US2206704A - Elastic fluid generator - Google Patents

Description

ELASTIC FLUID GENERATOR Filed June 28, 1939 5 Sheets-Sheet 2 Inventory: Anthong J Ner-ad,

His Attorney.

July 2 1940. A. J. NERAD ELASTIC FLUID GENERATOR Filed June 2a, 1959 3 Sheets-Sheet 5 glu/www1', Anthonyv J. Nerad,

Patented July 2, 1940 ELAsrrcFLUID GENERA'roRw i p Anthonyll. Nerad, Schenectady, NAI., assgnor to General Electric "Confi'fpanna corporation of New York npplicarionsune ze, measeriaiNo.281,688 i ie claims., (01,"122-{235} `'Ihe present invention is a continuation `in part of my application Serial No.\174,482,`ledNoveml ber 13, 1937, andrelates to `elastic fluidi genen ators, especially mercury boilersfor generating 5 mercury vapor for operating elastic fluidturbines. l

i The combustion gases which are discharged from the combustion or radiation space of `boilers have high temperatures. Therefore to obtain good boiler efliciency, `convection `zones or spaces must be provided to cool the combustion gases, In order to obtain good `heat transfer the tubes `or heating elements located? within the `radiation andconvection spaces may be filled enf ,15 tirely with liquidi i This, however, lwouldrequire `a `prohibiting amount of liquid inthe `case of mercury boilers because the tubes'must be made Vwide `enough `to prevent plugging. In mercury lboilers the tubes at least in the convection space are ordinarily charged with mixtures of vapor and liquid.` In these cases it is important lthat the inner surfaces of the tubes are wette-d bythe mercurybecause a mixture of liquid and1 vapor has good heat transfercompared to a pure liquid only if the inner surfaces of the tubes" arewell wetted, The object of my invention' is to4 provide an `improved 4construction and arrangement of elastic fluid generators, especially `mercuryboilers having heating elements disposed `inwradiation andconvection spacesor chambers, whereby vbetter `eiliciency and economy areobtained.

For a consideration of what I believe to` be novel `and my invention,"attention is directed Vto 335 `the following description and the claims appenddrawings. A

In the drawings, Fig, l represents a front View, partly broken awayg'of a mercury boiler embody-` 40 `ingrny invention; Fig. 2 is a sectional viewalong l-theline 2-2 of Fig; 1; Fig. 3 is a perspective view `of certain parts of Figs. `l and 2, and Fig.I 4 i1- lustrates a modication of my invention.` i Boilers or elastic fluid generators usually ined thereto in connection with the accompanying `cludea drum and heating` elements" connected to the drum and exposed to heat. `The heating elements receive liquid from the drum'and `discharge a mixture of liquid `and vapor into the `drum in which the mixtureis` separated, the

`vapor being discharged to a superheater or to a consumer and the liquid being` recirculated. These boilers are known as natural circulation i `type boilers. They do not employ any mechanical pumping means for forcing the operating `huid through the heating elements, the` iiow of operating fluid through said elements` taking 'place due -to the difference in `gravity between theoperating fluid contained in down tubes not exposed to heat and up tubes `exposed to heat. lThe eliminationI of pumps, `that is, theprovision f5 of boilers whichy may be operate-d without rnechanicalpumping means is` sometimes desirablev `when mercury is used as operating fluid, because of' the high specic weightfof mercury `.and `the consequent difficulties experienced `in the pump- 10 fingiof mercury liquid `by mechanical` pumps. In addition, thefuseof such pumps requires a `great amount ot energywhich reduces the overall eiliciencytoit the` boiler plant. yIn mercury Vboilers 'heretofore built,` the mercurywas discharged from the up tubes4 or heating elements intothei p d-rumat considerable/velocity andfV at a pressure `substantially above the pressure existing within;` lthe .i-drum; i Thelhigh 'velocityl energy contained :in the mixture thusdischarged into the drum 20 wastconverted fintoheat energy within the drum.

-\ Ihave discoveredthat better use may be made of `theavailablevelocity energy of themixture ordinarily discharged directly from the up tubes' .of the `heating elements inte une` drumby using .25 `thisenergyctof pump iiuid, more specifically the samefuid, through another heating element 1o- .cated above the drumfand connected in series between the raforementioned up tubes and the drum. rI-nfother `words, I provide, in accordance with my inventionan arrangement in which the up tubes of: .thel heatingvelernents are `considerably ex,M Htended sothat itheavailable energy of the mix; `ture in fthe portions of `theheating elements which arelocated below `the drum is utilized to` force `35 such mixture through a tube ortubes located l at a Alevel above that of thedrum `or drums. `In `such;arrangement the mixture is ultimately dis- 1chargedfrom theheating elements into the drum `atlow velocityand at apressure only"sligh`tly above that existing within the drum."` q, y.

