JPH07159084A - Operation method for heat exchanger - Google Patents

Abstract

PURPOSE:To easily carry out the control which keeps the thermal state of a heat exchanger constant. CONSTITUTION:In the operation method of a heat exchanger, heat exchange is carried out between tube side fluid (A) passing through a heat exchanger main body 4 through a number of heat transfer tubes 6 arranged within the heat exchanger main body 4 and main body side fluid (B) passing outside the heat transfer tube 6. A plural kinds of shutoff valves 22 are provided for the purpose of respectively closing the heat transfer tubes 6 at individually different temperature obtained by sensing the temperature of the fluid (A) at the outlet part 21 of the heat transfer tubes 6 opened within the heat exchanger main body 4. The number of the heat transfer tubes of an opened state are controlled by closing in a stepwise manner the selected kinds of the shutoff valves 22 according to the variation of the temperature of the tube side fluid (A).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to heat exchangers, and in particular to
The present invention relates to an operation method of a heat exchanger for controlling a temperature state of a tube-side fluid after heat exchange, which passes through a large number of heat transfer tubes arranged in a heat exchanger body, to be constant.

[0002]

2. Description of the Related Art In a chemical plant, a nuclear power plant or the like, a heat exchanger as shown in FIG. 7 is used to exchange heat between a pipe side fluid and a body side fluid.

As shown in the figure, this heat exchanger 1 has a heat exchanger body 4 having a water chamber portion 2 and a cylindrical body portion 3,
Inside the heat exchanger body 4, a heat transfer tube 6 held by a tube plate 5 that partitions the water chamber 2 and the body 3 is arranged, and the heat transfer tube 6 is U-shaped in the body 3. The inlet chamber 7 and the outlet chamber 8 which are bent into a shape and partitioned in the water chamber portion 2 are connected to each other. The heat transfer tubes 6 are arranged over a large number, and each heat transfer tube 6
Forms a transfer passage for the pipe side fluid A that flows into the inlet chamber 7 of the water chamber portion 2 and flows out from the outlet chamber 8. On the other hand, the body portion 3 is formed with an inlet portion 11 and an outlet portion 12 for the body-side fluid B passing outside the heat transfer tube 6.

Therefore, the tube side fluid A passing through the heat transfer tube 6 and passing through the heat exchanger body 4 and the body side fluid B passing through the outside of the heat transfer tube 6 and passing through the heat exchanger body 4 are the heat transfer tube 6 Through indirect contact with each other and heat exchange with each other.

[0005]

By the way, the heat exchanger 1
Therefore, under operating conditions aiming to always obtain a constant temperature, the temperatures at four points on the inlet / outlet side of the pipe side fluid A and the inlet / outlet side of the body side fluid B are fixed. If the temperatures at the four points are not fixed, the temperature of the tube-side fluid A changes and the temperature of the body-side fluid B changes, and the fluctuation of the body-side fluid temperature changes the tube-side fluid temperature.

Therefore, feedback control is performed to obtain a constant temperature. For example, the temperature of the outlet side of the body fluid B is detected by the sensor 13, the detected temperature is compared with the set temperature, and the throttle valve 14 provided on the inlet side of the body fluid B is installed according to the temperature difference. The opening of is being adjusted. Further, the discharge amount of the pump for pumping the fluid A, B on the tube side or the body side may be changed. By changing the opening degree of the throttle valve 14 and the discharge amount of the pump, the flow rates of the fluids A and B on the tube side or the body side are changed to adjust the temperatures of the fluids A and B on the tube side or the body side.

On the other hand, if the throttle valve 14 or the pump fails,
If the timing of operating these is delayed, it becomes impossible to obtain a constant temperature from the heat exchanger 1, and control of the mechanical system by the throttle valve 14 or pump provided outside the heat exchanger 1 complicates the control system. There is a problem to make it.

The present invention was devised to effectively solve the above problems. It is an object of the present invention to provide a heat exchanger operating method capable of easily controlling the temperature state of the heat exchanger to be constant.

[0009]

DISCLOSURE OF THE INVENTION The present invention is a cylinder in which a tube-side fluid passing through a heat exchanger main body through a large number of heat transfer tubes arranged in a heat exchanger main body passes outside the heat transfer tube. In a method of operating a heat exchanger for exchanging heat with a side fluid, a plurality of heat transfer tubes that are opened in the heat exchanger body are closed at different outlet temperatures by sensing the temperature of the tube side fluid. Different types of shut-off valves are attached, and these shut-off valves are gradually closed according to the temperature change of the fluid on the tube side to control the number of open heat transfer tubes.

