JP2005121238A - Heat transfer tube for boiling - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat transfer tube for boiling capable of realizing performance enhancement and miniaturization of a heat exchanger. <P>SOLUTION: A cavity 5 that is continuous in a tube circumferential direction is formed by pluralities of first fins 3 and second fins 4, and a tube body 2. An inlet 6 that is continuous in the tube circumferential direction, and an outlet 7 communicated with the cavity 5 and the outside are formed between a tip 3A of the first fin 3 and a tip 4A of the second fin 4. A refrigerant is sent in from the inlet 6, and discharge of bubbles of boiled refrigerant from the outlet 7 is carried out. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heat transfer tube for boiling which is incorporated in an evaporator of a large-scale refrigerator such as a turbo refrigerator or a screw refrigerator and is immersed in the refrigerant to heat and boil the refrigerant. The present invention relates to a heat transfer tube for boiling that can be downsized.

  Conventionally, various heat transfer tubes having different heat transfer surface shapes have been proposed (see, for example, Patent Documents 1 to 3).

  FIG. 4 shows the heat transfer tube for boiling shown in Patent Document 1. The heat transfer tube 30 for boiling includes a cavity 32 formed continuously between a fin 32 erected on the upper surface of the tube body 31, a fin tip 32 </ b> A and adjacent fins 32, and a cavity 33. Holes 34 formed at predetermined intervals and connected to the outside are provided. The ratio of the total area of the hole 34 and the surface 35 is 2 to 50%. According to the boiling heat transfer tube 30, the cavity 33 has an action of promoting the boiling of the refrigerant flowing from the hole 34, and by changing the area of the hole 34, air bubbles remaining in the cavity 33 are secured. Heat transfer efficiency can be improved.

  FIG. 5 shows the heat transfer tube for boiling shown in Patent Document 2. This boiling heat transfer tube 40 compresses and deforms the tip of the fin standing on the upper surface of the tube body 41 to form a block-like protrusion 42, and the block-like protrusion 42 forms a cavity 43 extending along the pipe circumferential direction. The gap portion 44 having a width of 0.13 mm or less that communicates the cavity 43 with the outside, the cavity 43A that is shallow in the axial direction perpendicular to the cavity 43, and the width that communicates the cavity 43A with the outside is 0.13 mm or less. The gap portion 44A is provided. According to the boiling heat transfer tube 40, the cavities 43 and 43A have an action of promoting the boiling of the refrigerant flowing in, and the refrigerant that has become bubbles in the cavities 43 and 43A passes through the gaps 44 and 44A. Discharged. By setting the width of the gaps 44 and 44A to 0.13 mm or less, it is possible to secure the bubbles remaining in the cavities 43 and 43A and improve the heat transfer efficiency.

6 shows the heat transfer tube for boiling shown in Patent Document 3. As shown in FIG. The heat transfer tube 50 for boiling includes a fin 52 erected on the upper surface of the tube main body 51, a T-shaped fin 54 with a tip 54 </ b> A abutting the fin 52, and the fin 52 and the T-shaped fin 54. A cavity 53 formed in the direction, and an opening 55 formed at the tip 54A of the T-shaped fin 54 and connected to the cavity 53 and the outside. According to the boiling heat transfer tube 50, since the refrigerant around the boiling heat transfer tube 50 is heated by the fins 52, the temperature of the refrigerant when entering the cavity 53 can be increased. Bubbles grow faster. Therefore, the heat transfer efficiency is increased and the size can be reduced.
Japanese Examined Patent Publication No. 53-253379 (FIG. 1) Japanese Examined Patent Publication No. 64-2878 (FIG. 6) JP-A-6-323778 (FIG. 1)

  However, according to the heat transfer tube for boiling described in Patent Document 1, the nucleate boiling in the cavity is good, but the bubbles discharged from the holes and the refrigerant before entering the cavity are not easily heated. It is difficult to improve. Further, since the hole through which the refrigerant enters the cavity and the hole through which the bubbles are discharged are the same, there is a possibility that the inflow of the refrigerant and the discharge of the bubbles may not be performed smoothly.

  Moreover, according to the heat transfer tube for boiling described in Patent Document 2, the flow of the refrigerant from the cavity provided in the axial direction into the cavity in the circumferential direction of the tube is not smooth due to a large pressure loss, and the heat transfer performance is improved. Is difficult. In addition, the intersection of the circumferential cavity and the axial cavity is wide open, and the refrigerant flows into the circumferential cavity where nucleate boiling occurs, so that nucleate boiling occurs. It becomes easy to be inhibited at this part.

