US1975889A - Heat exchanger and process of making the same - Google Patents

Description

F. A. WHITELEY 1,975,889 HEAT EXCHANGER AND PROCESS OF MAKING THE SAME Fild June 22, 1931' 5 Shets-Sheet 1 Inward-or;

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F. A. WHITELEY HEAT EXCHANGER AND PROCESS OEMAKING THE SAME Filed June 22 1931 5 Sheets-Sheet 4 I/ 2 f. n l/ 6 a F IRM t IE N Oct. 9, 1934- F. A. WHlTELEY 1,975,839

HEAT EXCHANGER AND PROCESS OF MAKING THE SAME Filed June 22, 1931 s Shets-Sheet 5 Inventor:

I Patented Oct. 9, 1934 HEAT EXCHANGER AND PROCESS OF MAKING THE SAME Frank A. Whiteley, Minneapolis, Minn.

Application June 22, 1931, Serial No. 545,940

7 Claims.

My invention relates to the process of making heat exchangers. It is the object of my invention to provide a process of making heat exchangers comprising a multiplicity of thin metal plates positioned close together but separated by narrow spaces and held secured in position by a multiplicity of small tubes extending at right angles through all of said plate", each of the tubes having its metal fused integrally into the metal of each of the plates. When a heat conveying medium is circulated through the tubes and air is circulated through the spaces between the plates it will result in rapid transference of heat one way or the other to the heat-conveying medium.

It is a principal object of my invention to enable the heat exchangers made by the process herein referred to to be used in connection with cooling or refrigerating systems wherein the heatconveying medium is a compressed gas expanding in the tubes and heat is withdrawn from the air or fluid contacting with the plates. But the heat exchanger is equally applicable where the heat-conveying medium is steam or hot-water or gases of combustion and the transference of heat is in the opposite direction and it is taken from the medium and added to the air circulating through the plates.

It is a further object of my invention to provide a process wherein the fin plates of a suitable shape and size are perforated with a number of apertures and are stacked with the apertures in alinement and with divided separators between the plates, the separators being formed of a metal having a materially higher fusing point than that of the plates, and having apertures of larger cross-sectional area than the apertures in the plates, and holding in the chamber formed by the alined apertures of plates and separator tubes 40 formed of the same metal as that of the plates or of metal having the same fusing point, placing within the tubes a filler rod of a metal having a higher melting point and greater coefficient of expansion than the metal of the tubes, and pour- 45 ing molten metal of the same fusing point as that of the tubes and the plates into the chamber around the tubes, whereby the tubes and the edges of the plates around the apertures will be fused together. It is a further object of my invention to fill said tubes, prior to casting, with material which will not fuse when the tubes are fused and which filling material will be withdrawn after the casting operation has been completed in the manner of removable cores employed in casting so as to leave a hole or channel extend ng through said casting into which the tubes and the edges of the fin plates have been fused.

It is a further object of my invention to provide chambered headers into which the tubes extending through the assembled stack of plates, as hereinbefore referred to, will project, and using the chamber of. said headers as a trough for guiding the molten metal into the spaces about the tubes and thereafter as a manifold connecting with all of the tubes.

It is a further object of my invention to make heat exchanger units of the above-defined type each having headers with chambers of a multiplicity of tubes opening into each of said chambers and to connect together a multiplicity of said units through said headers so that the heatconveying fluid will circulate successively through the desired number of said units.

The full objects and advantages of my invention will appear in connection with the detailed description thereof, and the novel features of the invention will be particularly pointed out in the claims.

' In the drawings, illustrating an application of my invention in one form,--

Fig. 1 is a side elevation view and Fig. 2 an end elevation view of a rack for stacking the sheets to aline the apertures and assemble the tubes and separators therein. Fig. 3 is a sectional end elevation of the rack shown in Fig. 2 with allparts s5 assembled ready for the pouring of the metal. Fig. 4 is a sectional elevation of parts of what is shown in Fig. 3 on a larger scale with half of the metal poured. Fig. 5 is a view similar to Fig. 4 after the unit has been inverted and the other half of the metal has been poured. Fig.

6 is a side sectional view of the rack when the parts have been assembled therein showing how it is clamped together for preheating. Fig. '7 is a view similar to Fig. 6 showing the parts after the first pouring of molten metal and when they have been inverted for the second pouring. Fig.-

8 is a plan view of one of the metal plates showing the apertures formed therein. Fig. 9 shows one of the tubes adapted to be positioned in said apertures. Fig. 10 is a longitudinal sectional plan view and Fig. 11 a transverse sectional view of one of the header boxes. Fig. 12 is a perspective view of the closure cap for the header box. Fig.

