KR102188806B1 - Coil bundle for multilevel heating - Google Patents

Abstract

In an embodiment of the present invention, a heating coil bundle 20 for heating a tank 10 comprising one heating coil body and three supports 40 is described. The bundle 20 is connected in series to prevent leakage at the open end, extends in a parallel and spaced relationship with each other, and is arranged at a plurality of levels (levels) 24, a plurality of straight tubes (tubes) 32 ) And a plurality of U-shaped tubes 34. The cross section of the bundle 20 is characterized by a binary-matrix-like tube pattern 22 of M rows 24 and N rows 26. The disclosed heating coil bundle 20 generates a large-scale circulation 52 of the heated fluid 50, and superimposes the large-scale circulation 52 induced by the convective circulation with the convection induced by buoyancy to transfer more efficient heat. Provides a mechanism.

Description

Coil bundle for multilevel heating

The present invention relates to a tanker (tanker) cargo heating apparatus.

Tankers transport various types of high viscosity fluids that require significant effort during off-loading. Accordingly, the tanker is provided with a cargo heating means for increasing the fluid temperature to lower the viscosity and improve the fluid offload.

Tanker cargo heaters are traditionally implemented with steam driven heating coils, which are heating tubes arranged along one or two levels that transfer heat from steam to fluid by a natural convection mechanism. It is evenly distributed throughout the lower part. The cumulative length of the tanker heating coil is over several thousand meters, so the tanker cargo heating system is an important item in the cost of building a tanker. The application of a more effective heating coil makes it possible to reduce the required heating coil length, thus reducing the construction cost of the tanker as a whole.

In a paper I. Pivac, G. Magazinovic, Numerical analysis of tank heating coil heating process, in C. Guedes Soares et al. (Eds.), Towards Green Marine Technology and Transport, CRC Press, London 2015, pages 603-608, the authors report the results of a numerical simulation showing the presence of a powerful heating fluid circular motion around an axis perpendicular to the tank cross section, 608 Page. The reported motion is a phenomenon of the technique known as the so-called large-scale circulation, see R. Krishnamurti and L. N. Howard, Large-scale flowgeneration in turbulent convection, Proc. Natl. Acad. Sci. USA, Vol. 78, No. 4, pp. 1981-1985, April 1981.

Large-scale circulation of heated fluid is the core of the present invention as it enables a more effective heat transfer mechanism by superimposing forced convection by large-scale circulation with natural convection induced by buoyancy, see VDI Heat Atlas, Springer-Verlag, Berlin 2010, page 684.

Regarding the patent publication, Japanese Utility Model JP3048878U (Shin Kurushima Dockyard, 1998) describes a collapsible heating unit in which heating tubes are arranged in only one level. The challenge to be solved is to simplify the tank cleaning process by enabling the rotation of the heating unit and making use of the solidified cargo residue under the unit; Fig. 1 of the citation. In addition, this document describes a conventional heating coil arrangement in which the heating coil covers a significant portion of the lower portion of the tank area; For example, Figure 2 of the cited document shows that about 40% of the lower portion of the tank area is covered by a heating coil.

This application provides an alternative approach to solving the problem. According to an embodiment of the invention, the heating coil bundle is characterized by a very small footprint; It can be easily cleaned without having to remove the bundle. In addition, most of the bottom of the tank is kept without the tank heating device. For example, less than 2.5% of the bottom of the tank area is covered with heating coil bundles; See Fig. 6 of this application.

Chinese patent CN101362509A (Wenchong Shipyard, 2009) describes a method of installing multiple bunker tanks. A two-level heating coil arrangement is described. The challenge to be solved is to reduce the difficulty during coil installation. Because the coils are arranged close to the vertical tank wall surrounded by the components of the vessel; Figure 1 of the cited literature; The possibility of improving heat transfer by fluid circulation is limited.

Japanese utility model application JPS5353786U (Hitachi Zosenkan, 1978) describes a multilevel heating coil bundle comprising 7 tube levels and 5 tubes per level; Figure 3 of the cited literature; Bundle length is determined by the bottom of tank particulars. The problem to be solved is a heating device with high heating efficiency. However, the described embodiment is surrounded by the structural elements of the vessel which greatly inhibit the free flow of heated fluid; Figure 4 of the cited literature; As a result, the possible heat transfer improvement is limited. In addition, the described embodiment includes a heating fluid inlet 10 arranged at the bottom tube level and a heating fluid outlet 11 arranged at the top tube level. Figure 3. A predictable result is the water hammer difficulty caused by the flow of condensing steam.

