US2402307A - Recuperative heat exchanger for gaseous media - Google Patents

Description

June 18, 1946. T. VANNERUS 2,402,397

RECUPER.\TIVE HEAT EXCHANGERFOR GASEOUSMEDIA Filed March 27, 1945 5 she ts-sheet 1 9 7 ll I m A 11 r r 6 4* 4 I I II: P. i '1 i ii :1 i I I I II 1* l' June 18, 1946.: T. VANNERUS REGUPERATIVE HEAT EXCHANGER FOR GASEOUS MEDIA Filed March 27, 1943 5 Sheets-Sheet 2 Invenior T 'Yannerus c A June 18, 1946 T. VANNERUS RECUPERAIIVE HEAT EXCHANGER FOR GASEOUS MEDIA Filed March 27, 1945 5 Shee ts-Sheet s Ina 61?;601" T Yaz'zzagz u, 5

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RECUPERATIVE HEAT EXCHANGER FOR GA SEOUS MEDIA Filed March 27, 1943 5 Sheets-Sheet 4 v; 8/ i g: a; l L

June 18, 1%46. T. VANNERUS RECUPERATIVE HEAT EXCHANGER FOR GASEOUS MEDIA Filed March 27, 1945 5 Sheets-Sheet 5 inventor T, Jazz/226:0 105 Patented June 18, 1946 RECUPERATIVE HEAT EXCHANGERFOR GASEOUS lHEDIA Torbjiirn Vannerua-Motala Verkstad, Sweden Application March 2'1, 1943, Serial No. 480,734

In Sweden April 28, 1942 4 Claims. 1 The present invention relates toimprovements in such known recuperative heat exchangers for gaseous media which comprise a housing, a rotor therein fixed on an axis of rotation and forming.

a set (one or more) of passages of flow for each medium, which sets of passages are adapted for heat exchange between the media through the walls of the passages, each set of passages bein connected to a separate interior axial inlet chamber and to a separate outer outlet chamber.

The two axial inlet chambers may for example in a known way be separated by a partition wall participating in the rotation of the rotor, and the two outlet chambers may for example be separated by a stationary radial partition wall constituting a part of or being connected with the housing.

It is known per se in such known heat exchangers to provide the rotor with fan vanes and to form the outlet chambers as spiral-shaped diffuser channels curved about the rotor to obtain a rotary heat exchanger which acts at the same time as a fan for propelling the heat exchanging media.

The present invention has for its object to greatly improve the efliciency of the heat exchange between the media and at the same time to considerably reduce the necessary dimensions of a recuperative heat exchanger of the above mentioned kind.

The invention is based on the knowledge that heat exchange is improved with increasing relative velocity between the heat exchanger and the gaseous media and with decreasing thickness of the layers of the gaseous media. The velocity of the gaseous media through the passages formed in a rotor of the above mentioned kind is composed partly of a radial velocity, partly of a peripheral velocity. Of these two'components the radial velocity determines the length of time for the media to pass through the rotor, that is the time during which the heat exchange between the media takes place. Thus an increase of the radial velocity shortens the period of heat exchange which is unfavourable. According to the invention, the relative velocity between the heat exchanger and the gaseous media is instead increased by increasing the peripheral velocity between the same as much as possible. This has not been observed in the hitherto known heat exchangers of the aforementioned kind, in which the gaseous media have been forced to participate in the rotary motion of the passages or forced to rotate by means of vanes or the like secured to the rotor so that the relative velocity 2 1 between the rotor and the gaseous media was reduced to nothing or to a low value.

According to the invention the heaigexchange is considerably improved in comparison with the known devices in that the rotor consists of several smooth, preferably plane, metal discsacting as heat exchangers and arranged perpendicular to the axis of rotation and forming several annular slot-shaped passages of flow alternately for one and the other medium respectively which passages are unobstructed to the flow of the gaseous media so that the conveying action of the rotat-- ing smooth discs upon the gaseous media in the peripheral direction is eiiected by the friction between the discs and the media in order to obtain at a high velocity of rotation of the discs a high relative velocity in the peripheral direction between the discs and the gaseous media during the radial outward motion of the latter.

The spaces between the discs forming the passages of flow for the gaseous media are quite free from projecting parts which might act to propel the media, and the feature of the discs being substantially smooth is, of course, to be understood in this sense. The only force acting upon the media in a peripheral direction is the friction between the rotatingdiscs and the gaseous media, and therefore the peripheral relative velocity must reach the highest possible value. At the same time it is possible by reducing the distance between adjacent discs to divide the gaseous media in thin layers which also is very favourable for a good heat exchange.

As it is possible to rotate a heat exchanger ac-- cording to the invention at a high rotary velocity, the dimensions of the same will be correspondingly reduced in comparison with hitherto known heat exchangers of the afore-mentioned kind.

