US2312313A - Evaporator - Google Patents

Description

March 2, A194,3. w. E. BELINE EVAPORATOR Filed OCT.. 17, 1941 3 Sheets-Sheet l WMO WWMNHZZOU Gttornegs MANI :Y

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`March 2, 1943. W. E. BELINE EVAPORATOR Filed Oct 17, 1941 3 Sheets-Sheet 2 (Ittornegs March 2, 1943. w, E; BELINE EVAPORATQR Filed OCT.. 1'7, 1941 3 Sheets-Sheet 3 0 O O 0890 o o0 OO 9000000 0o oooocoo MWL O Oo 0 00 0 Oog O O attorneys Patented Mar. E,

Application October i7, 1ML Serial No. 415,477

(Cl. (i2-126) i5 Claims.

This invention relates to evaporators and par ticularly to evaporator-s having a primary heat exchange surface through which the heat to produce evaporation is delivered to the lVolatile liquid to be evaporated and in which the off-fiowing vapor is subjected to a second heat exchange in the vapor ofitake by means of a second surface heat exchanger mounted in such oitake.

Generally stated, the fluid which delivers heat to the evaporator ows through tubes which are submerged in liquid retained by an embracing trough. This trough is mounted within the cyn lindrical shell enclosing the entire evaporator structure. The vapor, disengaged at the surface of the liquid in the trough, passes downward through the space between the trough and the enclosing shell, and there exchanges heat with a secondary exchanger, which may be of the finned type and which is mounted in such oitake.

The arrangement has a number of important advantages. In the first place, both heat eX- change surfaces may be enclosed in a single simple cylindrical shell. In the second place, the offtake is coextensive with the length of the shell and may readily be made of ample cross-sectional area, so that there are no localized areas of low pressure on the disengaging surface of the liquid undergoing' evaporation. This minimizes surging of the liquid and spouting of liquid which tends to occur at low pressure areas. As a consequence, priming is kept to a minimum, and if it occurs, occurs uniformly and moderately throughout the length of the evaporator.

The present application is subordinate to a companion application,4 Serial No. 415,476, led October 17, 1941, and the structure of the present application differs from that of the prior application chiefly in the presence of the secondary heat exchangerin 4the ofitake.

While the evaporator is adaptable to. a number of uses, it was devised primarily for use in refrigeration. Certain modern refrigerants such as Freon 11 (or F-il) and Freon 12 (or 1FL-12), the designations being accepted trade names, are characterized by the evolution of large volumes of vapor per ton of refrigeration. They are also characterized by miscibility of lubricating oil in all proportions therewith so that gravity separation to recover the oil is not practicable. F-ll. is

particularly characterized by the evolution of large volumes of vapor, and by a refrigerating cycle which requires only a rather narrow pressure range, so that rather small pressure losses between the evaporator andA compressor may ocn '-casion serious losses of emciency.

The evaporator hereinafter disclosed was developed for use in refrigeration in conjunction with a vapor superheater and oil recovery system described and claimed in the patent to Pownall No. 2,223,900, December 3, 1940. In order to develop special aspects for utility and to offer basis for certain claims directed to the refrigeration field, the invention is here described as embodied in a reirigerative evaporator connected to operate with F-12 on the iownall principle. It is to be understood, however, that the second heat exchanger, that is, the one mounted in the offtake, is not necessarily a superheater so far as the broad aspects of the invention are concerned.

A preferred embodiment of the invention intended for the specific use above set forth `will now be described with reference to the accompanying drawings, in which:

' Fig. i is a diagrammatic elevation of a typical refrigerative circuit including the evaporator here disclosed.

Fig. 2 is a longitudinal axial section of the evaporator with portions broken away to reduce the length of the View. No ns are illustrated on the tubes; The evaporator tubes preferably have thread-like integral fins and the superheater tubes are preferably similarly finned.

Fig. 3 is a perspective view of a sub-assembly comprising the trough and its attached defiector, and the superheater. ('I'he superheater fins are omitted). f/

Fig. 4 is a section on the line 4--4 of Fig. 2, showing the left hand header unit and the outlet connection of the superheater, the left. hand tube sheet for the heat exchange tubes and its sustaining grid for the tubes sheet.