[0010]

When the predetermined number of all the heat transfer tubes are closed by the shut-off valve according to the temperature change of the tube side fluid, the flow of the tube side fluid in the closed heat transfer tube is stopped, and the remaining open state is maintained. The fluid on the tube side passes only through the heat transfer tube. When the heat transfer tubes are closed, the heat transfer area of the entire heat exchanger is reduced by the number of closed heat transfer tubes, and the heat exchange amount is reduced. On the contrary, if the closed heat transfer tubes are opened, the heat transfer area is increased by the number of the opened heat transfer tubes, and the heat exchange amount is increased. Therefore, controlling the number of heat transfer tubes in the open state also controls the heat transfer area of the heat exchanger, and heat exchange is performed according to the temperature change of the tube side fluid so that the tube side fluid after heat exchange has a constant temperature. Feedback control is performed so that the heat transfer area of the vessel is adjusted.

Further, by closing a predetermined number of heat transfer tubes in multiple stages in accordance with the temperature change of the tube-side fluid, the heat transfer area is controlled to decrease gradually.

[0012]

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows a multi-tube heat exchanger used in a chemical plant, a nuclear power plant or the like. Since the heat exchanger 1 has already been outlined, it will be omitted. The same symbols are attached.

As shown in FIG. 1, a large number of heat transfer tubes 6 forming a transfer passage for the fluid A on the tube side are bent in a U shape and held by a tube sheet 5, and are shown in FIGS. As shown, the outlet 21 of the heat transfer tube 6 is closed by a shutoff valve 22 that senses the temperature of the fluid A on the tube side. The shut-off valve 22 has a disc-shaped shut-off lid 23 and one end welded to the shut-off lid 23 4
It is composed of a shape memory alloy rod 24. The other end of the rod 24 is welded to the bottom of an annular groove 25 formed in the tube sheet 5. The annular groove 25 expands the outlet portion 21 of the heat transfer tube 6 to form a substantial outlet portion. As shown in FIG. 3, since the closing lid 23 is formed larger than the annular groove 25, if the rod 24 senses a predetermined temperature of the tube-side fluid A and shortens the closing lid 23, the closing lid 23 closes the annular groove 25. The flow of the tube side fluid A will be automatically stopped. In this case, since the closing lid 23 acts as a flow resistance when the closing valve 22 is opened, a pump suitable for the pressure loss is used.

Further, each rod 24 is stored and set so that the temperature at which the heat transfer tube 6 should be closed differs depending on the type of the closing valve 22, and a plurality of types of closing valves 22 having different closing temperatures are stepwise for each type. In addition, a large number of heat transfer tubes 6 are closed. Generally, the heat transfer tubes 6 are arranged over 200 to 2000 tubes. For example, when the stop valves 22 are attached to the outlets 21 of all the heat transfer tubes 6, the temperature of the tube-side fluid A is determined from several times. How many times 50% of the closing valve 22 closes, 75% of the closing valve 22 closes from 90 to 90%, and 90% of the closing valve 22 closes from how many times The stepwise closing operation is performed. 75% of all heat transfer tubes 6 when 75% of the shutoff valve 22 is closed
%, The flow is stopped, so the heat transfer area of the heat exchanger as a whole is reduced to 25%. As described above, if the number of the heat transfer tubes 6 in the open state gradually decreases according to the temperature change of the tube side fluid A and the heat transfer area of the entire heat exchanger decreases stepwise, the heat exchange amount becomes stepwise. Will be lowered.
On the contrary, when the shutoff valve 22 opens all the heat transfer tubes 6, the heat transfer area becomes maximum and the heat exchange amount increases.

By repeating the stepwise opening and closing of a plurality of types of shut-off valves 22 having different closing temperatures according to the type, the temperature of the pipe side fluid A is always maintained in an equilibrium state. That is, the heat transfer area of the heat exchanger as a whole is set so that the pipe side fluid A flowing out of the heat exchanger 1 after the heat exchange has a set temperature.
The control of being adjusted by 2 will be made in the heat exchanger body 4. Therefore, when the tube side fluid A passing through the heat exchanger 1 is cooled by the body side fluid B, the shutoff valve 22 senses the outlet temperature of the heat transfer tubes 6 and reduces the heat transfer area of all the heat transfer tubes 6. It is possible to prevent the pipe side fluid A from being overcooled.

