JP2000227031A - Air cooler for gas turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent heating and damage to a heat transfer pipe due to flow rate reduction, by stabilizing the flow of cooling water flowing in the pipe, in a cooler for cooling air in a gas turbine. SOLUTION: Cooling water, from an outside boiler facility from a cooling water line 90, is supplied to an air cooler 80 by a pump 82 via an opening/ closing valve 83, to cool air from a cooling air line 88, and the air is supplied to a gas turbine 81 from a line 89, and the cooling water is made to flow out via an opening/closing valve 86. When the cooling water is reduced due to the running condition on a boiler facility side to derease flow rate flowing into the cooler 80, a control device 1 inputs the signals of flowmeters 3 and 4 to detect this condition, to increase the opening of a recirculating valve 2, and the water is returned from a recirculating line 5 to increase the flow rate of the water inflowing into the cooler 80, to suppress a flow rate variation in a heat transfer pipe, thereby preventing the heating and damage to the pipe due to the flow rate reduction in the pipe.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas turbine air cooler, which stabilizes the flow rate of cooling water to a cooler to prevent boiling in a heat transfer pipe due to insufficient flow rate of cooling water. The heat transfer tube is prevented from being damaged.

[0001]

2. Description of the Related Art A gas turbine performs work by flowing high-temperature combustion gas from a combustor through a gas path formed between a moving blade attached to a periphery of a rotor and a stationary blade fixed to a casing side. Rotate the rotor. Therefore, since the rotor and the blades are exposed to the high-temperature gas, they are cooled by air during operation, and therefore, an air cooler is provided. The air cooler requires cooling water to cool the air from the compressor to an appropriate temperature, and this cooling water may be derived from another equipment independent of the gas turbine plant, such as a boiler equipment.

FIG. 5 is a system diagram of the air cooler described above, wherein reference numeral 80 denotes an air cooler, and 81 denotes a gas turbine. The air cooler 80 is provided with air cooling lines 88 and 89 communicating with each other. The line 88 cools the rotor and blades of the gas turbine 81 and guides the air whose temperature has risen to, for example, about 400 ° C. To be cooled by the cooling water in the air cooler 81 and the cooling air from the cooling air line 89.
For example, cooling air of about 200 ° C. is supplied to the gas turbine 81 to cool the rotor and the blades.

As described above, the cooling water is supplied from the boiler facility or the like to the air cooler 80 through the water supply line 90 by the pump 82 via the on-off valve 83, and flows through the heat transfer tube communicating with the inside thereof. The surrounding air is cooled and flows out through the on-off valve 86. At this time, the flow rate control valve 84 is manually adjusted to adjust the amount of cooling water flowing in the air cooler 80, and the flow rate control valve 85 is manually adjusted to adjust the flow rate of the cooling air and the cooling air flowing into the gas turbine 81. The temperature is adjusted.

FIGS. 6, 7 and 8 show various examples of installation of an air cooler. In FIG. 6, reference numeral 80a denotes a U tube of the air cooler 80, 80b denotes a water chamber, and 80c denotes a cooling water inlet. , 80d are cooling water outlets, and cooling water 100 is
0b, it flows into the U tube 80a, cools the surrounding air, and flows out from the cooling water outlet 80d. FIG.
In the above, the air cooler 80 having such a structure is arranged in a horizontal manner, and two sides of the U-tube are arranged at an angle nearly vertically and vertically.

FIG. 7 shows an air cooler 80 having the same structure as a vertical type.
That is, FIG. 8 shows an example in which the water chamber 80b is installed at the bottom, and FIG. 8 shows an example in which the air cooler 80 having the same structure is arranged vertically, but the water chamber 80b is arranged at the top.

[0006]

In the conventional system of the air cooler 80 shown in FIG. 5, a water supply line 90 is incorporated into a water supply system from a boiler facility or the like independent of a gas turbine 81, and the water supply The volume is controlled by the capacity of the boiler equipment. Therefore, depending on the demand for water in the boiler facility, the amount of cooling water may decrease, and the amount flowing to the cooling water line 90 may decrease. In such a case, the flow rate in the heat transfer tube of the air cooler 80, that is, the flow rate in the U-tube may be significantly reduced, and the flow in the pipe may be unstable or, in extreme cases, the flow rate may be "0". sell. Further, in such a case, boiling occurs in the tube, the flow instability becomes more and more severe, and when the dryout occurs, the heat transfer tube may be damaged.

