US2418191A

US2418191A - Heat exchanger

Info

Publication number: US2418191A
Application number: US513674A
Authority: US
Inventors: William C Parrish
Original assignee: Stewart Warner Corp
Current assignee: Stewart Warner Corp
Priority date: 1943-12-10
Filing date: 1943-12-10
Publication date: 1947-04-01
Anticipated expiration: 1964-04-01

Description

April 1, 1947.

w. PARRISH HEAT EXCHANGE! '7 Sheets-Sheet 1 Filed Dec. 10. 1943 A '1 1947- w. c. PARRISH HEAT BXCHANGER 7 Filed D60. 10, 1943 7 Sheets-Sheet 2 April 1, 1947- w. C. PARRlSI-l ,1

HEAT EXCHANGE! Filed Dec. 10, 1943 7 Sheets-Sheet s April .1, 1947. w c PARRISH' 2,418,191

HEAT EXCHANGER Filed Dec. 10, 1943 7 Sheets-Sheet4 ZIPPER I 180 April 1, 1947.

W. C. PARRISH HEAT EXCHANGER Filed Dec. 10, 1943 7 Sheets-Sheet 5 April 1, 1947. w. c. PARRISH ,1

HEAT EXCHANGER 7 Filed Dec. 10, 1943 7 Sheets-Sheet 6 April I, 1947.

w. c. PARRESH HEAT EXCHANGER Filed Dec. 10, 1945 7 Sheets-Sheet '7 exhaust gases.

gether with the end tabs 52, are welded together in edge to edge relation, and thus form the divider 26 previously referred to. The edges of the deflector strips 50 are weldedto the tube 30, to the cylindrical sheets 34 to 46, and to the case ing 24, so as to provide airtight individual passageways extending through the heat exchanger. For example, the hot fluid entering the manifold 20 will be deflected through an angle of 90 by the helical portions 54 of the deflector strips at the inlet end, will flow substantially longitudinally between the longitudinal portions 56 of the deflector'strips, and will, at the outlet end, he deflected an additional90 in the same direction as the initial deflection, so that the hot fluid entering the manifold 20 will, in the course of its flow through the heat exchanger, be transposed 180? and will, therefore, be discharged through I thehot fluid manifold 2|. In a similar manner, the cold air entering manifold 22 will be deflected through a total of 180 in the course of its flow through the heat exchanger, and will be discharged through the manifold 23.- In this arrangement, the helical portions at opposite ends of each of the strips 50 extend in opposite directions from the straight intermediate portion circumferentially of the heater.

By comparison of Figs. 5 and 6, it will be observed that in the space between the tube 30 and the innermost cylindrical sheet 34, the deflection of the fluid entering the top portion of the heat exchanger will be in a clockwise, direction, whereas in the space between

sheets

34 and 35, the deflection of the hot fluid entering-the manifold will be 180 in the counterclockwise direction. Similarly, the deflection of the fluid in the spaces between the successive cylindrical sheets 34 to 4B and the casing 24 will be alternately in op- I heat exchanger. 1

exchanger maybe made of aluminum or other light weight metals, or their alloys.

As shown by the arrows in thevarious figures, the two fluids flow in opposite directions through the heat exchanger but this is not essential if the difference in initial temperatures of the two heat exchanger may be used as a secondary unit, that is, as a means to transfer heat 'to atmospheric or cabin air from air which has been heated by exhaust gases in a primary heat exchanger. In this latter system it will usually be found to be desirable, if notnecessary, to utilize the counter-flow principle in the secondary In my improved arrangement, comprising the closed tube 30, the concentric cylinders 34' to 4B and the outer casing 24, the space between each two adjacent cylindrical walls is divided by deflector strips into two sections, with one section preferably carrying heating fluid and the other section preferably carrying fluid to be heated. At'the extreme end, the deflector strips are positioned horizontally at opposite sides of the device so as to provide an upper section and a lower section, such strips being deflected circumferentially so as to bring the strips into vertical position at the intermediate portion of the device and thus provide a section at each side of the device, the strips being further deflected circumferentially so as to bring the opposite end portions again into horizontal position at opposite sides and providing upper and lower sections.

