Offshore water intake and discharge structures making use of a porous pipe

Abstract

A porous pipe for use in offshore water intake and discharge systems is provided, which is able to strain and filter water directly within the water body along the length of the pipe. Features of the porous pipe can be designed to optimize performance and flow rates for the particular environment, including the pore distribution and diameter along the pipe, the wall thickness and materials along the pipe; and the placement of piezoelectric devices to vibrate the pipe wall to remove impinged debris from pores.

Claims

1. A pipe comprising: a plurality of pores arranged along a length of the pipe disposed in a body of a liquid; and a pipe discharge end configured to be connected to a negative pressure source; wherein the negative pressure source is configured to cause the liquid to be drawn into the plurality of pores arranged along the length of the pipe and delivered to the negative pressure source; and wherein the plurality of pores are configured to filter particulates from entering along the length of the pipe.

2. The pipe according to claim 1, wherein the plurality of pores arranged along the length of the pipe comprise one or more pores of a first diameter and one or more pores of at least a second diameter.

3. The pipe according to claim 1, wherein the plurality of pores comprises spacing between each pore, and wherein the size of the spacing changes in different sections of the pipe.

4. The pipe according to claim 1, wherein the pipe comprises a pipe wall having the plurality of pores formed therethrough, and wherein the thickness of the pipe wall changes in different sections of the pipe.

5. The pipe according to claim 4, wherein the diameter of the pipe wall changes in different sections of the pipe.

6. The pipe according to claim 4, further comprising an inner pipe wall comprising a further plurality of pores arranged along the inner pipe wall, wherein the inner pipe wall is suspended from inside the pipe wall.

7. (canceled)

8. The pipe according to claim 4, further comprising at least one piezoelectric vibrational device affixed to the pipe wall and connected to an electrical cable, wherein the at least one piezoelectric vibrational device comprises an actuator connected to the pipe wall on a first end and connected to a counterweight on a second end; and wherein an alternating voltage is supplied to the actuator by the electrical cable causing the pipe wall to vibrate and dislodge debris in the plurality of pores.

9. A pipe comprising: a plurality of pores arranged along a length of the pipe disposed in a body of a first liquid; and a pipe intake end configured to be connected to a positive pressure source providing a second liquid; wherein the positive pressure source is configured to cause the second liquid to be drawn into the pipe and discharged through the plurality of pores arranged along the length of the pipe; and wherein the plurality of pores are configured to filter particulates from the second liquid from being discharged into the body of the first liquid along the length of the pipe.

10. The pipe according to claim 9, wherein the plurality of pores arranged along the length of the pipe comprise one or more pores of a first diameter and one or more pores of at least a second diameter.

11. The pipe according to claim 9, wherein the plurality of pores comprises spacing between each pore, and wherein the size of the spacing changes in different sections of the pipe.

12. The pipe according to claim 9, wherein the pipe comprises a pipe wall having the plurality of pores formed therethrough, and wherein the thickness of the pipe wall changes in different sections of the pipe, and wherein the diameter of the pipe wall changes in different sections of the pipe.

13. (canceled)

14. The pipe according to claim 12, further comprising an inner pipe wall comprising a further plurality of pores arranged along the inner pipe wall, wherein the inner pipe wall is suspended from inside the pipe wall.

15. (canceled)

16. The pipe according to claim 12, further comprising at least one piezoelectric vibrational device affixed to the pipe wall and connected to an electrical cable, wherein the at least one piezoelectric vibrational device comprises an actuator connected to the pipe wall on a first end and connected to a counterweight on a second end; and wherein an alternating voltage is supplied to the actuator by the electrical cable causing the pipe wall to vibrate and dislodge debris in the plurality of pores.

17. A method for designing and manufacturing a porous pipe, comprising: dividing the porous pipe into a plurality of elements of a predefined length and diameter; assigning a material of known permeability to each of the plurality of elements for manufacture of each of the plurality of elements; determining, for a first element of the plurality of elements, a required flow rate for a first end of the first element; determining, based at least partly on the required flow rate for the first end of the first element and the known permeability of the material of the first element, a pore flow rate for a single idealized pore of the first element; determining, based on the required flow rate for the first end of the first element and the pore flow rate for the first element, an end flow rate for a second end of the first element; iterating the steps of determining the required flow rate, the pore flow rate and the end flow rate for each of the plurality of elements, wherein for each element after the first element, the required flow rate of the first end of each element is the end flow rate for the second end of the prior element; determining, based on the iterations for each of the plurality of the elements of the porous pipe, a total flow rate the porous pipe may tolerate in a fluid body; and manufacturing the porous pipe having the plurality of elements, each having their respective predefined lengths and diameters and materials.

