, it was 0.010 to 0.020 g / m ² . Further, the amount of residual carbon in the pipe was measured. First, the heat transfer tube was washed using liquid chlorofluorocarbon (HCFC-141b) to remove oil remaining on the inner surface. Next, a mixed solution of an aqueous nitric acid solution and an aqueous hydrochloric acid solution was sealed in a tube to elute residual carbon into the solution, and this solution was filtered with a glass fiber filter paper to separate the residual carbon. Next, the separated carbon was heated and oxidized in air, and the CO ₂ concentration was measured by a detector EMIA-U510 manufactured by Shimadzu Corporation. Then, converts the measured value of the CO ₂ concentration in the residual carbon amount per unit area, determine the amount of residual carbon. As a result of measuring the amount of residual carbon in this way, the amount of residual carbon in the heat transfer tube after processing was 3.4 to 4.4 mg / m ² . If there is a large amount of residue on the outer surface of the tube, this becomes a thermal resistance, which reduces the heat transfer performance. For this reason, the amount of residue is desirably 0.3 g / m ² or less. In addition, if the amount of residual carbon on the inner surface of the tube is large, holes due to corrosion are likely to occur. Therefore, the amount of residual carbon is preferably 5 mg / m ² or less.

  The heat transfer performance of the test tubes thus prepared was evaluated. FIG. 5 is a schematic view showing a test apparatus used for evaluation of heat transfer performance. As shown in FIG. 5, in this test apparatus, a steam generator 11, a low-temperature regenerator 12, a condenser 13 and a solution tank 14 of a shell and tube heat exchanger are provided. The test apparatus main body is made of stainless steel (SUS304 and SUS316), and suppresses corrosion caused by the aqueous lithium bromide solution.

  The steam generator 11 is provided with an electric heater 15 having a capacity of 30 kW. The steam generator 11 boils distilled water by an electric heater 15 to generate water vapor, and supplies it to the low temperature regenerator 12. The boiling pressure of the steam generator 11 is in the range of 12.3 to 60 kPa, the temperature is in the range of 50 to 80 ° C., the in-machine pressure of the low-temperature regenerator 12 (LiBr side pressure), and the in-machine pressure of the condenser 13. (Water vapor side pressure) is controlled to be equal to each other. Further, the water condensed in the low temperature regenerator 12 is returned to the steam generator 11.

  The low temperature regenerator 12 is supplied with the LiBr aqueous solution 16 from the solution tank 14 and holds it. A heat transfer tube 17 is provided so that water vapor is supplied from the steam generator 11 to the inside and the outer surface is immersed in the LiBr aqueous solution 16. In the low-temperature regenerator 12, the LiBr aqueous solution 16 is supplied around the heat transfer tube 17, and water vapor is supplied to the inside of the heat transfer tube 17, whereby heat exchange is performed between the LiBr aqueous solution 16 outside the tube and the water vapor in the tube. To do. Thereby, the LiBr aqueous solution 16 outside the tube is boiled to generate water vapor, and this water vapor is supplied to the condenser 13 as refrigerant vapor. This also concentrates the LiBr aqueous solution. The LiBr aqueous solution circulates between the solution tank 14. Further, the water vapor supplied into the heat transfer tube 17 is condensed and returned to the steam generator 11.

  In the condenser 13, the test tube 18 is installed horizontally, and the end of the tube is fixed by an O-ring (not shown). Further, a baffle plate (not shown) is installed at the refrigerant vapor inlet so that the refrigerant vapor (water vapor) supplied from the low temperature regenerator 12 does not directly hit the test tube 18. The test tube 18 is connected to a cooling tower 19, and the cooling water cooled by the cooling tower 19 is supplied into the test tube 18 by a pump 20. Then, heat is exchanged between the cooling water supplied into the tube of the test tube 18 and the refrigerant vapor (water vapor) supplied from the low temperature regenerator 12 to the outside of the tube, and the heated cooling water is supplied to the cooling tower 19. Returning, the liquid refrigerant (water) condensed on the surface of the test tube 18 moves to the solution tank 14 by its own weight.