The present application provides an alternative approach to solving the problem of the cross-flow of heated fluid improving heat transfer. In addition, in order to suppress water hammer difficulty, a heating fluid inlet and a heating fluid outlet are disposed at the top and bottom levels of the tube, respectively.

Japanese patent application JPH0569893A (Shin Kurushima Dockyard, 1993) describes a method of installing a heating tube in a cargo tank. This document describes a single level of heating coil bundle that significantly reduces labor; Figures 1 and 2.

British patent application GB1054066A (J.H. Jefferson, 1967) describes a variable two-level heating coil bundle for cargo holds targeting solid cargo and liquid cargo. Multiple heating coils are arranged in two parallel rows; Figure 2 of the cited literature; Almost all lower portions of the tank area are covered by a heating coil.

Japanese patent JP2007238054A (Sumitomo Heavy Industries, 2007) is related to the reduction of ballast tank paint combustion defects due to welding operations; Leaving a passage for the working vehicle at the bottom of the tank; We describe a single level heating coil device that solves two problems. The cited document describes an asymmetric heating coil arrangement in which the heating coil is located near the longitudinal bulkhead of the vessel; 1 and 2 of the cited literature. The citation also describes a heated, heated cargo circulation enhanced using a convection plate (9). However, because the heating coil has a party in the corner of the tank; Where the heated fluid velocity is least; The impact of cargo circulation is limited. Further, most of the bottom (bottom) of the tank area is covered by a heating coil, and the covered area can be estimated to be about 60% of the bottom of the tank area; Figure 2.

The present application provides an alternative approach to solving the problem of providing passages on both sides of the heating coil bundle. In addition, because the number of bundle supports is small; For example, Figure 6 of the present application describes nine supports; The occurrence of bad ballast tank paint burnouts is limited.

According to the present invention, at least one comprising a plurality of straight tubes and a plurality of U-shaped tubes, a plurality of fastening means, and at least one support forming a compact and rigid structure that extends horizontally above the bottom of the tank. A heating coil bundle for heating a tank including one heating body is provided.

The supplied heating coil bundle is characterized by:

It causes large-scale circulation of heated fluid around an axis parallel to the longitudinal axis of the straight tube,

It enables an almost horizontal cross-flow (cross-flow) of the heated fluid through the empty space surrounding the straight tube and the U-shaped tube,

It provides a more effective heat transfer mechanism by superimposing forced convection by large-scale circulation on the convection induced by buoyancy.

The heating body consists of a straight tube and a U-shaped tube that are connected in series for leak-proof at the open end, and the bonding sequence starts by combining the straight tube and the U-shaped tube, and a series of continuous It proceeds by bonding, is disposed on the open end side of the U-shaped tube of a pair of tubes each including a straight tube and a U-shaped tube, and is finally completed by combining another straight tube. The result is a single heating body with one fluid inlet and one fluid outlet arranged at the level of a plurality of parallel and vertically spaced heating coil tubes secured to the support using a plurality of fastening means.

The cross section of the heating coil bundle perpendicular to the linear tube axis has a binary-matrix-like tube pattern of M rows and N columns, where the number of rows M is the total number of heating coil tube levels and the number of heating coil bundle rows. N is the maximum number of straight tubes arranged in any one of the M heating coil tube levels. The heating coil tube level is characterized by comprising at least one straight tube of a unique distance between the straight tube axis and the bottom of the tank.

The tube pattern of FIG. 2 is characterized by 6 rows and 3 columns, whereas the tube pattern of the bundle shown in FIG. 3 is characterized by only 20 rows and one column. The number of heating tubes placed at the tube level can vary. If any tube level is less than N tubes, the remaining elements of the pattern row are empty, see eg FIG. 2. The tube pattern represents the bundle tube arrangement ignoring the tube pitch. That is, the vertical pitch between levels can change like the horizontal pitch between tubes of the same level.

The heating fluid inlet is always located at the top level of the heating body in order to suppress possible water-hammer difficulties. 3. Similarly, the heating fluid outlet is always located at the lowest level of the heating body. Considering that the heating fluid temperature is highest at the fluid inlet and lowest at the fluid outlet, a high tube level is more thermally efficient than a thermally lower tube level. As shown in FIG. 2, the binary-matrix-like tube pattern enables the arrangement of straight tubes arranged at a high level of thermal efficiency and straight tubes arranged at a low level of thermal efficiency.