{willf fe'corne apparent j further below,- an rarraugen;ehi", ,inxaccordancelwith my invention "hasrnanyimportant advantages,` for instance, 45 locatinglffcertain.parts of "the heating elements above the drum, that is,`in the convection` space ,gf thepouei, permits' starting or the poner with gidheatingelements inthe convection space i 3VO operating medium, that is the mercury,-is forced through heating tubes by means ofpumps.

Referring to the arrangement shown in Figs.

walls form a combustion or radiation. space I5' and the upper portion of the walls forms a convection space I6 receiving combustion gases discharged from the combustionspace I5. Connected to the ends of each drum are down tubes .I1 and I8 receiving mercury liquid froml the corresponding drums.r 'I'he down tubes are located outside the furnace walls 'I3 and I4 and their lower ends are branched and connected to heating elements I9,\20,'2I (Fig. 3) located within and lining theffurnacelwalls. The heatingV element I9 includes three tubes 22, 23 and 24 and the heating eleme-nt 2n also includes three tubes 25, 26 and 21. Some of these tubes are connected `in a well known m-anner to the bottom of `the drum tol discharge the mixture of liquid and .Vapor formed in the tubes directly into the` drum, while others of thetubes are connected to heating elements located above the drum.

-More specifically, the central tubes 23 and 26 of tubes arranged transversely to the flow of combustion gases. nIn the present instance, the tubes have a number.` .orV plurality. of hairpin shaped Asubstantially horizontallyy disposed portions forming a zigzagpath .for the 4fluid owingtherethrough. The lower ends or outlets of the tubes lare connected to the drums.

fio

The heating elements or vbank ofY tubes 28, 29,

r3l! and 3| have upper ends connected to a source of supply, inthe present instance some of the wall tubes lin the combustion space, whereas the lower ends of thesetubes 28 to 3I, inclusive, are connected to the vessel. Thus, the flowthrough these tubes is in a downward direction wherefore these tubes may be termed downward flow heating tubes and as they are located in the convection space they constitute downward flow convection heating tubes or elements. The downward flow in the downward flow convection tubes facilitates draining of such tubesafter shut-down and,.what is also important, this downward iiow reduces the density of the mixture` of liquid :and vaporv flowing through the tubes during operation. 'Ihev density is reduced because with the mixture flowing in downward direction the liquid follows the vapor more readily or,l from another viewpoint, the slipbetween the liquid flow and the vapor flow is small as compared with the case of uid flow in upward direction. Reduced density in the convection tubes permits operation of the boiler with a smaller amount of liquid which is an important consideration in mercury boiler design. y

In order to obtain uniform distribution of mercury withinthe. drums, I connect the ends of agroup or bank of tubes to different drums. Thus, while such `bank of tubes receives mercury `fromra single drum it fdischarges mercury into Veter and forms a heating well 63.

several drums. From another viewpoint, some of the tubes or heating 4elements. are connected in series between different ldrums or vessels. This is especially important where the operating fluid consists of mercury and some other subst-ance such as sodium, lithium, aluminum, zirconium,

magnesium and titanium, because the connecting of the tubes of one bank to several drums as- `a header 33 into the drum Il; thetube 30 discharges through `a header 34 into the drum I0,

`and the tube 3I discharges through a header 35 into the drum II.' The headers 32, 33 are located partly outside the furnace wall I3 whereas the headers 34,35 are disposed entirely lwithin the furnace. The arrangement is symmetrical as viewed in Fig. l and also in Fig. 2. The down tube I8 in Fig. 2 conducts mercury liquid from the drum I0 to a pluralityof up tubes 35 and 31. The tubes 36 dischargev into the bottom of the drum, whereas the tubes 31 are connected to heating elements or a bank of tubes 38 located above the drum and arranged symmetrically to the aforementioned bank of tubes 28 to 3|.

Mercury liquid is conducted to the drums from a source, for instance a condenser (not shown) in the case of a vmercury turbine power plant, through a plurality of preheaters. In the present instance a preheater 38 is llocated. betweenV each pair of drums, the preheater 39 has an inlet Q35 conduit 40' connected to a U-shaped channel 4I; the left-hand leg of the channel 4I is connected to a bank of tubes 43. These tubes 43 are disposed substantially horizontally and partly somewhat below the level of the drums. of the tubes 43 are connected to a header 44 which in turn is connected through a connecting member 45 to a header 46 located outside the furnace wall and running along the entire boiler to discharge preheated liquid through a plurality of pipes 41 into the different drums. The right-hand leg of the U-shaped channel 4I is `connected to another bank of tubes 48 arranged similarly to the bank of tubes 43 and discharging into; the same outer header 4B.

