JPH1151588A - Multipipe heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance strength at a welded part by employing a double tube plate system having a hollow section in the structure of a high temperature side tube sheet, supplying the cooling air externally into the hollow section of the high temperature side tube sheet and cooling the tube sheet forcibly thereby lowering the temperature at the welded part of a heating tube and the high temperature side tube sheet. SOLUTION: A double tube plate system comprising a first tube sheet 4a on the flow-in side of a preheated fluid and a second tube sheet 4b constituting the heat source side is employed in the structure of a high temperature side tube sheet 4 where a plurality of heating tubes penetrates a front duct 6. The part defined by the double tube plates provides a cooling air ventilation space (hollow section) E. The temperature at the welded part of the heating tube 4b and the high temperature side tube sheet 4 can be kept low through forced cooling with the cooling air. Consequently, the strength can be enhanced at the welded part of the heating tube 4b and the high temperature side tube sheet 4 while improving the structural defect.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat source fluid flowing through a plurality of heat transfer tubes inserted into an outer cylinder connected between a front duct and a rear duct, and heat radiated through the heat transfer tubes. Is transferred to the preheating fluid supplied between the heat transfer tubes in the multi-tube heat exchanger, where the tube plate on the high temperature side (heat source fluid inlet side / preheating fluid outlet side) Sheet) is a double tube sheet system, cooling air is introduced from the outside into the cooling air ventilation space between the tube sheets, and the tube sheet is forcibly cooled, thereby lowering the weld temperature between the heat transfer tube and the tube sheet on the high temperature side. Let me
An object of the present invention is to provide a multi-tube heat exchanger capable of improving the strength of a welded portion, improving structural defects, improving the service life, and reducing the frequency of repair.

[0002]

2. Description of the Related Art In recent years, the demand for various plants in which multi-tube heat exchangers are installed has led to an increase in the capacity of various facilities,
Along with this, the size of the multi-tube heat exchanger has been increased (especially the number of heat transfer tubes has been increased), and the temperature of the heat source fluid has to be increased (both for the heat source and the preheating fluid). There has been an increasing demand for structuralization and an intermittent operation of the plant (especially an increase in the number of repetitions of heating / cooling at the start and stop of the operation).

As a result, the temperature of the weld between the heat transfer tube, which is the fixing point of the heat transfer tube constituting the main part of the multi-tube heat exchanger, and the high temperature side tube sheet (color pipe) becomes high. Damage occurs in a short period of time due to, for example, a reduction in the fatigue strength of the welded portion due to the effects of heating and cooling at the time of stoppage, and the frequency of damage increases, which is a problem with durability.

[0004]

As shown in FIG. 7, a conventional multi-tubular heat exchanger 20 comprises an outer cylinder 21 having an inlet A and an outlet B for a preheating fluid, and one end of the outer cylinder 21. A plurality of baffle plates 22 arranged at equal intervals on the inner wall surface from the other end to the other end, supported in the middle by the baffle plate 22, and inserted along the longitudinal direction of the outer cylinder 21,
Moreover, the high temperature side tube sheet 23 and the low temperature side tube penetrate through the high temperature side tube sheet 23 arranged to close one end of the outer cylinder 21 and the low temperature side tube sheet 24 arranged to close the other end of the outer cylinder 21. It is composed of a plurality of heat transfer tubes C each having an opening of each tube facing the inside of a front duct 25 and a rear duct 26 connected to the sheet 24, respectively. Since the high temperature side tube sheet 23 incorporated in the vessel 20 adopts a single tube sheet type tube sheet,
The temperature applied to the welded portion D between the plurality of heat transfer tubes C and the color pipe 27 penetrating the high temperature side tube sheet 23 is applied to the heat transfer tube C and the color pipe 27 because it is exposed for a long time under very high temperature conditions. The thermal stress was excessive, so that the fatigue strength of the welded portion D was reduced, causing damage in a short period of time, and the frequency of damage was increased, and had various disadvantages in durability.

