US3435894A

US3435894A - Heat exchangers

Info

Publication number: US3435894A
Application number: US590874A
Authority: US
Inventors: Herbert F Maddocks
Original assignee: HERBERT F MADDOCKS
Current assignee: HERBERT F MADDOCKS
Priority date: 1965-11-03
Filing date: 1966-10-31
Publication date: 1969-04-01
Anticipated expiration: 1986-04-01
Also published as: BE689174A; NL6615439A; GB1115988A; DE1501577A1; CH467986A; FR1503001A

Description

April 1, 1969 I H. F. MADDOCKS j 9 v HEAT EXGHANGERS Fil ed Oct. :51. 1966 Sheet are" OOCDCL++++OOO Q O Q Q Q C G QC++ +QO QC-++ +++++f+:')()

April 1, 1969 H. F. MADDOCKS HEAT-EXCHANGERS Sheet Filed Oct. 51. 1966 P 1, 1959 H. F. MADDOVCKS 3,435,894

HEAT EXGHANGERS Filed Oct. 51. 1966 Sheet 3 I of e O O D O O D O O O H. F. MADDOCKS HEAT EXCHANGER'S April 1, 1969 Sheet Filed Oct; 31. 1966 All: LCFMU H. F. MADDC5CK$ 3,435,894

April I 1969- HEAT EXCHANGERS Filed Oct. 31. 1966 Sheet 6 era Ca M4 M1 April 1, 1969 H. F. MADDOCKS HEAT EXCHANGERS G of 6 Sheet Filed Oct. '31. 1966 I Q Q (j l n wdkmuntum United States Patent US. Cl. 165-167 17 Claims ABSTRACT OF THE DISCLOSURE A heat exchanger assembly comprising a plurality of heat-exchanger elements, each element being of boxlike configuration having opposed parallel walls between which extend a plurality of tubular members constituting fluid passages, the rim or peripheral portions of the elements being laterally enlarged, so that when assembled in face to face relation, the rim portions only of the elements are in contact, and flow chambers communicating with the tubular members are provided between the parallel walls of the elements to permit circulation of one fluid through the tubular members of the several elements. The perimeter of the elements is open at two opposed portions to permit insulation of a second fluid through the elements and over the tubular members, other portons of the perimeter of the elements being closed.

The present invention relates to improvements in heat exchangers and also to heat exchanger elements for incorporation in heat exchanger equipment.

In my copending US. Patent 3,308,879, granted Mar. 14, 1967, heat exchanger elements have been described consisting of a hollow body having integral tubular elements extending between opposed faces thereof to permit a first fluid to flow from one exterior surf-ace of the body to another exterior surface and to permit a second fluid to flow in the space between the opposed surfaces of the body and around the outer surfaces of the tubular members. Adjacent element-s may be assembled with the formation of chambers between adjacent elements, one fluid being caused to pass from one chamber to the other, traversing the tubular members internally while the second fluid is caused to flow through the spaces of all elements lying between the opposed walls thereof as mentioned above.

A heat exchanger embodying these elemen-tshas proved to be extremely efficient in heat transfer properties permitting relatively small and compact exchanger equipment to be provided giving high transfer efliciencies with comparatively small equipment sizes. The efficiency of such a heat exchanger is due in part to the possibility of using comparatively thin walled heat exchanger elements where the tubular members thereof and the opposed surface parts are formed integrally by electro-forming techniques, although other production methods may be utilised such as the so-called electroless chemical deposition methods. Both in electro-deposition and in the case of electroless forming the elements are produced by producing a metal coating on a suitable mould or matrix, which is subsequently eliminated leaving an integral, one piece thin-walled component which provides the heat exchanger element. Such element can be produced of resistant metals. for example nickel, or of alloys, which may be provided with noble metal coatings on one or both sides according to service requirements, of silver, gold or rhodium for example.

The present invention is particularly directed to improved forms of heat exchanger elements of the charice acter above referred to and to improved heat exchanger structures embodying such elements.

A heat exchanger element according to the present in-- vention comprises opposed parallel faces and a series of integral tubular members extending between them and having openings in the two faces, such members being intended for assembly with adjoining faces parallel and spaced one from the other to form flow chambers between them, and in which the outer perimeter of each element incorporates closed sections and open sections.

