RU2534337C1 - Field pipe - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: straight-flow steam generator Field pipe comprises downcomer pipe, mid pipe arranged with clearance at the latter and outer pipe with outer surface flown over by heating heat carrier. Said clearance comprises heat-insulating material while sealant is arranged at lower part of clearance end. Mid pipe outer surface accommodates spiral element designed to intensify heat exchange processes between heat carrier and inner heat carrier in Field pipe.

EFFECT: higher heat-transfer between outer pipe inner surface and inner heat carrier.

8 cl, 4 dwg

Description

Technical field

The invention relates to mechanical engineering, namely to Field pipes for high-temperature tubular heat exchangers, for example, for direct-flow steam generators of nuclear power plants with a heating liquid metal coolant (for example, an alloy of lead with bismuth).

State of the art

Known Field pipe (patent JP 58184498, published 10.27.1983), containing an inner pipe with a wire wound on it and an outer pipe covering the inner pipe. The wire provides, in particular, the intensification of heat transfer processes in the flow of coolant flowing in the Field pipe. However, this design is ineffective when used in a once-through steam generator, in particular, due to undesirable spurious heat exchange between the coolant in the channel of the inner pipe (for example, the downward flow of feed water) and the coolant in the channel (for example, the upward flow of superheated steam) formed by the outer surface of the inner pipe and the inner surface of the outer pipe. This parasitic heat transfer reduces the temperature of superheated steam at the output of the annular channel, which, ultimately, leads to a decrease in the technical and economic indicators of a nuclear power plant using a steam generator.

The closest analogue of the invention is the Field pipe (Patent RU No. 50290, published December 27, 2005) of a direct-flow steam generator of a nuclear installation, comprising a dip pipe, an intermediate pipe mounted on it with a gap, an external pipe with an external surface, washed by the flow of the heating (external) coolant . The disadvantage of this design is, in particular, the insufficiently high intensity of heat transfer between the inner surface of the outer pipe and the flow of internal coolant in contact with it. This reduces the efficiency of the formation of superheated steam in the case of using the indicated Field pipe in a once-through steam generator, which leads to a decrease in the technical and economic indicators of a nuclear power plant using a steam generator.

Disclosure of invention

The problem to which the invention is directed, is to increase the technical and economic indicators of a nuclear power plant using a once-through steam generator with Field pipes. In particular, it consists in increasing the temperature of the superheated steam produced by the steam generator.

The technical result of the invention is to eliminate the above disadvantages, namely: increasing the heat transfer coefficient between the inner surface of the outer pipe (heated by an external coolant) and the flow of internal coolant in contact with it, as well as the reduction of parasitic heat transfer between the coolant in the channel of the inner pipe (for example, a downward flow of nutrient water) and a coolant in the channel (for example, an upward flow of superheated steam) formed by the external surface inside pipe and the inner surface of the outer pipe.

These technical results are influenced by the following essential features of the Field pipe.

The Field pipe of the direct-flow steam generator contains a down pipe, an intermediate pipe installed with a gap on the down pipe, and an outer pipe with an outer surface washed by the flow of heating medium, the gap contains heat-insulating material, a sealing element is placed in the lower end of the gap, on the outer surface of the intermediate pipe located spiral element, made with the possibility of intensification of heat transfer processes between the heating coolant and the internal coolant in the Field’s pipe.

The Field pipe may contain an additional sealing element in the upper end portion of the gap. The heat-insulating material may be selected from a group or mixture of materials including steam and water. The thermal insulation material may be gas. On the intermediate pipe transverse corrugations can be formed, made with the ability to compensate for the difference in temperature elongations of the lowering and intermediate pipes and spacing the intermediate pipe. The depth of the corrugations on the intermediate pipe may be less than the gap width, and the inner pipe may contain a spacer element. The spacer element may be longitudinal ribs in contact with the above corrugations, or a wire fixed to the ends of the lowering pipe. The spiral element can be made in the form of a spiral wound wire element with a diameter equal to or less than the gap width between the outer and intermediate pipes, and a winding pitch h = (0.5 ÷ 50) D, where D is the outer diameter of the intermediate pipe.

Brief Description of the Drawings

Figure 1 shows a design variant of the Field pipe with an additional sealing element in the upper end part of the gap and a corrugated intermediate pipe.

Figure 2 shows a cross section of the Field pipe for a variant of the Field pipe of Figure 1.

Figure 3 shows a design variant of the Field pipe with a spacer element in the form of a wire mounted on the ends of the lowering pipe.

Figure 4 shows a cross section of the Field pipe for a variant of the Field pipe of Figure 3.

