Patent Application
20100282451
The present invention relates generally to a heat exchanger apparatus and/or component therefor, and specifically to a heat exchanger apparatus and/or component therefor that results in a reduced pressure drop of the shell-side fluid while providing tube bundle stabilization.
Generally, a tubular heat exchanger consists of a shell or large vessel with a bundle of tubes inside of the shell. Two fluids of different starting temperatures flow through the heat exchanger. The fluid with the higher starting temperature is known as the primary fluid and the fluid with the lower starting temperature is known as the secondary fluid. One fluid, known as the tube-side fluid, flows inside of the tubes while a second fluid, known as the shell-side fluid, flows outside of the tubes through the shell. The fluids may both be liquids or they may both be gases or one may be a gas while the other is a liquid. Furthermore, either of the primary fluid or the secondary fluid may be the tube-side fluid or the shell-side fluid. During operation of the heat exchanger, heat is transferred between the two fluids without direct contact between the two fluids. Specifically, heat is transferred from the primary fluid, through the walls of the tubes, and into the secondary fluid. The transfer of heat without contact between the shell-side fluid and the tube-side fluid is particularly desirable in the nuclear power plant industry because the primary or secondary fluids may become radioactive. Depending upon the fluids used and the desired results, heat is transferred either from the tube-side fluid to the shell-side fluid or vice versa.
A typical solar power plant uses a preheater, a steam generator and a superheater to produce steam for introduction into a turbine where that steam is converted into useful work. In such a system, hot oil is typically used as the primary fluid and pre-heated water is typically used as the secondary fluid. The preheater heats up the secondary fluid and sends it to the steam generator where it is converted into vapor and sent to the superheater. The superheater then transfers thermal energy from the primary fluid to the vapor, thereby converting the vapor from a wet vapor into a dry vapor that is useful for power generation. The tube bundle is maintained submerged in the shell-side fluid, which may be the vapor produced in the steam generator or the primary fluid. As the wet vapor is converted into dry vapor and exits the superheater, it is replenished by introducing additional wet vapor into the shell.
A superheater may be designed with the primary fluid on the shell-side or on the tube side. Each configuration presents a unique set of challenges. When the primary fluid is on the tube-side and the vapor to be superheated is on the shell-side, the vapor entering the superheater may carry water droplets which, if traveling at a high velocity, may damage the tubes upon impact. Further, because the vapor entering the superheater is at a high pressure, possibly over 2,000 psi, making the diameter of the vessel large enough to reduce the vapor velocity will make the equipment exceptionally expensive. Therefore, it is an object of the invention to create a heat exchanger apparatus for use as a superheater with a primary fluid on the tube-side and the vapor to be superheated on the shell-side wherein the vapor will not damage the tubes upon impact due to the high pressure of the steam.
Alternatively, when the primary fluid is on the shell-side and the vapor to be superheated is on the tube-side, in order to maintain a very small pressure loss in the vapor flow and the primary fluid stream, conventional superheaters have been designed as bulky, large diameter pieces of equipment. Superheaters have also been designed with an increased baffle spacing and a decreased tube pitch dimension. However, these designs increase the likelihood of flow induced tube vibration. Therefore, it is an object of the invention to create a heat exchanger apparatus for use as a superheater with a primary fluid on the shell-side and the vapor to be superheated on the tube-side that has the smallest possible pressure loss in the vapor flow and heating fluid streams while reducing the effects of shell-side fluid induced vibration on the tube bundle.
Furthermore, preheaters in solar power plants contain a primary fluid with a flow rate that is significantly higher than the flow rate of the fluid to be heated. The higher primary fluid flow rate results in higher shell-side cross flow velocities and an undesirable higher pressure drop. It is therefore an object of the present invention to create a preheater with an efficient heat transfer rate that does not have an undesirable loss of pressure.
It is a further object of the invention to create a single heat exchanger apparatus that can accomplish all of the objectives noted above regardless of whether the primary fluid is on the shell-side or the tube-side.
These objects and others, which will become apparent from the following disclosure and drawings, are achieved by the present invention which comprises in one aspect, a heat exchanger comprising: a shell forming a cavity, the shell comprising an inlet for introducing a shell-side fluid into the cavity and an outlet for allowing the shell-side fluid to exit the cavity; a tube bundle for carrying a tube-side fluid, the tube bundle located in the cavity along a longitudinal axis; at least one stabilizing plate positioned within the cavity and arranged in a substantially transverse orientation, the stabilizing plate comprising a lattice structure having openings, wherein tubes of the tube bundle extend through the openings; and wherein the openings of the lattice structure are sized and shaped so that the tubes contact the lattice structure and a portion of the openings remain unobstructed by the tubes, thereby allowing axial flow of the shell-side fluid through the stabilizing plate.
