US3894579A

US3894579A - Heat exchanger devices for fluid flows

Info

Publication number: US3894579A
Application number: US224580A
Authority: US
Inventors: Maurice G Brille
Original assignee: Societe Anonime de Vehicules Industriels et dEquipements SA SAVIEM
Current assignee: Societe Anonime de Vehicules Industriels et dEquipements SA SAVIEM
Priority date: 1971-02-09
Filing date: 1972-02-08
Publication date: 1975-07-15
Anticipated expiration: 1992-07-15
Also published as: IT947434B; GB1382876A; DE2206109B2; DE2206109A1; SU553944A3; JPS506653B1; DE2206109C3

Abstract

Apparatus for producing the transfer of heat from one gaseous flow to another by the alternating and successive passage of the flows through successive sections of an exchanger block having a relatively large specific area comprising a device for dividing the gaseous flows into a plurality of streams flowing in separate passages, the exchanger block of cylindrical configuration being disposed across the passages so as to discontinue same and receive the flows therethrough; a mechanism for imparting an axial reciprocating motion to the exchanger block together with a movement of rotation about its axis; the passages having equal widths and being flat and disposed in parallel relationship, with seals similar to piston-rings disposed between the passages and the block, the sections of the exchanger block consisting of porous elements permitting the fluid flow in the transverse direction but not in the axial direction. This apparatus is particularly adequate for gas turbine equipping land vehicles, notably in that the heat exchanger can be disposed above the longitudinal side members of the chassis.

Description

United States Patent H91 Brille 1 HEAT EXCHANGER DEVICES FOR FLUID FLOWS [75] Inventor: Maurice G. Brille, Suresnes. France [73] Assignee: Societe Anonyme de Vehicules lndustriels et d'Equipements Mecaniques Saviem, Suresnes. France [22] Filed: Feb. 8, 1972 [211 App]. No.: 224,580

1 1 July 15, 1975 Primary Examiner-Albert W. Davis, Jr. Attorney, Agent, or Firm-Stevens, Davis, Miller & Mosher [57] ABSTRACT Apparatus for producing the transfer of heat from one gaseous flow to another by the alternating and successive passage of the flows through successive sections of an exchanger block having a relatively large specific area comprising a device for dividing the gaseous flows into a plurality of streams flowing in separate passages, the exchanger block of cylindrical configuration being disposed across the passages so as to discontinue same and receive the flows therethrough; a mechanism for imparting an axial reciprocating motion to the exchanger block together with a movement of rotation about its axis; the passages having equal widths and being flat and disposed in parallel relation ship, with seals similar to piston-rings disposed between the passages and the block, the sections of the exchanger block consisting of porous elements permitting the fluid flow in the transverse direction but not in the axial direction. This apparatus is particularly adequate for gas turbine equipping land vehicles, notably in that the heat exchanger can be disposed above the longitudinal side members of the chassis.

12 Claims, 21 Drawing Figures mrmmu b 15 I915 SHEET PATEHTEML 15 ms SHEET HEAT EXCHANGER DEVICES FOR FLUID FLOWS The present invention relates in general to means for producing a transfer of heat between gaseous fluid streams, and more particularly to a heat exchanger to be interposed between gaseous fluids, notably supercharging compressed air and exhaust gas of engines, such as gas turbine regenerators-exchangers.

The term regenerator-exchanger designates in general heat transfer devices comprising a block of metallic or ceramic permeable material, against which the hot gases and the compressed air are caused to impinge or flow by turns, in order to cool said gases and heat or re-heat said compressed air.

In most instances it is the porous block that is shifted from the hot gas stream to the compressed air stream, and vice versa.

Heat exchangers of this character consist as a rule of disks rotating at a relatively low speed. However, any communication between the burnt gases on the one hand and the compressed air on the other hand, i.e., between the conduits in which these gaseous fluids are conveyed, must be carefully avoided, since said compressed air circulates under a pressure of the order of 4 to 5 bars (58 to 73 psi) and even a small loss of compressed air by leakage would reduce considerably the turbine efficiency. Therefore, a reliable fluid-tight joint must be provided along the two lines defining the boundaries between the exhaust gas conduit and the compressed air conduit, which are in actual contact with said rotary disk.

