JP7036455B2 - Heat transfer promoter and its manufacturing method - Google Patents

Description

The present invention relates to a heat transfer promoter installed inside a radiant tube heater tube used in a heat treatment plant such as a metal annealing furnace, and a method for manufacturing the same .

In general, in annealing equipment and the like in a steel production process, a radiant tube type heating device (radiant tube heater) using a radiant tube as a heating means is often adopted. A radiant tube is a tube body in which a burner is placed inside a tube body having various shapes such as straight type, U type, L type, T type, W type, and even O type, and the tube body is heated by the burner to heat the tube body. It is a radiant heat transfer tube for heating an object to be heated such as a steel plate by radiant heat from the surface and removing distortion of the object to be heated. There are multiple continuous annealing furnaces in the steelworks, and dozens to hundreds of radiant tube type heating devices are used per furnace.
In November 2009, the Japan Iron and Steel Federation announced its approach to global warming countermeasures and promoted activities centered on the three eco-friendliness of "eco-process,""eco-product," and "eco-solution." Therefore, further improvement of energy efficiency and energy saving are important issues for the Japanese steel industry as a whole.
As part of the energy saving of annealing equipment, ceramic heat transfer promoters that promote heat transfer have begun to be installed on the inner walls of radiant tubes.

Patent Document 1 relates to a heat exchanger inserter provided in a molten steel furnace using a radiant tube, a boiler, etc. and a method for forming the same, and the outer surface of the heat exchanger inserter made of ceramic is spiral. It is described that the spiral shape of the outer surface enhances the heat exchange efficiency (column 8, lines 25 to 29). Further, the heat exchange insert has various shapes such as one provided with two blades (FIG. 2 and 3) and one provided with three blades (FIG. 6).

Further, Patent Document 2 relates to a heat transfer promoting device for a radiant tube, and the combustion gas temperature starts to decrease in order to prevent heat loss and efficiently transfer the amount of heat of combustion gas in the radiant tube to the radiant tube. It is described that a spiral-shaped guide blade 9 is installed in the latter half (columns 2 and 3), and as a result, it becomes possible to increase the heating capacity of the furnace, and the exhaust gas loss is reduced, which is a great energy saving effect. Is born (column 4).

Further, Patent Document 3 relates to a radiant tube and a heating furnace, and burns by arranging a heat transfer promoter 3 formed by processing a ceramic honeycomb as a lightweight structure having a high thermal conductivity in the radiant tube 1. It is described that it is possible to prevent local deformation of the radiant tube body while efficiently transferring the heat of the gas to the radiant tube body (paragraphs 0010, 0011, 0020).

U.S. Pat. No. 8,162,040 Japanese Unexamined Patent Publication No. 57-112694 Japanese Unexamined Patent Publication No. 2013-09644

In the invention disclosed in Patent Document 1, a heat exchanger inserter configured in a spiral shape is used to enhance the heat exchange efficiency, but the heat exchanger inserter is made of a heavy material. In addition, it is very expensive and the manufacturing cost is high, and the following problems (1) and (2) occur.
(1) Deformation due to the weight of the entire radiant tube (deformation due to creep phenomenon)
In a heat treatment plant such as a metal annealing furnace, the radiant tube has a high temperature of 700 ° C to 1200 ° C. In such a high temperature, a creep phenomenon occurs, and the radiant tube main body is deformed and bent with time due to the load of the entire radiant tube. Therefore, if the load of the heat transfer promoter is large, the load of the entire radiant tube is also large, and the deflection of the radiant tube body is large.
(2) Thermal response In the steel production process using a radiant tube type heater (radiant tube heater), changes in processing conditions such as steel type, steel plate thickness, line speed, and steel plate temperature at the outlet of the heating furnace can be changed. In order to respond, the plate temperature on the outlet side of the heating furnace is measured, and the combustion amount of the heating furnace is controlled so that this measured value matches the target value. Since the processing conditions such as steel type, plate thickness, speed, and target plate temperature are frequently changed, it is desired that the radiant tube type heating device is a device with a high thermal response that can quickly follow the changes in the processing conditions. If you are using equipment with a slow thermal response, the productivity of the steel production line will drop.
In the inventions disclosed in Patent Documents 2 and 3, heat is efficiently transferred to the radiant tube main body by using a spiral-shaped guide blade or by using a heat transfer promoter having a ceramic honeycomb structure. Although it is possible to obtain an energy saving effect, no consideration is given to the above-mentioned problems (1) and (2).
In this way, the heat efficiency is increased by inserting the heat transfer promoter into the radiant tube, but if the heat transfer promoter made of a heavy material is used, the deterioration of the radiant tube steel tube is accelerated and frequent replacement work is required. It occurs and causes high cost, and the heat response is slow, so the productivity of the steel production line is poor and it becomes difficult to actually introduce it.
As a result of diligent studies on the above-mentioned problems, the inventor of the present application can improve the deformation of the radiant tube and the thermal responsiveness of the radiant tube type heating device by reducing the bulk specific gravity of the heat transfer promoter. Then, they have found that it is possible to provide a heat transfer promoter having a small bulk specific density and high thermal efficiency by using a porous ceramic having a large number of pores as the heat transfer promoter.
Specifically, analysis and demonstration experiments on the heat flux of the inner wall of the radiant tube using heat transfer promoters of various shapes such as the surface shape of the heat transfer promoter, the number of fins, the twist angle of the spiral shape, and the cross-sectional shape. As a result, it was found that the amount of heat flux on the inner wall of the radiant tube changes due to the uneven shape and grooves on the outer peripheral surface of the heat transfer promoter, and the heat efficiency increases. It was found that it is possible to easily provide a heat transfer promoter having a small bulk specific gravity and high heat efficiency simply by adjusting the hole diameter.

Therefore, an object of the present invention is to efficiently transfer heat to the inner wall of the radiant tube for further energy saving effect, prevent deformation due to the weight of the entire radiant tube, and have excellent heat transfer responsiveness. And its manufacturing method .

The present invention relates to a heat transfer promoter made of porous ceramics, which is provided by connecting a plurality of pieces inside a radiant tube and having a plurality of fins provided on the outer periphery of a central axis .
The heat transfer accelerator is formed by sintering a large number of pores of different sizes using a mixture containing clay as a fireproof raw material and using a pore material or a foaming agent.
The air hole having a pore diameter of 0.1 to 10 mm and a small pore having a pore diameter smaller than that of the air hole are provided on the outer peripheral surface and the inside of the heat transfer promoter, and the air hole and the small pore are distributed throughout. Concavities and convexities are formed on the outer peripheral surface of the heat transfer promoter , and / or the arithmetic average roughness of the outer peripheral surface of the heat transfer promoter is formed to be 300 μm or more, and the silicon carbide (SiC) is used. It is a heat transfer promoter characterized in that a coating layer is uniformly applied to the entire outer peripheral surface of the unevenness with a thickness of 0.5 mm to 1.0 mm .
Since the amount of heat (heat capacity) required to raise the temperature of an object is obtained by multiplying the specific heat, mass, and rising temperature of the object, the heavier the mass, the more heat required to raise the temperature of the object. , The heat response is slowed down. Therefore, when a heat transfer promoter having the same volume is used inside the radiant tube, it is possible to improve the heat response by reducing the mass (bulk specific gravity) of the object.
Here, the "heat responsiveness" represents the speed at which the temperature of the heat transfer promoter goes from T1 to T2 when the ambient temperature of the heat transfer promoter is changed from T1 to T2.
If the bulk specific gravity of the heat transfer promoter is less than 0.2, a large number of pores are formed in the heat transfer promoter, which makes it fragile and rapidly deteriorates and wears easily in a heat treatment plant at high temperature. When the specific gravity is larger than 0.8, the heat transfer promoter becomes heavier, causing deformation of the radiant tube and slowing the heat response. With the current heat transfer promoter with a bulk specific density of 0.9, it is difficult to switch within a predetermined time because the heat response is slower as the operating conditions are switched more often. According to the present invention, by setting the bulk specific gravity of the heat transfer promoter to 0.2 or more and 0.8 or less, rapid deterioration, wear and deformation of the radiant tube are prevented, and a heat transfer promoter having a fast heat response is provided. It will be possible to provide.