If the number of types of the shutoff valve 22 set to different closing temperatures is increased, the heat transfer area can be adjusted in multiple stages, and the decrease in the heat transfer area can be moderated. Further, some of the heat transfer tubes 6 may be provided with the stop valves 22 set to different closing temperatures depending on the type.
Therefore, when the shutoff valve 22 is attached to the half of the heat transfer tubes 6, the flow of the half of the heat transfer tubes 6 is secured, and the control is to close the remaining half of the heat transfer tubes 6 in stages.

Of the large number of heat transfer tubes 6 arranged in the heat exchanger body 4 as described above, a required number of heat transfer tubes 6 are closed in accordance with the temperature change of the fluid A on the tube side to open the heat transfer tubes. Since the number of 6 is controlled, feedback control is performed within the heat exchanger body 4 such that the heat transfer area of the entire heat exchanger is adjusted in accordance with the temperature change of the fluid A on the tube side. Compared with the control by the machine installed outside
The control system is simple. Further, unlike the control system of the machine, the control timing is not delayed, and in the present invention, the temperature control of the heat exchanger 1 can be reliably and easily performed.

FIGS. 4 to 6 show other embodiments of the shutoff valve 22. Any of the shutoff valves 22 utilizes the characteristics of the shape memory alloy as in the above embodiments, and the pipe side fluid A It is configured to close the outlet portion 21 of the heat transfer tube 6 by sensing the temperature.

FIG. 4 shows a closing valve 22 in which the outlet 21 of the heat transfer tube 6 is projected from the tube sheet 5 into the outlet chamber 8 and the projected outlet 21 is closed by a closing lid 31. As indicated by the broken line in the example, the rod 32 for attaching the closing lid 31 to the tube sheet 5 is made of a shape memory alloy so as to shorten and close the outlet portion 21. By thus projecting the outlet portion 21 of the heat transfer tube 6 from the tube sheet 5, the welding operation becomes easy. FIG. 5 shows a shape memory alloy closing lid 33 and a mounting portion 3
4 is formed and the attachment portion 34 is directly attached to the tube sheet 5. The cover 33 which is bent back is deformed into a flat plate shape to close the heat transfer tube 6 when a predetermined temperature is sensed.
FIG. 6 shows that the central portion of the shape-memory alloy closing lid 35 that has been warped is attached to the heat transfer tube 6 via the attachment member 36.
When 5 detects a predetermined temperature, it deforms into a flat plate shape and closes the heat transfer tube 6.

[0021]

In summary, according to the present invention, the required number of heat transfer tubes are gradually closed according to the temperature change of the fluid on the tube side to control the number of open heat transfer tubes. Compared with the control by the mechanical system installed outside,
The control system is simple, and temperature control can be performed reliably and easily.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a heat exchanger of the present invention.

FIG. 2 is an enlarged view showing a main part of FIG.

FIG. 3 is a cross-sectional view showing a closed state of a stop valve.

FIG. 4 is a sectional view showing another example of the stop valve.

FIG. 5 is a perspective view showing another example of the stop valve.

FIG. 6 is a perspective view showing another example of the stop valve.

FIG. 7 is a cross-sectional view showing a conventional heat exchanger.

[Explanation of symbols] 1 heat exchanger 4 heat exchanger body 6 heat transfer tube 21 heat transfer tube outlet 22 stop valve A tube side fluid B cylinder side fluid

Claims (1)

[Claims] 1. A pipe-side fluid passing through a plurality of heat transfer tubes arranged in a heat exchanger body and passing through the heat exchanger body is heat-exchanged with a body-side fluid passing outside the heat transfer tube. In the operation method of the heat exchanger, a plurality of types of stop valves for closing the heat transfer tubes at different closing temperatures by sensing the temperature of the tube-side fluid at the outlet of the heat transfer tube opened in the heat exchanger body are attached, A method of operating a heat exchanger, characterized in that the shut-off valves are gradually closed according to the temperature change of the fluid on the tube side for each type to control the number of open heat transfer tubes.