However, it is well known in the art that this joint is extremely difficult to obtain, notably at the points of connection between said lines and between said lines and the outer periphery of the disk.

it is the essential object of the present invention to provide a heat exchanger in which the abovementioned inconveniences are safely avoided. In the heat exchanger according to this invention the gaseous fluids are distributed in the form of a sequence of flat parallel jets or streams of substantially equal width in which the hot and cold jets alternate. This jet assembly is discontinued by a cylindrical space extending therethrough and receiving in proper fitting relationship a heat exchanger also of cylindrical configuration to which an axial reciprocating motion is imparted with an amplitude equal to the width of one of said jets, the gaseou-s flows passing through said cylindrical exchanger along planes perpendicular to its axis, between a stacking of cellular plates constituting a porous pattern fluidproof in the axial direction, and according to the present invention a movement of rotation combined with said axial reciprocating motion is imparted to said movable exchanger body.

Thus, in the specific case of a regenerator-exchanger for a gas turbine a block of porous material shifted alternatively from the hot gases to the compressed air, and vice versa, will be used, thus avoiding the rotary disk solution and therefore the joint difficulty by which it is attended, in order to substitute a series of circular packings of the piston-ring type, i.e., elements operating nowadays with zero or substantially zero leakage, for the aforesaid linear joint.

To this end, the gas and air streams are each divided into a plurality of flat layers disposed alternately, i.e., with one gas layer alternating with an air layer. The cylindrical movable block of the heat exchanger is reciprocated along a rectilinear path by using suitable means, so that the section thereof which lies across the gaseous jet is shifted to a position in which it lies across the air jet, and vice versa.

As already mentioned hereinabove a cylindrical block of permeable material is used and the joints provided between the hot gas conduit and the compressed air conduit consist of cylindrical rings. Of course, this block of permeable material is so constructed that the fluids can flow only in the radial direction, not in the axial direction, therethrough. This block may consist of metal and more particularly of metal circular plates stacked to prevent any axial communication and separated from one another by projections, corrugations or peaks imparting a high permeability in any radial direction while creating a turbulence particularly favorable to heat exchanges. The reciprocating motion may be imparted to the cylindrical block either through a crank and connecting-rod mechanism or through a gaseous pressure (for example the pressure of the compressed air) exerted by turns to each end of the block, the air consumption in this case being extremely low in comparison with the turbine output.

The fluid tightness between the walls of the jets and the exchanger is obtained very simply by using circular packings of the piston-ring type, as commonly used in internal combustion engines. These rings are fitted into the wall of the fluid passage and their width is sufficient to cover simultaneously a plurality of cellular plate thicknesses of the exchanger cylinder, so as to constitute therewith a labyrinth-type seal. On the partition side the fluid-tightness or seal is of the valve or autoclave type.

in a typical form of embodiment suggested by way of example these rings may be 5 to 6 mm in width, the cell width being of the order of 0.5 mm, with a reciprocation frequency of less than 10 per minute.

in a modified form of embodiment the rings may consist of two concentric layers of materials having different coefficients of thermal expansion, the material having the higher coefficient being disposed inside the other. With this arrangement, the close-fitted ring tends to seize up when cold and to open out during a temperature increment and therefore when the pressure increases, thus balancing the gas pressure forces applied to these rings and limiting the loss of power due to the dry frictional contact between the rings and the edges of the cellular metal sheets or plates of the exchanger cylinder. In fact, at the same time the pressure developed by the compressed air is effective from the exterior of these rings and tends to compress the rings on the block, these two antagonistic actions of temperature and pressure are properly utilized to cause a positive yet moderate pressure to be eventually exerted on the block, to avoid any premature wear and tear of said rings and also of the block in which they are fitted. This twofold action remains constantly nearly proportional, for in the specific case of a gas turbine the exhaust gas temperature is constantly closely connected to the pressure of the compressed air blown therein.

According to a specific feature characterizing this invention the movement of rotation of the exchanger cylinder about its axis is added to its reciprocating motion. This rotational movement promotes the temperature compensation and therefore the stress in the exchanger cylinder, thus improving the homogeneousness of the exchange action. Preferably, the peripheral linear velocity of rotation is selected to be higher than the linear velocity of the movement of translation.

