SU654845A1 - Furnace roller - Google Patents

Description

(54) HOSE ROLLER

the carrier is heated and partially evaporated. The pressure in the middle part of the roller increases slightly. Formed with a two-phase mixture moves to the ends of the roller, mainly along the inner tube, where there are minimal hydraulic resistances. The area of the holes in the middle part of the inner tube is 4-10 times the area of the perforations of the partitions. The ratio of the areas of the holes in the middle part of the inner tube and in the partition is determined from the condition that the required amount of heat transfer fluid from the coolers is supplied to the working part of the roller and the two phases mixture is unhindered to the coolers. The heat transfer fluid occupies the lower part of the annular channel section.

The holes in the partition are evenly distributed around the circumference in order to ensure the continuous flow of the coolant during the rotation of the roller. The number of holes must be at least four. The two-phase mixture entering the refrigerators is cooled, the coolant vapors condense, and in the liquid state they drain into the lower part of the cavity. As the volume of the mixture decreases during condensation, the pressure decreases in the areas where the coolers are located.

The heat transfer fluid through the holes in the partitions flows into the middle part of the roller, cools its inner surface and partially evaporates. The process of heating, evaporation, cooling and condensation of the coolant and the transfer of heat from the high-temperature zone to the refrigerators takes place continuously.

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During boiling and condensation, very high heat transfer coefficients are created, which ensures efficient uniform cooling of the rollers and efficient heat removal. The inner cavity of the roller is under pressure of several atmospheres, which also contributes to the efficiency of heat transfer, as heat transfer coefficients increase with pressure to a certain level, all other conditions being equal. There is practically no danger of scale formation and sludge deposition in the roller, since the same heat transfer volume is in circulation: tel.

As a consequence, the durability of the roller increases. Separating the paths of the heated and cooled coolant by means of an internal pipe with partitions allows for intensive movement of the coolant inside the roller and using the coolers to maintain the desired temperature of the roller surface.

in the case of the pchpik a liquid heat carrier circulates and a two-phase sem under pressure of several atmospheres. The boiling point with pressure increase is known to increase. For example, the boiling point of water at a pressure of 10 atm is 179 ° C. Therefore, the inner surface of the housing will have a higher temperature than when the roller is cooled with cold water. Under similar external conditions (oven temperature), the temperature difference in the wall of the roller decreases, and the temperature of the outer surface of the housing increases. As a result, under similar conditions, the temperature difference between the upper and lower surfaces of the heated metal, i.e. In general, the furnace quality of the metal is improved. An increase in the temperature of the outer surface of the roller also causes a decrease in the removal of heat from the working space of the furnace, i.e. reduction of heat loss for cooling. In addition, with this design, it is possible to recover heat by including refrigerators in a water heating system or even producing steam.

The ratio of the areas of the holes in the Partitions and in the middle of the inner tube depends on the intensity of the heat sink. Due to the fact that the coolant inside the casing is driven by natural convection, the flow resistances of the circulation circuit should be minimal. A mixture consisting of a liquid and a gaseous phase, the volume of which is greater than that of a heat-transfer fluid, is moving from the high-temperature zone. The amount of the gaseous phase depends on the intensity of the heat sink and the rate of circulation of the coolant.

The rationale for the proposed limits of area ratios is given by example, where water and water vapor are taken as the coolant. It is assumed that it is necessary to divert 1 million kcal per 1 hour with an average pressure inside the roller body of 10 atm. For this you need to bring water

100QOOQ

U

 2080 kg / h

482.1

V mg. V 2080 0.001126

 2.34 m3 / h; where D1 is the mass of water, kg / h;

U is the amount of heat removed kcal / h;

d - the heat of vaporization is hidden, kcal / kg;

Vj - volume of water

Vj - specific volume of dry saturated steam,. . . -.

Claims (2)

