RU2844670C1 - Toroidal tubular heat exchanger - Google Patents

Abstract

FIELD: heat engineering.

SUBSTANCE: invention relates to heat engineering and can be used in various axisymmetric devices, such as gas turbine engines and power plants, one of heat carriers can be incoming air flow. Other heat carrier passes through multiple family of tubes with the specified total flow area and length to provide the required heat exchange. Device design is built on the basis of one simplest element – flat section of a group of tubes and end elements in the form of rings for large and small diameters of matrix, which finally forms groups of spiral-like channels around longitudinal axis of matrix in volume of toroidal heat exchanger. Length of spiral-like channels exceeds by many times longitudinal size of heat exchanger. At one step of the spiral-like channels they make a full turn about the axis of the matrix, at that the radial dimension from the axis of the spiral matrix of tubes alternately varies between large and small diameters of the matrix in its successive layers.

EFFECT: improving heat exchange efficiency.

12 cl, 9 dwg

Description

The invention relates to the field of heat engineering and can be used as part of various axisymmetric devices, such as gas turbine engines and power plants.

A plate-type heat exchanger is known (European application No. 0434553, 1990), which contains a package of thin rectangular plates installed in a housing, the plates are permanently connected to each other by soldering along the perimeter of the plates and the perimeter of the holes for alternate separate supply of heat carriers between the plates. At operating pressure in the heat exchanger, forces act on the edges of the connected plates, splitting the soldered or welded joint. During operation for a specified service life, fatigue cracking develops from splitting forces near the welding or soldering with depressurization of the cavities of the heat exchanger. Therefore, the entire plate package is additionally placed in a power housing so that the package does not increase in size when pressure is applied. In this case, the mass and dimensions of the heat exchanger increase. In addition, rectangular "suitcase"-shaped plate heat exchanger blocks are difficult to place in axisymmetric structures, such as in space-based nuclear power plants. A cylindrical housing is preferable, as it can withstand the operating pressure of coolants with minimal weight.

An axisymmetric cooling system for a multi-circuit gas turbine unit is known (RU 2680636), containing a multi-section annular recuperative heat exchanger placed in the cooling air flow of the flow part of the second circuit of the gas turbine unit and consisting of mechanically interconnected unitary sections, each representing a bundle of hollow tubular heat exchange elements. The design of such a heat exchanger does not provide a sufficiently high reliability in the operating range of thermal modes, since thermal movements of tubular heat exchange elements of complex spatial configuration lead to the appearance of defects (cracks) and to direct losses of the working fluid.

A tubular heat exchanger is known (RU 2727105), in which the heat exchanger matrix is an axisymmetric structure of tubes grouped into flat sections, where each section consists of several tubes and two end elements in the form of rings into which the ends of the tubes extend, the sections are laid in layers in planes perpendicular to the matrix axis with the end elements aligned and connected through openings in the end elements to each other so that they form axial channels parallel to the matrix axis. Despite all the increased maintainability, the design does not ensure the reliability of the heat exchanger, especially in cyclic modes with significant heating, affecting the tightening force of the flat sections of the heat exchanger.

A tubular heat exchanger (RU 2699851), adopted as a prototype, is known, containing a toroidal body, devices for supplying and removing heat carriers and a heat exchanger matrix, which is made monolithic without welded or soldered joints and is an axisymmetric structure of tubes laid in layers in planes perpendicular to the axis of the matrix, wherein the tubes located in adjacent layers intersect, and the ends of the tubes are connected to end elements that form longitudinal channels parallel to the axis of the matrix.

The disadvantage of this heat exchanger is its low efficiency, since heat exchange between the medium entering the tubes and the medium in the intertube space occurs over a short length equal to the length of the tube between the axial channels assembled from end elements located on the large and small diameters of the toroidal matrix. In addition, the heat exchange process may be unstable in terms of coolant flow when it is heated in a system of numerous parallel tubular channels.

The technical result of using the claimed invention is an increase in the efficiency of heat exchange.

The specified technical result is achieved in that the toroidal tubular heat exchanger contains a toroidal matrix formed from layers of flat sections perpendicular to the matrix axis, each consisting of several tubes and two end elements in the form of rings located on the large and small diameters of the matrix, characterized in that inside the toroidal matrix around the longitudinal axis, spiral-like channels are formed from tubes grouped by flat sections, with an alternating change in the radial size of the spiral between the large and small diameters of the matrix in successive layers of the matrix, wherein the number of groups of spiral-like channels is equal to the number of flat sections in the matrix layer.