A number of embodiments of the recuperative heat exchanger according to the invention are illustrated in the accompanying drawings, in which Fig. l is a sectional elevation of an embodiment with a rotor consisting of a plurality of plane discs'taken along the line I-I in Fig. 2.

Fig. 2.is a cross-sectional elevation along the line II-II in Fig. 1.

Fig. 3 is a fragmentary development in the plane of the cylindrical circumference of the rotor seen from the line III-III in Fig. 1.

Fig. 4 is a fragmentary development in the plane of the rotor seen from the line IV-IV in Fig. 6 is a sectional elevation along the line VI-VI in Fig. 7 of an embodiment consisting of two rotors secured to a common drive shaft, each rotor having a pluralityof plane discs.

Fig. '1 is a cross-section along the line VII-VII in Fig. 6.

In the embodiment according to Figs. 1-5, I designates the rotor of the recuperative heat exchanger. The rotor I is composed of a plurality of smooth, preferably plane, annular metal discs 2 which are perpendicular to the drive shaft H of the rotor. Between the plane discs 2 a corresponding number of annular slot-shaped flow passages 3 and 4 are formed which passages are unobstructed to the flow of gases. The end discs 5 and 5 of the rotor are secured to the driveshaft II by means of spokes 7, 8 andhubs 9, Ill,

The space in the rotor internally oi the discs 2.

is divided into two axial inlet chambers l3 and I 4 separated from each other'by means of a diagonal partition wall l2, which is connected to and participates in the rotation of the rotor. The rotor is enclosed by a stationary housing I5 which is provided with an axial intake It for one of the gaseous media (in this example air) and an axial intake I! connected to a supply conduit not shown for the second gaseous medium (for example hot flue gases). The inlet chamber l3 communicates with the air intake l8, and the inlet chamber M with the flue gas intake I1.

The flow passages 3, 4 alternately communicate with one of the inlet chambers l3, l4 and are shut off from the other one. Thus all the passages 3 communicate with the inlet chamber l3,

while all the passages 4 communicate with the inlet chamber I4 as shown in Fig. 1.

The outlet, ends of the passages 3 and 4 are covered by a cylindrical wall 18 which is shown developed in a plane in Fig. 3. In the cylindrical wall l8 there are provided for each passage 3 and 4 respectively a number of outlet openings 19 and 20 respectively, which are elongated in the peripheral direction and are distributed about the circumference of the rotor, the openings I9 commimicating with the air passages 3, and the openings 20 with the flue gas passages 4. The openings l9 and 20 are arranged in axial rows distributed about the circumference of the rotor, the rows of openings 20 being peripherally offset in relation to the rows of openings l9 as shown in Fig. 3.

The housing I 5 is divided by a radial stationary partition wall 2| into two separate outer outlet chambers 22 and 23 about the rotor, of which the chamber 22 communicates with the outlet openings l9, but is shut off from the outlet open- 23. The hoods 24, 25 extend from the wall I or 5 respectively. to the wall 20, in which an opening is provided equal to the cross-section of the channel in the hood. Thus the hoods 24 and 25 extend towards the wall 28 alternately in opposite direction's from opposite end walls of the rotor and screen oil the openings I9, 20 from each other as described above.

The outlet chambers 22 and 23 are shaped to form spiral-shaped channels, the cross-sectional area of which increases continually towards a diffuser channel 30 provided with an outlet opening 29.

The plane discs 2 when rotated at high velocity exert a certain fan action upon the gaseous media, but as they act upon the media only by means of friction, the fan action of the discs alone upon the media may not be suflicient to propel the media through the apparatus. However, the projecting hoods 24 and 25 will also act as fan vanes, and if this fan action should not be enough, special fan vanes may be provided on the rotor.

Furthermore, the surfaces of the spokes 1, 8 may be pitched or feathered so as to assist by a propeller-like action in the transport of the media through the apparatus. The major part of the kinetic energy of the gaseous media leaving the rotating rotor is transformed into pressure energy in the spiral-shaped outlet chambers and the diffuser 30 so that the fan energy'oi the apparatus may be utilised for further transport of the media.

