GB1566029A

GB1566029A - Multiple flow path bodies

Info

Publication number: GB1566029A
Application number: GB733677A
Authority: GB
Original assignee: Corning Glass Works
Current assignee: Corning Glass Works
Priority date: 1976-02-24
Filing date: 1977-02-22
Publication date: 1980-04-30
Also published as: FR2342122B1; DE2705123A1; DE2705123C2; JPS52103058A; FR2342122A1

Description

(54) MULTIPLE FLOW PATH BODIES (71) We, CORNING GLASS WORKS, a corporation organised under the laws of the State of New York, United States of America, of Corning, New York, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to bodies honeycombed with a plurality of thin-walled cells together providing multiple fluid flow paths through the body. Such bodies may be used for example as heat exchange devices, or particularly recuperators, for instance in turbine or Stirling cycle engines, pollution control devices, and as filtering means in filtration and osmosis processes.

In a gas turbine engine, an air-fuel mixture is burned in a combustion chamber to form hot gases which are directed to a turbine wheel to produce rotary motion of an engine output shaft. After these gases have impinged upon the turbine wheel, and prior to their being exhausted from the engine, it is desirable to extract as much heat energy as possible. The efficiency of the gas turbine engine is increased by transferring the heat energy extracted from these exhaust gases to the compressed intake air prior to its mixture with the fuel and entry into the combustion chamber. One type of heat exchanger that is used to accomplish this energy transfer and raise the temperature of the incoming compressed air is called a rotary regenerator.

This heat exchange system which employs a rotating cyclindrically-shaped regenerator core has in the past been found to be suitable for gas turbine engines. Typically, this regenerator core is made from a ceramic material and is porous to gases which flow substantially parallel to the rotational axis of the core. The porous ceramic regenerator core rotates in a housing that is divided into a plurality of passages. Hot exhaust gases and the cooler compressed incoming air pass through these passages and through the porous regenerator core.

The exhaust gases heat the regenerator core and the regenerator core, in turn transfers this absorbed heat energy to the cooler compressed incoming air. In this manner heat transfer results.

As is evident, this type of rotary regenerator unfortunately requires many accessory items to function properly, such as, drive mechanisms, motors and annular ring gears for rotating the core and rubbing seals and special housings for sealing the different sections of the core and the entire core from the rest of the engine.

Additionally, material requirements of thermal shock resistance, light weight, rigidity against fluid pressure, strength for rotation drive and sealability severely reduce the field of candidate materials for regenerator use.

The multiple flow path bodies of the present invention may be used as a fixed recuperator which does not require movement and therefore does not require the use of all the accessories named. It also enlarges the field of possible materials by eliminating some physical property requirements.

Metal recuperators of the multiple flow path type have been used in the past, for example see U.S.A. Patent No. 3,322,189, but they are not usually capable of being used in very high temperature environments, are difficult and expensive to build, and are cumbersome and inflexible in design, particularly with regard to the flow path of the fluids.

In general, the multiple flow path body of present invention may be used as a recuperator as mentioned above or as a heat exchanger in an afterburner to reduce energy requirements for maintaining combustion in industrial ovens for baking, oxidizing, polymerizing or removing coatings, in organic waste incinerators, in foundry cuplulos, and in internal combustion engines. In addition to operating as a heat exchanger, it may also be used in filtration and osmosis when porous materials are used to produce the honeycombed body.

It is an object of this invention to provide for improved multiple flow path bodies capable of improved flow and heat exchange, susceptible to a great variety of advantageous uses, and a simplified and efficient method of making them.

According to the present invention, there is provided a method of fabricating a monolithic multiple flow path body having a plurality of contiguous flow paths extending therethrough for separate fluid flow, the method comprising the steps of: (a) providing a honeycombed body in the form of a matrix of thin walls together defining a multiplicity of open-ended cells extending generally longitudinally of said body from one end face thereof to another end face thereof, said body being bounded on sides generally parallel to the cell axes by generally opposed upper and lower boundary surfaces connected by first and second side boundary surfaces, the cells being grouped into a plurality of columns of cells, each column being separated from adjacent columns of cells by a fluid barrier wall surface extending continuously from the upper boundary surface to the lower boundary surface and from one end face of the honeycombed body to the other face end thereof.

(b) removing portions of at least one of the upper and lower boundary surfaces and portions of the cell walls joining opposed fluid barrier wall surfaces in selected columns of cells near at least one end face of the honeycombed body to provide, respectively fluid openings in the boundary surface or surfaces leading to fluid flow conduits extending into said body from the said openings and from said end face or faces to cells in the selected columns, and (c) sealably enclosing the spaces between said opposed barrier wall surfaces of said selected columns of cells near the said end face or faces of the honeycombed body to complete said fluid flow conduits, whereby first fluid flow paths are formed leading from the openings through the fluid flow conduits and the cells in the selected columns of cells to the other ends of said cells; and second fluid flow paths are formed through open-ended cells in unselected columns of cells.