Groups of spiral-shaped channels are formed by placing plugs on the end elements of flat sections of the outer layers of the matrix and between even and odd layers of the matrix on a small (or large) diameter of the matrix and, accordingly, on a large (or small) diameter of the matrix, plugs on the end elements of flat sections between odd and even layers of the matrix.

Ring collectors are installed on the end elements of the flat sections of the outer layers of the matrix, respectively, on the large (or small) diameter of the matrix.

Between the adjacent even and odd (or odd and even) layers of the matrix, a ring-shaped pass-through collector is installed, respectively, on the large (or small) diameter of the matrix.

The plugs on the end elements of the flat sections of one matrix layer are made in the form of a common ring corresponding to the large (or small) diameter of the matrix.

The matrix layer can be formed from flat sections with the end elements located in adjacent angular sectors of the matrix layer (type A), while the spiral pitch is equal to

The matrix layer can be formed from flat sections with the end elements arranged through one adjacent angular sector of the matrix layer (type B), while the spiral pitch is equal to

where t is the pitch of the spiral of spiral-like channels; δ is the thickness of the end element of the flat section; n is the number of groups of spiral-like channels in the matrix, equal to the number of flat sections in the matrix layer.

The tubes of flat sections can be made straight.

Flat sections can be made monolithic with plugs in the form of a set of flat sections with different corresponding placement of plugs on the end elements.

The matrix layers can be made monolithic in the form of a set of layers with different corresponding placement of the component parts.

The matrix can be placed in a toroidal housing and the coolant with high pressure is connected to the tubes of the spiral-shaped channels, and with lower pressure - to the inter-tube volume of the housing.

Groups of spiral-shaped channels, each or several, can be connected to different heat carriers.

The heat exchanger is a structure somewhat reminiscent of a multi-start thread: the number of thread starts is equal to the number of flat sections in the matrix layer; the thread starts start from the end elements, for example, located on the large diameter of the matrix of the outer layer of the matrix; the thread depth varies between the radii of the end elements relative to the longitudinal axis of the matrix, located alternately on the large and small radii of the matrix; the thread pitch is determined between two points of one spiral-like channel lying on a longitudinal line along the matrix axis. The external coolant occupies the volume of the heat exchanger on the outside of a plurality of tubes of flat sections located in successive layers of the matrix.

The formed groups of spiral-like channels in the heat exchanger matrix provide a multiple increase in heat exchange efficiency through an increase in the heat exchange surface area, since the length of the spiral-like channels is many times greater than that known in the prototype, where it is equal to the surface area of the group of tubes of only one flat section with a single passage of the coolant between the end elements on the large and small diameters.

The conditions of the required heat exchange determine the length of the spiral-shaped channels, proportional to the number of matrix layers, and the flow section, equal to the sum of the cross-sectional areas of all the tubes of all the flat sections located in the matrix layer.

The installation of intermediate ring collectors ensures mixing of the internal heat carrier, preventing possible uneven flow through different heat exchanger tubes.

The use of a toroidal body allows for the circulation of two different heat carriers. At the same time, the direction of the heat carrier with high pressure through the tubes of spiral-shaped channels allows for their partial unloading by the back pressure of the heat carrier in the inter-tube volume and the use of tubes with a thinner wall thickness. In turn, this fact additionally increases the efficiency of heat exchange between the heat carriers and, in addition, reduces the total mass of the heat exchanger.

Groups of spiral-shaped channels, each individually or several pieces, can be connected to different heat carriers, which allows using a heat carrier for tubes from areas with different pressures and even using several different heat carriers.

With close values of the large and small diameters of the matrix with an increase in the number of flat sections in the matrix layer, the tubes of spiral-like channels can be made rectilinear in the delivered state without bending them before welding as part of flat sections. This significantly simplifies the matrix assembly technology and generally increases the overall reliability of the device.

The implementation of matrix layers from flat sections in the form of a set of monolithic sections (right, left, collector, etc.) and, even more so, the implementation of the matrix in the form of a set of monolithic layers (right, left, collector, etc.) significantly simplifies the assembly of the heat exchanger.

