SU1760300A1 - Heat exchange tube - Google Patents

Abstract

Use: heat exchanger elements in the chemical and energy industries. SUMMARY OF THE INVENTION: The heat exchange tube has transverse cavities on the outer surface and corresponding protrusions on the inner surface. The protrusions and depressions have a profile of a section of an ellipse, the major axis 7 of which is inclined to the axis of the pipe at an angle of 5-30 °, the ratio of the axes of the ellipse is from 1: 1.15 to 1: 4, and the depth of the depression is 0.020-0.035 outer diameter of the pipe. 3 il.

Description

The invention relates to heat exchange elements and can be used in the chemical, energy industry and other engineering fields related to the production and operation of heat exchange equipment.

In order to create efficient heat exchanging devices, heat transfer intensification is necessary. The most realistic and affordable way to intensify heat transfer in pipes is an artificial disruption of the laminar flow layer near the pipe wall.

A heat transfer tube is known with annular depressions along the outer surface and corresponding protrusions on the inner surface, having a height of 1.25-2.5 times less than the depth of the depressions.

The disadvantage of the described construction is that with an external longitudinal flow, the flow of heat transfer fluid in the depression zone is sharply turbulized, which causes the advance growth of aerohydrodynamic resistance, and with the flow of heat transfer fluid inside the pipe, the flow becomes turbulent with a protrusion, and behind the ledge there are stagnant zones due to discharge pipe walls, which contributes to the deposition of contaminants on the internal wall of the pipe, which reduces the efficiency of use of this pipe.

A heat exchanger tube is known that contains grooves on the outer and inner surfaces, each groove being connected to a corresponding smooth section of the pipe by a straight segment located to the longitudinal axis of the pipe with a slope of at least 2: 1 on the outer groove 1: 2.

A disadvantage of the known heat exchange tube is that when the working medium passes, the near-wall layers of the tube due to the protrusions are turbulized and open from the surface of the tube, forming stagnant zones in the grooves in which conditions are created for the deposition of contaminants. Availability

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protrusions also contribute to faster growth of aero-hydrodynamic resistance. In addition, the known heat exchange tube is low-tech for mass production due to the increase and decrease in the diameters of the mating areas relative to the original tube size, which requires several different manufacturing operations.

With the passage of heat carrier flow in the opposite direction, as indicated in the description of the invention, the aero-hydraulic expansion increases even more.

The aim of the invention is to intensify heat exchange by creating a vortex structure of the flow of heat-transfer fluid, reducing the deposits of contaminants on the pipe walls and improving the manufacturability of the heat-exchange tube.

The goal is achieved by the fact that in a heat exchange pipe with transverse depressions on the outer surface and corresponding protrusions on the inner surface of the pipe, the depressions and protrusions are made in axial section in the form of an elliptical profile with a ratio of the minor and major axes from 1: 1.5 to 1: 4, and the angles of inclination of the major axis to the axis of the pipe are from 5 to 30 °, while the depth of the groove is 0.020 - 0.035 of the outer diameter of the pipe.

FIG. 1 shows a heat exchange tube; in fig. 2 — node I in FIG. one.

The heat exchange tube 1 contains transverse depressions 1 on the outer surface 3 and the corresponding transverse protrusions 4 on the inner surface of the pipe 5, and transverse depressions 2 and protrusions 4 are made of an elliptical profile with a ratio of small b large 7 axes from 1: 1.5 to 1: 4 , the angle of inclination of the major axis of the ellipse to the axis of the pipe 8 is from 5 to 30 °, and the depth of the groove is 0.025-0.035 of the outer diameter of the pipe.

In this case, the positive effect is greatest with a smaller ratio of the axes of the ellipse and with a smaller angle of inclination of the larger axis with a larger ratio of the axes of the ellipse with a larger angle of inclination of the major axis.

With a smaller angle of inclination of the major axis and a larger ratio of the axes, the pipe surface decreases, which negatively affects the convective component. With a smaller ratio of axes and a larger angle of inclination of the major axis, turbulence and the formation of stagnant zones increase, which reduces thermal efficiency and increases aero-hydrodynamic resistance.

The operation of the heat exchange pipe is considered with the following combinations of coolants:

external surface — gas, internal — liquid (water economizers, steam superheaters, etc.);

internal surface - gas, external liquid (flame tubes of gas-tube boilers);

0 external and internal surface of the pipe - gas (air heaters).

When the flow of the coolant flow around the working medium, entering the transverse depressions 2, twists, about 5 times a tornado vortex along the entire length of depressions 2, and due to a smoother exit, the vortex leaves the depressions 2 without detachment from the wall of pipe 1, a continuous vortex structure on the surface pipes 1,

0 In the case of the in-line flow of the heat carrier gas, the working medium, meeting the protrusion 4, is turbulent and, due to the smooth transition from the protrusion 4 to the smooth part of the pipe 1, the flow does not come off

5 from the wall of the pipe 1, ensuring full utilization of the wall of the pipe 1 for heat transfer.

With two-way flow of gaseous media, the overall efficiency of the profiles of each side is used.

The use of the proposed design of the heat exchange tube allows to expand the range of its application (screen surfaces, water economizers,

5 tubes of gas-tube boilers and other surfaces of the boiler units), reduce the temperature pressure of the surfaces by increasing heat transfer, reduce the formation of deposits of contaminants from the stream

0 heat carrier, reduce the metal intensity of the heat exchanging equipment with high manufacturability.

The profile of the proposed heat exchange tube is obtained by the method of transversely-winded rolling in one pass, while in the manufacturing process it is possible to adjust the depth of the depression and, accordingly, the size of the protrusion, which allows you to adjust the intensity of heat exchange.

The cost of the profile pipe increases against the smooth by 1.3-1.5 kopecks. by 1 l.m. that with a decrease in the metal intensity of the heat exchanger 1.3-1.5 times does not affect the cost of manufacture of the equipment and gives

5 positive effect

As a result of bench studies, an increase in heat transfer along the inner and outer surfaces up to 2-2.5 times as compared with a smooth-wall pipe was obtained.

The results of a portion of the experimental data of the inventive pipe are presented in the accompanying drawing of FIG. 3, where the depth of the depression in the pipes 1,2,3, respectively, 0,7; 0.1; 1.5 mm.

Claims (1)

The invention of the heat exchange pipe with transverse depressions asymmetric profile on the outer surface and the corresponding 0 They have transverse protrusions on the inner surface, characterized in that, in order to intensify heat exchange, the depressions have a profile in the form of an ellipse section, whose major axis is inclined to the pipe axis at an angle of 5-30 °, the ratio of the ellipse axes is from 1: 1 , 5 to 1: 4, and the depth of the depression is 0.020-0.035 outer diameter of the pipe. Phie.1 j b fig g jf Ј j j; gl sf-i 4J hl J h i “W l -jfv-) CM CvjX-V-V. V CSfOQ C.-Ua Wrj f -tvfN 4 ..-. I