The invention will be described in greater detail with reference to the drawings. In these drawings: FIGURE 1 is a view of the multiple flow path body of the invention with exit flues only for first and second fluids sealably attached to ends of the honeycombed body. Similar entrance flues would normally be used in actual operation.

FIGURE 2 is a face end view of the assembly of FIGURE 1 but without the second fluid flue which would otherwise enclose the face end in actual use.

FIGURE 3 is a cross-sectional view cut through an unselected column of openended cells of FIGURE 2 through which the second fluid may flow.

FIGURE 4 is a cross-sectional view cut through a selected column of cells, the fluid conduits, and the end seals of FICT URE 2 and showing the paths through which the first fluid may flow.

FIGURE 5 is a cross-sectional view of an alternative fabrication wherein the cross-section is taken through a selected column of cells and wherein an intermediate fluid barrier surface parallel to the upper and lower boundary surfaces separates the honeycombed body into upper and lower units for separate flow of two fluids in selected cells.

FIGURE 6 is a face end view of an alternative multiple flow path honeycombed body wherein the body is a laid-up structure rather than an extruded structure as in FIGURE 2.

FIGURE 7 is a view of the upper boundary surface of the multiple flow path body looking down into the entrance openings and fluid flow conduits in selected alternate columns of cells near one face end of the body.

FIGURE 8 is a view of the face end of the multiple flow path body showing alternate sealed and open columns of cells.

FIGURE 9 is a section view of Figure 7 in an unselected column of cells showing the open cells extending unobstructed from one face end to the other face end for passage of a second fluid.

FIGURE 10 is a section view of Figure 7 in a selected column of cells showing "Z"-type flow paths for a first fluid through an entrance opening in the upper boundary surface, the shortened cells of the column and an exit opening in the lower boundary surface at the opposite end of the body. The Figure also shows the seal on face ends in the selected column.

FIGURE 11 shows a view of the face end of a multiple flow path body made from a laid-up honeycombed body such as could be produced by U.S.A. Patent 3,112,184.

Looking at Figures 1 and 2, the multiple flow path body of the invention is shown as having a honeycombed body 1 with first fluid exit flue 20 and second fluid exit flue 25. Similar entrance flues on ends opposite the exit flues have been omitted for clarity.

Choice of parallel or countercurrent flow of the two fluids determines whether first and second fluids enter at the same end or at opposite ends of the honeycombed body but the preferred countercurrent flow design is primarily described herein and is shown by the solid and broken arrows in the views.

The honeycombed body is an extruded body having thin cell walls 2 forming an array or matrix of square cells 3 extending the length of the body from one face end shown in Figure 2 to the other face end at the opposite end of the body. The honeycombed body is bounded by cell walls or a separate skin forming an upper boundary surface 4, lower boundary surface 5 and opposed first and second side surfaces 6, 7, in this case forming a body with a rectangular (square) cross-section. The cells are grouped into columns of cells which are separated from adjacent columns of cells by fluid barrier wall surfaces 8. The fluid barrier wall surface may be a composite of the thin walls of the cells in the column as shown, or a separate wall may be formed.It is preferred though not necessary, that the cell walls and fluid barrier wall surface be planar and parallel to one another; though it is only necessary that columns of cells be separate from adjacent columns for independent flow of fluids. Methods of fabricating laid-up and extruded type structures are exemplified by the disclosures of U.S.A. Patents 3,112,184 and 3,790,654.

Entrance openings 9 and exit openings 10 are provided through upper boundary surface 4 and through lower boundary surface 5 into selected columns of cells. Openings in only one surface would provide a "U" shaped flow path for the first fluid; entrance openings in one surface, exit openings in the opposed boundary surface would provide a "Z" shaped flow path; and entrance and exit openings in both surfaces as shown in the Figures, would provide an "I" shaped flow path.Every other column of cells may be selected as shown in Figures, giving a ratio of selected cells for first fluid flow to unselected cells for second fluid flow of 1:1 or some other pattern of selections may be made giving other first fluid cell to second fluid cell ratios, such as 1: 2 or 2:1, usually for providing for different quantities or pressure drop of first and second fluids passing through the honeycombed body.

The first fluid is applied to first fluid entrance openings and recovered from first fluid exit openings by means of the first fluid entrance and exit flues 20 which are sealably attached to the honeycombed body. A metal flue may, for example, sur round a ceramic honeycombed body and be sealed against a hot gas escape by means of asbestos or insulating refractory wool between the body and the flue. The flue 20 includes hole 21 for connecting to a fluid source (not shown) or to a fluid exhaust (not shown). The paths of the fluid from exit openings to the flue hole 21 are shown by the dotted arrows in Figure 2. Other flues, headers, or manifolds which are known for delivering and recovering fluids are equally useable with the multiple flow path body.

