Title of Invention: A set of water-cooled panels for electric arc furnaces

Technical Field

[0001] The present invention relates generally to electric arc furnaces, and more particularly to the structure of improved cooling panels having wavy fins for increasing heat transfer efficiency.

Background Art

[0002] A water-cooled panel is an important component of many electric arc furnaces. It is typically a rectangular panel made of copper that is closely fitted to the inside walls of the furnace. Water is circulated through channels within the panel through a system of pipes, allowing it to absorb the heat generated during the melting process. This helps to protect the refractory lining of the furnace, prevent overheating, and minimize the risk of damage to the furnace structure. The water-cooled panel acts as a "heat sink" by absorbing much of the heat generated by the furnace, which is essential for optimizing the efficiency and productivity of the furnace. The panel also helps to maintain the overall temperature of the furnace by preventing hot spots that could lead to uneven melting and poor quality of the final product. Overall, the water-cooled panel is an essential component of electric arc furnaces that is critical to maintaining the stable operation of the furnace and the quality of the final product.

[0003] Some patents disclose some improvements in the water-cooled panels, for example:

[0004] US patent No. 4417343, discloses a water-cooled lid for an electric furnace comprising divided sectorial segments, each of the sectorial segments having a cooling water inlet and a cooling water outlet and being formed in its interior with a zigzag cooling water channel for holding the inlet in communication with the

[0005] US patent No. 4107449, discloses a furnace in which a water-cooled roof is made up of a circular ring that supports a box-shaped structure made from metal plates. The structure is divided into two parts where water is circulated through discrete roof panels or sections to cool the roof. [0006] US patent No. 4351055, discloses a water-cooled wall element consists of a plurality of parallel, horizontally extending and vertically superimposed tubes, a cooling water inlet connected to the lowermost tube, a cooling water outlet connected to the uppermost tube, and return bends connecting the ends of proximal tubes to each other.

Summary of Invention

[0007] According to this invention, a set of water-cooled panels is provided in an electric arc furnace, which covers part of the roof and/or wall of the furnace and each part of panel consists of a number of independent curved tubes, which are configured in such a way that the panel has a spiral structure and both tubes are connected with U-shaped caps and there is an empty space between the two curved tubes where the fluid inside the panel tubes exchanges heat with the air layer between the tubes and inside the curved tubes there are some fins with a wavy shape, which have some supports, and fins are attached firmly to the tube in the inlet section of the tube by at least one support.

Technical Problem

[0008] High temperature in arc furnaces causes the water panels to deform and crack. The mean life of ceiling panels is less than one year in most cases. Another problem in panels used in the roof of electric arc furnaces is thermal shock and fluid phase change due to the heat transfer of the fluid inside the tubes of the water water-cooled panel with the roof of the furnace.

Advantageous Effects of Invention

[0009] In this invention, to solve said problems, a water-cooled panel with an improved heat transfer assembly is disclosed, which increases the amount of heat transfer between the surface of the furnace and the panel, as a result, improves the performance of the panel. Reducing the stopping or shutting down of the electric arc furnaces due to the perforation of the panels are other effects of improvements of this invention

Brief Description of Drawings

[0010] Fig.1 illustrates a perspective view of a set of water-cooled panels which cover some parts of the wall and the ceiling of an arc furnace from the inside. [0011 ] Fig. 2 illustrates a pie-shape water-cooled panel in which wall and roof sections of the panel are shown.

[0012] Fig. 3 illustrates a section view of a pie-shape water-cooled panel in which wavy fins are inside the tubes.

[0013] Fig. 4 illustrates a perspective view of a water-cooled panel in which the circulation parts of fluid are shown as the upper part and the lower part of the panel.

[0014] Fig. 5 illustrates a perspective view of a pie-shape panel with inside wavy fins in tubes.

[0015] Fig. 6 illustrates a perspective view of a pie-shaped panel and details of wavy fins and supports inside the tubes.

[0016] Fig. 7 depicts an exemplary mesh of fluid flows.

[0017] Fig. 8 shows a diagram of the temperature change of outlet fluid at 1600°C at various pressures.

[0018] Fig. 9 shows a diagram of the temperature change of outlet fluid at 1800°C at various pressures.

