US2172227A - Fluid heat exchange apparatus - Google Patents

Description

Sept. 5, 1939. T. B. STILLMAN 2,172,227

FLUID HEAT EXCHANGE APPARATUS Filed July 16, 1935 4 Sheets-Sheet l ED INVENTOR. E Thomas B Stillman ATTORNEY.

Sept. 5, 1939. T. B. STILLMAN FLUID HEAT EXCHANGE APPARATUS 4 Sheets-Sheet 2 Filed July 16, 1935 Flgz V INVENTOR. Thomas B. Stillman ATTORNEY.

P 1939- 'r. B. STILLMAN FLUID HEAT EXCHANGE APPARATUS 4 Sheets-Sheet 3 Filed July 16, 1935 INVENTOR. ThomasB. Stillmazz ATTORNEY.

Sept. 5, 1939. s 2,172,227

FLUID HEAT EXCHANGE APPARATUS Filed July 16, 19:55 4 Sheets-Sheet 4 INVENTOR. m omas B Stillman ATTORNEY.

3.3 absorbing surfaces of the vapor Patented Sept. 5, 1939 UNITED STATES PATENT OFFICE FLUID HEAT EXCHANGE APPARATUS Thomas B. Stillman, South Orange, N. J., assignmto The Babcock & Wilcox Company, Newark, N. J., a corporation of New Jersey Application July 16, 1935, Serial No. 31,569

3 Claims.

This invention relates to fluid heaters. It will be apparent as the description proceeds that the invention is especially applicable to power apparatus for use on ships. However, it is to be 5 understood that in so far as certain of its broader suited for installations where space and weight are important factors.

A further object is to provide a direct-fired vapor superheater wherein the superheat temperature may be quickly varied at will, and wherein the wall structure and heat absorbing surfaces are protected against the destructive action incident to high operating rates.

A further object is to provide a direct-fired vapor superheater wherein a bank of vapor gencrating tubes protects the superheating tubes from the radiant heat of the flame and wherein the surface area of the vapor generating tubes is as small as practical, consistent with the protection of the superheater.

A further object is to provide a vapor generator furnace of improved form which is capable of burning the maximum amount of fuel per unit of combustion chamber space and wherein the combustion chamber is delineated by the heat rator.

A still further object is to provide an improved means for supporting the tubes of a superheater.

These and other objects are effected by my invention as will be apparent from an examination of the following description and claims, taken in connection with the accompanying drawings, in which:

Fig. 1 is a vertical sectional view of a steam superheater furnace unit constructed in accordance with the present invention;

Fig. 2 is a view similar to Fig. 1 and illustrating a modified form of construction;

Fig. 3 is a fragmentary sectional view taken on the line 3-3 of Fig. 2; and illustrating an imin Fig. 1 and illustrates more clearly the pipe connections to the drums and headers and the supporting construction for the furnace; and

' Fig.5 is a view similar to Figs. 1 and 2 and illustrating a further modived form of superheater furnace unit.

As will appear more fully as the description proceeds, the type of apparatus disclosed in the accompanying drawings is used to superheat water vapor generated in an independent boiler unit operating with fuel burning means which are 10 controlled independently from the burners of the superheater furnace and this type of apparatus may therefore be termed a separately-fired superheater furnace unit.

Referring now in detail to the construction il- 15 lustrated and particularly to the embodiment of my invention disclosed in Figs. 1 and 4, the reference numeral Ill indicates, in its entirety, a separately-fired superheater furnace unit which includes a relatively small combustion chamber II. The chamber II is defined by a relatively high side wall I2, a relatively low side wall l3, an upwardly inclined bottom wall I, a rear wall l5 and a front wall 16.

A plurality of oil burners I! are mounted in the front Wall and they are operated to introduce fuel oil and air into the combustion chamber in a manner well known. It is to be understood at this point that, while I have elected to show a furnace fired by oil, my invention is not limited thereto in so far as all of its aspects are concerned, for other fuels may be used and other means may be provided for burning the fuel without departing from certain of the broader aspects of my invention. The burners I! are of a type and capacity and are so arranged as to be capable of burning the maximum amount of fuel per unit of combustion chamber space.

In accordance with my invention I provide a superheater l8 in the upper portion of the unit I0, the surface area of which comprises the major portion of the heat absorbing surface of the unit. The superheater consists of an inlet header IS, an intermediate header 20, an outlet header 2|,

3. group 22 of return-bend tubes connecting the 45 inlet and intermediate headers, and a group 23 of return-bend tubes connecting the intermediate and outlet headers.