Conveniently the element is of broadly rectangular shape, two opposed sides of the rectangle being closed by a marginal wall extending at right angles to the opposed parallel surfaces, while the other opposed edges are open for the purpose of admitting one of the fluids to the space between the parallel side Walls and around the outer surfaces of the tubular elements. The invention is not, however, restricted to exchanger elements of rectangular shape as they may also be of part-circular shape such as defined by a circle intersected by two parallel chords on opposite sides of the axis and equidistant from said axis. In this case the perimeter of the exchanger incorporates part-circular sections which. may be closed sections and parallel linear sections which may be open sections.

Whatever construction or configuration is adapted, each exchanger element is preferably provided with -a raised rim part extending around its whole perimeter so that when adjacent elements are assembled in facial contact, chambers are formed between the flat surfaces bounded by the raised marginal portions of adjacent elements, and preferably the tubular members in adjacent elements are non-coincident so that a fluid being caused to flow from one chamber to the other through the tubular members of adjacent elements is caused to take a sinuous path ensuring a high degree of turbulence and avoiding laminar flow effects for the purpose of maintaining a high transfer efliciency.

Such elements may be. formed by electro-forming methods or electroless forming methods from any suitable metals, but in many cases nickel is the preferred material because of its high strength, high corrosion resistance and other favourable mechanical properties. Moverover, such articles may be readily produced by electro-deposition methods with thin walls providing adequate strength and good heat transfer property between the two fluids being dealt with. If desired such elements may be formed from different metals in successive layers or may be provided on one or both sides with a protective coating of a noble metal as already referred to.

Such elements can be economically produced by means of a mould or matrix of a readily fusible conductive material, such as a low melting point alloy, and after the required coating has been performed thereon, with the formation of integral tubular members by deposition in suitably placed apertures in the matrix, the latter may be removed by fusion leaving the heat exchanger element as a thin-Walld component ready for assembly in a heat exchanger unit. The closed wall edges of such elements are, of course, produced at the same time as the remainder of the element so that the face parts, the closed edge parts and the tubular elements are integral sections, all comprising a unitary structure.

It will be understood that the marginal parts of each element by which chambers are formed between adjacent pairs of elements and which marginal portions may be raised to a higher lever than the remainder of the face parts, result in the formation internally of each element of a ductway through which a fluid caused to pass between the two walls of each element could flow freely without encountering the outer surfaces of the tubular elements which are distributed over the whole face of each element within the marginal parts; which latter do not, however, incorporate the tubular elements. To minimize flow of the fluid through these ducts the latter may incorporate separate filler elements which are inserted after production and which elements may consist for example of suitably shaped plastics strips which substantially fill the ducts and cause the fluid to pass through that section of the element which incorporate the tubular elements. Such plastics filler elements may consist of suitable material having regard to the fluids being handled, strips of polyvinyl chloride being suitable in many cases.

The present invention further comprises a heat exchanger of the cartridge type comprising an outer casing and a plurality of heat exchanger elements accommodated in said casing, said casing including ductways to cause a fluid to pass in succession through the spaces formed between the parallel walls of each element in a flow path comprising several successive elements.

The outer casing may include inlet and outlet means disposed at the two ends to cause fluid to flow transversely through the tubular members of each element in turn and from one chamber to the next and further inlet and outlet means for a second fluid, said outlet means opening into passages leading peripherally towards the elements, said casing further including guides to cause said second fluid to flow successively through groups of elements in a controlled path.

In many cases the tubular members referred to may be of circular cross-section, this arrangement being particularly suitable for liquid to liquid exchanger systems. In the case of liquid to gas or liquid to air exchangers, it may be preferable, however, to adopt an alternative construction of the tubular members, making them of elongated form as seen in the direction of flow of the gas or air. Such members may be of sinuous form in plan, the raised parts of one member entering the depressions of an adjacent member and so on alternately to provide good heat transfer conditions. Preferably the air flow passages between adjacent elements are of uniform cross-section throughout, although this may require that the widths considered in the same direction of the facing walls of the tubular members vary at different points of the sinuous curve. The tubular members may include straight exit sections for the gas or air flow to promote optimum flow conditions.

The present invention further includes a heat exchanger comprising an assemblage of elements having such elongated sinuous tubular members, such exchanger being in the nature of a radiator with the different component elements rigidly assembled but with the aligned open edge sections placed in free contact with the atmosphere or in association for causing flow of air or other gaseous medium through the spaces between the parallel faces of all the exchanger elements.