The present invention has an air hole having a pore diameter of 0.1 to 10 mm and a small pore having a pore diameter smaller than that of the air hole on the outer peripheral surface and the inside of the heat transfer promoter, and the air hole and the small pore are the whole. It is characterized in that unevenness is formed on the outer peripheral surface of the heat transfer promoter.
Conventionally, the porosity of the porous ceramics used as the heat transfer promoter is determined in consideration of the weight and durability of the heat transfer promoter, and the heat transfer promoter is formed in consideration of the pore diameter of the pores. There was no point of view.
The applicant of the present application pays attention to the pore diameter of the pores, and by forming pores on the outer peripheral surface and inside of the heat transfer promoter, the heat transfer promoter of the present invention is lightweight and promotes turbulence of combustion gas. Invented that it is possible to do.
According to the present invention, the heat transfer promoter is formed because a large number of air holes having a pore diameter of 0.1 to 10 mm and small pores having a pore diameter smaller than the air holes are formed on the outer peripheral surface and the inside of the heat transfer promoter. It is possible to provide a radiant tube type heating device having excellent heat responsiveness by reducing the weight and preventing deformation of the entire radiant tube due to its own weight.
Further, according to the present invention, since the atmospheric pores and the small pores having different pore diameters are distributed and formed on the entire outer peripheral surface of the heat transfer promoter, a large number of irregularities are formed on the outer peripheral surface. The large number of irregularities on the outer peripheral surface promotes turbulent flow of combustion gas inside the radiant tube, and the amount of heat flux on the inner wall of the radiant tube changes, so that the thermal efficiency of the radiant tube type heating device can be improved.
If the pore diameter of the air hole is smaller than 0.1 mm, the turbulent flow effect of the combustion gas due to the unevenness of the outer peripheral surface becomes small, and the thermal efficiency cannot be sufficiently increased. On the other hand, if the pore diameter of the air hole is larger than 10 mm, the strength of the heat transfer promoter itself becomes small, and the fins are easily chipped or worn when the heat transfer promoter is used. By setting the pore diameter of the air pores to 0.1 to 10 mm, it is possible to provide a heat transfer promoter having excellent durability and thermal efficiency.
Further, according to the present invention, by forming the heat transfer promoter with porous ceramics, it is possible to easily form air pores and small pores on the outer peripheral surface and inside of the heat transfer promoter, and promote heat transfer. It is possible to easily realize the two effects of weight reduction of the body and improvement of heat efficiency due to the unevenness of the outer peripheral surface of the heat transfer promoter, and the heat transfer promoter has excellent workability and low cost, and can be delivered and replaced. It is easy and it is possible to reduce the manufacturing cost of the heat transfer promoter.

The heat transfer promoter of the present invention is characterized in that the arithmetic average roughness of the outer peripheral surface is 300 μm or more.
Here, the arithmetic average roughness Ra is a parameter representing the surface roughness of each portion extracted from the surface of the object, and only the reference length is extracted from the roughness curve in the direction of the average line, and the extracted portion is When the X-axis is taken in the direction of the average line and the Y-axis is taken in the direction of the vertical magnification, and the roughness curve is expressed by y = f (x), the value obtained by (Equation 1) is in micrometer (μm). Represented.

The larger the arithmetic mean roughness Ra, the wider the width of the height of the unevenness in the vertical direction with respect to the outer peripheral surface of the heat transfer promoter, the more turbulent flow of the combustion gas is promoted, and the combustion efficiency is improved.
According to the present invention, since the arithmetic mean roughness of the outer peripheral surface is 300 μm or more, the depth of the pores formed on the outer peripheral surface becomes deeper, more combustion gas enters the pores, and turbulence is generated for combustion. Efficiency is improved.

In the heat transfer promoter of the present invention, grooves are formed radially from the center of the heat transfer promoter toward the tip of the fin on the outer peripheral surface of the heat transfer promoter, and the width of the groove is set at the tip of the fin. It is characterized in that it is gradually formed larger toward the end.
According to the present invention, since grooves are formed radially from the center of the heat transfer promoter toward the tip of the fin on the outer peripheral surface of the heat transfer promoter, heat transfer promotion is promoted inside the radiant tube. The combustion gas collides with a large number of irregularities formed on the outer peripheral surface of the body and grooves formed on the outer peripheral surface, further generating turbulent flow of the combustion gas, and improving thermal efficiency.

Further, the heat transfer promoter of the present invention is characterized in that the plurality of fins form a spiral heat transfer path on the outer peripheral surface of the heat transfer promoter.
According to the present invention, since the heat transfer path is spirally formed in the heat transfer promoter, the heat of the combustion gas can be efficiently transferred to the inner wall of the radiant tube, and further energy saving effect can be achieved. It becomes.

The heat transfer promoter of the present invention is characterized in that the twist angle of the fin is 30 degrees to 150 degrees.
According to the present invention, the heat transfer promoter is in a state where the shape of the bottom surface of the heat transfer promoter is rotated by 30 to 150 degrees with respect to the shape of the top surface (twisting angle 30) about the Z axis (central axis). It was found that the turbulent flow of the combustion gas was effectively generated and the thermal efficiency was improved when the spiral shape was formed so as to be (degree to 150 degrees).
Depending on the size and ambient temperature of the tube, the device configuration of the radiant tube tube type heating device and the radiant tube type heat exchanger (presence or absence of a suction device provided around the combustion gas outlet 7, etc.), the twist angle can be set to 30 degrees to 150 degrees. It can be selected as appropriate within the range of degree.

Further, the present invention is a method for arranging a heat transfer promoter made of porous ceramics provided in a radiant tube and having a plurality of fins, wherein the heat transfer promoter has a bulk specific gravity of 0.2 or more and 0.8 or less. Is characterized in that the plurality of fins spirally and continuously form a heat transfer path and are arranged in the radiant tube.
According to the present invention, by arranging a plurality of heat transfer promoters in which a large number of pores of different sizes are formed in the downstream position in the pipe which is the flow path of the combustion gas, it is appropriate on the downstream side where the temperature of the combustion gas becomes low. It is possible to generate a turbulent flow in the pipe and transfer a sufficient amount of heat to the pipe even on the downstream side in the pipe.