The implementation of the invention

In the present invention, the device - Field's pipe is the main unit of the steam generator that produces superheated steam. The composition of the Field pipe includes an outer pipe 2, washed by the flow of the heating fluid, an intermediate pipe 3, installed with a gap 6 on the lowering pipe 4. The gap 6 contains a heat-insulating material and, accordingly, is a heat-insulating gap. The sealing element 1 is placed in the lower end part of the gap 6 between the lower 4 and the intermediate pipes 3. An additional sealing element is placed in the upper end part of the gap 6 between the outer 2 and the intermediate 3 pipes. The spiral element 5 is placed on the outer surface of the intermediate pipe 3. The spacer element 7 is fixed to the ends of the lowering pipe 3. The tube plates of the steam generator 8 form a channel for superheated steam leaving the Field pipe.

The implementation of the intermediate pipe 3 with transverse corrugations with predetermined design or empirically specified dimensions (depth) provides compensation for the difference in temperature elongations of the lowering pipe 4 and the intermediate pipe 3. In addition, such corrugation provides the spacing of the intermediate pipe in relation to the lowering pipe. The spiral element 5 is made in the form of a spirally wound wire element with a diameter equal to or less than the width of the gap between the outer and intermediate pipes, and the winding pitch h = (0.5 ÷ 50) D, where D is the outer diameter of the intermediate pipe. The winding step is selected from a given range and is selected experimentally by selecting the optimal heat transfer conditions.

The device operates as follows (see Fig 1, 3). The internal heat carrier (feed water at the inlet of the downpipe 4) descends down the downpipe of the Heat exchange pipe of the Field direct-flow steam generator. Next, the flow of the internal coolant turns 180 ° at the closed end of the outer pipe 2 and rises upward through the gap between the intermediate pipe and the inner surface of the outer pipe 2. When rising upward, the internal coolant heats up due to the transfer of heat to it from the side of the heating (external) coolant through the walls of the outer pipe.

When moving upward, the internal coolant is heated to turn into a steam-water mixture, which turns into superheated steam, as a result of heat transfer, from the heating coolant. In the lower lifting zone (by the gap between the intermediate pipe and the inner surface of the outer pipe 2), the coolant is a liquid with vapor particles inside. Further, when lifting, the coolant is steam with drops of water (middle zone). And finally, in the upper zone of the rise forms superheated steam (steam that does not contain water droplets) entering the channel with pipe boards 8.

When interacting with the spiral element 5, the flow of the internal coolant is twisted, its speed increases, the heat transfer coefficient increases (from the wall of the outer pipe 2 to the internal coolant), and the intensification of thermal processes that ensure the formation of superheated steam occurs. This effect acts in the lower and upper lifting zones. In the middle zone, heat transfer intensification occurs due to the action of centrifugal force (which occurs when twisting water droplets in a pair due to their interaction with a spiral element) on water droplets in a steam stream, which also leads to an increase in the heat transfer coefficient.

The presence of a heat-insulated gap 6 prevents unwanted radial heat transfer between the feed water passing down the downcomer 4 and the steam-water mixture rising in the gap between the outer and intermediate pipes. This, ultimately, also leads to more efficient steam formation.

The proposed design of the Field pipe can be manufactured industrially and used in high-temperature tubular heat exchangers such as direct-flow steam generators.

Claims (8)

1. Field pipe containing a lowering pipe, an intermediate pipe installed with a gap on the lowering pipe, and an outer pipe with an outer surface washed by the flow of the heating fluid, the gap containing heat-insulating material, a sealing element is placed in the lower end of the gap, and on the outer surface the intermediate pipe is a spiral element. 2. Field pipe according to claim 1, characterized in that a sealing element is placed in the upper end part of the gap. 3. The Field Pipe according to claim 1, characterized in that the heat-insulating material is selected from a group or mixture of materials including steam and water. 4. Field pipe according to claim 2, characterized in that the heat-insulating material is gas. 5. Field pipe according to claim 1, characterized in that transverse corrugations are formed on the intermediate pipe, made with the possibility of compensating for the difference in temperature elongations of the lowering and intermediate pipes and ensuring the distance of the intermediate pipe. 6. Field pipe according to claim 5, characterized in that the depth of the corrugations on the intermediate pipe is less than the gap width, and the lowering pipe contains a spacer element. 7. Field pipe according to claim 6, characterized in that the spacer element is a longitudinal ribs in contact with the corrugations, or a wire attached to the ends of the lowering pipe. 8. Field pipe according to claim 1, characterized in that the spiral element is made in the form of a spirally wound wire element with a diameter equal to or less than the width of the gap between the outer and intermediate pipes, and a winding pitch equal to from 0.5 to 50 of the outer diameter intermediate pipe.

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