US2221871A - Fluid heat exchange apparatus - Google Patents

Description

FLUID HEAT EXCHANGE APPARATUS Filed Sept. 28, 1-935 4 Sheets-Sheet-l -Fig INVENTOR. H0 ward Ke ATTORNEY.

Nov. 19, 1940.

H. J. KERR FLUID HEAT EXCHANGE APPARATUS Filed Sept. 28, 1935 4 Sheets-Sheet 2 INVENTOR.

Ho'n/ara J Kerr ATTORNEY.

Nov. 19, 1940. KERR 2,221, 71

FLUID HEAT EXCHANGE APPARATUS Filed Sept. 28, 1935 4 Sheets-Sheet 3 INVENTOR. Howard J K8 rr ATTORNEY.

Nov. 19, 1949 H. .J. KERR 2,221,871

FLUID HEAT EXCHANGE APPARATUS Filed Sept. 28; 1955 4 Sheets-Sheet 4 FM? I Fig]! Afr? I7 /77 ms /75 J9 M3 202 INVENTOR.

J Howard .1 Kerr I 1 s' ATTORNEY.

Patented Nov. 19, 1940 l'iE srarss ,ZZLtllf FLUID HEAT EXCHANGE APPARATUS a Application September 28, 1935, Serial No. 42,558

7 Claims.

This invention relates to fluid heat exchange devices, and more particularly to improvements in vapor heaters.

It is an object of the invention to so improve I tubular vapor heaters that they may not be damaged or their operation rendered ineffective by condensate or other liquid in the heaters.

It is a further object of the invention to provide a tubular vapor heater in which the tubular sections are drained into a succeeding tubular section without excessive by-passing of vapor from the pockets to the succeeding section. In one embodiment of the invention velocity created efiects are employed to restrict the by-pass flow of the vapor.

In the operation of steam boilers having multiple loop superheaters, undesirable conditions are created by reason of the fact that water or other liquid may collect in the pockets formed by the low level of the loops. This collection may result from hydrostatic tests while the boiler is out of service, or it may result from the condensation of vapor in the superheater while the boiler is being started up. In some cases also, it has been the practice to flood the superheater with liquid prior to starting the boiler in order to prevent damage to the superheater by reason of the contact therewith of hot gases before steam flows through the superheater in sufiicient amounts to protect it. In any event, such accumulations of liquid within the superheater are not only apt to cause damage to a turbine, but they are also apt to cause distortion of the superheater tubes due to excessive inequalities of temperature conditions. Each tube length of the superheater may,

under such circumstances, be subjected to wide- 1y different temperatures at different portions. For instance, the lower ends of the loops may be relatively cool because of accumulations of water, and adjoining portions of separate tubes may have highly heated superheater steam in them before steam flow takes place through the superheater. In addition, even after steam flow has been established through the superheater as a whole, the superheater having multiples of looped tubes in parallel, some of the loops may be water bound with no steam flow, while the rest are clear, and no cooling of the water bound tubes above the water level can occur until the water is evaporated or otherwise removed. Such conditions cause warping and distortion of the tubes. It is an object of this invention to prevent the occurrence of such undesirable results.

The invention will be described with reference to the accompanying drawings, in which:

Fig. 1 is a view in the nature of a vertical sec tion of a Stirling boiler organization in which the illustrative superheater construction is incorporated.

Fig. 2 is a horizontal section of such a boiler 5.1: organization as that shown in Fig. 1.

Fig. 3 is aview showing the relationship of two of the superheater manifold sections, mainly in vertical section. 1

Fig. 4 is a horizontal section taken on the line 4-4 of Fig. 3 and showing the vortex chamber in one of the partitions separating the manifold sections. I I

Fig. 5 is a vertical section through the manifold, showing the ,realtionship of the vortex chamber to its inlet and outlet ports.

Fig. 6 is a detail view showing an additional embodiment of the Fig. 12 construction in vertical section and in elevation. 1

Fig. '7 is a view in the nature of a vertical sec 20 tion, showing a three drum cross flow boiler including another embodiment of the superheater.

Fig. 8 is a View showing a part of the Fig. 11 superheater on an enlarged scale.

Fig. 9 is a detail view showin arts of a superheater construction in vertical section. This figure illustrates an arrangement of parts similar to those shown in Fig. 11.

Fig. 10 is a detail view showing an additional embodiment partly in evelation and partly in vertical section.

