JP2000180092A - Heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heat exchanger in which leakage is minimized, if any, heating side fluid is prevented from being mixed with fluid on the side to be heated and detection of leakage is facilitated by providing a buffer channel between a heating side channel and a channel on the side to be heated and providing the buffer channel with a leak detection mechanism. SOLUTION: A buffer channel 23 is provided between the heating side channel 20 and the channel 21 on the side to be heated of a plate fin type heat exchanger. These channels are sectioned by means of a tube plate 25 and a spacer 26 having different shape from channel to channel. A corrugated fin 28 is brazed to the tube plates 25 on the opposite sides in the channel between the tube plates 25. The buffer channel 22 is provided is provided with a pressure gauge which can measure pressure variation on line. According to the structure, leaked fluid, if any, stands in the buffer channel 22 and heating side fluid is prevented from being mixed with fluid on the side to be heated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger capable of safely exchanging heat for a fluid such as a flammable substance or a poison that is not desired to leak from a flow path.

[0002]

2. Description of the Related Art For example, Japanese Unexamined Patent Publication No. Hei 10-47080 describes a heat exchange between flammable liquefied natural gas (hereinafter, referred to as LNG) and compressed air. In order to avoid this, it has been proposed to perform heat exchange with a nonflammable intermediate refrigerant interposed. In addition,
Japanese Patent Application Laid-Open No. 9-279132 discusses a nonflammable refrigerant for heat exchange with LNG.

[0003]

In the above two known examples, a nonflammable intermediate refrigerant is assumed for heat exchange with combustible LNG. However, when an intermediate refrigerant is used, the refrigerant is circulated. In addition to the need for a mechanism, the temperature range for the refrigerant being a liquid is also limited, and there is a problem that handling is difficult.

An object of the present invention is to provide a heat exchanger for exchanging a fluid that is not desirable to leak, such as a flammable substance or a poison, in order to minimize the amount of leak if there is a leak. Another object of the present invention is to provide a heat exchanger having a structure capable of preventing mixing of a heating-side fluid and a heated-side fluid and of easily detecting leakage.

[0005]

In the heat exchanger, a buffer passage is provided between the heating-side passage and the heated-side passage. If a leak occurs in the heating-side flow path or the heated-side flow path, the leaked fluid is discharged to the adjacent buffer flow path and does not mix with the fluid of the partner on which heat exchange is performed. By providing a leak detection mechanism in this buffer channel, leak detection can be performed. As the leak detection mechanism, for example, a pressure measuring element or a gas component analyzing element is provided.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIG. 2 shows an embodiment of an LNG cold-heat utilization type gas turbine power generation system equipped with a heat exchanger according to claims 1 and 2 of the present invention.
The main components of the present invention are compressors 51 and 52 for compressing air to high pressure, a combustor for burning compressed air and fuel such as LNG, and a gas turbine driven by expansion of high-temperature and high-pressure combustion gas. 7, a generator 8 disposed on the same axis as the gas turbine 7, and a regenerative heat exchanger 9 for recovering heat of exhaust gas from the gas turbine 7.

[0007] The main components of the embodiment are as follows.
Heat exchangers 60 and 61 for exchanging heat between the compressed air and LNG supplied from the LNG storage tank 43 via the pipe 40. In this embodiment, the heat exchangers 60 and 61
As shown in FIG. 1, a plate fin type is assumed, and a buffer fluid channel 22 is provided between a heated fluid channel 20 and a heated fluid channel 21.

As shown in FIGS. 3A to 3C, these flow paths are partitioned by a tube plate and a spacer 26 having a different shape for each flow path. Corrugated fins 28 are brazed to the tube plates on both sides in the flow path sandwiched between the tube plates, and have an effect of increasing the heat transfer area and increasing the rigidity of the tube plate. The tube plate 25 and the spacer 26 are joined by welding, and the mounting positions of the header 27 communicating with the flow path are all set in different directions as shown in FIG. 4, so that leakage between the flow paths basically occurs. It does not have a structure.

In addition, in the present embodiment, the buffer fluid passage 2
2, a pressure gauge 30 is installed so that a pressure change in the buffer fluid flow path 22 can be measured online, and even if a leak occurs, it can be detected. Also,
Even if a leak occurs, the leaked fluid will
There is no possibility that the fluid on the heating side and the fluid on the heated side stay in the buffer fluid stream 22 and mix.