The present invention is characterized in that heat transfer promoters having different twist angles of the fins are arranged so that the heat transfer paths form a continuous spiral shape.
Further, according to the present invention, in a radiant tube type heating device or a radiant tube type heat exchanger in which a plurality of heat transfer promoters are arranged, the heat transfer promoters are arranged so that the plurality of fins are continuously arranged. It is characterized by that.
The present invention is characterized in that, in a radiant tube type heating device or a radiant tube type heat exchanger provided with a heat transfer promoter, a plurality of the heat transfer promoters having different twist angles are arranged.
Here, the "twisting angle" refers to the axis perpendicular to the upper surface and the bottom surface of the heat transfer promoter and passing through the center of the cross section of the heat transfer promoter as the Z axis (central axis), and the heat transfer is centered on the Z axis. It is a measure of how many times the shape of the bottom surface of the heat promoter rotates with respect to the shape of the top surface, and how many times the spiral shape rotates about the Z axis from the top surface to the bottom surface. It is a measure to represent.
For example, a heat transfer promoter with a small twist angle is placed on the upstream side that first receives the combustion gas in the radiant tube, and a heat transfer promoter with a large twist angle is placed toward the downstream side. By connecting a plurality of heat promoters, the residence time of the combustion gas is changed between the upstream side and the downstream side in the radiant tube. The upstream side where the temperature of the combustion gas is high has a short residence time of the combustion gas, and the downstream side where the temperature of the combustion gas is low has a long residence time of the combustion gas. The amount of heat transferred to is made uniform, and it becomes possible to efficiently transfer heat to the entire radiant tube.
Further, in order to appropriately generate turbulence in the radiant tube, a heat transfer promoter having a small twist angle and a heat transfer promoter having a large twist angle may be arranged discontinuously.
As described above, according to the present invention, the heat transfer path is spirally formed in the heat transfer promoter, so that the heat of the combustion gas is efficiently transferred to the inner wall of the radiant tube, and the pores of the heat transfer promoter are formed. In addition to the turbulent flow effect due to the above, it is possible to further improve the thermal efficiency and save energy.
When a heat transfer promoter is placed inside the radiant tube heat exchanger, the heat transfer promoter is made by flowing a fluid for heat exchange such as combustion gas or liquid in the tube of the radiant tube heat exchanger. The heat exchanges with the fluid, but by changing the residence time of the fluid in the pipe between the upstream side and the downstream side, it becomes possible to efficiently transfer heat from the heat transfer promoter to the fluid.
Further, according to the present invention, by connecting a plurality of heat transfer promoters having different twist angles, it is possible to transfer heat as a whole without locally transferring high heat to a part of the tubular tube. This makes it possible to reduce the occurrence of distortion and breakage of the radiant tube, and it becomes possible to efficiently transfer heat.
Since the heat transfer promoter is formed in a small size that can be divided, it is easy to store and transport.
In addition, since the fins have a continuous spiral shape, the heat of the combustion gas is efficiently transferred, but even if they are arranged at predetermined intervals (for example, at intervals of one or less), the heat transfer effect is achieved. Will not be lost.

The heat transfer promoter of the present invention is characterized in that the number of fins is 3 to 12.
According to computer analysis, in order to obtain high heat transfer efficiency, the number of fins forming the heat transfer path of the heat transfer promoter is preferably 3 to 12, and more preferably 4 or more. I found it good.
According to the present invention, by setting the number of fins of the heat transfer promoter to 3 to 12, it is possible to provide a heat transfer promoter capable of efficiently transferring heat.

The heat transfer promoter of the present invention is characterized in that a coating layer of silicon carbide is formed on the entire outer peripheral surface of the heat transfer promoter by impregnation.
Further, the radiant tube type heating device or the radiant tube type heat exchanger of the present invention is characterized in that silicon carbide is uniformly applied to the entire inner wall surface and / or the entire outer wall surface.
According to the present invention, by applying silicon carbide (SiC) having a high infrared emissivity to the entire outer peripheral surface of the heat transfer promoter, or to the entire inner wall surface and / or outer wall surface of the tube, further axial heat transfer is performed. Can be increased.
Further, according to the present invention, since silicon carbide (SiC) is expensive, the present invention in which silicon carbide (SiC) is applied only to the outer peripheral surface as compared with the case where the entire heat transfer promoter is made of silicon carbide (SiC). The heat transfer promoter of the present invention can be formed at low cost, and the same axial heat transfer as in the case of using the heat transfer promoter in which the entire heat transfer promoter is formed of silicon carbide (SiC) can be obtained. Is possible.

The present invention is a heat transfer promoter made of porous ceramics, which is provided by connecting a plurality of heat transfer promoters inside a radiant tube. The heat transfer promoter uses a mixture containing clay as a fireproof raw material and uses a pore material or a foaming agent. A large number of pores of different sizes are formed by sintering, and the air pores having a pore diameter of 0.1 to 10 mm and small pores having a pore diameter smaller than those of the air pores are formed on the outer peripheral surface and inside of the heat transfer promoter. The atmosphere pores and the small pores are distributed throughout to form irregularities on the outer peripheral surface of the heat transfer promoter , and / or, or the arithmetic average roughness of the outer peripheral surface of the heat transfer promoter. Is a heat transfer promoter, which is formed to have a thickness of 300 μm or more and the silicon carbide (SiC) coating layer is uniformly applied to the entire outer peripheral surface of the uneven surface with a thickness of 0.5 mm to 1.0 mm. It is a manufacturing method of .
In order to form an atmospheric pore with a pore diameter of 0.1 to 10 mm on the outer peripheral surface of the heat transfer promoter, a pore material such as organic foam particles having a size corresponding to the pore diameter of the atmospheric pore is used as a raw material for the porous ceramics. It can be formed by mixing, molding and sintering. Further, a foaming agent may be used in the manufacturing process to form air pores by foaming at the time of firing.
Further, small pores having a pore diameter smaller than that of the atmospheric pores, for example, those having a pore diameter of about 1.0 μm can be formed by mixing sawdust or the like as a raw material for porous ceramics.
As described above, according to the present invention, the outer peripheral surface of the heat transfer promoter can be easily obtained by simply changing the material of the pore material, which is the raw material of the porous ceramics, the size of the pore material, or the amount of the foaming agent. It is possible to form pores of a desired size.

The plurality of heat transfer promoters of the present invention are characterized in that connecting means to be connected to each other are formed on the upper surface and the bottom surface, or are connected by an adhesive means.
In the present invention, by providing the connecting means and the adhesive means on the upper surface and the bottom surface of the heat transfer promoting body, it is possible to easily and accurately connect the heat transfer promoting bodies to each other when connecting the heat transfer promoting bodies. ..

According to the present invention, by adjusting the bulk specific gravity of the heat transfer promoter, it is possible to prevent deformation of the entire radiant tube due to its own weight and to provide a heat transfer promoter having excellent heat responsiveness.
Further, according to the present invention, a large number of irregularities are formed on the outer peripheral surface of the heat transfer promoter by the atmospheric pores and small pores having different pore diameters, and the unevenness (arithmetic mean roughness) of the outer peripheral surface is adjusted. The turbulent flow of combustion gas inside the radiant tube can be promoted, and the amount of heat flux on the inner wall of the radiant tube can be changed to increase the thermal efficiency of the radiant tube type heating device.
According to the present invention, by forming the heat transfer promoter with porous ceramics, it is possible to easily form air pores and small pores on the outer peripheral surface and inside of the heat transfer promoter, thereby promoting heat transfer. It is possible to easily realize the two effects of weight reduction of the body and improvement of heat efficiency due to the unevenness of the outer peripheral surface of the heat transfer promoter, and the heat transfer promoter has excellent workability and low cost, and can be delivered and replaced. It is easy and it is possible to reduce the manufacturing cost of the heat transfer promoter.
Further, according to the present invention, by arranging a heat transfer promoter inside the radiant tube heat exchanger, the radiant tube heat exchanger can efficiently transfer heat from the heat transfer promoter to the fluid. Can be provided.