Fig. 11 is a vertical section of the three drum vent tube boiler having associated therewith a superheater constructed in accordance with the invention. I

Fig. 12 is a detail view illustrating a manner in which the superheater loops of the Fig. '7 boiler may be connected to succeeding sections of the superheater. 40

Fig. 13 is a transverse vertical section taken on the line i3l3 of Fig.12.

The boiler indicated in Fig. l of the drawings includes a lower drum I!) connected to the upper drum l2 by a bank of steam generating tubes l4 which are exposed to furnace gases proceeding from the combustion chamber it. The baffle l8 extending along the rearward tubes of this bank causes the furnace gases to first proceed. across the tubes to a position near the drum 5?. From this 50 position they pass downwardly to a second gas pass 20 in which there is located a superheater 22.

The superheater receives its steam from an offtake drum 24 through inlet tubes 26. These 55 tubes are connected to the header 28 from which the tubes 30 of the superheater depend. The tubes are arranged in flat multiple loop coils with several such fiat coils in parallel. The bottom ends of the tubes of each flat coil are connected to the manifolds 32 which are provided with diaphragms 34 to cause the steam to pass in succession through the superheater tube loops 36 and 38. From the last mentioned loops the steam proceeds to the outlet chambers of the manifolds and thence to the superheater outlet header 40. This header is drained through the valve 4|.

The furnace gases, on leaving the superheater, pass upwardly through a third gas pass. This is defined by baffles 42 and 44 which extend along opposite sides of a bank of tubes including the tubes 46 connecting the drum 48 to the drum I and other tubes 50 connecting the drums I8 and I2.

From the top of the third gas pass the gases proceed downwardly to the flue 52 and in so doing they pass over a third bank of tubes 54, some of which directly connect the drums I8 and 24 while other tubes 55 afford direct communication between the drums I8 and 48 as clearly illustrated in the drawings.

Water circulators 56 afford direct communication between the drums I2 and 48 below their water levels, and the steam spaces of these drums are connected by steam and water circulators 58. Other steam circulators 68 directly connect the steam spaces of the drums 24 and 48, and above all of the steam circulators is located the roof 62 of the boiler.

In starting up such a boiler as that indicated in Fig. 1, any excessive accumulations of water in the manifolds 32 are apt to cause considerable damage. They may pass through the superheater and thence into a turbine in slugs and they operation of the superheater, steam passes from the chamber 66 through the tube section 69 which may be the inlet section of an inner loop tube 36 or 38. It passes upwardly through one leg of this loop and then downwardly through the other to the section 10 which communicates with the chamber 64.

The diaphragm is provided with an inlet port 12 which communicates with a vortex chamber 14. At the bottom of this chamber an outlet port 16 affords communication with the manifold chamber 64. If at any time during the operation of the boiler, water collects in the chamber 66 to a sufiicient extent it passes through the ports 12 and 16 and thence into the chamber 64. Thus, there can be no water level in any of the manifold chambers higher than the ports 12, when the flow resistance through the superheater tubes on opposite sides is equal to or greater than the hydraulic head of port 16 over 12, and inasmuch as the last of the manifold chambers is connected to the outlet header 40 to afford drainage, water cannot collect in the manifold sections to such an extent that it will interfere with the operation of the superheater by passing through the superheater tubes in slugs or preventing steam flow in some coils and causing tube damage by over heating.

Even if the water level, during the starting up of the boiler accumulates in all of the manifold chambers up to the levels of the ports 12 steam flow is not prevented and continued operation of the boiler will cause this water to be blown out or to be evaporated so that during normal operation the manifolds will be free of water. At such times the ports forming communication between the successive manifold chambers must not permit excessive amounts of steam to pass therethrough. Otherwise, the operation of the superheater would be impaired because the steam would not be sufficiently subjected to the heating action of the superheater in the tubes 36 and 38 and correspondingly, the lessened flow of steam through the tubes might not be sufficient to keep them cool. To prevent any such action the diaphragms are arranged to afford considerable resistance to steam flow. In the construction illustrated in Figs. 3, 4 and the vortex chambers provided in the projecting mid-portions 11 set up velocity created effects which reduce the steam flow directly from one manifold chamber to the other.

