CZ201777A3 - An annular heat exchanger - Google Patents

Abstract

An annular heat exchanger comprising at least two circumferentially closed and fluidly arranged tubular profiles (1, 2) in which a heat conducting structure (3) is arranged. The heat conducting structure (3) comprises a spirally tightly wound pair of superimposed strips (4, 5), the first strip (4) being smooth while the second strip (5) is corrugated transversely to the coiling direction to form flow channels (6).

Description

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The invention relates to an annular heat exchanger comprising at least two circumferentially closed and arranged tubular profiles for the flow of media in which a heat conducting structure is arranged.

BACKGROUND OF THE INVENTION

Heat exchangers, including at least two tubes for the flow of media, are sometimes referred to as "tube-in-tube" exchangers. The tube in the tube-in-tube exchangers has two main functions - it separates the media and also serves as a heat exchange surface. Heat transfer from the medium to the heat exchanger material is decisive for heat exchange;

Increasing the heat exchange surface will increase the heat exchanger performance. For tube-to-tube exchangers, the length of the tubes needs to be increased to increase the heat exchange surface. Since the tube also separates the media, the entire heat transfer surface must have a wall thickness such that it can withstand the pressures of the media and their differential pressure. This results in a very large weight (and dimensions) of such exchangers.

The heat exchange surface can be increased by ribbing. The ribs are part of the pipe and have a thickness of the order of mm. In this case, both heat transfer and heat conduction are partially applied, but heat transfer is still critical.

Ribs (heat exchange area increase) are used on one side - inside or outside.

In order to achieve maximum performance with a minimum exchanger weight, there is an effort to reduce the thickness of the media separating wall, which encounters technological limits, especially when media are of different or high pressures. Moreover, it is necessary to connect these thin walls in some way.

soldering or welding. This also runs into certain technological limits.

A tube for heat exchangers filled with a heat exchange surface in the form of ribs is known, for example, from U.S. Pat.

Furthermore, heat exchangers filled with a honeycomb-like structure are known.

For example, Japanese documents JPHD2150691

62288495.

Furthermore, rotary regenerative heat exchangers are known, for example KASTT, which operate on the capacitor principle, i.e., they are cyclically charged and then discharged after the charged portion of the heat exchange surface is turned to a lower temperature location. This is technically a completely different way of working with the exchanger than the tube-in-tube exchangers.

It is an object of the present invention to provide known tube-in-tube exchangers in such a way as to achieve a significant reduction in weight and an increase in heat exchanger performance.

SUMMARY OF THE INVENTION This object is achieved by an annular heat exchanger comprising at least two circumferentially enclosed and arranged tubular profiles for the flow of media in which a heat conducting structure is arranged according to the invention, characterized in that the heat conducting structure comprises a spirally tightly coiled pair the first strips are smooth, while the second strips are undulated transversely to the direction of winding to form flow channels.

An advantage of the solution according to the invention is that in the exchanger according to the invention, the individual heat-conducting structures are separated from each other by respective tubular profiles, which in standard exchangers function as heat exchange surfaces, but in the exchanger 38 according to the invention predominantly function as a media separator. The tubular profiles do not primarily form the heat exchange surface, but the exchanger member that separates the media, so that the tubular profiles can be sized for the respective pressure difference and the exchanger according to the invention can then be used for almost any pressure differential of the media.

Since the heat conducting structure can have a thickness of tens of micrometers regardless of the media pressures, the thickness of the wall and the possible fins in the finned tubes of known heat exchangers is in the order of millimeters, ie 2 orders of magnitude stronger. lower.

X

The tubular profiles may have substantially any cross-section, in particular circular, oval or angular.

It is preferred that the heat conducting structure completely fills the tubular profiles.

Explained £ (Ptehted-Images) »

FIG. 1 is a schematic cross-sectional view of a first embodiment of an annular heat exchanger according to the invention. Fig. 2 shows a detail of an embodiment Jq of the heat conducting structure in the region of the inner profile. Figures 3, 4, 5 and 6 show further embodiments of an annular heat exchanger according to the invention.

EXAMPLES ⁴ in FIG

The exemplary embodiment of the annular heat exchanger of FIG. 1 comprises three concentrically arranged tubular flow profiles having an outer profile 1, an inner profile 2 and a center profile 7. In this embodiment, the tubular profiles 1, 2, 7 are formed by tubes with a circular cross-section. The interstices between these profiles 1, 2, 7 are completely filled with a heat-conducting structure 3, which is formed by a spirally tightly coiled pair of superimposed strips 4, 5 of 0.05 mm aluminum sheet. The first strip 4 is smooth, while the second strip 5 is undulated transversely to the winding direction to form flow channels 6 (see FIG. 2).