It is a schematic diagram which shows the state which the heat transfer promotion body 10 which is 1st Embodiment of this invention is arranged in a radiant tube. It is a perspective view which shows the heat transfer promotion body 10 of the said embodiment. It is a top view which shows the heat transfer promotion body 10 of the said embodiment. It is a side view which shows the heat transfer promotion body 10 of the said embodiment. It is a perspective view which shows the state which connected three heat transfer promotion bodies 10 of the said embodiment. It is a microscope enlarged view (20 times) of the outer peripheral surface of the heat transfer promoter 10 of the said embodiment. It is a perspective view which shows the heat transfer promotion body 20 of the 2nd Embodiment of this invention. It is a schematic diagram which shows the state which three kinds of heat transfer promoters with different twist angles are connected and arranged in a radiant tube. It is a schematic photograph which shows the material of the heat transfer promotion body of this invention, (a) is the thing which did not form the film | coating layer on the material of a heat transfer promotion body, (b) is the thing that the film | coating layer is formed on the material of a heat transfer promotion body. It was formed. It is a flow chart which shows the flow of the manufacturing process of the heat transfer promoter of this invention. It is a graph which shows the average heat flux by the difference of the surface roughness when the heat transfer promoter of this invention is used. It is a graph which shows the heat responsiveness by the difference of the bulk specific density when the heat transfer promoter of this invention is used. It is a microscope magnified view (10 times) of the outer peripheral surface of the heat transfer promoter of (Example 1).

Specific embodiments to which the present invention is applied will be described in detail below with reference to the drawings.

(First Embodiment)
FIG. 1 is a schematic view showing a state in which the heat transfer promoter 10 according to the first embodiment of the present invention is arranged in a radiant tube. FIG. 5 is a perspective view showing a state in which three heat transfer promoters 10 of the above embodiment are connected.

The radiant tube type heating device (radiant tube heater) installed in a heat treatment plant such as a metal annealing furnace is provided at the radiant tube 4 attached to the furnace wall 5 and the inflow port 8 (upstream side) of the radiant tube 4. It is composed of a member such as a connected heat transfer promoter 100 connected and arranged in the latter half (downstream side) of the radiant tube 4 and the burner 3 (FIG. 1).
Combustion gas 6 from the burner 3 arranged in the radiant tube 4 flows from the inlet 8 of the radiant tube 4 toward the outlet 7 to heat the radiant tube 4 and from the surface of the radiant tube 4. Heat treatment of objects to be heated such as steel plates is performed by radiant heat.
The radiant tube 4 may have a shape such as a U type, a straight type, an L type, a T type, a W type, or an O type. Even if the shape of the radiant tube 4 is different, the connected heat transfer promoter 100 is arranged in the latter half of the radiant tube 4 (on the outlet 7 side of the combustion gas 6). By arranging as described above, heat is efficiently transferred without reducing the heat flux of the inner wall of the radiant tube 4 even in the latter half of the radiant tube 4 where the temperature of the combustion gas 6 begins to decrease. It becomes possible.

The connected heat transfer promoter 100 is for promoting heat transfer to the wall surface of the radiant tube 4, and is formed by connecting a plurality of heat transfer promoters 10 (FIG. 5) in the radiant tube 4. Be placed. The number of connected heat transfer promoters 10 is about 10 to 17, but it can be appropriately changed depending on the length of the straight tube portion of the radiant tube 4.
Further, in the process of forming the connected heat transfer promoter 100, when the heat transfer promoters 10 are connected to each other, the fins 2 of the heat transfer promoter 10 are joined together and the outer surface of the fins 2 is joined. Join so as to form a continuous spiral shape. By joining the heat transfer promoter 10 as described above, a plurality of spiral passages (heat) for the combustion gas 6 to flow when the connected heat transfer promoter 100 is arranged in the radiant tube 4. A transmission path) 14 is formed, the flow velocity around the inner wall of the radiant tube 4 of the combustion gas 6 increases, and the combustion gas 6 rotates in the radiant tube 4 to cause a high temperature center of the radiant tube 4. Heat exchange between the shaft and the wall surface of the radiant tube 4 at a low temperature is promoted, heat can be efficiently transferred even in the latter half of the radiant tube 4, and a high energy saving effect is produced.
When the heat transfer promoters 10 are connected to each other to form the connected heat transfer promoter 100, the upper and lower surfaces of the heat transfer promoter 1 are simply combined in the radiant tube without using connecting means or adhesive means. In some cases, the connected heat transfer promoter 100 may be formed one by one, or the connected heat transfer promoter 100 may be formed by using a connecting means or an adhesive means described later. Further, the heat transfer promoters 10 may not be connected to each other and may be arranged at predetermined intervals (for example, arrangement at a distance of one interval or less).

FIG. 2 is a perspective view showing the heat transfer promoter 10 of the above embodiment. FIG. 3 is a plan view showing the heat transfer promoter 10 of the embodiment, and FIG. 4 is a side view showing the heat transfer promoter 10 of the embodiment.
The heat transfer promoter 10 is a constituent member of the connected heat transfer promoter 100, and the cross section of the heat transfer promoter 10 has a cross-shaped shape and has four fins 2, 2, ... Radially extending from the center. 2 and 3). The fins 2, 2, ... Have the same shape, and the adjacent fins 2, 2, ... Are attached to the central axis 9 of the heat transfer promoter 10 at an angle of 90 degrees.
On the outer peripheral surface and the inside of the heat transfer promoter 10, a large number of atmospheric pores 1a having a pore diameter of 0.1 to 10 mm and a large number of small pores 1b having a pore diameter smaller than that of the atmospheric pores, which will be described later, are formed. And the small pores 1b are distributed throughout and form irregularities on the outer peripheral surface of the heat transfer promoter 10.
The planar shape of the fins 2, 2 ... Is a tapered shape in which the width gradually narrows from the central axis 9 of the heat transfer promoter 10 toward the tips 2a, 2a ... of the fins 2, 2 ... Yes, the cross-sectional shape around the tips 2a, 2a ... is a gentle arc shape. Further, when considering the cross section of the heat transfer promoting body 10, the tips 2a, 2a.・ Is located.
The fins 2, 2, ... Are formed in a gentle spiral shape clockwise around the Z axis (central axis) that passes through the center point 9a and is perpendicular to the upper surface 11 and the bottom surface 13 (FIGS. 2 and 4). In the embodiment, the shape of the bottom surface 13 of the heat transfer promoter 10 is rotated 60 degrees with respect to the shape of the top surface 11 (twisting angle 60 degrees) about the Z axis (central axis). It is formed. Therefore, the fins 2, 2 ... Form four spiral passages (heat transfer paths) 14, 14 ... For the combustion gas 6 to flow around the central axis.
The material of the heat transfer promoter 10 is lightweight porous ceramics, which is lightweight, has excellent workability, and is low in cost. Therefore, the heat transfer promoter 10 can be easily delivered and replaced, and the heat transfer promoter 10 can be easily delivered and replaced. It is possible to reduce the manufacturing cost of.
The distance (height) H in the Z-axis direction from the bottom surface 13 to the top surface 11 is 106 mm (mostly 100 to 110 mm), centered on the center point (central axis) 9a of the heat transfer promoter 10. The outer diameters R (2r) are 146 mm, 170 mm, and 158 mm. The width W in the cross section of the fins 2, 2 ... Is 25 mm. The distance (height) H, outer diameter R (2r), and width W in the Z-axis direction from the bottom surface 13 to the top surface 11 can be appropriately changed depending on the inner diameter and length of the radiant tube to be introduced. The distance (height) H in the Z-axis direction from the bottom surface 13 of the heat transfer promoter 1 to the top surface 11 is 106 mm, but when two are connected, the H becomes 212 mm and three are connected. When it becomes 324 mm.
Concavo-convex portions (connecting means) (not shown) for connecting the heat transfer promoting bodies 10 to each other may be provided on the central axes of the upper surface 11 and the bottom surface 13. By providing a concave portion on the upper surface 11 and a convex portion on the bottom surface 13, or by providing a convex portion on the upper surface 11 and a concave portion on the bottom surface 13, the concave portion is formed when the connected heat transfer promoter 100 is formed. By fitting the convex portions, the heat transfer promoters 1 can be easily and accurately connected to each other.
Further, when the heat transfer promoters 10 are connected to each other, they may be connected by an adhesive means such as an adhesive.