In this arrangement, the circumferential deflection of the strips 50 for the innermost sections next to the closed tube 30 is in clockwise direction, while the circumferential deflection of the strips for the next adjacent sections is in a counposite directions, thus providing hot and cold fluids on the opposite sides of each of the cylindrical sheets 34 to 46. This feature of the con- 'struction may be most readily comprehended by comparing Figs. '7, 8, and 9. Due to this arrangement, the construction of the heat exchanger is greatly strengthened since the helical portions of alternate deflector strips, proceeding radially outward from the center of the heat exchanger, lie in different planes and thus serve beter as reinforcements of the cylindrical sheets. Because of this arrangement, the cylindrical sheets may be made very thin and the overall weight of the heat exchanger is thereby reduced.

In most installations it is desirable torhave all of the passageways through the heat exchanger of substantially equal cross-sectional areas, so that the pressure drop due to friction will be substantially uniform across all passageways. In this way the temperature gradient along the heater will be uniform in the different passageways and there will not be any tendency for the walls of some of the passageways tobecome excessively heated. It will be noted that in Figs. 3 and 4 the sheets 34 to 46 and casing 24 are spaced progressively closer together to accomplish this result.

All of the parts of the heat exchanger are preferably made of stainless steel sheets whenever one of the fluids is of a corrosive nature, or of extremely high temperature, such as the engine Due to the arrangement of the concentric sheets and the deflector strips, the

sheet metal may be very thin, sheets in the orderof .007" in thickness being found satisfactory. When both fluids are not extremely hot and are of a non-corrosive nature, the parts of the heat terclockwise direction, the direction of deflection of the strips changing for each two sections as compared with the two sections next adjacent thereto. This causes the strips in each cylinder 1 to be in crossed relationship with respect to the single inlet manifold connected with all of the strips in the next adjacent cylinders, so as to bunched inlet portions of the passageways at the top at one end of the device to direct fluid into alternate sections at both sides of the device, and by the use of a single inlet manifold connected with all of the bunched inlet portions of the passageways at the top at the opposite end of the device to direct fluid into all of the remaining sections of the device. In like manner two outlet manifolds, one at each end and each connected with all of the outlet portions of the passageways at that end, are adapted to receive the fluid passing through the device, the outlet portions ,of the passageways at each end being bunched at the bottom half of the device for convenient connection of the'manifold thereto.

In some installations, especially those wherein the volumetric rate of flow of onefluid is considerably in excess of said rate of flow of the other fluid, it becomes desirable to provide an inequality of cross-sectional area in the flow paths of the two fluids, a larger flow area being. assigned the fluid having the higher volumetric rate so as to prevent such fluid from undergoing an excessive drop in pressure during flow through the exchangers A construction embodying this principle of having the hot and 00111 fluid passageways oi unequal cross-sectional area is dis- .7

closed in Figs. 10, 11 and 12.- The portion of the heat exchanger shown in these flgiires is adapted to be assembled with manifolds of the type shown in Figs. 1 and 2, and is to be used in essentially the same manner. Although the flow of the two fluids through the exchanger is shown in Figs. 10,

11 and 12, as being in the same general direction, this is not essential and the unit may be used with fluids flowing in opposite directions should zontal center line' is in alignment with the longithe condition of the installation require and war- 4 rant such flow condition.

