US2821369A

US2821369A - Heat exchangers

Info

Publication number: US2821369A
Application number: US384437A
Authority: US
Inventors: Hilliard Alfred
Original assignee: Carbone Lorraine SA
Current assignee: Mersen SA
Priority date: 1952-10-14
Filing date: 1953-10-06
Publication date: 1958-01-28
Anticipated expiration: 1975-01-28
Also published as: GB756327A; DE1034671B; FR1088732A

Description

A. HILLIARD HEAT EXCHANGERS Jan. 28, 1958 3 Sheets-Sheet 1 Filed Oct. 6. 1953 IN VENTOR I A. HILLIARD HEAT EXCHANGERS Jan. 23, 195

3 Sheets-Sheet 2 Filed Oct. 6. 1953 a v M A. HILLIARD HEAT EXCHANGERS Jan. 28, 1958 3 Sheets-Sheet 5 Filed Oct. 6, 1953 Fig.5i7274 IN VE N TOE ALF/e50 H/L 1. IARD Tram/Em Patented Jan. 2s, 1.958

HEAT EXCHANGERS Alfred Hilliard, Brockwell Park, London, ljlngland, assignor to Societe Le Carhone Lorraine, Paris, France Application ()ctober 6, 1953, Serial No. 384,437

Claims priority, application Great Britain October 14, 1952 8 Claims. (Cl. 257241) This invention relates to heat exchangers of the kind made of blocks of material having two series of holes therein, one series serving for the passage of a fluid therethrough and the other serving either for the passage of another fluid or to contain heating elements. Examples of such heat exchangers are described in the specifications of British Patents Nos. 285,151, 391,817 and 665,899. The manufacture of these blocks is however a somewhat difficult and expensive process involving drilling of many long holes or formation of grooved plates which are permanently cemented together to form the holes.

The main object of the present invention is to provide a construction which offers remarkably high heat exchange efliciency combined with a simple construction of heat exchangers of any required size.

A further object of the invention is to provide a heat exchanger comprising blocks of material each having two series of holes therein to receive two heat exchange means respectively, at least one of which means .is a fluid, 'said blocks being detachably secured together, removable packing means being provided between adjacent blocks.

The blocks have the advantage of being comparatively small and are connected together by means adapted for speedy removal so that any damaged block can be readily replaced. For this purpose, said packing may be a soft cement having a suitable thickness, e. g. at least one thirty-second of an inch, but we prefer to utilise removable gaskets made of a material suitable for providing fluid tight joints when the blocks are clamped together. blocks together to form one or more columns of blocks which can be takenapart for cleaning or replacement. The building up of these blocks enables a large heat exchanger to be constructed with almost unlimited heat exchange areas and existing heat exchangers made in accordance with the invention can be readily increased or decreased in size. The blocks may be comparatively small which facilitates production of the holes by drilling. It is an important feature of the invention that at least one side, but preferably two sides of the blocks are short, so that the drilled passages are correspondingly short. This is desirable to permit easy drilling of heat exchange passages and the use of monolithic blocks free from cement joints, and also for improved heat exchange etficiency which we have found is associated with said short passages.

One of the principal factors affecting the heat exchange efficiency of heat exchangers, is the film effect. By film effect, we mean a substantially stagnant film of the fluid to be treated, which acts as an insulator of heat on the heat exchange surfaces of the heat exchange elements. The film effect will generally increase in severity with increasing viscosity of the fluid to be treated. In certain cases, the film effect may be of such magnitude as to actually overshadow the thermal conductivity of the material from which the heat exchange elements are made. The film effeet can be destroyed, or substantially reduced by turbulence. The most generally applied method to produce said Means are therefore provided for clamping the turbulence, is to pump the heat exchange media .at high flow velocities, past the respective faces of the heat exchange elements. Whereas ;the pumping, at high flow velocities, of non-corrosive fluids, introduces no serious problems, this is not so in the case of corrosive fluids.

The film eifect does not occur immediately at the entrance of a tube or suchl'ike heat exchange passage, but increases gradually towards the interior of the heat exchange passage. This we may call the entrance effect.