Under these conditions, the cellular pattern is not a purely directional one. it may consist of a plurality of circular projections having their axes parallel to the exchanger axis and interconnecting the walls of a pair of adjacent plates of the cellular pattern. Thus, any preferential orientation is precluded and a turbulent yet continuous gaseous flow is obtained. This rotation is particularly advantageous in that it tends to equalize the block temperature and avoid distortions. The movement of rotation may be produced independently of the movement of translation, the former being advantageously faster than the latter.

According to a more specific feature characterizing this invention the movements of rotation and translation of the exchanger block are produced simulta' neously from the action of at least one of the fluids flowing therethrough.

By controlling the rotational and translational movements of the cylinder by means of a fluid under pressure the exchanger block can be constructed as a fully self-contained unit as far as the sustained movement thereof is concerned, without resorting to cumbersome and expensive additional mechanisms, a particularly advantageous feature in the case of gas turbine driven land vehicles.

To this end, according to a preferred form of embodiment, the cylindrical exchanger block is mounted for rotation about its axis and the axial planes of the gaseous flow passages are off-set on a same side in relation to said axis.

This asymmetric flow the gases through the exchanger causes the latter to rotate as in the case of a turbine rotor, the loss of pressure in its cellular stacking providing the necessary reaction.

Thus, the passages may be designed with a lateral wall directed tangentially to the exchanger block, the other wall lying approximately in the diametral plane of said block.

This other wall may lead directly to the exchanger or, according to a modification adapted to improve the output, it may be outflared so as to be connected tangentially thereto.

The outlet passages are designed symmetrically to the corresponding inlet passages, in relation to an axial plane of the exchanger block.

This arrangement is also characterized by a considerable flexibility in the orientation of the fluid jets or passages, this constituting a valuable feature in the case of an adaptation to existing vehicles.

The rotational racing of the exchanger block is prevented by the braking action exerted by the sealing rings.

This undesired racing would occur if the rings, when at a relatively high temperature, expanded to a degree reducing to an abnormally low value their frictional contact with the cylindrical surface of the exchanger block. This expansion is balanced by the higher gas pressure in the case of high rotational speed of the turbine, this pressure tending to re-close the rings by valve effect. The higher rotational speed of the exchanger increases the velocity of flow of the gases on the ring surface and therefore the rate of heat transfer, thus tending to cool said rings and to contract them, so as to retard the block rotation.

Conversely, when the exchanger block is retarded or even brought to a standstill the gas mixing action produced about the rings is decreased and at the same time their rapid heating by conduction as a consequence of the contact with the exchanger surface is attendedby the re-opening of said rings. 7

When the reciprocating motion is obtained by utilizing the gaseous pressure of one of the fluids circulating through the exchanger, for example compressed air in the case of an air-gas exchanger of a gas turbine, directed by turns against each end face of the exchanger block, the latter being thus caused'to abut against stop means with its opposite face, this movement is almost instantaneous for the pressure is effective throughout the area of the exchanger face. In order properly to control the temperature increment time of the exchanger block sections, the frequency of the changes of position of said block is adjusted by means of a proper time lag introduced into theoperation of the reversing valve controlling the pressurization of one face and at the same time the release of the other face by venting same to the free atmosphere.

To this end, a reversing valve responsive to an electrical time-lag device may be used, of a type currently used in the field of pneumatic control systems, but a valve incorporating pneumatic retarding means, usually more cumbersome but operating without any external source of power, may also be used.

Thus, according to this invention, the pressure of the fluids circulating through the exchanger is utilized for advantageously and adjustably obtaining the combined alternate movements of translation and rotational movements of the exchanger block. This arrangement is particularly advantageous in the specific case of gas turbine driven land vehicles due to its simplicity and moderate weight and over-all dimensions, and also to its flexibility of mounting and orientation, notably in the case of trucks.