Fig. 5 is'a section on the line E-i of Fig. 2. Fig. 6 is a section on the line G-- of Fig. 2

showing the right hand header unit of the super'- heater and the supply connection thereto.

Fig. 7 is a fragmentary view indicating iins on the tubes preferably used for the evaporator and superheater. This view shows how the tube ends are smooth and beiled out so that their outside diameter slightly exceeds the outside diameter of the fins.

As illustrated in Fig. 1, theevaporator indi- Y cated generally by the numeral ii applied to its enclosing shell is adapted to be included in a refrigerative circuit of the type disclosed in the Pownall patent.

The suction line i2 leads to the intake of compressor i3 which discharges compressed gaseous refrigerant through line i4 to condenser i5, in

the main evaporator inlet connection 2|.

which it is liquefied and from which it drains to receiver I5. Liquid line I1 leads from receiver I3.

The main supply of refrigerant to the evaporator ilows from line I1 through strainer I8 and diaphragm operated regulator valve I9 to As in the Pownall patent, the valve I9 is piloted or controlled by a small expansion valve 22 of the superheat controlled type. The thermal bulb 23 oi this valve is applied to the suction line I2 near its connection with evaporator Il, and is connected by the usual capillary tube 24 with valve 22.

A branch 25 leads from the liquid line at a point between strainer I8 and regulator valve I9 through ilow restricting orifice 23 to the line 21 which is connected both to the diaphragm chamber of valve I3 `and to the intake connection of valve 22. '113e dischargeconnection of valve 22 leads to evaporator inletl. A gage 28 indicates the pressure in connection 21 and enables the voperator to check the performance of the automatic control. A normally closed by-pass valve 29 permits operation oi' the evaporator under manual control incase of emergency.

The expansion control described is simply one of several known schemes for supplying liquid refrigerant to connection 2| at a rate so controlled that refrigerant entering suction line I2 will be slightly superheated.

As in the Pownall device, a portion of the liquid refrigerant fed to the evaporator II flows through the superheater. This superheater, hereinafter described in detail, is a finned heat exchanger in which the warm liquid refrigerant gives up heat to cold refrigerant vapor as the latter iiows toward the suction line I2. The supply flow is through the stop valve 3|, which is normally wide open to the superheater inlet con-A nection 32. The refrigerant passes thence through the superheater remaining in the liquid phase and reaches the superheater discharge connection 33. Thence it flows through regulating valve 34 and solenoid stop valve 35 to a secondary refrigerant inlet 35.

The rate of flow through the superheater is controlled at the exit end by adjusting the valve 34.. v The solenoid valve is controlled in any convenient way, so as to be open when compressor I3 runs, and closed when the compressor is out of action. The amount of refrigerant allowed to iiow through the superheater is less than the minimum demand of evaporator |I, so that there is always a supplementing flow controlled by valve I9 under the piloting action of valve 22.

The circuit above described is one typical environment in which the invention may be used to advantage, but this is adopted for purpose of at intervals in their length. These plates 40 are spaced at their edges from the trough hereinafter described and are sustained thereby.

The tubes 39'open at their ends into water boxes formed by the cupped heads 4| which are bolted to the stiffening rings 31 as shown. The water boxes are subdivided by webs 42 which may be variously arranged to provide for various numbers of water passes. The pattern of the tube sheets is indicated in Figs. 4-6 and the webs 42 align with certain of the radial blank spaces in the tube sheets and seat on gaskets 43 of suitable pattern interposed between the head flange and webs on the one hand, and the stiffening ring and tube sheet on the other.

The application of suitably webbed heads will permit arrangement for various numbers of water passes, according to familiar principles. Water inlet and outlet connections are indicated at 44 and 45 in Fig. 2. They are shown in dotted lines because they are forward of the plane of section in the particular three-pass arrangement here illustrated.

The Water tubes are in effect an extended surface heat exchanger and are arranged as a central core or bundle extending axially from end to end of the evaporator shell and so arranged as to leave an intervening space between the core and the shell.

