FIELD OF THE INVENTION
The invention generally relates to a tube nest layout in a single pass steam condenser to achieve uniform steam distribution and equalized pressure drop across different tube bundles from all directions around the tube nest. The invention more particularly relates to a method of generating an optimized tube nest layout for compact single pass condenser.
BACKGROUND OF THE INVENTION
It is known that a steam condenser is to condense steam from exhaust of a low pressure steam turbine. It consists of number of cooling tubes, as high as 30,000, for a large power plant application. Performance of a condenser is mainly dependent on arrangement of the cooling tubes which is called tube layout. It significantly influences the steam distribution to all the tube bundles venting of non-condensable gases, deaeration of condensate and pressure loss across tube nest. Condensers can be of single pass or two pass type depending on the plant layout constraints including availability of height for locating the equipment below the turbine. For a given number of tubes, if the height of condenser is reduced, then density of tubes will increase. This is called compact tube layout which is being used where there are constraints in availability of height of condenser.

Indian Patent No.245800 describes a tube nest layout of a compact two pass condenser with improved tube nest configuration having converging vertical and horizontal flow passages in the second pass and the first pass respectively. This prior art layout has the limitation of its applicability to two pass condensers.
US Patent No.5,649,590 describes tube layout in the form of radiating spikes. Some of the spikes split at least once into the branches and wherein said spikes radiate from a tube containing area that forms a circular ring. This layout has the possibility of air pocket formation in the spikes with the steam entering from both sides of the spike. Moreover, compactness of the layout cannot be achieved by this concept.
Another version of tube nest layout has been described in US Patent No.5960867 wherein the tube nest is spaced from a bottom surface and the side walls of the condenser to allow flow of steam from all directions into the tube nest with a reduced velocity. The extraction opening is disposed below the center of gravity of the outer circumference and the width of each of the flow passages increases towards open outer end. The area ratio and length of the flow passage increase towards the central axis of the tube nest. The advantage claimed are reduced pressure loss and improved non condensable evacuation. With this layout concept, the height of the condenser becomes comparatively high and thereby, affecting compactness.
US Patent No.6,269,867B1 teaches a tube nest which has a mass region of cooling tubes and plurality of tube bundles with flow passages. A non-condensate gas extracting tube is arranged among the cooling tubes in the massed region. A cooling unit or a steam condensing chamber for condensing steam contained in non-condensable gas extracting tube is arranged in the massed region. A discharge flow passage is formed at least partially in the tube next so as to enable the non-condensable gases from the cooling unit or the steam condensing chamber to be

discharged outside of the condenser, whereby condensing efficiency of the steam contained in the non-condensable gases which flow into the cooling unit or the steam condensing chamber is improved. This layout also carries the disadvantage of comparatively a taller condenser.
Patent No. US 7,481264B2 discloses a steam condenser having heat transfer tubes arranged in two upper groups and at least two lower groups with gap between each other. A baffle plate is placed at lower part between two lower groups obstructing flow of steam extends horizontally. Between upper and lower heat transfer groups, inter tube group inundation prevention plates extend horizontally. In each heat transfer group an enclosure part extends to guide gas from enclosure part to outside of the container through a gas extraction duct.
This layout has zones having potential for entrapment of non-condensable gases that affect the overall heat transfer capability of a condenser.
EP 150361A2 describes a condenser tubes arrangement in upper tube and lower tube bundle in U-shaped vertical sections. At a portion where the condenser tubes are not arranged between upper and lower tube bundles, steam flow prevention plates are provided at both right and left sides of the non-condensing air ducts. This layout also has zones that have potential for entrapment of non-condensable gases.
Patent No. US2001/0027703A1 shows a condenser on the church window principle. The condenser comprises at least one bundle with a multiplicity of tubes arranged parallel to one another, the bundle being subdivided into an upper section and a lower sector. The tubes have a first fluid flowing through them and the vaporous fluid flowing around them. A condensate discharge element is arranged in the bundle between the upper

sector and the lower sector preventing extent blockage of steam paths. This layout is mainly useful for modular approach and cannot be used for arriving at a compact design. This layout also results in comparatively higher pressure drop across the tube bundle.
US 5960867 describes a tube nest in which plurality of flow passages extend from outer circumference towards the extraction opening. Venting of non-condensable gases is not proper in this layout with regard absence of vent lane.
None of the identified prior patents shows, suggest or motivates to provide a tube nest layout for compact single pass condenser configured with optimized steam lanes and vent lanes with thickness of tube bundles achieving improved availability of steam around the tube nest, including positive venting of non-condensable gases, as well as substantially equalized pressure drop in the flow streams through different bundles.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose a method of generating an optimized tube nest layout for compact single pass condenser which minimizes overall steam pressure drop.
Another object of the invention is to propose a method of generating an optimized tube nest layout for compact single pass condenser which achieves uniform distribution and equalized pressure drop of steam across different tube bundles from all directions around the tube nest.

