Aerodynamic tube shields
Novel aerodynamic tube shields are presented herein. One embodiment may be comprised of a body, such as a semi-cylindrical body, for protecting against a tube's hostile environment and first and second fins, which may be tapered, for redirecting the flow of gas in the area around the tube.
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This application claims priority to U.S. patent application Ser. No. 61/355,783, which is hereby incorporated by reference.
FIELD OF THE INVENTIONThe present invention relates to tube shields and baffles generally. More specifically, the present invention relates to aerodynamic tube shields.
BACKGROUND OF THE INVENTIONIn many applications and environments, such as boilers (including evaporators therein), gas has a tendency towards certain areas. This unequal gas flow distribution can reduce heat transfer efficiency among tubes in these applications and environments, and further results in such tubes being fouled and worn more quickly.
Baffles may be used to redirect gas flow, but have many drawbacks and, correspondingly, are frequently not used in many applications and environments (including boilers). Baffles are typically solid, flat plates that run from one area in an application or environment to another. For example, in the context of a boiler, a baffle might run from a rear wall to the center of a pass. This eliminates portions of the tubes in the boiler from heat transfer and a substantial part of the gas net flow area, as well as increases gas velocity in other tube areas, resulting in the degradation of the tubes. Tube shields are known in the art to be useful to a protect a tube against the hostile environment in which the tube resides, but are not known to assist in gas flow distribution.
In view of the foregoing and for other reasons, there is a need in the art for an aerodynamic tube shield that can more efficiently and effectively redirect gas flow in an application or environment, while simultaneously providing a shield to protect the tube from its hostile application or environment.
SUMMARY OF THE INVENTIONNovel aerodynamic tube shields are presented herein. One embodiment may be comprised of a body, such as a semi-cylindrical body, for protecting against a tube's hostile environment and first and second fins, which may be tapered, for redirecting the flow of gas in the area around the tube.
The invention disclosed herein can be conceptualized as an aerodynamic tube shield that can be used in a variety of applications to help maximize heat transfer efficiency and alleviate the effects of unequal gas flow distribution, while simultaneously providing a shield to protect a tube against an application's environment.
The body 10 may have a first edge 12a, a second edge 12b, a first end 14a, and a second end 14b. The first fin 20 may extend longitudinally along said first edge 12a of the body 10, and the second fin 20′ may extend longitudinally along said second edge 12b of the body 10. Said fins 20, 20′ may similarly each have an outside edge 22, 22′, a first end 24a, 24a′, and a second end 24b, 24b′. In certain embodiments, said fins 20, 20′ may be tapered, such that each said fin 20, 20′ is wider at or near its first end 24a, 24a′ than at or near its second end 24b, 24b′, and, correspondingly, the outside edge 22, 22′ of each said fin may be sloped. In certain other embodiments, the fins may not be sloped or tapered. The degree of tapering (if any) and length of each fin 20, 20′ may help to, among other things, control the flow and distribution of gas in an application or environment (such as a boiler) and, more specifically, in the banks of the tubes in such application or environment, and may be dictated by the desired redistribution of gas across such tubes. In some embodiments, the spacing of the tubes in the boiler may affect the tapering of the fins 20, 20′, and the farther apart said tubes are, the wider the fins 20, 20′ may be. In certain embodiments, the respective first ends 24a, 24a′ of the fins 20, 20′ may touch, or nearly touch, the respective first ends 24a, 24a′ of the fins 20, 20′ of the tube shields on the adjacent tubes. Also in certain embodiments, the respective first ends 24a, 24a′ or second ends 24b, 24b′ of the fins 20, 20′ may be interlocked or welded to the respective first ends 24a, 24a′ or, as the case may be, second ends 24b, 24b′ of the fins 20, 20′ of the tube shields on the adjacent tubes. Each fin 20, 20′ may be comprised of the same types of materials as the body 10, including, for example, steel (including carbon steel). It should also be appreciated the body 10 and the fins 20, 20′ may be formed from a single piece of material (such as a single piece of metal).
