JP7000166B2 - Heat exchanger leak detection method - Google Patents

Description

The present invention relates to a leak detection method for a heat exchanger.

For example, in a gas turbine, heat is exchanged between the air that cools the blades and the fuel gas using a heat exchanger to save energy (see, for example, Patent Document 1).
As a heat exchanger, for example, a multi-tube heat exchanger called a shell-and-tube type is known. The multi-tube heat exchanger has a cylindrical casing and a plurality of heat transfer tubes arranged inside the casing in parallel with the axis of the casing.
In the above-mentioned heat exchanger, heat exchange is carried out by passing a high-temperature fuel gas through a heat transfer tube and passing air between the tube plates.

Further, as a heat exchanger, a plate type heat exchanger having a plurality of plates and flowing a high temperature fluid and a low temperature fluid through a flow path formed between the plates to exchange heat is known.

Japanese Unexamined Patent Publication No. 2001-296090

By the way, in the operation of the heat exchanger having the above structure, how to detect the gas leak due to the deterioration of the heat transfer tube at an early stage is an issue.

INDUSTRIAL APPLICABILITY According to the present invention, a gas leak can be detected at an early stage in a heat exchanger including a first distribution unit in which a first fluid flows and a second distribution unit in which a second fluid different from the first fluid flows. It is an object of the present invention to provide a leak detection method for a heat exchanger.

According to the first aspect of the present invention, the leak detection method of the heat exchanger has a first heat transfer surface and faces the first flow unit through which the first fluid flows and the first heat transfer surface. A heat exchange having a second heat transfer surface, an inert space between the first heat transfer surface, and a second flow section through which a second fluid different from the first fluid flows. A leak detection method for a device, a pressure measuring step of measuring the pressure in the inert space, a threshold calculation step of acquiring the temperature of the inert space and calculating a threshold based on the temperature, and the pressure It has a leak determination step of determining that a leak has occurred when it is larger than the threshold value, and in the threshold value calculation step, the temperature is the temperature of the first fluid supplied to the first flow unit. , The temperature of the first fluid discharged from the first flow section, the temperature of the second fluid supplied to the second flow section, and the temperature of the second fluid discharged from the second flow section. Calculated based on the temperature .

With such a configuration, leaks can be detected early based on the temperature and pressure of the active space. Further, by continuously acquiring the pressure and temperature of the inert space, it is possible to detect the leak even during the operation of the heat exchanger.

In the leak detection method of the heat exchanger, in the threshold calculation step, the temperature is the temperature of the first fluid supplied to the first flow unit and the temperature of the first fluid discharged from the first flow unit. , The temperature of the second fluid supplied to the second flow section, and the temperature of the second fluid discharged from the second flow section may be averaged.
In the leak detection method of the heat exchanger, in the threshold calculation step, the temperature is the temperature of the first fluid supplied to the first flow unit and the temperature of the first fluid discharged from the first flow unit. , The temperature of the second fluid supplied to the second flow section, and the temperature of the second fluid discharged from the second flow section, multiplied by a coefficient obtained by adding a time delay to the average. It may be calculated by.
In the leak detection method of the heat exchanger, in the threshold calculation step, the temperature is the temperature of the first fluid supplied to the first flow unit and the temperature of the first fluid discharged from the first flow unit. In addition to the temperature of the second fluid, the temperature of the second fluid supplied to the second flow section, and the temperature of the second fluid discharged from the second flow section, the flow rate of the second fluid, and It may be calculated based on the thermal capacity of the casing.

With such a configuration, leaks can be detected even when it is difficult to measure the temperature of an inert space.

In the leak detection method of the heat exchanger, the heat exchanger is a tubular casing having a first supply port to which the first fluid is supplied and a first discharge port to which the first fluid is discharged. The inner pipe extends so as to pass through the inner space of the casing, and the inner pipe is accommodated inside so as to pass through the inner space and the inner pipe through which the second fluid flows. The first heat transfer surface is the inner peripheral surface of the outer tube, and the second is the inner peripheral surface of the outer tube. The heat transfer surface may be the outer peripheral surface of the inner pipe.

According to the present invention, leaks can be detected early based on the temperature and pressure of the active space.