According to the present invention, a heat source fluid is circulated through a plurality of heat transfer tubes inserted into an outer cylinder connected between a front duct and a rear duct, and heat radiated through the heat transfer tubes is dissipated by each of these tubes. In a multi-tube heat exchanger that performs heat exchange by transmitting to a preheating fluid supplied between heat transfer tubes,
The tube sheet (tube sheet) on the high temperature side (heat source fluid inlet side / preheating fluid outlet side) is a double tube sheet, and cooling air is introduced from the outside between the tube sheets (cooling air ventilation space) to forcibly cool the tube sheet. Multi-tube heat exchanger that can lower the temperature of the weld between the heat transfer tube and the tube sheet on the high-temperature side, improve the strength of the weld, improve structural defects, improve service life and reduce the frequency of repairs Is to provide.

[0006]

According to the present invention, there is provided an outer cylinder provided with an inlet / outlet for a preheating fluid,
A plurality of baffle plates arranged at equal intervals on the inner wall surface from one end to the other end of the outer cylinder, supported midway by the baffle plate, and inserted along the longitudinal direction of the outer cylinder, and A high-temperature side tube sheet arranged to close one end of the outer cylinder, a low-temperature side tube sheet arranged to close the other end of the outer cylinder, and penetrates these high-side tube sheet and low-temperature side tube sheet. A multi-tube heat exchanger comprising a plurality of heat transfer tubes each having an opening of a tube facing the inside of a front duct and a rear duct connected to each other via the high-temperature side tube sheet and the low-temperature side tube sheet. In the exchanger, the structure of the high temperature side tube sheet is a double tube sheet system having a hollow portion (cooling air ventilation space), and cooling air is externally provided in the hollow portion of the high temperature side tube sheet. And the cooling air supplied to the hollow portion is discharged from a cooling air outlet provided in communication with the hollow portion, and the high-temperature side tube sheet having the double tube sheet system is supplied with a preheating fluid. The first tube sheet on the inflow side and the second tube sheet structure constituting the heat source side are provided, and the second tube sheet is provided in a double-layered structure of a heat insulating board and a heat insulating castable, and further in a hollow portion of the high temperature side tube sheet. The cooling air supplied from the outside is configured such that the cooling air supplied to the hollow portion is discharged to the outside from a cooling air outlet provided in communication with the hollow portion, or provided on the outer peripheral portion of the tube sheet and the cone plate. It is configured to be discharged from the cooling air discharge hole into the outer cylinder.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a multitubular heat exchanger according to the present invention will be described below in detail with reference to the drawings. FIG.
FIG. 2 is a sectional view showing the overall structure of the multi-tubular heat exchanger according to the present invention, FIG. 2 is a plan view of a high-temperature side tube sheet portion of the multi-tubular heat exchanger according to the present invention, and FIG. FIG. 4 is a cross-sectional view of a main part showing a double tube sheet structure of a high-temperature side tube sheet portion of a multi-tube heat exchanger according to the present invention. FIG. 4 shows fixing points of heat transfer tubes of the multi-tube heat exchanger according to the present invention. FIG. 5 is a cross-sectional view showing a structure of a welded portion between the heat transfer tube and the high-temperature side tube sheet (color pipe). FIG. 5 is a diagram illustrating cooling of the hollow portion by cooling air supplied from the outside to the hollow portion of the high-temperature side tube sheet according to the present invention. FIG. 6 is a cross-sectional view showing another embodiment of the cooling air discharging method of the high temperature side tube sheet portion of the multi-tube heat exchanger according to the present invention.

[0008]

Embodiment 1 A multi-tube heat exchanger 1 according to the present invention is shown in FIG.
6, an outer cylinder 2 provided with an inlet A and an outlet B for a preheating fluid, and a plurality of baffle plates arranged at equal intervals on an inner wall surface from one end to the other end of the outer cylinder 2. 3
The baffle plate 3 is supported halfway and inserted along the longitudinal direction of the outer cylinder 2.
Through the high-temperature side tube sheet 4 arranged to close one end and the low-temperature side tube sheet 5 arranged to close the other end of the outer cylinder 2 and connected to the high-temperature side tube sheet 4 and the low-temperature side tube sheet 5, respectively. And a plurality of heat transfer tubes 8 each having an opening of each tube facing the inside of the front duct 6 and the rear duct 7.