Fig. 11 indicates a cross flow boiler in which the superheater includes a plurality of inlet tubes I58 communicating with the steam space of the drum I52 and extending downwardly of a gas pass at positions rearwardly of the front bank of steam generating tubes I54. At their lower ends they are bent rearwardly of the boiler and then upwardly and downwardly to form the looped sections I56 and I58. This construction may be repeated to form the additional upward loops I68 and I62 which connect with the outlet tubes I64 and I66 in direct communication with the superheater outlet header I68.

The lower loops at the ends of the inlet sections I50 form pockets in which condensate might collect. To prevent this, these pockets are connected by drains and other superheater sections to drain outlet header 256. The drawings show the loop I12 to be connected to the lower section I14 by the tubular drain I16. Because there is no pressure drop between the loop I12 and the section I14 there will be no by-passing tendency when they are in communication through a constantly open passage. Hence, the drain connection may be provided as indicated in Fig. 9. Here, the metallic element I69 is welded at its upper end to the loop I12 and at its lower end to the section I 14, thus forming a rigid structural connection. A removable plug I1I allows access to the passage I13 which establishes communication between the connected elements. Similar connections I18 may connect similarly related parts at lower levels, but the conditions at the intervening connections I11 and I19 are different. There is a pressure drop between the connected sections I14 and I15, and a similar condition prevails between the sections I8I and I83. Hence, means are provided for restricting the steam short-circuiting or by-passing tendencies at these positions while freedom of water drainage is maintained. Such means are illustrated in Figs. 12 and 13.

When such a lower superheater tube loop as that indicated in Fig. 12 at I84 is drained into a succeeding superheater section such as the section I86 there is a pressure drop between the loop and the section when steam is flowing through the superheater. Assuming that steam is passing through the loop in the direction of the arrow I88, and through the section I86 in the direction of the arrow I98 to the superheater outlet header it is, of course, undesirable that any excessive 5 amount of steam pass directly from the loop through the connection I92. If such an amount of steam did pass directly to the section I86 any succeeding superheater loop sections would be robbed of steam and the heating effect of the su- 1 0 perheater and cooling effect of the steam on the tube would be impaired. Also, if a plurality of loops, such as the loops I84 drained into the section I86 and each loop was connected to the section I86 the total amount of steam by-passing some of the superheater loop sections might be a large portion of the total amount of steam passing to the superheater. Such serious effect is prevented by means which will now be described.

The connection I92 may be provided by a cylindrical metal section which is reduced at its end to provide extensions I94 and I96 which project respectively into the section I86 and the loop I84. Shoulders I98 provided at the junction of the main portion of these elements and the extensions I94 and I96 space the connected parts and provide grooves for the reception of weld metal which is indicated at 288.

A bore 282 of small diameter is formed coaxially through the connection I92 and its extensions and the ends of the extensions are particularly formed so as to create flow effects which tend to reduce steam flow to the section I86. As shown, the extension I94 has its face presented upstream in the section I86 beveled as indicated at 284. This, in effect, causes the outlet of the bore 282 to be presented up stream. The steam in the section I86, proceeding in the direction of the arrow I98, therefore creates an impact head which tends to offset the difference between the pressures in the loop I84 and the section I86. Also, at the other end of the connection I92 the extension I96 is formed with a beveled face 286. This causes the inlet of the passage 282 to be presented down stream in the loop I84 and thus creates a suction head, or reduces the pressure at the inlet. The effects of this arrangement are cumulative with respect to the impact heat effect at the other end of the connection I92, and the effect increases with velocity of flow of steam. Fig. 18 indicates cleanout plugs 288 formed opposite the bores 282 of the connections I92. When these connections are of small diameter, or when it is desired for other reasons, the superheater structure may be rigidified by the struts 2I8 and 2I2 on opposite sides of the connections.

These struts may be welded to the loops and the sections I86 as indicated at 2I4 and 2| 6.

The connections 228 indicated at Fig. 6 of the drawings will have an efiect greater than that of 50 the connections M2 to offset the pressure drop between the loop 222 and the succeeding superheater section 224. This is because the inlet 226 and the outlet 228 of the bore 238 are formed at an angle to the direction of the bore. The flow resistance added by reason of these turns in the passage between the loop 222 and the section 224 is a major part of the total flow resistance of each of the connections 228.