18. The method according to claim 17, wherein the required flow rate for the first end of the first element corresponds to an intake flow rate of a fluid intake to which the porous pipe is to be connected, or a discharge flow rate of a fluid discharge to which the porous pipe is to be connected.

19. (canceled)

20. The method according to claim 17, wherein the pore flow rate for each element is determined by the equation Q.sub.pores=Permeability.sub.wall×(Po.sub.c−Po.sub.d)×(π×D.sub.sect)×L.sub.ab+t.sub.wall, wherein Q.sub.pores is the pore flow rate for the element; Permeability.sub.wall is the known permeability of the material of the element; Po.sub.c is the pipe static pressure; Po.sub.d is the fluid body static pressure; D.sub.sect is the predefined diameter of the element; L.sub.ab is the predefined length of the element; and t.sub.wall is the predefined wall thickness of the element.

21. The method according to claim 20, wherein the pipe static pressure (Po.sub.c) is determined by the equation Po.sub.c=H.sub.c×gρ, wherein H.sub.c is the fluid head at the idealized pore of the element; and ρ is the average density of fluid in the porous pipe.

22. The method according to claim 20, wherein the fluid body static pressure (Po.sub.d) is determined by the equation Po.sub.d=depth.sub.d×gρ, wherein depth.sub.d is the depth at a point of the fluid body adjacent to the idealized pore of the element.

23. The method according to claim 20, wherein the end flow rate for the second end of each element is determined by the equation Q.sub.a−Q.sub.pores=Q.sub.b, wherein Q.sub.a is the required flow rate for the first end of the element, and Q.sub.b is the end flow rate for the second end of the element.

24. The method according to claim 17, further comprising: prior to manufacturing the porous pipe, redefining one or more of the predefined length, diameter, wall thickness, pore distribution or pore diameter of one or more of the plurality of elements, or assigning a new material having a different permeability to one or more of the plurality of elements, to provide one or more of the plurality of elements with redefined parameters; and repeating the steps of determining a required flow rate for a first end of the first element, determining the pore flow rate for the single idealized pore of the first element, determining the end flow rate for the second end of the first element and iterating the steps of determining for each of the plurality of elements of the porous pipe based on the redefined parameters, and determining a new total flow rate the porous pipe may tolerate in the fluid body; wherein providing one or more of the plurality of elements with redefined parameters is repeated until a target total flow rate the porous pipe may tolerate in the fluid body is reached based on a particular set of redefined parameters for the plurality of elements; and wherein manufacturing the porous pipe further comprises manufacturing the porous pipe in accordance with the particular set of redefined parameters for the plurality of elements.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1A illustrates some typical arrangements of intake structures and methodologies currently employed according to the prior art;

[0027] FIG. 1B illustrates various embodiments of porous pipe configurations in accordance with the present application;

[0028] FIG. 2 illustrates a cross-sectional view of an installed porous pipe in accordance with an embodiment of the present application;

[0029] FIG. 3 illustrates further cross-sectional views of porous pipe in accordance with an embodiment of the present application;

[0030] FIG. 4 illustrates a cross-sectional view of an installed porous pipe in accordance with a further embodiment of the present application;

[0031] FIG. 5 illustrates a finite element of the porous pipe as used in the finite element analysis model; and

[0032] FIGS. 6A-6C illustrate various embodiments of porous pipe configurations in accordance with the present application comprising piezoelectric vibrational devices to perform a vibrational cleansing method of the pores.

DETAILED DESCRIPTION OF THE DRAWINGS

[0033] The present application will now be described with reference made to FIGS. 1B to 6C.

[0034] Porous pipe enables a cost effective structure to be employed that acts to strain filter water directly within the water body, efficiently removing organism entrapment, and significantly reducing entrainment and impingement. These functions can be performed by varying various features of the pipe wall, including: pore distribution can be controlled and varied along the pipe such that the average approach water velocity to the pipe surface (i.e., the actual water intake flow) is lower than the local particle settling velocity, and far lower than the local organism impingement velocity; pore diameter can also be controlled and varied along the pipe to limit the maximum particle diameter that may be entrained and locating the fine filtration within the water body removes organism entrapment; the wall thickness can be controlled and varied along the pipe to achieve the required pipe wall strength, and vary the pore length, thereby varying the flow resistance; and vibrating the pipe wall at frequencies optimized to remove impinged debris from pores.