It is sectional drawing of the heat exchanger of the 1st Embodiment of this invention. It is a graph explaining the leak detection part of the control device of the heat exchanger of the 1st Embodiment of this invention. It is a flowchart explaining the leak detection method of the heat exchanger of the 1st Embodiment of this invention. It is sectional drawing of the heat exchanger of the 2nd Embodiment of this invention.

[First Embodiment]
Hereinafter, the leak detection method of the heat exchanger according to the first embodiment of the present invention will be described in detail with reference to the drawings.
The heat exchanger of this embodiment is a multi-tube heat exchanger called a shell and tube type. The heat exchanger accommodates a plurality of heat transfer tubes inside the casing, and exchanges heat by flowing fluids having different temperatures inside and outside the heat transfer tubes.
The heat exchanger of the present embodiment exchanges heat between the fuel gas and the air used for cooling in the gas turbine to heat the fuel gas and cool the air. However, the use of the heat exchanger is not limited to this.

As shown in FIG. 1, the heat exchanger 1 includes a casing 2, a plurality of inner tubes 3 arranged in the casing 2 and functioning as heat transfer tubes, and a plurality of outer tubes 4 containing the inner tubes 3 inside. And have. A part of the heat transfer tube of the heat exchanger 1 of this embodiment is a double tube. Although only one inner pipe 3 and two outer pipes 4 are shown in FIG. 1, the heat exchanger 1 of the present embodiment has a plurality of inner pipes 3 and a plurality of outer pipes 4. There is.

The casing 2 has a dome-shaped (hemispherical) first dome portion 5, a tubular tubular portion 7, and a dome-shaped second dome portion 6. The first dome portion 5 is connected to the cylinder portion 7 so as to seal one end of the cylinder portion 7, and the second dome portion 6 is connected to the cylinder portion 7 so as to seal the other end of the cylinder portion 7. ing.

The first dome portion 5 and the cylinder portion 7 are separated by a first pipe plate 9, and the fuel gas chamber 12 is formed by the first dome portion 5 and the first pipe plate 9. The fuel gas chamber 12 is divided into a first fuel gas chamber 12a and a second fuel gas chamber 12b by a partition plate 16.
The second dome portion 6 and the cylinder portion 7 are separated by a third pipe plate 11, and the first nitrogen gas chamber 13 is formed by the second dome portion 6 and the third pipe plate 11.

The space formed by the first pipe plate 9, the tubular portion 7, and the second pipe plate 10 is partitioned by the second pipe plate 10. The second pipe plate 10 is arranged so that the distance between the first pipe plate 9 and the second pipe plate 10 is smaller than the distance between the second pipe plate 10 and the third pipe plate 11.
The second nitrogen gas chamber 14 is formed by the tubular portion 7, the first pipe plate 9, and the second pipe plate 10.
An air chamber 15 (first distribution section) into which air A (first fluid) is introduced is formed by a tubular portion 7, a second pipe plate 10, a third pipe plate 11, and a plurality of outer pipes 4. There is.

In the first dome portion 5, a fuel gas supply port 18 for supplying fuel gas FG (second fluid) to the first fuel gas chamber 12a and a fuel gas exhaust for discharging fuel gas FG from the second fuel gas chamber 12b are provided. The exit 19 is formed.
The cylinder portion 7 is formed with an air supply port 20 (first supply port) for supplying air A to the air chamber 15 and an air discharge port 21 (first discharge port) for discharging air A from the air chamber 15. ing. Further, the cylinder portion 7 is formed with a nitrogen gas discharge port 23 for discharging nitrogen gas NG from the second nitrogen gas chamber 14.
The second dome portion 6 is formed with a nitrogen gas supply port 22 for supplying nitrogen gas NG to the first nitrogen gas chamber 13.

The outer pipe 4 extends into the air chamber 15 in the axial direction D of the tubular portion 7 (hereinafter, simply referred to as the axial direction D) and connects the first nitrogen gas chamber 13 and the second nitrogen gas chamber 14. Is. One end of the outer pipe 4 is connected to the second pipe plate 10, and the other end of the outer pipe 4 is connected to the third pipe plate 11. The first nitrogen gas chamber 13 and the second nitrogen gas chamber 14 communicate with each other through the space inside the outer pipe 4.
The inner peripheral surface 4s (first heat transfer surface) of the outer tube 4 functions as a heat transfer surface of the air chamber 15.