The features of the present invention as above referred to and constructional forms of heat exchanger equipment incorporating such exchanger elements are illustrated by way of example n the accompanying drawings in which:

FIG. 1 is a perspective view illustrating one form of heat exchanger element according to the present invention,

FIG. 2 is an edge view of FIG. 1 seen in the direction of an open edge,

FIG. 3 is a section on the line III-III of FIG. 1,

FIG. 4 is a perspective view illustrating another form of heat exchanger element according to the present invention,

FIG. 5 is a partial longitudinal section showing a heat exchanger incorporating heat exchanger elements as shown in FIG. 4;

FIG. 6 is a section on the line VIVI of FIG. 5,

FIG. 7 is a sectional view showing part of the heat exchanger incorporating heat exchanger elements as shown in FIGS. 1 to 3,

FIG. 8 is a cross-sectional view on the line VIIIVIII of FIG. 7,

FIG. 9 is a plan view partially in section showing an alternative form of heat exchnager element particularly suitable for gas to liquid heat exchangers, and

FIG. 10 is a view showing a radiator incorporating the elements shown in FIG. 9.

Referring to FIGS. 1 to 3, the heat exchanger elements 8 incorporate parallel opposed faces with integrally formed tubular members 9 extending between them in the manner described more fully in my copending US. Patent 3,308,879 aforesaid, the side walls of the tubular elements being formed integrally by electro-forming or other similar processes, a suitable metal for example nickel, being deposited on a fusible or soluble matrix which is subsequently eliminated by melting or dissolving it out.

Each element 8 is open at two opposed edges, for example the edges 10, and is closed at the other two opposed edges, as indicated at 11, by means of end walls. Plastic fillter strips 12 extend within the channel formed within the element adjacent the closed edges 11, this channel resulting from the fact that the marginal edges of the elements are free from the tubular connecting members 9 and are provided with a raised rim part 13 extending around the periphery of the element on both faces.

The invention is not specifically limited to heat exchanger elements 8 of square or rectangular shape since alternative shapes may be adopted; in particular as shown in FIG. 4 the opposed parallel edges 11 may be of curved formation defined by a cylindrical surface the open edges 10 then being defined by chords intersecting such peripheral surface.

In this case filler members similar to those shown at 12 in FIG. 3 may be provided, such elements being of curved form in plan to suit the curved peripheral closed walls 11.

Conveniently a number of such elements are joined together to form a complete unit by coating the adjoining closed edge parts 11 by soldering or brazing, or by bonding with epoxy resins or the like, the coating extending over the peripherally closed edge parts 11 to form a continuous surface, such soldering, brazing or bonding forming the joint between adjacent rim parts 13. The joining of the rim parts is also operative between the rim parts 13 at the open edge sections 10 so that the chambers defined by the parallel faces bounded by the raised rim parts are peripherally sealed and thus a fluid flowing transversely of the elements passes from one chamber to the next through the tubular members 9. Preferably the tubular members of adjacent elements are relatively offset to ensure that said fluid moves in sinuous paths in traversing the heat exchanger, thereby ensuring extremely high transfer efficiencies.

Exchanger elements according to the present invention may be built into cartridge type exchangers in a variety of ways and in accordance with the particular transfer operations which are involved. FIGS. 5 to 8 show typical arrangements suitable for liquid to liquid exchange operations although the same principles are broadly applicable to liquid to gas exchangers although in general greater flow areas are required where a gas is being handled. Thus the construction of FIGS. 5 and 6 may be readily arranged for gas to liquid or gas to gas exchange systems whereas the arrangement of FIGS. 7 and 8 are more suitable in the form shown for liquid to liquid exchangers.

The arrangement shown in FIGS. 5 and 6 is intended for use with the elements shown in FIG. 4. As shown in FIG. 5 a plurality of the heat exchanger elements 8 shown in FIG. 4 are assembled face-to-face, bonding material being provided at the edges where the raised marginal rim portions 13 come into facial contact or if desired said rim portions may be joined by brazing, soldering or other similar joining operations. A pile of heat exchanger elements so formed is incorporated within a tubular casing 17 which is flanged at its two ends as indicated at 18.

D-shaped clamping members 19 of angle section are adapted to clamp the elements 8, inwardly directed arms engaging the straight edge parts of the elements, being forced into intimate contact with them by means of clamp bolts 21.