The second fluid may be applied and recovered from unselected cells at face ends of the honeycombed body by means of second fluid entrance and exit flues 25 which are sealed to the multiple flow path body in any convenient manner such as that suggested for the first fluid flues.

Open-ended cells for the passage of the second fluid appear in cross-section in Figure 3 showing a section of the honeycombed body of Figure 2 through an unselected column of cells. The fluid may enter and pass, as shown by the arrows, through any or all of the cells 3 in unselected columns when applied to the face end of the honeycombed body by the second fluid entrance flue.

Figure 4 is a cross-sectional view of the honeycombed body of Figure 2 showing the first fluid paths through cells of selected columns of cells. The fluid enters the honeycombed body through the entrance openings 9 in both upper and lower boundary surfaces 4, 5 and passes into entrance fluid conduit 11 which extends in each selected column of cells between fluid barrier wall surfaces and upper and lower boundary surface openings 9. The entrance fluid conduit gives the first < fluid access to all the cells af the selected column so that multiple flow paths are available through the cells 3 to the other (exit) end of the body.

Near the other face end of the body of the first fluid passes out of the cells 3 and into an exit fluid conduit 12 which extends in each selected column of cells between fluid barrier wall surfaces and exit openings 10 in upper and lower boundary surfaces 4, 5, thence out of the honeycombed body through the exit openings to be recovered by the first fluid exit flue. The method of producing the fluid conduits 11, 12 will be described in detail further below.

Figure 5 shows a cross-sectional view through a selected column of cells in an alternative multiple flow path body. The body is similar to that of Figure 4 but has an intermediate fluid barrier 14 generally parallel to the upper and lower boundary surfaces 4, 5 extending from the first side to the second side and from the one face end to the other face end of the body. This intermediate barrier essentially separates the body into upper and lower units and al lows first and third fluids to flow separately through selected columns of cells in upper and lower units while not affecting the flow of the second fluid through unselected cells in both upper and lower units.

Figure 6 shows the face end view of a laid-up honeycombed body which is fabricated by stacking alternate layers of flat 33 and corrugated 32 sheets of green ceramic material. Rounded cross-section cells 34 are grouped in columns by the flat walls 33 which act as fluid barrier wall surfaces. Alternate selected columns of cells are sealed at their ends.

The fluid conduits 11, 12 near face ends of the honeycombed body can be produced by removing portions of cell walls joining the opposed fluid barrier wall surfaces in selected columns of cells, thereby forming fluid flow grooves between the upper and lower boundary surfaces 4, 5. This may be accomplished, for example, by drilling, punching or sawing from upper or lower boundary surfaces through the surface, the cell walls and through the opposed bound ary surface, in which case the entrance and exit openings are made in the boundary surfaces at the same time. In the alterna tive, the fluid flow grooves an entrance and exit openings may be made by sawing cell walls and boundary surfaces from each face end toward the other face end parallel to and between the barrier wall surfaces in the selected columns.

To transform the fluid grooves into fluid conduits and to prevent flow of the second fluid into selected columns of cells, the fluid grooves are enclosed near face ends of the honeycombed body between the fluid barrier wall surfaces along the length of the fluid flow grooves in selected columns of cells. The groove may be enclosed by sealing with ceramic slip, ceramic cement, wax, plastics, rubber, or any other material which is compatible with the honeycombed body, essentially non-porous, and which will be chemically, mechanically and thermally resistant to the fluid and atmosphere during use. Compatibility includes considerations of the thermal expansion for high temperature use.

As shown in Figure 4 the sealing material 13 is forced into selected columns at a depth less than the depth of the fluid flow grooves.

The sealing material may be advantageously urged into these columns as a fluid using a method constituting a preferred embodiment, which will next be described.

The honeycombed body is preferably dipped into a flowable resist material which can become stiff before the cutting and final sealing steps of the method and may then be easily removed by heat softening or by chemical means, e.g. leaching. The term "resist material" as used herein means a material which is firm enough to remain in the cells and give support to cell walls during cutting and also firm enough to keep the final sealant from filling the unselected columns of cells. Materials such as paraffin wax, rubbers, silicone rubbers, plastics or other similar thermoplastic materials which become stiff below their softening temperature are appropriate.

Slurried inorganic materials which dry to a rigid state and can be selectively removed may also be used but are not preferred.

The resist material could also be painted or pressed into the cells but dipping has been effective in filling the cells to a uniform depth of about one-eighth to one-half inch, which is entirely satisfactory for providing support for the thin-walls during the cutting step of the inventive method.

The channels are preferably formed in the selected columns by a gang of band saws or circular saws, although more sophisticated apparatus, such as a laser, could also be used. The saws may be used to make rectangular channels that are gen erally perpendicular to the cell axes (paral lel to the fluid barrier wall surfaces) to provide inlet or outlet openings in both the upper and lower surfaces; or as shown in Figure 10, the saws may be used to make a triangular channel with a diagonal cut which may be used to primarily cut only one of the upper or lower surface, leaving the other intact and thereby providing for only one inlet or outlet opening near each face end for U-type or Ztype fluid flow.