[0035] In accordance with the present application, the porous pipe 101a, 101b, 101c may be manufactured to any length with an end jointed to conventional plant pipework 102a, 102b, 102c, as shown in FIG. 1B. In one example shown at the top of FIG. 1B, the porous pipe 101a wall may be manufactured at a thickness and strength suitable to be located any distance 103d from the water body bed 103 or any distance 104d from the surface 104. The porous pipe 101b, 101c may also be fully or partially contained in a further porous pipe, protective structure 105, trench 106 or other enclosure allowing communication between the porous pipe and the water body, as illustrated in the center and bottom of FIG. 1B. The installed porous pipe 101c may undergo variations in direction and depth 107 as required in the specific application and permitted by its manufacture.

[0036] FIGS. 2 and 3 illustrate cross-sectional views of a porous pipe 200. The walls 201 of the porous pipe 200 can be manufactured according to the processes and comprise the materials described in the aforementioned referenced U.S. patent application Ser. No. 15/552,868, thereby expressing a plurality of pores 205 throughout the entire wall 201 surface area of the pipe 205. The walls 201 are manufactured at a suitable thickness 201a, 201b, which may vary along the length 204 of the pipe 200, and local wall thickness variations may occur, for example at sectional joints. The porous pipe walls 201 form a circular or other shaped profile that may also change in diameter 202a, 202b along the length 204 of the porous pipe 200.

[0037] In further accordance with the present application, the diameter 202 of each pore 205, and the spacing 203 between pores 205 can be varied along the length 204 of the pipe 200 as required to create a given porosity. The pressure difference along a pore (i.e., across the pipe wall 201), the diameter 202 of the pore, and other structural compositions (e.g., pore pathway between weave layers) determine the water volume flow rate through a pore 205. Each pore 205 can be maintained at a suitable velocity and jet diameter 202 to reduce impingement and entrainment. The pressure gradient 206 along the pipe 200 may change commensurately, thereby varying the pressure difference 206 at each pore 205.

[0038] In a further embodiment shown in FIG. 4, the porous pipe 400 may additionally be configured with multiple walls 401, 402 having different diameters and different amounts of porosity, and with one or more of such walls 401, 402 configured incorporating structural elements. For such “pipe in pipe” configurations 400, the inner pipe 401 may be suspended 403 from or otherwise supported by the outer pipe 402, such that sonic or other type of cleaning of the inner and outer pipes 401, 402 may be readily undertaken.

[0039] Given required flow conditions, for example a process plant intake flow-rate, the present application allows the design of the porous pipe to be changed and variable to optimize performance of the porous pipe. A process plant typically requires a known and steady flow-rate, and is often able to adjust its intake and discharge pressures within a specified range to achieve this desired operating envelope.

[0040] The pipe can be designed by the user by dividing the pipe into sections of known properties (e.g. length, depth, etc.), and assigning a material of known permeability to each section. An effectively unlimited number of section and material combinations may be used. The permeability of a material of known construction is derived through a mixture of calculations and, to ensure accuracy, empirical testing. The depth at the start and end of each section can be used to determine the water body pressure of an undulating pipe.

[0041] Various manufacturing parameters of the porous pipe material that affect flow characteristics within a particular operating environment can be controlled. The value of these parameters (and thereby the permeability) can therefore change along the length of the pipe and include, but are not limited to, length, diameter, wall thickness, pore distribution, pore diameter, direction, etc. With knowledge of the particular configurations of these manufacturing parameters, and the resulting permeabilities, the expected flow characteristics of the porous pipe can be calculated.

[0042] The porous pipe is divided into discrete elements suitable for Finite Element Analysis (“FEA”). It is impractical to model every pore on the entire pipe, therefore each element models the element's plurality of pores as a single pore with a short length of non-porous pipe at either side. By reducing the total length of each element, and thereby increasing the number of elements, the accuracy of the calculation can be increased. The total volume flow-rate through the pores of each element is calculated using the idealized single pore and the number of pores dispersed along the circumference and length of the element (and, thereby, the entire porous pipe). Calculated volume flow-rates and the flow characteristics through each element are consequently based on this model. In the present application and shown for example in FIG. 5, elements are referred to as end “a” (the shorewards end), end “b” (the seawards end), point “c” (the modelled pore), and point “d” (the water body immediately next to point c). The pipe may have multiple sections, and each section may have multiple elements.

