US1958899A - Heat transfer apparatus - Google Patents

Description

May 15, 1934. J. E. MaCADAMS HEAT TRANSFER APPARATUS Filed June 50, 1931 2 sheets-Sheet l INVENTOR JZZ'v rd/Z/acAda 7725 MTQ,

ATTORNEY May 15, 1934. J. E. MacADAMS HEAT TRANSFER APPARATUS Filed June 30, 1931 2 Sheets-Sheet 2 INVENTOR J1;a mard/%zafdam$ hum W2,

ATTORN EY Patented May 15, 1934 UNITED STATES;

FATEN'F OFFICE- 2 Claims.

This invention relates to heat transfer apparatus and more particularly to such apparatus as is used in connection with the evaporation of liquid.

A primary object of the invention is to so construct an apparatus of this character that the resistance to heat transfer between the liquid container and the liquid to be evaporated will be decreased.

Another object is to cause greater numbers of adjacent bubbles to unite into single bubbles than would occur in a more open space, by this means momentarily reducing the liquid in contact with the metal at any small spot that may be under consideration to a film so thin as to break down practically all very smallbubbles which cling to the metal.

Another object is to provide an evaporating section comprising a hollow two-walled structure 20 with the walls arranged very close together whereby the gas bubbles liberated by evaporation will each contact both walls and become flattened causing them to coalesce.

Still another object of the invention is to provide an evaporating section for use in refrigerating plants composed of two plates spaced apart a very slight distance and fixedly secured to each other at intervals to form a hollow structure equipped with suitable openings for the introduction of liquid and the removal of gas, suitable means being provided for connecting the sections together and to connect them to supply and exhaust lines.

In carrying out these objects, the invention is susceptible of a wide range of modification without departing from the spirit or sacrificing any of the advantages of the claimed invention; there being shown in the drawings for illustrative A purposes a preferred and practical form, in 40 which:

Figure l is a perspective view of a plurality of connected heat transfer elements or sections constructed in accordance with this invention;

Fig. 2 is a side elevation of one of the sections;

Fig. 3 is a longitudinal section taken on the line 3--3 of Fig. 2;

Fig. 4 is an edge view of one of the elements or units shown applied with a separate portion in section to illustrate the connection with the discharge pipe;

Fig. 5 is a vertical section taken on the line 5--5 of Fig. 2;

Fig. 6 is a similar view taken on the.line 6-6 of Fig. 2; V

Fig. 7 is a detail sectional view showing one of the couplings used for connecting two discharge pipes to each other and with one of the evaporating units;

Fig. 8 is a similar view showing another form which is used, in elevation;

Fig. 9 shows still another form of coupling; and

Fig. 10 shows still anotherform of coupling.

In the embodiment illustrated in Figs. 1 to 6 the heat transfer units or sections 1 are individually shown in Figs. 2 to 6 and are each composed of two thin plates 2 and 3 of steel or other suitable metal. These plates are provided at suitably spaced intervals with hollow struck out tits 4, those on one plate facing in one direction and those on the other in the opposite direction so that when the plates are assembled these. tits will operate as spacers. The tits 4 of one plate are preferably arranged in staggered relation to those of the other plate and are shown uniformly distributed throughout the entire area of the plate so that when the plates are assembled the tits contact the flat portion of the opposed plate I and are spot welded thereto as shown at 5. This 50 arrangement of the tits and the welding of them to the complementary plate provides for the supporting of one plate by the other and renders each unit area distinctive unto itself as to stress and strain and permits the whole area to be extended indefinitely without increasing the strength or thickness of the material or the strength of the supporting point.

The two plates 2 and 3 are sealed together around their edges at 6 forming a thin shell of any desired area.

Each section has a fluid inlet '7 and an outlet 8 suitably located for the attachment of con-' nections for the entrance and discharge of the operative fluid as will be hereinafter more fully I described.