In the superheater indicated in Fig. '1 each coil includes a number of loop sections 232 each of which is separately drained into the manifold section 234. There is a pressure drop between the latter and each loop, and, therefore, each loop is in communication with the section 234 through the intermediacy of such connections as those shown in Figs. 12, 10 and 6. The passage of steam in excessive amounts directly from a loop to the outlet manifold section is, in each instance limited by the direction of flow and the velocity head effects on the connector ends. 5 Each outlet manifold section drains into an outlet header 236 supported by the lower drum 238, and the latter communicates with steam and water drums 248 and 242 through front and rear banks of steam generating tubes 244 and 246, re- 10 spectively. A pier 248 rests upon the tubes of the front banks and acts as a superheater support.

It also combines with the baflie walls 258, 252, the header 236, and the drum 238, to form a chamber through which access may be had to the header. 15 A workman may enter this chamber through an access door 254. Similar constructions are also present in the boiler shown in Fig. 1.

While the gas flow in the Fig. 1 boiler is to a major extent longitudinally of the tubes, the 20 gases in the Figs. 11, and '7 boilers flow mainly transversely of both the superheater tubes and the steam generating tubes.

Referring again to Fig. 11, it will be understood that all of the superheater loops ultimately drain 95 into an outlet tube or header 256 which is connected'to the sections I8I by tubes 258. The latter may extend partially around the drum I82 and thereby afiord lateral support for the superheater.

The boiler furnace preferably has walls which include wall cooling tubes which are connected into the boiler circulation. These are exemplified by the tubes 218 which extend along a boiler wall 212 indicated in Fig. 1 of the drawings. 85 These tubes may be connected at their upper ends to the header 214 which may have exterior circulators connecting it into the boiler circulation. Wall tubes 216 are similarly arranged along the opposite wall 218. These tubes are 40 shown as directly connected at their upper ends to the header 219. At their lower ends they may be connected to-a header similar to the header 214, and this header may be connected by circulators into the boiler circulation. Sim- -45 ilar arrangements of tubes and headers may be arranged along the walls of the furnace associated with the boiler indicated in Fig. 11 of the drawings.

Fig. 1 also indicates a depending flange 298 '50 which may be welded to the header 219 and positioned between upstanding guides 388 which are welded to the beam 382. With this arrangement, the wall 218 together with the tubes 216 may be free to expand upwardly, and the parts would 55 still be maintained in operative position during such movement. Such action takes place when the wall 218 is a part of a bottom supported furnace.

Due to the fact that the drum I8 tends to 60 move downwardly as the boiler tubes expand, and the header 219 tends to move independently of the drum I8 as the temperature of the furnace increases an expansion joint gas seal structure is provided between the drum and the header. As shown, this includes a Z bar 384 fixed to the drum l8 and received in a pocket formed by upstanding plates 386 and 388 which are directly or indirectly rigidly secured to the header 219. This seal construction is prefer- 70 ably metallic, and between it and the ceramic refractory wall 1M8 loose material 3I2 of high thermal insulating capacity is positioned.

In the operation of modern water tube steam boilers, it is somewhat of a general practice to 7 iii give an entire boiler unit a hydrostatic test while it is out of service. When such a test is conducted, the boiler superheater is usually flooded, and water remains in the superheater tubes unless they are arranged to have proper connec tions to drainage. At other times when. the fire is drawn there is a tendency for vapor to condense in the superheater tubes, and this action may result in excessive accumulations of condensate in multiple loop superheaters where the tubes are arranged vertically or when any section is lower than a section to which it delivers steam. In its looped portions: accumulations of water may maintain a relatively low temperature, while an adjoining unsubmerged portion may have highly heated steam in it when no steam flow exists. The consequent differential expansions would set up stresses in the tube and distort it and it might also be weakened or burned.

After steam pressure has been built up, in a boiler not equipped with the bleed structures herein described, and that pressure is sufficient to overcome the resistance of the non-return and stop valves to permit delivery of the steam to the steam main, the flow initiated through the superheater will carry water through it, perhaps in all flat coils. The water carried through will come in contact with highly heated tube portions and there will be a resulting quick change in temperature, likely to cause further distortion of the tubes and loosening of the connections between those tubes and associated headers or drums. Those not cleared of water have no steam flow and may overheat before the water evaporates. By draining the water out during the preliminary heating and the pressure raising stage of the boiler operation, all metal parts are kept within a relatively close temperature range so that distortion and warping of the tubes, and leakage due to loosening tube connections, or possibly burning, will not occur. Warping of the tubes and tube distortion not only place undue stresses on the tube connections, but they also disturb the predetermined tube spacing necessary for best heat absorption, and the best superheating results.