The inner pipe 3 is a U-shaped pipe. One end 3a of the inner pipe 3 and the other end 3b of the inner pipe 3 are connected to the first pipe plate 9. In the inner pipe 3, the fuel gas FG in the first fuel gas chamber 12a flows to the inside of the inner pipe 3 through one end 3a of the inner pipe 3, and the second fuel gas chamber is passed through the other end 3b of the inner pipe 3. It is arranged so as to be discharged to 12b.

The inner pipe 3 has a linear first straight portion 25 and a second straight portion 26, and an arc-shaped bend portion 27 connecting the first straight portion 25 and the second straight portion 26 in the first nitrogen gas chamber 13. Have. The first straight line portion 25 and the second straight line portion 26 extend so as to be accommodated inside the outer pipe 4. As a result, the outer peripheral surface (second heat transfer surface) of the inner tube 3 and the inner peripheral surface (first heat transfer surface) of the outer tube are arranged so as to face each other.
The bend portion 27 is arranged in the first nitrogen gas chamber 13. The outer pipe 4 accommodates the inner pipe 3 inside so as to pass through the air chamber 15 (internal space of the casing 2), and extends in the axial direction D, which is the extending direction of the inner pipe 3.
Air A, which is a second fluid different from the fuel gas FG, flows through the inner IS (second flow section) of the inner tube 3, and the outer peripheral surface (second heat transfer surface) of the inner tube 3 is a heat transfer surface. Functions as.

The outer diameter of the outer pipe 4 can be, for example, 1.1 to 1.2 times the outer diameter of the inner pipe 3. The outer diameter of the outer pipe 4 is set so that a predetermined space is formed between the outer peripheral surface of the inner pipe 3 and the inner peripheral surface of the outer pipe 4.
The air chamber 15 is provided with a plurality of baffle plates 28 so that the flow of the air A in the air chamber 15 hits the outer pipe 4 as equally as possible. The baffle plate 28 also functions as a support member for supporting the outer pipe 4.

The heat exchanger 1 of the present embodiment has a plurality of temperature sensors TS1, TS2, TS3, TS4, a pressure sensor PS, and a control device 60.
The heat exchanger 1 has a first temperature sensor TS1 that measures the temperature T1 of the gas flowing inside the fuel gas supply port 18, and a second temperature sensor TS2 that measures the temperature T2 of the gas flowing inside the fuel gas discharge port 19. A third temperature sensor TS3 that measures the temperature T3 of the gas flowing inside the air supply port 20, and a fourth temperature sensor TS4 that measures the temperature T4 of the gas flowing inside the air discharge port 21. There is.

The heat exchanger 1 has a pressure sensor PS that measures the pressure P of the gas in the first nitrogen gas chamber 13.
The temperatures T1, T2, T3, T4 measured by the temperature sensors TS1, TS2, TS3, and TS4, and the pressure P measured by the pressure sensor PS are transmitted to the control device 60.

The control device 60 includes a leak detection unit 61 that detects a leak based on the temperatures T1, T2, T3, T4 measured by the temperature sensors TS1, TS2, TS3, and TS4, and the pressure P measured by the pressure sensor PS. Have. The leak referred to here is a leak that occurs in the inner tube 3 or the outer tube 4 that constitutes the heat transfer tube due to deterioration or the like.

The leak detection unit 61 stores a mathematical formula (1) for calculating a threshold value L, which is a reference for leak detection.
L = 1.1 × (R / V) × T ・ ・ ・ (1)
The equation (1) is an equation based on the straight line P = (R / V) × T by the ideal gas state equation PV = RT. Here, the coefficient R is a molar gas constant, and V is a volume determined by the specifications of the heat exchanger 1. That is, R / V is constant. Further, the temperature T is the temperature of the inert space NA.

The leak detection unit 61 has a function of acquiring the temperature T of the inactive space NA based on the temperatures T1, T2, T3, and T4 measured by the temperature sensors TS1, TS2, TS3, and TS4. The leak detection unit 61 of the present embodiment acquires the temperature T by estimating the temperature T of the inactive space NA by the following mathematical formula (2).
T = (T1 + T2 + T3 + T4) / 4 ... (2)
That is, in the control device 60 of the present embodiment, the temperature T of the inactive space NA is the average of the temperatures T1, T2, T3, and T4.

