US2092170A

US2092170A - Method of fabricating a finned heat exchanger

Info

Publication number: US2092170A
Application number: US56936A
Authority: US
Inventors: Richard W Kritzer; Anthony F Hoesel
Original assignee: Individual
Current assignee: Individual
Priority date: 1935-12-31
Filing date: 1935-12-31
Publication date: 1937-09-07
Anticipated expiration: 1954-09-07

Description

Se t. 7, 1937. R. w. KRITZER ET AL,

METHOD OF FABRICATING A FINNED HEAT EXCHANGER Filed Dec. 31, 1935 2 Sheets-Sheet 1 FIGZ ' INVENTORS.

FIG. 3

p ,1937. R. w. KRITZER HAL 2,092,110

METHOD OF FABRICATING A FINNED'HEAT EXCHANGER Filed Dec. 31, 1935 2 Sheets-Sheet 2 J I'NVENTOPS a w /5. FIIIGJZ".

Patented Sept. 7, 1937 UNITED STATES PATENT OFFICE Application December 31, 1935, Serial No. 56,936

.lClaim.

One of the objects of our invention is to fabricate a finned heat exchanger of continuous tubing, the parallel reaches of which are placed at very close centers.

Another of the objects of our invention is to provide a finned heat exchanger in which the tubing is firmly gripped by the fins.

A further object of our invention is to provide a finned heat exchanger, which necessitates a minimum amount of labor and machinery for the fabrication of the same.

Further objects of our invention include a finned heat exchanger having a very high rate of heat absorption.

Referring to the drawings:

Figure 1 is an isometric view, looking upward, of a fin coil embodying our invention.

Figure 2 is an elevational view of a fin as used in our invention.

Figure 3 is a plan view of a fluid conduit used in our invention.

Figure 4 is a vertical cross-section along line A-A, Figure 1.

Figure 5 is a cross-section along line BB,

Figure 4.

Figure 6 is a cross-section of a return bend of the fluid conduit, Figure 3.

Figure 7 is a cross-section along line CC, Figure 6.

Figure 8 is a cross-section along line D--D,

Figure 6.

Figure 9 is a modification of the fluid conduit shown in Figure 3.

Figure 10 is another modification of the fluid a5 conduit shown in Figure 3.

Figure 11 is a cross-section along lines EE and F-F of Figures 9 and 10, respectively.

Figure 12 is a diagrammatic illustration showing a certain manner of pressing the tubing into 40 the fin apertures.

In the drawings:

Figure 1, a finned tube heat exchanger I, comprises a fluid conduit 2 having an inlet 3 and an outlet 4, between both of which are a 45' plurality of parallel reaches joined by return bends 5. Upon the parallel reaches .oi'the fluid conduit 2, and between the opposite return bends 5, a multiplicity of spaced apart fins 6 have a frictional engagement with thefluid conduit 2.

50 The upper edges, of the fins 6, have slots I which frictionally engage longitudinal bracing bars 8 driven into the slots.

. In Figure 2, a metallic fin plate 6 has slots 1 in each right-hand and left-hand upper corner.

55 The lower portion of the fin plate 6 has spaced return bends 5, is squeezed to a smaller dimension, at certain points, than the dimension of the conduit at the parallel reaches. The reason 10 therefor will be fully explained later.

In Figures 4 and 5, the lower portion, of a fluid conduit 2, is flattened-with ridges ii! angularly disposed relative to the length of the parallel reaches of the fluid conduit 2. Fluid wells l5 l3 lie between adjacent ridges l2.

In Figures 6, 7 and 8, the return bend 5 is formed, in a suitable bender, so that the section (J-C is of comparatively elliptical form, for a purpose to be explained later, and the section 20 DD is left of substantially its former shape, prior to the bending operation. The purpose of the change in section along lines D--D, as com- I pared to the section of C-C, is because that in bending thin walled tubing, to a short radius 25 and without the aid of internal devices for preventing inward buckling of the tube walls during the bending operation, the tube walls at the inner radius of the bend will buckle inwardly, unless the accumulated stresses are released at 30 given points. We have found that bending dies, made to all the humps shown at D-D, to form during the bending operation, allow us to form copper tubing, of .032 thick walls, to commercially acceptable return bends of radius to the center of the tube.