In order to assure uniform mixtureof operating uid Within the dilferent portions of a drum, the several preheaters are preferably arranged so as to discharge into different end portions of the drums. between drums I I and I2 discharges into the end portions of the drums II and I2 projecting through the rear furnace wall I4, while the preheater arranged between the drums I0 and II discharges through a header 49 into the end portions of the drums I0 and II projecting through the front furnace wall I3.

The arrangement shown in Fig. 4 comprises a boiler having a cylindrical wall 6l] defining a combustion space 6I and a convection space 62.?

The lower portion of the wallis reduced in diam- Burners 64 and 65 are provided in thejheating well and the lower portion of the combustion space respectively. A heating element 66 in the form of a helical tube is located in the heating well and arranged to line the wall thereof. Another heating ele- 4ment 61 inthe form of a helical tube is located in the combustion space 8| and arranged to line the boiler wall therein.- A third heating-element;

The outlets Thus the preheater located lil) `hairpin-`shapedtubesis located in the convection spacefii` `The heating element 66 in the well has an inlet portion 69 connected to receive mercury liquid from a liquid vapor separating device lll y located outside the boiler at a level near that of the well. Mercury liquid is forced into theheating element 6W5 by means of a pump 'Il having o an inlet connected to the device l@ by a conduit 'll and to some other source of supply, (not shown) by a conduit i3. the heating element 6E in the` well is discharged `therefrom through a conduit 'lil into the upper end` of the hairpin-shaped heating` elements t8,

which latter in turn discharges into the upper end of the heating element l. The lower end `of the heating element @l isconnected by a conduit F tothe liquidvapor separating device lll.

@through theheating element E56 takes place in Thus,` the three heating elements 66, El, (i8 are connected in series with the drum. The ilow upward direction, this element consequently constituting an up-flow heating element, whereas thefllow through the heating elements 621,458 takes place in downward direction, said elements consequently constituting downward flow heating elements `or tubes. 4

During operation mercury flows from the drum 10 through the elements 65, 6B, 6l in the order stated and is discharged in the form of a mixture ofliquid and vapor to the drum l'll. The liquid is recirculated through `the heating elements,

p whereas the vapor is discharged from the device `lll through a conduit lli. During starting the downwardffiow heating elemental?? and 68 are empty of mercury, the` lower end of the element `lil `and the discharge conduit l5 being located above the mercury liquid level in the device lil. Thus,` during starting only the element 65 in the well isiilled with mercury. From the element `66 `the mercury is forced into the down-now elements 6l, 58 by the action of the pump 1l. In casethe boileris operated `without the liquid circulating pump li, mercury is conducted to the downflow heating element only after the liq- `uid. contained in the `element Sii has expanded sufficiently to iill the conduit lll. The burners or fuel andl air supply means 6d, lili may be started simultaneously or consecutively. In case the boiler is operated natural circulation pipe boiler, that is, without the pump ll, it may be` `.preferable to start the burner 65 only after the mercury inthe heating well has expanded sufliciently` to 1cause flow of mercury through the down-flow heating elements Bl, 68. Thus,'where as in the arrangement of Figs. l to 3 the downflow heating elements are located entirely in the convection space, in the `arrangement of Fig. 4 said elements are located partly in the convection space and partly in the radiation space.

summarizing, an elastic fluid generator, in accordance with my invention, includes in addi-y tion to a vessel for containing operating fluid and a first heating element located below the level of the vessel and receiving liquid therefrom, another heating element located at a level above that of the vessel and connected in series between the rst heating element and the vessel. Operating Huid is conducted to the first heating ele- `ment through conduits connected to the vessel.

p The energy of the fluidheated in the first heating elementcauses this fluid to be forced through @the second heating element into the vessel; The

first heating element is located at least partly in the combustion space of the boiler while the sec- Mercury forcedthrough i i ing liquid from the vessel i connection with Figs, l to 3 in which only a few of the first heating elements are connectedlto the bottom of the drum` or vessel, hasthe further advantage of reducing the number of openings that have to be made vin the bottom `of the drum, thus avoiding excessive weakening of the wall of the drum. In a. boiler in which the lower or first heating elements line the wall or walls of the combustion space, an increased output of the boiler is effected by connecting at least some of these wall tubes to second heating elements located above the drums or vessels. As the heating elements near and abovethe level of the vessel maybe empty of operating fluid during the starting operation, a considerable economy in operating iluidsuch as `mercury is attained.

As pointed `out above, in the case of a mercury boiler the mixture of mercury and vapor is discharged from the heating elements above the drums at a pressure only slightly above that existing within the drums. This naturally means little temperature change of the mercury on its path from said heating elements into the vessels.