(Pores of heat transfer promoter 10)
FIG. 6 is a microscope enlarged view (20 times) of the outer peripheral surface of the heat transfer promoter 10 of the above embodiment. FIG. 6 is a photograph of the outer peripheral surface of the heat transfer promoter 10 magnified 20 times with a microscope, and is an example of the heat transfer promoter.
The heat transfer accelerator 10 is obtained by molding a mixture containing clay and sintering it to obtain a sintered body of porous ceramics, and grinding the surface of the sintered body of the porous ceramics. Pore (atmospheric pores 1a and small pores 1b) are formed on the outer peripheral surface and inside.
The sizes of the air pores 1a and the small pores 1b can be determined in consideration of the weight reduction of the heat transfer promoter and the uneven shape of the outer peripheral surface of the heat transfer promoter, specifically, the pore diameter is 0.1 to 10 mm. It is formed by mixing an air hole 1a on the order of millimeters and a small pore 1b on the order of micrometer with a hole diameter of less than 0.1 mm. The pore diameter refers to a long pore, and the pore diameter can be adjusted by using a pore material or a foaming agent having a size corresponding to the pore diameter.
As a method for measuring the pore diameter, the upper surface 11 and the bottom surface 13 of the heat transfer promoter are surface-observed and measured using an optical microscope or an electron microscope.
By combining a plurality of pores having different pore diameters in this way to form discontinuous irregularities on the outer peripheral surface of the heat transfer promoter 10, turbulent flow of combustion gas is generated inside the radiant tube, and the radiant tube type heating device is used. It is possible to improve the thermal efficiency of.
The pores formed in the heat transfer promoter 10 may be independent or may be communication holes that communicate with each other.

(Relative density of heat transfer promoter 10)
The specific gravity of the porous ceramics of the heat transfer promoter 10 can be determined in consideration of heat responsiveness and strength.
Here, "specific gravity" is expressed by the ratio of the mass (g) of the porous ceramics to the volume (cm ³ ) of the porous ceramics, and the mass (g) of the porous ceramics / the volume of the porous ceramics (cm ³ ). The value is preferably 0.2 or more and 0.8 or less. When the specific gravity of the heat transfer promoting body 10 is smaller than 0.2, a large number of pores are formed inside the heat transfer promoting body 10 to make it brittle, and it becomes easy to rapidly deteriorate and wear in a heat treatment plant at a high temperature. On the other hand, when the specific gravity is larger than 0.8, the heat transfer promoter 10 becomes heavier, causing deformation of the radiant tube and slowing the heat response. Therefore, according to the present invention, by setting the specific gravity of the heat transfer promoter to 0.2 or more and 0.8 or less, rapid deterioration, wear and deformation of the radiant tube are prevented, and the heat transfer promoter has a fast heat response. Can be provided.

(Arithmetic mean roughness of heat transfer promoter 10)
Further, the porous ceramics of the heat transfer promoter 10 have an arithmetic average roughness Ra of the outer peripheral surface of 300 μm or more.
When the arithmetic mean roughness Ra is large, the width of the height of the unevenness in the vertical direction with respect to the outer peripheral surface of the heat transfer promoter becomes large, the generation of turbulent flow of combustion gas is promoted, and the combustion efficiency is improved.
By forming the arithmetic mean roughness of the outer peripheral surface of the heat transfer promoter 10 to 300 μm or more, the depth of the pores formed on the outer peripheral surface becomes deeper, and the combustion gas enters the pores more to generate turbulence. The combustion efficiency is improved.

Since the air holes 1a and the small pores 1b are formed inside the heat transfer promoter 10 in this way, the heat transfer promoter 10 is lightened, the entire radiant tube is prevented from being deformed by its own weight, and the heat response is excellent. It becomes possible to provide a radiant tube type heating device.
Furthermore, since atmospheric pores and small pores with different pore diameters are distributed and formed on the outer peripheral surface of the heat transfer promoter, many irregularities are formed on the outer peripheral surface, and the irregularities cause turbulent flow of combustion gas inside the radiant tube. It is generated and the amount of heat flux on the inner wall of the radiant tube is changed, so that the thermal efficiency of the radiant tube type heating device can be improved.
Further, even in a place where the temperature of the combustion gas 6 from the latter half of the radiant tube 4 to the outlet 7 of the radiant tube 4 becomes low inside the radiant tube 4, the spiral passage (heat transfer path) 14, As a result, the flow velocity around the inner wall of the radiant tube 4 of the combustion gas 6 increases, and the combustion gas 6 rotates in the radiant tube 4, so that the central axis of the radiant tube 4 at a high temperature and the temperature at a low temperature are low. Heat exchange with the wall surface of the radiant tube 4 is promoted, heat can be efficiently transferred, and a high energy saving effect can be produced.

The heat transfer promoting body 10 of the present embodiment is in a state where the shape of the bottom surface 13 of the heat transfer promoting body 10 is rotated by 60 degrees with respect to the shape of the upper surface 11 (twisting angle 60) about the Z axis (central axis). It was formed in a spiral shape so as to be (degree), but the size and ambient temperature of the radiant tube, the device configuration of the radiant tube tube type heating device (presence or absence of a suction device provided around the outlet 7 of the combustion gas, etc.) The twist angle can be appropriately selected in the range of 30 degrees to 150 degrees.
Further, although the number of fins of the heat transfer promoter 10 of the present embodiment was 4, it is preferable that the number of fins is in the range of 3 to 12 in order to obtain high heat transfer efficiency, and the fins are appropriately selected depending on the application. It is possible.