Two diagonal cuts in each selected column may also be used at each end thereby cutting both upper and lower surfaces and forming "K" shaped channels at each end.

Actually, using a straight cut on the diagonal may necessitate cutting a portion of the opposed boundary surface so that sufficient portions of nearby cell walls are removed and the nearby cells are not thereafter sealed by the final sealant. In that, the final sealant would be filled deeply enough to re-seal the opposed surface opening as seen in Figure 7 near the other face end 17.

In any case, in the preferred method, the resist material is filled to a depth generally less than the depth of the cut (depth of the channels) and the body is cooled below the softening temperature in the case of thermoplastic material or dried in the case of an inorganic slip or slurry, to make the restist material stiff. The stiff material then protects the thin walls from breakage and chipping by the saw blades.

Most or all of the resist material should be removed from the selected columnsduring the cutting.

After removing the resist material and portions of the cell walls, the upper boundary surface and/or the lower boundary surface, the final sealant material is applied to the face end of tbe body to enclose the channels on the face end. Preferably the ceramic honeycombed body is dipped into a ceramic slip, slurry, or cement and the selected columns filled to a depth less than the depth of the channel thereby leaving a conduit through at least one boundary surface and through cell wall portions near the face ends of the body.

The sealant may be applied in any fashion and thereafter is cured or sintered as required to form a strong, non-porous, fluid-resistant seal. If the honeycombed body must also be sintered, a final step of heating may accomplish the sintering of the honeycombed body and the final sealant, as well as the removal of the remaining thermoplastic resist material.

It should be evident that the method just described represents an improvement in the fabrication of multiple flow path bodies, heat exchangers such as recuperators by providing production efficiencies associated with rapid setting of selected columns, support of thin cell walls by the resist material in unselected columns during cutting, and rapid and selective sealing of selected columns of cells to define the fluid paths through the selected columns.

In practising the method, extruded honeycombed bodies are preferred, as are ceramic compositions predominantly consisting of a low-expansion material, such as cordierite or beta-spodumene disclosed in U.S.A. Patent 3,885,977 and 3,600,204 respectively. The honeycombed body is preferably pre-fired but may be in the green state during the method in which case the honeycombed body and final ceramic sealant could be co-fired as a final step.

Figures 7, 8, 9 show the final sealant 15 thus applied in honeycomb bodies as described earlier with respect to Figures 1-6 wherein the additional numerals 16, 17 designate the end faces of the honeycomb body, 31 designates the unselected open coluinns of cells, and 32 designates selected columns of cells sealed on face ends with the final sealant material 15.

Figure 10 shows a section view of Figure 7 through a selected column of cells.

Thin cell walls 2 again are shown forming cells 3, however, the cells, as well as the upper boundary surface 4 near one face end 16 and the lower boundary surface 5 near the other face end 17, have been cut to provide an inlet opening 42, an outlet opening 44, a triangular-space, fluid inlet conduit 47 and a triangular-space, fluid outlet conduit 46 in the selected column of cells between the fluid barrier wall surfaces. Further, the final sealant material 15 is shown in the selected column of cells to further deliniate the first fluid Z-type flow paths as are exemplified by the directions of the arrows in the Figure.

Figure 11 shows a multiple flow path body made from a honeycombed body produced by a laying-up process wherein alternate fiat and corrugated green ceramic sheets are stacked and are then covered with boundary surfaces and fired. The body is then treated as described before to obtain the multpile flow path body. Again, the final sealant material 15 is shown.

Although not preferred, an alternative fabrication using the resist material is possible. Firstly, the channels may be formed from face ends of the honeycombed body in selected columns of cells to a predetermined depth and thereafter the face ends may be sealed with the resist material which enters the cells and the channels to a depth preferably less than the depth of the channels. Before the resist material stiffens, it is removed from the channels by a blast of gas directed from above or below the honeycombed body toward the openings in the upper or lower boundary surface so that the fluid resist material is blown out of the channels. It is also noted that if the resist material is of an optimum viscosity, it will flow on its own out of the channels but will remain in the cells in unselected columns after the material is applied to the entire face ends.In either event, the remaining resist material is allowed to stiffen and the remaining steps are completed as in the preferred method.

For use as a heat recuperator or in an afterburner in pollution control devices the honeycombed body is preferably made of a ceramic material but could be made of a metal. Ceramic and metal powders may be formed into honeycombed bodies by a stacking or wrapping process such as described in U.S.A. Patent 3,112,184 or by extrusion of a plastically- formable mass such as shown and described in U.S.A.

Patent 3,790,654.