In the arrangement of the air coolers 80 as shown in FIGS. 6, 7 and 8, the flow of the cooling water flowing in the tubes tends to be unstable depending on the arrangement and angle of each U tube 80a. In some cases, the flow may be "0", and in such a case, there is a high possibility that the heat transfer tube is broken, and the flow of the cooling water is constantly stabilized in the heat transfer tube. There was a desire for a device to make it flow.

Therefore, in the present invention, the cooling water for the air cooler for obtaining the cooling air for the gas turbine is obtained from an independent facility other than the gas turbine plant, and the supply of the cooling water is restricted. In order to constantly stabilize the flow state flowing through the heat transfer tubes in the air cooler, a gas turbine cooling air cooler that can always flow a fixed amount of water to the heat transfer tube group and does not cause damage to the heat transfer tubes It was made to provide.

[0009]

The present invention provides the following means (1) to (4) to solve the above-mentioned problems.

[0010] (1) Cooling water is supplied from the external equipment of the gas turbine to the heat transfer tube group inside the cooler main body and flows therethrough to cool the air around the heat transfer tube group and supply it as gas turbine cooling air. In the air cooler of the turbine, a recirculation line connected from the middle of the cooling water outlet side flow path to the inlet side flow path of the heat transfer tube group, a recirculation valve provided in the middle of the recirculation line, A first flow meter provided on the downstream side of the recirculation line connection portion of the water outlet side flow path;
A second flow meter provided in the recirculation line, and a control device that captures detection signals from the first and second flow meters and controls an opening of the recirculation valve. Characteristic air cooler for gas turbine.

(2) The air cooler comprises two systems,
The cooling water inlet side and the outlet side of each system are provided with on-off valves, respectively, and the control device controls the on-off valves to supply cooling water to one of the two systems and supply the cooling water to the gas turbine. The air cooler for a gas turbine according to (1), wherein the air cooler is controlled to supply cooling air.

(3) A cooling water tank connected to external equipment of the gas turbine, a supply system for supplying cooling water from the cooling water tank to the heat transfer tube group inside the cooler main body, and provided in the middle of the supply system. A flow control valve, a path for supplying cooling water from the cooling water tank to the heat transfer tube group, a standby pump provided on the same path, and a cooling water outlet from the cooling water outlet side passage of the heat transfer tube group. A recirculation line connected to the tank, a recirculation valve provided in the middle of the recirculation line, and a first flow rate provided downstream of the recirculation line connection of the cooling water outlet side flow path A second flow meter provided on the upstream side of the recirculation line connection portion of the cooling water outlet flow path; and a detection signal of the first and second flow meters. Control the opening of the flow control valve and the recirculation valve Rutotomoni, air cooler of a gas turbine and controlling the driving of the standby pump.

(4) Cooling water is supplied from the external equipment of the gas turbine to the heat transfer tube group inside the cooler main body and flows therethrough to cool the air around the heat transfer tube group and supply it as gas turbine cooling air. In the air cooler for a turbine, the heat transfer tube group is constituted by a plurality of U-shaped tubes, and a pair of communicating tubes of each U-shaped tube is arranged to be on the same horizontal plane. Turbine air cooler.

In (1) of the present invention, when the amount of cooling water flowing in the air cooler decreases, the controller detects this condition with the first flow meter and increases the opening of the recirculation valve to increase the amount of cooling water. The detected value of the flow meter 2 is monitored to increase the amount of cooling water flowing into the air cooler from the recirculation line, and control is performed so that the amount of cooling water flowing in the heat transfer tube group is constantly constant. By controlling the cooling water amount in this way, the flow state in the heat transfer tube group is stabilized, and the heat transfer tubes can be prevented from being broken without boiling in the tubes due to a decrease in flow rate or dryout.

In (2) of the present invention, the air cooler is composed of two systems, and each system is provided with an opening / closing valve on the inlet side and the outlet side, and their opening and closing are controlled by a control device. The two systems are switched by the control device and only one of them is operated. The control device also controls the flow of the cooling water to the air cooler during operation in the same manner as in (1) above so as to reduce the fluctuation. When operating the air cooler, the corresponding one of the inlet / outlet open / close valves is opened, the other open / close valve is closed, and only one is operated. When switching from one cooler to the other cooler during operation, control is performed to open and close the corresponding on-off valves in the opposite manner as described above. In (2) of the present invention, one can be operated and the other can be used for backup, so that even if one fails, the other can be operated and continuous operation is possible. Thus, fluctuations of the cooling water flowing in the heat transfer tube group can be suppressed, and damage to the tube due to boiling in the tube due to a decrease in the flow rate can be prevented.