FIG. 8 is a schematic view showing a state in which three types of heat transfer promoters having different twist angles are connected and arranged in a radiant tube.
The linked heat transfer promoter 100 of the present embodiment was formed by connecting a plurality of heat transfer promoters 10, but the linked heat transfer promoters 200 were combined with the heat transfer promoters 1, 10 and 20 having different twist angles. It may be mixed and formed.
Twisting, such as arranging the heat transfer promoter 1 with a small twist angle on the upstream side that first receives the combustion gas 6 in the radiant tube 4, and arranging the heat transfer promoters 10 and 20 with a large twist angle toward the downstream side. By connecting a plurality of heat transfer promoters having different angles, the residence time of the combustion gas 6 is changed between the upstream side and the downstream side in the radiant tube. Since the residence time of the combustion gas 6 is short on the upstream side where the temperature of the combustion gas 6 is high, and the residence time of the combustion gas 6 is long on the downstream side where the temperature of the combustion gas 6 is low, it is transmitted to the upstream side of the radiant tube 4. The amount of heat and the amount of heat transferred to the downstream side are made uniform, and heat can be efficiently transferred to the entire radiant tube 4.

Although the heat transfer promoter 10 of the embodiment is made of porous ceramics, it is also possible to uniformly apply silicon carbide (SiC) to the entire outer peripheral surface of the porous ceramics.
In this case, silicon carbide (SiC) having a high infrared emissivity is uniformly applied to the entire outer peripheral surface to a heat transfer promoter made of porous ceramics to a thickness of 0.5 mm to 1.0 mm. The coating layer 81 is formed. Regarding the method of applying silicon carbide (SiC), heat transfer before coating silicon carbide (SiC) in a silicon carbide (SiC) mixed solution 82 in which an inorganic binder is dissolved in water and a powder of silicon carbide (SiC) is mixed. A method of impregnating the accelerator 10 to form a coating layer 81 (immersion coating method), a method of spray-applying the silicon carbide (SiC) mixed solution to the heat transfer accelerator before coating (spray coating method), and a curtain. Various methods such as flow coater coating, roller coater coating, and manual coating (brush coating, roller brush coating, etc.) can be used.
Further, it is also possible to uniformly apply silicon carbide to the entire inner wall surface and / or the entire outer wall surface of the radiant tube 4 provided in the radiant tube type heating device (radiant tube heater).
In this way, the heat transfer promoter is formed into a spiral shape and the outer peripheral surface is provided with irregularities to greatly improve the heat transfer efficiency, and silicon carbide (SiC) having a high infrared emissivity is applied to the outer peripheral surface. Further, it is possible to further increase the axial emissivity of the heat transfer promoter, and it is possible to obtain the same effect at a much lower cost than forming the entire heat transfer promoter with silicon carbide.
Then, by applying silicon carbide (SiC) having a high infrared emissivity to the entire inner wall surface and / or the outer wall surface of the radiant tube, axial radiant heat from the inner wall surface and / or the outer wall surface of the radiant tube is increased. This makes it possible to manufacture the entire radiant tube at a much lower cost than forming the entire radiant tube from silicon carbide.

(Manufacturing method of heat transfer promoter 10)
FIG. 10 is a flow chart showing the flow of the manufacturing process of the heat transfer promoter of the present invention.
The method for producing the heat transfer promoter 10 of the present invention is a step of obtaining a mixture containing clay (mixing step), a step of molding the mixture to obtain a molded body (molding step), and a step of sintering the molded body. It is provided with a step of obtaining a porous ceramics sintered body (firing step) and a step of performing a finishing process of the porous ceramics sintered body (finishing process).

<Mixing process>
The mixing step is a step of appropriately mixing a fireproof raw material, a foaming agent, a pore material, a filler, an aggregate and the like to obtain a mixture.

(Fireproof raw material)
The fireproof raw material is a mineral material having a clay-like property that is generally used as a raw material for ceramics. As the fireproof raw material, known materials used for porous ceramic sintered bodies can be used, and they are composed of mineral compositions such as quartz, feldspar, and clay, and the constituent minerals are mainly kaolinite, halloysite, and the like. Those containing montmorillonite, illite, and alumina are preferable.

(Effervescent agent)
The foaming agent foams at the time of firing, and for example, known foaming agents for ceramics such as calcium carbonate, silicon carbide, magnesium carbonate, and slag can be used. Among these foaming agents, slag is preferable.
The slag is not particularly limited, and is, for example, blast furnace slag generated during metal refining, urban waste molten slag generated when urban waste is melted, sewage sludge molten slag generated when sewage sludge is melted, and cast iron such as ductile cast iron. Examples thereof include glassy slag such as cast iron slag. Of these, cast iron slag is more preferred. Since the composition of cast iron slag is stable, a stable foaming state can be obtained, and the foaming rate is about 1.5 to 2 times that of other slags. By using cast iron slag, large pores on the order of millimeters can be formed in the porous ceramics.
The blending amount of the foaming agent in the mixture is appropriately determined in consideration of the porosity of the porous ceramics and the pore diameters of the air pores and small pores.

(Stomata)
The pore material contains an organic substance as a main component. By using organic foam particles, wood chips, etc., air pores and small pores are formed in the porous ceramics.
By appropriately selecting the size of the organic foam particles to be used, it is possible to adjust the pore diameters of the air pores and the small pores.

(Filler)
Examples of the filler include inorganic fibers and rock wool. For example, sintering a mixture containing inorganic fibers as a filler makes it resistant to thermal shock, has low thermal conductivity, and can withstand complex shapes.

(aggregate)
Aggregates include, for example, pottery, porcelain material, alumina, chamotte, forsterite, cordierite, zeolite, hydrotalcite, montmorillonite, sepiolite, zirconia, fluorinated fiber, silicon carbide, calcium phosphate, hydroxyapatite, and heat resistant. Use powdered glass fiber, rock wool, aluminosilicate fiber, alumina fiber, etc., which are sex fibers.

The mixing device is not particularly limited, and a conventionally known mixing device can be used, and the mixing time in the mixing step is set so that the mixture is in a plastic state in consideration of the mixing ratio of each raw material and the like. To.
The temperature conditions in the mixing step are appropriately determined in consideration of the mixing ratio of each raw material and the like.

<Molding process>
The molding step is a step of molding the mixture obtained in the mixing step into an arbitrary shape. The molding method is appropriately determined according to the shape of the heat transfer promoter 10. For example, a method of continuously obtaining a molded body of an arbitrary shape using a molding device, or a method of continuously filling a mixture into a mold of an arbitrary shape and forming a molded body. A method of obtaining a molded product, a method of stretching or rolling a mixture, and a method of cutting the mixture into an arbitrary shape to obtain a molded product can be mentioned.
Examples of the molding apparatus include an earth kneading machine, a press molding machine, a pouring molding machine and the like.

<Baking process>
The firing step is a step of firing the molded body obtained in the molding step to obtain a porous ceramic sintered body. Examples of the firing step include a method of drying the molded body (drying operation), firing the dried molded body (baking operation), and sintering clay to obtain a porous ceramic sintered body.
The firing temperature (reached temperature) is determined in consideration of the type of arbitrary component, the mixing ratio of the raw material, and the like.

<Finishing process>
The finishing process is a process for commercializing the porous ceramic sintered body obtained in the firing process.

According to the present invention, by forming the heat transfer promoter with porous ceramics, air pores and small pores can be easily formed on the outer peripheral surface and the inside of the heat transfer promoter, and the heat transfer promoter can be easily formed. It is possible to easily realize the two effects of weight reduction and improvement of heat efficiency due to the unevenness of the outer peripheral surface of the heat transfer promoter, and the heat transfer promoter has excellent workability and low cost, and is easy to deliver and replace. Moreover, it is possible to reduce the manufacturing cost.

