US1268074A - Surface condenser and method of operating same. - Google Patents

Description

BRNCEL. 0 SURFACE CONDENSERAND METHOD OFOPERATING'SAME.

APPLICATION FILED DEC- 7. I915)- Patented May 28,1918.

2 SHEETS-SHEET 1.

l l l P. A BANCEL' SURFACE CDNDENSER AND METHOD OF OPERATING SAME. APPLICATION FILED DEC. 7,-1915.

Patented. May 28,1918.

2 SHEETS-SHEET 2.

sharp one.

JPAUL A. JBANCEL, OF NUTLIEY, NEW J EIIRSEY, ASSIGNOR T0 HIM-SELF, AND GEORGE H. GIBSON, 0F UPPER MONTGLAIR, NEW J ERSEY.

SURFACE CONDENSER AND METHOD OF OPERATING SAMUEL.

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Specification of Letters Patent. P t t Maw 2 11,

Application filed. December 7, 1915. Serial No. 65,448.

To all whom it may concern:

Be it known that I, PAUL A. BANCEL, a citizen of the United States, and resident of Nutley, in the county of Essex and State of New Jersey, have invented-certain new and useful Improvements in Surface Condensers and Methods of Operating Same, of which the following is a true and exact description, reference being had to the accompanying drawings, which form a part thereof.

My present invention consists in improvements in surface condensers and methods of operating same, and its general object is to increase the operating efficiency of such condensers by a more effective utilization of the energy expended in circulating cooling water through the condenser.

In thenormal operation of an ordinary surface condenser the rate at which steam is abstracted from the gaseous medium in the condensing space varies greatly in different portions of said space. For example, with a surface condenser operating at a fairly high vacuum such as is commonly employed to condense the exhaust steam from turbines and the like, the great bulk of the steam passing into the condensing space is condensed in a portion of the latter adjacent the steam inlet thereto which may be called the active zone of the condenser. This active zone will vary in volume with the conditions of use. In the winter time with light loads it may include not more than ten to twenty per cent, of the total condensing space, while with heavy loads in the summer time when the condensing Water enters the condenser at a substantially higher temperature than it does in the winter time, the active zone'm'ay includefrom forty to eighty er cent, of the total condensin space. he remainder, or inactive zone 0 the condenser is filled with a more or less stagnant mixture of steam with .non-condensable gases and'vapors' commonly referred to as air. It will be understood, of course, that the line of division between the two zones is never an absolutely My invention eflectively utilizes the fact that a substantial economy in condenser operation may be obtained by causing the cooling water to flow with a substantially 1 the active zone than through the tubes higher velocity through the tubes trav-' traversing the inactive zone of the condensing space. The explanation of this economy is found in the conditions governing the transfer of heat from the gaseous medium in the condensing space to the cooling water in the tubes. The rate at which heat is thus transferred depends primarily upon two factors one of which is the conductivity for heat transfer from the gaseous fluid to the metal walls of the cooling water tubes, and the other is the conductivity for heat transfer from the tube walls to the 'cooling water. The first mentioned conductivity varies greatly with the character of the gaseous fluid, being much higher in the case of practically pure steam and much lower in the case of a stagnant rarefied air-steam mixture rich in air than is the last mentioned conductivity. For example, if we assume that the conductivity for heat trans fer per unit of tube surface area to the tube from the stagnant air-steam mixture per degree difi'erence in temperature may be represented by unity, the conductivity for transfer from pure steam to the tubemay be 4000 or more, while the conductivity from the tube to the cooling water may vary from 300 to 750 depending on the water velocity in the tube. These conductivities vary greatly in different condensers and under difi'erent conditions, but the figures given indicate their'order.

llt follows therefore that in the active zone of the condenser the temperature of the metal tube walls approximate that of the steam and the rate at which heat is abstracted is almost directly proportional to the conductivity for heat transfer from the tube walls to the water. The high velocity for the water flowing through the tubes of the active zone is desirable therefore, not only because a large volume of flow is necessary to keep down the temperature of the water, but also because of the well known fact that the tube to water conductivit is increased by increasing the velocity of ow. This increase of, conductivity is due to the agitation of the water and the breaking up of the stream lines which results from causing the water to flow at high velocity through such a restricted channel as is formed by a condenser tube. 1 Any such agitation, such asis produced by an increase in velocity, demands a greater expenditure in energy in forcing the water through, and the expendiint llll l ture of energy per unit of tube area may be considered an approximate measure of the amount ofvconductivity in any tube. In the inactive zone on the other hand, the tube temperature approximates that of the water flowing through the tubes and the rate at which heat is abstracted by the water is almost directly proportional to the conductivity for heat transfer; from the air-steam mixture to the tube walls,