The normal operation of this embodiment will be described with reference to the drawings. The normal-temperature air supplied to the heat exchanger 60 by the air blower 80 passes through the heating-side fluid flow path 20 of the heat exchanger 60. At the same time, the temperature of about -16
The 2 ° C. LNG is supplied to the heated fluid passage 21 of the heat exchanger 60.
Pass through. At this time, the corrugated fin 28 of the air-heating-side fluid flow path 20 to the tube plate 25 to the corrugated fin 28 of the buffer fluid flow path 22 to the tube plate 2
Heat is generated and heat is exchanged in a path from the corrugated fin 28 to the natural gas of the fluid channel 21 to be heated 21.

In this embodiment, the corrugated fins 28 are all made of aluminum having good heat conductivity, and have a very large surface area per unit volume. The overall thermal resistance is small due to the use of thick ones. The air is-
It is cooled down to about 135 ° C.
Compressed to about atmospheric pressure. At this time, since the air that has been cooled and has a high density is compressed, the air can be compressed with very little power as compared with compressing air at room temperature to about 7 atm. The temperature of the compressed air rises to about 10 ° C. The air is caused to flow into the heating-side fluid flow path 20 of the heat exchanger 61, and by the same operation as the heat exchanger 60, the air flow becomes −13 again.
Cool to about 0 ° C.

The natural gas heated by the heat exchangers 60 and 61 has a temperature of about 0 ° C. at the outlet of the present system, but is supplied to another system via a pipe 42 and adjusted to a required temperature for use. You. The low-temperature air of about 7 atm passed through the heat exchanger 61 is further compressed by the compressor 52 to about 46 atm. Also at this time, it is possible to compress with very little power as compared with compressing air at room temperature. The compressed high-pressure air at a temperature of about 0 ° C. is regenerated by the regenerative heat exchanger 9.
The fuel is heated to about 280 ° C. and burned in the combustor 5 together with the fuel 50 such as LNG.

In the gas turbine 7, the generator 8 is driven by the expansion force of the high-temperature and high-pressure combustion gas to generate electric power. The exhaust gas of the gas turbine 7 is recovered by the regenerative heat exchanger 9 and discharged from the stack 55 to the atmosphere.
The feature of this system is that by using the cold energy possessed by LNG, the power of the air compressor, which normally consumes 50 to 60% of the gas turbine output, can be greatly reduced, resulting in a large power generation output. Can be increased.

Next, the operation of this embodiment in the event that a leak occurs in the heat exchanger 60 or 61 will be described. In the present embodiment, the buffer fluid flow path 22 includes:
Fill with noncombustible nitrogen. The filling pressure is determined in consideration of the pressures at the minimum use temperature and the maximum use temperature. However, it is desirable that the pressure does not become negative even if contracted at a low temperature. For example, it is set to about 5 atm at normal temperature. Assume that one of the tube plates is damaged. If the pressure in the buffer fluid channel 22 is higher than the pressure between the damaged channels, nitrogen gas flows out of the buffer fluid channel into the compressed air or natural gas channel. On the other hand, the buffer fluid passage 2
If the pressure of the second is lower than the pressure between the damaged channels, compressed air or natural gas flows into the nitrogen-filled buffer fluid channel.

These flow phenomena are caused by the buffer fluid passage 22
Ends as soon as the pressure of
Compressed air and natural gas do not mix. When the flow of the buffering fluid occurs, the pressure in the buffering fluid passage 22 asymptotically approaches a value equal to the pressure of the compressed air or the pressure of the natural gas. Therefore, the pressure gauge is monitored during the operation of the plant. If it is, the leak can be detected quickly. Further, even after the plant is stopped, the pressure of the buffer fluid passage 22 is
The value becomes different from the initial nitrogen filling pressure, and the leak can be reliably detected.

(Embodiment 2) FIG. 5 shows an embodiment of an LNG cold-heat utilization type gas turbine power generation system provided with a heat exchanger according to claims 1 and 2 of the present invention. In the present embodiment, as shown in FIG. 6, cylindrical heat exchangers 60 and 61 are assumed to be of a cylindrical triple tube type. The heated-side fluid flow path 21 through which LNG flows is the innermost flow path, the heated-side fluid flow path 20 through which compressed air flows is disposed at the outermost periphery, and the buffering fluid flow path 22 is located in the middle of these. Fins 29 are provided in the heating-side fluid flow path 20 and the heated-side fluid flow path 21 to promote heat transfer. Buffer fluid channel 22
Is provided with a spacer 26 made of a metal having good heat conductivity to promote heat transfer between the compressed air and LNG.