13 shows a skeleton clamp top used in clamping the parts together for moving and heating. Fig;

14 is a plan view of one of the divided separator members employed in building up and holding separated the stack of fin plates. Fig. 15 is a view of the rod to be threaded into the base 1 member and to provide means for clamping the assembled stack together. Fig. 16 is a plan view of the special copper separator plate which divides the casting operation into two parts. Fig. 17 illustrates one of the copper-filled rods. Fig. 18 is a transverse section of one of the exchanger units taken across the plates and the header members and through one of the apertures showing the construction in its completed form. Fig. 19 is a transverse sectional view on lines 19-19 of Fig. 18. Fig. 20 is a transverse sectional view taken on line 20-20 of Fig. 18. Fig. 21 is an edgewise sectional view along one of the tubes and through one heat exchanger unit and parts of adjacent units showing the manner in which they join together with an air-separating plane. Fig. 22 is a sectional elevation taken on line 22 of Fig. 24 with some parts broken away and in section showing arrangement of an enlarged heat exchanger formed of a multiplicity of individual units secured together and housed for controlling the circulation of air therethrough. Fig. 23 is a side elevation of the parts shown in Fig. 22 with the side casing removed and in section. Fig. 24 is a top plan view of the organization shown in Fig. 23. Figs. 25 and 26 are longitudinal and transverse sections showing a connecting end union of two of the header members. Fig. 2'7 is an end illustration of a separator plate.

A base member 10 is provided having rigidly secured thereto a suitable number of posts 11 each carrying a spindle 12 of smaller diameter than the posts and preferably milled out of the same shaft of metal so as to leave a shoulder 13 on each post. Clamped at the corners of the base member-10 by means of strips 14 and bolts and nuts 15 are angle pieces 16 which may further be held in rigid position at a point partway up their length by surrounding straps 17. The entire organization comprises a rack with vertical and parallel corner guides for assembling the pieces comprising my invention as hereinafter recited. The several posts 11 are adapted to receive upon the extended spindles 12 the ends of tubes 18 such as illustrated in Fig. 9, the said tubes preferably being of some metal of a relatively low melting point, as aluminum, and fitting snugly about the spindles 12. After the tubes 18 have been assembled on the spindles 12 a header casting 19 of the form shown in Figs. 10 and 11 and embodying a multiplicity of apertures 21 positioned and shaped as indicated in Fig. 10 is positioned upon the rack with the spindles 12 extending through the apertures 21, and the opening 22 in the top of said casting being turned down, the engagement of the posts 11 with the walls of opening 22 fixing the casting in proper position, in which position also, as clearly shown in Fig. 4, the apertured bottom wall 23 of the casting member will be held above the shoulders 13 and the lower ends of the tubes 18 a suitable space, as indicated by numeral 25.

A separator plate 26, as shown in Fig. 14, is formed of two sections, 27 and 28, the sections when assembled appearing as shown in the figure with a multiplicity of elongated apertures 29.

of exactly the same location and shape as apertures in the fin plates hereinafter to be described. These apertures are in the bottom wall 23 of the castings 19, there being shown in the particular example in both the wall of the casting and the separator plate nine of such holes or apertures arranged in a zigzag staggered rela tion corresponding to the nine posts 11 and spindles 12 positioned in a similar zigzag staggered relation. The division of the two sections of the separator plates occurs along lines 30 which run from front to rear of adjacent apertures, the dividing line being of such a nature that the two sections can be drawn apart without any binding effect from adjoining margins. The separator plates are formed of metal having a materially higher fusing point than the metal of the tubes and fin plates which make up the heat exchanger, as iron for the separator plates where the heat exchanger plates are aluminum. One such heat exchanger plate 32 is shown in plan in Fig. 8. This embodies a multiplicity of apertures 33 similar and similarly positioned to the apertures 29 of the united separator plates 26 except that the cross-sectional dimensions of the apertures 33 are somewhat less than of the apertures 29, so that when separator plates and fin plates are assembled in the stack the margins of the fin plates about the apertures will project a certain distance beyond the margins of the separator plates 26, as clearly shown in Figs. 6 and '7, and the margins of the apertures through the fin plates will coincide in vertical alinement with the margins through the bottom wall 23 of the casting 19. The shape of the apertures 21, 29 and 33 may be varied as desired, but I have found it to be an effective shape to make them roughly pear-shape in crosssection, which performs the advantageous function of giving extra flow space for the molten metal to pass down to the bottom of the cavity formed by the stacked fin plates and separator plates.