I also provide a means for protecting the superheater and walls of the furnace from the de- 50 structive action resulting from the relatively high rate of combustion in the relatively small combustion chamber l I. This means is shown as being in the form of a steam generating section having as small area of heat absorbing surface 55 superheater. I

The steam generating section comprises an upper steam and water drum 26 positioned at the upper end of the high side wall it, a lower water drum 26 positioned at the upper end of the lower side wall I 3, and a relatively small bank of steam generating tubes 2'! connecting the steam and water drum 25 with the water drum 2t and being inclined downwardly from the drum 25 to the drum 26 and extending across the upper and outlet side of the combustion chamber ii. The steam generating section also comprises a water drum 28 positioned at the lower end of the high side wall it, a row of downcomer tubes 29 within the high side wall it and. connecting the water space of the steam and water drum 2%? with the water drum 28, and a row of wall cooling tubes 30 at the combustion chamber side of the high side wall I2 and connecting the steam and water drum 25 and water drum 28, and the wall tubes 30 being curved at their upper ends as indicated at 3! to provide radial entrance into the drum 25 at points spaced from the points of entrance of the downcomer tubes 29 and also to provide for the expansion of the tubes 36 due to heat. The curved portions 35 also serve to protect the drum surface between the tubes El and the tubes 29. The steam generating section also comprises a row of wall cooling tubes 32 extending for the width of the bottom wall i i and for the height of the low side wall it, and directly connecting the drum 28 with the drum 26.

The downcomer tubes 29 are of suficient size and sufficient in number to provide adequate circulation through the wall cooling tubes 30 of the high side wall i2, and through the wall cooling tubes 32 of the bottom wall it and low side wall It to the water drum 26 and through the bank of steam generating tubes 27 to the steam and water drum 25.

The downcomer tubes 29 and the wall cooling tubes 32 provide both for cooling the wall structure defining the combustion chamber and for the unidirectional flow of fluid through the bank of steam generating tubes 2?. The ratio between the area of heat absorbing surface of the steam generating section to that of the superheater section is unusually low, and this is made possible by providing for this unidirectional flow of fluid through the bank of steam generating tubes '21, as will presently appear.

The primary function oi the bank of steam generating tubes 2V is to shield or protect the superheater BS from the radiant heat of combustion; and, in order to maintain the desired low ratio between the heat absorbing surface of the generator and that of the superheater while securing an efficient screening effect, it is necessary that the tubes forming this bank be small as and as few in number as is practical. If it were not for the fact that one way flow of fluid is provided through the bank of steam generating tubes 21, the bank would have to be deep enough to produce a sumcient difference in temperature between the tubes at the combustion chamber side and the tubes at the superheater side to provide for natural circulation between drums 25 and 26 through the bank. Such a construction would materially increase the heat absorbing surface of the bank of tubes and would also cool the furnace gases to such an extent that the desired high temperature of superheat could not be obtained. The unidirectional flow of fluid through the bank 21 could probably as ispractical, consistent with protection of the be provided by outside circulators between the drums 2b and 26; but this latter is not desirable because such circulators would occupy additional space in the boiler room.

In addition to the fact that the downcomer tubes 2% and row of wall cooling tubes 32 perform the novel dual function of protecting the furnace walls and of providing for the unidirectional flow of fluid through the bank of steam generating tubes 21; other features of novelty are present in the particular arrangement of the tubes to perform these functions in a highly emcient manner. By providing continuous tubes from the drum 28 to the higher drum 26, a portion of which is disposed in the vertical side wall it, a positive flow of water is assured through each of the fioor tubes, the head developed by the vertical portion overcoming the friction of the relatively long horizontally inclined portion. Also, by providing a junction header 26 at the upper end of the tubes 32, and an increased flow area in the bank of tubes 21 over that oil the tubes 32, the resistance offered to the unidirectional circulation flow oi fluid is reduced in that portion of the circuit where the steam-water ratio is highest, thereby assuring again a more positive circulation through the floor and wall tubes.

The separately-fired superheater furnace unit ii] is particularly suitable for applications where space and weight are at a premium, for example, in connection with steam generating apparatus for use in ships. From an examination of Figs. 1 and 4 it will be observed that the furnace unit it is substantially rectangular in cross section, with the steam generating section occupying the lower portion and one side of the rectangle and defining a combustion chamber which is trapezoidal in shape, and the superheater iB being disposed in the remaining space of the rectangle which lies laterally of the steam and water drum 25 and above the inclined bank of tubes 21. This arrangement of the parts provides a highly compact unit and the superheater requires approximately no more head room than is required by the steam and water drum and requires no more width than that required by the combustion chamber. It is also noted that a highly compact economizer 35 is disposed above the superheater section and occupies very little head room.