By the way, the structure of the high-temperature side tube sheet 4 (the heat source fluid inlet side and the preheating fluid outlet side) through which the plurality of heat transfer tubes 8 penetrate the front duct 6 is the first tube on the side where the preheating fluid flows. The double tube sheet system of the sheet 4a and the second tube sheet 4b (using a thin plate structure) constituting the heat source side is adopted, and a portion defined by the double tube sheet is used as a cooling air ventilation space (hollow portion) E. It is becoming.

A front end of a cooling air introduction pipe 9 inserted from the front duct 6 side faces the center of the cooling air ventilation space E. An introduction castable 1 for shutting off the high temperature of the heat source fluid is provided on the outer periphery of the cooling air introduction pipe 9.
A cooling air distribution nozzle 11 is attached to a leading end of the cooling air introduction pipe 9 facing the center of the cooling air ventilation space E.

Around the double tube sheet of the first tube sheet 4a and the second tube sheet 4b constituting the heat source side, cooling air supplied from the cooling air distribution nozzles 11 (a plurality of nozzles), that is, cooling heat absorption Plate 12 and header outer cylinder 13 for discharging hot air F
It is configured to be discharged to the outside through a discharge air annular pipe 15 through a cooling air discharge nozzle (a plurality of nozzles) 14 penetrated through the cooling air discharge nozzle.

By the way, the center of the plurality of heat transfer tubes 8 inserted along the longitudinal direction of the outer cylinder 2 corresponds to the cooling air introduction pipe 9 arranged at the center of the cooling air ventilation space E. In this connection, one heat transfer tube 8 is deleted (that is, considering the drift of the preheating fluid because the drift of the center portion of the preheating fluid is increased), the dummy tube 16 is replaced with the dummy tube 16 instead.
Has been arranged.

In the case where the number of the heat transfer tubes 8 is large, the influence of the drift in the central portion is small. Therefore, there is a case where the dummy tubes 16 need not be arranged as in the above embodiment. . In the vicinity of the open ends of the heat transfer tubes 8 penetrating through the second tube sheet 4b constituting the heat source side and facing the inside of the front duct 6, the heat insulating effect from the heat source is increased and the cooling effect is improved. In order to increase the temperature, a heat insulating board 17 and a color pipe 18 are provided so that the temperature rise (the welded portion D of the second tube sheet 4b) can be reduced as much as possible.

[0014]

Second Embodiment In the first embodiment, the cooling air supplied to the hollow portion (the cooling air ventilation space E) of the high temperature side tube sheet is provided with the cooling air discharge nozzle provided in communication with the cooling air ventilation space E. Although described as having been configured to be discharged to the outside from the outside 14, the inside of the outer cylinder 2 from the cooling air discharge hole 19 provided on the outer periphery of the first tube sheet 4a and the cone plate 12 as shown in FIG. You may comprise so that it may discharge.

The other structure is the same as that of the first embodiment. Hereinafter, the operation of the multitubular heat exchanger according to the present invention will be described in detail based on the first and second embodiments. In the multi-tubular heat exchanger 1 according to the present invention, the structure of the high-temperature side tube sheet 4 (the heat source fluid inlet side / the preheating fluid outlet side) in which one ends of the plurality of heat transfer tubes 8 pass through the front duct 6 is preheated fluid. The first tube sheet 4a on the side from which water flows out and the second tube sheet 4b (using a thin plate structure) constituting the heat source side are of a double tube sheet type, and a section defined by the double tube sheet is a cooling air ventilation space. The front end of the cooling air introduction pipe 9 inserted from the front duct 6 side faces the center of the cooling air ventilation space E, and the cooling air distribution nozzle 11 attached to the front end of the cooling air introduction pipe 9 Since the cooling air is supplied, the high temperature side tube sheet 4, especially the color pipe 18 and the second tube sheet 4b arranged on the outer periphery of the heat transfer tube 8 facing the heat source fluid inlet side are forcibly cooled by the cooling air. To Becomes DOO, weld temperature of the heat transfer tube 4b and the high-temperature side tube sheet 4 can be kept at a temperature considerably lower than that of conventional multi-tube heat exchanger. Therefore, the strength of the welded portion between the heat transfer tube 4b and the high temperature side tube sheet 4 is improved and structural defects are improved, so that the service life can be greatly improved and the frequency of repair can be reduced.