(Second embodiment)
FIG. 7 is a perspective view showing a heat transfer promoter 20 according to a second embodiment of the present invention.
The heat transfer promoter 20 of the second embodiment of the present invention has a plurality of grooves 2b, 2b formed along the outer surface of the fins 2, 2 of the heat transfer promoter 10 of the first embodiment. Since the other configurations are the same as those of the first embodiment, the same parts are designated by the same reference numerals and duplicated description will be omitted.
The heat transfer promoter 20 according to the second embodiment of the present invention has long grooves 2b, 2b radially extending from the center of the heat transfer promoter 20 toward the tip of the fin on the outer surface of the fins 2, 2. Multiple are formed.
The widths of the grooves 2b and 2b are gradually increased toward the tips of the fins 2 and 2.
Further, although the grooves 2b and 2b are provided, centrifugal force is applied to the combustion gas 6 when it is formed on both side surfaces of the fins 2 and 2 or when the combustion gas 6 flows along the heat transfer path 14. It may be formed only on the side surface of the fin on the side where it works and collides.
Since the grooves 2b and 2b are formed on the side surfaces of the fins 2 and 2 of the heat transfer promoter 20 where the combustion gas 6 easily collides, it is possible to promote the generation of turbulent flow of the combustion gas 6 and improve the thermal efficiency. Will be.
The number of grooves 2b and 2b can be appropriately selected in consideration of thermal efficiency.

In the embodiment, the example in which the heat transfer promoter is arranged in the radiant tube of the radiant tube type heating device has been described, but it is also possible to arrange the heat transfer promoter inside the radiant tube type heat exchanger. be.
In that case, a radiant tube type heat exchanger in which the heat transfer promoter of the present invention is inserted in the pipe is used, and a fluid for heat exchange such as combustion gas or liquid is flowed in the pipe to promote the heat transfer. And the fluid can efficiently exchange heat.

図１３は、（実施例１）の伝熱促進体の外周表面の顕微鏡拡大図（１０倍）である。
（表１）に示す組成で、耐火原料、気孔材、骨材および水を混合し、混合物を得て（混合工程）、混合物を伝熱促進体の形状に成形した（成形工程）。
その後、得られた成形体を乾燥させ、焼結炉を用いて焼成した（焼成工程）。そして、焼成工程で得られたセラミックス焼結体を砥石加工することで、伝熱促進体を得た。
得られた伝熱促進体について、カサ比重、算術平均粗さを測定し、その結果を（表２）に示した。
気孔径に関しては、得られた伝熱促進体の外周表面を拡大して撮影した画像を用いて、画像内に存在する気孔に着色を施し、目視にて気孔径１ｍｍ以上の気孔をカウントし、気孔径が１－２ｍｍ、２－３ｍｍ、３－４ｍｍ、４－５ｍｍ、５－６ｍｍおよび６－７ｍｍの間に存在する気孔の数の割合（％）、および平均径（ｍｍ）を算出した。ここで、気孔径１ｍｍ未満の気孔はカウントしていない。結果を（表３）に示す。また、伝熱促進体の外周表面を顕微鏡で１０倍に拡大して撮影を行った結果を図１３に示した。
図１３、（表２）、（表３）に示されるとおり、耐火原料、発泡剤、気孔材、フィラー、骨材等の材料を適宜選択することにより、外周表面に気孔を備えた伝熱促進体を得ることができる。 (Example 1)

FIG. 13 is a microscope enlarged view (10 times) of the outer peripheral surface of the heat transfer promoter of (Example 1).
With the composition shown in (Table 1), a fireproof raw material, a pore material, an aggregate and water were mixed to obtain a mixture (mixing step), and the mixture was molded into the shape of a heat transfer promoter (molding step).
Then, the obtained molded product was dried and fired in a sintering furnace (firing step). Then, the ceramic sintered body obtained in the firing step was grindstone-processed to obtain a heat transfer promoter.
For the obtained heat transfer promoter, the bulk specific gravity and the arithmetic mean roughness were measured, and the results are shown in (Table 2).
Regarding the pore diameter, the pores existing in the image are colored by using the image taken by enlarging the outer peripheral surface of the obtained heat transfer promoter, and the pores having a pore diameter of 1 mm or more are visually counted. , Percentage (%) of the number of pores with pore diameters between 1-2 mm, 2-3 mm, 3-4 mm, 4-5 mm, 5-6 mm and 6-7 mm, and average diameter (mm) were calculated. .. Here, pores having a pore diameter of less than 1 mm are not counted. The results are shown in (Table 3). Further, FIG. 13 shows the results of photographing the outer peripheral surface of the heat transfer promoter by magnifying it 10 times with a microscope.
As shown in FIGS. 13, (Table 2) and (Table 3), heat transfer having pores on the outer peripheral surface is provided by appropriately selecting materials such as fireproof raw materials, foaming agents, pore materials, fillers and aggregates. You can get a promoter.

(Example 2)
9A and 9B are schematic photographs showing the material of the heat transfer promoter of the present invention, in which FIG. 9A is a material having no coating layer formed on the material of the heat transfer promoter, and FIG. 9B is a material of the heat transfer promoter. A film layer is formed on the surface.
As the material of the heat transfer promoter, a white mullite lightweight refractory fired at 1550 ° C. is used, and silicon carbide (SiC) having a high infrared emissivity is uniformly applied to the outer peripheral surface of the heat transfer promoter. By applying to a thickness of 0.5 mm to 1.0 mm, a coating layer was formed, and a heat transfer promoter with a coating was formed (FIG. 9 (b)). Using the heat transfer promoter with a coating (FIG. 9 (b)) and the heat transfer promoter without a coating (FIG. 9 (a)), the difference in infrared emissivity depending on the presence or absence of a coating due to silicon carbide (SiC) can be seen. It was measured.

(measuring device)
The measuring device for measuring the infrared emissivity is an FIR device (PerkinElmer, System2000 type), the integrating sphere is Labspher, RSA-PE-200-ID, and the inside of the sphere is coated with gold. There is. Further, the incident diameter of the integrating sphere is Φ16 mm, and the diameter of the measuring unit is Φ24 mm.
(Measurement condition)
The measurement area is 370 to 7800 cm ^-1 (effective range 400 to 6000 cm ^-1 ), the number of integrations is 200, the light source is MIR, and the detector is MIR-TGS. The resolution was 16 cm ^-1 , and the beam splitter used optimized KBr. The optical path from the light source to the detector was filled with _N2 gas and purged.
(Measurement method)
The reflection spectrum was measured at room temperature, and the total emissivity at the specified temperature (25 ° C, 500 ° C, 950 ° C, 1000 ° C) was calculated from the obtained data. The measurement is based on JIS R 1693-2: 2012.

It can be seen that in the case of the heat transfer promoter without a film, the spectral emissivity is small, but in the case of the heat transfer promoter with a film, the spectral emissivity in the entire wavelength region is large.
In addition, in the temperature range of 950 ° C to 1000 ° C, where the heat transfer promoter is exposed to combustion gas during operation, the emissivity of the heat transfer promoter with a film shows a high emissivity close to 90% of blackbody radiation. found.
This means that the heat transfer promoter with a film has a radiant heat transfer effect of transferring twice the radiant heat from the inside of the tube to the tube in the temperature range of 950 ° C to 1000 ° C.
This makes it possible to utilize the high infrared emissivity of silicon carbide (SiC) at a dramatically lower cost than when the entire heat transfer promoter is made of silicon carbide (SiC).

