JPH0635920B2 - Heat transfer tube for heat exchanger - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat transfer tube for a heat exchanger used in an air conditioner refrigerator or the like.

"Prior Art" Conventionally, heat exchanger tubes for heat exchangers that have been put to practical use are made of copper or a copper alloy in order to improve heat transfer efficiency,
There are a pipe having a smooth inner surface (smooth pipe) and a pipe having a spiral groove formed on the inner surface (grooved pipe) to further improve thermal efficiency.

[Problems to be Solved by the Invention] As is well known, in order to improve the heat transfer efficiency of a heat transfer tube, (a) the heating area is increased.

(B) Make nucleate boiling easier.

(C) Capillarity tends to occur.

(D) Turbulence tends to occur.

Is said to be effective.

On the other hand, in the above conventional heat transfer tube, particularly in the smooth tube, the above items have not been sufficiently satisfied, and therefore, the heat transfer tube having higher thermal efficiency is required at present. Further, in the grooved tube of the above heat transfer tubes, this grooved tube is mainly manufactured by the rolling method, and in this method, the processing speed is slow, and the number of spiral grooves and the twisting angle of the spiral groove are considered in the rolling technology. However, there are drawbacks such as limitations, etc., and therefore improvement in performance cannot be obtained at the expense of production efficiency.

"Means for Solving the Problems" The present invention has been made to solve the above problems, and the inner surface of a tubular body made of copper or a copper alloy with a smooth inner surface or a groove with an inner surface is almost the same as the inner diameter of the tubular body. It is characterized in that a spiral wire made of copper or a copper alloy, which is formed by spirally forming a spiral extra fine wire or a twisted wire with a winding diameter of a size, is closely fixed.

[Operation] In this heat exchanger tube for heat exchanger, since the spiral wire formed by spirally winding either a spiral extra fine wire or a stranded wire is fixed to the inner surface of the tube, the surface area in contact with the heat medium Is significantly increased, and the flow of the heat medium in the tube becomes a turbulent flow, so that the heat exchange efficiency between the heat medium and the tube can be improved.

In addition, if the pitch of the spiral wire is narrowed, a thin and continuous void is formed between the spiral wire and the tubular body, and a void rich in capillary force is also formed inside the spiral wire itself. The total capillary force is remarkably larger than that of the spiral wire, and the transport efficiency of the liquefied heat medium is enhanced by the capillary force of these voids, and the transport efficiency of the heat medium can be remarkably enhanced.

In addition, spiral fine wires and stranded wires are rich in fine undulations and have higher surface activity than smooth spiral wires, so that good boiling nuclei and
It can act as a condensation nucleus and promote boiling and condensation of the heat carrier.

"Embodiment" FIG. 1 is a perspective view showing an embodiment of a heat transfer tube for a heat exchanger according to the present invention.

In the figure, reference numeral 1 is a tubular body made of copper or a copper alloy, and an inner surface 1a of the tubular body 1 is smooth, and a spiral spiral wire 2 is provided on the inner surface 1a over the entire length of the tubular body 1. It is fixed tightly. The spiral wire 2 is formed by twisting a twisted wire formed by twisting a copper or copper alloy extra fine wire 3 into a spiral shape at a close contact pitch.

In order to fix the spiral wire 2 to the inner surface 1a of the pipe body 1, first, the stranded wire is previously wound around a winding core metal bar having a diameter slightly smaller than the inner diameter of the pipe body 1 at an equal pitch or a close pitch. The core bar is inserted into the tubular body 1 and then the both ends of the stranded wire are released. Then, the winding diameter of the stranded wire is expanded by the force of the spring back, and the tightening force for the cored bar is relaxed, so that the cored bar is pulled out from the tube body 1.

Even in this state, the spiral wire 2 is tightly fixed to the inner surface 1a of the tubular body 1 by the stress of the spring back, but it is desirable that the spiral wire 2 be securely tightly fixed by any of the following four methods.

(I) A fixed plug or a floating plug is inserted into the inside of the tube body 1, or the tube body 1 is reduced in diameter by inserting a drawing die without inserting anything (drawing method).

(Ii) The tube body 1 is squeezed by two opposing rolls each having a semicircular caliber or two claw type rolls (roll pressure method).

(Iii) While injecting a water-soluble flux into the tube body 1, inserting a solder wire, and then introducing an inert gas or a reducing gas while heating by using an induction heater or a bright annealing furnace, Soldering is performed (brazing method). In this case, if the spiral wire 2 is plated with a low melting point metal in advance, the brazing becomes easy.