In another aspect, the invention can be a heat exchanger comprising: a shell having a cavity, the shell comprising an inlet for introducing a shell-side fluid into the cavity and an outlet for allowing the shell-side fluid to exit the cavity; a tube bundle for carrying a tube-side fluid, the tube bundle positioned in the cavity along a longitudinal axis; a plurality of lattice structures located in the cavity for transversely stabilizing the tube bundle, wherein tubes of the tube bundle extend through openings of the lattice structure, a portion of the openings remaining unobstructed by the tubes so as to allow substantially unrestricted axial flow of the shell-side fluid through the lattice structure; a plurality of baffles positioned within the cavity, the baffles producing cross-flow of the shell-side fluid within the cavity; and wherein the lattice structures and the baffles are arranged in alternating manner along the longitudinal axis.
In a further aspect, the invention can be an apparatus for stabilizing a tube bundle within a heat exchanger comprising: a peripheral frame having an inner surface that defines a central opening; and a plurality of members, each of the members having a first end connected to the peripheral frame and a second end connected to the peripheral frame, the members arranged in an intersecting manner so as to form a lattice structure that fills the central opening, the lattice structure comprising openings for receiving tubes of a tube bundle.
In a still further aspect, the invention can be a tube bundle assembly comprising: a plurality of tubes forming a tube bundle that extends along a longitudinal axis, the tubes having an outer surface having a circular transverse cross-section; a stabilizing structure oriented substantially transverse to the longitudinal axis, the stabilizing structure comprising: a peripheral frame having an inner surface that defines a central opening; and a plurality of linear members, each of the linear members having a first end connected to the peripheral frame and a second end connected to the peripheral frame, the linear members arranged in an intersecting manner so as to form a lattice structure that fills the central opening, the lattice structure comprising quadrilateral openings; the tubes of the tube bundle extending through the quadrilateral openings so that the circular outer surface of the tubes are in tangential contact with the linear members.
a is a front view of a double segmental baffle according to an embodiment of the present invention.
b is a front view of a disc-and-donut baffle according to an embodiment of the present invention.
Referring to
The solar power plant 200 generally comprises a preheater 10, a steam generator 20, a superheater 30, a high pressure (HP) turbine 40, a reheater 50, a low pressure (LP) turbine 45, an air cooled condenser 60, a condensate pump 65, a low pressure feedwater heater 70, a deaerator 80, a boiler feed pump 85 and a high pressure feedwater heater 90. All of the aforementioned components of the solar power plant 200 are arranged and operably coupled to one another as is known in the art.
In the solar power plant 200, the preheater 10 is used to preheat a secondary fluid, which is water in the exemplified embodiment. Once preheated in the preheater 10, the preheated water flows into the steam generator 20 where it is converted (i.e., boiled) into vapor (i.e., steam). However, it is possible to omit the pre-heater 10 if desired. Although the solar power plant 200 will be discussed as using water as the secondary fluid, the invention is not so limited and other fluids may be used in place of water. Furthermore, as used herein, the term fluid is intended to include liquid, gas, vapor, plasma or any combination thereof that may be used in a heat exchanger device.
The preheater 10 is a high pressure container or shell that preheats the water so that the water does not need to be heated in one step from an ambient temperature to a final temperature within the steam generator 20. Using the preheater 10 is preferred because it increases efficiency and minimizes thermal shock stress to components, as compared to injecting ambient temperature liquid into a steam generator or other device that operates at extreme temperatures.
The preheated water, often referred to as the feedwater, is introduced into the steam generator 20 where the preheated water is converted to steam. As water in the steam generator 20 continually turns to steam and vacates the steam generator 20, additional preheated water from the preheater 10 is continuously introduced into the steam generator 20 to replenish the recently vacated water. The steam generator 20 uses heat from the tube-side fluid, which is preferably hot oil or some other primary fluid that is heated through the use of solar panels, to convert the preheated water to steam through a thermal energy transfer process. Of course, the primary fluid may be the shell-side fluid and the preheated water may be the tube-side fluid if desired.