The aerodynamic tube shield 2 of the present invention may be secured to a tube 4 by various means. In certain embodiments, one or more fasteners may be used to secure said tube shield 2 to said tube 4. Said fasteners may include, without limitation, a number of different types of fasteners, including snaps, clips, bolts, and straps. During installation of an aerodynamic tube shield 2, a thin layer of a high thermal conductivity material, such as mortar, may be deposited under each tube shield 2 or on the surface of the applicable tube 4 on which the tube shield 2 is to be placed. Said tube shield 2 may be installed on any side of the applicable tube 4, including the top or bottom surface, as may be dictated by or desired under the circumstances. In certain embodiments, a tube shield 2 may be installed on the top surface of the applicable tube 4 and a second tube shield 2 may be installed on the bottom of such tube 4 (or vice versa).
Computational fluid dynamics (CFD) simulation results for such an EfW boiler evaporator will next be described. These simulation results show pressure, temperature, and velocity contour plots for a cross-section of such evaporator with and without aerodynamic tube shields of the present invention.
At the outset, it is noted that
With reference again to
The following results were also determined from the foregoing CFD simulations using CFD Ansys Fluent software:
As can be seen from the foregoing, there is a pressure drop in the evaporator 52 between the inlet 58 and the outlet 60 when either Test Embodiment One or Test Embodiment Two is used. The pressure drop with Test Embodiment Two is slightly smaller because such embodiment is shorter than Test Embodiment One. As can also be seen from the foregoing, in this particular boiler, Test Embodiment One enhances gas velocity and uniformity more than Test Embodiment Two. (These are measures of the uniformity of gas velocity and temperature throughout the evaporator.) As can further be seen from the foregoing, in this particular boiler, Test Embodiment One enhances heat transfer slightly more than Test Embodiment Two. (This is a measure of the energy being absorbed from the gas into the evaporator tubes.) As noted elsewhere, however, the dimensions (including length, width, and thickness) and placement of the aerodynamic tube shield that will work most effectively and efficiently for a given application will depend on such application. For example, in certain applications, gas velocity and temperature uniformity and heat transfer may further be improved by including aerodynamic tube shields on a row of tubes in the middle of the evaporator, as well as at the inlet and outlet. It is further noted that the foregoing CFD simulation results relate to only a cross-section of the evaporator (i.e., five of the 29 total tubes). Thus, if the additional 24 tubes in this particular simulated evaporator were taken into the account, the gas velocity and temperature uniformity and heat enhancements could be even higher.
Additional data was collected from the field regarding heat recovery in an evaporator in an EfW boiler before and after the use of aerodynamic tube shields with the dimensions of Test Embodiment One.
Although the foregoing application of the present invention relates to an evaporator in an EfW boiler, it should be appreciated that the aerodynamic tube shield of the present invention may be used in a wide range of applications, including a wide range of boilers, gasifiers, and heat exchangers and components therein. Indeed, the tube shields of the present invention may be used in any application where there is unequal gas flow distribution to help alleviate the effects of such unequal distribution and maximize heat transfer efficiency, while simultaneously providing a shield to protect the tube from the environment of the application.
Further, although the foregoing application of the present invention discussed the installation of aerodynamic tube shields at the evaporator inlet and outlet, it should be appreciated the aerodynamic tube shields of the present invention may be installed in various locations in EfW boilers (as well as boilers of various other types and designs), depending on the tendencies of the relevant gas passing through the applicable boiler, as may be determined by engineering analysis (such as CFD modeling).
Claims
1. A tube shield for protecting a tube and simultaneously directing the flow of gas, said tube shield comprising:
- a. a body configured for protecting a tube, said body having a first edge and a second edge;
- b. first and second fins configured for directing the flow of a gas, wherein said first fin extends longitudinally along said first edge of said body and said second fin extends longitudinally along said second edge of said body.
2. The tube shield of claim 1, wherein said tube shield is configured for insertion onto a tube in a boiler, gasifier, or heat exchanger.
