RU2799161C1 - Heat exchanger - Google Patents

Abstract

FIELD: heat engineering.

SUBSTANCE: invention relates to heat exchangers and can be used in processes in various industries, agriculture and public utilities. The heat exchanger consists of outer and inner tubes having an inlet and outlet of the outer tube, as well as an inlet and outlet of the inner tube, and flanges for connecting additional sections. In this case, the inner tube and the outer tube have helical grooves with the same pitch and depth of the groove, and the helical groove of the inner tube is oppositely directed to the helical groove of the outer tube. It is also possible to connect additional sections to the heat exchanger.

EFFECT: intensification of heat transfer by increasing the heat transfer coefficient.

1 cl, 4 dwg

Description

The invention relates to the field of heat engineering, namely to heat exchangers and can be used in technological processes in various industries, agriculture and utilities.

Known screw heat exchanger [RU 2415363, F28D 1/04, F28F 9/22]. The screw heat exchanger contains tube boards, heat exchange tubes removable from both sides of the cover, contains bundles with a staggered arrangement of tubes for the first heat carrier, located diametrically in a circle around the central pipe supplying this heat carrier and a screw plate directing the movement of the second heat carrier transversely to these tubes.

The disadvantages are the complexity of the design and the need to take into account the movement of the tube sheets during the operation of the heat exchanger.

A heat exchanger pipe is known [RU 2200925, F28F 1/00], containing fins in the form of a wire spring wound in a spiral, the fins being located on the outer and inner surfaces of the pipe, the fins on the inner surface of the pipe are made of a spiral located on the frame. According to the invention, the finning on the inner surface of the pipe is made in the form of a double helix, placed on a frame, which is a twisted double wire, the diameter of the finned wire is selected in the range of 0.3-1.0 mm, the spring pitch is selected in the range of 2-6 mm of wire diameters , and the outer winding spiral pitch is selected from 1 to 2 spring diameters.

The disadvantages of this solution are as follows: design complexity
due to the presence of an additional element in the form of a wire spring; does not provide uniform heat removal along the annulus flow
due to a decrease in the driving force between heat exchange media; to protect the elements of the heat exchanger from overheating, it requires the flow of a cooling medium, which significantly increases operating costs.

The closest in technical essence and technical essence is a pipe-in-pipe heat exchanger [EN 2502931, F28F1/42].

A tube-in-pipe heat exchanger with screw inserts installed in the inner tube and annular space, characterized in that the inner space of the inner tube and the annular space between the inner and outer tubes are helical cavities formed by the pipe walls and screw inserts installed in such a way that the inner screw insert is connected, preferably by welding or soldering, to the inner surface of the inner pipe, the screw insert in the annular space is connected in the same way to the outer surface of the inner pipe and to the inner surface of the outer pipe, and the materials of the inner pipe, screw inserts and the joints of the screw inserts with the walls of the inner pipe must have a minimum thermal resistance, the flows of media (liquid or gaseous) in the inner pipe and in the annulus flow through helical spirals.

The disadvantage of the proposed analogue is the complexity of manufacturing structures. In particular, the inner screw insert is connected to the inner surface of the inner pipe by welding or soldering, the screw insert in the annulus is connected to the outer surface of the inner pipe and to the inner surface of the outer pipe also by welding or soldering. In addition, the disadvantage of such heat exchangers is a slight increase in turbulence with a faster increase in hydraulic resistance. A large contact thermal resistance deprives the turbulent insert of its essential function - to transfer heat from it to the wall of the inner pipe due to thermal conductivity.

Increasing the efficiency of heat transfer makes it possible to reduce the required heat exchange area, reduce the length of the heat exchanger, its other dimensions and weight. But an increase in the speed of media in pipes requires an increase in the power of pumps that pump these fluids. If we take into account that the increase in turbulence is proportional to the speed of the medium, and the required pump power is proportional to the speed of the flow, then it is obvious that the increase in the speeds of the media has a certain limit, after reaching which a further increase in speeds becomes unprofitable.

The objective of the invention is to intensify heat transfer by increasing the heat transfer coefficient.

The problem is solved due to the fact that the heat exchanger with helical tubes transfers heat from the heat carrier moving along the inner helical tube to the heat carrier moving in the annulus. The pitch and depth of the helical grooves on the outer and inner tubes are the same for their equal thermal expansion and elimination of thermal deformations, and the direction of knurling of the helical grooves is different to increase the turbulence of fluid movement in the annular space and increase the heat transfer coefficient.