The heat exchanger comprises a central closed end tube 80 and eccentric

cylindrical sheets

82, 84, and 86 with intermediate sheets 83 and 85 and the external casing 81 concentric with the central tube 80. Deflector strips 90 are oi gen-' erally the same form as the deflector strips 50,

but are of tapering width conforming to the in which the are located. l l s ivith deflector strips 50, the deflector strips 90, if desired, can be so constructed as to deflect the fluid at the} exit end, 90 in a direction gen.- erally opposite to the initial deflection, instead of 90 in a direction generally the same as the initial deflection. In the arrangement shown in the drawings, however, the deflection of the fluid entering either the upper passageway or the lower passageway between the wall of the casing 81 and the cylindrical sheet 86 extends through 180 degrees in counterclockwise direction in Fig. 12, and this is true of the deflection of the fluid entering either the upper passageway or the lower passageway between the cylindrical sheets 85 and 84, and true of the deflection of the fluid entering either the upper passageway or the lower passageway between the

cylindrical sheets

83 and 82.

The deflection of the fluid entering the remaining three upper passageways or the remaining three lower passageways, as shown in Fig. 12, extends in each instance through 180 degrees in clockwise direction.

The cylindrical sheets 82 to 8'? are so spaced relative to one another that the areas of the inlet ends of the various passageways are equal. However, it will be noted that the major portion of the inlet area of each of the passageways above the horizontal center line is in alignment with the longitudinal portion of the passageway. For example, the inlet passageway at the top between the cylindrical sheets 83 and 84 increases in size toward the right in Fig.12 so that the major portion of the inlet is located in the upper right hand quarter of said flgure, such major portion being thus in alignment with the longitudinally extending portion of the passageway. The inlet passageway at the top between the cylindrical sheets at and 85, on the contrary, increases in size toward the left in said figure so that the major portion of said inlet is located in the upper left hand quarter of said figure, such major portion being in this instance also in alignment with the longitudinally extending portion of the passageway. Similarly, it will be clear from a consideration of Figs. 11 and 12 that the inlet above the divider between the central tube 80 and the innermost cylindrical sheet 82 has the greater portion of its area to the right as viewed in Figs. 11 and 12. The deflector 90 on the inner portion of the tube 80 has the helical and blocking the space between the tube 80 and sheet 82 to the left as viewed in the figures, and serving as'a baille or tudinal portion of the passageway. This reversal of conditions in connection with the passageways below the horizontal central line in Fig. 12 is due to the fact that the upper inlet passageways increase in the same direction circumferentially as that in which the deflection of the fluid is effected,

while the lower passageways increase in the opposite direction circumferentially from that in which the deflection of the fluid takes place. The

' pp r passageways may be used for the hot fluid,

while the lower passageways fluid.

When the heat exchanger of Figs. 10 to 12 is employed in an airplane and utilizes the engine exhaust gases as a source of heat, the gravimetric flow rate of the exhaust gases will ordinarily are used for the cold be much greater, and the density much less,

than that of the air to be heated. The resultant high volumetric flow rate of exhaust gas is accommodated by the heat exchanger at a relatively low velocity offlow, resulting in a low pressure drop, by reason of the fact that the cross-sectional area of the hot fluid passageways is so much greater than would be the case were the cylindrical sheets all placed concentrically about the central tube as in the construction shown in Figs. 1 to 9. On the other hand, while the pressure drop across'the cold air passageways is increased as compared with the pressure drop in the constructions of- Figs. 1 to 9, this is not of great importance, because of the much lower volumetric flow rate of the cool air which is to .be

heated.

Generally speaking, the loss of heat due to the Entrance, or exit, of a fluid into, or. out of, a

heat exchanger is proportional to the square of the velocity of flow, the proportionality factor increasing with increasing value, in excess of 1. of the ratio oi. the flow area immediately preceding or following entrance to, or exit from, the heat exchanger to the flow area immediately after entrance to, or prior to exit from, said heat exchanger. Since the ends of the passageways through the heat exchanger for, each fluid occupy substantially the whole area of the end of the inlet manifold, the entrance losses will be negligible. Only the edges of the circular sheets will be effective to reduce the total cross-sectional area of the inlets to the passageways, and since these sheets are very thin. their effect will be negligible.