The economizer 35 is provided with an inlet 36 which may be connected to a feed waterv pump (not shown), and an outlet 31 which is connected to the steam and water drum 25 by a pipe 38. The inlet header i9 of the superheater is connected by a pipe 39 to a pipe 40 and the latter is in turn connected to the steam outlet M of the steam and water drum 25 by a pipe 42 and to the major source of low-temperature or saturated steam by a pipe $3. The major source of steam is one or more steam generators (not shown). The outlet header 2| is connected to a pipe 46 by a pipe 65, and the pipe 46 continues to the point of use of the steam, for example, a steam turbine (not shown). A valve 46 is provided for controlling the flow of steam from the drum 25 to the pipe M and a valve ll controls the flow of steam from the steam line 43 to the pipe to. A valve 48 controls the flow of steam from the pipe 40 to the inlet header IQ of the superheater and a valve 50 controls the flow of steam from the outlet header 2! to the pipe M. A by-pass valve 5! connects the pipes MI and it, and, when opened, permits low temperature or saturated steam to flow direct to the turbine, and when closed, causes the steam to flow through the superheater to the pipe 44.

With the piping and arrangement of valves shown, the ship propulsion means may receive either low temperature steam from the pipe 43 or high temperature steam from the superheater and pipe 45. Under normal operation the steam from the pipe 43 and drum 25 flows through the pipe 48 and pipe 39 to the superheater, and from the superheater through pipe 45 to pipe 44 to the point of use. To secure this operation, valves 46, 41, 48, and 58 are open and valve is closed. If, for example, in starting up the turbine or in reversing the ship, it is desired to use saturated or low temperature steam, only the pipe 43 may be connected to the pipe 48 and the latter to the pipe 44, valves 41 and 5| being opened and valves 46, 48 and 58 being closed. Under such operation, the superheater would be taken off the line, a change which can be quickly and effectively accomplished with the expresstype of construction shown due to the water cooling of the combustion chamber and the readily controllable oil burners H.

The superheater furnace unit III is suitably supported from the shipstructu're by means of frames disposed at each side of the furnace. Each of the frames comprises a column 60 supported at its lower end by the ship structure (indicated by the dot and dash line BI) and supporting at its upper end the steam and water drum 25, a column 62 also. supported at its lower end by the ship structure 6| and supporting at its upper end the intermediate header 28, and struts 63 and 64 connecting the columns 68 and 62 respectively. Each frame structure also comprises a relatively short column 65 supported at its lower end by the ship structure 6| and connected to the column 82 by struts 56 and 61.

The side casing structure 68 of the furnace is secured to the columns in a manner well known, and the ends of the headers l9 and 2|, and water drum 26 extend through openings provided in the side casing and are supported thereby. The water drum 26 is also supported by means of a beam 68' connecting the struts 61 at opposite sides of the furnace. The inlet header I9 is supported intermediate its ends by means of lugs 69 and fixed to the drum 26 and header l9 respectively, and suitably secured together. Likewise, the intermediate header 2| is supported intermediate its ends from the inlet header I9 by means of similar lugs 1| and 12 secured to the headers 2| and I9 respectively, and also secured together. Brackets 13 and 14 are secured to the drum 25 and header respectively, and spaced beams 15 are secured at their ends to the brackets 13 and 14 respectively, and serve as supports for the economizer 35. The return-bend ends of the groups 22 and 23 of superheater tubes are supported by plates 16 depending from an air-cooled beam structure 11 carried at its ends by the beams 15, just described.

Referring now to the modification of my invention shown in Figs. 2 and 3, it will be observed thTt I have shown a superheater furnace unit Illa which comprises substantially the same novel elements as that of the previously described embodiment, and the elements, with the exception of the superheater |8a, are constructed and arranged in substantially the same manner. The superheater |8a shown in Figs. 2 and 3, comprises an inlet header 88 and an outlet header 8| and intermediate headers 82 and 83. A group 84 of return-bend tubes connects the inlet header 88 with the intermediate header 82; a group 85 of return-bend tubes connects the intermediate headers 82 and 83; and a third group 86 of return-bend tubes connects'the intermediate header 83 with the outlet header 8|. It will be observed from an examination of Fig. 3 that the intermediate headers 82 and 83 are arranged at one side of a gas pass 81 and that the inlet and outlet headers are arranged in spaced relation in the gas pass and above the groups of return-bend tubes, with the outlet header at the side of the pass opposite the intermediate headers 82 and 83. All of the headers are suitably supported by the furnace structure. The outer return-bend ends of the tubes are supported by plates 89 depending from the header 8| and having openings therein, through which the tubes extend. A similar piate depends from the header 88 and serves to define a side of the gas pass 81. This construction and arrangement provides a highly compact and efiicient superheater and eliminates the necessity of extra supports for the groups of tubes which, if provided, would involve extra expense and complications and. interfere with the proper flow of gases through the pass 81. An additional advantage of this construction is that the headers 88 and 8|, beoing exposed to the hot gases in the pass 81, provide additional superheater surfaces.