Another object of the invention is to propose a method of generating an optimized tube nest layout for compact single pass condenser, in which the bundle widths in terms of number of tube rows crossed by steam is constructed in both vertical and horizontal arrangement to achieve a low bundle pressure drop.
A still another object of the invention is to propose a method of generating a tube nest layout for compact single pass condenser in which well-spaced converging steam lanes are provided to achieve saving in steam lane pressure drop.
Yet another object of the invention is to propose a method of generating a tube nest layout for compact single pass condenser which allows configuration fo the vent lanes for effective evacuation of non-condensable gases with the steam lanes for better availability of steam around the tube nest interalia to prevent air pocket formation by making all the tubes operative for condensation process.
A further object of the invention is to propose a method of forming a tube nest layout for compact single pass condenser which enables higher deaeration of condensate, by construction of a part of the tube bundles in horizontal manner with the condensate flowing opposite to steam flow into the bundle.
A still further object of the invention is to propose a method of generating a tube nest layout for compact single pass condenser, which ensures effective utilization of tube sheet area and thus making the condenser height as low as possible.

SUMMARY OF THE INVENTION
With the foregoing objects in view the present invention provides a compact condenser tube nest layout for compact single pass condenser, comprising a steam inlet through which steam is received, a plurality of cooling tubes for condensing steam received through the steam inlet, a condensate outlet through which condensate produced by the cooling tubes is discharged and at least one extracting means through which non-condensable gases are extracted.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which :
Figure 1 shows schematic diagram indicating configuration of cooling tubes on tube plate in accordance with the present invention.
Figure 2 shows the steam flow path in accordance with the present invention.
Figure 3 shows flow of steam with higher concentration of non-condensable gases in accordance with the present invention.
Figure 4 shows the tube bundles in a nest with combination of vertical and horizontal configuration in accordance with the present invention.

Figure 5 shows the double section condenser with two identical tube nests on either side of central line in accordance with the present invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION.
Referring to Figure 1 in detail, a plurality of cooling tubes (1) is arranged on tube plate (2). Some of the bundles (12, 12a) are arranged in array in vertical fashion. At least one bundle (13a) is arranged in horizontal fashion at the bottom. Another bundle (7) is arranged as shown in Figure 1 before the gas extraction passage (11). At least two vertical steam lanes (3a) in upper part in the middle of vertical sections are formed by not providing tubes in that zone for steam entry to the vertical bundles (12a). Steam lanes (3) are formed as shown in Figure 1 by not providing cooling tubes in that zones to supply the required steam to the horizontal bundles (13). The shape of steam lanes (3) is such that uniform velocity is maintained. The width of the steam lanes (3) is selected based on the steam quantity to be received into the bundles (12, 12a, 13, 13a) to maintain comparable velocities in the steam lanes (3). The bundle width and shape in both vertical bundles (12, 12a) and horizontal bundles (13, 13a) are worked out based on the equalization of pressure drop in an optimum manner. Lane (5) represents a central lane in case of double section condensers as shown in Figure 5 and can be treated as side gap in case of single section condensers. Steam enters through the lane (5) and side gaps (14) for catering to the vertical bundles (12) and horizontal bundles (13 and 13a). A plurality of vent lanes (4, 4a) is provided to guide the steam

with high concentration of non-condensable gases to air cooling zone (7). A plurality of baffle plates (6, 6a) are provided to prevent direct bypassing of steam into the air cooling zone (7) and guide the steam with high gas concentration towards the gas evacuation pipe located in the passage (11) for gas evacuation by the evacuation device not shown in the figure. A vessel (10) surrounds the tube nest which has steam inlet (9) at the entry and condensate outlet at the hot well (8). A plurality of tubes arranged in tube bundles (13, 13a) of the said tube nest is configured in horizontal segments has condensate falling down and steam flow path towards thus promoting counter flow of the streams. This feature helps in condensate heating and consequent liberation of non-condensable from the condensate. Steam flowing through central lane (5) impinges directly on the hotwell surface. Live steam impingement on the hotwell surface promotes deaeration. The vent lanes (4, 4a) as described above contribute for deaeration by isolating non-condensate gas and preventing its remixing with the condensate.
Figure 2 shows the stream lines of steam flow. The tube nest design provides uniform and even stream distribution to all the sections of the bundles (12, 12a, 13, 13a). The number of tubes crossed is based on the steam to be condensed in that section satisfying the pressure loss balance among the other sections of the bundles in optimum manner. Steam lanes (3, 3a) are formed in such a way that the steam quantity drawn is in proportion to the total number of tubes in the respective bundles (12, 12a, 13, 13a) located at different zones. The shape of steam lane (3, 3a) is converging in nature with reduced cross sectional area downstream to maintain approximately constant steam velocity through the steam lane. Steam lanes (3a) in the vertical bundles (12) are provided for better accessibility of steam to the tubes in this region. Tube bundles are designed and arranged as mirror images on either side of vertical section A-A through the center line of gas evacuation pipe Bottom bundle (13a)