  Moreover, according to the heat transfer tube for boiling described in Patent Document 3, since the refrigerant around the heat transfer tube for boiling is heated by the fins, the temperature of the refrigerant flowing into the cavity is increased, so that the heat transfer efficiency is increased. However, since the fins protrude, the heat transfer tube for boiling is enlarged. Further, since the opening through which the refrigerant enters the cavity and the opening through which the bubbles are discharged are the same, there is a risk that the inflow of the refrigerant and the discharge of the bubbles may not be performed smoothly.

  Accordingly, an object of the present invention is to provide a heat transfer tube for boiling which promotes nucleate boiling and improves heat transfer performance by smoothly flowing in refrigerant and discharging bubbles.

  In order to achieve the above object, the present invention provides a tube main body through which a heating medium flows, a plurality of first fins provided on an outer peripheral surface of the tube main body, and a predetermined distance from the plurality of first fins. A cavity having an inflow port through which a refrigerant flows is formed by being combined with the plurality of first fins and formed on the outer peripheral surface of the tube main body with a gap therebetween, and the refrigerant flowing into the cavity is the heating medium And a plurality of second fins formed with a plurality of discharge ports for discharging bubbles when boiled to the outside.

  In the embodiment of the present invention, the plurality of second fins have notches formed at the tip portions thereof, the tip portions are bent toward the plurality of first fins, and the plurality of first fins. It is preferable to form an inflow port between the tip of each fin and a plurality of discharge ports that communicate the cavity with the outside.

  In the embodiment of the present invention, the discharge port has a size corresponding to the size of the bubbles of the refrigerant boiled by the heating medium and discharged to the outside, and the inflow port flows the refrigerant into the cavity, It is preferable to have a size smaller than the size of the outlet so as to prevent the bubbles from flowing out to the outside.

  In the embodiment of the present invention, the inlets preferably have a distance of 0.02 to 0.2 mm.

  In the embodiment of the present invention, the interval between the plurality of cavities is preferably 0.1 to 0.8 mm.

  According to the heat transfer tube for boiling of the present invention, since the opening for discharging the bubbles to the outside and the inlet for introducing the refrigerant into the cavity are formed, the inflow of the refrigerant by discharging the bubbles is not hindered by the bubbles. Is promoted, the flow of the refrigerant and bubbles in the cavity is smooth, the heat transfer performance of the refrigerant is improved, and the high performance and miniaturization of the heat exchanger can be realized.

  According to the heat transfer tube for a boiling tube of the present invention, since the inlet and outlet can be formed by bending the tip portions of the plurality of second fins toward the plurality of first fins, A heat transfer tube can be formed.

  According to the heat transfer tube for boiling of the present invention, the discharge port has a size corresponding to the size of the bubbles of the refrigerant boiled by the heating medium and discharged to the outside, and the inflow port puts the refrigerant in the cavity. In order to prevent inflow and outflow of the bubbles to the outside, the size is smaller than the size of the discharge port, so that the flow of refrigerant and bubbles in the cavity is smooth, improving the heat transfer performance of the refrigerant Therefore, it is possible to realize high performance and miniaturization of the heat exchanger.

  According to the heat transfer tube for boiling of the present invention, since the inflow port has a gap of 0.02 to 0.2 mm, the bubbles of the refrigerant cannot come out of the inflow port. The discharge point can be made different.

  According to the heat transfer tube for boiling of the present invention, since the interval between the plurality of cavities is 0.1 to 0.8 mm, the refrigerant can easily flow into the cavities.

  FIG. 1 shows a heat transfer tube for boiling according to an embodiment of the present invention. The boiling heat transfer tube 1 is formed on the tube main body 2, the first fin 3 erected from the outer peripheral surface of the tube main body 2, and the outer peripheral surface of the tube main body 2, and covers the tip portion 3 </ b> A of the first fin 3. And a second fin 4 whose tip is bent.

  The first fin 3, the second fin 4, and the pipe body 2 form a cavity 5 that is continuous in the pipe circumferential direction. The tip portion 3A of the first fin 3 and the tip portion 4A of the second fin 4 are formed to be tapered, and an inflow port 6 is formed therebetween. The front end 4A of the second fin 4 is cut out at a predetermined interval to form a discharge port 7. The discharge ports 7 are offset from the discharge ports 7 formed in adjacent second fins by a half pitch.