The outwardly directed arms of the members 19 at each end of the pile of elements are adapted to receive flanged terminal members 22, 23 forming parts of pipe coupling members 24, 25 having terminal flanges 2'6, 27 for coupling to feed pipes.

The pipe connecting flanges 26 and 27 are arranged to provide for a flow of fluid through the heat exchanger elements 8, the fluid passing through the tubular members 9 then into the chambers 28 formed between each element 8 and its neighbours, then through the tubular members 9 in the next element and so on in succession. The arrangement of the tubular members 9 is such that fluid cannot flow directly through one aperture in one element to a similarly placed aperture in the next element since the apertures are staggered as between adjacent pairs of elements to ensure that the fluid is caused to take a sinuous path through the exchanger.

A second fluid flows through inlet and outlet connec tions 31, 32 formed in the peripheral wall 17. Flow guides 33 are provided in the D-shaped gap between the straight open edge part 10 of the piled elements 8 and the circular wall part of the casing 17 and are arrenged, as shown in cross-section in FIG. 6, in a direction transverse to the axis of the exchanger. These guides include peripheral portions 34 seating snugly against the circular walls of the casing 17, intermediate guide surfaces 35 and a central guide 36, the guides 35 being forked to embrace the clamp bolts 21. Each guide element is formed in two parts, as shown in section in FIG. 5, in the lengthwise direction of the main axis of heat exchanger, being arranged divergently from the inlet and outlet connections 31, 32 so that fluid admitted for example through the connections 31 is distributed uniformly to enter the spaces between the walls of six heat exchanger elements 8, a second fluid being thus caused to flow in parallel through said six units, the fluid passing through the space between the adjacent walls of each pair of elements, sweeping over the outer surfaces of the tubular members 9.

The fluid flowing out at the base of the first six units 8 is then diverted by means of a curved guide having the general configuration indicated by the dotted line 34 in FIG. 5 to cause said liquid to flow upwardly through the other six elements 8 towards the other connection 32, the fluid being collected through the guide elements 33 with the guide surfaces 34, 35, 36, as best shown on FIG. 6.

The invention is not limited to arrangements where the second fluid is caused to flow through any particular number of heat exchanger elements 8 in parallel nor is it limited to an arrangement in which the second fluid flows downwardly through half the elements and then upwardly through the other half of the elements and incorporating adjacent inlet and outlet connections 31,

FIGS. 7 and 8 illustrate alternative embodiments, applicable particularly to the rectangular exchanger elements shown in FIGS. 1 to 3 and described in more detail hereinafter, wherein the second fluid is caused to pass alternately upwardly and downwardly several times successively and in which the fluid traverses two heat exchanger elements in parallel in each case. Obviously an arrangement of this general character may be applied, according to particular requirements, to a construction of heat exchanger such as is shown in FIGS. 5 and 6.

Referring now to FIGS. 7 and 8, it will be seen that the rectangular heat exchanger elements 8 are located within a rectangular tubular casing 41 having a flange 42 at one end to which a tubular pipe connection 43 is bolted by means of a fastening bolt 44.

The pile or block ofelements 8 is located between end plates 45 which at one end may be slidably sealed within a tubular casing part 46 of the pipe connection 43, the

pile of elements 8 being fixed in position by means of fastening bolts 47.

The casing 41 is somewhat larger than the elements 8 along one axis to provide spaces above and below the exchanger elements adapted to receive fluid guide elements 48 preferably formed of moulded plastics mate rial. A fluid .connection 49 is provided in a side wall of the casing 41 and the guide element 48 positioned beneath the connection 49 is somewhat wider than the other elements 48 and is provided with a duct 51 permitting fluid to flow towards or away from the two terminal elements 8 in parallel. The guide elements 48 are provided with channels 52 and ducts 53 so that fluid passing towards or away from one pair of elements is diverted to flow in the opposite direction within the next two elements and so on in sequence so that the fluid successively traverses pairs of elements 8 in series in flowing from one end of the pile of exchanger elements to the other, said other end, not shown on FIG. 7 of the drawings, being provided with a connection similar to the connection 43.

The elements 48 are traversed by the fixing bolts 47 and are provided with guide fins or webs 54 to ensure a smooth fluid flow from one pair of elements 8 to the next.