The tank heating process begins by heating the fluid that fills the empty space of the heating coil bundle tube. The heating fluid raises the temperature of the heating tube, which transfers heat to the surrounding heating fluid by a natural convective heat transfer mechanism. Due to the buoyancy effect, the heated fluid close to the heating tube begins to move upward, resulting in a number of small fluid swirls due to the dominant vertical flow of the hot fluid and friction between the hot and cold fluid particles. As the smoke of the heated fluid over time reaches the top of the tank, the process of gradually concentrating the vortex begins, and most of the small vortex ends in one large vortex known as the large-scale circulation. The result is the dominant circular motion of the heated fluid, and the fluid streamline takes the form of a concentric circle in FIG. 7. The large-scale circulation of the heated fluid is generated by the inflow of convective energy from the asymmetrically arranged heating coil bundle in Fig. 1, and is further strengthened by the outflow of convective energy through the tank wall, and is sufficient to develop the large-scale circulation. Sufficient heating time is required.

The heating coil bundle enables a large-scale circulation of nearly horizontal crossflow through the empty space surrounding the straight tube and the U-shaped tube, Figs. 1 and 7. This is an important feature for two reasons. First, horizontal cross flow minimizes pressure loss to fluid flow by creating the shortest cross flow path through the bundle. Second, the horizontal cross-flow is similar to the large-scale circulation path in the bundle region, and has little detrimental effect on the heated fluid flow structure.

This application satisfies several long-standing requirements known in the art. In addition to the improvement of heat transfer, the present application is characterized by:

This application enables more efficient tank cleaning by reducing the covered bottom of the tank area;

This application leaves a passage for the work vehicle;

And the present application reduces the difficulties associated with ballast tank paint burnouts due to welding operations.

The invention will be described with reference to the accompanying drawings and also by way of examples.
1 is a cross-sectional view of a tank with a heating coil bundle and a large-scale circulation of heated fluid outlined in dashed lines.
2 is a schematic diagram showing a typical heating coil bundle binary-matrix-like tube pattern.
3 is a perspective view showing a preferred embodiment of the heating coil bundle.
4 is a perspective view showing a heating fluid delivery tube.
5 is a perspective view showing a heating fluid transfer tube having an expansion bend as a thermal expansion compensation device.
6 is a perspective view showing a preferred embodiment of a tank heating system in which a heating fluid supply and discharge line is omitted for clarity.
7 is a schematic diagram showing a result of a numerical simulation showing large-scale circulation of a heated fluid.

The tank 10 filled with the liquid cargo 50 of Fig. 1 is equipped with a heating coil bundle 20; It extends in a parallel and spaced relationship to the tanker longitudinal symmetry plane 2 and to the tank inner side wall 18 slightly closer to the tank inner side wall 18 than the tank outer side wall 14; It is characterized in that it is coupled to the tank bottom 12 using a plurality of supports (40). The tank bottom 12 is a flat surface with no structures or devices that can impede fluid flow. The tank 10 is covered with a deck 16.

The heating coil bundle 20 of FIG. 3 is manufactured in advance in the workshop and is erected on the tank 10 where the support 40 is coupled to the tank bottom 12, and the heating fluid inlet 31 and the heating fluid outlet 39 Is leakproof coupled to the corresponding heating fluid supply and discharge line.

When the heat generated by one heating coil bundle 20 is not sufficient to meet the heating requirements of the tank 10, a plurality of heating coil bundles 20 need to be installed. For clarity, in FIG. 6, the heating fluid supply and heating fluid discharge lines are not shown.

The heating tubes 32 and 34 of FIG. 3 are carbon steel according to the type of cargo transported by the tanker; Stainless steel; Or some copper-based alloys. When the tube is made of a copper alloy, the tubes are joined to each other by welding when the tube is of steel or solder. The heating tube 32 is fixed to the support 40 by using a fastening means 42, usually a U-shaped bolt and nut. The heating coil bundle 20 is driven by steam, which is a heating fluid generated in a boiler located in a tanker engine room. Steam is distributed along the tanker deck by steam headers, where a steam manifolds diverge the intended steam into each heating body. Steam is guided to the tank bottom 12 from the deck 16 level steam descending pipe extending along the tanker transverse bulkhead, and the steam is supplied to the inlet 31 of each heating body using a horizontal transfer tube.

The heating coil heats the surrounding liquid by heat transfer from the vapor to the cargo liquid. Steam is gradually condensed due to the heat energy outflow. The tube length of the heating body should be sufficient to completely condense the vapor. The condensate after exiting the outlet 39 of the heating body is guided to the transverse bulkhead through a horizontal transfer tube, where the condensate lifts; A riser; And a steam trap is used to connect the heating body outlet 39 to a condensate manifold at the deck 16 level. The condensate manifold directs the condensate to the condensate header, which returns the condensate to the engine room and boiler.