The quantity of the heat abstracted by the tubes in the inactive zone is but a small fraction of the amount of heat abstrated in the active zone and a high velocity of the water through the tubes of the inactive zone is not necessary either to increase the conductivity for tube to water heat transfer, or to prevent an undue rise in temperature in the tit? water flowing through these tubes. The amount of heat abstracted by the tubes in the inactive zone is further diminished by the heat insulating efiect of the films of water on the tubes. In the active zone the steam velocityis high enough to keep the outer tubes swept fairly clear of water of condensation but in the inactive zone the gaseous velocity is not sufficient to prevent the maintenance of water films on the tubes having a considerable heat insulating property. The presence of water films on the tubes of the inactive zone is much less objectionable than would be the presence of such films on the tubes. of the active zone, owing to the diflerencesin the condensing effect and conditions of operation of the two groups of tubes. It is'desirable, therefore, that the tubes of the active zone should be arranged above, or otherwise so disposed with respect to the tubes of the inactive zone that water of condensation drippin ofi of the latter will not fall on the tubes 0 the active zone. I

In the ordinary operation of surface condensers ass-heretofore practised, the water is caused to flow through thetubes in the inactive zone with approximately the same velocity as it flows through the tubes of the active zone. This means that the same or substantially the same energy is expended in forcing the water through each tube inathe inactive zone as in the active zone. In proceeding in accordance with the present invention I cause the circulating water to flow through the tubes of the active zone at a much higher velocity than through the tubes of the inactive zone. By-doing this I am enabled to condense a given amount of steam with a smaller expenditure of energy in driving the circulating pump than was heretofore necessary, ,or bygexpending the same amount of pump driving energy in a more efficient manner I may increase the amount .of condensation which may be secured with a given condenser.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, and the advantages possessed by it, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated in a somewhat diagrammatic manner various forms of apparatus embodying novel features of construction and useful in carrying out my novel method of operation.

Of the drawings:

Figure 1 is a sectional elevation of a surface condenser with cooling water circulating connections thereto;

Fig. 2 is a transverse section taken on the line 2-2 of Fig. 1;

Figs. 3, 4, 5, (i and 7 are each views taken similarly to Fig. 1 illustrating modifications differing from one another in the provisions made either internally of the condenser or externally thereof for effecting the desired circulation of the cooling water.

In the typical surface condenser construction somewhat conventionally illustrated in Figs. 1 and 2, the condenser A is shown as comprising a condensing chamber with an upper inlet A thereto for the steam to be condensed, and a lower outlet A for water of condensation and air. The condensing chamber is traversed by cooling water tubes which connect the water chambers B and C at the opposite ends of the condensin space. As shown, the water chamber B is ivided into separate upper and lower compartments by a barrier G. and the condenser tubes are consequently divided into an upper bank or group of tubes D, and a lower bank or group of tubes D The cooling water is supplied to the two compartments of the Water chamber B by the branches E and E respectively of the delivery pipe of the circulating pump E. The water passing from the two compartments of the chamber B into the undivided chamber C through the tubes D and D escapes from the chamber C through the outlet C. A throttle valve F in the pipe E forms a means by which the amount of water passing through the tubes D may be proportioned to the amount of water passing through the tubes D as desired. The flow through the pipe IE will be so restricted, under all ordinary operating conditions, that the velocity of fiow through the tubes I) will be appreciably less than the velocity of flow through the tubes D, but as alreadv explained the difference between the velocities of flow through the two groups of tubes should ordinarily be less in warm weather than in cold and may advantageously be increased and decreased by manipulating the valve F as the amount of steam to be condensed materially decreases and increases. In the condenser A the inactive zone will no'r ally include the tubes D ber C as well as in the water chamber B, and

these barriers are so arranged as to divide the condenser tubes into three banks or groups D, D and D the tubes 3 serving to convey water passed into the oWer compartment of the chamber C by the tubes D ack to the upper compartment of the chamber B, from which the water thus supplied and the water supplied through the pipe E, passes to the upper compartment of the chamber C through the tubes D. With the arrangement shown in Fig. 3 it will be obvious that the velocity of flow through the tubes D and D will be quite small in com parison with the velocity offlew through the tubes D unless the supply conduit branch E is greatly restricted. With the condenser A there is a waste of energyinvolved in forcing the water past the throttle valve F which may be avoided with the condenser AB. In the condenser'AB each of the two groups of tubes D and D forms a means for reducing the difference in head at the opposite ends ofthe tubes in the other group. With the arrangement shown in Fig. 3 no throttling valve will ordinarily be needed and if used at all should be put in the conduit E rather than in theconduit E In the condenser AC shown in Fig. 4, the water chamber B is divided by two barriers G into three compartments with a branch of the cooling water supply pipe connected to each compartment. As shown the extra branch E of the delivery pipe is connected to the intermediate compartment, and the flow through this branch may be throttled more or less by a throttling valve F. The single barrier provided in the water chamber C is so located that the water passing through the water chamber C from the lower compartment of the chamber B through thebank of tubes D is returned to the intermediate compartment of the chamber B through the tubes D The tubes D leading from the intermediate compartment of the chamber B, and the bank of tubes D leading :t'rom the upper compartment of the chamber l3 both deliver into the upper compartment cf the chamber C. With the arran ement described a short circuit or by-pass is ormed about tubes D and D when the valve F is opened, and the flow resistance of this short acabre circuit or by-pass may be varied by varying the throttling efi'ect of the valve F, and by entirely closin the valve F the short circuit or by-pass is e iminated. The arrangement shown in Fig. 4 makes it possible to maintain a wide difi'erence between the rates of flow through the upper tubes D, on the one hand, and through the lower tubes D and D on the other hand, while varying the velocity of flow through the groups of tubes D practically throughout the range between the high velocity in the tubes D and the low velocity in the tubes D and D The condenser AD shown in Fig. 5 differs from. the condenser AG by the insertion of a barrier G in the water chamber B above the uppermost barrier Gr of Fig. 4, and by the provisions of the cooling water outlet 18 from the upper compartment of the chamber B, and the elimination of the external cooling water outlet from the chamber C. These changes have the efiect of dividing thecondenser tubes into four groups or banks of which the bank or group D not employed in the condenser AC serves to convey water from the upper compartment of the chamber C to the uppermost compartment of the chamber B.