Another essential advantageous feature characterizing this invention is that it facilitates considerably the general design of a gas turbine in the case of a vehicle. in fact, in known heat-exchangers the disks are disposed coercively on the sides of the turbine, so that the transverse over-all dimensions, in. the plane of the turbine shaft become relatively large and are difficult to house between the two longitudinal beams of the chassis. Usually, in order to keep this width within reasonable reduced limits, the fluid passages are constructed with shapes less satisfactory from the point of view of pressure losses. With the exchangers according to this invention these can be disposed above the turbine axis and behind the turbine unit, so that the transverse overall dimensions across the longitudinal members of the vehicle remain within reasonable limits. With the exchangers of this invention it is also possible to use particularly direct exhaust pipes, without any pressure loss except for the flow through said blocks.

Another valuable feature of this arrangement lies in the possibility of directing indifferently and cross the gaseous flows, thus facilitating and permitting the arrangement of the exchanger or exchangers under the best possible conditions in the room available. Furthermore, at least two exchanger cylinders are mounted symmetrically, as a rule, in parallel, with inverted displacement off-settings and the capacity for producing a constant exchange rate.

The heat exchangers according to this invention are also advantageous in that the exchanger cylinders can be removed and replaced very easily for checking and cleaning purposes, by pulling them from one end, like the cartridges of filter units, thus minimizing maintenance costs.

A complete understanding of the invention may be obtained from the foregoing and following description thereof taken together with the drawings in which:

FIG. 1 is a front elevational view of a disk exchanger of a known type;

FIG. 2 is a sectional view of the same disk, taken along a diametral plane;

FIG. 3 is an axial section of a heat exchanger according to this invention;

FIG. 4 is a cross sectional view of the exchanger of FIG. 3;

FIG. 5 is a section similar to FIG. 3 in the ,case of a gaseous pressure motion control system (utilizing for example compressed air);

FIG. 6 is a plan view of a sealing ring;

FIG. 7 is an elevational view of the ring of FIG. 6;

FIG. 8 is a sectional view of a typical ring fitted in position;

FIG. 9 is a sectional view of a composite ring consisting of a bimetallic structure;

FIGS. 10 and 11 corresponding to FIGS. 3 and 5 respectively illustrate a device for rotatably driving the exchanger cylinder;

FIG. 12 is a modified form of embodiment of the structure shown in FIG. 4, wherein the gaseous flows have different directions;

FIG. 13 is a perspective view of a block die for illustrating diagrammatically the multidirectional exchange and turbulence relief elements;

FIG. 14 is a diagrammatic axial section showing a general view of a turbine for equipping a vehicle;

FIG. 15 is a corresponding plane view of an advantageous arrangement for a similar assembly;

FIG. 16 illustrates a plan view from above, in the direction of the axis of the heat exchanger, showing diagrammatically an exchanger block and the means for connecting the fluid passages thereto;

FIG. 17 is a modified form of embodiment of said fluid passages;

FIG. 18 is a diagrammatic axial view of a vehicle turbine assembly, similar to the view of FIG. 14;

FIGS. 18A and 188 show, more specifically, apparatus which may be used in the apparatus of FIG. 18, and

FIG. 19 is a plan view from above taken along the lines XIXXIX of FIG. 18.

Referring first to FIGS. 1 and 2 illustrating a known type of heat exchanger, wherein the disks revolve slowly and intersect simultaneously the cold and hot flows, the two radii separating the two passages and along which it is desired to provide a sealed or fluidtight joint, are clearly shown together with the special rollers for rotatably driving said disks through peripheral teeth, and the particularly elaborate and contorted configuration of the passages or duct means.

FIG. 3 shows in elevation an exchanger constructed according to the principle of this invention, which comprises a compressed air inlet 1, an exhaust gas inlet 2, the division of the inlet duct 1 into a plurality of branch sections 3, the number of these branch sections being if desired greater than two, and also the division of inlet duct 2 into a plurality of branch sections 4 interposed between said sections 3. The cylindrical exchanger block 5 extends at right angles through all these branch sections which on the other hand have all the same width corresponding to the block stroke. The joint between the block and the duct sections is sealed by means of rings 6 illustrated more in detail in FIGS. 6, 7, 8 and 9. These sealing rings are substantially like ordinary piston rings, with a cut gap at mid-height as shown at 7. The compressed air pressure penetrates as usual into the ring groove 8 and urges the ring against the cylinder at 9. As already explained hereinabove, this ring may consist of a bimetallic assembly with the material or strip having the higher coefficient of expansion disposed inside. These two strips may have a constant thickness, or, as illustrated in FIG. 9, a variable thickness to take due account of the higher temperature on the burnt gas side 13 than on the compressed air side 14. In this case the interface of these two strips is oblique, as shown at 12. Thus, by suitably selecting the materials and dimensions of the bimetallic strip, it is possible to adjust very accurately the opening thereof. A slight rounding of the edges of the friction face of these rings will facilitate the engagement and frictional contact with the edges of the exchanger sections during the operation.