Comparing the construction shown in FIGS. 7 and 8 with that shown in FIGS. 5 and 6, it will be seen that in the latter case the fluid flows through six elements 8 in parallel and traverses two of such groups before leaving the exchanger, whereas in FIGS. 7' and 8 the fluid traverses two elements 8 in parallel and then passes in sequence in opposite directions through other pairs of elements 8 before leaving the exchanger. The precise design adopted will depend on local conditions, the arrangement shown in the two embodiments being intended to represent heat exchangers for operation under somewhat diiferent conditions.

Obviously the arrangements shown in either group of figures can be modified to allow the fluid to flow through any number of elements in parallel and. to pass through two or more groups of such elements in opposite directions alternately in passage between the inlet and the outlet.

The exchanger elements and heat exchangers so far described are particularly suitable for liquid to liquid exchanger systems or, in the case of FIGS. 5 and 6, to gas to gas or gas to liquid where both fluids are circulated under applied pressure. In the case of radiator type heat exchangers where one component is air at substantially atmospheric pressure, that is without any high degree of force circulation, the alternative form of heat exchangers shown in FIG. 9 are particularly suitable. In this case a heat exchanger element is shown having the configuration indicated on FIGS. 1 to 3 being open at the two edges 10 and closed at the other two opposite edges 11. The series of tubular members 9 are in this case replaced by ducts 55 which are of elongated form and of sinuous configuration in plan. These ducts are, just like the tubular members 9, formed integrally with the front and rear walls of the exchanger element, and said ducts are bounded by raised marginal portions 13.

Preferably the ducts are arranged so that the peaks of the sinuous configuration thereof enter the depressions of adjacent ducts so that there is no direct or lineof-sight air flow path between adjacent ducts 55, the air or other gas being thus caused to maintain intimate contact in passing from one edge 10 to the other in the direction of the arrow A. The air flow passageways thus formed between the adjacent ducts 55 are preferably designed so as to be of constant section throughout from one end to the other and it will be found that this necessitates an arrangement of the ducts 55 such that the flow passage for the liquid varies in width at different points of the sinuous configuration of the ducts 55 but this is not a matter of any substantial importance because the 7 direction of flow of liquid is transversely to the plane of FIG. 9 through the ducts 55, whereas the direction of flow of air represented by the arrow A is in the plane of the drawing and along the space formed between adjacent ducts 55.

Conveniently each of the ducts 55 terminates at the edge from which the air passes outwardly of the units by straight parallel sections 56 which assist in obtaining smooth air flow on leaving the exchanger elements.

As in the embodiments described with reference to FIGS. 1 to 3 and 6, plastics filler strips may be inserted into the edges of the units 8 adjacent to the closed edge parts 11 thereof, and, of course, the arrangement shown on FIG. 9 is not limited to the use of exchanger elements of rectangular form of the general character shown on FIG. 4 of the drawings.

The elements shown in FIG. 9 may conveniently be provided with apertures 57 near each corner for the passage of fixing bolts whereby a number of such elements may be fastened together conveniently with jointing means or sealing means between adjacent rim parts 13, such fixing bolts further serving to attach end plates 58 to the assembly for attachment to flow and return pipes 59 as shown in FIG. 10. The open edge sections 10 are, however, entirely unobstructed to allow free flow of air through the passageways between adjacent ducts 55.

What I claim is:

1. A heat exchanger of the cartridge type, comprising an outer casing and a plurality of heat exchanger elements each comprising opposed parallel faces, a series of integral tubular members extending between them and having openings in the two faces, and having smooth peripheral portions for assembly of adjacent elements in facial contact at such peripheral portions only, to provide flow chamber within and bounded by said peripheral portions, said elements being assembled such that the tubular members of adjacent elements are not axially aligned, whereby sinuous flow paths are provided, the outer perimeter of each element having closed sections and intervening open sections, and ductways in said casing for admission of a first fluid to the elements which moves transversely through the tubular members of successive elements in a sinuous path and through the peripherally closed chambers between adjacent elements, and means to cause a second fluid to pass via the open sections through the spaces defined between the parallel walls of each element.

2. A heat exchanger according to claim 1, comprising an outer casing having inlet and outlet means for a first fluid, said inlet and outlet means being disposed at the two ends to cause fluid to flow transversely through the tubular members of each element in turn and from one chamber to the next and further inlet and outlet means for a second fluid, said latter means opening into passages leading peripherally towards the elements, said casing further including guides to cause said second fluid to flow successively through groups of elements in a control path.

