JP3812054B2 - Capacity adjustment device for heat exchanger - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a capacity adjustment device for a heat exchanger using steam as a heating source.
[0002]
[Prior art]
FIG. 3 is a configuration diagram of a shell-and-tube heat exchanger widely used as a heat exchanger using steam as a heat source in a chemical plant, a power plant, a large refrigerator, and the like. In this figure, 1 is a shell constituting a pressure vessel, 2 is a heat transfer tube (tube), 3 is a baffle, and 4 is a header. When used as a heater using water vapor, as illustrated in the figure, the fluid 5 to be heated is usually flowed inside the tube 2 and the water vapor 6 is supplied into the shell 1. On the contrary, in some cases, the water vapor 6 is allowed to flow in the tube, and the heated fluid 5 is allowed to flow in the shell. In addition, 6b is a drain trap in this figure, and drains condensed water (drain). In addition, a regulating valve may be used instead of the drain trap.
[0003]
[Problems to be solved by the invention]
In the heat exchanger using steam as a heating source as described above, the steam supply line is provided with a flow rate adjusting valve 7 as illustrated in FIG. 3, and the temperature of the heated fluid 5 is detected by the temperature sensor 8, and this temperature falls within a predetermined range. The flow control valve 7 is adjusted to enter. In this case, the heat transfer amount Q in the heat exchanger is expressed by the heat transfer basic equation (Q = UAΔT) of the heat exchanger. Here, U is the heat transfer rate, A is the heat transfer area, and ΔT is the temperature difference between the inside and outside of the tube.
[0004]
However, in such a heat exchanger, in order to reduce the heat transfer amount (load) when the load is reduced, even if the flow rate control valve 7 is throttled and the supplied water vapor amount is reduced, the change in the heat passage rate U due to the steam pressure is small, Since the steam temperature does not change so much, the change in temperature difference ΔT is small. Therefore, even if the flow control valve 7 is throttled, there is a problem that the amount of heat transfer does not decrease until the drain trap 6b is closed and the drain is accumulated inside the heat transfer area A.
[0005]
Therefore, in the conventional heat exchanger, when reducing the load, for example, it may take 30 minutes to 1 hour or more until the drain accumulates, and during that time, the heated side is overheated, and the controllability when reducing the load There was a very bad problem. Further, if the flow rate control valve 7 is completely closed to reduce the load, the internal pressure becomes negative as the remaining water vapor condenses, and air may enter from the outside air, thereby impairing the function of the heat exchanger. was there.
[0006]
The present invention has been made to solve such problems. That is, an object of the present invention is to provide a capacity adjusting device that can greatly enhance the responsiveness when reducing the load of a heat exchanger that uses steam as a heating source without generating a negative pressure inside.
[0007]
[Means for Solving the Problems]
In this type of heat exchanger using steam as a heat source as described above, the means for controlling the heat transfer area by the drain is the most effective for dealing with low loads, and the point is to perform this means quickly. . The present invention is based on such a new idea.
[0008]
That is, according to the present invention, a water tank having a larger water capacity than a water vapor chamber capacity of a heat exchanger having a heat transfer surface using water vapor as a heat source, and a drain pipe communicating the water vapor chamber lower part and the water tank lower part A drainage line that is attached to a predetermined level of the water tank and drains the overflow water from the predetermined level when the amount of water increases due to condensation of water vapor, and automatically adjusts the internal water level. The installation height of the water tank is such that the water level in the heat exchanger becomes lower than the heat transfer surface at the rated steam pressure, and the steam pressure in the steam chamber decreases as the load of the heat exchanger decreases. There is provided a capacity adjustment device for a heat exchanger, characterized in that the heat transfer area of the heat exchanger is automatically set to match the load .
[0009]
This invention is particularly suitable when the pressurized steam pressure is low. That is, according to the configuration of the present invention, the drain side of the drain of the heat exchanger is arranged high and a water tank having a sufficient holding amount is installed there, and the water level in the heat exchanger is transmitted at the rated steam pressure. Since it is set to be lower than the hot surface, the water level in the heat exchanger is sufficiently low due to the rated steam pressure at the rated load, and the entire heat transfer area can be effectively utilized as it is.
[0010]
In addition, when the load is reduced, the heating steam flow rate is reduced and the condensation pressure is reduced, so that the heat transfer area can be reduced by sending water back to the heat exchanger by the water pressure in the water tank. At this time, since the water level of the water tank is sufficiently high, water is automatically fed to the heat exchanger side by this differential pressure, and balance is achieved at the water level corresponding to the heat transfer area. If the water pipe (drain pipe) is made sufficiently thick, the flow resistance is low and the water moves quickly, so that the response at the time of load reduction is greatly improved and the response delay can be made small enough to be ignored.