In (3) of the present invention, normally, the flow control valve is opened, and the cooling water is supplied to the air cooler within a range in which a required flow to the boiler equipment can be secured. The control of the supply amount is performed by the control device taking in the signal from the first flow meter,
The opening of the flow control valve is controlled to control the amount of cooling water flowing in the heat transfer tube group of the air cooler to be constant. Also, the control device takes in a signal from the second flow meter, controls the opening of the recirculation valve based on the signal, and transfers a part of the cooling water flowing out of the air cooler into the cooling water tank by the bypass line. And control to balance outflow.

In such a state, when the operating conditions of the boiler equipment fluctuate, the amount of water in the cooling water tank decreases, and when the supply of cooling water to the air cooler falls below a certain value, the control device operates the recirculation valve. Control to increase the opening, increase the return amount of cooling water from the bypass line, and operate the standby pump to supply water from the cooling water tank to reduce the supply amount of cooling water to the air cooler. Control so that it does not drop extremely. Also in the invention of (3), the flow state of the cooling water in the heat transfer tube group in the air cooler is stabilized, and the heat transfer tube can be prevented from being damaged without boiling or dryout in the tube due to a decrease in the flow rate. Things.

In (4) of the present invention, the conventional air cooler is arranged so that the U-shaped pipe is horizontal for the purpose of removing a vertical flow portion in which the flow rate in the heat transfer tube group is likely to be unstable. I have. Therefore, in the U-shaped pipe, the flow of the cooling water is all horizontal, so that even when the flow rate of the cooling water is reduced, a stable flow is generated by the horizontal flow in the U-shaped pipe, and the flow is prevented from fluctuating. This can prevent damage due to overheating.

[0019]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a system diagram of a gas turbine cooling air cooler according to a first embodiment of the present invention. In the figure, reference numerals 80 to 90 have the same functions as those of the conventional example shown in FIG. 5 and therefore, detailed description is omitted, and the description is referred to as it is. This is the part shown and will be described in detail below.

In FIG. 1, reference numeral 1 denotes a control unit, and 2 denotes a recirculation valve, which is provided in the middle of a recirculation line 5 and adjusts the amount of cooling water to be recirculated. Reference numeral 3 denotes a flow meter for measuring a flow rate of a cooling water outflow passage.
Is also a flow meter, which measures the flow rate of the cooling water in the recirculation line 5.

In the above configuration, the cooling water is supplied to the cooling water line 90 from the boiler equipment, the operating conditions on the cooling water supply side change, the demand for water on the boiler side decreases, and the cooling water line 90 A decrease in the amount of water supplied to the system occurs.

In this case, the amount of cooling water to the air cooler 80
Decreases, the detection value of the flow meter 3 decreases. Control equipment
The device 1 takes the value detected by the flow meter 3 and the value detected by the flow meter 4.
And the detection value of the flow meter 4 in the recirculation line 5 increases.
Control to increase the opening of the recirculation valve 2.
You. That is, the control device 1 sets the flow rate of the outflow side cooling water to G ₁
And the flow rate of the recirculation line 5 is G_TwoThen G₁+ G
_Two= Control the opening of the recirculation valve 2 so as to be constant
You.

According to the first embodiment, the amount of water in the cooling water line 90 decreases, and the amount of cooling water flowing in the air cooler 80 decreases. The controller 1 detects this state from the flow meter 3, increases the opening of the recirculation valve 2, monitors the detection value of the flow meter 4, and determines the amount of cooling water flowing from the recirculation line 5 to the air cooler 80. It is controlled so that the amount of cooling water flowing in the heat transfer tube is constantly constant. By such control, the flow state in the heat transfer tube is stabilized, and the heat transfer tube can be prevented from being broken without boiling or dryout in the tube due to a decrease in the flow rate.

FIG. 2 is a system diagram of a gas turbine cooling air cooler according to a second embodiment of the present invention. In the figure,
Reference numerals 80 to 90 are the same as those shown in FIG. 1, and thus detailed description is omitted and will be referred to as they are. However, the characteristic portions of the present invention are those indicated by reference numerals 10 to 17 and will be described in detail below. .