  A LiBr aqueous solution 16 is held in the solution tank 14, and a liquid refrigerant (water) is supplied from the condenser 13 to dilute the LiBr aqueous solution 16. The solution tank 14 is provided with a pump 21, and the LiBr aqueous solution 16 is circulated between the solution tank 14 and the low temperature regenerator 12.

  An electromagnetic flow meter 22 and a platinum resistance temperature detector (JIS-A class) 23 are provided at the inlet of the test tube 18, and a platinum resistance temperature detector 23 is also provided at the outlet of the test tube 18. . The steam generator 11 and the condenser 13 are each provided with a diaphragm type absolute pressure converter 24.

  Next, a method for evaluating heat transfer performance using this test apparatus will be described. In the steam generator 11, the electric heater 15 generates water vapor and supplies it into the heat transfer tube 17 of the low temperature regenerator 12. Thereby, heat exchange is performed between the water vapor in the heat transfer tube 17 and the LiBr aqueous solution 16 outside the heat transfer tube 17, the water vapor is condensed and returned to the steam generator 11, the LiBr aqueous solution 16 is boiled, and the water vapor is refrigerant vapor. To the condenser 13. In the condenser 13, cooling water whose temperature is adjusted to be constant is supplied from the cooling tower 19 into the test tube 18, and steam (refrigerant vapor) is supplied from the low-temperature regenerator 12 to the outside of the test tube 18. Heat exchange is performed between cooling water and water vapor. Thereby, water vapor (refrigerant vapor) condenses into water (refrigerant liquid) and moves to the solution tank 14 by gravity. In the solution tank 14, water is supplied from the condenser 13, and the LiBr aqueous solution 16 is circulated with the low-temperature regenerator 12 to keep the concentration of the LiBr aqueous solution 16 in the low-temperature regenerator 12 constant. At this time, the condensation pressure is measured by the diaphragm type absolute pressure converter 24 provided in the condenser 13, the cooling water inlet / outlet temperature is measured by the platinum resistance thermometer 23, and the cooling water flow rate is measured by the electromagnetic flow meter 22. did. Table 3 shows the heat transfer performance evaluation conditions. The pipe water flow rate is based on the pipe end, and the pipe pressure loss evaluation is based on the machining section inner diameter.

  After starting operation of the test apparatus, it was confirmed that a steady state was reached, and the pressure in the condenser 13, the flow rate of the cooling water, and the inlet / outlet temperature were measured. And the signal of each measuring device was taken in into the hybrid recorder (not shown), and it converted into a numerical value, and the total heat transfer coefficient of the heat exchanger tube was computed. Hereinafter, the calculation method will be described.

(1) Cooling water heat transfer amount Q
Cooling water heat transfer amount is Q (kW), cooling water flow rate is G (kg / hour), specific heat of cooling water is Cp (kJ / kg / K), cooling water inlet temperature is Tin (° C.), cooling water The heat transfer amount Q of the cooling water was calculated by the following formula 1 when the outlet temperature of T was set to Tout (° C.).

(2) Logarithmic average temperature difference ΔTm
When the logarithm average temperature difference is ΔTm (° C.) and the refrigerant condensing temperature is Ts (° C.), the logarithm average temperature difference ΔTm is calculated by the following formula 2. In addition, the refrigerant | coolant condensation temperature Ts used the value calculated and converted from the condensation pressure.

(3) External surface area Ao
The outer surface area of the test tube is Ao (m ² ), the circumference is π, the outer diameter of the protrusion of the test tube, that is, the maximum outer diameter of the test tube is Do (m), and the effective heat transfer length of the test tube is L ( m) When the number of test tubes is N (number), the outer surface area Ao of the test tubes was calculated by the following formula 3 based on the protrusion outer diameter.

(4) Overall heat transfer coefficient Ko (outside surface area standard)
When the overall heat transfer coefficient based on the outer surface area is set to Ko (kW / m ² K), the overall heat transfer coefficient Ko is calculated by the following expression 4 using the values calculated in the above expressions 1 to 3. The larger the value of the overall heat transfer coefficient Ko, the better the heat transfer performance of the heat transfer tube.

  The values of the overall heat transfer coefficient Ko calculated in this way are shown in Table 4.1 to Table 4.4 and FIG. FIG. 6 is a graph plotting the calculation results shown in Tables 4.1 to 4.4 with the horizontal axis representing the flow rate of cooling water and the vertical axis representing the overall heat transfer coefficient.