The essence of the invention is explained by the drawings:

Fig. 1 - diagram of a toroidal tubular heat exchanger;

Fig. 2 - fragment of a heat exchanger - a flat section from a group of tubes and end elements for large and small matrix diameters;

Fig. 3 - diagrams of one channel of a heat exchanger of type A at different n;

Fig. 4 - diagrams of one channel of a type B heat exchanger for different n;

Fig. 5 - conventional transverse diagram of a heat exchanger of type B with n=8, t _B - 4 δ;

Fig. 6 - conventional longitudinal diagram of a heat exchanger of type B at n=8, t=4 δ;

Fig. 7 - transverse diagram of a heat exchanger of type B with straight tubes of flat sections at n=32, t _B =16 δ;

Fig. 8 - diagram of one channel of a heat exchanger of type B with straight tubes of flat sections at n=32, t _B =16 δ,

Fig. 9 - schematic layout of the gas turbine power plant recuperator.

On the figures, the designations of numbers with footnotes, letters and numbers without footnotes are accepted:

1 - toroidal heat exchanger body,

2 - external coolant inlet pipe,

3 - outlet pipe of external coolant,

4 - inlet pipe of the internal coolant,

5 - inlet ring collector of the internal coolant,

6 - outlet pipe of the internal coolant,

7 - outlet ring collector of the internal coolant,

8 - axisymmetric matrix,

9 - group of flat section tubes,

10 - end element of flat section for large matrix diameter,

11 - end element of flat section for small matrix diameter,

12 - annular flow-through collector,

n is the number of groups of spiral-shaped channels in the matrix, equal to the number of flat sections in the matrix layer,

Δ - thickness of the toroidal spiral of the spiral-shaped channel,

t - pitch of the spiral channel,

D - large matrix diameter,

d - small diameter of the matrix,

δ - thickness of the end element of the flat section,

F - diameter of the end element of the flat section,

2 m - total number of layers in the heat exchanger matrix,

A, B, C, D, E, G, I - designation of end elements on the large radius of the matrix, a, b, c, g, d, e, g, i - designation of end elements on the small radius of the matrix,

1, 2, 3…16 (without footnotes) - designation of the serial numbers of flat sections and layers in the heat exchanger matrix (in the diagrams of a single group of the spiral-shaped heat exchanger channel - Fig. 3, 4, 8).

The design of the toroidal tubular heat exchanger is shown in Fig. 1. The toroidal body 1 is used when working with two coolants, including in outer space conditions. Without the body 1, the toroidal tubular heat exchanger can be used, for example, as an air-to-air heat exchanger in the incident flow of the outer channel of a dual-circuit turbojet engine. The inlet branch pipe 4, through the annular inlet manifold 5, supplies the internal coolant to the matrix 8, composed of layers of flat sections.

Each flat section-fragment of the heat exchanger (see Fig. 2) contains a group of tubes 9 and two end elements: 10 - for a large diameter of the matrix and 11 - for a small diameter of the matrix 8.

A set of "n" flat sections forms a layer in the matrix 8, perpendicular to the axis of the matrix. The layer can be formed in different ways:

- formation of a matrix layer from flat sections with the location of end elements in adjacent corner sectors (type A);

- formation of a matrix layer from flat sections with the end elements located through one adjacent angular sector (type B), etc.

Fig. 3 shows the diagrams of one spiral-shaped channel of a heat exchanger of type A with a different number of flat sections in the matrix layer with a changing pitch t _A of the spiral-shaped channel. Similar diagrams of one channel of a heat exchanger of type B are shown in Fig. 4. In Fig. 3, 4, each element in the form of a curve segment means one flat section in one matrix layer (the design of the flat section was described earlier in Fig. 2).

The heat carrier passes from the initial end element on the large diameter of the matrix through the tubes of the flat section of the first layer to the end element on the small diameter (solid line with an arrow), then passes to the end element on the small diameter of the flat section of the second layer of the matrix and through the tubes of the second layer of the matrix reaches the end element on the large diameter (dashed line), etc. until the heat carrier makes a full revolution around the axis of the matrix and returns to the initial point by the position of the end element, but already through a step t of the spiral-like channel. It should be remembered that each layer of the matrix contains "n" groups of spiral-like channels, each group of which consists of several tubes of one flat section. Thus, a cross-countercurrent heat exchange scheme is formed, since in the intertube space the flow of the external heat carrier goes from right to left.