In FIG. 2, reference numeral 10 denotes a control device,
Reference numeral 1 denotes a flow meter for the cooling water discharged from the air cooler 80. 1
2 is a cooling water flow control valve on the inlet side of the air cooler 80, 13
Is an on-off valve for a line 16 provided in parallel with the flow control valve 12, and 14 is a standby pump also provided on the line 16. Reference numeral 15 denotes a tank, which is connected to a cooling water line 90 connected to a boiler facility or the like, so that a required amount of water for the boiler facility is supplied from the tank.

In the tank 15, a recirculation line 5, a line 16, and a supply line 17 are connected. A part of the cooled water is returned from the recirculation line 5 to the tank 15, and the water in the tank 15 is supplied from the supply line 17 to the air cooler 80 through the pump 82, the flow control valve 12, and the on-off valve 83. When the cooling water is insufficient, the standby pump 14 is operated through the line 16, and the cooling water flows from the tank 15 to the air cooler 80 through the on-off valve 13.

In the above arrangement, the flow control valve 1
2 is opened, the pump 82 is operated, and the cooling water is supplied to the air cooler 80 within a range where the required flow rate to the boiler equipment can be secured. The control of the supply amount is performed by the control device 10 by the flow meter 3.
To control the opening of the flow control valve 12,
Control is performed so that the amount of cooling water flowing in the heat transfer tube of the air cooler 80 is constant. Further, the control device 10 receives a signal from the flow meter 11 and controls the opening degree of the recirculation valve 2 based on the signal, and controls a part of the cooling water flowing out of the air cooler 80 into the tank 15. Return from recirculation line 5, tank 1
Control is performed to balance the inflow and outflow from 5.

In the above-described cooling water supply state, operating conditions on the boiler equipment side fluctuate, the amount of water in the tank 15 decreases, and the supply of cooling water to the air cooler 80 by the pump 82 falls below a certain value. In the state, the control device 10 controls the recirculation valve 2 to increase the opening thereof,
The return amount of the cooling water from the tank 15 is increased, the on-off valve 13 is opened, the standby pump 14 is operated, the water from the tank 15 is supplied from the line 16, and the supply amount of the cooling water to the air cooler 80 is extremely low. Control so that it does not decrease. Also in the second embodiment, the flow state of the cooling water in the heat transfer tubes in the air cooler 80 is stable, and the heat transfer tubes can be prevented from being damaged without boiling or dryout in the tubes due to a decrease in the flow rate. Things.

FIG. 3 is a system diagram of a gas turbine cooling air cooler according to a third embodiment of the present invention. In the system shown in FIG. 3, two systems of the first embodiment shown in FIG. 1 are provided, one of the air coolers is operated at all times, and the other is put on standby for backup, and one of the systems is broken down.
Alternatively, in the case of periodic inspection, switching is performed so that continuous operation can be performed.

In FIG. 3, the air cooler 80 is (A),
1B, each of which has the same configuration as that shown in FIG. 1. These two systems are switched by the control device 20 and only one of the air coolers 80 is operated. Each system has an on-off valve 21 (A), 2
1 (B) is an on-off valve 22 (A), 22 (B) on the outlet side.
However, switching valves 23 (A) and 23 (B) are further provided in a system of cooling air to the gas turbine 81, and the opening and closing of the switching valves are controlled by the control device 20.

The control unit 20 controls the flow of the cooling water to the air cooler 80 in the same manner as in the system shown in FIG. 1 so as to reduce the fluctuation of the flow of the cooling water. The valves 21 (A) and 22 (A) are opened, and the on-off valve 2
1 (B) and 22 (B) are closed, and the switching valves 23 (A) and
23 (B) is switched to the system on the side of the air cooler 80 (A), and when the air cooler 80 (B) is operated, the on-off valves 21 (A) and 22 (A) are closed. , 21
(B), 22 (B) are opened, and the switching valves 23 (A), 23
Control is performed so that (B) is switched to the system on the side of the air cooler 80 (B).

According to the third embodiment, since two systems of the air coolers 80 (A) and 80 (B) are provided, one of them can be operated at all times and the other can be used as a backup. Even if one fails, it is possible to continuously operate the other by operating the other, and to suppress the fluctuation of the cooling water flowing in the heat transfer tube as in the first and second embodiments, and to reduce the flow rate by the boiling in the tube. The pipe can be prevented from being damaged.