In the modification shown in Fig. 5, it will be observed that I have included therein a large number of the advantageous features disclosed in the previously described modifications, and have shown a construction which may be profitably used in certain installations. Instead of introducing the fuel through the front wall ofthe furnace as was done in Figs. 1 and 2, the burners |1b are shown as introducing the fuel through the high side wall I212. The high side wall is not water cooled as was the case in the previously described modification and the downcomer tubes 29b extend through a space 98 at the side of the wall |2b which is provided for conducting preheated air to the burners. The tubes 29b connect the steam and water drum b with a water drum or header 28b, shown as being square in cross section. The downcomers 29b supply the header 281) with the water and a row of wall cooling tubes 32b connect the header 28b with a water drum 26b and extend for the width of the fioor I41) and for the heighth of the lowside wall |3b, as was the case in the previously described modification. The water drum 28b is connected to the steam and water drum 25b by means of a bank of steam generating tubes 21b having an area of heat absorbing surface relatively small when considered with respect to the area of the heat absorbing surface of the superheater |8b. Thus, the modification shown in Fig. 5 provides for the unidirectional flow of fluid through the wall cooling tubes 32b and the bank of steam generating tubes 21b.

The superheater |8b is shown as comprising two sections 9| and 92 respectively; the first section 9| being disposed immediately above the bank of steam generating tubes 21b and being provided with an inlet header 92' and an outlet header 93 and an intermediate header 94, which headers are connected by rows 95 and 96 of return-bend tubes. The section 92 of the superheater consists of a junction inlet header 91 and a junction outlet header 98 connected by loop tubes 99 (of the superheater section 92) arranged for parallel flow of steam between the headers. By this construction and arrangement the direction of flow of the steam in the section 9!, which is nearer the source of heat, is parallel to the gas flow, thereby providing the maximum protection for the superheater tubes adjacent the fire; and the direction of fiow of steam through the section Q2 of the superheater,

which is remote from the source of heat, is counand Mb and connected to the space 98 for con-' ducting the hot air to the burners ilb.

While I have shown my invention in only three forms, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various other changes and modifications without departing from the spirit thereof and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the, appended claims.

Iclaim:

l. A separately fired superheater comprising a furnace and a steam superheating system of commensurate capacities, a natural circulation system of steaming ability below the capacity of the superheating system and incorporated as a protective means for the superheater, each of said systems having a bank of tubes disposed in a single gas pass across the furnace outlet in a manner to be subjected to a uniform transverse fiow of hot gases throughout, the bank of tubes of the natural circulation system being in advance of'the other to act as a radiant heat shield, a steam and water drum at the highest location in the natural circulation system, combined wall cooling and floor cooling tubes discharging into the bank of tubes of the natural circulation system, downcomers receiving water from the drum and delivering to the combined tubes, and other wall tubes connected directly to the drum andlocated between the furnace and downcomers for shielding the latter from the heat of the combustion chamber.

2.1m a single pass separately fired {superheater, a. furnace, a steam and water drum,

horizontally inclined steam generating tubes extending over the furnace and across the path of the furnace gases'passing therefrom, a water drum positioned at the side of the furnace opposite the steam and water drum and communieating with the lower ends of said tubes, combined furnace floor and wall cooling tubes acting as parts of connections between the water space of the steam and water drum and the inlet ends of the generating tubes, means for burning fuel in the furnace, superheater inlet and outlet headers, an intermediate header positioned above the inlet and outlet headers, means for connecting the steam space of the steam and water drum to the inlet header, means for connecting the inlet header to an independent source of steam, a bank of superheater tubes including U-shaped tubes directly connecting the inlet header and the intermediate header, and similar U-tubes directly connecting the intermediate header and the outlet header, the latter U-tubes being shorter than the former and nested therein, all of the superheater tubes extending transversely of the path of the furnacegases to constitute parts of a single pass installation.

3. A combined steam generating and-separately fired superheater unit comprising, in combination; means defining a furnace combustion chamber including a high side wall, a lowside wall opposite the highside wall, and a floor upwardly inclined toward the low walland connecting the lower ends of the high and low side walls; fuel burning means; a steam generator including a steam and water drum at the upper end of the high side wall, a submerged drum at the upper end of the low side wall, a small bank of steam generating tubes directly connecting the water drum and the steam and water drum and extending upwardly in a single gas pass across the path of the furnace gases, a water chamber at the lower end of the high side wall, a row of outside downcomer tubes positioned along the high side wall and connecting the water space of the steam and water drum with said water chamber, and a row of combined floor and wall tubes extending upwardly along the low side wall and connecting said water chamber to the water drum; and a superheater having tubes in the furnace setting so arranged with respect to the combustion chamber that the superheater is protected from the radiant heat of combustion by the bank of steam generating tubes, the superheater tubes and the steam generating tubes being so arranged that the furnace gases contact therewith entirely within a unidirectional single gas pass.

THOMAS B. STILLMAN.

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