The difference between this embodiment and the embodiment described with reference to FIG. 2 is that a gas component analyzer 31 is provided in place of the pressure gauge 30 in the buffer fluid flow path 22. Further, in this embodiment, the pressure of the nitrogen gas to be charged into the buffer fluid flow path 22 is set to be low, and in the event that a leak occurs in the heat exchanger 60 or 61, the compressed air or natural gas is supplied to the buffer fluid flow path. Designed to flow into the road. When a leak occurs, the air component or the natural gas component is mixed into the buffer fluid flow path, so that the gas component ratio indicated by the gas component analyzer 31 changes, and the leak can be detected quickly.

In this embodiment, the buffer fluid passage 22 is filled with a gas, but it may be filled with a porous solid such as a sintered metal. In that case, heat conduction in the porous material promotes heat transfer. The operation in which the gas existing in the porous gap acts on the detection of leakage is the same as in the above-described embodiment.

As another form of this embodiment, a heat exchanger 60
And 61, a plate fin and tube type as shown in FIG. 7 can be applied. In a normal plate-fin-and-tube heat exchanger, the fluid to be heat-exchanged flows through the shell side and the tube side, respectively.
In the present invention, as shown in FIG. 7, a part of the tube is used as the heating-side fluid flow path 20, the remaining tube is used as the heated-side fluid flow path 21, and a buffering fluid flow path 22 is provided on the shell side. The tubes of the heating-side fluid flow path 20 and the heated-side fluid flow path 21 are alternately arranged and connected by a large number of fins 29, so that good heat transfer performance between the fluids can be obtained. . In the event that leakage occurs in either of the tubes, it flows out into the buffer side fluid flow path 22 on the shell side, and by the same operation as in the above embodiment, mixing of the heating side fluid and the heated side fluid is prevented, thereby preventing leakage. Can be detected.

Although not shown, the present invention can be applied to other types of heat exchangers, such as a plate type heat exchanger.

As described above, the embodiments of the LNG cold heat power generation system equipped with the heat exchanger according to the present invention have been described in the two embodiments. However, the present invention uses liquid air, for example, in addition to these. The present invention is applicable to all systems that exchange heat between LNG and air, such as an energy storage and power generation system.

[0022]

According to the present invention, since the heat exchanger is provided with a buffering flow path in addition to the heating-side fluid flow path and the heated-side fluid flow path, flammable substances and poisons leak. In the case of exchanging heat with a fluid that is not desirable, the amount of leakage can be minimized, and mixing of the heated fluid and the heated fluid is prevented. In addition, by installing a pressure gauge or a gas component analyzer in the buffer channel, it is possible to easily detect leakage. By applying the present invention to the heat exchanger of the LNG cold energy utilization system, a safe LNG cold energy utilization system can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view of a plate-fin heat exchanger according to the present invention.

FIG. 2 is a schematic diagram of a system according to an embodiment of the present invention.

FIGS. 3A to 3C are cross-sectional views showing a configuration example of a tube plate of a heat exchanger according to the present invention.

FIG. 4 is an external view of a plate-fin heat exchanger according to the present invention.

FIG. 5 is a schematic diagram of a system according to an embodiment of the present invention.

FIG. 6 is a sectional view of a flow channel of the cylindrical triple tube heat exchanger according to the present invention.

FIG. 7 is a perspective view of a plate fin-and-tube heat exchanger according to the present invention.

[Explanation of symbols]

Reference numeral 5: combustor, 7: gas turbine, 8: generator, 9: regenerative heat exchanger, 20: heating-side fluid channel, 21: heated-side fluid channel, 22: buffering fluid channel, 25: tube Plate, 26 spacer, 27 header, 28 corrugated fin, 29 fin, 30 pressure gauge, 31 gas component analyzer, 41 pump, 42 pipe, 43 LNG storage tank, 51, 52 compression Machine, 55 ... stack, 60,
61: heat exchanger, 80: air blower.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Mitsugu Nakahara 7-2-1, Omika-cho, Hitachi City, Ibaraki Prefecture F-term in the Electric Power & Electronics Development Division, Hitachi, Ltd. 2F030 CB02 CC11 CF20 2G067 AA12 AA34 BB11 DD02

Claims (2)

[Claims] 1. A heat exchanger, further comprising a buffering flow path in addition to a heating-side fluid flow path and a heated-side fluid flow path. 2. The heat exchanger according to claim 1, further comprising a leak detecting mechanism in the buffer passage.