The cross section of the heating coil bundle 20 has 20 rows of binary-matrix-like tube patterns 22, each of which is a tube level 24, and one row is only one straight tube 32. Include. The tube pattern 22 features one pattern column, while the heating coil bundle 20 is implemented by heating tubes 32 arranged in two physical columns, each row ( column) occupies one of the opposite sides of the support 40, FIG. 3.

The support 40 can be implemented in a variety of ways, from a simple single part standard profile as shown in FIG. 3 to a more complex multi-part structure capable of holding the heating coil bundle 20 rigidly. Built-in The multi-part support is suitable for a bundle of heating coils characterized by a more complex binary-matrix-like tube pattern 22, Figure 2.

The heating tubes 32 can be arranged as low as three levels 24, but the heating coil bundles 20 arranged at a higher number of tube levels 24 are arranged at a lower number of tube levels 24. It is more thermally efficient than the heated coil bundle. Accordingly, the heating coil bundle 20 of FIG. 3 is characterized by high thermal efficiency and low manufacturing cost due to its simple and compact design.

The distance between the inner side wall 18 and the center line of the straight tube 32 closest to the heating coil bundle 20 is 0.3 to 0.7 times the width of the tank 10; It is preferably 0.4 to 0.45 times.

The bundle 20 is located in the middle of the bottom of the tank 12 of FIG. 1, and the velocity profile of the large-scale circulation 52 is a straight tube 32 and U It is most powerful against the intended cross-flow through the voids surrounding the shaped tube 34. However, a slight deviation from the ideal midpoint is a preferred feature of the provided embodiment, as the exact midpoint position produces a less stable large-scale circulation and is prone to change in the direction of the circulation 52.

The vertical pitch, i.e. the vertical distance between two successive tube levels 24 of the tube pattern 22, is the fluid (e.g., the heated fluid through the voids surrounding the straight tube 32 and the U-shaped tube 34). 50) must be large enough to allow easy cross flow; The ratio of the vertical pitch of the tube pattern 22 to the outer diameter of the straight tube 32 is at least 1.25; It is preferably 3 or more.

Another embodiment of the invention comprises at least one heating fluid transfer tube 36, characterized in that, FIG. 4; The heating fluid delivery tube 36 is a single body having one fluid inlet and one fluid outlet; The heating fluid transfer tube 36 extends in a parallel and spaced relationship with the straight tube 32; The heating fluid delivery tube 36 is fixed to the support 40 using the plurality of fastening means 42.

Another embodiment of the invention comprises at least one tube thermal expansion compensating device 38; The heating fluid transfer tube 36 and the tube thermal expansion compensating device 38 are devices characterized in that they provide a single body having one fluid inlet and one fluid outlet and are connected in series to prevent leakage at their open ends. . 5 shows such a thermal fluid transfer tube 36, the tube thermal expansion compensating device 38 being implemented in the form of an expansion bend.

When the tank 10 heating demand is too high to be satisfied by the heating coil bundle 20, the plurality of heating coil bundles 20 minimize the detrimental effect of the bundle 20 on the flow structure of the heated fluid. In order to do so, it must be arranged longitudinally spaced from each other in exactly one row in the tank 10, Fig. 6.

Each of the heating coil bundles 20 has a heating fluid supply line and a heating fluid discharge line, and the heating fluid supply line and the heating fluid discharge line are the corresponding headers at the level of the deck 16, and the heating body The inlet 31 and the outlet 39 of the heating body are hydraulically connected.

As multiple heating coil bundles 20 are lined up along the length of the tank 10, a number of parallel supply and discharge lines traversing long distances between vertical downpipes and risers are required, and It extends along the partition wall and the corresponding heating fluid inlet 31 and outlet 39. In this configuration, the heating coil bundle 20 located closer to the bulkhead can assist heating fluid transfer to and from the bundle 20 located farther from the heat. . In addition, the heating fluid transfer tube 36; A portion of each heating coil bundle 20; Is conveniently used as a section of a supply line and a section of a discharge line.

The effect of large-scale circulation 52 on the thermal efficiency of the heating coil bundle 20 was numerically determined by transient simulations performed using the buoyantPimpleFoam solver in the OpenFOAM® 3.0 toolbox, a finite volume method software. Is verified; See, for example, F. Moukalled et al., Computational Fluid Dynamics: An Advanced Introduction with OpenFOAM® and Matlab®, Springer-Verlag, Cham 2016, pages 103-135 and 561-690.

For confirmation, a 7 bar steam driven heating coil bundle made of 5800 mm ² /s viscous oil is filled in the two-dimensional region 10 of Fig. 1, is discretized at about 150000 cells, and made of a 50A-sized steel tube (Fig. 3) ( 20) is heated for 3 hours.