Description of Embodiments

[0019] The main object of this invention is to provide an improved water-cooled panel for arc furnaces, which eliminates the disadvantages of the prior art, increases the amount of heat transfer between the surfaces of the furnace and the panel, and increases the performance of the panel.

[0020] The water-cooled panel(10) disclosed in this document is an integrated panel that is simultaneously used for heat transfer with the ceiling and walls of the electric arc furnace. The panel set(10) consists of a number of pie-shaped panels(20) that cover the ceiling and wall of the furnace in a circular arrangement. In one embodiment of the invention, the panel(20) is integrated and made one-piece item, which covers both some part of the wall and the ceiling of the electric arc furnace

[0021 ] . According to Fig. 1 , water-cooled panels (20) have been used for protecting the ceiling and walls of the furnaces. Due to the high melting temperature in the electric arc furnace, it is important to protect the metal structure of the furnace body.

[0022] The main panel consists of some pie-shaped panels(20) that cover the ceiling and the walls of the electric arc furnace in a circular arrangement. Each panel(20) consists of a number of separate and independent tube(22), each tube has a certain curvature, and the opening and end of each tube is connected with U- shaped connecting parts(30), so that the panel(20) has a spiral structure with a gradual increase in length of the tubes, which each part can be replaced in case of a defect in any part of the panel, tube or connecting piece. To increase the life of the panels (20) and the uniform cooling effect, wavy fins(24) are installed inside the tubes(22) of the panel. When the fluid(water) moves inside the tubes(22) equipped with wavy fins(24), the wavy fins(24) cause rotation of fluid and increase turbulence in the fluid inside the panel tubes

[0023] Each pie-shaped panel(20) comprises two interconnected parts. The roof section(20a) includes a number of spiral tubes(22) covering and protecting the ceiling of the electric arc furnace(10) and the wall section(20b) includes a number of spiral tubes(22) covering some part of the wall of the furnace.

[0024] As shown in Figures 2 and 4, the panel has a pie-shaped cross-section with curved heat tubes(22), each tube having a circular cross-section. From the side view, as shown in Figure 4, the return tube is a cross-section of a pipe that has a straight section and an inclined section. The inclined part of the return pipe is parallel to the walls of the electric arc furnace.

[0025] Each pie-shaped panel(20) has an inlet (25) and an outlet(26). The panel inlet cooling fluid is water for economic reasons in many practical and industrial examples. The inlet(25) and the outlet(26) are anticipated in the middle of the panel(20). The cooling fluid travels(circulates) up the length of the panel and then is transferred to the end of the panel through the return tube(27), which is a tube on the outer edge of the panel, and fluid after passing through the spiral path, returns to the middle of the panel and then comes out of the outlet(26). The cooling fluid first enters the panel from the inlet section(25) and cools the upper part(28a) of the panel(20), and then it is transferred to the lower part(28b) of the panel through the return tube(27), and after passing through the spiral path, it returns to the middle of the panel. Finally, it exits from the outlet(26) of the panel(20).

[0026] One of the common problems in water-cooled panels used in the roof of electric arc furnaces is thermal shock and fluid phase change due to the heat transfer of the fluid inside the tubes of the water water-cooled panel with the ceiling of the furnace. In order to solve this problem, blades or fins(24) with a wavy or sinusoidal form are placed inside the curved tubes(22) in the present invention, which have a number of protrusions as horizontal and/or vertical support(32).

[0027] Wavy fins(24) inside tubes(22) increase the surface area of the tube(22) in contact with the fluid, which can enhance the transfer of heat from the water to the surrounding air or other medium. This increased surface area can promote more uniform distribution of heat throughout the tube as well as reduce the likelihood of hot spots. Additionally, the presence of fins can create some degree of flow turbulence, which improves mixing fluid flows and prevent stagnant areas within the tube(22).

[0028] The use of in-tube fins can create some degree of flow turbulence, which can help to improve mixing and prevent stagnant areas within the pipe. This flow turbulence can also create a rotational motion within the fluid, known as flow rotation. The presence of flow rotation can further enhance the transfer of heat from the water to the surrounding air or other medium by promoting better mixing and distribution of heat throughout the tube and prevents the creation of hot spots(high-temperature spots), which increases the heat transfer rate and the life of the panels.