New significant features:

- the pitch and depth of the helical grooves on the outer and inner tubes is the same for their uniform thermal expansion and elimination of thermal deformations;

- the direction of knurling of the helical grooves of the outer and inner tubes is different to increase the turbulence of fluid movement in the annulus.

The listed new essential features, together with the known ones, are necessary and sufficient to achieve a technical result in all cases covered by the requested scope of legal protection.

Technical result

The technical result consists in the intensification of heat transfer by increasing the turbulence of fluid movement. Thermal expansion is taken into account in the design.

The essence of the invention is illustrated in the drawings, where:

- in Fig.1. the outer tube of the heat exchanger is shown;

- in Fig.2. inner tube of the heat exchanger;

- Fig.3. a section assembled from the proposed heat exchangers is presented;

- fig. 4 experimental data on changes in the temperature difference along the length of the heat exchanger when it is operated in the direct-flow mode.

The heat exchanger contains an outer tube 1 (Fig. 1) with a helical groove along the outer surface, which is the body; inner tube 2 (Fig. 2) with a helical groove opposite to the helical groove of the outer tube 1; connecting pipes: outlet 4 outer tube 1, inlet 6 inner tube 2, outlet 8 inner tube 2, inlet 10 outer tube 1 with flanges: flange inlet 3 outer tube 1, outlet flange 5 outer tube 1, flange the inlet pipe 7 of the inner tube 2, the flange of the outlet pipe 9 of the inner tube 2; inlet pipe 10 of the outer tube 1 with the flange of the inlet pipe 3 of the outer tube 1; outlet pipe 4 with the flange of the outlet pipe 5 of the outer tube 1; the inlet 6 of the inner tube 2 with the flange of the inlet 7 of the inner tube 2; the outlet 8 of the inner tube 2 with the flange of the outlet 9 of the inner tube 2; through the flange of the inlet pipe 7 and the flange of the outlet pipe 9 of the inner tube 2, it is possible to connect additional sections through the cable 11.

The heat exchanger works as follows.

The first heating coolant II (Fig. 2) enters the inlet pipe 10 of the outer tube 1 and passes into the annular space of the blue arrow section, moves along the helical outer tube 1 and the helical inner tube 2 and acquires turbulent motion due to the peculiarities of winding helical grooves, which increases the Reynolds number and, as a result, improves the heat transfer coefficient and heat transfer in general, then exits through the outlet 4 of the outer tube 1 with a different temperature. The second heated coolant I (Fig. 2) through the inlet pipe 6 enters the cavity of the inner tube 2, moves along the heat exchange surface in a spiral, the red arrow due to the profile of the helical groove, exits through the outlet pipe 8 of the inner tube 2 with a different temperature. Moreover, the first coolant can be heated, and the second coolant can be heating. If necessary, one or more heat exchangers can be connected to the heat exchanger through the cable 11, forming a multi-section heat exchanger (Fig. 3).

Compensation for thermal expansion of the outer 1 and inner 2 tubes is achieved by the same pitch and depth of helical groove winding. An increase in the heat transfer coefficient and, as a consequence, a decrease in metal consumption is provided by reducing the required heat exchange surface.

In FIG. 4 shows the experimental data on the change in the current temperature difference in the case of the heat exchanger operating in the once-through mode. Studies of the operation of heat exchangers have shown that the helical groove on the tubes of a shell-and-tube heat exchanger not only increases the heat exchange surface area by about 40%, but also the heat transfer coefficient by 30-35%. This occurs due to flow turbulence and an increase in the Reynolds number, which in turn increases the heat transfer coefficients and, as a result, leads to an increase in the efficiency of the entire heat exchanger as a whole.

Thus, the creation of a helical groove on the tubes of a shell-and-tube heat exchanger is a simple and effective means of increasing the efficiency of heat exchangers.

The invention makes it possible, by reducing the required heat exchange surface, to increase the heat transfer coefficient and, as a consequence, to reduce the metal consumption of the heat exchanger.

Claims (1)

A heat exchanger consisting of outer and inner tubes having an inlet and outlet pipe of the outer tube, as well as an inlet and outlet pipe of the inner tube, flanges for connecting additional sections, characterized in that the inner and outer tubes have helical grooves with the same groove pitch and depth, moreover the helical groove of the inner tube is oppositely directed to the helical groove of the outer tube, while it is possible to connect several sections to the heat exchanger using a cable.

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