In each ofthe embodiments of the invention,

the deflector strips 50, 90, as well as the cylindrical sheets, provide surfacesfor the transfer of heat, since each of these strips and sheets provides primary heat transfer surfaces; having the hot fluid on one side and cold fluid on the other. Also, in both embodiments the deflector strips are so arranged as to reinforce the cylindrical sheets and to render the heat exchanger assembly structurally rigid. This is of importance since in some installations of the heat exchanger it may project partly through the skin oi the airplane so as, in effect, to constitute a continuation of the skin.

In the latter type of installations, the fluids guide leading to the passage formed to theright. are preferably arranged to flow in the same direction, since one of the manifolds, such, for example, as the manifold 20, may be in the form of an air scoop or ram to provide for flow of ventilatin air through the heat exchanger, this ventilating air after passing through the heat exchanger being discharged into the cabin through manifold 2|, to which a suitable'duct may be connected; On the other hand, the exhaust stack may be connected to the manifold 23' and, after passing through the heat exchanger, the exhaust gases may be discharged through the manifold 22. The manifold 22 may be suitably constructed for the purpose, and be located in the air stream external of the cabin skin, so that the velocity head of the exhaust gases leaving this manifold may be effectively utilized to impart some added speed to the airplane due to the reactive jet propulsion effect of the gases discharged from the manifold.

Each embodiment of the invention may be modified by having the helical portions of each deflector strip extend in opposite directions. In such modified forms of the invention the advantage of having the fluids transposed 180 in their courseof flow through the heat exchangers would be lost, but in some installations, other benefits may more than compensate for this loss.

While I have shown and described particular embodiments of my invention, it will be apparent that numerous variations and modifications thereof may be made without departing from the underlyin principles of the invention. I, therefore, desire, by the following claims, in include within the scope of my invention all such variations and modifications by which substantially the results of my invention may be obtained through the use of substantially the same or equivalent means.

I claim:

1. A heat exchanger comprising, a plurality of cylindrical sheets of difierent diameters positioned one within the other, a plurality of deflector strips secured between uccessive sheets respectively, and dividing each space between adjacent cylindrical sheets into two separate passageways, said deflector strips having their inlet endsin alignment and secured to one another to form a diametral dividing strip and having their outlet ends transposed through an angle of 180 and secured together to form a second diametral dividin strip parallel to the first, and a plurality of mainfolds having ends semi-circular in cross section and secured to said dividing strips and the outermost of said cylindrical sheets.

2. The combination set. forth in claim 1, in which said cylindrical sheets are concentric and spaced to provide passageways equal cross-sectional area.

of substantially 8 3. The. combination set forth in claim in which alternate cylindrical sheets are concentrio with one another and eccentrically located with respect to the remaining sheets.

.4. The combination set forth in claim 1, in which alternate cylindrical sheets are concentric with one another and eccentrically located with respect to the remaining cylindrical sheets, the eccentricity being along the diameter at which the ends of said deflector strips are located.

5. The combination set forth in claim 1, in

which alternate cylindrical sheets are concentric with one another and eccentrically located with respect to the remaining sheets, and in which the areas of the inlet ends of the passageways are substantially equal.

6. A heat exchanger comprising a'plurality of cylinders of different diameters positioned one within the other in spaced relation, 9. pair of deflector strips positioned between each two ads jacent cylinders and fixed in position so as to divide the space into two passageways, eachof said deflector strips having a circumferential deflection through substantially with the strips deflected in opposite directions circumferentially in alternately positioned cylinders and with the inlets of the several passageways in horizontal alignment with each other, a manifold connected with all of the passageways at the top portion of the device at one end communicatin through the passageways with a second manifold connected with all f the passageways at the bottom portion at the opposite end, and a manifold con- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Noyes Jan. 9, 1940 Munday Aug. 16, 1927 Mortensen Apr. 19, 1932 Boehm July 19, 1932 Rosenblad May. 25, 1937 FOREIGN PATENTS Country Date British Mar. 11, 1884 British Mar. 23, 1901 British Sept. 19, 1903 Number Shipman June 10, 1930'