FIG. 4 shows a layout of heat transfer tubes of a gas turbine cooling air cooler according to a fourth embodiment of the present invention.
FIG. 6B is a front view, and FIG. 6B is a side view. In the fourth embodiment, the conventional air cooler 80 shown in FIGS. In order to remove a flow portion, the U-tube 80a is arranged so as to be horizontal.

For this purpose, the water chamber 80b is arranged horizontally on the base 30 in the direction in which the U tubes 80a are horizontal, and the flow of the cooling water is all horizontal in the U tubes 80a, thereby reducing the flow rate of the cooling water. Even if U tube 8
Within 0a, a stable flow is generated by the horizontal flow, fluctuation of the flow is prevented, and breakage due to heating of the tube can be prevented.

[0035]

The air cooler of the gas turbine according to the present invention has the following features.
(1) Cooling water is supplied from an external facility of the gas turbine to a heat transfer tube group inside the cooler main body and flows therethrough to cool air around the heat transfer tube group and supply it as gas turbine cooling air. In the cooler, a recirculation line connecting the cooling water outlet side flow path of the heat transfer tube group to the inlet side flow path, a recirculation valve provided in the middle of the recirculation line, the cooling water outlet side A first flow meter provided on the downstream side of the recirculation line connection portion of the flow path, a second flow meter provided on the recirculation line, and a first flow meter provided from the first and second flow meters. A control device for receiving the detection signal and controlling the opening of the recirculation valve. With this configuration, the controller detects the instability of the amount of cooling water in the heat transfer tube group with the first flow meter, and controls the recirculation valve of the recirculation line to increase the amount of cooling water flowing into the air cooler. Thus, the amount of cooling water flowing in the heat transfer tube group is controlled so as to be constantly constant. By controlling the amount of cooling water in this way, the flow state in the heat transfer tube group is stabilized, and the heat transfer tubes can be prevented from being broken without boiling or dryout in the tubes due to a decrease in the flow rate.

According to a second aspect of the present invention, in the first aspect of the present invention, the air cooler comprises two systems, and each system has an opening / closing valve on each of a cooling water inlet side and an outlet side, and The apparatus controls the on-off valves to supply cooling water to one of the two systems and supply cooling air to the gas turbine. With such a configuration, one of the air coolers can be operated, and the other can be used as a backup. Therefore, even if one of the air coolers fails, the other can be operated to perform continuous operation. Similarly, fluctuation of cooling water flowing in the heat transfer tube group can be suppressed, and damage to the tube due to boiling in the tube due to a decrease in flow rate can be prevented.

(3) The present invention provides a cooling water tank connected to external equipment of a gas turbine, a supply system for supplying cooling water from the cooling water tank to a heat transfer tube group inside the cooler body,
A flow control valve provided in the middle of the supply system, a path for supplying cooling water from the cooling water tank to the heat transfer tube group and a standby pump provided on the same path, and a cooling water outlet side of the heat transfer tube group A recirculation line connected to the cooling water tank from the middle of the flow path, a recirculation valve provided in the middle of the recirculation line, and a downstream side of the cooling water outlet side flow path from the recirculation line connection portion. A first flow meter provided in the
A second flow meter provided on the upstream side of the recirculation line connection part of the cooling water outlet side flow path, and detection signals of the first and second flow meters are taken in, and flow rate adjustment of the supply line is performed. The opening of the valve and the recirculation valve is controlled, and the driving of the standby pump is controlled. With such a configuration, when the operating conditions on the boiler equipment side fluctuate, the amount of water in the cooling water tank decreases, and when the supply of cooling water to the air cooler falls below a certain value, the control device determines the opening of the recirculation valve. To increase the amount of cooling water returned from the recirculation line, and operate the standby pump to supply water from the cooling water tank and reduce the amount of cooling water supplied to the air cooler. By controlling so that it does not decrease, the flow state of the cooling water in the heat transfer tube group is stabilized, and boiling and dryout in the tube due to the decrease in flow rate do not occur,
This can prevent the heat transfer tube from being damaged.