In forming this stack, a separator plate is laid in the rack so that its two sections embrace the assembled tubes 18, and its corners 34 engage in the corner guides of the angle uprights 16. A fin plate 32 is then dropped down on the separator plate, and by alternating separator plates and fin plates the structure is built up to a point which will constitute the center of the heat exchanger, wherein the successive apertured members comprising separator plates and fin plates will form chambers about the tubes 18 which open directly through the bottom wall 23 of the header members 19. At the central point of the heat exchanger a special transverse separator plate 35 is laid into the stack. This will be formed of metal having a materially higher melting point than that of the tubes and fin plates such as copper or iron, and it will have therein apertures 36 circular in crosssection and positioned so as to fit closely around the upstanding tubes 18, thus blocking the chamber 37 below and forming the bottom wall of a second chamber 38 above the separator plate 35, which chambers are formed by the adjacent margins or edges of the fin plates and separator plates surrounding the apertures therethrough. The special separator plate 35 not only forms a division wall between chambers 37 and 38, but it has the further function when positioned with its corners 39 engaging the vertical guides 16 of adjusting and holding properly positioned all of the tubes 18. As clearly shown, in Fig. 16 the separator plate 35 is made wider than the fin plates 32 to form, when assembled, extensions 40 and 41 which have a function when complete exchanger units are assembled to form composite units, as hereinafter described. The separator plate 35 also is provided with a lip or extension 42 at the end thereof which is used in assembling such a composite heat exchanger.

Upon the separator plate 35 additional sectional separators and fin plates are stacked up until the heat exchanger is formed of a requisite length. This length may vary according to the purpose for which the heat exchanger is used, a convenient length, and one which adapts itself well to the casting operation, being twenty-four inches with the separator plate 35 up to twelve inches from the bottom wall 23 of the head casting 19. When the structure has been built up to the desired height a head casting'19 exactly like the lower head casting is applied with its bottom wall 23 engaging a separator plate 26 and with its open top 22 projected upwardly, as shown most clearly in Fig. 6. A skeleton top member 43, as shown in plan in Fig. 13, then has its flange portion 44 seated in the top against receiving ribs 45 surrounding it, as clearly shown in Fig. 6. Bolts '46 of the type shownin Fig. 15 have their lower ends 48 threaded into extensions 49 at opposite ends of the base member 10, and these bolts pass freely through apertures 50 in ears 51 extending outwardly from the ends of the clamp member 43. By turning down nuts 52 on the threaded ends of the bolt members 46 the entire assemblage will be firmly clamped and held together with the several chambers 37 and 38 extending through the separator plates and fin plates opening. into the interiors of the casting heads 19 on each side of the member. The nuts 15 are then unscrewed, which releases the clamping members 14 and the comer guide members 16 which are removed from the rack. There are then inserted in each of the tubes 18 rods 53 which are shown at Fig. 17 and elsewhere, which, engaging with their lower ends the tops of the spindles 12, project outwardly within the chamber of the header 19, and fit with a reasonable degree of snugness inside of the tubes 18, and which are formed of a metal having a higher melting point than the melting points of the tubes and fin plates, and also preferably having a greater coefiicient of expansion. Where aluminum is employed. for tubes and fin plates I have found that copper rods are exceptionally efficient for this purpose. At opposite corners of the clamping plate 43 are thickened portions having apertures 47 of a diameter sufllcient to just take over the corner rods 53 (or 56), as clearly shown in Fig. 4 and Fig. 12, and since the clamping member 43 takes into the top of the header 19, this will hold the header in proper position relative to the apertures 21 in the bottom thereof and the tubes 18 projecting therethrough.

The heat exchanger unit is then ready for the pouring of metal to fuse the tubes 18 upon and to the marginal edges of the plates 32. Preferably the skeleton clamped together in the form shown in Fig. 6 will be preheated before the hot metal is poured. This will be done in a suitable oven for that purpose corresponding with standard foundry practice, in cases where preheating is desirable. A measured quantity of molten metal having the same melting point as that of the tubes and of the fin platesof aluminum where that is employedand heated to a temperature somewhat higher than the melting point, will then be poured through the opening 22 into the chamber inside of the casting head 19, as shown in Fig. 6. The amount of molten metal required will be determined in advance and it will only be necessary to pour that amount into the chamber of the header. This molten metal will flow into all of the vertical chambers 38 opening through the bottom wall 23 of the header 19,