The regulation of the distribution of cooling water to the condenser through branch supply pipes by the action of a throttling valve involves a certain loss of energy in the circulating system which may be avoided in whole or in part by the use of a plurality of circulating pumps adapted to have .slightly different and somewhat variable delivery pressures, in lieu of a divided and throttled outlet from a single circulating pump. For instance, as shown in Fig. 6, a condenser AB which may be identical with. that shown in Fig. 3, receives cooling water through the upper compartment of the chamber B from a pump 1E through its undivided outlet pipe E, while water is supplied to the lower compartment of the chamber B from ltd a single pump 6 through its undivided dc.-

livery plpe c.

In Fig. 7 the condenser AC shown is identical with the condenser shown in Fig. 4:, but issupplied with cooling water in part by a pump 1E having its undivided delivery ipe connected to the'upper compartment 0 the chamber B, and in part by a second pump 6 having one branch 6 of its delivery plpe con nected to the lower compartment of the chamber B and a second branch e connected to the intermediate compartment of the chamber B. A throttling valve is located in the pipe a lit will'be apparent to those skilled in the art that various modifications of the apparatus for and method of eondensin steam herein disclosed in detail may be ma e without departing from the spirit cl. my invention. I

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Having now described my invention, what I claim as new and desire to secure by Letters Patent is,

1. The method of condensing steam in a surface condenser which consists in forcing one stream of cooling water through the tubes traversing the portion of the condensing space adjacent the steam inlet at a relatively high velocity and in forcing a diflerentstream of cooling water through the tubes traversing a portion of the space more remote from said inlet at a lower velocity.

2. The method of efliciently utilizing the energyv expended in circulating cooling water through the tubes of a surface condenser which consists in expending a substantially larger amount of such energy per unit oftube area in the portion of the condensing chamber adjacent the steam inlet than in the portion of said space adjacent the air outlet, and in varying the amount of such energy expended in an intermediate portion of said space as the load varies.

3. The method of efliciently utilizing the energy expended in circulating cooling water through the tubes of asurfac condenser which consists in expending a substantially larger amount of such'energy per unit of tube area in the portion of the condensing chamber adjacent the steam inlet than in the portion of said space adjacent the air outlet, and in varying the amount of such energy expended in an intermediate portion of said condensing chamber as the conditions of operation vary.

4. A surface condenser having a condensing space-with a steam 'inletrat the upper end thereof, cooling water tubes traversing said space and circulating connections thereto, said tubes and connections being so relatively arranged and proportioned as to provide upper and lower parallel paths of flow, the expenditure of energy per unit of tube area for 'causing the fioweo'f cooling water being greater in the upper path than in the lower path.

5. A surface condenser having a condensing space with a steam inletiat the upper end thereof, cooling water tubes traversing said space, and circulating connections thereto, said tubes and connections being so relatively arranged and proportioned as to provide upper and lower parallel paths of flow, for separate streams of cooling Water through different groups of tubes, with the loss of head per unit of tube'length greater in the upper path than in the lower.

6. A surface condenser having a condensing space with a steam inlet thereto, cooling water tubes traversing said space and circulating connections to said tubes arranged to form a single circulating system comprising multiple paths of flow across said space through said tubes, the different paths being equal in length to different multiples, reipectively, of the length of an individual tu e.

7. A surface condenser having a condensing space with a steam inlet thereto, cooling water tubes traversing said space and circulating connections to said tubes arranged to form a single circulating system comprising multiple paths of flow across said space through said tubes,with the different paths comprising different numbers of tube passes.

8. A surface condenser having cooling water tubes forming multiple paths for the cooling water, means for subjecting some of said tubes to a greater difference in internal pressure or loss of head per unit of length than others, and means providing a by-pass of regulable flow resistance about some of said tubes.

9. In a surface condenser having cooling water tubes forming multiple paths for the cooling water, means for subjecting some of said tubes to a greater difierence in internal pressure or loss of head per unit of length than others, and means providing a by-pass about some of said tubes.

10. A surface condenser comprising a condensing space, a steam inlet, tubes traversing said condensing space, means for passing water through a part of said tubes adjacent to said inlet at a high velocity, means for passing water through another part of said tubes at a lower velocitv than through said first mentioned tubes and means to vary the relative number of high and low velocity water tubes.

PAUL A. BANOEL.

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