  FIG. 2 shows a manufacturing process of the heat transfer tube for boiling according to the embodiment of the present invention. First, as shown in FIG. 2A, a tube 1A having a smooth outer peripheral surface is prepared, and a first cutting tool 10A and a second cutting tool 10B having a cutting edge angle of 60 ° are connected to a predetermined cutting angle and a predetermined cutting angle. The first cutting tool 10A and the second cutting tool 10B are arranged so as to be shifted in the tube axis direction and the tube circumferential direction so that the insertion amount and the interval between the formed fins 3 and 4 have predetermined dimensions. The first cutting tool 10A and the second cutting tool 10B are brought into contact with the pipe body 2 and rotated in the circumferential direction of the pipe 1A, and the pipe 1A is moved in the axial direction so that the first fin 3 and the second fin 4 are Wake up. At this time, in order to form the first and second fins 3 and 4 having different heights, it is necessary to adjust the cutting amount of each of the first cutting tool 10A and the second cutting tool 10B. The cutting amount of the cutting tool 10A was set to 0.10 mm, and the cutting amount of the second cutting tool 10B was set to 0.25 mm. Further, the rotation speed of the first cutting tool 10A and the second cutting tool 10B and the feed speed of the pipe 1A were adjusted so that the space between the cavities in the tube axis direction was 0.3 mm. Since the fins 3 and 4 formed thereby are raised by the first cutting tool 10A and the second cutting tool 10B, the tip portions are sharply formed.

  Next, as shown in FIG. 2B, the grooved roll 11 is rotated while being pressed against the second fin 4 by 0.2 mm, and the tube 1A is moved in the tube axis direction so that the second fin 4 has a triangular shape. A plurality of cutouts 4A having a shape were formed.

  Next, as shown in FIG. 2C, the flat roll 12 is rotated, the tube 1A is moved in the tube axis direction, the middle of the second fin 4 is bent toward the first fin 3, and the tube A cavity 5 continuous in the axial direction was formed. At this time, the inlet 6 continuous in the tube axis direction was formed by the tip 4A of the second fin 4 and the tip 3A of the first fin 3. If the distance between the tip of the tip 4A of the second fin 4 and the tip of the tip of the first fin 3 is too narrow, the inflow port 6 formed is too wide for the refrigerant 5 to flow into the cavity 5. Since the refrigerant excessively flows into the cavity 5 to inhibit nucleate boiling, the thickness is set to 0.02 to 0.2 mm. Further, the amount of bending the tip portion 3A of the first fin 3 so as to cover the tip portion of the second fin 4 was adjusted.

  If the interval between the cavities 5 in the tube axis direction is too short, it becomes difficult for the refrigerant to flow in. Conversely, if the interval is too wide, the nucleate boiling region in the cavities 5 decreases, so 0.1 mm to 0.8 mm is preferable.

  FIG. 3 is an enlarged view of a main part of the heat transfer tube 1 for boiling according to the embodiment of the present invention. The operation of this embodiment will be described with reference to FIG. In the heat transfer tube 1 for boiling according to the present invention, a continuous cavity 5 extends in a direction perpendicular to or inclined with respect to the tube axis, and the internal space of the cavity 5 is provided along the cavity 5 at a predetermined interval. The plurality of discharge ports 7 connected to each other and the inflow ports 6 between the fins forming the cavity 5 are connected to the outside.

  When the heat transfer tube 1 for boiling is immersed in the refrigerant, and the heating medium is flowed into the tube body 2 in a state where the refrigerant is filled with the refrigerant such as chlorofluorocarbon, the tube body 2 is heated by the heating medium. Heat is conducted to the first fin 3 and the second fin 4. These first and second fins 3 and 4 transmit heat to the refrigerant in the vicinity thereof and raise the temperature of the refrigerant. On the other hand, in the cavity 5, the first and second fins 3, 4 and the surface of the tube body 2 in contact with the refrigerant are heated, the refrigerant boils and bubbles 13 are actively generated. When the bubbles 13 grow to a certain size, they are detached from the first and second fins 3 and 4 and move into the refrigerant through the plurality of discharge ports 7. Since the bubbles 13 are usually larger than the interval between the inlets 6, the bubbles 13 are not discharged from the inlet 6, but gather at the outlet 7 along the tip portion 4 </ b> A of the tapered second fin and are discharged from the outlet 7. . At that time, the detachment of the bubbles 13 is facilitated by the tip portion 4 </ b> A of the tapered second fin forming the cavity 5. A part of the bubbles 13 remains as small bubbles 13 a in the cavity 5. An amount of refrigerant corresponding to the detached bubbles 13 flows into the cavity 5 from the inflow port 6. The refrigerant newly flowing into the cavity 5 is heated by the first and second fins 3 and 4 forming the cavity 5 and flows into the cavity 5 from the inlet 6 in a state where the temperature is rising. Reach boiling temperature with less heat. Therefore, the bubble 13 grows rapidly with the bubble 13a remaining in the cavity 5 as a nucleus.