The tube bundle of the steam generator 20 is preferably a two pass U-tube design. The invention, however, is not so limited. For example, the steam generator 20 may be a single pass heat exchanger or a U-tube heat exchanger with four, six, eight or more passes. The steam generator 20 in the solar power plant 200 serves to produce high pressure steam in a classical kettle type heat exchanger by circulating hot oil through the tubes of the tube bundle. The hot oil is the primary fluid (i.e., the tube-side fluid) and it is typified by a high boiling point and an even higher flashpoint so that the energy captured by the solar collectors can be transferred to it, raising its temperature to between 700° F. and 800° F. without any risk. The hot oil primary fluid causes the water or other secondary fluid (i.e., shell-side fluid in the steam generator) to heat up, evaporate and convert to pressurized vapor or steam.
The steam produced within the cavity of the shell that exits the steam generator 20 is introduced into the superheater 30 where the saturated or wet steam is converted into a dry steam that can be used for power generation. The superheater 30 is also preferably a two pass U-tube heat exchanger but can be any of the types mentioned above. In a preferred embodiment, the solar heated primary fluid flows through the tube-side and the wet steam flows through the shell-side of the superheater 30. Of course, the invention is not so limited.
Upon exiting the superheater 30, the superheated dry steam enters the HP steam turbine 40 where the thermal energy from the pressurized steam is converted into rotary motion. Next, the partially spent steam that emerges from the HP turbine 40 is reheated by the primary fluid in the reheater 50, which is another heat exchanger apparatus. The steam emerging from the HP turbine 40 has a small fraction of moisture content. Utilizing the heat from the primary fluid, the wet steam is superheated in the reheater 50 prior to being introduced into the LP turbine 45 in order to remove as much of the moisture as possible. Reheating the steam in the reheater 50 enhances the thermal efficiency of the power plant.
Once reheated, the steam is introduced into the LP turbine 45. The HP and LP turbines 40, 45 are coupled with electric generators in order to produce electricity. Specifically, the pressurized steam that is fed through the HP and LP turbines 40, 45 is used to drive an electrical generator which is connected to the electric grid for distribution. The spent steam emerging from the LP turbine 45 is transported to the water or air cooled condenser 60 where it is converted into condensate. The condenser 60 converts the steam back to a liquid so that it can be pumped back to the steam generator 20. However, prior to re-entering the steam generator 20, a few more steps must be completed.
Specifically, the condensate is pumped from the condenser 60 by a condensate pump 65 to one or more low pressure feedwater heaters 70 for preheating. The heated condensate is then deaerated in a deaerator 80 and pumped into the high pressure feedwater heater 90 using boiler feed pumps 85. The preheated and pressurized condensate is then pumped back into the preheater 10 where the process starts over.
The invention discussed herein will be described with reference to a preheater and a superheater. However, the invention is not so limited and the particular components that are described may be used with any heat exchanger apparatus. The discussion that follows is limited to a preheater and a superheater for clarity and discussion purposes only. Furthermore, different aspects of the description with reference to the preheater may be used with the superheater and vice versa. A person skilled in the art would understand how to combine various aspects of the present invention described below in order to create a heat exchanger apparatus to achieve a particular result.
Referring to
The superheater 30 is preferably a kettle-type heat exchanger. In the exemplified embodiment, the superheater 30 is an elongated, tubular type heat exchanger that extends along a longitudinal axis A-A from a proximal end 301 to a distal end 302. The superheater 30 comprises a plurality of vents 374 and a plurality of drains 376 for emptying a shell-side fluid from a shell 310 and/or for maintaining a desired shell-side liquid level within the shell 310. The superheater 30 comprises fixed supports 306 for maintaining the superheater 30 in a horizontal orientation. Of course, the invention is not limited to a horizontal superheater and the superheater may be vertically or otherwise oriented as would be known to persons skilled in the art.
Preferably, all components of the superheater 30, including the shell 310, the tube bundle 330 and all other major components, are constructed of metal, such as steel, aluminum, iron or the like. Of course, other metals and materials can be used for the various components as long as the proper thermal transfer can be effectuated between the shell-side fluid and the tube-side fluid. It is preferable that the materials used for the various components are capable of withstanding corrosion or damage when submerged in or otherwise subjected to temperatures in excess of 800° F.