All the water tubes 39 are embraced by the trough 46 whose general form is best indicated in Fig. 3. The ends of the trough are notched, as indicated, to form shoulders 41. The arcuate portions between shoulders 41 t closely within and are continuously welded to corresponding rings 31 and the portions beyond the shoulders 41. abut the inwardly presented plane faces of the rings and are welded thereto. Thus, the trough extends from tube sheet to tubesheet and is sustained by and connected liquid-tight to the stiffening rings 31, to which the tube sheets `are similarly connected.

A baille 43 connects one upper margin of the trough 45 with the shell so that an arcuate ofitake passage 49 is afforded, leading from the top of the trough, downward and beneath the trough and then upward on the opposite side of the trough to the suction connection 5|. More than explanation and without implying that the xtility of the features now to be described is limited to this particular environment.

Refer to Figs. 2 to 7. The arrangement of parts will first be described, after which the mode used to assemble the parts will be explained. The evaporator is arranged to cool liquid, for example, water or brine.

i The shell Il is cylindrical and at its ends is welded to the stiilening rings` 31 which are recessed in their outer sides to receive the tube sheets 38 which are brazed or welded to the corresponding rings.. The Water tubes 33 extend from tube sheet to tube sheet and are brazed to the tube sheets. They preferably have fine integral ns, but smooth tubes can be used. Sustaining plates 40 are used to sustain the tubes one such connection could be provided but one is sulcient, because the arcuate passage 49 is long enough to give satisfactory distribution and flow over the superheater which is mounted therein. The use ot the baffle 48 is desirable because it gives a single and rather long flow path but the baille can be omitted when the location of the suction connection 5| is such as to render this expedient.

- The connections 2| and 36 are in the form of tubes which extend across the passage 49 and communicate with the space within trough 43, I

beneath a perforated horizontal bale 52. Connection 2| is threaded into a nipple 53 and connection 33 is threaded into a nipple 54, each formed in the -bottom of the trough. Each connection is welded to shell I as indicated at 55,- 55.

A crow foot stiiener frame 51 is 'mounted in each ring 31 and is welded to the trough, but not connected with the tube sheet. It conforms to the radial blank areas of the tube sheet pattern and serves to sustain the tube sheet against gasket seating pressures and against water pressure when this exceeds evaporator pressure.

The superheater, as here illustrated, comprises seven passes, each made up of ten finned tubes. The number of passes, the number of tubes per asienta pass and the type of :uns are all subject to modi fication. The tubes extend between two suit ably chambered arcuate headers which are `sustained by and embrace the trough.

The headers appear at 58 and 59. ".ihey are large curved tubes plugged at their ends and each subdivided into four chambers by disc plugs. The plugs in header 58 are indicated at 6l (see Figs. 3 and 6) and those in header 59 at (F52 (See Figs. 3 and 4). The chambers are staggered in the two headers so that the tubes 63 afford zig-zag flow back and forth between the two headers. There are ten tubes in each of seven passes, the passes being connected in series, .as is clearly evidenced by Figs. 4 and 6. The number of passes and the number of tubes per pass are details of design, as are the iin spacingv and iin area.

All the tubes 63 have fine thread-like integral iins from header to header, and in that respect are identical with the tubes 3s except in some cases as to size. Fig. 1 is a perspective view ot tubes of this type. The iins til extend nearly but not quite to the ends of the tubes, and the plain ends S are belled out, so they fit the holes in the tube sheets and headers. These holes are large enough to pass the fins.

The superheater tubes are so spaced and ar ranged that the superheater approximately lls the offtake passage through an arc of over 180. Since the tubes are rather closely spaced the fins not only serve as secondary heat exchange surfaces but, because they extend transversely to the tubes and consequently in a direction of flow through the offtake, they serve as ow directing means ensuring a substantially uniform distribution of refrigerant ow over the entire superheater.

, The inlet connection 32 leads by way of curved pipe 65 to one end of header 53, i. e. to the inlet chamber of the first pass. From the exit cham ber of the last pass, which is on header bil, a curved pipe GS leads to' the outlet connection Each of the pipes G5, 86 has a threaded fitting Bia, 66a on its end to receive the connections 32, 33 (see Fig. 2).

The headers 58 and 5@ are held to trough tb by straps 61, and the tubes 63 are supported inm termediate the headers by a suitable number of arcuate plates S8 (two being shown), through which the tubes pass, as best shown in Fig. 3. The angle clips 69 with bolts 1l (see Figs. 3 and permit the plates 68 to be drawn tightly against the trough 48.