When a leak occurs, the space between the outer peripheral surface of the inner pipe 3 and the inner peripheral surface of the outer pipe 4, that is, the pressure of the inactive space NA increases, so that the leak is detected by the inactive space A. Can be done.
The leak detection unit 61 determines the threshold value L in the case of the temperature T by the temperature T acquired by the mathematical formula (2) and the mathematical formula (1). The leak detection unit 61 has a function of comparing the pressure P measured by the pressure sensor PS with the threshold value L and determining that a gas leak has occurred when the pressure P is larger than the threshold value L. There is.

The leak detection unit 61 will be described with reference to the graph shown in FIG. The straight line shown by the alternate long and short dash line is a straight line based on the ideal gas state equation, and is a straight line P = (R / V) × T based on the ideal gas state equation PV = RT. The straight line L is a straight line according to the mathematical formula (1), and is a relational expression between the temperature T and the threshold value L.
When the points plotted by the temperature T and the pressure P are below the straight line L, the pressure P is determined to be a normal value. When the points plotted by the temperature T and the pressure P are above the straight line L, the pressure P is determined to be an abnormal value, and it is determined that a leak has occurred.

Next, the operation of the heat exchanger 1 of the present embodiment will be described.
Nitrogen gas NG is supplied to the first nitrogen gas chamber 13 from a nitrogen gas supply device (not shown) via the nitrogen gas supply port 22. The nitrogen gas NG supplied to the first nitrogen gas chamber 13 flows into the space between the outer peripheral surface of the inner pipe 3 and the inner peripheral surface of the outer pipe 4, and then is introduced into the second nitrogen gas chamber 14 to produce nitrogen. It is discharged from the gas discharge port 23.
The space inside the first nitrogen gas chamber 13, the inside of the second nitrogen gas chamber 14, and the space between the outer peripheral surface of the inner pipe 3 and the inner peripheral surface of the outer pipe 4 was filled with nitrogen gas NG, which is an inert gas. It becomes an inert space NA.

When the fuel gas FG is supplied to the first fuel gas chamber 12a through the fuel gas supply port 18, the fuel gas FG flows from one end 3a of the inner pipe 3 into the inside of the inner pipe 3 and then the other end of the inner pipe 3. It is introduced from 3b into the second fuel gas chamber 12b and discharged from the fuel gas discharge port 19.
When the air A is supplied to the air chamber 15 through the air supply port 20, the air A collides with the baffle plate 28, flows through the air chamber 15, and then is discharged from the air discharge port 21.
During this time, heat is exchanged between the fuel gas FG and the air A via the nitrogen gas NG, the fuel gas FG is heated, and the air A is cooled.

Next, a leak detection method for the heat exchanger of the present embodiment will be described.
The leak detection method of the heat exchanger includes a pressure measurement step S1 for measuring the pressure P of the inert space NA and a threshold calculation step S2 for acquiring the temperature T of the inert space NA and calculating the threshold L by the mathematical formula (1). And a comparison step S3 and a leak determination step S4.

In the pressure measurement step S1, the pressure sensor PS is used to measure the pressure P, which is the actual pressure of the inert space NA. The pressure P is transmitted to the control device 60.

In the threshold calculation step S2, the temperature sensors TS1, TS2, TS3, and TS4 are used to supply the temperature T1 of the gas flowing inside the fuel gas supply port 18, the temperature T2 of the gas flowing inside the fuel gas discharge port 19, and the air supply. The temperature T3 of the gas flowing inside the mouth 20 and the temperature T4 of the gas flowing inside the air discharge port 21 are measured. The temperatures T1, T2, T3 and T4 are transmitted to the control device 60.
The control device 60 acquires the temperature T using the mathematical formula (2) stored in the leak detection unit 61, and calculates the threshold value L using the mathematical formula (1).

In the comparison step S3, it is determined whether or not the pressure P is larger than the threshold value L.
When the pressure P is larger than the threshold value L, it is determined that a leak has occurred in the leak determination step S4.