Fig. 5 shows the transverse diagram of the heat exchanger type B for n=8, t _B =4δ. The multi-pass nature of the spiral-like channel at step t _B , i.e. the total number of transitions from the large diameter of the matrix to the small diameter and the reverse transitions, depends on the number of groups of spiral-like channels "n" and its evenness or oddness, since the number of layers in step t depends on this. With an even number of channel groups, the step of the spiral-like channel becomes shorter. This is traced in the given diagrams of one channel: Fig. 3 a) c) - the step is equal to t _A =2n δ; Fig. 3 b) d) - the step is equal to t _A =n δ; Fig. 4 b) - the step is equal to t _B =2nδ; Fig. 4 a) - the step is equal to t _B =n δ; Fig. 4 c) d) - the step is equal to t _B =nδ/2.

From each initial end element in the first layer of the matrix, through spiral-like channels go into the matrix, forming a family of cross-transverse tubes of flat sections - an example in Fig. 5 (in this case, one line in Fig. 5 denotes a family of tubes of a flat section, as can be seen in Fig. 2). The same example of a heat exchanger is shown in Fig. 6 in the form of a conventional longitudinal diagram, where the numbers 1, 2 ... (with the letters A, B ... indicate the ordinal layer of the matrix. Spiral-like channels are formed by attaching plugs on the small diameter of the matrix to the end elements of the outer layers of the matrix and between the even and odd layers of the matrix, and, accordingly, on the large diameter of the matrix by attaching plugs to the end elements between the odd and even layers. In Fig. 6, the plugs are indicated by bold lines. One of the groups of spiral-like channels is formed, for example, A1 - a1 - b2 - B2 - D3-d3 -zh4 - Zh4 - A5 - a5 - ... D (2 m-1) - d (2m-1) - zh (2m) - Zh (2m). In the example of the matrix under consideration, there are eight such groups of spiral-like channels, with the beginning A1, B1, B1, G1, D1, E1, Zh1, I1. The output ring collector 7 is mounted at the end matrix, multiple of the pitch of the spiral-like channel. At a distance equal to t _B =4δ, an annular through-flow collector 12 is installed, equalizing by mixing the temperature of the internal coolant coming out of different toroidal spirals of the spiral-like channels: from Ж4 to Е4 in the matrix layer in front of the collector 12 (see Fig. 6 and 5). The annular collector can be installed between even and odd or odd and even layers of the matrix, but in this case, respectively, for a large or small diameter of the matrix.

The heat exchanger matrix can be made with any number of layers (not necessarily multiple of the pitch) to achieve the overall longitudinal dimensions of the heat exchanger, taking into account the placement of the ring collectors.

Depending on the diameters D and d, when designing a heat exchanger, a heat exchanger scheme of type A or B and the number of groups of spiral-like channels "n" in the matrix are selected so that the tubes of the flat sections of adjacent layers form a more frequent spatial lattice. In all Figs. 3 - 5, 7, 8, each line between the end elements A - a, B - 6, etc. denotes a family of several tubes connecting the end elements of the flat sections located on the large and small diameters of the matrix, as shown in Fig. 2.

For some applications, it is possible to manufacture the heat exchanger matrix by assembling individual layers of identical flat sections, each of which is manufactured, for example, by a modern process of selective laser cladding of tubes, end element blanks and plugs. In this case, a whole set of flat sections appears: right, left, plug on a small or large diameter. The assembled matrix is pulled together by longitudinal pins passing between the tubes along the entire length of the matrix. Also, whole layers of the matrix can be made monolithic in the form of corresponding sets.

In space nuclear gas turbine power plants, there are two heat exchangers according to the scheme: a recuperator and a refrigerator. And if the refrigerator can be structurally combined with the external refrigerator-emitter of the power plant, then the recuperator is designed to capture the waste heat, and heat exchange in it occurs between the coolant used in the turbine and the coolant leaving the compressor into the heater for heating. In the recuperator, a coolant with a high pressure (after the compressor) is supplied through the tubes, and through the intertube volume in the casing - with a lower pressure (after the turbine). This allows you to reduce the thickness of the walls of the tubes 9 and end elements 10, 11 (Fig. 2), calculating their strength only for the difference in pressures of the coolants. The walls of the tubes are thinner, which additionally increases the efficiency of heat exchange.