In manufacturing the evaporator, the shell is formed and one of the rings 31 is welded in place. The trough and superheater are constructed sep arately, the coil is tested, and then assembled with the trough as indicated in Fig. 3, together with the bafile 52 and crow foot stay structures 51. The trough and superheater assembly is then inserted through the open end of the shell,

and the second ring 31 is placed and welded to the shell.

Then the connections 2l, 32, 33 and it are screwed into the nipples 53, E@ and itno fittings 65a., 66a, in the pipes 65 and t6, as the case may be. after which the connections are all Welded to the shell il, as shown in Fig. 2. At this time the ends of trough lit also are welded to rings 31. After testingall connections and joints the tube sheets are mounted in t'fheir seats and brazed to rings 91 after which' the water tubes are placed and brazed to the tube sheets. During brazing of the tubes to the tube sheets,

warping if; prevented by forcing the tube sheet against the crow ioot stay structure..

Various diderent heads di and gaskets i3 may be applied to give the desired number oi water passes.

When the evaporator is operating at low refrigerant liquid level, the comparatively high oil concentration causes foaming and the foam is heated and all refrigerant evaporated in passage over the superheater. Similarly whenl operating at high liquidlevel, liquid slop-overs are evaporated by the heating effect of the superheater coil. Usually oil passes ofi through the suction line as in the Pownall device, but there is nothing in the design of the evaporator to preventthe use of oil separators of various types.

While the invention offers advantages peculiar to refrigeration when used in the Pownall circuit,

it has certain inherent advantages which are independent of the particular field of use. It can be used in any system in which vapor evolved from an evaporating heat exchanger is subjected to a heat exchange as it ows away from such exchanger. The use of the trough within a generally cylindrical shell and the use of the space between the trough and the shell as the oftake give uniform pressure over the entire vapor disengaging surface of the liquid in the trough. The invention permits the use of an offtake of such large cross-sectional area as to reduce the velocity of vapor fl'ow to moderate limits. It offers ample space for mounting the second heat exchanger and if the heat exchanger is finned, the fins can be used to distribute the iiow over the entire secondary heat exchanger. These eiects are present whether the second heat exchanger acts to deliver heat to or withdraw heat from the o-iiowing vapor.

' Further, if the secondary exchanger is a superheater, as it is in the Pownall device, it is by no means essential that the heating medium passing through the superheater be delivered to the evaporator. it need not even be the same liquid as that evaporated in the evaporator.

Thus, while the structure has peculiar advantages when used in the Pownall relationship, and that is the environment in which immediate commercial use of it is contemplated, the various advantages of the invention can be had in other environments, and such use is within contemplation and within the scope of the invention.

In this connection, it is pertinent to remark that when the invention is used in the Pownall circuit, the tubes of both exchangers should be finned, for in this system the additional heat transfer surface is needed to secure the desired violent ebullition which gives the foam lifting and" priming effects. In other fields, the fins are not always needed.

I claim:

1. An evaporator comprising in combination a shell, tube sheets with tubes extending therebetween; connections for passing a heat conveying medium through said tubes; a trough structure within said shell .serving to retain a volatile liquid in contact with said tubes and providing in conjunction with the shell an ofitake which passes between said shell and trough; a connection for supplying volatile liquid to said trough; a heat exchanger in said oftake; and connections for passing a heat exchanging medium through the last named exchanger.

2. The combination defined in claim 1 in which the exchanger mounted in the oitake is of the multi-pass, mul ti-tubular type.

3. The combination defined in claim 1 in which the exchanger mounted in the oftake is of the multi-pass, multi-tubular finned type.

4. An evaporator comprising an elongated trough open at its top; a surface heat exchanger in the trough; an enveloping shell enclosing the trough and forming therewith an ofltake which leads from the tcp of the 'trough down one side beneath and up the other side thereof, said offtake extending substantially the entire length of the trough; a second surface heat exchanger in said offtake; connections for supplying a volatile liquid to said trough; and separate connections for passing different heat conveying fluids through the respective heat exchangers.