Likewise, the two processes for producing ceramic and metal bodies may be used to make plastic honeycomed bodies which, along with ceramic and metal bodies, may be used in the invention to produce porous multiple flow path bodies useful in filtration or osmosis processes at low temperature.

The invention method is adaptable to honeycombed bodies having non-parallel and non-planar cell walls forming cells of any cross-sectional shape such as hexa gonal, triangular, bowties, T's; but preferably the cell walls are planar and parallel and also form the fluid barrier wall surfaces and square cells. Preferably, alternate columns of cells are selected but other selections are possible.

The methods preferred also may produce bodies having flow paths for a first fluid which are "U"-shaped, "Z"-shaped or "I"shaped, depending on whether only one of the upper or lower boundary surfaces is cut on both ends; one of the boundary surfaces is cut on one end while the opposed surface is cut on the other end; or both surfaces are cut on both ends. And whereas it is preferred that the columns of cells are either not modified on both ends of the honeycomb body or are modified on both ends to produce U, Z or I-type flow paths for one fluid and straight through flow paths for a second fluid, it is equally possible, though more complicated, to group the cell columns into two groups and then modify one group on one end and modify the other group on the other end or modify both groups on both ends.Modifying a different group of cell columns on each end would result in "L"-shaped or "T"shaped flow paths for both fluids so that the fluids would enter the cell columns from one or both boundary surfaces or from one face end and then exit at the other end of the honeycombed body from the other face end or from one or both boundary surfaces, respectively. Modifying both groups of cell columns at one or both ends would produce U or Z-type flow paths for both fluids or U or Z-type flow paths for one fluid and L-type flow paths for the second fluid. At ends where both groups of cell columns are modified, portions of only one of the upper or lower boundary surface would be removed in the one group and portions of only the other (opposed) boundary surface would be removed for the other group at the end so that separate entrances or exits are maintained for the fluids.Again, these modifications wherein different or both groups of all columns are modified on each end of the honeycomb body, are not preferred and will not be further discussed herein. Further discussion will refer primarily to the preferred process wherein the same group of cell columns is modified at each end.

Three fluids may be accommodated if a barrier wall exists in the honeycombed body intermediate the upper and lower boundary surfaces. Two "U"-type flow paths (one inverted) and one set of straight through flows paths are then possible, making the body similar to a composite of two U-type flow recuperators held back to back (or lower boundary surface to lower boundary surface).

Fluids may be applied to the multiple flow body and removed therefrom through header or manifold assemblies sealed to the honeycomb body and communicating with all fluid entrance and exit openings.

EXAMPLE I The honeycombed body of the invention may be made of metal, plastics or ceramic materials, the latter group being preferred and being exemplified by a family of low expansion cordierite materials disclosed in U.S.A. Patent 3,885,977 and useful in high temperature recuperators of the present invention. Ceramic or metal powders and heat-softened plastics are preferably extruded as plastically deformable batches into monolithic hoenycombed bodies in the manner disclosed in previously mentioned U.S.A. Patent 3,790,654.

A honeycombed ceramic body may be extruded according to the teaching of previously mentioned U.S.A. Patent 3,790,654 using a cordierite composition similar to body F of U.S.A. Patent 3,885,977. The low expansion cordierite has a chemical composition of 49.6% Sio2, 35.9% A1203, and 14.5% MgO and is useful in moderately high temperature applications (below about 1500 C).

Such a body as above described may be tested as a heat exchanger (recuperator) using hot-burned natural gas as the first fluid and cold blown air as the second fluid.

A 2-inch square, sintered cordierite body, 20 inches long and having about 225 square cells per square inch with 10 mil thick walls separating the cells may be modified according to the invention by cutting the upper and lower surfaces and horizontal cell walls from face ends to a depth of about one inch between vertical cell walls in alternate columns of cells and then cementing the face end of the body in the selected columns of cells to a depth of about 1/8 inch with high temperature ceramic cement. The cement may then be sintered and a metal air flue attached at each end of the body and sealed to the body with refractory wool fibre to provide a means of applying the hot gases to the first fluid flow paths through the honeycombed body.

Using the above model, hot air may enter the first fluid entrance openings at about 800-850 C. while a stream of cold air is directed toward the entire face end and enters the open-ended cells at the other end of the body at about 20-25"C. The fluids pass in countercurrent fashion through the body and may be collected at opposite ends when the temperature of the "hot" gas is 30-60"C and the temperature of the "cold" air is 400-450 C. Flow rates may be adjusted to provide for different temperatures at the exit ends but the above data are representative of the magnitude of heat exchange that may take place over a short path length.

EXAMPLE 2 A rectangular 1 x 4 inch honeycombed body, 6 inches long, such as shown in the Figures, was extruded using the method of U.S.A. Patent 3,790,654 and a raw batch given as body F in U.S.A. Patent 3,885,977.