The block comprises a series of circular stamped or pressed plates or like elements 21 stacked and clamped on a central rod 15 by means ofend flanges l6 and nuts 17. The extensions of this rod 15 are guided in sliding elements and at the upper end the rod is driven through a connecting-rod l9 and a crank 20. The circular plates 21 may consist of disks formed with projections 22 or peaks 23 (FIG. 13) so that

ducts

3 and 4 are not coer cively directed through the block in mutual parallel relationship as illustrated in FIG. 4, and may form be tween each other an angle as shown in FIG. 12. Since the block is reciprocated in the axial direction through a distance equal to the width of

ducts

3 and 4, the heat stored in the materials is transferred into the next lower or upper cold duct.

The movements of block 5 may be obtained by means of compressed air pressure. In FIG. 5 the same block as described in the foregoing is illustrated but without any extension of the central rod and without any guide means, the compressed air being supplied for example through ducts 24 either to the upper portion or to the lower portion by a valve 25 automatically controlled by pneumatic time-lag means 55. The used air escapes through nozzle means 26. The movement thus obtained is relatively rapid and the block remains a certain time in each end position, the movement being damped out however by a proper control of the air exhaust across the nozzle means 26. In this case the block is retained only by its sealing rings, without any additional stress.

However, if a movement of translation alone is obtained a certain asymmetry may result in the heat transfer action and also in the corresponding expansions. Therefore, the present invention is directed more particularly to a rotary block of the type illustrated diagrammatically in FIGS. I0 and 11. It will be seen that the rod 15 may have a ring shaped extension 27 solid with a gear 28 driven in turn from a pinion 29. The translation is still obtained either through the bead 30 and the connecting-rod and crank

mechanism

19, 20, or through compressed air supplied via ducts 24.

It may be noted that the rotation of the aforesaid block comprising the stamped or pressed metal plates 23 is favorable not only to the temperature balance but also to turbulence about the peaks and therefore to the heat exchange effect. The term peak is used herein to denote any type of round shaped projection producing the same resistance to the gaseous fluid flow in all directions.

Under these conditions it is nearly certain that the exchange rate and regularity are greater than in the form of embodiment comprising a single rotary disk. Therefore, it should be possible, theoretically, to move the block at a higher speed and thus improve its heat transfer capacity, but this speed is limited by the unavoidable air/gas mixing during the axial movements of the block. Similarly, the cross-sectional area of the

inlet ducts

3 and 4 could be increased, but a corresponding increment in the number of rings would result. An optimum choice of the dimensions must be made as a function of the specific and desired performances of this heat exchanger.

It may also be noted that the block rotation is combined with its translation for producing a tacking" movement propitious to the reduction in the coefficient of friction on the block and therefore to the reduction in the mechanical losses and to a longer useful life of the apparatus, even in the case of a ceramic block. In fact, no details have been proposed herein for a possible constitution of a ceramic block, the ideal solution consisting in reproducing as closely as possible what is obtained with the metal elements 23. The plates formed with the aforesaid peaks or like projections may also be made of ceramic. It is also possible to construct a unitary or one-piece ceramic block, provided of course that no axial communication or circulation takes place.

The arrangement may be fitted in a turbine as illustrated in FIGS. 14 and 15 illustrating a typical example of a possible application of these heat exchangers.