With relatively close values of the diameters D and d, it is possible to increase the number of groups of spiral-shaped channels, while the tubes in the flat sections between the end elements are made straight without bending, which significantly simplifies the technology of assembly operations in the manufacture of heat exchangers. An example is shown in Fig. 7 for one quarter of the circle of the transverse diagram of a type B heat exchanger and in Fig. 8 for the diagram of one spiral-shaped channel of the same heat exchanger with the parameters: n = 32, t _B = 16 δ. When using tubes with a diameter of 12 x 1 mm in flat sections (Fig. 2), the thickness of the end elements δ is 16 mm, and the entire assembly of the matrix of 16 layers makes up a longitudinal size of 256 mm. In this case, the total flow cross-section of all spiral-shaped channels (with four 12x1 mm tubes in a flat section) is 102 ^cm2 , which is equivalent to a pipeline with an internal diameter of 5.7 cm. In this case, according to estimates, the heat exchange area is approximately related as 7700 (D-d) versus 2320 ^cm2 .

The schematic layout of the gas turbine power plant recuperator is shown in Fig. 9, where I is the internal coolant, II is the external. For ground and atmospheric applications, in some cases, the heat exchanger body is not necessary and the flowing air stream serves as the external coolant.

When designing a heat exchanger, a set of parameters is selected in each specific case that ensure the most uniform distribution of intersecting tubes between large and small diameters in the heat exchanger matrix. When designing, the dimensions of the heat exchanger are determined by the required flow rate of the internal coolant: the diameter of the tubes and their number in a flat section, the diameter of the end elements, the number of flat sections and spiral-shaped channels from the condition of constancy and sufficiency of the flow cross-section. The number of matrix layers is also determined for a given length of the heat exchanger; the location of the outer ring collectors on which diameter of the matrix; the direction of the coolant outlets from the outer collectors; possible sectioning/grouping.

The design of the heat exchanger allows for the supply of internal heat carrier from different systems operating autonomously from each other, and even internal heat carriers of different types, through separate groups of spiral-shaped channels; with a common external heat carrier in the intertube space of the heat exchanger.

Claims (15)

1. A toroidal tubular heat exchanger containing a toroidal matrix formed from layers of flat sections perpendicular to the matrix axis, each consisting of several tubes and two end elements in the form of rings located on the large and small diameters of the matrix, characterized in that inside the toroidal matrix around the longitudinal axis, spiral-like channels are formed from tubes grouped by flat sections, with an alternating change in the radial size of the spiral between the large and small diameters of the matrix in successive layers of the matrix, wherein the number of groups of spiral-like channels is equal to the number of flat sections in the matrix layer. 2. The device according to item 1, characterized in that the groups of spiral-shaped channels are formed by placing plugs on the end elements of the flat sections of the outer layers of the matrix and between the even and odd layers of the matrix on a small or large diameter of the matrix and, accordingly, plugs on the end elements of the flat sections between the odd and even layers of the matrix on a large or small diameter of the matrix. 3. The device according to item 1, characterized in that ring collectors are installed on the end elements of the flat sections of the outer layers of the matrix, respectively on the large or small diameter of the matrix. 4. The device according to item 1, characterized in that between adjacent even and odd or odd and even layers of the matrix, an annular through-flow collector is installed, respectively, on the large or small diameter of the matrix. 5. The device according to item 1, characterized in that the plugs on the end elements of the flat sections of one layer of the matrix are made in the form of a common ring corresponding to the large or small diameter of the matrix. 6. The device according to item 1, characterized in that the matrix layer is formed from flat sections with the end elements located in adjacent angular sectors of the matrix layer, type A, while the pitch of the spiral is equal to 7. The device according to item 1, characterized in that the matrix layer is formed from flat sections with the end elements arranged through one adjacent angular sector of the matrix layer, type B, while the pitch of the spiral is equal to where t is the pitch of the spiral of spiral-like channels; δ is the thickness of the end element of the flat section; n is the number of groups of spiral-like channels in the matrix, equal to the number of flat sections in the matrix layer. 8. The device according to item 1, characterized in that the tubes of the flat sections are made rectilinear. 9. The device according to item 1, characterized in that the flat sections are made monolithic with plugs in the form of a set of flat sections with different corresponding placement of plugs on the end elements. 10. The device according to item 1, characterized in that the matrix layers are made monolithic in the form of a set with different corresponding placement of the component parts. 11. The device according to item 1, characterized in that the matrix is placed in a toroidal housing and the coolant with high pressure is connected to the tubes of the spiral-shaped channels, and with lower pressure - to the inter-tube volume of the housing. 12. The device according to item 1, characterized in that the groups of spiral-shaped channels, each or several, are connected to different heat carriers.