  According to the heat transfer tube 1 for boiling according to the embodiment of the present invention, the place where the bubbles 13 are discharged from the cavity 5 and the place where the refrigerant enters the cavity 5 are different from each other. As a result, a route is formed in which the refrigerant is warmed and exits from the cavity 5 as the bubbles 13, and at the same time as the bubbles 13 exit from the cavity 5, the warmed refrigerant enters the cavity 5 to promote nucleate boiling. In addition, since the flow of the refrigerant and the bubbles 13 in the cavity 5 is smooth, the heat exchange efficiency is improved and the heat exchanger can be downsized.

  Further, since the cavities 5 are formed at predetermined intervals in the pipe circumferential direction, even when the cavities 5 are incorporated above the heat exchanger, the first and second fins between the cavities 5 are used for lower boiling. Since the bubbles 13 generated by the heat transfer tube 1 are difficult to enter and the refrigerant is well wetted, the heat transfer efficiency is further improved as compared with the conventional boiling heat transfer tube.

  In addition, although the shape of a notch, ie, the shape of the discharge port 7, is made into the triangle in FIGS. 1-3, shapes, such as a rectangle and a circle, may be sufficient. Further, the amount of bending of the higher fin for forming the cavity 5 may be such that the low fin is not covered.

It is a figure which shows the heat exchanger tube for boiling which concerns on embodiment of this invention, (a) is a perspective view, (b) is a top view, (c) is a cross-sectional view of (b). It is a figure which shows the manufacturing process of the heat exchanger tube for boiling which concerns on embodiment of this invention, (a) is a figure which shows the state which raised the 1st and 2nd fin, (b) is a figure of a 2nd fin The figure which shows the place which forms a notch in a front-end | tip, (c) is a figure which shows the place which bent the 2nd fin and formed the heat exchanger tube for boiling. It is explanatory drawing of operation | movement of the heat exchanger tube for a boiling which concerns on embodiment of this invention. FIG. 4 is a diagram showing the heat transfer tube for boiling shown in Patent Document 1. As shown in FIG. FIG. 5 is a diagram showing a boiling heat transfer tube disclosed in Patent Document 2. As shown in FIG. FIG. 6 is a diagram showing the heat transfer tube for boiling shown in Patent Document 3. As shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Boiling heat transfer tube 1A Tube 2 Tube body 3, 4 Fin 3A, 4A Tip 5 Cavity 6 Inlet 7 Discharge port 10A First bit 10B Second bit 11 Grooved roll 12 Flat roll 13 Bubble 13a Residual bubble 30 Boiling heat transfer tube 31 Tube body 32 Fin 32A Fin tip 33 Cavity 34 Hole 35 Surface 40 Boiling heat transfer tube 41 Tube body 42 Block-like projections 43, 43A Cavity 44, 44A Inlet 50 Boiling heat transfer tube 51 Tube body 52 Fin 53 Cavity 54A Tip 54 T-shaped fin 55 Opening

Claims (5)

A tube body in which a heating medium flows;
A plurality of first fins provided on an outer peripheral surface of the tube body;
A cavity is formed on the outer peripheral surface of the tube main body with a predetermined distance from the plurality of first fins, and has an inflow port through which the refrigerant flows by being combined with the plurality of first fins. A heat transfer tube for a boiling tube, comprising: a plurality of second fins formed with a plurality of discharge ports for discharging bubbles when the refrigerant that has flowed into the water boiled by the heating medium. The plurality of second fins have notches formed at the tip portions thereof, the tip portions are bent toward the first fin side, and between the tip portions of the plurality of first fins. Forming an inlet to the
The heat transfer tube for boiling according to claim 1, wherein a plurality of discharge ports connecting the cavity and the outside are formed. The discharge port has a size corresponding to the size of bubbles of the refrigerant that is boiled by the heating medium and discharged to the outside,
The boiling point according to claim 1, wherein the inlet has a size smaller than a size of the outlet so as to allow the refrigerant to flow into the cavity and prevent the bubbles from flowing out to the outside. Heat transfer tube for tube.   The heat transfer tube for boiling according to claim 3, wherein the inlet has an interval of 0.02 to 0.2 mm. The heat transfer tube for boiling according to claim 3, wherein the plurality of cavities have an interval of 0.1 to 0.8 mm.

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