The supercharger 31 is driven from the first turbine wheel 32. Within the gaseous flow in said duct the second turbine wheel 33 drives the reduction gearing 34 and the output shaft 35. Between the first and second wheels 32, 33 a swivelling distributor 36 is provided. The air compressed by supercharger 31 is divided into two streams by the symmetric manifolds or header 37. Each manifold or header 37 terminates in front of the vertical cylindrical exchanger 38 and is divided of course as shown in FIGS. 5 and 11. They open into a general manifold or header 39 supplying air to the combustion chamber 40. The primary air necessary for the combustion penetrates at 41 and the secondary air at 42, the stream of burnt or exhaust gas being guided through the manifold 43 directing the hot gases under pressure towards the turbine 32. The gases expanding at the outlet of turbine 33 are directed to the rear through duct means 44 also extending through the heat exchangers 38 after having been divided into a plurality of channels as illustrated in FIGS. 3, 5 and 11, but without changing their direction, except downstream of the turbine at which a single elbow 45 directs them back to the chimney 46.

The means for controlling the movements of exchangers 38 are not shown but the means contemplated in FIGS. 3, 5, l0 and 11 may be used to this end. It may be noted that the exchangers 38 are disposed completely beneath the axis 47 of the turbine unit, i.e.,

above the lognitudinal side members of the vehicle chassis, so that these longitudinal side beams may be disposed in the position shown in dash lines at 48.

The two exchangers must be synchronized and off-set by a half-stroke in order to improve the regularity of the air temperature.

With this arrangement the clogging of the heat exchanger with soot takes an extremely long time and even when it occurs it is clear that the blocks of porous material can be disassembled very easily without having to remove the turbine unit from the vehicle, by simply removing the upper cover and introducing hot gases under pressure for expanding the rings 6 and eliminating their frictional contact. This block replacement may be effected within a few minutes.

According to a preferred form of embodiment, the movements of rotation and translation of the exchanger block are obtained simultaneously through the action of at least one of the pressure fluids flowing therethrough.

To this end and as illustrated in FIGS. 16 and 17 the

axial planes

3,, and 3,, and 4, and 4 of

passages

3 and 4 are off-set in relation to the axis 50 of the exchanger block.

In the form of embodiment illustrated one of the lateral walls of the gaseous flow inlet passage is tangent to the external cylinder of the exchanger block, the other wall being directed in a substantially diametral plane of the exchanger block, and on the other hand the gaseous flow discharge passages are symmetrical to the inlet passages in relation to a diametral plane of the exchanger.

Thus. the exchanger block 5 is rotatably driven about its axis 50 due to the pressure gas introduced through the

passages

3 and 4 and flowing through the sections of block 5. These passages are shifted in relation to the axis 50 so that the dynamic effect of the fluids is preponderant over one half of block 5 and generates a torque producing its rotation. The exchange is advantageously located in positions where elbows are necessary in the general system so that this driving effect can be obtained without resorting to additional means.

FIG. 17 illustrates a modified form of embodiment of this arrangement, wherein the passage is connected through a rounded wall 51 externally tangent to the block 5, thus reducing pressure losses and increasing the passage output.

FIG. 18 illustrates an arrangement contemplated in the case of a vehicle and similar to that illustrated in FIGS. 14 and 15. It will be seen that in this modified arrangement a supercharger 31 driven from the first turbine wheel 32 supplies compressed air to headers 37 having a divided end portion upstream of the cylindrical exchanger 38, the air emerging therefrom being directed by the general header 39 into the combustion chamber 40 through

ports

41 and 42. The combustion gases are directed by

header

43, 44 to exchanger 38 from which they flow to the chimney 46. As shown in this figure the axis 50 of the heat exchanger is disposed across or transversely to the direction of flow of the fluid passages in order to reduce pressure losses by reducing the length of these passages and obtaining a flow path as direct as possible.

FIG. 19 illustrates in section the contour of

passages

37 and 44 in which the gaseous flows impart a torque to the exchanger block 5. As already explained in the foregoing the block axis 50 is off-set in relation to the axial planes of these passages, and the resulting asymmetry of the gaseous flow determines the rotation of said block.

In this example the torque is provided by both hotgas and cold-gas streams. However, the drive may be derived from one fraction only of the gases flowing through the exchanger, the other fraction flowing through the exchanger section without producing any torque or even in counter-current relationship.

With this arrangement it is possible to regulate the driving torque applied to the exchanger and to prevent same from racing, in conjunction with the ring action as explained hereinabove.