If the passages are long, then the entrance effect, with respect to improved heat exchange, is negligible, and its importance increases with decreasing length of the heat exchange passages.

The present invention enables heat exchange equipment to be provided which takes special advantage of the entrance effect in substantially reducing .the film effect with respect to one or both of the heat exchange media by dividing the holes through the column by means of said spaces.

The invention will now be described by way of example with reference to the accompanying diagrammatic drawings wherein:

Figure 1 is a vertical sectional view of a heat exchanger made in accordance with the invention;

Figure 2 is a perspective view of one of the blocks shown in Figure 1, part being broken away to show the holes;

Figure 3 is a vertical sectional view of a second form of heat exchanger made in accordance with the invention;

Figure 4 is a perspective view of one of the blocks shown in Figure 3; and

Figure 5 is a vertical sectional view of a third form of heat exchanger made in accordance with the invention.

In the constructional form of the invention illustrated in Figures 1 and 2, the heat exchanger comprises a series of pressed graphite blocks, 10, assembled on top of each other to form a vertical column; each block is cylindrical with a cylindrical hole 11 axially thereof and formed with banks of holes 12 parallel to the axis and between adjacent banks are other holes 13 which extend from the interior cylindrical surface to the exterior cylindrical surface, and are disposed at a slight angle to the radial so that they are tangential to a cylindrical geometrical figure co-axial with the block. The holes 13 may be in radial planes if desired. The block at each end has a shallow annular recess 14 (Figure 2) leaving

annular ribs

15, 16 at their inner and outer peripheries respectively. These ribs are grooved at 17, 18 to receive

packing rings

19, 20 made of rubber or other suitable elastically deformable material. These recesses 14 in adjacent faces of the blocks form the spaces or gaps 21 which extend transversely across the holes 12. The rubber packing rings form an effective seal around the gap but do not separate the holes 12 from each other. Consequently, the fluid flows through the holes 12, passes out into each gap respectively, whereby the fluid from these holes mixes in the gap and then passes on to the holes 12 in the next block. The holes 12 in adjacent blocks are staggered in relation to each other to avoid tendency for the fluid to flow straight through the gap in the next adjacent corresponding hole, whereby an increase of turbulence is efiected in the gap. This avoids carrying a stream lining or film effect from one hole through a space into the next hole and consequently increases the heat transfer e'fliciency. The length of each hole between adjacent spaces is preferably between 1 /2 and 15 times the diameter of the hole and the spaces are preferably at :least 50% greater in area transversely of the holes than the area -:of the holes in one face leading into a space. The holes 13 are transverse to the outer face of the blocks (where further spaces are provided as will be described) and the holes in adjacent blocks are disposed at an angle to each other. This is effected by locating adjacent blocks upside down in relation to each other. This disposition increases turbulence in the holes and in the spaces at the outer peripheries of the blocks. The thickness of each of the spaces is preferably greater than one third of the diameter or mean diameter of the holes therein. Although theblocks are preferably made of graphite or carbon, they may be made of Monel metal, silicon carbide or other material. Graphite is preferred because of its combination of good thermal conductivity with resistance to chemical attack at elevated temperatures. Its most favourable mechanical property is its compressive strength and the principles of design forming the purpose of the present invention, fully exploit this property. The axial length of the blocks is preferably about one half to one fifth of their diameter. The numbers of the holes 12 may conveniently be 6 to 30 holes in each of to 30 spaced radially extending sections for liquids but may be considerably more for gases.

The blocks are surrounded by a plurality of sections 22 of an outer casing with packing rings 23 at the joints between the sections 22. At the top and bottom of the column are

header plates

25, 26. Clamping

plates

31, 32 engage the header plates and are clamped together by bolts 33 whereby the blocks are clamped firmly but removably together.

The sections 22 are disposed between

rings

80, 81 which in turn are located between

rings

82, 83.

Packing rings

84, 85 made of resilient material are contained under compression in spaces between the header plates '25, 26 and the

rings

80, 81 and 83. The packing assists in preventing leakage in the event of sliding of the

rings

80, 82, or 31, 83 due to unequal expansion between the column of blocks and the casing 22.

Further packing rings

29, 30 are disposed between the

rings

80, 81 and the adjacent ends of the casing 22.