filling said chambers down to the separator plate 35 and extending above their tops a predetermined distance to form when cooled a layer of cast metal 54 which with the end of the column of cast metal below embraces and binds to it the floor 23 of the header 19. Since there is a considerable number of such columns spaced all along the bottom wall 23 both crosswise and lengthwise the headers 19 will be integrally and very rigidly united with the tube columns 18, which in turn are integrally united with the fin plates 32. The header castings will be formed of metal of a higher melting point than that of the tubes 18 and fin plates 32, such as some form of bronze where aluminum is used, or iron, but the manner in which cast metal grips the walls 23 above and below makes them in effect integral.

As indicated at 54 in Figs. 4 and 5, the metal so poured will fuse into the, exposed walls of the tubes 18 and marginal edges of the fin plates 32, but will not be sulficiently hot to melt the separator plates 26 or the copper rods 53. After "the first pouring the lower part of theunit will be insulated so as to retain its heat while the metal which has been poured cools suificiently to be rigid. Thereafter the assemblage is inverted and the base 10 removed, withdrawing the spindles 12 from the tubes 18, which can readily be done where the tubes are of aluminum and the spindles of iron or steel, since the coefilcient of expansion of the aluminum is greater than that of iron or steel. Short filled rods 56 as shown in Figs. 5 and '7 are then inserted within the tubes 18 so as to occupy the places of he spindles 12, filling the tubes 18 to the ends of the filler rods 53, as shown in Figs. 5 and 6. In this new position a second quantity of molten metal is poured within the chamber of the header 19 and fills the chambers 37 opening thereinto down to the separator plate 35 and leaving a second cap 55 of cast metal at the bottom of the chamber in casing 19, as clearly shown in Fig. 5. The unit is then completely cooled. When that happens the filler rods 53 and 56 may readily be pushed out, as the copper of which they are composed will have expanded much greater than the aluminum tubes surrounding them, and will 'correspondingly contract in cooling, shrinking away from the aluminum tube. The divided separator members 26 are provided with projecting ends 58 and 59 with a V-shape notch 69 between them, as shown in Fig. 15. The nuts 52 will have been removed, releasing the clamping member 43 (in practice the nuts 52 will be somewhat released before the beginning of the casting of the metalpouring operation). The unit will be laid on its side and a wedge-shaped member driven into the V-shaped groove 60 between the extensions 58 and 59 on portions of the separator plates 27 and 28. A light blow of a hammer or mallet upon this wedge-shaped member will loosen all of the separator plates, which can be withdrawn on either side of the cast walls of metal surrounding the tubes. A cover plate 61, shown in Fig. 12, will'then be secured upon the ledge 45 surrounding the opening 22 into the header member 19, shown in Fig. 18, as preferably by welding ing header, tubes and plates. The tubes 18 will remain in position slightly expanded as to their inner bores 67, but in eiiect the walls of these tubes have become a part of the cast metal column indicated in its smaller size at of Fig. 19 and in its full size at 66 of Fig. 20. These cast metal columns are pear-shaped in cross-section excepting the last one, indicated at 68 and 69, which, to preserve the strength of the fin plates, are cast round. The air moves in the direction of the arrows in Figs. 19 and 20, contacting with the large side of the cast metal column first, and, because of its pear-shape tapering toward the other side, said air will tend to follow around close to said column. The unit is then complete and can be used in its finished form or assembled with other units in a manner hereinafter described.

Each header member will preferably have formed on one side an opening 62 surrounded by a threaded nipple 63 and on the opposite side a threaded boss 64, as shown in detail in Figs. 10 and 11, it being understood, however, that one or more connecter openings may be formed into the chambers 23 of the header members of such size and in such position as may be desired, either on the sides or at the ends thereof. By means of these connecter heads a multiplicity of units may be united to form a composite heat exchanger unit of large size suitable for employment in operating to cool rooms of houses or storage compartments. A preferred form of effecting the union of a group of exchanger units and assembling them in a casing adapted to circulate air for cooling purposes is illustrated in Figs. 21 to 26, inclusive. As there illustrated,