In Figures 9 and 10, we show return bends II, which are of the same cross-section as the tubing prior to bending. These return bends, on short radius bends, are generally made with internal former mandrels, during the bending operation, to prevent buckling of the tube walls at the bends.

In Figure 11 is shown a cross-section-of the conduit along lines E-E of Figure 9 and lines F -F of Figure 10.

In Figures 7 and 11, the cross-sections shown should have a width less than the dimension of the openings ID of the apertures 9 of the fin plate 6, Figure 2.

Having described the elements of the invention, we shall now describe the method of fabricating a coil in accordance with the invention.

Using outside diameter copper tubing, we bend it, with suitable dies as mentioned previu ously, to the form shown in Figure 3.

, to use we punch the apertures 9 with a round die having a diameter of .640", which is .015 larger than the outside diameter of the tubing used. The fin ,plate fi is so positioned in respect to the punching die that the aperture irbreaks' through the edge of the fin plate 6, as shown'in Figure 2, and produces an opening l0, which is approximately .531" 'in width.

Laying the formed conduit 2, of Figure 3, upon a flat surface, we then engage the return bends 5, at the right-hand side of FigureB, at the lines C of Figure 6, with the openings ID of the apertures 9 of the fin plate 6, Figure 2.

Since the openings ID are wider than the width In placing'the fins along the conduit, in their' proper spacedrelationship, We employ spacers, which we prefer made of a hardwood although any suitablematerial may be employed.

After the coil is assembled, we have a series of spaced fins, with a spacer. between adjacent fins. We now pass the assembly to a pressing machine, which is illustrated diagrammatically in Figure 12, in which a stationary table 15 provides a support for the finned tube heat exchanger I, which is step moved along in the direction indicated by the arrow. A die I6, hav: ing projections II onits working face, movedup and down at intervals, presses the tubing conduit 2 to a D shape having angularly disposed ridges along the fiat portion of the D shape as shown in Figures 1, 4 and 5 In pressing the tubing to a D shape, the tubing is pressed against the sides of the apertures '9 of the fin plates 6, and the fin plates 6 are firmly gripped by the conduit 2.

After the conduit tube 2 is pressed into all of the fins, the spacers, between adjacent fin plates 6, are then removed and the longitudinal bracing bars 8 are then driven into the slots I, which rigidifies the upper edges of the fins 8, making a comparatively solid assembly.

In certain cases, we may prefer to have return bends having a full tube cross-section and, in that case, we shall form the bends as shown in Figure 9, in which the section EE is slightly flattened to a dimension less than .531", allowing the fin plates to drop. onto, the conduit at these flattened portions, from which they can 1) moved to their respective positions.

In other cases, we may prefer to assemble the finsand spacers in a separate jig and then lay the conduit tube 2 into the assembly, engaging all the fin, plates 6 simultaneously, without the necessity of moving the pin plates to their respective positions after dropping them onto the tube at the flattened sections. In this case, we shall fiatten the entire length of the parallel reaches. joined by the return bends, as shown in Figure 2, to a dimension less than .531", which is the width of theopening II) in the fin plates 6, Figure 2.

While we have described preferred forms of the invention, it is understood that departures from the same may be employed without departing from the spirit and scope of the invention, which is limited only to the following claim.

We claim:

The method of manufacturing a. heat exchanger which comprises preforming a conduit with parallel courses joined by return bends,

punching fin plates with apertures breaking through an edge of the fin plates, the said apertures having a narrower width at the said edge than the aperture width at some point within the said fins, deforming the said conduit to a width-v