The following table summarizes the results obtained. Pre-LSC column refers to a pre-circulation fluid flow stage during the initial 2700 seconds of heating; Whereas the LSC column represents a large circulating fluid flow stage developed for the remaining 8100 seconds of heating.

Physical quantity pre-LSC LSC Peak cross flow velocity, m/s 0.067 0.184 Average cross flow velocity, m/s 0.021 0.076 Average Richardson number,- 95.2 7.3

According to Y. I. Cho, G. A. Greene, Advances in Heat Transfer, volume 43, Academic Press, San Diego 2011, page 298, the Richardson number is a measure of the relative strength of the buoyant induced current to the imposed flow. It was reported that the average Richardson number decreased from 95.2 to 7.3, the large-scale circulation 52 affected the effect of forced convective heat transfer of the bundle 20 on the natural convective heat transfer of the bundle 20. It is for an order of magnitude, indicating improvement.

A typical simulated large-scale circular streamline is shown in FIG. 7.

Claims (7)

In the tank 10 heating apparatus comprising a plurality of heating coil bundles 20,
The plurality of heating coil bundles 20 extend horizontally and are connected to the tank bottom 12 by using a plurality of supports 40 disposed between the inner sidewall 18 and the outer sidewall 14, and the heating One of the coil bundles 20 is located closer to the middle side between the inner side wall 18 and the outer side wall 14 than to either side of the inner side wall 18 and the outer side wall 14,
As the plurality of heating coil bundles 20 extend exclusively in exactly one row along the length of the tank 10 in a manner spaced apart in the longitudinal direction, the heating coil bundle 20 is formed in each cross-section of the tank 10. Exist,
Each heating coil bundle of the plurality of heating coil bundles 20 includes a plurality of straight tubes 32; A plurality of U-shaped tubes 34; A plurality of fastening means 42; And including the plurality of supports 40 forming a compact and robust structure,
The plurality of straight tubes 32 and the plurality of U-shaped tubes 34 are arranged in at least three parallel and vertically spaced heating coil tube levels 24, each of the heating coil tube levels 24 Tank (10) heating device, characterized in that it comprises at least one said straight tube (32) of an inherent distance between the axis of the straight tube (32) and the tank bottom (12).
The method of claim 1,
One heating coil bundle among the plurality of heating coil bundles 20 includes at least one heating body;
The plurality of straight tubes 32 and the plurality of U-shaped tubes 34 leak from the open end providing the heating body having one fluid inlet 31 and one fluid outlet 39 Prevent series connection;
The joining sequence starts by joining the straight tube 32 and the U-shaped tube 34, opening the U-shaped tube 34 of a tube pair comprising the straight tube 32 and the U-shaped tube 34 It is completed by continuing a series of connections to the end face, and finally by joining another straight tube 32;
A tank (10) heating device, characterized in that the plurality of straight tubes (32) are fixed to the plurality of supports (40) using the plurality of fastening means (42).
The method of claim 2,
Each one heating coil bundle of the plurality of heating coil bundles 20 extends in a parallel and spaced relationship from the tank length symmetry plane 2,
Heating the tank 10, characterized in that each distance between the inner side wall 18 and the center line of the straight tube 32 closest to each heating coil bundle 20 is 0.3 to 0.7 times the width of the tank 10 Device.
The method of claim 3,
Tank (10) heating apparatus, characterized in that the ratio of the vertical pitch of the tube pattern (22) to the outer diameter of the straight tube (32) is at least 1.25.
The method of claim 4,
The at least one heating coil bundle 20 further comprises at least one heating fluid delivery tube 36,
The heating fluid delivery tube 36 is a single body having one fluid inlet 31 and one fluid outlet 39;
The heating fluid transfer tube 36 extends in a parallel and spaced relationship with respect to the plurality of straight tubes 32;
The heating fluid delivery tube (36) is fixed to the plurality of supports (40) using the plurality of fastening means (42);
Tank (10) heating device, characterized in that the heating fluid transfer tube (36) is conveniently used as a section of any one of the heating fluid lines extending within the tank (10).
The method of claim 5,
At least one of the heating fluid transfer tube 36 comprises a tube thermal expansion compensating device 38, and the heating fluid transfer tube 36 and the tube thermal expansion compensating device 38 have one fluid inlet (31) And a single body having one fluid outlet (39) to be continuously leak-proof connected at the open end.
The method according to any one of claims 4, 5 and 6,
The fastening means 42 is a U-shaped bolt and nut fastener, and the support 40 can reliably hold any one of the plurality of heating coil bundles 20 of an integral type or any built-in type. Tank 10 heating device, characterized in that it provides a multifunctional structure.

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