This flow of one fraction of the gases in countercurrent relationship which acts as a dynamic brake retarding the rotation of the exchanger block is also advantageous in that it increases the velocity of flow of these gases along its walls and therefore the rate of heat exchange. As the rotatable drive is caused by only one fraction of the gas throughout, it is less sensitive to variations in this throughput.

The reciprocating movement of translation of the exchanger block is also caused by the gas pressure and controlled through the reversing valve 25 (FIG. 18) supplied with gas under pressure through a branch line 52 connected to one of the fluid passages upstream of the exchanger. This gas is distributed by turns to each one of the end faces of the cylindrical exchanger block via

ducts

53 and 54, the pipe associated with the opposite, non-pressurized face being vented at the same time to the atmosphere.

The time-lag actuation of reversing valve 25, preset as a function of the desired heat exchange time of the block sections is obtained through a time-lag device 55. ln the case of an electric time-lag the latter may consist of an electric timing mechanism controlling an electromagnet connected to valve 25. If a pneumatic time-lag device is used the latter is supplied with pressure fluid through a pipe line 56 connected to manifold 52. In the use of an electric time lag device a coil 55' of an electromagnet may be energized by the closure of a circuit through an electric timing mechanism 55''.

In FIG. 18B is shown a preferred embodiment, wherein use is made of the pressure involved by the gases released from the turbine, thus avoiding energy expenses. The device comprises a piston 61 located within device 55, for controlling valve intended to enable the gases coming from duct 52 to flow towards

duct

53 and 54. Duct 52 is connected to duct 56 which cooperates with valve 57 itself connected by means of a rod system to valve 58, so as to feed in turn a gas flow through

ducts

59 and 60 at each respective face of piston 61. Piston 61 is integral with cross-head 62 itself provided with a fork member 63 intended to insure that valve 57, and thus valve 25, is reversed in both directions.

Time-lag device 55 comprises at each end thereof calibrated openings 64 having a flow area smaller than that of

ducts

59 and 60. Gas overpressure within device 55 causes piston 61 to move towards the opposite extremity, until fork 63 pushes the lever of valve 57 out of its point of unstable equilibrium, i.e., in the opposite position, thus actuating valve 25 so as to invert the gas flow within

duct

53 and 59 towards

ducts

54 and 60, wherein the aforesaid process is repeated, due to the pressure increase on the relative face of piston 61.

Of course, various modifications may be applied to the specific forms of embodiment of the present invention which are shown and described herein, without departing from the scope of the invention as defined in the appended claims.

What is claimed as new is:

l. A device for producing a heat exchange between gaseous flows in which the heat transfers take place between a hot flow and a cold flow by causing said flows to be directed by turns and successively through sections of a heat exchanger block comprising:

a. a plurality of adjacent flat and parallel passages of equal width into which said gaseous flows are divided, the passages receiving the gas to be cooled alternating with the passages receiving the gas to be heated, said plurality of passages being associated with and interrupted by a cylindrical space disposed thereacross;

b. a cylindrical exchanger block provided within said cylindrical space and being both axially reciprocating and rotatable therein, the amplitude of reciprocation corresponding to the width of one of said passages, said block including stacked pressed plates forming a porous cellular structure in the transverse direction but being fluid-tight in the axial direction of said block so as to provide fluidtightness between said gaseous flow passages and said enchange block, said gaseous flows passing through said block in planes perpendicular to the block axis;

c. circular seals in frictional contact with the periph eral surface of said block and fitted in the walls of said plurality of passages to provide said fluidtightness;

d. means for axially reciprocating said exchanger block, said reciprocating means including the flow of at least one of said gases flowing through said block; and

e. means for continously rotating said exchanger block, said rotating means including the flow of at least one of said gases flowing through said block.

2. Heat exchanger device according to claim 1 wherein said means for axially reciprocating comprises means for alternately supplying one of said gases to an upper and lower portion of said exchanger block.

3. Heat exchanger device according to claim 2 wherein said means for alternately supplying comprises:

a. a first duct connected to the upper portion of said block;

b. a second duct connected to the lower portion of said block; and

c. an automatically controlled valve for directing a supply of the gas to either said first or second duct.