With a speed of movement aodn through the opening of the partition, equal to 1 m / s. the hydraulic resistance of the bulkhead is, g 0, .9.81 56 kg / m or mm water column, where. UP is the hydraulic resistance of the partition, mm water column; W is the speed of water movement through the openings of the partition, m / s; . j) g is the density of water at operating conditions, kg / m3; p. - consumption coefficient; g - acceleration of gravity, m / s. The required area for the passage of this amount of water is Va 2.34 3600-1 360-WB 0.00065 m2. We accept that all heat is removed due to vaporization. In this case, a pair of Vme Vy 2080-0 is formed, where Y "is the volume of dry saturated steam, m3 / h; Vy is the specific volume of dry saturated steam,. .To ensure the stability of the circulation of water and water vapor in the circuit, the resistance in the steam path must be less than the resistance in the water path. As a minimum value, the Area ratio should be such that the resistances in the path of water and water vapor are equal (the pressure drop in the wall of the inner tube is also 56 mm water. Under this condition, the speed of steam in the corners of the inner pipes are 2.Dr 2.9,81.59 D 5,051 where f is the flow coefficient; AP- pressure drop before and after the openings of the inner pipe, mm water with JJj, is the density of dry saturated steam under operating conditions, kg / m. to skip this amount of steam is L12. 0,0086 3600-W. 3600-13,3 Liquid the coolant does not fill the entire cavity of the roller body, but an extra 40-50% of the volume. The liquid phase occupies the lower part of the cavity. In a cross section, this segment has an arc of approximately 1/2 to 1/3 of the circumference. heat carrier (f 0 00065 must be within this segment. But since the roller rotates and the flow of liquid heat carrier must be continuous, the holes in the partitions are evenly distributed around the entire circumference, and their total area is three times larger than the optional. " 3 walk passing heat transfer fluid. ;. fnep 2 in 3 О, ООЮ65-0.00195 m. The ratio of the area of the hole in the wall of the inner tube to the area of the partition wall is fn 0.0086 0.00195 As a lower limit value, this ratio can be reduced by 10%, i.e. up to 4.0. Reducing this ratio to less than 4.0 is impractical because it reduces the relative area for the gas phase of the gas phase. Therefore, a significant part of the gaseous phase will move into the refrigerators through the openings in the upper part of the partitions, which can worsen the cooling uniformity of the roller body. Increasing f: fpj, p decreases the resistance in the path of the gaseous phase. For the upper limit of this ratio, one should take such a value that the resistance in the path of the gaseous phase is 4 times less than in the path of the liquid phase. For this, the hole area in the inner tube should be 2 times larger than in the case when the resistance is the same. The ratio f: in this case is 8.8. In case of deviation of the actual thermal and temperature parameters of the roller from the calculated upper value of the ratio of the areas of the holes in the pipe and in the partition, it is advisable to increase to 10. A further increase does not make sense, since the main resistance of the circulation loop will be the resistance of the partitions. FIG. 1 shows a roller when installing refrigerators at both ends, a longitudinal section; in fig. 2 section A-A in FIG. one; on fig.Z option roller when installing the refrigerator from one end. Roller body 1 is a thick-walled tube. The wall thickness of the body sections protruding from the furnace is somewhat reduced. Inside the housing there is a liquid coolant. At one end of the housing 1 a flat disk 2 is installed, at the second end there is a disk 3 with a trunnion 4, which serves to communicate the rotational movement of the roller. On both sides, the housing 1 is equipped with bearings 5 and refrigerators 6. An internal pipe 7 with partitions 8 in which holes are made 9 is installed in the case. Holes 10 are made in the middle part of the pipe 7. The valve 1 is also installed in the housing 1, which is activated when the pressure rises above the permissible value, for example, if one or both of the refrigerators come out of it. The refrigerators 6 have nozzles 12 and 13 that are used for supplying and discharging water. When the refrigerator is located at one end, the holes in the inner tube are made near the end of the tcM side opposite to the refrigerator. FIG. 3) .. The rollers of the preheating heating furnace of the large-sized mill 600 are made as follows .. In the roller casing, which is a tube with an outer diameter of 200 mm, an inner diameter of 100 mm, and a length of 3 m, insert an inner tube with an outer diameter of 75 Mti, inner 70 mm, with a partition at the site of the high-temperature zone of the furnace and the refrigerator and into the cavity of the housing with a volume of 0.02 m, water as a heat carrier is poured in a quantity of 10 kg and brewed. The maximum heat flux to the surface of the roller is 220,000 kcal / m. h The area of the roller located in the furnace is 1 m, the thermal parameters of the roller are determined from the condition that the heat removal is completely accomplished by the evaporation of water. The water flow rate is 220,000. E. / -48271- b / The average pressure inside the roller housing is 10 atm. Volumetric water flow Va 456 0.001126 0.515. The area of the partition at a water velocity of 5 m / s, taking into account the free cross section of the water surface, is 30.515 - nnnftfi mler 3600-0.5 О00086 m, 8 holes with a diameter in the partition. 12 mm. The actual area of the openings in the partition wall is 0.0009. 20 holes 16 mm in diameter with a total area of 0.00402 m are made in the wall of the inner pipe from the opposite side of the refrigerator. The ratio of the holes in the wall of the inner pipe to the area of the holes in the partition is 4.5 . The vapor velocity in the holes of the inner tube is 6.3 m / s, in the inner tube 6.5 m / s. The refrigerator is made in the form of a cylindrical body in which a cooled roller is installed. In order to intensify the heat exchange, the inner part of the cooled part of the roller is made finned. The water supply to the cooler is tangential. The body of the refrigerator is provided with a hole for periodic cleaning of the outer surface of the roller. The effectiveness of the proposed roller is in increasing the durability of the rollers, reducing the specific fuel consumption, improving the quality of metal heating. An increase in the resistance of the rollers is expected to be at least three times. The economic effect of the increase in the resistance of the rollers is 100 thousand rubles. in year. The reduction in specific fuel consumption is about 10%, which gives an economic effect in the amount of 40 thousand rubles. in year. The total expected economic / leth effect of the use of the proposed roller under the conditions of the continuous mill preheater of the large-section mill 600 is about 140 thousand rubles per year. Claims of an inventive furnace roller comprising a housing and a tube with holes mounted concentrically inside it, characterized in that, in order to increase the durability of the roller and increase the efficiency of the furnace, the roller is made in the form of a sealed housing filled with heat-transfer fluid and equipped with end-side refrigerators, in this case, the fastening of the pipe to the body is made in the form of partitions with holes, the area of which is 0.25-0, 1 of the area of the holes of the internal pipe. Sources of information taken into account in the examination 1. USSR author's certificate number 160196, cl. C 21 D 9/50, 1975. 2. The patent of Germany No. 1408274, CL 18 from 9/00, 1970. one 8 s. fig.Z7