The superheater 30 generally comprises a shell 310 having an inner surface 314 that forms an internal cavity 313 with a tube bundle 330 positioned therein. The superheater 30 also comprises a tube sheet 315 disposed in the cavity 313 in a substantially transverse orientation that separates the internal cavity 313 into a tube-side chamber 316 and a shell-side chamber 317. The tube-side chamber 316 extends longitudinally from the tube sheet 315 to the proximal end 301 of the shell 310 while the shell-side chamber 317 extends longitudinally from the tube sheet 315 to the distal end 302 of the shell 310.
The superheater 30 comprises a plurality of inlets and outlets 320-323 that form passageways through the shell 310 so that fluids can pass into or out of different constituent components and/or internal chambers of the shell 310. Specifically, the superheater 30 includes a tube-side fluid inlet 320, a tube-side fluid outlet 321, a shell-side fluid inlet 322 and a shell-side fluid outlet 323. In a preferred embodiment, the tube-side fluid is steam or vapor from the steam generator 20 and the shell-side fluid is hot oil that is heated via solar power to temperatures between 700-800° F. or higher. However, the invention is not so limited and the tube-side fluid may be hot oil and the shell-side fluid may be water. Alternatively, fluids other than steam or vapor and hot oil may be used.
In a preferred embodiment, the tube-side fluid inlet 320 is located on a bottom portion 318 of the shell 310 while the tube-side fluid outlet 321 is located on a top portion 319 of the shell 310. The tube-side fluid inlet 320 and the tube-side fluid outlet 321 are preferably positioned so as to introduce fluid into and allow fluid to exit the tube-side chamber 316 of the shell 310, respectively because the preferred embodiment utilizes a tube bundle with a U-tube design. However, the invention is not so limited and the tube-side fluid inlet 320 and the tube-side fluid outlet 321 could be positioned on opposite ends of the shell 310 in embodiments where, for example, the tube bundle 330 has a straight (i.e., single-pass) tube design.
The shell-side fluid inlet 322 is located on a top portion 324 of the shell 310 at or near the distal end 102 of the shell 110 and the shell-side fluid outlet 323 is located on a bottom portion 325 of the shell 310 at or near the tube sheet 315. The term “near” is intended to indicate that the shell-side fluid inlet 322 and the shell-side fluid outlet 323 need not be positioned exactly at the distal end 302 of the shell 310 and the tube sheet 315, respectively. Rather, the tube-side fluid inlet 322 is positioned between a middle point MP of the shell 310 and the distal end 302 of the shell 310 and the tube-side fluid outlet 323 is positioned between the middle point MP of the shell 310 and the tube sheet 315. Furthermore, the invention is not limited to having the shell-side fluid inlet 322 on the top portion 324 of the shell 310 and the shell-side fluid outlet 323 on the bottom portion 325 of the shell 310. Other configurations are contemplated within the scope of the present invention.
Referring now solely to
The U-tubes 331 have a general U-shape having a bight portion 332 that is generally located adjacent the distal end 302 of the shell 310 and two straight legs 308, 309 that are operably coupled to (or extend through) openings 333 in the tube sheet 315 so as to form passageways into the tube-side chamber 316. The tube-side chamber 316 is separated into a top chamber 303 and a bottom chamber 304 by a partition plate 307. The partition plate 307 is a wall that extends along the longitudinal axis A-A from the tube sheet 315 to the proximal end 301 of the shell 310 and creates two distinct, hermetically isolated chambers 303, 304. The partition plate 307 separates the tube-side chamber 316 so that the tube-side fluid can be introduced into the bottom chamber 304 via the tube-side fluid inlet 320 and flow into the bottom legs 309 of the U-tubes 331. The tube-side fluid will continue to flow through the bight portions 332 of the U-tubes 331 and into the top legs 308, where it will exit the U-tubes 331 into the top chamber 303. Once in the top chamber 303, the tube-side fluid will be forced out of the shell 310 via the tube-side fluid outlet 321. Of course, the invention is not so limited and the tube-side fluid may be introduced into the superheater 30 through the top chamber 303 and may exit the superheater 30 through the bottom chamber 304.
While not necessary, the proximal end 301 of the shell 31.0 also comprises an access door 339 for accessing the internal cavity 313 of the shell 310 so that the tube bundle 330 and other components can be removed, cleaned and/or worked on for maintenance and up-keep. Removably attached to the access door 339 is an end cap 338 that creates a solid, hermetically sealed proximal end 301 of the superheater 30.