Further, the cooling air supplied through the cooling air distribution nozzles 11 (plurality) to the cooling air ventilation space E formed by the double tube sheet of the first tube sheet 4a and the second tube sheet 4b is transmitted. Heat tube 8 and color pipe 1
8 is forcibly cooled, that is, the hot air F that has cooled and absorbed heat at a predetermined temperature is quickly discharged to the outside via the cooling air discharge nozzles (plurality) 14 and the discharge air annular pipe 15. The cooling efficiency is very good.

Further, since the cooling air distribution nozzle 11 disposed with respect to the cooling air ventilation space E is configured to be located at the center of the cooling air ventilation space E, the cooling air ventilation space is provided via the cooling air distribution nozzle 11. The cooling air blown to E can forcibly cool the heat transfer tubes 8 and the color pipes 18 arranged concentrically from the center position toward the outer periphery, and the forced cooling is performed from the center position. Since the cooling is performed toward the outer peripheral portion of the tube sheet 4, the cooling can be performed very efficiently without any positional constraint.

In addition to the forced cooling structure described above, the heat transfer tube 8 penetrates through the second tube sheet 4b constituting the heat source side and faces the front duct 6, near the open end of each heat transfer tube 8. Since the heat insulating board 17 and the color pipe 18 are employed, the heat insulating effect from the heat source is good, and therefore, the cooling effect can be further enhanced.
The high temperature of the weld in b can be reduced as much as possible.

[0019]

Second Embodiment In the first embodiment, the cooling air supplied to the hollow portion of the high-temperature side tube sheet is discharged outside from the cooling air discharge nozzle 14 provided in communication with the cooling air ventilation space E. However, as described in the second embodiment, the first tube sheet 4a and the cooling air discharge hole 19 provided on the outer peripheral portion of the cone plate 12 are discharged to the inside of the outer cylinder 2 as described in the second embodiment. The structure can be made very simple.

[0020]

According to the present invention, as described in detail above,
An outer cylinder provided with an inlet / outlet for the preheating fluid, a plurality of baffle plates arranged at equal intervals on the inner wall surface from one end to the other end of the outer cylinder, and supported halfway by the baffle plate, and A high-temperature side tube sheet that is inserted along the longitudinal direction of the outer cylinder and that is arranged to close one end of the outer cylinder, and a low-temperature side tube sheet that is arranged to close the other end of the outer cylinder; A plurality of tubes that penetrate the high-temperature tube sheet and the low-temperature tube sheet and face the opening of the tube inside the front duct and the rear duct that are connected to each other via the high-temperature tube sheet and the low-temperature tube sheet In the multi-tubular heat exchanger composed of the heat transfer tubes described above, the structure of the high-temperature side tube sheet is a double tube plate having a hollow portion (cooling air ventilation space), While supplying cooling air from the outside to the hollow portion of the sheet, the cool air supplied to the hollow portion is configured to be discharged from a cooling air outlet provided in communication with the hollow portion, and the double tube plate system The high-temperature side tube sheet has a first tube sheet on the side where the preheating fluid flows in and a second tube sheet structure forming the heat source side, and the second tube sheet has a two-layered structure of a heat insulating board and a heat insulating castable, and The cooling air supplied from the outside to the hollow portion of the high-temperature side tube sheet is configured such that the cool air supplied to the hollow portion is discharged to the outside from a cooling air outlet provided in communication with the hollow portion, or The high-temperature side tube sheet is supplied to the hollow part by discharging the cooling air to the inside of the outer cylinder through the cooling air discharge hole provided in the outer peripheral part of the sheet and the cone plate. It is appropriately cooled by air, so that the inherent stress can be maintained as a whole, and the metal temperature is reduced compared to the conventional multi-tube heat exchanger, so that it is not affected by thermal stress, pressure load and static load. It is possible to measure the strength improvement. In addition, the second tube sheet has a thin plate structure, so that the cooling heat transfer effect of the weld between the heat transfer tube and the color pipe is enhanced. Furthermore, since the cooling air introduction pipe for supplying predetermined cooling air to the hollow portion is arranged at the center of the front duct, it induces turbulence in the heat source fluid flowing into the front duct, and causes each heat transfer. It has the effect of reducing the drift of the heat source fluid flowing into the tubes, and corrects structural defects in the welds of each heat transfer tube, thereby increasing the durability and reducing the frequency of maintenance and repair work. And various other excellent effects.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the overall structure of a multitubular heat exchanger according to the present invention;