According to (4) of the present invention, cooling water is supplied from an external facility of a gas turbine to a heat transfer tube group inside a cooler main body and flows therethrough to cool air around the heat transfer tube group, thereby cooling the gas turbine. In the air cooler of a gas turbine supplying as air, the heat transfer tube group is composed of a plurality of U-shaped tubes, and a pair of communicating tubes of each U-shaped tube is arranged to be on the same horizontal plane. It is characterized by. With such a configuration, the flow of the cooling water is all horizontal, and even when the flow rate of the cooling water is reduced, a stable flow is generated by the horizontal flow in the U-shaped pipe, and the flow is prevented from fluctuating. It can prevent breakage due to heating.

[Brief description of the drawings]

FIG. 1 is a system diagram of an air cooler of a gas turbine according to a first embodiment of the present invention.

FIG. 2 is a system diagram of an air cooler of a gas turbine according to a second embodiment of the present invention.

FIG. 3 is a system diagram of an air cooler of a gas turbine according to a third embodiment of the present invention.

FIG. 4 is a system diagram of an air cooler of a gas turbine according to a fourth embodiment of the present invention.

FIG. 5 is a system diagram of an air cooler of a conventional gas turbine.

FIG. 6 shows a horizontal (U-tube vertical) arrangement of an air cooler of a conventional gas turbine, wherein (a) is a front view and (b) is a side view.

7A and 7B show a vertical (bottom of water chamber) arrangement of an air cooler of a conventional gas turbine, wherein FIG. 7A is a front view and FIG. 7B is a side view.

8 shows a vertical (water chamber top) arrangement of an air cooler of a conventional gas turbine, where (a) is a front view and (b) is a side view.

[Explanation of symbols]

 1, 10, 20 Controller 2 Recirculation valve 3, 4, 11 Flow meter 5 Recirculation line 12, 85 Flow control valve 13, 83, 84, 86 On-off valve 14 Standby pump 15 Tank 16 Line 17 Supply line 21 (A ), 21 (B) on-off valve 22 (A), 22 (B) on-off valve 23 (A), 23 (B) switching valve 80 air cooler 81 gas turbine 82 pump 87 bypass line 88, 89 cooling air line 90 cooling Water line

Claims (4)

[Claims] 1. A gas turbine for supplying and flowing cooling water from external equipment of a gas turbine to a heat transfer tube group inside a cooler main body, cooling air around the heat transfer tube group, and supplying the cooled air as gas turbine cooling air. In the air cooler, a recirculation line connecting the cooling water outlet side flow path of the heat transfer tube group to the inlet side flow path, a recirculation valve provided in the middle of the recirculation line, A first flow meter provided on the downstream side of the recirculation line connection portion of the outlet flow path, a second flow meter provided on the recirculation line,
An air cooler for a gas turbine, comprising: a control device that receives a detection signal from a second flow meter and controls an opening of the recirculation valve. 2. The air cooler comprises two systems, and each system has an opening / closing valve on each of a cooling water inlet side and an outlet side, and the control device controls the opening / closing valves to control the two systems. 2. An air cooler for a gas turbine according to claim 1, wherein control is performed such that cooling water is supplied to one of the gas turbines and cooling air is supplied to the gas turbine. 3. A cooling water tank connected to external equipment of the gas turbine, a supply system for supplying cooling water from the cooling water tank to a heat transfer tube group inside the cooler body, and provided in the middle of the supply system. A flow control valve, a path for supplying cooling water from the cooling water tank to the heat transfer tube group, and a standby pump provided in the same path; and a cooling water tank from the middle of the cooling water outlet side flow path of the heat transfer tube group. A recirculation line connected to the recirculation line, a recirculation valve provided in the middle of the recirculation line, and a first flow meter provided on the cooling water outlet side flow path on the downstream side of the recirculation line connection portion. And a second flow meter provided on the upstream side of the recirculation line connection portion of the cooling water outlet side flow path, and captures detection signals of the first and second flow meters, and Controlling the opening of the flow control valve and the recirculation valve In both cases, the air cooler of the gas turbine controls the drive of the standby pump. 4. A gas turbine for supplying and flowing cooling water from external equipment of a gas turbine to a heat transfer tube group inside a cooler main body, cooling air around the heat transfer tube group, and supplying the cooled air as gas turbine cooling air. Wherein the heat transfer tube group is composed of a plurality of U-shaped tubes, and a pair of communicating tubes of each U-shaped tube are arranged so as to be on the same horizontal plane. Air cooler.