The raw batch was calculated to yield a fired ceramic body with cordierite as the primary crystal phase. The body was fired and the composition was calculated as about 49.6% Six2, 35.9% A1203 and 14.5% MgO, by weight, normalized. The honeycombed body had a regular array of 100 mil square cells separated by 10 mil walls and boundary surfaces parallel to the cell axes of about 20 mils thick.

The fired honeycomb body was dipped, face end first into a heat-softened paraffin wax to a depth of about 1/4 inch. The other face end of the honeycomb body was dipped and filled similarly.

After cooling the wax to a stiff state, alternate columns of cells on one face end were cut one at a time between vertical fluid barrier walls with a straight saw. The cuts were taken diagonally as shown in Figure 10 (at an angle of about 50 to the cell axes) thereby cutting the inlet openings in the upper boundary surface at the same time to a depth of almost 1 inch. The same alternate columns of cells were likewise cut on the other face end, this time cutting the outlet openings in the lower boundary surface. A portion of the opposed boundary surface may have to be removed during this type of cut so that cells near the opposed surface will not be blocked by the final sealant. In this case the opposed surface will be resealed by the final sealant.

After cutting, both ends of the honeycombed body were dipped to a depth of 1/8-1/4 inch into a ceramic cement slurry consisting of 3 parts by weight of OF 180 cement (an aluminosilicate) made by Carborundum Corporation and 1 part finely ground beta-spodumene material with a composition of 78.5% Sift, 16.6% A1203 and 4.9% Li.O, by weight, and made according to U.S.A. Patent 3,600,204. A slip consisting of the original cordierite material in a vehicle could likewise have been used.

Following drying of the cement, the body was fired to a temperature of about 1180"C. to sinter the cement and burn out the remainder paraffin wax.

The resulting body had separate flow paths for two fluids and was successfully tested as a heat exchanger by applying hot gas to the Z-type flow paths through the inlet openings in the upper surface, and blowing cold air countercurrent to the hot gas through the open-ended cells between face ends of the body. The temperatures of the inlet gases and the outlet gases were compared and the successful heat transfer was substantiated by the changes in temperature of the gases.

EXAMPLE 3 A honeycombed body similar to that used in Example 2 was dipped into the paraffin wax on both face ends, filling the cells to a depth of about one-quarter inch.

A saw cut was then made in alternate columns of cells perpendicular to cell axes to a depth of about 3/4 inch. The face ends were then dipped in the final sealant used in Example 2 to a depth of less than onequarter inch and the body was fired to sinter the cement and to remove the remaining paraffin.

The resulting fixed recuperator had, therefore, inlet openings and outlet openings through both upper and lower boundary surfaces thereby providing for I-type flow paths for the first fluid.

EXAMPLE 4 An alternative fabrication was attempted using a honeycombed body similar to that used in Example 2. A diagonal cut was made in each face end as in Example 2 to a depth of about 1 inch in the boundary surfaces of selected columns of cells and then the face ends were dipped into the fluid wax to a depth of about 1/4 inch. While still fluid, the wax in selected columns was then removed by means of a stream of pressurized air directed from above and below the honeycombed body toward the openings in the upper and lower boundary surfaces, respectively.

After removal of the wax from the selected columns, the remaining wax (in unselected columns) was allowed to stiffen before the face ends were dipped into the cement of Example 2 to a depth of 1/81/4 inch. Thereafter, the cement was dried and then fired to about 1180"C. to sinter the cement and burn out the remaining wax.

WHAT WE CLAIM IS: 1. A method of fabricating a monolithic, multiple flow path body having a plurality of contiguous flow paths extending therethrough for separate fluid flow, the method comprising the steps of: (a) providing a honeycombed body in the form of a matrix of thin walls together defining a multiplicity of open-ended cells extending generally longitudinally of said body from one end face thereof to another end face thereof, said body being bounded on sides generally parallel to the cell axes by generally opposed upper and lower boundary surfaces connected by first and second side boundary surfaces, the cells being grouped into a plurality of columns of cells, each column being separated from adjacent