is fully covered on both sides of section A-A so as to prevent direct entry of live steam to the air cooling one (7). Tube bundle (7) is provided before the gas evacuation passage (11) and named as air cooling zone for residual condensation and cooling of steam air mixture for reducing its volume at the entry to gas evacuation pipe (11).
Figure 3 shows vent lanes (4, 4a which are the evacuation lanes for non-condensable gas arranged with increased cross sectional area down-stream. All the vent lanes are designed in such a way that the steam with high non-condensable gas concentration is directed without any obstruction towards the air cooling zone (7). The converging shape of tube bundle (7) is for enhanced heat transfer and aids improved cooling of the mixture of steam and non-condensable gas. Proper cooling of the steam and non-condensable gas mixture reduces the volumetric flow rate to the gas evacuation device and ensures effective suction by the evacuation device connected through suction pipe located in the passage (11).
Figure 4 shows tube bundles in different configurations arranged as per present invention. One tube nest as described above can be used in single section condenser or two such tube nests as mirror image to each other as shown in Figure 5 can be used in double section condenser. The condensate is collected in to the hot well (8).
Although the present discussion relates to a compact tube nest layout for single pass steam condenser, it will be appreciated that the methods discussed may be readily adapted for use with other similar procedures. Not only the present invention proposes a method of generating a tube nest layout for compact single pass condenser to

achieve uniform steam distribution and equalized pressure drop across different tube bundles from all directions around the tube nest so as to minimize overall steam pressure drop but also ensures effective utilization of tube sheet area and this making the condenser height as low as possible.
It will be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its scope.
Furthermore, all examples recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor(s to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.

WE CLAIM :
1. A method of forming a compact tube nest layout for single pass condenser
to achieving minimize overall steam pressure drop through uniform steam flow distribution and equalized pressure drop across different tube bundles from all directions around the tube nest, wherein said single pass condenser have a steam inlet (9) through which steam is received; a gas extraction pipe (11); a condensate outlet (8) through which condensate condensed on the cooling tubes is discharged, and a vessel (10), and wherein said method comprising of :
- constructing the tube nest with at least four to six types of tube bundles (12, 12a, 13, 13a, 7) with a plurality of cooling tubes constituting a first type of tube bundles (12, 12a, 13, 13a) to act as condensing zone and a second type of tube bundle (7) acting as an air cooling zone; and
- arranging two tube nests as mirror image to each other in a double section condenser, characterized in that the steam received from a steam inlet (9) is allowed to pass into the first type of tube bundles through a central lane (5), and a plurality of formed steam lanes (3, 3a) having two side gaps (14), a top gap (15), and a bottom gap (16), and in that the air cooling zone (7) comprising at least of 5-10% total number of said plurality of cooling tubes surrounded by at least two baffle plate (6, 6a) to prevent direct entry of the steam into the air cooling zone (7).

2. The method as claimed in claim 1, wherein the steam lanes (3, 3a, 5) and the side gaps (14) constitute converging passages for steam so as to maintain a fairly constant steam velocity for achieving a low steam lane pressure drop, and wherein the passages are formed such that steam availability around the tube nest is higher.
3. The method as claimed in claim 1, wherein the portion of steam with high concentration of non-condensable gases is allowed to pass through a plurality of diverging passages (4, 4a) created in the tube nests at different zones of the condenser before entering the air cooling zone (7), and wherein the air cooling zone is formed by a converging tube bundle (7) in steam flow direction so as to achieve an effective cooling of the non-condensable gases.
4. The method as claimed in claim 1m wherein steam bypassing to the air cooling one (7) is prevented by said baffle plates (6, 6a) at specific location.

5. The method as claimed in claim 1, wherein the thickness of tube bundles
(12, 12a, 13, 13a) in terms of number of tube rows in the direction of steam flow is such that the overall pressure drops in their respective paths are substantially equal to minimize the overall average pressure drop of steam in the condenser.