According to the above embodiment, the leak can be detected at an early stage based on the temperature T and the pressure P of the inert space NA. Further, by continuously acquiring the pressure P and the temperature A of the inert space NA, it is possible to detect the leak even during the operation of the heat exchanger 1.
Further, by acquiring the temperature T of the inactive space NA as the average of the temperatures T1, T2, T3, and T4, it is possible to detect a leak even when it is difficult to measure the temperature of the inactive space NA.

Further, the presence of a nitrogen gas space, which is an inert space NA, between the space to which the fuel gas FG is supplied and the space to which the air A is supplied prevents the fuel gas FG and the air A from being mixed. be able to. That is, even if a problem occurs in one of the inner pipe 3 and the outer pipe 4 and the fluid leaks, the fuel gas FG is formed between the inner pipe 3 and the outer pipe 4 as an inert space NA. It is possible to prevent problems such as the mixture of air A and air A and an explosion.

Further, since the bend portion 27 of the inner pipe 3 is not fixed, the structure can be such that the thermal stress generated in the inner pipe 3 is not generated.

In the above embodiment, the temperature T is obtained from the average of the temperatures T1, T2, T3, and T4, but the present invention is not limited to this. For example, based on the theory of a heat exchanger, the above average may be multiplied by a coefficient in which a time delay is added, or the estimation accuracy may be improved by using the flow rate of gas, the heat capacity of the casing, or the like.

Further, in the above embodiment, the first fluid is the fuel gas FG and the second fluid is the air A, but the present invention is not limited to this. For example, the first fluid is an oxidant and the second fluid is an air A. It can be applied when it corresponds to a reducing agent.
Further, in the above embodiment, the space between the inner pipe 3, the inner pipe 3, and the outer pipe 4 is filled with nitrogen gas NG, but the space between the inner pipe 3, the inner pipe 3, and the outer pipe 4 is an inert space. It may be NA, and for example, a vacuum may be created between the inner pipe 3 and the inner pipe 3 and the outer pipe 4.

[Second Embodiment]
Hereinafter, the heat exchanger of the second embodiment of the present invention will be described in detail with reference to the drawings.
As shown in FIG. 4, the heat exchanger 1B of the present embodiment is a plate heat exchanger. The heat exchanger 1B of the present embodiment has a casing 50, a fuel gas flow section 55 through which the fuel gas FG flows, and an air flow section 56 through which the air A flows. The fuel gas flow section 55 and the air flow section 56 are portions partitioned in the casing 2 by a plurality of plates 51, 52, 53, 54.

The fuel gas flow unit 55 is formed by a first plate 51 and a second plate 52 facing the first plate 51. The fuel gas FG is supplied to the fuel gas distribution unit 55 through the fuel gas supply port 18D, and the fuel gas FG is discharged through the fuel gas discharge port 19D.

The air flow section 56 is formed by a third plate 53 and a fourth plate 54 facing the third plate 53. The air A is supplied to the air flow unit 56 through the air supply port 20D, and the air A is discharged through the air discharge port 21D.

Each of the plates 51, 52, 53, 54 is shaped so as to absorb the difference in heat elongation. The plates 51, 52, 53, 54 of this embodiment have a wavy shape. More specifically, the plates 51, 52, 53, 54 have a sinusoidal shape. The shapes of the plates 51, 52, 53, 54 may be any shape as long as they absorb the difference in thermal elongation, and may be, for example, a rectangular wave shape.

The second plate 52 of the fuel gas flow unit 55 and the third plate 53 of the air flow unit 56 are arranged so as to face each other. That is, the second plate 52 and the third plate 53 are not common plates, and the second plate 52 and the third plate 53 are arranged at intervals.

Nitrogen gas NG is supplied between the second plate 52 and the third plate 53 via the nitrogen gas supply port 22D. That is, an inactive space NA is formed between the second plate 52 and the third plate 53. Further, nitrogen gas NG is discharged from between the second plate 52 and the third plate 53 through the nitrogen gas discharge port 23D.

The heat exchanger 1B of the present embodiment has a plurality of temperature sensors TS1, TS2, TS3, TS4, a pressure sensor PS, and a control device, similarly to the heat exchanger 1 of the first embodiment. .. The control device has the same function as the control device 60 of the first embodiment.