  As shown in Tables 4.1 to 4.4 and FIG. Since the outer surface shape of the heat transfer tubes according to 1 to 13 satisfies the scope of the present invention, Comparative Example No. Compared with the heat transfer tubes according to 14 to 26, the overall heat transfer coefficient Ko was high, and the heat transfer performance was excellent. In particular, Example No. In the heat transfer tubes according to Nos. 12 and 13, since the protrusion shape is a quadrangular prism shape, the protrusion shape is a square frustum shape. The heat transfer performance was superior to 1 to 11. In addition, Example No. In Comparative Examples Nos. 1 to 13, even though the pipe inner surface is smooth. The heat transfer performance was higher than that of the corrugated tube shown in FIG. In contrast, Comparative Example No. In Nos. 14 to 26, the shape of the outer surface of the pipe did not satisfy the provisions of the present invention, and the heat transfer performance was inferior.

It is a fragmentary perspective view which shows the heat exchanger tube which concerns on embodiment of this invention. It is a pipe-axis parallel sectional view containing the pipe axis which shows this heat exchanger tube. It is a tube axis orthogonal sectional view showing this heat exchanger tube. It is a figure which shows the operation | movement which the refrigerant | coolant liquid condensed in this embodiment remove | deviates from a heat exchanger tube. It is the schematic which shows the test apparatus used for evaluation of heat-transfer performance. It is the graph which plotted the calculation result shown in Table 4.1 thru | or Table 4.4, taking the flow rate of cooling water on a horizontal axis | shaft and taking a general heat transfer coefficient on the vertical axis | shaft. It is sectional drawing which shows an example of the condenser of a shell and tube system. It is sectional drawing which shows an example of the condenser of a shell and coil system. It is side surface sectional drawing which shows a corrugated tube.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Heat transfer pipe 2; Pipe main body 3; Protrusion 4a, 4b; Groove part 5; Refrigerant liquid (condensed water)
11; Steam generator 12; Low temperature regenerator 13; Condenser 14; Solution tank 15; Electric heater 16; LiBr aqueous solution 17; Heat transfer tube 18; Test tube 19; Cooling tower 20, 21; Platinum resistance thermometer 24; Diaphragm type absolute pressure transducer 51; Shell and tube type condenser 52; Body portion 53; Tube plate 54; Refrigerant vapor inlet 55; Refrigerant liquid outlet 56, 57; Lid portion 58; 59, 65; Partition plates 60-62, 66, 67; Chamber 63; Coolant inlet 64; Coolant outlet 71; Shell-and-coil condenser 72; Chamber 73; Refrigerant vapor inlet 74; Refrigerant liquid outlet 75; Cooling liquid inlet 76; coolant outlet 77; the heat exchanger tubes 81, the corrugated tube 82; groove 83; protrusion 84; recess h; the height of the projection h _c; corrugation depth P ₁ Projecting the tube outer surface; corrugated pitch W _1;; width θ of the groove in the circumferential direction of the _pipe; width W 2 of the groove in the tube axis direction arrangement pitch P c of the protrusions in the circumferential direction of the _pipe; arrangement pitch P 2 of the protrusions in the tube axis direction Between the line extending in the direction in which they are arranged and the line extending in the pipe circumferential direction

Claims (2)

It has a tube main body and a plurality of protrusions arranged on the outer surface of the tube main body and arranged in a direction orthogonal to or inclined with respect to the tube axis direction. Water or brine is circulated in the tube and water vapor is brought into contact with the tube outer surface. In the heat transfer tube for a condenser that performs heat exchange between the water vapor and the water or brine by condensing the water vapor, the arrangement pitch of the protrusions in the tube axis direction is 0.70 to 1.42 mm, The projection pitch in the tube circumferential direction is 0.45 to 0.65 mm, and the width of the groove formed between the projections in the tube axis direction is 0.30 to 0.80 mm. A condenser heat transfer tube, wherein a width in a direction is 0.12 to 0.38 mm, and a height of the protrusion is 0.18 to 0.50 mm. The heat transfer tube for a condenser according to claim 1, wherein the shape of the protrusion is a quadrangular pyramid shape or a quadrangular prism shape.

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