What is claimed is:

1. In combination with a steam boiler, tubular superheater sections through which steam flows successively and at considerable velocity, and constantly open bleed structures communicating with the lower parts of said sections and having steam deflecting parts so acting upon the moving steam that velocity developed efiects prevent such excessive amounts of steam from flowing through the bleeds that the operation of the superheater would be impaired, each of said structures presenting a bleed passage having a flow area smaller than that of the superheater section with which it communicates but large enough to always permit the draining of condensate or other liquid from the sections.

2. In combination with a steam boiler, serially connected tubular superheater sections through which steam flows successively and at considerable velocity, and constantly open bleed structures of flow areas less than the superheater sections, said structures separately communicating with said sections and having angled steam deflecting parts so acting upon the moving steam that velocity developed efi'ects prevent such excessive amounts of steam from flowing through the bleeds that the operation of the superheater would be impaired, said structures permitting the draining of condensate or other liquid from the sections.

3. In fluid heat exchange apparatus, a plurality of looped and serially connected tubular sections so arranged that their loops present succeedingly lower pockets in which condensate or other liquid might collect, and by-pass liquid drain-s each individually connecting a pocket to a succeeding tubular section for permitting liquid to pass to said succeeding section without by-passing an excessive amount of vapor, said drains being located at the lower parts of the sections and having flow areas which are smaller than the flow areas of the tubular sections.

4. In a draining superheater, serially connected tubular sections through which steam passes successively, means so connecting the sections that the superheater presents pockets into which condensate or other liquid may fiow, and constantly open bleed means including vortex chambers communicating with the lower parts of the pockets for draining said pockets without permitting such flow of steam therethrough that the elfectiveness of the superheater is impaired, said bleed means having outlets in succeeding parts of the superheater, each of said bleed means having an inlet fiow area which is smaller than the flow area of the tubular section and the vortex chamber with which it is connected.

5. In a draining superheater, tubular sections including a bank of steam conducting tubes extending across a gas pass, said tubes being looped with each loop including vertically extending legs, means providing for the supply of steam under pressure for passage through; a series of the loops in succession, a superheated steam outlet with which the tubes communicate, means connected to said sections and forming pockets positioned at successively lower levels toward the outlet and arranged to communicate with adjacent loops so that liquid may flow thereinto from the loops, and means whereby any liquid in a pocket may drain to the succeeding and lower level pocket, steam flow from pocket to pocket, said last means being of such .745

flow capacity as to restrict.

6. In a superheater, looped tubes through which steam passes in succession, said looped tubes including vertically extending legs, a steam outlet with which the tubes communicate, a50

plurality of pockets arranged at successively lower levels toward the outlet, the pocket freely communicating with the tubes and so associated therewith that every one of said tubes connecting two pockets leads to an outlet pocket at a level lower than that of its inlet pocket, and liquid outlet means connecting each pocket to a space in which the fluid pressure is less than that in the pocket, each of said liquid outlet means having a flow area smaller than that of the tubes associated therewith and the liquid outlet means being so arranged with reference to the tubes and the pockets that all pockets in the superheater are drained.

7. In a convection superheater, a group of upright superheater tube sections spaced apart, means for connecting the upper and lower ends of said sections so that steam fiows through consecutive sections in series, the steam flowing upwardly in alternate sections and downwardly in intervening sections, said connecting means forming consecutive chambers arranged in series at the lower ends of the sections, each chamber connecting an upflow section to an adjacent downflow section, constantly open liquid connections of much smaller diameter than the tubular sections, each of said connections joining one of said chambers to such an outlet position that there is an appreciable pressure drop between each chamber and the outlet position to which it is connected, said liquid connections functioning to permit the flow of water from said. chambers without permitting excessive steam flow thereafter, and means for connecting said group of sections to a source of steam.

HOWARD J. KERR.

. CERTIFICATE OF CORRECTION. Patent No. 2,221,871. November 19', 19J o.

HOWARD J. KERR.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, sec- 0nd column, line hit, for the word "header" read -headers-; page 5, first column, line 50, before "and" insert a comma; page LL, second column, lines 1411;, 14.5, and 1+6, claim 5, for "and lower level pocket, steam flow from pocket to pocket, said last means being of such flow capacity as to restrict," read -and lower level pocket, said last means being of such flow capacity as to restrict steam flow from pocket to pooket,-; line 52 claim 6, for "pocket" read --pockets-; 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 Officea Signed and sealed this 18th day of March, A. D. v1911.1.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents.

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