[0029] In other words, the tubes of the panel have a number of fins (24) whose side section is wavy or crooked. This wavy shape can be sinusoidal or spiral or other wavy shapes with different steps whose dimensions (geometric properties) are proportional to the dimensions of the tube(22).

[0030] One of the problems in common water-cooled panels is the lack of uniform distribution of heat in the panel tubes(22). If the wavy fins(24) is used inside the curved tubes(22) of the water-cooled panel(20), the heat transfer rate increases and can be effective in improving the efficiency of the water-cooled panel(20). In other words, the presence of the wavy fin (24) causes the creation of a rotating flow and better distribution of heat in the fluid in the curved tubes(22) of the panel(20) and prevents the creation of thermal shock and high-temperature spots or hot spots. Also, the wavy fin changes the speed profile of fluid in the tube and increases the heat transfer coefficient, which improves the performance of the panel.

[0031] The panel disclosed in this document has fewer tubes(22) than conventional panels. In one embodiment of the invention, at least two tubes were eliminated from the set of panel tubes hence the number of tubes has been reduced compared to the conventional example, which makes the weight of the panel lighter and the gap(empty space) between the tubes has been increased. In the panels proposed in the prior art, the spiral tubes of the panel were either stuck together or had a very slight distance from each other. The created gaps increase the heat transfer coefficient of the panel with the outside.

[0032] Fin(24) with wavy or spiral form can be galvanized metal or steel, but it is not limited to said materials. The purpose of choosing galvanized material is to be lightweight and economical. The fins made with this material move easily inside the tube due to their proper weight and strength.

[0033] The way to install and place the wavy fins(24) inside the curved tubes(22) of the panel(20) is in such a way that a wavy fin proportional to the length of the pipe is considered inside each curved tube (22). In order to fix the wavy fins(24) in the center of the tube(22), a number of small parts(32) as supports are placed at a certain location of the fin(24). These parts(32) are used as supports and prevent movement of the fin(32) from the center of the tube(22).

[0034] The way to install the wavy fins(24) inside the curved tubes(22) is that the wavy fin(24) is connected to the body of the tube through horizontal or vertical supports(32) in the fluid inlet section, for example, one of them is welded after inserting and meanwhile, the other supports(32) do not have a fixed connection with interior of tube(22). Therefore, in case of defect or failure in any part of the panel, pipe, and connecting piece, the said fin can be replaced or fixed easily. According to this installation and placement method, defective tubes are disposed and replaced more quickly. [0035] In one of the embodiments of the invention, the supports(32) are integrated with the wavy fin body and are extended in different directions of the body to keep the fin(24) fixed in the center of the tube(22).

[0036] In one embodiment of the invention, the wavy fin height is 15 mm, the fin thickness is 0.5 mm, the pitch of the wavy fin is 25 mm, the support length is 25 mm, the support width is 5 mm, and the total number of supports is 5. The said supports(32) are placed or extended horizontally and vertically, and the number of supports and their distance from each other is proportional to the length of the tube.

[0037] In this invention, the study of the effect of parameters such as fluid volume, flow rate, and changes and effects of the parameters shows that the presence of wavy fins in the panel has a great effect on the heat transfer rate of the fluid flow in the pipes as shown in figures 7,8 and 9. According to the investigations carried out on the design of the new panels of electric arc furnaces, along with a comprehensive study of operational measures, taking a sample to simulate in computational fluid dynamics (CFD) simulation software. In order to evaluate the design of the panel with wavy vanes, several studies were conducted, and finally, numerical simulations and comparisons with the old design showed that the changes made in this invention increased the lifespan of the panels and reduced energy losses in electric arc furnaces. Increasing the heat transfer rate and reducing the stopping or shutting down of the electric arc furnaces due to the perforation of the panels are other effects of improvements of this invention. For example as shown in figure 8, when the temperature of fluid is 1800°C in different pressure ranges, the temperature of outlet fluid increase between 2°C and 5°C which means the panel disclosed in this invention has a better heat transfer coefficient than prior arts. Again as shown in the figure 9, when the temperature of fluid is 1600°C, the outlet temperature increases almost 2° C in different pressures.