The superheater 30 also comprises a plurality of stabilizing plates 140 for supporting the U-tubes 331. The stabilizing plates 140 are positioned within the shell-side chamber 317 and arranged in a substantially transverse orientation. The stabilizing plates 140 comprise a lattice structure 165 having openings 141 that receive the legs 108, 109 of the U-tubes 331, thereby stabilizing the U-tubes 331 of the tube bundle 330 and permitting axial flow of the shell-side fluid along the U-tubes 331. The stabilizing plates 140 are preferably disk-shaped structures with an outer peripheral frame 142 wherein the lattice structures 165 are formed by intersecting members in the form of thin, flat linear strips. These strips form a grid having rhombus shaped openings 141 (
The outer peripheral frames 142 of the stabilizing plates 140 preferably conform to the shape of the inner surface 314 of the shell 310. The peripheral frames 142 also enclose the lattice structure 165. The peripheral frames 142 of the stabilizing plates 140 are preferably welded, bolted, or otherwise attached to a structure within the superheater 30 to provide stability and rigidity to the tube bundle 330. The specific details of the rhombus shaped openings 141, as well as the specific manner by which the U-tubes 331 are secured within the rhombus shaped openings 141 of the lattice structure 165, will be described below in greater detail with reference to
Referring still to
The baffles 400 are used to hold the U-tubes 331 in position, prevent the effects of vibration on the U-tubes 331, and direct the shell-side fluid flow along the tube bundle 330 within the shell-side chamber 317. Directing the shell-side fluid flow increases the fluid velocity and the effective heat transfer coefficient of the superheater 30, thereby making the superheater 30 more efficient. However, as noted above, using the baffles 400 to create a shell-side fluid flow redirection or cross-flow also results in an often undesirable pressure loss.
Referring to
Referring now to
Referring now to
The baffles 400, including the double segmental baffles 401 and the disc-and-donut baffles 430, also comprise openings for supporting the U-tubes 331 therein. The openings of the baffles 400 are sized to tightly retain the U-tubes 331 to prevent sagging of the U-tubes 331 and to prevent the U-tubes 331 from suffering damage due to vibration. The baffles 400 do not allow axial flow of the shell-side fluid therethrough but rather induce cross-flow around the structures.
Referring now solely to
The rectangular plate 420 is positioned in the cavity 313 so that the convex sides 422 will be in surface contact and welded, bolted or otherwise connected to the inner surface 314 or some other component of the shell 310. Specifically, the convex sides 422 of the rectangular plate 420 will be coupled to opposite lateral sides of the inner surface 314 of the shell 310. If the semi-circular plates 405 are coupled to the top and bottom portions 334, 335 of the inner surface 314 of the shell 310, then the rectangular plate 420 is coupled to left and right portions of the inner surface 314 of the shell 310 (as best seen in
The disc-and-donut baffles 430 may be used instead of the double segmental baffles 401. In such a configuration, the donut plate 432 and the disc plate 431 will be arranged within the cavity 313 in an alternating manner along the longitudinal axis A-A to produce the cross-flow of the shell-side fluid. With such an arrangement, the shell-side fluid will flow through the opening 433 in the donut plate 432 and around an outer periphery 435 of the disc plate 431.
It should be noted that relative terms such as axially, longitudinally, cross-flow, back-and-forth, left, right, up and down are merely used to delineate relative positions of the internal components of the superheater 30 with respect to one another and with respect to the longitudinal axis A-A and are not intended to be in any further way limiting of the present invention. Thus, although the discussion above indicates that the semi-circular plates 405 are positioned at the top and bottom portions 334, 335 of the inner surface 314 of the shell 310, they may be positioned in other locations as would be known to persons skilled in the art.
Still referring to
Referring to
Referring to
Referring to
The rhombus shaped openings 141 have two diagonals extending from opposite corners of the openings 141. Specifically, the rhombus shaped openings 141 have a major diagonal 143 that extends from a top corner 147 to a bottom corner 148 of the openings 141 and a minor diagonal 144 that extends between two side corners 149, 160 of the openings 141. As such, the major and minor diagonals are substantially perpendicular to one another. The major diagonal 143 is greater than the minor diagonal 144.