In the embodiment according to Figs. 6 and '7 two rotors 48 and 41, each consisting-in accordance wtih Figs. 1-5-of a plurality of plane discs 48 and 49 respectively, are secured to a common drive-shaft 50 and arranged inside a common stationary housing 5|, which is divided into two halves by a radial partition wall 52 arranged in a groove 53 in a ring 54 welded to the cylindrical wall 55 of the combined rotor 48, 41. v

In thi embodiment the air is heated in two steps, and the hot flue gases are cooled in two steps. In the first step air enters the axial inlet chamber 58 01' the rotor 48, and is led through the annular slotshaped air passages 51 of this rotor and the channels 58 communicating with said passages to an axial chamber 59 in the second rotor 41, from where the preliminarily heated air is led through the annular slot-shaped air passages 80 in the rotor 41 into the spiral-shaped w outlet channel 8! which leads to a diffuser 62.

ings 20, whereas the chamber 23 communicates with the outlet openings 20 but is shut oil from the outlet openings I 9. This connection of the outlet openings with the respective chambers 22 and 23 is eirected by hollow screening members 24 and 25 respectively, arranged just outside those outlet openings I9 and 20. Thus the wall 2| and the members 24 together screen on the openings l9 from the outlet chamber 23, while the wal1 2| and members 25 screen ofi the openings 20 from the outlet chamber 22. In the shown example the members 24 and 25 are hood-like and project from the cylindrical wall It.

26 (Fig. 5) designates a radial wall welded to the cylindrical wall l8 in the same plane as the wall 2 I. To the wall 28 a ring 28 with a circular groove 21 is welded. The inner edge of the wall 2| enters the groove 21 and forms a substantially fluid tight joint separating the chambers 22 and The incoming hot flue gas enters first the axial inlet chamber 83 in said second rotor 41, in which the chamber 83 is separated from the chamber 59 by the diagonal partition wall 64 which participates in the rotation of the rotor. From the inlet chamber 82 the hot gases pass through the passages 85 in the rotor and the channels 66 communicating with the passages v55 to an axial chamber 81 in the rotor 46, which chamber is separated from the chamber 58 by the diagonal partitioning wall 58 rotating with the rotor 48.

From the chamber 81 the gases pass through the passages 59 in the rotor 46 into the surrounding spiral-shaped outlet-channel 10 which also leads to a diffuser 62.

Thus the air will be heated in two steps according to the counter-current principle being in the first step (rotor 45) preliminarily heated by the flue gases thathave passed through and been cooled in the rotor 41, in which the preheated air is finally heated in the second step by the hottest flue gas. In this manner the cold medium (air) may be heated to a final temperature that is higher than the final temperature of the hot medium (flue gases) when leaving the heat exchanger. I

The combined rotor 46, 41 is as a unit secured tothe drive shaft 50 by the spokes H, 12 and the hubs I3, 14. The surfaces of the spokes H, I2

may also inthis embodiment be' formed with a pitch to assist in the propulsion of the gaseous media in a propeller-like fashion.

I claim: 1. A recuperative heat exchanger fortwo gaseous media "having difierent temperatures comprising a housing, a rotor rotatable in said housing and including a plurality of annular, radially covered at the outer circumference of the rotor by a cylindrical wall',in which for eacbpassage a number of outlet openings are provided, which openings are distributed along the circumference V of the rotor, outlet openings belonging to the same set of passages being arranged in a corre-. sponding number of axial rows, the rows of outlet openings belonging to difierent 'sets of passages being mutually ofiset peripherally, the different rows of outlet openings being screened off from each other by hollow members forming arranged metal discs forming a plurality of annular, slot-shaped passages of flow for the gaseous media between the discs, a shaft rotatable in said housing and connected with the outer discs of the rotor, a wall arranged internally of the rotor and forming inlet chambers for the gaseous media, a separate outlet chamber for each gaseous medium leaving the rotor, the alternate passages between the discs for the flow of one gaseous medium communicating with one of the inlet chambers and with one of the outlet chambers, means closing communication between the intermediate passages for the flow of the second gaseous medium and saidone inlet chamber and said one -outlet chamber, said intermediate claim 1, and in which said passages of flow are channels communicating with outlet openings of the respective row and with the respective outlet chamber.v

3. A recuperative heat exchanger according to claim 1, and in which said passages of flow are covered at the outer circumference of the rotor by a cylindrical wall, in which for each passage a number of outlet openings are provided, which openings arev distributed along the circumference of the rotor, outlet openings belonging to the same set of passages being arranged in a, corresponding number of axial rows, the rows of outlet openings belonging to different sets of passages being mutually ofiset peripherally, the difierent rows of outlet openings being screened oil? from each other by hollow members forming channels communicating with outlet openings of the re spective row-and with the respective outlet chamher, and in which said hollow screening members are hood-like and project from said cylindrical wall being adapted to act. as fan vanes at the rotation of the rotor.

4. A recuperative heat exchanger, in which two heat exchangers according to claim 1 are secured to the same drive-shaft and interconnected by channels in such a manner that the medium to" be heated is preheated in one rotor in a first step by heating medium that has already been utilised in-the second rotor, in which the medium to be heated is finally heated in a second step by the I heating medium in its hottest state. I ToaBJoRN VANNERUS.

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