[0011]
Furthermore, when the amount of water increases due to condensation of water vapor, the overflow water can be drained from the predetermined level of the water tank via the drainage line, and the amount of retained water is automatically adjusted to a certain range. be able to. Therefore, the back pressure can be maintained within a certain range, and the condensing pressure can be maintained almost constant. In particular, in this capacity adjusting device, since water is sent in response to a decrease in the condensation pressure accompanying a decrease in load, a special control device is unnecessary and high reliability can be obtained.
[0012]
[0013]
[0014]
Therefore, according to the present invention , the heated fluid does not overheat and the condensing pressure does not become negative, and a stable operating state can be obtained up to a low load (theoretically 0%). Responsiveness can be greatly improved.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the common part in each figure, and duplication of description is abbreviate | omitted. Figure 1 is a block diagram of a capacity adjusting device of a heat exchanger showing the implementation of the invention. In this figure, a heat exchanger 10 has a heat transfer tube (tube) 2 that passes through the inside of a shell 1, a heated fluid 5 flows inside the tube 2, and water vapor 6 flows into the shell 1 via a steam line 6 a. The heated fluid 5 is supplied and heated. Therefore, the heat transfer tube 2 is a heat transfer surface, and a part of the shell 1 becomes the water vapor chamber 10a. Further, a flow rate adjusting valve 11 is provided in the steam line 6a, and the flow rate adjusting valve 11 is adjusted so that the output of the temperature sensor 12 for detecting the temperature of the heated fluid 5 becomes a set temperature. Yes. Reference numeral 13 denotes a flow rate adjusting valve for adjusting the load.
[0016]
The heat exchanger 10 is preferably a shell-and-tube heat exchanger, but the present invention is not limited to this, as long as it is an indirect heating method having a heat transfer surface using steam as a heating source. However, other types of heat exchangers may be used. Further, unlike the ordinary shell-and-tube heat exchanger, the heat exchanger 10 has no baffle or has a vent hole even in some cases so that the drain water accumulated therein can freely communicate through the baffle. It is good to be. Further, in this figure, a horizontal heat exchanger is shown, but a vertical heat exchanger may be used.
[0017]
In FIG. 1, the capacity adjusting device 14 of the present invention includes a water tank 15, a drain pipe 16 and a drain line 17. The water tank 15 has a retained water amount larger than the capacity of the water vapor chamber 10a of the heat exchanger 10, and is installed at a high position as shown in the figure. The drain pipe 16 communicates the lower part of the water vapor chamber 10 a and the lower part of the water tank 15. The drain line 17 drains overflow water from a predetermined level of the water tank 15. The upper part of the water tank 15 communicates with the atmosphere and is at atmospheric pressure.
[0018]
Furthermore, the installation height H of the water tank 15 is set so that the water level in the heat exchanger is lower than the heat transfer surface at the rated steam pressure of the heat exchanger 10. That is, the head difference Hm from the level at which the water level 9 in the heat exchanger 10 becomes lower than the lower part of the water vapor chamber 10a (indicated by 0 in the figure) to the level at which water overflows from the water tank 15 is the heat exchanger 10. Is set so as to substantially match the rated steam pressure P.
[0019]
Therefore, when the rated water vapor pressure P is, for example, 0.5 kg / cm ² g (ie 0.5 atg), the head difference H is set to about 5 m, and when it is 1 atg, it is set to about 10 m. The capacity adjustment apparatus implementation form of this is particularly suitable when pressurized steam pressure is low, when the pressurized steam pressure is high, it is preferable to use reference example will be described later.
[0020]
According to the configuration of the present invention described above, the drainage side of the drain of the heat exchanger 10 is arranged high, and the water tank 15 having a sufficient holding amount is installed therein, and the heat exchanger 10 has the inside at the rated steam pressure P. Since the water level in the heat exchanger 10 is sufficiently low due to the rated steam pressure P at the rated load, the heat transfer area A can be effectively utilized as it is.
[0021]
Further, when the load is reduced, the flow rate of the heating steam is reduced by the flow rate control valve 11 and the condensing pressure is lowered. Therefore, the water pressure in the water tank 15 reversely sends water to the heat exchanger to reduce the heat transfer area A. it can. At this time, since the water level of the water tank 15 is sufficiently high, the water is automatically sent to the heat exchanger 10 side by this differential pressure H, and the water level is balanced at the heat transfer area A corresponding to the load. It is preferable that the water pipe (drain pipe 16) has a sufficient thickness with little resistance. As a result, the water moves quickly so that the response at the time of reducing the load is greatly improved, and the delay in response is negligibly small. it can.