The U-tubes 331 extend through and fit within the rhombus shaped openings 141 such that portions of the U-tubes 131 contact portions of the parallel strips 145, 146. Specifically, linear portions of the parallel strips 145, 146 contact contoured outer surfaces 361 of the tubes 331 of the tube bundle 330. More specifically, because the U-tubes 331 have a circular transverse cross-section and the strips 145, 146 are linear, a substantial majority of the outer surface 361 of each U-tube 331 is not in contact with the parallel strips 145, 146. Rather, from a transverse cross-section perspective, there are four points of contact between the outer surface 361 of the U-tubes 331 and the parallel strips 145, 146. Of course, the term “points of contact” is not strictly limited to a single point, but rather to a line (or very small area) of the contoured outer surface 361 of the U-tubes 331 that tangentially contacts the parallel strips 145, 146. In other words, the outer surface 361 of the U-tube 331 within each opening 141 has a tangential point of contact with each of the four parallel strips 145, 146 that makes up the opening 141.
Furthermore, there are minor gaps 162 between the outer surface 361 of the U-tubes 331 and the parallel strips 145, 146 along the direction of the minor diagonal 144 and major gaps 163 between the outer surface 361 of the U-tubes 331 and the parallel strips 145, 146 along the direction of the major diagonal 143. These major and minor gaps 162, 163 remain unobstructed by the U-tubes 331 when the U-tubes 331 are positioned within the openings 141 of the lattice structure 165 in order to afford axial flow of the shell-side fluid through the openings 141 and, thus, through the stabilizing plate 140 with no substantial pressure drop and/or cross flow. The major gaps 163 have a larger area than the minor gaps 162.
The combined space within the openings 141 that the minor and major gaps 162, 163 take up is not minute and inconsequential. Rather, the minor and major gaps 162, 163 provide a sufficient amount of space to encourage the axial flow of the shell-side fluid through the openings 141. In a preferred embodiment, the major and minor gaps 162, 163 take up between 25-50% of the openings 141. In a more preferred embodiment, the major and minor gaps 162, 163 take up between 30-45% of the openings 141. In a most preferred embodiment, the major and minor gaps 162, 163 take up between 35-40% of the openings 141. Of course, the portion of the openings 141 that is not taken up by the major and minor gaps 162, 163 is instead obstructed by the U-tubes 331 such that in the most preferred embodiment, the U-tubes 331 take up between 60-65% of the openings 141.
This axial flow of the fluid further improves the boiling rate. Furthermore, the axial flow of the shell-side fluid prevents oxidation products and sludge from depositing in the crevices at the tube support locations, which has been known to cause the demise of numerous steam generators in nuclear plants in the past. Additionally, the openings 141 allowing for axial flow of the shell-side fluid does not introduce a pressure loss into the flow of the shell-side fluid because no cross-flow or flow redirection or obstruction is created.
Furthermore, as noted above, the configuration of the lattice structures 165 of the stabilizing plates 140 allow for the pitch between adjacent U-tubes 331 within the openings 141 to not be decreased. The openings 141 can be conceptualized as having vertical rows, horizontal rows and diagonal rows. The tube pitch in the vertical rows is larger than the tube pitch in the horizontal and diagonal rows. Specifically, in a preferable embodiment the tube pitch in the vertical row is approximately equal to, or slightly smaller than, twice the length of one side of the opening 141. In a more preferable embodiment, the tube pitch in the vertical row is between 1.9 to 2.0 times the length of one side of the opening 141. The tube pitch in the horizontal and diagonal rows is preferably the same, although the invention is not limited to such a configuration. Specifically, the tube pitch in the horizontal and diagonal rows is preferably between 1.0 to 1.5 times the length of one side of the opening 141 and more preferably between 1.1 to 1.2 times the length of one side of the opening 141.
The stabilizing plate 140 illustrated in
Many components of the preheater 10 are the same as the components of the superheater 30 that have been described above. Thus, only components of the preheater 10 that are substantially different from the components of the superheater 30 will be discussed in detail below. Furthermore, the superheater 30 was discussed above using reference numbering in the “300” series. The components of the preheater 10 that are the same or similar to components of the superheater 30 are provided with the same reference number, except that the “100” series will be used to describe the preheater 10 components.
Similar to the superheater 30, the preheater 10 is specially designed to minimize the pressure loss of the shell-side fluid while still maintaining a stable, vibration-free environment for a tube bundle 130 positioned within the preheater 10. At the same time, the preheater 10 reduces costs and enhances heat transfer rates.