4. Heat exchanger device according to claim 1 wherein the alternate passages have axial planes that are off-set on a same side in relation to the axis of rotatiori of said block and said rotating means comprises at least one fraction of said gaseous flow directed across said exchanger block.

5. Heat exchanger device according to claim 4 wherein one of the lateral walls of the off-set alternate passages is tangent to said exchanger block, the other lateral wall being directed in a substantially diametral plane of said block.

6. Heat exchanger device according to claim 5 wherein said lateral walls of said passages lying substantially in a diametral plane of said block are connected thereto through a rounded portion directed tangentially to the outer cylindrical surface of said exchanger block.

7. Heat exchanger device according to claim 4 wherein said passages for receiving the gas to be cooled are disposed symmetrically to the passages for receiving the gas to be heated in relation to a diametral plane of said exchanger block.

8. Heat exchanger device according to claim 4 wherein one portion of the passages for receiving the gas to be heated is off-set on a same side in relation to the axis of said exchanger block and another portion is off-set on the other side of said axis whereby the difference between the inverted torques applied to said exchanger block causes the rotation thereof.

9. Heat exchanger device according to claim 1 wherein said reciprocating means comprises:

a. means for exposing gas by turns to the end faces of said exchanger block;

b. a reversing valve means for alternately supplying the flow of gas to the respective end faces; and

c. time lag means for actuating said reversing valve.

10. Heat exchanger device according to claim 9 wherein said time lag means comprises an electromagnetic control device connected to said reversing valve means and an electric timing mechanism associated with said electromagnetic control device.

11. Heat exchanger device according to claim 9 wherein said time lag means comprises a pneumatic timing device responsive to one of the gases flowing through said exchanger block.

12. Heat exchanger device according to claim 9 wherein said reversing valve means simultaneously supplies gas to one end face of said exchanger block and vents gas from the other end face to the atmosphere.

Claims

1. A device for producing a heat exchange between gaseous flows in which the heat transfers take place between a hot flow and a cold flow by causing said flows to be directed by turns and successively through sections of a heat exchanger block comprising: a. a plurality of adjacent flat and parallel passages of equal width into which said gaseous flows are divided, the passages receiving the gas to be cooled alternating with the passages receiving the gas to be heated, said plurality of passages being associated with and interrupted by a cylindrical space disposed thereacross; b. a cylindrical exchanger block provided within said cylindrical space and being both axially reciprocating and rotatable therein, the amplitude of reciprocation corresponding to the width of one of said passages, said block including stacked pressed plates forming a porous cellular structure in the transverse direction but being fluid-tight in the axial direction of said block so as to provide fluid-tightness between said gaseous flow passages and said enchange block, said gaseous flows passing through said block in planes perpendicular to the block axis; c. circular seals in frictional contact with the peripheral surface of said block and fitted in the walls of said plurality of passages to provide said fluid-tightness; d. means for axially reciprocating said exchanger block, said reciprocating means including the flow of at least one of said gases flowing through said block; and e. means for continously rotating said exchanger block, said rotating means including the flow of at least one of said gases flowing through said block.

3. Heat exchanger device according to claim 2 wherein said means for alternately supplying comprises: a. a first duct connected to the upper portion of said block; b. a second duct connected to the lower portion of said block; and c. an automatically controlled valve for directing a supply of the gas to either said first or second duct.

4. Heat exchanger device according to claim 1 wherein the alternate passages have axial planes that are off-set on a same side in relation to the axis of rotation of said block and said rotating means comprises at least one fraction of said gaseous flow directed across said exchanger block.

7. Heat exchanger device according to claim 4 wherein said passages for receiving the gas to be cooled are disposed symmetrically to the passages for receiving the gas to be heated in relation to a diametral plane of said exchanger block. 8. Heat exchanger device according to claim 4 wherein one portion of the passages for receiving the gas to be heated is off-set on a same side in relation to the axis of said exchanger block and another portion is off-set on the other side of said axis whereby the difference between the inverted torques applied to said exchanger block causes the rotation thereof.

9. Heat exchanger device according to claim 1 wherein said reciprocating means comprises: a. means for exposing gas by turns to the end faces of said exchanger block; b. a reversing valve means for alternately supplying the flow of gas to the respective end faces; and c. time lag means for actuating said reversing valve.