(Iv) A plating solution and an anode are put into the tube body 1 and the tube body 1 is plated as a cathode (plating method).

The spiral wires 2 may be formed at a pitch with a space therebetween, but if they are arranged at a close pitch as shown in the drawing, a spirally continuous gap 4 can be easily formed between the spiral wire and the inner surface 1a of the tubular body 1. Can be formed.

According to the heat transfer tube having the above structure, since the spiral wire 2 made of a stranded wire is fixed to the inner surface 1a of the tube body 1, the contact area with the heat medium is significantly increased, and The effect of making the flow of the heat medium turbulent can be obtained, and the heat exchange efficiency between the heat medium and the tubular body 1 can be improved.

In addition, since the spiral wire 2 has a close contact pitch, a thin and continuous void 4 is formed between the spiral wire 2 and the tubular body 1, and the capillary force is exerted between the ultrafine wires 3 forming the spiral wire 2 as well. Since the minute voids rich in water are formed, the overall capillary force is remarkably large compared to the case where a simple spiral wire is used, and the transport efficiency of the liquefied heat medium is increased to significantly improve the transport efficiency of the heat medium. Can be improved.

Further, since the spiral wire 2 is a stranded wire, it is rich in fine undulations and has a higher surface activity than a smooth spiral wire, so that it acts as a good boiling nucleus / condensation nucleus and can promote boiling and condensation of the heat medium.

Further, since the winding direction of the spiral wire 3 is close to 90 ° with respect to the axial direction of the tube body 1 (the flow direction in the tube body 1), the effect of generating turbulence on the heat medium in the tube body 1 is high, Also from this point, the heat transfer efficiency can be improved.

Further, the copper or copper alloy stranded wire forming the spiral wire 2 is extremely easy to obtain, and the spiral wire 2 is also easily manufactured, so that the cost is relatively low.

Furthermore, since the minimum winding diameter of the spiral wire 2 is limited only by the manufacturing lower limit of the winding core metal bar, it is possible to form even a very small winding diameter, and therefore 4 mm.
It is also possible to manufacture extremely thin heat transfer tubes of φ or 3 mmφ.

Next, FIG. 2 shows a modified example of the spiral wire 2. The spiral wire 2 is formed by spirally winding a fine diameter spiral in which a single fine wire 5 made of copper or copper alloy is spirally wound. It has a double spiral structure and is fixed to the inner surface of a tubular body (not shown). Other configurations may be similar to those of the above embodiment.

Also in this example, the same effect as that of the above-described embodiment can be obtained.

Although the tubular body 1 is a smooth tube in the above embodiment, a grooved tube can be used instead of the smooth tube, and in that case, the heat exchange efficiency can be further improved.

"Effects of the Invention" As described above, according to the heat transfer tube for a heat exchanger of the present invention, the following excellent effects can be obtained.

Since the spiral wire consisting of a spiral extra fine wire or stranded wire is fixed to the inner surface of the tube, the contact area with the heat medium is significantly increased, and the flow of the heat medium in the tube becomes turbulent and The heat exchange efficiency between the medium and the pipe can be improved.

If the pitch of the spiral wire is narrowed, a thin and continuous void is formed between the spiral wire and the tubular body, and a void with rich capillary force is also formed inside the spiral wire itself, so a simple spiral The overall capillary force is remarkably large as compared with the line, and the transport efficiency of the liquefied heat medium is increased by the capillary force of these voids, and the transport efficiency of the heat medium can be remarkably enhanced.

Since the spiral fine wire and the twisted wire are rich in fine undulations and have higher surface activity than the smooth spiral wire, they act as good boiling nuclei and condensation nuclei, and can promote boiling and condensation of the heating medium.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a heat transfer tube for a heat exchanger according to the present invention, and FIG. 2 is a plan view showing a modification of a spiral wire. 1 ... Tube, 1a ... Inner surface, 2 ... Spiral wire, 3 ... Extra fine wire constituting stranded wire, 4 ... Void, 5 ... Spiral extra fine wire.

Claims (1)

[Claims] 1. A spiral extra fine wire or a twisted wire having a winding diameter substantially the same as the inner diameter of the tubular body is provided on the inner surface of the tubular body having a smooth inner surface or a groove with an inner surface made of copper or copper alloy. A heat transfer tube for a heat exchanger, characterized in that a spiral wire made of copper or a copper alloy formed in a spiral shape is closely fixed.