' six of the complete units are secured together side by side and six more end to end, as clearly shown in Fig. 24. The manner of securing the units side by side to provide ,for circulation of the heat-conveying medium successively through the different units of the first row of six such units is clearly shown in Fig. 22. As there illustrated, adjacent headers 19 have their oppositely-threaded nipples 63 brought together by ring nut 70, and the bosses 64 are correspondingly brought together by a ring nut 71, a tube '72 leading from the compressor or other device for causing circulation of heat-conveying fluid. By observing the relative position of the ring nuts and '71 in Fig. 22, it will be apparent that the fluid entering the chamber in the header at the a lower left-hand corner will rise through the tubes of the heat exchanger unit to the header chamber at the upper left-hand corner, will then go across to the next unit, from there down through the around end openings '76 and 7'7 are brought,

together by means of nuts and bolts 78. As shown in Fig. 26, this is done before the cap plate 61 is welded into position, and a similar method of fastening at the sides of the headers can be employed, if desired, by leaving 01f cap plates until the fastening has been completed, and then secure the parts together by means of bolts and afterwards welding on the cap plates. The complete circulation of the fluid through the composite heat exchanger may be traced from the designating letters of Fig. 24 in which the several units are designated from a to Z inclusive. Thus, the heat-conveying medium enters the bottom of unit a through pipe '72, goes through the tubes to the top, across to b at the top, to the bottom of b and across to c at the bottom, to the top of c and across to d at the top, to the bottom of d and across to e at the bottom, to the top of e and across to j at the top, to the bottom of f and endwise across to g at the bottom, to the top of g and across it at the top, to the bottom of h and across to i at the bottom, to the top of 12 and across to a at the top, to the bottom of 7' and across to k at the bottom, to the top of k and across to I at the top, to the bottom of l, and discharge through return pipe 79, thus completing the circuit.

The manner in which a separation of the composite exchanger of Figs. 22 to 26 is effected is best shown in Figs. 21 and 22. When two units are brought together side by side the edges of the fin plates 32 of one unit will theoretically contact and aline with'the edges of the fin plates 32 of another unit. In practice, however, this will not quite be true, as there will ordinarily be some offsetting at the edges. However, an effective seal to divide the heat exchanger into upper and lower portions is brought about through the copper separator plates 35. As shown in Fig. 27 these plates have the extensions 40 and 41 thereof bent laterally in opposite directions at and 81 which line of bend when two sections are assembled together will lie in the plane 82 of the ends of the fin plates, as clearly appears in Fig. 21. The effect of this is to cause the outer edges of the bent portions 40 and 41 to clasp with a spring pressure the first of the abutting separator plates 35, thus producing an effective air seal. To the tabs or projecting portions 42 of the separator plates a partition plate 82 is welded or otherwise secured whereby with a surrounding casing member 83, 84 upper and lower passages 85 and 86 are formed, the first above and the second below the partitions separating the heat exchanger. To the casing members 83 and 84 a front 8'7 and side walls 88, 89 are secured, forming an enclosed chamber. A blower introducing air into one of the chambers 85 or 86, as shown, into chamber 86, will force the air through the lower half of the heat exchanger, and in the chamber 90 the air will be reversed in direction as shown by the arrows passing back through the heat exchanger and to the passageway 85, from which it will be discharged to whatever space it is proposed to cool. In the form shown, adapted to be used as a refrigerating device, the heat exchanger is secured within the casing at a slight angle from the horizontal, so that condensate forming upon the fin plates will drain vapor into a trough 91 at the bottom of the chamber 90, from which it will discharge through any suitable pipe 92.

The advantages of my heat exchanger and the method of making the same will appear quite clearly from the foregoing description. The feature of primary importance is the production of a heat exchanger of the finned plate type wherein a large number of relatively small tubes pass through and are integrally united by f ing with all of the closely-spaced finplates, and all of the tubes open into the chamber of a single header member which is so constructed as to adapt the several units to be connected together to form composite units of anydesired size. The particular size of exchanger unit shown and described, and the particular showing of a group of such units united to form a composite unit are exemplary only, as in both of these particulars size and number may be varied within any limits desired to effect a requiredresult. It is peculiarly within the scope of purview of my invention to provide in exceptionally compact space, especially for use in cooling air, an enormous amount of heat exchanger surface. However, I do not wish to be limited to the use of the invention in large units or composite heat exchangers formed of a multiplicity of units, as the invention is excellently adapted for use in single units of any desired size. It is also within the scope of the invention to subdivide the chamber of the header castings into separate compartments so as to provide multiple circulation back and forth between headers in a single unit.

I claim:

1. A process of making heat exchangers which consists in arranging in alternation a stack of apertured fin plates and divided apertured spacer plates formed of metal having a higher melting point than that of the fin plates with all apertures in alinement, inserting a metal tube having a lower melting point than that of the spacer plates within. the chamber formed by all said apertures, filling the tube with material of higher melting point than the metal of the tube, and pouring molten metal of no lower-melting point than that of the fin plates and tube into the space around the tube.