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. data are representative of the magnitude of heat exchange that may take place over a short path length. EXAMPLE 2 A rectangular 1 x 4 inch honeycombed body, 6 inches long, such as shown in the Figures, was extruded using the method of U.S.A. Patent 3,790,654 and a raw batch given as body F in U.S.A. Patent 3,885,977. The raw batch was calculated to yield a fired ceramic body with cordierite as the primary crystal phase. The body was fired and the composition was calculated as about 49.6% Six2, 35.9% A1203 and 14.5% MgO, by weight, normalized. The honeycombed body had a regular array of 100 mil square cells separated by 10 mil walls and boundary surfaces parallel to the cell axes of about 20 mils thick. The fired honeycomb body was dipped, face end first into a heat-softened paraffin wax to a depth of about 1/4 inch. The other face end of the honeycomb body was dipped and filled similarly. After cooling the wax to a stiff state, alternate columns of cells on one face end were cut one at a time between vertical fluid barrier walls with a straight saw. The cuts were taken diagonally as shown in Figure 10 (at an angle of about 50 to the cell axes) thereby cutting the inlet openings in the upper boundary surface at the same time to a depth of almost 1 inch. The same alternate columns of cells were likewise cut on the other face end, this time cutting the outlet openings in the lower boundary surface. A portion of the opposed boundary surface may have to be removed during this type of cut so that cells near the opposed surface will not be blocked by the final sealant. In this case the opposed surface will be resealed by the final sealant. After cutting, both ends of the honeycombed body were dipped to a depth of 1/8-1/4 inch into a ceramic cement slurry consisting of 3 parts by weight of OF 180 cement (an aluminosilicate) made by Carborundum Corporation and 1 part finely ground beta-spodumene material with a composition of 78.5% Sift, 16.6% A1203 and 4.9% Li.O, by weight, and made according to U.S.A. Patent 3,600,204. A slip consisting of the original cordierite material in a vehicle could likewise have been used. Following drying of the cement, the body was fired to a temperature of about 1180"C. to sinter the cement and burn out the remainder paraffin wax. The resulting body had separate flow paths for two fluids and was successfully tested as a heat exchanger by applying hot gas to the Z-type flow paths through the inlet openings in the upper surface, and blowing cold air countercurrent to the hot gas through the open-ended cells between face ends of the body. The temperatures of the inlet gases and the outlet gases were compared and the successful heat transfer was substantiated by the changes in temperature of the gases. EXAMPLE 3 A honeycombed body similar to that used in Example 2 was dipped into the paraffin wax on both face ends, filling the cells to a depth of about one-quarter inch. A saw cut was then made in alternate columns of cells perpendicular to cell axes to a depth of about 3/4 inch. The face ends were then dipped in the final sealant used in Example 2 to a depth of less than onequarter inch and the body was fired to sinter the cement and to remove the remaining paraffin. The resulting fixed recuperator had, therefore, inlet openings and outlet openings through both upper and lower boundary surfaces thereby providing for I-type flow paths for the first fluid. EXAMPLE 4 An alternative fabrication was attempted using a honeycombed body similar to that used in Example 2. A diagonal cut was made in each face end as in Example 2 to a depth of about 1 inch in the boundary surfaces of selected columns of cells and then the face ends were dipped into the fluid wax to a depth of about 1/4 inch. While still fluid, the wax in selected columns was then removed by means of a stream of pressurized air directed from above and below the honeycombed body toward the openings in the upper and lower boundary surfaces, respectively. After removal of the wax from the selected columns, the remaining wax (in unselected columns) was allowed to stiffen before the face ends were dipped into the cement of Example 2 to a depth of 1/81/4 inch. Thereafter, the cement was dried and then fired to about 1180"C. to sinter the cement and burn out the remaining wax. WHAT WE CLAIM IS:

1. A method of fabricating a monolithic, multiple flow path body having a plurality of contiguous flow paths extending therethrough for separate fluid flow, the method comprising the steps of: (a) providing a honeycombed body in the form of a matrix of thin walls together defining a multiplicity of open-ended cells extending generally longitudinally of said body from one end face thereof to another end face thereof, said body being bounded on sides generally parallel to the cell axes by generally opposed upper and lower boundary surfaces connected by first and second side boundary surfaces, the cells being grouped into a plurality of columns of cells, each column being separated from adjacent

columns of cells by a fluid barrier wall surface extending continuously from the upper boundary surface to the lower boundary surface and from one end face of the honeycombed body to the other face end thereof, b) removing portions of at least one of the upper and lower boundary surfaces and portions of the cell walls joining opposed fluid barrier wall surfaces in selected columns of cells near at least one end face of the honeycombed body to provide, respectively fluid openings in the boundary surface or surfaces leading to fluid flow conduits extending into said body from the said openings and from said end face or faces to cells in the selecetd columns, and (c) sealably enclosing the spaces between said opposed barrier wall surfaces of said selected columns of cells near the said end face or faces of the honeycombed body to complete said fluid flow conduits, whereby first fluid flow paths are formed leading from the openings through the fluid flow conduits and the cells in the selected columns of cells to the other ends of said cells; and second fluid flow paths are formed through open-ended cells in unselected columns of cells.

2. A method of fabricating a multiple flow path body according to claim 1, charac terized by providing an entrance for a first fluid into selected columns o fcells near one face end of the honeycomb body and an exit for the first fluid out of the selected columns of cells near the other face end thereof by forming openings in the upper boundary surface and the lower boundary surface of said body, forming entrance and exit fluid flow conduits leading from said entrance and exit openings, respectively, to the cells in said selected columns of cells by removing portions of cell walls joining opposed fluid barrier wall surfaces bounding said selected columns near end faces of said body, and sealably enclosing entrance and exit fluid flow grooves near face ends of the honeycombed body to form, respectively, entrance and exit fluid flow conduits, such that first fluid flow paths are formed from the first fluid entrance openings through the entrance fluid flow conduit the cells in selected columns of cells, the exit fluid flow conduit, and to the first fluid exit openings and second fluid flow paths are formed through openwended cells in unselected columns of cells.