Itis known that mercury at high temperature dissolves ferrous metal a-nd that this dissolving action is somewhat in proportion to the ternperature change of the mercury. Hence, in mercury boilers as described above, owing to thel small temperature change of the mercury on its path through the second heating elements into the vessel, there will belittle dissolving of fer- 170115 metal. by mercury at the operating temin the above described arrangement, that is,

transverseto the now of combustion gases which results in efficient heat absorption of said second heatingy elements. i

Having described the method of operatic-n of my invention; together with the apparatus which I now consider to represent the best embodiments thereof, I desire to have it understood that the apparatus shown is only illustrative and that theinvention may be carried out byother means.

What I claim as new and Letters Patent of the United States is.'

1. `An elastic fluid generator comprising a radiationsp'ace, a convection space, a liquid vapor separating vessel, a first heatingfelement receiv- Within the radiation space, and a second heating element forming a fluid path of a length `substantially greater than the iiuid path formedby the first element, the second element being disposed substantially entirely within the convec` `tion space and connected .in series between the rst element and the vessel with the upper end of the second element connected to receive heated fluid from the upper end of the first element.

2. An elastic fluid generator comprising a radidesire to secure by A i and being disposed ation space, a convection space,y a vessel for con* i taining operating fluid, a rst heating element located at least partly below the level of the `vessel and arranged to receive liquid from the vessel and being exposed to heat from the radiation space, and a second heating element connected in series between the rst heating element forming a zigzag path for fluid discharged from the .first heating element.

. 3. An elastic fluid generator, including the,

combination of a vessel for containing operating fluid, a iirst heating element located below the vessel and having a lower end for receiving liquid from the vessel by gravity, and a second heating element located above the vessel and connected in series between the first heating element :and the vessel with the upperend of the second element connected to the upper end of the iirst element, the length of the secondheating element being substantially greater than the length of the rst heating element.

4. An elastic uid generator including the combination of a vessel for containing operating fluid, a first heating element located substantially below the vessel and receiving liquid therefrom bygravity, a second heating element connected between the rst heating element and the vessel Vwith the upper end of the second element connected to the discharge end of the first element whereby some of the energy of the fluid in the rst heating element is utilized to force the fluid contained in the first element through the second element into the vessel, the second element forming a zigzag fluid path of a length greater than the length of fluid path formed by the first element. v

`5. An elastic fluid generator including they combination of walls forming a combustion space andl a convection space, a vessel between said spaces, a plurality of first heating elements lining the wall of the combustion space, down tubes for conducting operating liquid from the vessel to the lower ends of the first heating elements, second heating elements located in the convection space and having inlets and outlets, said inlets being connected to the upper ends of at least some of the first heating elements and the outlets being connected to the vessel to utilize some of the energy of the iiuid in some of the first heating elements to pump such fluid through the second heating elements, the outlets of the other first heating elements being connected directly to the vessel.

6. An elastic fluid generator including the coml bination of walls forming a combustion space I and a convection space, a plurality of vessels for in series between the first heating elements. and the vessels, some of the first andsecond heating elements being connected in series between dierent vessels to receive operating fluid from one vessel and discharge heated fluid into another vessel to maintain uniform conditions in the various vessels.

7. yA mercury boiler including the combination of walls forming a radiation space and a convection space, up-tubes lining the walls of the radiation space, downward flow heating tubes disposed in the convection space, means for conducting mercury liquid by gravity to the lower ends of the up-tubes, conduit means connecting the upper ends vof the up-tubes to the upper ends of the downward now. tubes and a vessel located at a level near the lower level of the downward flow tubes for receiving heated mercury therefrom.

8. An elastic fluid generator including the combination of a wall forming a combustion space and a convection space, a liquid vapor separating drum, an up-flow heating element located in the i combustion space below the level of the drum and connected to receive liquid from the drum, a

ldown-flow heating element located at least partly in the convection space at a level above the drum and connected in series between the up-flow heating element and the drum.

9. An elastic iiuid generator including the com bination of a heating chamber, a liquid vapor separating drum, means` including a heating element located in the chamber below the level of the drum and 'connected to receive liquid from the drum for heating such liquid by radiation, a down-flow heating element in the chamber located .at least partly above the liquid level in the drum and having an upper end connected to receive heated fluid discharged from the upper end of the first mentioned heating element.

10. An elastic fluid generator including the combination of a cylindrical wall having a lower portion forming a heating well and a combustion space and an upper portion forming a convection space, a liquid'vapor separating device 10+ cated outside the drum at a height to establish a liquid level above the upper end of the heating well, a first heating element located in the well and connected to receive liquid from the drum, a second heating element in the form of a helical coil lining the wall in the combustion space and having a lower end connected to discharge heated iiuid to the device, and a third heating elementv in the form of aY plurality of series-connected hairpin-shaped tubes located in the convection space and having a lower end connected to the ,f

upper end of the second element and an upper end connected to receive mercury discharged from the iirst heating element.

ANTHONY J NERAD.

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