2. A process of making heat exchangers which consists in arranging in alternation a stack of apertured'fin plates and divided apertured spacer plates formed of metal having a higher melting point than that of the fin plates with all apertures in alinement, inserting a metal tube having a lower melting point than that of the spacer plates within the chamber formed by all said apertures, inserting within the tube a rod of metal which will substantially fill the space within the tube and which has a higher melting point and greater coeflicient of expansion than that of the tube, pouring molten metal having a melting point at least as high as that of the tube and fin plates and lower than that of the rods and spacer plates into the space around said tube, and spreading and withdrawing the spacer plates and withdrawing the rod after the poured metal has cooled.

3. A process of making heat exchangers which consists in holding a multiplicity of elongated tubes in fixed relation, assembling about said tubes a multiplicity of metal fin plates having substantially the same melting point as the metal of the tubes and formed with apertures through which said tubes project of larger diameter than the tubes, holding said fin plates spaced by means having a melting point materially higher than that of the fin plates, and which provides apertures aboutthe tubesyggr than those through the fin plates so that edges bi thefin plates project into the chamber formed by aifofwheifi plates and spacing means, and pouring molten metal of no lower melting point than that of the fin plates and tubes into the chambers surrounding each of the tubes.

4. A process of making heat exchangers which consists in holding a multiplicity of elongated tubes in fixed relation, assembling about said tubes a multiplicity of metal fin plates having substantially the same melting point as the metal of the tubes and formed with apertures through which said tubes project of larger diameter than the tubes, holding said fin plates spaced by removable means having a melting point materially higher than that of the fin plates, and which provides apertures about the tubes larger than those through the fin plates so that edges of the .fin plates project into the chambers formed by all of the fin plates and spacing means, uniformly preheating the assembled stack of fin plates, separating means and tubes, and thereafter pouring molten metal of no lower melting point than that of the tubes and fin plates into the chambers about each of the tubes.

5. A process of making heat exchangers which consists in holding a multiplicity of elongated tubes in fixed relation each with an end projected through apertures in a wall of a header casting into a chamber within said casting, assembling about said tubes a multiplicity of metal fin plates having substantially the same melting point as the metal of the tubes and formed with apertures through which said tubes project corresponding with the apertures in the wall of the header casting and of larger diameter than that of the tubes, holding said fin plates spaced by removable means having a melting point materially higher than that of the fin plates and which provides apertures about the tubes larger than those through the fin plates so that edges of the fin plates project into the chambers formed by all of the fin plates and spacing means, and pouring molten metal of no lower melting point than that of the tubes and fin plates into the chamber of the header casting and in sufficient quantity to fill all of the chambers about each of the tubes and forming a layer of said molten metal over the bottom of said header casting.

6. The process of making heat exchangers which consists in holding a multiplicity of fin plates and the bottom wall of a previously-formed open-topped header box composed of metal having a higher melting point than that of the fin plates, all formed with a multiplicity of correspondingly sized and positioned apertures, so the respective sets of apertures have their edges in alinement, forming divided spacer plates from metal havinga higher melting point than said fin plates with conjoint apertures of larger diameter than the first-named apertures, and positioning said spacer plates between successive fin plates so as to leave exposed edges of the fin plates and of said bottom wall adjacent the spacer plate apertures, forming and holding removable members of higher melting point than said fin plates in said apertures, and spaced from the surrounding edges thereof and projecting into said header box, pouring molten metal in said header box to cast simultaneously a multiplicity of tubes integrally united'with all the spacer plates and connected and opening into the header box.

'7. The process of making heat exchangers which consists in holding a multipicity of fin plates and the bottom walls of two previouslyformed open-topped header boxes composed of metal having a higher melting point than that of the fin plates, all formed with a multiplicity of-correspondingly sized and positioned apertures, so the respective sets of apertures have their edges in alinement, forming divided spacer plates from metal having a higher melting point than said fin plates with conjoint apertures of larger diameter than the first-named apertures, and po== iti ning said spacer plates between successive fin m tes so as to leave exposed edges of the fin plates nd of said bottom walls adjacent the header box and then into the other, to cast simultaneously first the parts on one side of said separator member and then the parts on the other side of a multiplicity of tubes integrally united with all the spacer plates and connected to and opening into both said header boxes.

FRANK A. WHITELEY.

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