FIG. 2 is a plan view of a high-temperature side tube sheet part of the multitubular heat exchanger according to the present invention,

FIG. 3 is a sectional view of an essential part showing a double tube sheet structure of a high temperature side tube sheet portion of the multi-tube heat exchanger according to the present invention;

FIG. 4 is a cross-sectional view showing a structure of a weld between a heat transfer tube and a high-temperature side tube sheet (color pipe), which is a fixing point of the heat transfer tube of the multi-tube heat exchanger according to the present invention;

FIG. 5 is an explanatory view showing a state of cooling the hollow portion by cooling air supplied from the outside to the hollow portion of the high-temperature side tube sheet according to the present invention;

FIG. 6 is a cross-sectional view showing another embodiment of a cooling air discharging method for a high-temperature side tube sheet portion of the multi-tube heat exchanger according to the present invention;

FIG. 7 is a cross-sectional view showing the entire structure of a conventional multi-tube heat exchanger.

[Explanation of symbols] 1 Multi-tubular heat exchanger 2 Outer cylinder 3 Baffle plate 4 High temperature side tube sheet 4a First tube sheet 4b Second tube sheet (using thin plate structure) 5 Low temperature side tube sheet 6 Front duct 7 Rear duct Reference Signs List 8 heat transfer tube 9 cooling air introduction pipe 10 introduction castable 11 cooling air distribution nozzle 12 cooling plate 13 header outer cylinder 14 cooling air discharge nozzle (plural) 15 discharge air ring tube 16 dummy tube 17 heat insulation board 18 color pipe 19 cooling air Discharge hole A Preheating fluid inlet B Preheating fluid outlet D Welded part E Cooling air ventilation space (hollow part) F Hot air

Claims (4)

[Claims] 1. An outer cylinder provided with an inlet / outlet for a preheating fluid, a plurality of baffle plates arranged at equal intervals on an inner wall surface from one end to the other end of the outer cylinder, and a midway between the baffle plates. A high-temperature side tube sheet supported and inserted along the longitudinal direction of the outer cylinder, and arranged to close one end of the outer cylinder, and a lower-temperature side sheet arranged to close the other end of the outer cylinder. The tube opening extends through the tube sheet and the inside of the front duct and the rear duct that penetrate the high-temperature tube sheet and the low-temperature tube sheet and are connected to each other through the high-temperature tube sheet and the low-temperature tube sheet. In a multi-tube heat exchanger composed of a plurality of heat transfer tubes, the high-temperature side tube sheet has a double-tube sheet structure having a hollow portion. The cooling air is supplied to the hollow portion (cooling air ventilation space) from the outside, and the cooling air supplied to the hollow portion is configured to be discharged from a cooling air outlet provided in communication with the hollow portion. Multi-tube heat exchanger. 2. The high-temperature side tube sheet of the double tube sheet type has a first tube sheet on a side to which a preheating fluid flows and a second tube sheet structure on a heat source side, and the second tube sheet is insulated. 2. The multi-tube heat exchanger according to claim 1, wherein the heat exchanger has a two-layer structure of a board and a heat-insulating castable. 3. A cooling air supplied from outside to a hollow portion (cooling air ventilation space) of the high temperature side tube sheet is discharged to the outside through a cooling air discharge port provided in the hollow portion. The multi-tube heat exchanger according to claim 1, wherein: 4. Cooling air supplied from the outside to the hollow portion (cooling air ventilation space) of the high-temperature side tube sheet enters the outer tube through a cooling air discharge hole provided in the outer peripheral portion of the tube sheet and the cone plate. The multi-tube heat exchanger according to claim 1, wherein the heat exchanger is configured to discharge the heat.