According to the above embodiment, even in the plate heat exchanger, the leak can be detected at an early stage based on the temperature T and the pressure P of the inert space NA.
Further, the presence of a nitrogen gas space, which is an inert space NA, between the space to which the fuel gas FG is supplied and the space to which the air A is supplied prevents the fuel gas FG and the air A from being mixed. be able to. That is, even when a defect occurs in the plates 51, 52, 53, 54 and the fluid leaks, the fuel is provided as an inert space NA between the fuel gas flow section 55 and the air flow section 56. It is possible to prevent problems such as the gas FG and the air A mixing and exploding.
Further, since the plates 51, 52, 53, 54 have a wavy shape, not only heat transfer is promoted but also heat elongation difference can be absorbed.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment and includes design changes and the like within a range not deviating from the gist of the present invention. ..

1,1B Heat exchanger 2 Casing 3 Inner pipe 3s Outer pipe outer surface 4 Outer pipe 4s Inner peripheral surface of outer pipe 5 First dome part 6 Second dome part 7 Tube part 9 First pipe plate 10 Second pipe plate 11 Third pipe plate 12 Fuel gas chamber 12a First fuel gas chamber 12b Second fuel gas chamber 13 First nitrogen gas chamber 14 Second nitrogen gas chamber 15 Air chamber 16 Partition plate 18 Fuel gas supply port 19 Fuel gas discharge port 20 Air supply port 21 Air discharge port 22 Nitrogen gas supply port 23 Nitrogen gas discharge port 25 First straight part 26 Second straight part 27 Bend part 28 Baffle plate 50 Casing 51 First plate 52 Second plate 53 Third plate 54 Fourth plate 55 Fuel gas flow section 56 Air flow section 60 Control device 61 Leak detector A Air IS Inside the inner pipe PS pressure sensor TS Temperature sensor FG Fuel gas NA Inactive space NG Nitrogen gas

Claims (5)

The first distribution section, which has the first heat transfer surface and through which the first fluid flows,
A second heat transfer surface that has a second heat transfer surface facing the first heat transfer surface, has an inert space between the first heat transfer surface, and a second fluid different from the first fluid flows through the second. It is a leak detection method for a heat exchanger equipped with a distribution unit.
A pressure measuring step for measuring the pressure in the inert space, and
A threshold calculation step of acquiring the temperature of the inactive space and calculating a threshold based on the temperature.
It has a leak determination step of determining that a leak has occurred when the pressure is larger than the threshold value .
In the threshold calculation step, the temperature is the temperature of the first fluid supplied to the first flow section, the temperature of the first fluid discharged from the first flow section, and the second flow section. A leak detection method for a heat exchanger calculated based on the temperature of the second fluid supplied and the temperature of the second fluid discharged from the second flow unit . In the threshold calculation step, the temperature is the temperature of the first fluid supplied to the first flow section, the temperature of the first fluid discharged from the first flow section, and the second flow section. The leak detection method for a heat exchanger according to claim 1, wherein the temperature of the second fluid supplied and the temperature of the second fluid discharged from the second flow unit are averaged. In the threshold calculation step, the temperature is the temperature of the first fluid supplied to the first flow section, the temperature of the first fluid discharged from the first flow section, and the second flow section. The first aspect of claim 1, which is calculated by multiplying the average of the temperature of the second fluid supplied and the temperature of the second fluid discharged from the second flow unit by a coefficient with a time delay added. How to detect leaks in heat exchangers. In the threshold calculation step, the temperature is the temperature of the first fluid supplied to the first flow section, the temperature of the first fluid discharged from the first flow section, and the second flow section. A claim calculated based on the temperature of the second fluid supplied, the temperature of the second fluid discharged from the second flow unit, the flow rate of the second fluid, and the heat capacity of the casing. Item 1. The method for detecting a leak in a heat exchanger according to Item 1. The heat exchanger is
A cylindrical casing having a first supply port to which the first fluid is supplied and a first discharge port to which the first fluid is discharged.
An inner pipe that extends so as to pass through the internal space of the casing and through which the second fluid flows inside.
It has an outer tube that accommodates the inner tube inside so as to pass through the inner space and extends in the extending direction of the inner tube, and has an inactive space between the inner tube and the inner tube.
The first heat transfer surface is the inner peripheral surface of the outer tube.
The leak detection method for a heat exchanger according to any one of claims 1 to 4, wherein the second heat transfer surface is an outer peripheral surface of the inner pipe.

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