JPS60200095A - Heat transfer pipe - Google Patents

Abstract

PURPOSE:To enable to increase the coefficient of overall heat transmission and to decrease pressure loss, by providing a plurality of projections, having uprising surfaces on the upstream side and downwardly inclined to the downstream direction, on the inner wall of a pipe at a specified pitch, slanted against the axis of a pipe, in a heat transfer pipe. CONSTITUTION:Projections 11 having a specified angle of inclinaion to the axis O of a pipe are provided on the inner wall of a pipe body 10 at the specified pitch, in a heat exchanger for a nuclear power plant. The projection 11 has a vertically uprising surface 11a on the upstream side of flow direction of cooling water which flows through the pipe bodyh 10, and an inclined surface 11b which is smoothly inclined downwardly along the flowing direction of cooling water flowing from the upper end of an uprising surface 11a. With such an arrangement, the coefficient of overall heat transmission becomes the maximum when the ratio of pitch Pt of a rib and the height (e) of a rib is around 40 and the angle of inclination theta is around 60 deg.. In such a manner, the coefficient of overall heat transmission can be increased, as well as to decrease the pressure loss in a heat transfer pipe.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to heat exchanger tubes, and is mainly used in heat exchangers in nuclear power plants to condense and liquefy water vapor existing outside the tubes. It relates to the heat exchanger tube used.

[Technical background of the invention and its problems]

Conventionally, heat transfer tubes have been used in heat exchangers in nuclear power plants, for example, to flow cooling water inside the tubes and condense and liquefy water vapor such as turbine exhaust existing outside the tubes. . In order to improve the heat transfer coefficient of the fluid in the tube, protrusions for forming turbulent flow are formed inside the tube by protruding from the inner peripheral surface of the tube.

As described above, while the protrusions formed as turbulence promoting means improve the heat transfer coefficient of the fluid inside the tube, on the other hand, the pressure loss of the fluid inside the tube increases. In other words, the conventional heat exchanger tubes that formed the turbulence promotion means had a large possibility of increasing the equipment cost and power cost of the cooling water circulation pump more than the benefit obtained by improving the heat transmission coefficient, and there was room for improvement. .

[Purpose of the invention]

SUMMARY OF THE INVENTION The present invention was created in view of the conventional problems of slanted tubes, and an object of the present invention is to provide a heat exchanger tube that has a high heat transmission coefficient and a low pressure loss.

[Summary of the invention]

In order to achieve the above-mentioned object, the present invention has an upright surface on the inner circumferential surface of the tube body that stands vertically from the inner circumferential surface of the tube body on the upstream side in the flow direction of the fluid in the tube, and also has an upright surface on the F flow side. This is characterized in that a number of protrusions are formed at a required pitch, each having a sloped surface that gently descends from the upper end of the upright surface along the flow direction, and are inclined with respect to the tube axis of the tube body.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

The reference numeral 10 shown in the figure is a tube body, and the inner peripheral surface of this tube body 10 is provided with protrusions 1 at predetermined intervals along the tube axis O.
1 is made of fiber, and the protrusion 11 itself is inclined at a predetermined inclination angle θ with respect to the tube axis 0.

The cross-sectional shape of the protrusion 11 includes an upright surface 11m that stands up perpendicularly from the inner surface of the tube body 10 on the upstream side, which is the front side in the flow direction of the tube fluid such as cooling water flowing inside the tube body 10;
Similarly, on the upstream side in the flow direction of the fluid in the pipe, there is an inclined surface 11 that gently descends from the upper end of the upright surface 11a along the flow direction.
Assume that it is a right triangle with b.

The tube body lO and the protrusion 11 are manufactured from titanium or stainless steel. An example of the manufacturing method is the third
As shown in the figure, the protrusions 11 are formed on the plate by rolling using forming rolls at a predetermined inclination angle
After T-forming, this plate material is formed into a tube shape.

In order to obtain the characteristics of the heat exchanger tube according to the present invention constructed as described above, pressure loss and heat transfer coefficient were measured, and the results were as follows.

In other words, the pressure loss is 0.5 to 4.0 m4
The heat transfer coefficient is obtained by changing the flow rate and heat load, and the heat transfer tube of the present invention is obtained by changing the pressure loss and heat transfer coefficient, and the pressure loss is kept constant based on the measurement results of the heat transfer coefficient. The characteristic value of was calculated.

In Figure 4, the pitch pt between the protrusions 11 is 12.5 mm.
.