The embodiment of the annular heat exchanger of FIG. 3 differs from the embodiment of -X of FIG.

Conversely, the exemplary embodiment of the annular heat exchanger of FIG. 4 includes several center profiles 7. In such a case, the media may be two or the heat exchanger may be designed to exchange heat between multiple media.

Figures 5 and 6 show examples of exchangers whose tubular profiles 1, 2 have a rectangular cross-section. It will be apparent to those skilled in the art that the profiles 1, 2, 7 may have substantially any circumferentially closed cross-section.

The annular heat exchanger according to the invention can be connected upstream or co-current with any number of intermediate profiles 1, 2, 7. The exchanger can also be used for liquid / liquid media, but its advantages are most evident when used for gas / gas and gas / media. liquid and in applications with a large pressure difference on the hot and cold side (steam generators, combustion turbine recuperators, condensers, evaporators).

X.

The operation of the annular heat exchanger according to the invention will be described with reference to the exemplary embodiment according to FIGS. 1 and 2. The other embodiments function analogously.

The warm medium is supplied to the space between the inner profile 2 and the center profile 7, where the medium transfers heat to the heat conducting structure 3. The heat conducting structure 3 leads this heat to the tube forming the inner profile 2 and subsequently heats to the heat conducting structure 3 between the inner profile 2 and the outer profile 1. In this space, the heat conducting structure 3 then transfers heat to the colder medium flowing in this space. The movement of heat is indicated by arrows in FIG.

The annular heat exchanger according to the invention is therefore based on a combined heat exchange, where the heat transfer has the same weight as the heat conduction. The heat transfer surface is maximized therein by inserting the heat-conducting structure 3 described above. To exchange heat to the same extent, it utilizes heat transfer to the heat-conducting structure 3, then conducting heat through the heat-conducting structure 3 to the separating wall heat conduction 3, which is in the exchanger according to ·

Of the invention as important as heat transfer.

The individual heat-conducting structures 3 are separated from one another by respective tubular profiles 1, 2, 7, which in standard exchangers function as heat exchange surfaces, but in the exchanger according to the invention, however, they mainly function as media separators.

By separating the tubular profiles 1, 2, 7, which are dimensioned for the respective pressure difference, the exchanger according to the invention can be used for almost any pressure difference of the media. Thus, the tubular profiles 1, 2, 7 do not primarily form a heat exchange surface, but a heat exchanger member separating the media. Since the heat conducting structure may have a thickness of tens of micrometers regardless of the media pressures, while the wall thickness and possible fins in the finned tubes of known heat exchangers are in the order of millimeters, ie 2 orders of magnitude stronger, performance of the order of magnitude lower.

X

The comparative calculation using the numerical model in the ANSYS CFD program compared the heat output transferred by a 50 mm aluminum tube with a diameter of 20 mm in four versions, simulating 4 different types of exchangers:

- smooth pipe

standard finned tube (3) (30) ribbed tube according to patent U heat exchanger according to the invention ° C heated tube,

Calculation conditions: from the outside to a constant temperature of 10 Xs, which enters air with a temperature of 20fC and a flow rate of 31.87 m / s.

The ideal heat exchanger with 100% efficiency would have an output of 604 W. Using the numerical model, the following values were calculated:

Smooth tube - 32 W (5% ideal heat exchanger)

Standard finned tube - 146 W (24% ideal heat exchanger)

Pipe with ribs according to patent U ^ 53á | p30 - 252 W (42% ideal heat exchanger)

Heat exchanger according to the invention - 375 W (62% ideal heat exchanger)

It is clear from the above that the exchanger according to the invention clearly has the highest performance.

X List of reference numbers outer profile inner profile heat conducting structure first strip second strip flow channel center profile

Claims (3)

An annular heat exchanger, comprising at least two circumferentially closed and arranged tubular profiles (1, 2) for the flow of media in which a heat conducting structure (3) is arranged, characterized in that the heat conducting structure (3) comprises a spirally tightly coiled a pair of superimposed belts (4, 5), wherein the first strip (4) is smooth, while the second strip (5) is undulated transversely to the winding direction to form flow channels (6). An annular heat exchanger according to claim 1, characterized in that the tubular profiles (1, 2) have a circular, oval or angular cross-section. An annular heat exchanger according to claim 1 or 2, characterized in that the heat conducting structure (3) completely fills the tubular profiles (1, 2). PRINTING 1/3