Inlet pipes

34, 35 lead to

holes

36, 37 in the clamping plates which communicate with holes 38/ 39 in the header plates, these latter holes 39 leading to the holes 12 in the upper block. Fluid introduced into the

pipes

34, 35 passes through all the holes 12 in the column and finally is removed through

holes

40, 41 in the bottom header plate,

holes

42, 43 in the bottom clamping plates and outlet pipes 44, 45. The other heat exchange fluid enters through a pipe 47, hole 48 in the bottom clamping plate, and a hole 49 in the bottom header plate leading to the channel 11 in the bottom block. Packing means in the form of obstruction discs 50 made from carbon, rubber or other suitable material are provided between the lower block and the next block so as to close the channel 11 at that position and at each alternate intersection of the blocks. The packing rings 23 also serve as obstruction rings and close the space between the casing 22 and the column at alternate intersections of the blocks and are staggered in relation to the discs 50. Consequently the fluid entering at 47 flows through the holes 13 in the lower block into a space 51 which bridges over the lower block and the adjacent block at the side faces thereof. The fluid then enters the holes 13 in the next block and flows therethrough into channel 11. The fluid then flows upwardly and is again re-directed by the next disc 50 outwardly through the holes 13 in the next block into the next space 51 and so forth to the top of the column where the fluid finally leaves through a hole 53 in the top header block, the hole 54 in the top clamping plate and outlet pipe 55.

As shown in Figures 3 and 4, the blocks 58, instead of being cylindrical, may be of rectangular shape.

The blocks are provided at their opposed faces with spaces 59 'and packing rings 60. At their side faces they are provided with spaces 61 which are isolated by packing ribs 62 formed on the casing 63. If desired, resilient packing rings may be provided between the parts 62 and the blocks. The blocks have a series of vertical holes 65 and a series of transverse holes 66, both sets of holes passing through the width and depth of the blocks, i. e. their short diameters, rather than through the length, in order to keep the holes short. Fluid entering the top header 72 passes down through all of the holes 65 and spaces 59 and leaves through the lower header plate 73. The second heat exchange fluid enters from an opening 68 in the casing and flows through the holes 66 in the top block around the first space 61 into the holes 66 in the next block and so forth, finally leaving at an outlet 69 at the lower part of the casing. Packings 79 are disposed between the blocks and the casing and header plates.

In the modification shown in Figure 5, similar blocks 58 are used, but in addition to being mounted to form a single vertical column, two such columns are mounted adjacent each other with spaces 74 and packing rings 75 at the opposed faces of the two columns. The first fluid enters at 72 as before and passes down through the holes 65 through both columns simultaneously to the outlet 73, while the second fluid enters at 68 and passes through the holes 66 in a sinuous path to the outlet 69 at the lower part of the casing.

The packing rings or gaskets may be made of elastic material, as for example neoprene, poly-tetra-fluoroethylene, rubber, graphited asbestos, nylon and suchlike materials. The choice of a suitable material will depend upon the nature of the fluids, the temperature ranges involved, and so forth.

In some exceptional applications, a cement may be used instead of the said gaskets. The latter, however, should be easily removable and replaceable, so as not to prevent the replaceability of the individual components of the assembly.

When it is required to treat a corrosive medium or media, the outer shell can be protected against chemical attack by providing its internal surface with a corrosion resisting lining, as for example, synthetic rubber, carbon or suchlike corrosion resisting materials as shown by in Figure 1.

Cascade arrangement are possible for example by an arrangement as shown in Figure 5 but having more than two vertical columns, and will prove of particular advantage where very large heat transfer areas are required.

In cascade arrangements of the type of Figure 5, the polypass obstructions in the headers can conveniently correspond to the respective columns of heat exchange blocks 58.

Each of the blocks 10 is preferably a single integrally pressed block of homogeneous monolithic construction as contrasted with a block made up by connecting separate plates together permanently by a cement. The

holes

12, 13 are preferably drilled in the blocks.