[0022]
Furthermore, when the amount of water increases due to the condensation of water vapor, the overflow water can be drained from the predetermined level of the water tank 15 through the drain line 17, and the internal water level is automatically kept within a certain range. Can be adjusted. In particular, in the capacity adjusting device 14, since water is fed based on a decrease in the condensation pressure accompanying a decrease in load, a special control device is unnecessary and high reliability can be obtained.
[0023]
FIG. 2 is a configuration diagram of a capacity adjustment device for a heat exchanger showing a reference example of the present invention. In this figure, the water tank 15 is an airtight tank, and is kept at a constant pressure by the gas supplied from the gas line 18 having the flow rate control valve 18a. This gas may be air or nitrogen gas. The drain line 17 drains directly from the drain pipe 16.
[0024]
The capacity adjusting device 14 of the present invention further includes a water level sensor 19 that detects the water level in the water tank 15 and a drain valve 17a that opens and closes the drain line 17. The water level sensor 19 operates the drain valve 17a to The water level in the tank 15 is adjusted to a predetermined range. Furthermore, in this embodiment, a pressure sensor 20 that detects the pressure in the water tank 15 is provided, and the internal pressure is detected by the pressure sensor 20, and this internal pressure is subjected to heat exchange at the rated steam pressure P of the heat exchanger 10. The water level in the vessel 10 is set to be lower than the lower part of the water vapor chamber 10a. Other configurations are the same as those in FIG.
[0025]
The reference example of FIG. 2 is particularly suitable when the pressure (and temperature) of pressurized steam is high. According to the configuration of the reference example described above, the water tank 15 is an airtight tank pressurized with gas, and the internal pressure is the rated steam pressure P of the heat exchanger 10 and the water level in the heat exchanger is the heat transfer surface. Since the pressure is set to be lower, even when the pressure of the pressurized steam is, for example, 10 atg or more, the water tank 15 can be functioned in the same manner as the present invention with the water tank 15 installed at a low position. That is, if the load decreases, the condensing pressure decreases, water is sent from the water tank 15 to control the heat transfer area A, and the drain water valve 17a is also closed by decreasing the water tank liquid level. If the load increases, the water level rises and the drain valve 17a opens to drain the drain. Therefore, only by keeping the internal pressure of the water tank 15 constant according to the rated water vapor pressure P, no special control device is required, and high reliability can be obtained. In addition, drainage can be performed by simple liquid level control of the water tank, and the retained water can be adjusted to an appropriate range.
[0026]
In addition, this invention is not limited to embodiment mentioned above, Of course, it can change variously in the range which does not deviate from the summary of this invention.
[0027]
【The invention's effect】
As described above, the capacity adjustment device for a heat exchanger according to the present invention does not cause overheating of the heated fluid and negative pressure of the condensation pressure, and is in a stable operating state up to a low load (theoretically 0%). Is obtained, and it has excellent effects such as greatly improving the responsiveness when the load of the heat exchanger is reduced.
[Brief description of the drawings]
1 is a configuration diagram of a capacity adjustment apparatus according to the implementation embodiments of the present invention.
FIG. 2 is a configuration diagram of a capacity adjustment device showing a reference example .
FIG. 3 is a configuration diagram of a conventional heat exchanger.
[Explanation of symbols]
1 Pressure vessel (shell)
2 Heat transfer tubes (tubes)
3 Baffle 4 Header 5 Heated fluid 6 Steam 6a Steam line 7 Flow control valve 8 Temperature sensor 9 Water level 10 Heat exchanger 10a Steam chamber 11 Flow control valve 12 Temperature sensor 13 Flow control valve 14 Capacity adjustment device 15 Water tank 16 Drain piping 17 Drain line 17a Drain valve 18 Gas line 18a Flow control valve 19 Water level sensor 20 Pressure sensor

Claims (1)

A water tank having an amount of retained water larger than the steam chamber capacity of the heat exchanger having a heat transfer surface with steam as a heating source;
A drain pipe communicating the lower part of the water vapor chamber and the lower part of the water tank;
A drainage line that is attached to a predetermined level of the water tank and drains the overflow water from the predetermined level when the amount of water increases due to condensation of water vapor, and automatically adjusts the internal water level. Prepared,
The installation height of the water tank is such that when the water level in the heat exchanger becomes lower than the heat transfer surface at the rated steam pressure, and the steam pressure in the steam chamber decreases as the load of the heat exchanger decreases, the heat exchanger The heat exchanger capacity adjustment device is characterized in that the heat transfer area of the heat exchanger is automatically set to match the load .

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