5. An evaporator comprising an elongated trough open at its top; a surface heat exchanger in the trough; an enveloping shell enclosing the trough and forming therewith an ofitake which leads from the top of the trough between the shell and the trough; a second heat exchanger in said otake; connections for supplying a volatile liquid t) said trough; and separate connections supplying heat conveying media to the respective heat exchangers.

6. An evaporator comprising a shell with tube sheets and tubes extending therebetween; means for passing a heat conveying fluid through said* tubes; a trough structure within said shell serving to retain a volatile liquid in contact with said tubes and providing in conjunction with the shell an oitake for' vapor which passes between said shell and trough; a surface heat exchanger in said offtake; and connections for supplying volatile liquid to said trough and for causing at least a part thereof to pass through the heat exchanger just mentioned.

'7. An evaporator comprising a shell with tube sheets and tubes extending therebetween; means for passing a. heat conveying fiuidthrough said tubes; a trough extending between said tube sheets, embracing and extending above said tubes and extending to the shell along one margin, said trough serving to hold a bath of volatile liquid in contact with at least the lower ones of said tubes and aording with the shell an oitake which passes between the shell and trough around and beneath the trough; a multi-pass finned tube heat exchanger substantially filling said oil'take; and connections for volatile supplying liquid to said trough directly and also indirectly through the heat exchanger just mentioned.

'8. The combination defined in claim 7 in which the shell is cylindrical, the trough is arcuate in cross-section and substantially concentric with the shell, and the heat exchanger in the ofltake comprises headers embracing and supported by the trough and connected by tubes.

9. The combination dened in claim 7 in which the shell is cylindrical, the trough is arcuate in cross-section and substantially concentric with the shell, the heat exchanger in the offtake comprises headers embracing and supported by the trough and connected by tubes, and the trough and tube sheets are connected to and sustained by stiiener rings fixed in the ends of the cylindrical Wall of the shell.

10. The combination' of a cylindrical shell; an extended surface heat exchanger extending axially within said shell from end to end and spaced from the walls of the shell; a trough within said shell embracing said exchanger spaced from the walls of the shell and serving to retain a volatile liquid in contact with at least a portion of said exchanger, said trough being open at its top to the interior of said shell; a second surface heat exchanger mounted in the space between the bottom and sides of said trough and said shell; means comprising a suction connection communicating with said space at a point remote from the top of said trough arranged to cause vapor evolved from the liquid in said trough to flow in heat exchanging relation with said superheater; and connections for supplying volatile liquid to said trough through two paths in parallel, one of said paths leading through the second surface heat exchanger.

`l1. The combination dened in claim 10 in which the second heat exchanger is finned and the ns extend in the direction of vapor flow through the space between the trough and shell and thus serve as now directing means.

12. 'I'he combination deiined in claim l0 in -which the cylindrical shell is provided with internal stiffening rings at its ends, and the trough ts at its ends into said rings and is welded thereto.

13. The combination dened in claim l0 in which the cylindrical shell is provided with internal stiening rings at its ends, into which the ends of the trough t, the side walls and ends of the shell and the ends of the trough being welded or brazed to said rings, and the second heat exchanger is attached 'to and sustained by the trough. Y

14. An evaporator comprising an elongated trough open at its top; a surface heat exchanger in the trough; and an enveloping shell enclosing the trough and forming therewith an oitake which leads from the top of the trough, down one side, beneath and up 'the other side, said oitake extending substantially the entire length of the trough.

15.I An evaporator comprising an elongated trough open at its top; 9, surface heat exchanger in the trough; a connection'for supplying volatile liquid to said trough; an enveloping shell enclosing the trough and forming therewith an otake which leads from the top of the trough, down one side, beneath and up the other side, said offtake extending substantially the entire length of the trough; a second surface heat exchanger in said oiftake; and connections for passing heat conveying liquids through said heat exchangers.`

WALTER E. BELINE.

CERTIFICATE OF CORRECTION.

Patent No. 2,512,515. March 2, 191g.

WALTER E BELINE It is hereby certified` that error appears in the printed specification of theabove numbered patent requiring correction as follows: Page 14., first column, line 52, for "volatile supplying read --supplying volati1e; and

that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed nd sealed this 15th day of April, A. D. l9li5.

Henry Van Arsdale,

(Seal) Acting Commissioner of Patents.

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