[0043] Calculation Parameters

[0044] The following input, intermediate calculation, and output parameters are ostensibly specified in SI units (indicated in brackets below); however another system may be supplanted if desired.

[0045] 1. Input Parameters [0046] Q.sub.pipe [m.sup.3/s] Volume flow-rate through the porous pipe and thereby to pass through the pores. [0047] P.sub.pipe [N/m.sup.2] Porous pipe pressure at the process pipework connection. [0048] P.sub.air [N/m.sup.2] Absolute air pressure at the water body surface. [0049] Z.sub.sect [m] Depth at seaward and shoreward ends of each section. [0050] μ [N.Math.s/m] Average dynamic viscosity of the pipe and water body fluid. [0051] ρ [kg/m.sup.3] Average density of the pipe and water body fluid. [0052] t.sub.wall [m] Porous pipe wall thickness (may be a function of location). [0053] ϵ.sub.pipe [m] Roughness of porous pipe wall internal surface.

[0054] 2. Intermediate Calculation Parameters [0055] D.sub.sect [m] Diameter of a section (assumed to be constant for the section). [0056] L.sub.sect [m] Length of a section. [0057] n Number of elements in a section. [0058] L.sub.ab [m] Length of an element. [0059] H.sub.a, H.sub.b [m] Water head at element ends a and b.

[0060] P.sub.a, P.sub.b [N/m.sup.2] Dynamic pressure at element ends a and b.

[0061] Po.sub.c, Po.sub.d [N/m.sup.2] Static pressure at element modelled pore point c and water body point d. [0062] u.sub.ac, u.sub.cb [m/s] Fluid velocity element end a to point c, and point c to end b. [0063] Re.sub.ac, Re.sub.cb [m/s] Commensurate Reynolds number element end a to point c, and point c to end b. [0064] f.sub.ac, f.sub.cb [m/s] Commensurate friction factor element end a to point c, and point c to end b. [0065] hf.sub.ac, hf.sub.cb [m/s] Commensurate frictional loss end a to point c, and point c to end b. [0066] V.sub.ac, V.sub.cd, V.sub.cb Volume flowrate element ends a and b, and modelled pore point c and water body point d.

[0067] 3. Output Parameters [0068] L.sub.pipe [m] Required length of the designed porous pipe to operate at the given flow envelope. [0069] Q.sub.pores [m] Volume flowrate out of the pores of a section of pipe. [0070] Material.sub.dist The material construction used at any given distance along the pipe. [0071] Permeability.sub.dist The resulting permeability at any given distance along the pipe.

[0072] Detailed Calculations

[0073] The design and method of manufacture provided for in U.S. patent application Ser. No. 15/552,868 allows for the distribution and dimension of pores to be accurately controlled, thereby controlling the amount of porosity and overall water flow-rate through the pipe wall at any given location. Subsequently, in accordance with the second aspect of the invention, a method has been provided to determine the optimum manufacturing parameters and design for the porous pipe given a demanded discharge or intake volume flow-rate. The calculations can be performed by a computer processor executing instructions comprising the algorithms for performing the calculations, such as by executing a software program stored on a tangible computer readable medium, which executes a number of iterative loops using a computer processor. The calculation steps will now be described with reference to FIG. 5, which shows an example of an element 500.

[0074] As discussed previously, an accurate permeability of a material, given in volume flowrate per area per pressure difference with material thickness, is derived through empirical means. An empirical permeability value is only valid for the pressure differences and material thicknesses that it has been tested with. Therefore, such values are monitored and only valid materials are allowed to be used for a section.

[0075] The fluid velocity (u.sub.ac) through the first half of the element length is calculated from the average element diameter (D.sub.sect) and required volume flow-rate (Q.sub.ac or Q.sub.a) (1).

[00001]$\begin{array}{cc}{Q}_{ac}=u_{ac}\times \frac{D_{\mathrm{sect}}^2}{4}& \left(1\right)\end{array}$

[0076] Flow conditions at an end 501 of the element 500 (end “a”) determine the relevant head H.sub.a using Bernoulli's equation (2), and Reynold's equation (3) assuming a fully developed flow.

[00002]$\begin{array}{cc}{H}_a=\frac{P_a}{\rho g}+\frac{u_{ac}^2}{2g}+z_a& \left(2\right)\\ R{e}_{ac}=\frac{\rho \times u_{ac}\times D_{\mathrm{sect}}}{\mu }& \left(3\right)\end{array}$

[0077] The average Reynold's number over the first half of the element 500 with the Colebrook-White equation (4) and material roughness is used to determine the relevant Darcy friction factor.