(Example 3)
FIG. 11 is a graph showing the average heat flux due to the difference in surface roughness when the heat transfer promoter of the present invention is used.
In the embodiment, detailed data such as the temperature and flow velocity of the combustion gas are input and fluid analysis is performed by computer simulation. Specifically, the surface roughness of the heat transfer promoter is changed to 200 μm, 300 μm, 450 μm, and 700 μm. The average heat flux (W / m ² ) at the outer wall of the radiant tube was calculated.
The calculation result is shown in FIG.

(Calculation condition)
The radiant tube used for the fluid analysis was assumed to be a linear structural steel pipe having a density of 7850 (Kg / m ³ ), a specific heat of 434 (J / kgK), and a thermal conductivity of 60.5 (W / mK).
Although it is the air inside the pipe used for fluid analysis, considering compressibility, it has a density of 1.226 (Kg / m ³ ), a constant pressure specific heat of 1006 (J / kgK), and a thermal conductivity of 2.55 × ^10-2 (W / mK). )It was used.
Assuming that 1200 (° C) combustion gas flows into the radiant tube from the inlet, the air flow velocity in the tube is 5 (m / s), the gauge static pressure at the outlet is 0 (Pa), and the radiant tube. The ambient temperature was 950 (° C.), and the inner wall of the pipe was given heat transfer efficiency in consideration of radiative cooling when the ambient temperature was 950 (° C.).

(Calculation result)
The average heat flux on the outer wall of the radiant tube when the heat transfer promoter is not inserted into the radiant tube is about 2000 (W / m ² ). When the heat transfer promoter is inserted, the average heat flux becomes larger than when the heat transfer promoter is not inserted when the surface roughness of the heat transfer promoter is 300 μm or more. When the surface roughness of the heat transfer promoter increases from 300 μm, the average heat flux further increases, but when the surface roughness of the heat transfer promoter decreases from 300 μm, the average heat flux is equivalent to the case where the heat transfer promoter is not inserted. Or it becomes smaller and the heat efficiency becomes worse.
As described above, it can be seen that the surface roughness of the heat transfer promoter capable of improving the thermal efficiency as compared with the case where the heat transfer promoter is not inserted is 300 μm or more.

(Example 4)
FIG. 12 is a graph showing the heat responsiveness due to the difference in bulk specific gravity when the heat transfer promoter of the present invention is used.
In the embodiment, the fluid analysis by computer simulation, specifically, the bulk specific gravity of the heat transfer promoter is changed to 1.1, 0.9, 0.8, 0.7, 0.5, 0.2. The heat responsiveness was calculated, and when the heat responsiveness of the conventional heat transfer promoter, which is a comparative example, was set to 100, the bulk specific gravity was 1.1, 0.9, 0.8, 0.7, 0.5. , 0.2 The heat response of the heat transfer promoter was calculated.
The calculation result is shown in FIG.

(Calculation condition)
This is the same as in Example 3.

(Calculation result)
The heat transfer promoter having a bulk specific density of 0.8, 0.7, 0.5, 0.2 has a smaller heat responsiveness value than the conventional heat transfer promoter which is a comparative example, and has a heat responsiveness. It turns out that becomes better. The value of thermal responsiveness decreases as the bulk specific density decreases from 0.8, but when the bulk specific density becomes 0.2 or less, the rate of change in thermal responsiveness decreases, and the thermal responsiveness value is around 60. calm down.
When the bulk specific density is larger than 0.8, the value of heat responsiveness is equal to or larger than that of the conventional heat transfer promoter, and the heat responsiveness is deteriorated.
As described above, it can be seen that the bulk specific gravity of the heat transfer promoter capable of improving the heat response as compared with the conventional heat transfer promoter is 0.2 or more and 0.8 or less.

10,20 Heat transfer promoter of the present invention,
1a Stoma,
1b small pores 2 fins,
2a tip,
2b groove,
3 burner,
4 Radiant tube,
5 furnace wall,
6 Combustion gas,
7 outlet,
8 inlet,
9 Central axis (central part),
9a Center point (central axis),
11 top surface,
13 bottom,
14 Spiral passage (heat transfer path),
100,200 Connected heat transfer promoter

Claims (4)

In a heat transfer promoter made of porous ceramics, which is provided by connecting a plurality of pieces inside a radiant tube and having a plurality of fins provided on the outer periphery of the central axis.
The heat transfer accelerator is formed by sintering a large number of pores of different sizes using a mixture containing clay as a fireproof raw material and using a pore material or a foaming agent.
The outer peripheral surface and the inside of the heat transfer promoter have an air hole having a pore diameter of 0.1 to 10 mm and a small pore having a pore diameter smaller than that of the air hole, and the air hole and the small pore are distributed throughout and the transfer. Concavities and convexities are formed on the outer peripheral surface of the heat transfer promoter, and / or the atmospheric pores having a pore diameter of 0.1 to 10 mm and small pores having a pore diameter smaller than the atmospheric pores on the outer peripheral surface and inside of the heat transfer promoter. The outer surface of the outer peripheral surface of the heat transfer promoter is formed to have an arithmetic average roughness of 300 μm or more, and silicon carbide (SiC) is applied to the outer surface of the unevenness of the plurality of connected electric heat transfer promoters. A heat transfer promoter, characterized in that the coating layer of silicon carbide (SiC) is uniformly applied to the entire outer peripheral surface of the uneven surface with a thickness of 0.5 mm to 1.0 mm. On the outer surface of the heat transfer promoter, grooves are formed radially from the center of the heat transfer promoter toward the tip of the fin, and the width of the groove is gradually increased toward the tip of the fin. The heat transfer promoter according to claim 1, wherein the heat transfer promoter is provided. In a heat transfer promoter made of porous ceramics, which is provided by connecting a plurality of heat transfer members inside a radiant tube.
The heat transfer accelerator is formed by sintering a large number of pores of different sizes using a mixture containing clay as a fireproof raw material and using a pore material or a foaming agent.
The outer peripheral surface and the inside of the heat transfer promoter have an air hole having a pore diameter of 0.1 to 10 mm and a small pore having a pore diameter smaller than that of the air hole, and the air hole and the small pore are distributed throughout and the transfer. Concavities and convexities are formed on the outer peripheral surface of the heat transfer promoter, and / or the atmospheric pores having a pore diameter of 0.1 to 10 mm and small pores having a pore diameter smaller than the atmospheric pores are formed on the outer peripheral surface and inside of the heat transfer promoter. The outer surface of the outer peripheral surface of the heat transfer promoter is formed to have an arithmetic average roughness of 300 μm or more, and a coating layer of silicon carbide (SiC) is formed on the outer surface of the unevenness of the plurality of connected electric heat transfer promoters by impregnation. A method for producing a heat transfer promoter, which is formed and is characterized in that a coating layer of the silicon carbide (SiC) is uniformly applied to the entire outer peripheral surface of the uneven surface with a thickness of 0.5 mm to 1.0 mm. Grooves are formed radially from the center of the heat transfer promoter toward the tip of the fin on the outer surface of the heat transfer promoter, and the width of the groove is gradually increased toward the tip of the fin. 3. The method for producing a heat transfer promoter according to claim 3.

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