3. The tube shield of claim 1, wherein said body is semi-cylindrical.
4. The tube shield of claim 3, wherein said body has a radius substantially the same as an outer radius of said tube.
5. The tube shield of claim 1, wherein said first and second fins each have first and second ends and are tapered such that each said fin is wider at its first end than at its second end.
6. The tube shield of claim 1, wherein said body and first and second fins are formed from a single piece of material.
7. The tube shield of claim 1, wherein said body and first and second fins are comprised of steel.
8. The tube shield of claim 1, further comprising one or more fasteners.
9. The tube shield of claim 8, wherein said fasteners are snaps, clips, bolts, or straps.
10. An aerodynamic tube shield, said aerodynamic tube shield comprising:
- a. a body; and
- b. a first fin and a second fin, wherein said first fin extends longitudinally along a first side of said body is tapered and said second fin extends longitudinally along a second side of said body and is tapered;
- c. wherein said body and first and second fins are configured for protecting a tube and simultaneously directing the flow of gas.
11. The aerodynamic tube shield of claim 10, wherein said aerodynamic tube shield is configured for insertion onto a tube in a boiler, gasifier, or heat exchanger.
12. The tube shield of claim 10, wherein said body is a semi-cylindrical body having a radius substantially equal to an outer radius of a tube.
13. The tube shield of claim 10, wherein said body and first and second fins are formed from a single piece of metal.
14. The tube shield of claim 10, further comprising fastening means that can be used to secure said tube shield to a tube.
15. An aerodynamic tube shield, said aerodynamic tube shield comprising:
- a. a body having a first edge, a second edge, a first end, and a second end, said body being configured for protecting a tube; and
- b. means for redirecting the flow of gas in an environment having unequal gas flow distribution.
16. A method for redistributing gas flow across and protecting tubes in a system having unequal gas flow distribution using aerodynamic tube shields, wherein said system has multiple rows of tubes, said method comprising the steps of:
- a. obtaining a plurality of aerodynamic tube shields having tapered fins configured for redistributing the flow of a gas and a body configured for protecting a tube;
- b. installing an aerodynamic tube shield on one or more tubes in a first row of tubes in said system; and
- c. installing an aerodynamic tube shield on one or more tubes in a second row of tubes in said system.
17. The method of claim 16, wherein said system is a boiler, gasifier, or heat exchanger.
18. The method of claim 16, wherein said first row of tubes is at an inlet in an area in said system.
19. The method of claim 16, wherein said second row of tubes is at an outlet in an area in said system.
20. The method of claim 16, further comprising the step of, before installing each aerodynamic tube shield, depositing a thin layer of a high thermal conductivity material under said aerodynamic tube shield or on a surface of the tube on which the aerodynamic tube shield is to be installed.
21. The method of claim 20, wherein said high thermal conductivity material is mortar.
22. A system for improving unequal gas flow distribution and protecting tubes, said system comprising:
- a. one or more rows of tubes;
- b. a plurality of aerodynamic tube shields, wherein each said aerodynamic tube shield is comprised of a body and one or more fins tapered for directing the flow of gas and wherein said plurality of aerodynamic tube shields are installed on one or more tubes in a first row of tubes and one or more tubes in a second row of tubes.
23. The system of claim 22, wherein said one or more rows of tubes are in a boiler, gasifier, or heat exchanger.
24. The system of claim 23, wherein said first row of tubes is at an inlet in a first area of said boiler, gasifier, or heat exchanger and said second row of tubes is at an outlet in said first area of said boiler, gasifier, or heat exchanger.
25. The system of claim 24, wherein said plurality of aerodynamic tube shields are installed on said first row of tubes and said second row of tubes along a rear wall of said boiler, gasifier, or heat exchanger.
Type: Application
Filed: Dec 23, 2015
Publication Date: Apr 28, 2016
Applicant: COVANTA ENERGY CORPORATION (Fairfield, NJ)
Inventor: Grigory Epelbaum (Morristown, NJ)
Application Number: 14/757,495