The width or thickness of the liquid chamber formed between the two plates 2 and 3 is least at the bottom margin of the section at 10a, Fig. 6 and gradually increases in thickness or width 0 as it approaches the top as is shown clearly in Figs. 4, 5, and 6. The thickness near the lower margin of the chamber should be such as to permit the entrance from distribution channel 10, (hereinafter described). of that quantity of liquid which will be evaporated by the area above. This amount varies with the height of the section and the temperature difierence. The temperature difference may vary considerably in any given installation and between difi'erent installadifiicult to maintain in manufacture.

tions. It is therefore impossible to provide the correct spacing to meet all conditions and in many cases the spacing would be so small as to be It is desirable, therefore, to establish for each height of plate a purely arbitrary width of separation of the walls at 10a the point of communication with channel 10. This width may be slightly greater than the ideal without sacrificing any of the qualities or merits of the invention.

While the entrance opening '7 is-located at the bottom of the chamber and the discharge opening 8 at the top at diagonally opposite corners it is of course to be understood that these openings may be changed as to location if found desirable.

It is of course understood that the plates 2 and 3 are substantially alike the only differences being those required to make each the reverse of the other so the two will comprise a matched pair.

Along the top and bottom edges of the sections 1 are formed substantially tubular distribution channels 9 and 10. Leading downward from the outlet opening 8 is another channel 11 to facilitate any return flow within the section. To add mechanical strength the separation of the plates may be increased near the openings 7 and 8. The channel 11 may increase in thickness or width from the bottom toward the top as is shown clearly in Fig. 4 as does also the space between the plates, the nipples or tits 4 controlling the distance between the plates. The space between these plates is generally a very small fraction of an inch. The space between the plates at the lower portion thereof is about one one-thousandth or between one one-thousandth and one two-thousandths part ofthe vertical height of the section 1. From this point the walls gradually separate toward the top so that the space at the top is from twelve to fifteen times the width at the bottom. I

The close spacing of the plates results in a vigorous motion of the operating fluid which is comparable to violent boiling but having two distinctive features: first, it takes place with a much smaller heat supply than is possible in any other type of container known; and second, all of the gas liberated gathers in relatively large pockets which are kept in contact with the active surface as they move toward the outlet opening. These gas pockets gather in the bubbles which cling to the active surfaces thereby removing them much sooner than they would be liberated under ordinary conditions. The ultimate result of this action is that with a given difference in temperature between the external fluid and the evaporating liquid the total heat transfer from outside to inside will be greatly accelerated.

The tapered spacing of the plates has only a very small modifying effect on the motion of the operating liquid, this motion being due, as stated above, to the close spacing of the plates and would be present if the plates Were parallel or even closer together at the top than at the bottom, provided the maximum distance between the plates is adjusted to the amount of gas available at any point. The function of the tapered spacing is to provide easier means by which the liquid suspended above the growing gas pockets may drop into lower parts of the section and may cause the sub-division of the pockets to secure more frequent wetting of the active surfaces and to allow a more ready discharge of gas from liquid at the channel 9 so that liquid spray will not be carried into the outlet port 8.

' sleeve end forming a tight joint.

This action is inherent in a section of any size from one of a few square inches to many square feet if the separation of the plates be determined by the relations set forth above.

' The thickness of the plates 2 and 3 and the spacing of the supporting points or nipples 4 are determined by the pressure to be used in service while the size and shape of the supply and discharge openings aside from 'being adequate for the purpose, is affected somewhat by the design of connection used. The sections may be used singly or in groups. 7

One means of connecting the sections 1 into groups is shown in Fig. 1 in which the liquid supply tube 13 is inserted into or through the lower opening 7 and the discharge tube or pipe 14 is threaded through the upper opening 8 of the section. The tubes or pipes 13 and 14 which pass through the openings in sections 1 are secured to such sections by welding or other suit able means. These tubes are provided with apertures 15 which bring the fluid chambers of the sections into communication with the tubes. The ends of the tubes 13 and 14 are. shown threaded and they may be closed, or left open for connection to other groupsof sections. It is of course understood that any desired number of sections may be included in a group, seven being shown in Fig. 1 and the distance between the sections ods are shown for providing the supply and.dis-,

charge openings with various individual types .of connection whereby any number of sections may be connected together at will without being permanently welded into a group. In

"1 two pipe ends 16 and 1'7 are shown one having an internally threaded socket to engage the ex-- teriorly threaded extension of the other pipe between which ends the section 1 is inserted. Suitable gaskets 18 are provided to render an air tight connection at this point and the extension of pipe 17 is provided with apertures 19 which communicate with the interior of section 1.

. In the form shown in Fig. 8 the section 1 has welded at the opening therein two short tubu lar connections 20 and 21, the outer ends of which are provided with what are known to the trade as ammonia flanges 22. These flanges cooperate with similar flanges 23 on the ends of tubes or pipes 24 and 25. These flanges are secured together by a suitable bolt 26 and have gaskets arranged between them to provide a fluid tight connection.

In the form shown in Fig. 9 the section 1 is provided with an inserted nipple 28 which is provided with a right hand thread at one end and a left hand thread at the other. A coupling nut 29 also having right and left hand internal threads draws the nipples of adjacent sections together. A gasket 30 is arranged between the ends of the nipple and this gasket must be confined to prevent extrusion and shear shoulders are here shown as the means of accomplishing this. In Fig. 10 a section 1a is shown into which before welding the plates 2 and 3 together there is inserted a nipple 31 having a central shoulder 32, externally threaded ends 33 and 34 and inwardly projecting lugs 35 by means of which a sleeve 36 and the nipple 31 may be tightened together. This tightening clamps the edge of the plate 2 or 3 between the shoulders 32 and the sleeve 36 where a narrow seat 37 is formed on the These various forms of connections are shown and described to illustrate how the sections may be used in connection with various arts to which the sections are. adaptable and whereby any amount of surface may be displayed in almost any manner according as the particular use may require.

In this heat transfer device the gist of the invention resides in the relation of the spacing between the walls'and the vertical distance from the inlet distribution channel to the outlet channel as above described, This relation does not involve any consideration of the horizontal dimension of the section which has no bearing on the matter.

The vertical height of a section may be greater or less than the horizontal dimension. It may be curved about a vertical axis or, within limits, about a horizontal axis. For special purposes one of the plates 2 or 3 may be left entirely smooth and flat, the other being formed with tits 4 to the required number and with all openings and channels which ordinarily would be provided on both.

I claim: v

1. A heat transfer device for. the evaporation of liquid comprising a container composed of two opposed walls arranged re?atively close together and form'ng a sheet-like fluid chamber between them, said chamber having an opening for the introduction of liquid formed at a point along the lower edge of the container, 9. distribution channel extending along said lower edge, the spacing of the walls being such that the inlet of the fluid to the sheet-l'ke space from the distribution channel shall be sosmall as to allow free entrance only of such an amount of fluid aswill be evaporated in its passage to the upper edge of the container, the space between the walls being gradually widened upward to provide for the free flow of vapor toward the upper portion of the container, said container having a gas collecting channel and discharge opening at some point close to the upper end thereof.

2. A heat transfer devicefor the evaporation of liquid, comprising a container composed of two opposed'walls arranged relatively close-together and forming a sheet-like fluid chamber between them, said chamber having an opening for the introduction of liquid formed at a point along the lower edge of the container; a distribution channel extending along said lower edge, the lower edges of said walls being spaced apart from one-thousandth to one two-thousandth part of their vertical dimensions, so that the inlet of the fluid to the sheet-lire space from the distribution channel shall be so small as to allow free entrance only of such an amount of fluid as will be evaporated in its passage to the upper edge of the container, the space between the walls being gradually widened upward to provide for the free flow of vapor toward the upper portion of the container, said container having a gas collecting channel and a discharge opening at some point close to the upper end thereof.

- JESSE EDWARD MACADAMS.

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