Referring to
The preheater 10 comprises a longitudinal barrier 170 that separates the shell-side chamber 117 into an upper portion 127 and a lower portion 128. The longitudinal barrier 170 may be formed of a unitary piece of material that extends the longitudinal length of the cavity 113 or as several longitudinal sections that are welded or otherwise fastened together. Regardless of whether the longitudinal barrier 170 is formed of a unitary piece or attached sections, it is substantially impermeable to the flow of the shell-side fluid, thereby forcing the shell-side fluid to flow around the longitudinal barrier 170 during operation of the preheater 10. There is an opening 129 between the longitudinal barrier 170 and the tube sheet 115 and an opening 139 between the longitudinal barrier 170 and the distal end 102 of the shell 110, each of which creates a passageway for the shell-side fluid to flow between the upper and lower portions 127, 128 of the shell-side chamber.
Referring now solely to
As noted above, the stabilizing plate 140 used in the preheater 10 is preferably the embodiment comprising two distinct semicircular plates 171, 172 separated by a space 173. This is preferred so that the longitudinal barrier 170 can fit in the cavity 113 within the space 173 between the two semicircular plates 171, 172. The baffles 400 are also preferably configured with a space for the longitudinal barrier 170 to fit within. Preferably, the longitudinal barrier 170 fits tightly within the space 173 in order to minimize or eliminate a flow of the shell-side fluid through the space 173 and to force the shell-side fluid to flow through the openings 141 of the lattice structure 165 of the stabilizing plates 140.
The preheater 10 comprises a transverse barrier 135 positioned within the cavity 113. The transverse barrier 135 is a single, unitary plate that separates the shell-side chamber 117 into two equally sized longitudinal sections. However, the invention is not so limited and the transverse barrier 135 may comprise two separate plates, one positioned on either side of the longitudinal barrier 170. The transverse barrier 135 extends into the upper portion 127 of the shell-side chamber 117 from the longitudinal barrier 170 to the shell-side fluid inlet 122 and into the lower portion 128 of the shell-side chamber 117 from the longitudinal barrier 170 to the shell-side fluid outlet 123. Furthermore, the transverse barrier 135 separates the shell-side fluid being introduced into the upper portion 127 into two shell-side fluid streams 132, 133 flowing in opposite divergent longitudinal directions within the upper portion 127. A bottom portion 134 of the transverse barrier 135 in the lower portion 128 directs the two shell-side fluid streams 132, 133 in the lower portion 128 into the shell-side fluid outlet 123.
Referring to
The baffles 400 create a cross-flow of the shell-side fluid within the cavity 113. Specifically, if double segmental baffles 401 are positioned within the cavity 113, the first and second streams 132, 133 must flow around the two straight sides 421 of the outer surface of the rectangular plate 420 and in the space 406 between the two semicircular plates 405. Of course, it should be understood that the disc-and-donut baffles 430 could replace the double segmental baffles 401 and have the same effect. Furthermore, any other type of baffle arrangement may be used within the scope of the invention including, without limitation, single segmental baffles or triple segmental baffles.
The cross-flow of the shell-side fluid created by the baffles 400 enhances the efficiency of the preheater 10, but creates a pressure drop in the shell-side fluid. In order to sufficiently restrain the tubes within the baffles as will be described below, a large number of the baffles 400 must be positioned in the cavity 113. However, this is undesirable because including more baffles 400 creates a greater cross-flow of the shell-side fluid and results in a greater pressure drop of the shell-side fluid. Furthermore, providing less baffles 400 within the cavity 113 enables the U-tubes 131 to sag and makes the U-tubes 131 more susceptible to damage resulting from shell-side fluid induced tube vibration. Therefore, it has been found to be advantageous to position the baffles 400 with greater spacing in between them to reduce the cross-flow and hence, the pressure drop and to further position the stabilizing plates 140 within the cavity 113 to restrain movement of the tubes while allowing for axial flow of the shell-side fluid through the plates 140, as was described above with reference to
Referring to
Referring to
Referring to
While the invention has been described with respect to specific examples including presently preferred modes of carrying out the invention, those skilled in the art will appreciate that there are numerous variations and permutations of the above described systems and techniques. It is to be understood that other embodiments may be utilized and structural and functional modifications may be made without departing from the scope of the present invention. Thus, the spirit and scope of the invention should be construed broadly as set forth in the appended claims.
The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/175,963, filed on May 6, 2009, and U.S. Provisional Patent Application Ser. No. 61/175,967, filed on May 6, 2009, the entireties of which are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61175963 | May 2009 | US | |
| 61175967 | May 2009 | US |
