JPH10325697A - Capacity regulator for heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacity regulator for a heat exchanger which can largely enhance the controlling properties of the heat exchanger which uses steam as its heating source at the time of a load reduction without making the interior a negative pressure. SOLUTION: There are provided a water tank 15 having the larger holding amount of water than the capacity of a steam chamber 10a of a heat exchanger 10, drain piping 16 which communicates the lower part of the steam chamber to the lower part of the water tank, and a drain line 17 which drains overflowing water from a predetermined level of the water tank. The installation height H of the water tank 15 is set, so that the water level in the heat exchanger 10 becomes lower than a heat transfer surface by a rated steam pressure P. Thereby, the water in the water tank 15 flows into the heat exchanger 10 to reduce the heat transfer area by the decrease in the condensing pressure in the event of the load reduction, so that the water is balanced at the water level which provides the heat transfer area corresponding to the load.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for adjusting the capacity of a heat exchanger using steam as a heating source.

[0002]

2. Description of the Related Art FIG. 3 shows a chemical plant, a power plant,
1 is a configuration diagram of a shell and tube heat exchanger widely used as a heat exchanger using steam as a heating source in a large refrigerator or the like. In this figure, 1 is a shell constituting a pressure-resistant container, 2 is a heat transfer tube (tube), 3 is a baffle, and 4 is a header. When used as a heater using steam, the fluid to be heated 5 is usually flowed inside the tube 2 and steam 6 is supplied into the shell 1 as illustrated in the figure. Conversely, in some cases, steam 6 may flow in the tube and fluid 5 to be heated may flow in the shell. In addition,
In this figure, reference numeral 6b denotes a drain trap which drains condensed water (drain). Further, a regulating valve may be used instead of the drain trap.

[0003]

In the heat exchanger using steam as a heating source, the steam supply line is provided with a flow rate control valve 7 as shown in FIG. And the flow control valve 7 is adjusted so that the temperature falls within a predetermined range. In this case, the heat transfer amount Q in the heat exchanger is represented by the heat transfer basic formula (Q = UAΔT) of the heat exchanger.
It is represented by Here, U is the heat transmission coefficient, A is the heat transfer area, and ΔT is the temperature difference between the inside and outside of the tube.

However, in such a heat exchanger, even if the flow control valve 7 is throttled to reduce the heat transfer amount (load) when the load is reduced and the amount of supplied steam is reduced, the change in the heat transfer rate U due to the steam pressure is reduced. Is small and the temperature difference ΔT does not change much because the steam temperature does not change much. For this reason, 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 closes and the drain accumulates inside and the heat transfer area A decreases.

[0005] Therefore, in the conventional heat exchanger, when the load is reduced, for example, it may take 30 minutes to 1 hour or more until the drain accumulates, during which time the heated side is overheated and the load is reduced. There is a problem that the controllability of the device is extremely poor. Further, if the flow control valve 7 is completely closed to reduce the load, the inside becomes negative pressure due to the condensation of the remaining water vapor, and air may enter from the outside air and hinder the function of the heat exchanger. was there.

The present invention has been made to solve such a problem. That is, an object of the present invention is to provide a capacity adjusting device capable of greatly increasing the responsiveness of a heat exchanger using steam as a heating source when the load is reduced without generating a negative pressure inside.

[0007]

In this type of heat exchanger using steam as a heating source, the means for controlling the heat transfer area by drain is the most effective in responding to a low load. The point is to do it quickly. The present invention is based on such a new idea.

That is, according to the first aspect of the present invention, a water tank having a larger amount of water than a steam chamber capacity of a heat exchanger having a heat transfer surface using steam as a heating source, a lower portion of the steam chamber, and a water tank It has a drain pipe communicating with the lower part, and a drain line for draining overflow water from a predetermined level in the water tank, and the installation height of the water tank is such that the water level in the heat exchanger at the rated steam pressure is a heat transfer surface. There is provided a heat exchanger capacity adjusting device, which is set to be lower.

The first invention is particularly suitable when the pressure of the pressurized steam is low. That is, according to the configuration of the present invention, the drain side of the drain of the heat exchanger is arranged at a high position, and a water tank having a sufficient storage amount is installed therein, 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 used as it is.

In addition, when the load is reduced, the flow rate of the steam for heating is reduced and the condensing pressure is reduced. Therefore, water can be sent to the heat exchanger in reverse by the water pressure in the water tank to reduce the heat transfer area. At this time, since the water level in the water tank is sufficiently high, water is automatically sent to the heat exchanger side by this differential pressure, and the water level is balanced with a heat transfer area corresponding to the load. If the water pipe (drain pipe) is made thick enough,
Since the flow resistance is low and the water moves quickly, the responsiveness at the time of load reduction is greatly enhanced, and the response delay can be made negligibly small.