3. A method according to either one of claims 1 or 2, comprising the step of sealably communicating all first fluid entrance openings and all first fluid exit openings to first fluid entrance and exit flues, respectively, and all open-ended cell openings in unselected columns of cells on the one face end of the honeycomb body and all openended cell openings in unselected columns of cells on the other face end thereof to second fluid exit and entrances flues, respectively.

4. A method according to claim 1 wherein the honeycomb body is provided with a matrix of thin walls forming a regular array of open-ended cells having substantially parallel cell axes.

5. A method according to claim 4 wherein the honeycomb body has a rectangular cross-section.

6. A method according to claim 1 wherein the entrance openings are formed only in one boundary surface and the exit openings are formed only in the opposed boundary surface so that Z flow, first fluid paths are formed.

7. A method according to claim 1 wherein the entrance openings are formed only in one boundary surface and the exit openings are formed only in the same one boundary surface so that U flow, first fluid paths are formed.

8. A method according to claim 1 wherein the entrance openings and exit openings are formed in both the upper and lower boundary surfaces so that I-flow, first fluid paths are formed.

9. A method according to claim 1 wherein said selected columns comprise alternate columns of cells.

10. A method according to claim 1 including providing the honeycomb body with an intermediate fluid barrier surface extending continuously from one end face to the other end face and from the first side surface to the second side surface, the barrier surfuce being intermediate and substantially opposed to upper and lower surfaces, and wherein entrance and exit openings are provided in both the upper and lower boundary surfaces, so that separate upper and lower U-flow, fluid paths are formed through cells in selected columns of cells and three fluids may be separately passed through the cells of the honeycombed body.

11. A method according to any one of the preceding claims comprising the steps of sealing the open-ended cells on both face ends of the honeycombed body with a resist material which enters the yells to a predetermined depth, and thereafter becomes reversibly stiff; forming channels of a predetermined depth in selected columns of cells from both face ends of the honeycombed body by removing portions of the cell walls and portions of at least one of the upper boundary surface and the lower boundary surface, all between adjacent fluid barrier wall surfaces in the selected columns of cells; applying a final sealant material to both face ends of the honeycombed body and transforming the chan nels in the selected columns of cells into conduits having at least one open-end, by filling the channels from face ends with the final sealant material to a depth less than the depth of the channels, and removing the remaining resist material.

12. A method according to claim 11 wherein the resist material is thermoplastic and the final sealant is a ceramic cement.

13. A method according to claim 12, wherein the honeycombed body is heated to temperatures at which the resist material is removed and the ceramic cement is sintered.

14. A method of fabricating a multiple flow path body substantially as described with reference to the accompanying drawings.

15. A heat exchanger, recuperator or the like made by the method claimed in any one of the preceding claims.

16. An internal combustion engine, turbine, combustion engine with external combustions, Sterling engine or the like having a multiple flow path honeycomb body made by the method claimed in any one of claims 1 to 14.

17. A heat exchange device comprising (a) a monolithic multiple flow path, honeycombed body comprising a matrix of thin walls forming a multiplicity of substantially parallel cells extending through said body and being bounded on sides generally parallel to the cell axes by opposed upper and lower boundary surfaces of said body and first and second side boundary surfaces of said body interconnecting said upper and lower boundary surfaces, (i) the cells being grouped into a plur ality of columns of cells, each column being separated from adjacent columns of cells by a fluid barrier wall surface extending continuously from the upper boundary surface to the lower boundary surface and from one end face of the honeycombed body to another end face thereof, (ii) selected columns of cells being closed against fluid passage therthrough on both end faces of the honeycombed body while unselected columns of cells are open ended, and (iii) the honeycombed body further hav ing openings in the upper and lower boundary surfaces, near the end faces of the honeycombed body said openings leading into the selected columns of cells via, fluid flow conduits within said body, each conduit extending from one of the openings in the upper boundary surface to one of the openings in the lower boundary surface and between opposed fluid barrier wall surfaces in the selected columns of cells, thereby providing in the body first fluid flow paths through the boundary surface openings and the fluid flow conduits to cells in the selected columns of cells near the one end face of the honeycombed body, through the cells, and from the cells in the selected columns of cells through the fluid flow conduits and the boundary surface open ings near the other end face of the honeycombed body; (b) means sealably fixed to the honeycombed body for communicating a first fluid to the openings in the upper and lower boundary surfaces at the one face end of the honeycombed body; and (c) means sealably fixed to the honeycombed body for recovering the first fluid from the openings in the upper and lower boundary surfaces at the other face end thereof.