It is a graph showing the relationship between the heat transfer coefficient and the inclination angle θ of the protrusion 11 when the flow velocity of the fluid in the pipe is fixed at 2.0 m/s. In this graph, the vertical axis shows the pump power (pressure loss) and the ratio of the heat transfer coefficient α' of the heat transfer tube of the present invention to the heat transfer coefficient αB of the smooth tube under the constraint condition of constant heat load (heat transfer The coefficient ratio) αA8 is taken, and the horizontal axis is the inclination angle θ of the protrusion 11.

As is clear from FIG. 4, when the height e of the upright surface 11a of the protrusion 11 is 0, 2 to 0, 7 mm and the inclination angle θ is 40 to 90 degrees, the heat transfer coefficient is excellent. This shows that. As the height e of the upright surface 11a increases, the heat transfer coefficient ratio α' 6 increases;
It shows the highest value when the height e is about 0.5 mm,
The maximum value was 1.58 when the inclination angle θ was around 60'. Furthermore, as the height e of the upright surface 11a increased, the heat transfer coefficient ratio α'A1B actually decreased. Therefore, the upright surface 1
The height of 1 m is preferably 0.2 to 0.7 mm, and the inclination angle θ is preferably 40 to 90 degrees.

Next, the relationship between the ratio Pt/e of the pitch pt of the protrusions 11 and the height e of the upright surface 11a and the heat transfer coefficient ratio Cl'/(Lm is shown in FIG. 5. In the graph,
The vertical axis represents the heat transfer coefficient ratio α'/(im, and the horizontal axis represents the inclination angle θ.

As is clear from FIG. 5, excellent heat transfer performance is exhibited when the value of Pt/e is between + and 90° and the inclination angle θ is between 90° and 90°. That is, as Pt/e increases, the heat transfer coefficient ratio α/ds increases, reaching a maximum value when the value of Pt/e is around 40, and a maximum value of 1.58 when the inclination angle θ is ω0. Furthermore, as the value of Pt/e increases, the heat transfer coefficient ratio α7αB gradually decreases. Therefore, the protrusion 11
The pitch pt along the pipe axis is the height e of the standing surface 11m.
It is preferable that the amount be increased to (equity) times.

Now, the height e of the upright surface 11a is 0.3 mm, and the protrusion 1
1 pitch pt of 12.5 mm, inclination angle θ 55
The heat exchanger tube of the present invention configured as ゜ is used in a heat exchanger,
Cooling water flows inside the pipe and condenses water vapor that exists outside the pipe.
The result used in the case of liquefaction is the heat transfer coefficient ratio α′/α
An S value of 1.58 was obtained.

Further, in the heat transfer tube of the present invention in which the height of the upright surface 11a is 0.5 mm, the pitch pt between the protrusions 11 is 12.5 mm, and the inclination angle is ω0, the heat transfer coefficient ratio α7αB is It was 1.43.

〔Effect of the invention〕

Therefore, the present invention provides an upright surface that stands up perpendicularly from the inner peripheral surface of the tube body on the upstream side in the flow direction of the fluid in the tube, and a raised surface that extends vertically from the upper end of the upright surface along the flow direction on the downstream side. A plurality of protrusions with gently descending slopes are arranged at a required pitch and are inclined with respect to the tube axis of the tube body, making it possible to achieve high heat transfer coefficient and low pressure loss. It has the following effects.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a heat exchanger tube according to the present invention, FIG. 2 is a longitudinal cross-sectional view along the tube axis, and FIG. 3 is a perspective view showing the protrusions in a rolled state before pipe formation. FIGS. 4 and 5 are graphs showing the results of the performance test. DESCRIPTION OF SYMBOLS 10... Pipe body, 11... Projection, lla... Upright surface, llb... Inclined surface. Representative Patent Attorney Kensuke Chika (and 1 other person) No. 1!
@Figure 2 Figure 43

Claims (1)

[Claims] 1. g On the inner circumferential surface of the main body, on the upstream side in the flow direction of the fluid in the tube, there is an upright surface that stands up perpendicularly from the inner circumferential surface of the tube body, and on the downstream side, there is a raised surface that stands up vertically from the upper end of the upright surface in the flow direction. A heat exchanger tube characterized in that a plurality of protrusions having sloped surfaces gently descending along the ridges are inclined with respect to the U-axis of the tube body and are formed at a required pitch. 2. The transmission fA tube according to claim 1, wherein the protrusion has an upright surface diameter of 0.2 to 0.7 mm. 3. The heat exchanger tube according to claim 1 or 2, wherein the protrusions are inclined at an angle of 40 to 90' with respect to the tube axis. 4. The pitch between the protrusions along w: m is 2 of the height of the upright surface.
The heat exchanger tube according to any one of claims 1 to 3, which is 0 to 80 times larger.