[00003]$\begin{array}{cc}\frac{1}{\sqrt{f_{ac}}}=-0.869\ln \left(\frac{ϵ}{3.7D_{\mathrm{sect}}}+\frac{2.523}{R{e}_{ac}\sqrt{f_{ac}}}\right)& \left(4\right)\end{array}$

[0078] The Darcy-Weisbach equation (5) is subsequently used to calculate the head loss (hf.sub.ac) over the first half of the element 500, and thereby the remaining head (H.sub.c) at a location with a pore in the element 503 (“c”), typically half-way between ends 501 (“a”) and 502 (“b”)

[00004]$\begin{array}{cc}{H}_c=H_a-\Delta h{f}_{ac}=H_a-f_{ac}\frac{L_{ac}}{D_{\mathrm{se}\mathrm{ct}}}\frac{u_{ac}^2}{2g}& \left(5\right)\end{array}$

[0079] The difference in pipe static pressure (6) and water body static pressure (7), with the material permeability, thickness, and elemental surface area, allows calculation of the volume flowrate through the pores of the element 500 (8).

Po.sub.c=H.sub.c×gρ  (6)

Po.sub.d=depth.sub.d×gρ  (7)

Q.sub.pores=Permeability.sub.wall×(Po.sub.c−Po.sub.d)×(π×D.sub.sect)×L.sub.ab÷t.sub.wall  (8)

[0080] The volume flowrate (Q.sub.b or Q.sub.cb) at the other end 502 of the element 500 is given by the continuity equation (9), thereby allowing the head (H.sub.b) to be derived which forms the input for the next element.

Q.sub.a−Q.sub.pores=Q.sub.b  (9)

[0081] The results of the calculation for each element 500 can be congregated, thereby calculating the total flow-rate (Q.sub.pipe) that a porous pipe of the specified dimensions may tolerate at a designated positive or negative pressure difference with the water body.

[0082] By iteratively changing any of the aforementioned porous pipe design parameters and materials selection, and recalculating the resulting flow characteristics, the porous pipe design can be optimized for an installation's required process flow.

[0083] In additional embodiments of the present application, shown for example in FIGS. 6A-6C, one or more piezoelectric vibrational devices 601 can be affixed directly to the porous pipe wall 602. A piezoelectric actuator 603 connects the inner or outer surface of the porous pipe wall 602 to a counterweight 604, with the entire structure of the piezoelectric vibrational device 601 protected by a permanent watertight cover 605. An alternating voltage supplied by an electrical cable encased within a duct or within the pipe matrix is applied to the piezoelectric actuator 603 causing the piezoelectric actuator 603 to expand and contract at a commensurate frequency.

[0084] Consequently, coupled with the counterweight 604, a cyclical force is applied to the pipe wall 602. The pipe wall 602 stiffness is high and known, such that the pipe may vibrate at a fundamental frequency, thus maximizing the effect of cleaning and removing debris from the pores. The piezoelectric devices 601 can be located periodically or strategically along the length pipe and at any orientation, as shown for example in FIGS. 6B and 6C.

[0085] In summary, the present application relates to an intake or discharge structure commonly used to transfer water between process pipework and a general water body, such as a lake or sea, including, but not limited to, the following: an applicable intake or discharge structure comprising a novel design of porous pipe laid on, near, or under the seabed, or generally submerged within the body of water; the use of a plurality of pores throughout the full surface area of the porous pipe wall through which water will flow; the use of pores accurately manufactured in diameter and length such that the amount of porosity at any location of the porous pipe wall can be controlled; an application of varying the amount of porosity along the length of the pipe; a structure comprising such a porous pipe acting to distribute discharged water over an area; an application of filtering water to a fine degree of filtration along the whole length of the porous pipe directly within the water body; an ability to reduce the intake velocity of water from the immediate water body to velocities far below those currently generally seen; an intake structure with an intake velocity below the settling velocity of particulates within the water body; and a unique method of applying high frequency vibration to the porous pipe wall to dislodge particulates that have become embedded within pores.

[0086] It should be understood that, unless stated otherwise herein, any of the features, characteristics, alternatives or modifications described regarding a particular embodiment herein may also be applied, used, or incorporated with any other embodiment described herein. Also, the drawing herein is not drawn to scale or orientation.

[0087] While there have been shown and described and pointed out fundamental novel features of the invention as applied to preferred embodiments thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices and methods described may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice.