US2220886A - Fluid heat exchange apparatus - Google Patents

Description

Nov. 12, 1940. P. R. CASSIDY 2,220,886

FLUID HEAT EXCHANGE APPARATUS 8 Sheets-Sheet 1 Fig] Filed Sept. 20, 1935 INVENTOR. Perry Cassidy ATTORNEY}.

Nov 12, 1940.

P. R. CASSIDY I FLUID HEAT EXCHANGE APPARATUS Filed Sept. .20, 1955 8 Sheets-Sheet 2 INVENTOR.

ATTORNIISY.

8 Sheets-Sheet 3 ATTORNEY.

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P. R. CASSIDY F UID HEAT EXCHANGE APPARATUS Filed Sept. 20, 1955 a Shets-Sheet 4 R w@ N E 5 WW 6 u m D Noy. 12, 1940.

P. R. CASSIDY FLUID HEAT EXCHANGE APPARATUS Filed Sept. 20, 1935 8 Sheets-Sheet 5 INVENTOR';

Perry 2. Cdssz'ay Nov. 12 1940.

. R. CASSIDY FLUID HEAT EXCHANGE APPARATUS Filed Sept. 20; 1935 8 Sheets-Sheet 6 Nov. 12, 1940. IP. R. CASSIDY 2,220,886

FLUID HEAT EXCHANGE APPA'RATUS Filed Sept. 20, 1935 8 Sheets-Sheet 7 1 Perry 1Qv Cassidy N5v.12,1940. Sam 7 2,220,886

FLUID HEAT EXCHANGE APPARATUS Filed se i. 20, 1935 I s Sheet-Sheet s Fig 9 1 f o INVENTOR.

Perry I? Cassz'dy Patented Nov. 12, 1940 UNITED STAES Y 2,220,886 FLUID HEAT EXCHANGE APPARATUS I Perry R. Cassidy, Short Hills, N. J. assignor to The Babcock & Wilcox Company, Newark, N. J., a corporation of New Jersey Application September 20, 1935, Serial No. 41,403

8 Claims.

This invention relates to fluid heat exchange apparatus, and it is exemplified herein in connection with water tube steam boilers.

More particularly, the invention comprehends improvements in steam boilers of the bent tube type, with which superheaters are associated.

It is an object of the invention to provide a boiler which will generate steam at high capacities without impairment of the quality or superheat of the steam, or integrity of the superheater. High steam quality as to purityis attained by reason of the relation of the disengaging surfaces of the water to the saturated steam exit in the separator chamber of the boiler. High 10 superheat is also attained with a minimum of superheater surface by improving the transverse mass flow (mass flow being authoritatively and Widely known as weight of gases per unit of area,

\ per unit of time, weight rate of flow; Chemical Engineering Handbook, J. H. Perry, 1934 edition page 736, McGraw Hill Publishing Company, New

York, N. Y.: Kents Mechanical Engineers Handbook, eleventh edition, volume II, 1936, page 6-45,

John Wiley 8; Sons, Publishers: American Standard Association, Letter Symbols for Heat and Thermodynamics including Heat Flow-H. F.,

October 1939, page 7) of high temperature gases over that surface, and the integrity of the superheater is maintained by a radiant heat screen and drainage of water from it.

It is also an object of the invention to improve the effectiveness of heat transfer in a multiple separator boiler by providing for the most'effective flow of the furnace gases transversely of the vertically disposed steam generating tubes, and this reduces the cost of the boiler per unit of capacity. i

A further object of the invention. is an improvement in such boilers wherein ratio of the cost 40 of the superheater to the cost of the total installation is reduced, with no consequent loss ineffectiveness.

Other objectsof the invention relate to water tube steam boilers in which a single lower drum is joined by separate banks of upright tubes to a plurality of upper drums. These banks of tubes extend entirely across the width of the boiler, and the general combination is such that natural tendencies toward priming and the pro- 50 duction of steam under high capacity operating conditions are overcome. The steam separation takes place finally in an offtake drum increasingly effective as the boiler capacity increases so that the production of dry steam is maintained.

55 The steam and water separation is a multiple stage separation taking place in different stages in the upper drums as a considerable portion of the steam generated passes through thedrums in succession to a steam outlet which is on the rear drum. t

The invention comprehends a multiple tube bank water steam boiler in which the front bank of tubes receives gases from a furnace acr oss the entire width of the boiler and in. a' single gas pass. It, discharges the gases rearwardly into a gas 10 equalization space extending also across the entire width of the boiler. Thus, substantially uniform gas distribution across the front bank is effected, regardless of the direction of firing, or of the type of furnace used.

A slag screen may also be advantageously providedby the front bank of the tubes, andjto this end, some of the tubes of the front bank are more widely spaced. If the firing of the furnace is from the side, the gases would concentrate toward one end and thus tend to cause an unequal flow across the'front bank; The 'inventioncomprehends, as one means for neutralizing such an effect, a tapering free gas flow space from side to side of the boiler, in the front bank. This is provided by a tapering bafile.

The space at the rear of the front bank of tubes is made wide enough to contribute to gas distribution and'equalization across the front bank and the gases enter this space across the entire width of the boiler in a generally horizontal direction at the front of thespace. They leave it rearwardly over a portion only of the width of the boiler, and the relationship of elements effecting this action wouldhave a natural tendency to cause some of thegases in front of the exit for the equalization space to flow straight across that space while gases at the other end of the space would be compelled to approach the exit by side to side flow. If the equalization 40 space did not have sufficient width such side to side flow would tend to disturb distribution of the gases across the front bank even with front firing and thus tend to concentrate the gas flow through that portion directly in front of the exit from the space. This could be corrected, with a narrow space, by such front bank distribution baffies as have been mentioned, but by making the space sufficiently Wide the side to side gas flow through the space takes place at a low velocity and uniform distribution in the front bank may be effected without such distribution baffles, therefore making for a saving in draft loss and keeping all front tube surface equally efiective at high capacities.

To effect the above described gas flow and to control gas flow in the inter-tube bank spaces, an angle baffle is provided. One leg of this baffle forms a back wall of the above described gas equalization space, and the other leg bounds the gas pass which forms the exit from that space. This bafile cooperates with another straight baffle to provide three gas passes extending forwardly or rearwardly across the tube "bank "from side to side, the first starting at the'exit from-said space, and the gases being forced to fiow in a generally horizontal direction throughout the boiler. The boiler, as above described, may beconsidered as having a tapering first gas pass, including the whole front bank at its wide part, and the invention comprehends a superheater'which.islocated in a narrow part of that gas pass between the first and second bank of tubes. The arrangement improves mass flow over the superheater by giving it a high value and equalizing it to the end that variations in the superheat from a desirable fiat curve will be .minimized as the boiler .is operated at increasing capacity.

Other objects of the invention will appear as the accompanyingdescription proceeds.

Fig. v1 is a view in the nature of a vertical section, showing a water tube steam boiler and its furnace together with the relationship .of the superheater to the steam generating tubes. This view is taken on the .line l--.l of Fig. 3.

Fig. 2 is a vertical sectional view taken on the line 2-2'of Fig. 3.

Fig. ,3 is :a horizontal section taken on the line 3-3 .of Fig. 2. This view shows the relationship of the different gas passes to the superheater and :to the steam generating tubes.

'Fig. 4 'is a view in the nature of a front elevation of the front bank ofsteam generating tubes, showing a tapered baffle for effecting distribution of gasflow acrossthe steam generating tubes .of the first bank. In a cut-out-portion, apartbf the superheater construction is shown.

Fig. 5 is a view in the'nature of a vertical section showing a modified boiler construction in which the first section of the superheater extends entirely across the width of the boiler.

Fig. 6 is a section taken on the line 6iof Fig. 5.

Fig. 7 is a detailed view in the nature of a vertical section showing the manner in which the horizontal manifolds of the Fig. 1 superheater may be arranged and supported.

Fig. 8 is a verticalsection taken in a plane as indicated by the line 88 of Fig. '7.

Fig. 9 is a viewin the nature of a vertical section showing a modified arrangement of parts involved in the location of the superheater manifolds.

Fig. 10 is a viewin the nature of an upright section taken on the line I ill li of Fig. 9.

The drawings indicate bent tube steam boilers each having a lower drum I!) connected to the steam and water drums l2 and M by banks of steam generating tubes. In each illustrative embodiment of the invention the tubes of the front bank liiextend forwardly of the drum lil adjacent the combustion chamber l8 of a furnace. Tubes .connected to the rear drum 12 are disposed rearwardly of av super-heater 20, relative to gas flow.

Referring to Fig. 3 of the drawings, the furnace gases from the combustion chamber 18 first pass over and between the tubes of the bank i 6 into an equalizer chamber 22. From this chamber they are compelled by the bafiles 24 and 25 to pass 7 one gas pass into another.

across the tubes of the superheater 20 and rearwardly of the boiler through the first gas pass defined by the baffle 26 and the wall 28 of the boiler. After passing over the tubes of the superheater the gases pass over and between the tubes 39 which form a part of the bank connecting the drums Ill and I2.

From the outlet 32 of the first gas pass the gases proceed to the inlet 34 of the second gas pass through which the gases proceed forwardly through the banks of steam generating tubes 38 and 38. This second gas pass is formed between the bailles 26 and 40, the latter extending forwardly from the rear wall 42 of the boiler.

After passing across the bank of tubes 38 in the second pass the furnace gases turn in the space 144 :rearwardly of the wall 24 and enter the third gas pass in which they proceed rearwardly across the tubes and then upwardly to a flue 45. The flow of gases through this flue may be controlled by dampers 46 and 48.

In connection with the above indicated structure, it will be noted that open spaces are provided at the positions where the gases turn from This facilitates the changes in direction of the gases and is advantageous for two particular reasons, first, that draft loss incident to the turning of the gases is minimized, and second, that uniform distribution across the tubes in the different gas passes is effected.

It will also be noted, in the illustrative boiler, that thegases have a generally horizontal flow and that they change their directions at the same level. Thetubes contacted by the horizontally moving gases are preferably inclined and these circumstances facilitate the deposition and removal of solids carried by the gases. They may fall out of the gas stream into pockets from which they may be conveniently removed. This promotes the maintenance of clean heating surfaces.

The fact that the tubes of the front and rear bank are inclined as shown is advantageous. Referring to the inclination of the front bank, the space between the front furnace wall and the tubes of the front bank constitutes a part of the furnace space, and the gases rising into this triangular space are well distributed over the tubes of the bank. Also, this arrangement includes tubes which extend over the top of the furnace so that they are directly exposed to radiant heat. With this arrangement also, wall cooling tubes may be conveniently added and connected into the boiler circulation, thus giving a completely water cooled furnace top with a tapering gas pass to promote uni-form distribution of gas flow across the tubes of the front bank. Referring to the inclination of the rear bank with respect to the rear wall of the boiler, gas flow to an exit flue connection from the last gas pass and at the upper rear part of the boiler is facilitated.

Although the illustrative embodiments include but two steam and water drums, it is to be understood that these embodimens are only representative, and that a greater number of steam and water drums and connecting banks of steam generating tubes may be employed. In any event the gas flow across the successive banks of tubes is of the nature above indicated.

Fig. 4 of the drawings indicates a flow distributor represented as a substantially triangular baffle 59 preferably supported by the tubes 52 of the front bank 86. This baflie may consist of refractory material held in position by metallic studs which are weldedto. the tubes 52.. Its wider end, in a vertical direction, is adjacent the wall 28 as shown in Fig. 4, and it is located directly in front of the first gas pass. In con-, junction with the tubes of the bank IE it affords upper and lower gas passages through that bank, said passages, increasing in flow area. as the wall 54 is approached. Short circuiting of the tubes disposed away from the first gas passand toward the Wall 54 is thus minimized and a more uniform distribution of gas contact over the tubes of the first bank is attained. I

The superheater disposed in'the first gas pass and rearwardlyjof the wider end of the equalizer bafiie 56 may consist of an outlet header. 56 supported upon the drum I0 and having manifolds 56 extending forwardly therefrom. The inlet ends of these manifolds are connected to the steam space 66 of the drum I2 by inlet, tubes 62. As shown in Fig. 3, these tubes may have a spacing wider than that of the remaining tubes of the superheater, and the entrance of Water into these tubes is prevented by a steam and water separator 64.

The steam after passing from the drum I2 to the inlet ends of the manifolds 58 through the tubes 62 proceeds in succession through the series of upwardly looped tubes 64, 66 and GBto the outlet ends of the manifolds. Opposite ends of these looped tubes are connected to separate manifold chambers formed by the partitions III as clearly indicated in Figs. 8 and 10. From the rearmost chambers steam proceeds to the outlet header 56 and then to points of use.

In Figs. 5 and 6 of the drawings there is illustrated an embodiment in which the superheater is aranged in two sections. The primary section consists of inlet tubes 12 and upwardly looped tubes I4 which are arranged as a bank extending entirely across the furnace. These tubes are connected at their lower ends. by the header I6 which is preferably mounted upon a similar header I8 which connects the tubes I4 with the manifolds 86. These manifolds are chambered so as to cause the steam to pass in succession through the series of looped tubes 82 and 84 to the outlet portionsv of the manifolds and thence to the outlet header 86.

As indicated clearly in Fig. 6 of the drawings, the looped tubes 82 and 84 constituting the second section of the superheater are positioned entirely in the first gas pass at one side of the boiler, this gas pass being formed by the wall 68 and the baffle 96.

When the arrangement of elements indicated in Figs. 5 and 6 causes undesirable short circuiting of some of the superheater tubes in the first section and some of the steam generating tubes in the front bank a triangular trickle baflle may be employed. As shown, this baffle consists of refractory elements 92 supported by the tubes 94 and so arranged that alternate inter-tube spaces are closed thereby. In other words, there is mainly supported by the tubes which con-v nect it to the upper drums. When the parts are arranged in this manner} the lower drum is relatively free to move upwardlyor downwardly in response to the temperature changes in the tubes. The outlet header 56 of the superheater istpreferably supported upon the lower drum II] asindicated in Fig. 7 of the drawings. Here, av bracket I 30 is secured to lugs I3I attached to the. header 56, and is preferably formed at its top to constitute a saddle. The superheater manifolds 58 communicate With'the header as shown, and are supported at their outer ends by brackets I 32 which may be welded to the tubes I34 ofthe front bank I6. These brackets are received between pairs of lugs I36 which are rigid with, and depend from, a channel I38 ex-' tending across the superheater. As particularly shown in Fig.6, downwardly extending lugs I46 are bolted tothe channel and these lugs are preferably welded to the manifolds 58. In this construction theload of the superheater is distributed over two rows of tubes of the bank I6 by means of struts I42 which are shown as welded to the tubes I34.

Inthe Fig. 9 construction the load of the manifolds is taken entirely upon the drum III. The

brackets I36 support the header 56 and rear ends of the manifolds, while the forward endsof the manifolds are supported by struts I44 which may be pivoted as indicated at I46 to brackets I48 which are fixed to the drum Ill. At the opposite ends of the struts there are pivotal conthe lower drum III may be pivotally tied to a' fixed frame member I54 by means of a link I56 which passes through a bracket I58 rigidly se-' cured to the drum. When the drum is sup-' ported in this manner it is free to move upwardly and downwardly as a result of expansion and contraction of the boiler tubes. but it will still be maintained in operative position and be prevented from creating any undesirable side thrust upon the part I66 of the furnace wall which is I shown above the header I62.

The boiler furnace may be one in which a burner I64 is employed in connection with the utilization of a slag forming fuel. Molten slag collects on the bottom of the furnaceand is pe-l riodically tapped through an opening I66.

Walls of the furnace may be fluid cooled as indicated. To provide for such fluid cooling, the headers I62, I68, and III] at one side of the furnace are preferably connected into the fluid.

circulation of the boiler. They are also connected by wall tubes I12 and I14. Adequate circ'ulation in these tubes is promoted by exterior circulators I16 which are shown as connecting the headers I62 and I'IIJ.

From the header IIU floor cooling tubes I18 extend across the bottom of the furnace and between the wall tubes I86 to a position where they are connected to the header I82. Exterior circulating tubes I84 may connect these headers to thedrum III. The tubes I lead from the lower header I86 to an upper header I88 which is connected to the drum I4 by circulator tubes I96 and to the header I86 by tubes I92.

Fluid cooled headers I94 are also provided on the. remaining sides of the furnace. They may be connected into the boiler circulation by uptake :tubes 1:95 :and be .joined to a lower side Wall header :by wa'll tubes I 98.

.In Fig; 2 of the drawings, a section of the gas distribution baiile'fifi is shown at 203. This'bafhe as well as 'the wall .23 shown in section at 282 may be of stud tube construction in which the refractory material is "maintained, and held in operative position, by metallic studs welded to the tubes. 1

2 also show's'a'guid'e for the header F52. This may consist of parallel flanges 2M and 296 extendingflupwardly from the I beam 2ll8. Afin 2H), secured'to the header I62, is positioned between these flanges. Fig. 3 indicates refractory blocks 2 52 which may be secured to the wall tubes "ltll. These blocks :may be "Bailey blocks, constructed of metal, and tightly secured to the tubes-withja thermal bond between the blocks and the tubes, or alternatively, may consist of a stud tube construction in which metallic studs are welded 'to' the tubes and thereafter covered with refractory material and "installed as a plastic. Similarly, the gas distribution bafile shown in Fig. 4 of the drawings may be constructed of preformed blocks secured to the tubes, or may be of" stud tube construction as above indicated.

What is claimed is:

I lp'In a water tube steam boiler, an organization including a plurality of upper drums connected to a lower drum by front and rear banks of steam'generating"tubes, a furnace, means for directing 'the furnace gases transversely of the drums and through a first gas pass at one side of the boiler,'sai'd means including an upright wall extending substantially across one of said banks from front to rear, baffle means includin a similar wall and forming a second gas pass in which the gases pass from the outlet of the first '14): pass reversely of their movement in the first pass and forwardly transversely of the tubes of a rear bank, and a superheater positioned in said first pass rearwardly of the tubes of the front bank so as to be screened -th'ereby, the front bank being spaced forwardly of the superheater throughout its length andforwardly of the foremost part of said 'baffie means and upright wall so as to form a gas equalization chamber.

2. In a water tube steam-boiler having a plural-ity'of banks of steam generating tubes connecting a lower drum to a plurality of parallel upper drums, a boiler setting, a furnace including a combustion chamber, means forming a first gas passpositioned at one side of the setting and extending transversely of the drums and tubes and communicating with said chamber at one side of the boiler only, a superheater positioned in said gas pass and screened by the tubes of one of said banks, means forming a second gas pass communicating with the outlet of the first and directing the gases in a reverse direction transversely of said tubes, a partition'extending between said banks of tubes forward of the end of the second gas pass and so associated with said first means as to compel gases to pass from the furnace through the first gas pass, one of said banks of tubes extending entirely across the boiler and spaced forwardly of the superheater and said partition so as to afford a gas equalization space, and means associated with the tubes of the last named bank for equally distributing gases passing across the tubes of said bank.

3. In a superheater, a primary section subjected to heating gases at high temperatures operating-on the counterflow principle, a parallel flow section subjected to the same "heating gases after their temperature has decreased due to contact with the primarysection, means connecting said sections so that a fluid in the sections passes to the parallel flow section from the primary section, and means providing for increased mass flow of the gases over the parallel flow section.

4. In a water tube steam boiler of the Stirling type, a boiler setting, a lower drum, upper drums, upright front and rearward banks of steam generating tubes connecting the drums, a transverse bafiie extending from the lower drum to an upper drum transversely -of the setting rearwardly of and spaced from the front bank; upright longitudinal baffles so extending relative to a rearward bank and so cooperating with the setting Walls :and the transverse bafile as to form a plurality of serially connected gas passes the inlet of which leads from the gas space r-earwardlyof the front bank of tubes and is con-fined to one side of the setting toward one end of 'a-dr-um, afurnace from which the gases are distributed across the front bank, said transverse bafile extending substantially at right angles to the longitudinal bailies, and a gas distribution baffle extending across the front bank with a gas contacting surface which diminishes from the wide end of the bafiie directly in front of the inlet to the first of said passes to its narrow end near'the opposite side of the front bank.

5; In a cross flow water tube boiler, a boiler setting, spaced front and rear banks of steam generating tubes exposed externally to high temperature furnace gases, means for connecting said banks of tubes into boiler circulation, there being a gas equalization chamber rearwardly of the front bank with reference to gas flow, a transverse baflie positi'oned'rearwardly of said chamber and forwardly of said 'rear bank of tubes, said bafiie extending only part of the way across the setting and terminating at the side of the first of a plurality of gas passes loading rearwardly and then forwardly across the rear bank, a longitudinal :bafile extending transversely of and joining the first 'baffie along one side of the first gas pass,

means defining a furnace gas chamber forwardly of the front bank of tubes, means providing a gas outlet remote from the first gas pass laterally of the setting, said bafiies being supported and cooled by said tubes, and a superheater disposed rearwardly of the front bank of tubes and having tubes extending across the entrance to the first gas pass.

6. In a water tube steam generator, a plurality of upper drums, a submerged drum, a plurality of separated banks of steam generating tubes connecting the upper drums to the submerged drum, downcomers directly connecting the front upper drum with the'su'bmerged drum and disposed in a gas pass of the generator, and bafile means causing furnace gases to pass over said tubes in a plurality of gas [passes before contacting with the downcomers.

7. In a water tube steam boiler of the Stirling type, means forming a plurality of steam and water chambers, means forming a water chamber below the steam and water chambers, front and rear banks of steam generating tubes connecting the submerged chamber to the other chambers, a furnace, downco'mers connecting the front steam and water chamber to the submerged chamber, and baffles forming a plurality of gas passes and directing the gases over said banks of steam generating tubes before the gases contact with the downcomers.

8. In fluid heat exchange apparatus, a furnace, a bank of spaced tubes extending across the path of the furnace gases, means forming an unobstructed gas flow equalization chamber substan tially coextensive with said bank of tubes and disposed on the side of said bank opposite the furnace, means forming a gas pass directly communicating with said chamber over only a fraction of the horizontal Width of the chamber and the furnace with they furnace gases passing over said tubes and through said chamber to the entrance of the gas pass, means forming additional heating surface in the gas pass, a part of said bank of spaced tubes positioned directly forwardly of said entrance while the remainder of the bank extends laterally in a horizontal direction beyond the entrance and in front of said chamber.

PERRY R. CASSIDY.

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