I claim:

1. A heat exchanger comprising a plurality of hollow cylindrical blocks of graphite each being an integrally pressed block of monolithic construction, said blocks being arranged in axial alignment to form a column having a central hollow interior, each of said blocks having two series of holes cut therein to receive two heat exchange fluids respectively, the holes of the first series receiving the first fluid and being arranged vertically in banks which are spaced apart from each other and extend through each block from one end surface to the other and the holes of the second series receiving the second fluid and being arranged in banks of holes disposed between and transversely to the banks of the first series and extending through each block from the inner surface to the outer surface thereof, said blocks being recessed at adjacent end surfaces to form a space transversely across all the holes of the first series, removable packing means provided around each space between said end surfaces whereby fluid from the holes of the first series of one block passes into said space and then into holes of the first series of the adjacent block, a casing surrounding the column and spaced therefrom, exterior obstruction means between the casing and the blocks, interior obstruction means within said hollow interior of the column, said exterior and interior obstruction means being arranged to direct the second fluid in a sinuous path through the holes of the second series, header plates at opposite ends of the column having openings therein for conducting the two fluids into and out of the two series of holes separately, and means for holding the header plates and blocks together under compression.

2. A heat exchanger as claimed in claim 1, wherein the holes on opposite sides of the space are staggered in relation to each other.

3. A heat exchanger as set forth in claim 1, wherein the said other series of holes are in rows disposed in planes that are tangential to a small cylindrical figure coaxial with the blocks.

4. A heat exchanger as defined in claim 1, wherein the blocks in the column are arranged so that each block is upside down in relation to the adjacent block to increase the tortuous passage of the liquid passing through the blocks.

5. A heat exchanger as claimed in claim 1, wherein the end faces of the blocks have recesses therein leaving ribs at their peripheries so as to form said spaces.

6. A heat exchanger comprising a plurality of blocks arranged in alignment to form at least one column, each of said blocks having two series of holes therethrough to receive two heat exchange media respectively, a casing on the outside of the column and at least partly spaced therefrom to form at least one outer space between the casing and blocks which outer space bridges over at least first holes of the same series of at least two blocks whereby the first series of holes in one :block open directly to said outer space and the holes of the corresponding series of the adjacent block also open directly to said outer space, and a plurality of removable packing means arranged at intervals between the casing and blocks, adjacent packing means being spaced apart so as to permit flow of medium from the holes of one block through said outer space and into the holes of the adjacent block, the holes of the second series of holes in each block being in communication with each other for flow therethrough of the other medium, each column having at least one interior space in communication with holes of the first series of at least two blocks.

7. A heat exchanger comprising a plurality of hollow cylindrical blocks of graphite said blocks being arranged in axial alignment to form a column having a central hollow interior, each said blocks having two series of holes cut therein to receive two heat exchange fluids respectively, the holes of the first series receiving the first fluid and extending vertically through each block from one end surface to the other and the holes of the second series receiving the second fluid and extending transversely through each block from the inner surface to the outer surface thereof, removable packing means provided between adjacent ends of the blocks to form annular spaces between said ends, said spaces communicating with the holes of the first series whereby fluid from the holes of the first series of one block passes into said space and then into holes of the first series of the adjacent block, a casing surrounding the column and spaced therefrom, exterior obstruction means between the casing and the blocks, interior obstruction means within said hollow interior of the column, said exterior and interior obstruction means being arranged to direct the second fluid in a sinuous path through the holes of the second series, header plates at opposite ends of the column having openings therein for conducting the two fluids into and out of the two series of holes separately, and means for holding the header plates and blocks together under compression,

8. A heat exchanger as set forth in claim 6, wherein the blocks are of graphite and wherein the holes of at least one series have a length of from one and a half to fifteen times its diameter.

References Cited in the file of this patent UNITED STATES PATENTS 504,548 Bauer Sept. 5, 1893 1,571,068 Stancliffe Ian. 26, 1926 1,771,160 Chapman July 22, 1930 1,794,573 Arnoult Mar. 3, 1931 1,992,097 Seligman Feb. 19, 1935 2,152,546 Fitch Mar. 28, 1939 2,537,276 McMahon et al Jan. 9, 1951 2,566,161 Brown Aug. 28, 1951 2,662,748 Huber Dec. 15,. 1953