3. A heat exchanger according to claim 2, comprising an inlet for the second fluid with a flow duct to direct the incoming flow to a first n elements and a series of successive guide ducts to cause the fluid to flow from the first n elements into the next n elements in the opposite direction and so on in succession until the second fluid has traversed all the exchanger elements.

4. A heat exchanger according to claim 1, further comprising means to hold the several elements in rigid assembly with the open sections of all the elements in alignment and open to the atmosphere.

5. A heat exchanger according to claim 1, further comprising means to hold the several elements in rigid assembly with the open sections of all the elements in alignment and means to control the admission and outflow of a gaseous medium towards and away from the said open sections.

6. A heat exchanger according to claim 1, comprising a plurality of heat exchanger elements, each such element comprising tubular members in the form of parallel elongated ducts of sinuosu form as seen perpendicular to the parallel faces and said elements having open sections adjacent the tenminal ends of all said ducts and a holder for said elements having inlet and outlet means for a first fluid which is caused to flow transversely through all said elements and through said ductways transversely to the length thereof and means to admit a second gaseous fluid to said elements to pass into and out of said open sections through sinuous passageways defined between adjacent ducts.

7. A heat exchanger assembly comprising an outer casing and a plurality of heat-exchanger elements, each such element comprising a thin-walled boxlike structure having opposed parallel walls, integral tubular members extending between said parallel walls and having a length substantially equal to the distance between the outer faces of said parallel walls and terminating flush and integrally with said outer faces, said elements having smooth pe ripheral portions for assembly of adjacent elements in facial contact at such peripheral portions only, to provide flow chambers Within and bounded by said peripheral portions, said flow chambers affording communication between the tubular members in adjacent elements, said elements being assembled such that the tubular members of adjacent elements are not axially aligned, whereby sinuous flow paths are provided, two opposed parts of the outer perimeter of each element being open and unobstructed to provide for circulation of fluid within said heat-exchanger elements and in contact with said tubular members, while other parts of the outer perimeter of each element embody peripheral closing walls and flow ducts within said outer casing to admit the fluid for circulation within said heat exchanger elements.

8. A heat exchanger element according to claim 7, of four-sided form in which two opposite side edges are open and the other two edges are closed.

9. A heat exchanger element according to claim 8, wherein each element is of rectangular form.

10. A heat exchanger element according to claim 8, wherein each element has the shape defined by a circle intersected by two parallel chords on opposite sides of the axis so that such element has rectilinear parallel edge parts, said edge parts being open, and part-circular edge parts which are peripherally closed.

11. A heat exchanger element according to claim 7, wherein the tubular members are in the form of a plurality of parallel elongated ducts of sinuous form as seen in a direction perpendicular to the two parallel faces.

12. A heat exchanger element according to claim 11, wherein passageways defined between each adjacent pair of sinuous ducts are of parallel cross-section throughout the length of such passageways.

13. A heat exchanger element according to claim 11, wherein each duct is of sine-wave form as seen in elevation and the configuration of the sine-wave and mutual spacing of adjacent ducts is such that the peaks of each duct extend to a point lying beyond a line joining the peaks of adjacent ducts so that at no point of the passageways between the ducts is there a direct through or line-of-sight path for the fluid flowing along said passageway.

14. A heat exchanger element according to claim 13, wherein the passageways extend from near one edge to the opposite edge, both said edges being at open sections of the elements to permit direct flow of a gaseous medium such as air through all the parallel passageways of adjacently positioned elements.

15. A heat exchanger element according to claim 11, comprising a plurality of parallel elongated ducts each duct being of sinuous formation for the major proportion of its length and a minor proportion at one end which is straight to define a series of rectilinear parallel passage- P ways for outflow of a gaseous medium travelling in the lengthwise direction of the spaces between adjacent ducts.

16. A heat exchanger element according to claim 7, comprising tubular openings adjoining corner parts of the elements for the passage of fastening means interconnecting a plurality of such elements.

17. A heat exchanger element according to claim 7, comprising filler elements disposed Within each heat exchanger element adjoining the closed peripheral sections References Cited UNITED STATES PATENTS Hart 165-430 Melcher 165-467 Holm et a1 165-166 Norman et al 165164 Hedbom 165-166 Maddocks 165-167 thereof to cause fluid to flow through that zone of each 10 ROBERT A. OLEARY, Primary Examiner.

THEOPHIL W. STREULE, Assistant Examiner.

element bearing the tubular members.