Further, when the amount of water increases due to the condensation of water vapor, overflow water can be drained from a predetermined level in the water tank through a drain line, and the amount of water retained inside is automatically adjusted to a certain range. Can be adjusted. Therefore,
The back pressure can be maintained within a certain range, and the condensing pressure can be kept almost constant. In particular, in this capacity adjusting device, since water is fed in accordance with a decrease in condensing pressure due to a decrease in load, a special control device is not required, and high reliability can be obtained.

According to the second aspect of the present invention, there is provided a water tank having a larger water holding capacity than a steam chamber capacity of a heat exchanger having a heat transfer surface using steam as a heating source, a lower steam chamber section and a lower water tank section. And a drain line for draining from the drain pipe, wherein the water tank is an airtight tank pressurized with gas, and the internal pressure of the heat exchanger at the rated steam pressure of the heat exchanger. Wherein the water level is set lower than the heat transfer surface. According to a preferred embodiment of the present invention, a water level sensor for detecting a water level in a water tank and a drain valve for opening and closing a drain line are provided, and the water level sensor operates the drain valve to set the water level in the water tank to a predetermined level. Adjusts to the range.

The second invention is particularly suitable when the pressure (and temperature) of the pressurized steam is high. In the present invention, the water tank is an airtight tank pressurized with gas, and the internal pressure thereof 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. So
Even when the pressure of the pressurized steam is, for example, 10 atg or more,
With the water tank installed at a low position, it can function similarly to the first invention. That is, when the load is reduced, the condensing pressure is lowered, water is fed from the water tank to control the heat transfer area, and the drain tank valve is closed by the water tank liquid level dropping. If the load increases, the water level rises and the drain valve opens to drain the drain. Therefore, only maintaining the internal pressure of the water tank constant according to the rated steam pressure does not require a special control device, 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.

Therefore, according to the first and second aspects of the present invention, overheating of the fluid to be heated and negative pressure of the condensing pressure do not occur, and a stable operating state up to a low load (theoretical 0%) can be obtained. In addition, the responsiveness of the heat exchanger when the load is reduced can be greatly increased.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the drawings, common portions are denoted by the same reference numerals, and redundant description is omitted. FIG.
1 is a configuration diagram of a heat exchanger capacity adjusting device according to a first embodiment of the present invention. In this figure, the heat exchanger 10
It has a heat transfer tube (tube) 2 that passes through the inside of the shell 1, flows the fluid to be heated 5 inside the tube 2, and supplies steam 6 into the shell 1 via a steam line 6 a to heat the fluid 5 to be heated. It has become. Therefore, the heat transfer tube 2 is a heat transfer surface, and a part of the shell 1 is a steam chamber 10a. Also,
The steam line 6a is provided with a flow control valve 11,
The flow rate control valve 11 is adjusted so that the output of the temperature sensor 12 for detecting the temperature of the fluid 5 to be heated becomes the set temperature. Reference numeral 13 denotes a flow control valve for adjusting a load.

Note that the heat exchanger 10 is a shell and
Although a tube heat exchanger is preferable, the present invention is not limited to this, and other types of heat exchangers may be used as long as they are indirect heating systems having a heat transfer surface using steam as a heating source. Is also good. In the heat exchanger 10, a normal shell
Whether there is no baffle unlike the and tube heat exchanger,
Even in some cases, it is preferable that a vent hole is provided so that drain water accumulated inside can freely communicate through the baffle. Further, although this figure shows a horizontal heat exchanger, it may be a vertical heat exchanger.

In FIG. 1, the capacity adjusting device 14 of the present invention is shown.
Is a water tank 15, a drain pipe 16 and a drain line 17
It has. The water tank 15 has a larger amount of water than the capacity of the steam chamber 10a of the heat exchanger 10, and is installed at a high position as shown in the figure. Drain piping 16
Communicates the lower part of the water vapor chamber 10a and the lower part of the water tank 15. The drain line 17 drains overflow water from a predetermined level in the water tank 15. The upper part of the water tank 15 communicates with the atmosphere so that the water tank 15 is at atmospheric pressure.

Further, the installation height H of the water tank 15 is set such 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 is lower than the lower part of the steam chamber 10a (shown by 0 in the figure) to the level at which water overflows from the water tank 15 is the heat exchanger 1
It is set so as to substantially match the rated steam pressure P of 0.

Therefore, the rated steam 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 in the case of 1 atg, about 1
Set to 0m. The capacity adjusting device of the first embodiment is particularly suitable when the pressure of the pressurized steam is low, and when the pressure of the pressurized steam is high, it is preferable to use the second embodiment described later.

According to the configuration of the present invention described above, the drain side of the drain of the heat exchanger 10 is arranged high, and the water tank 15 having a sufficient amount is installed therein. Since the water level in the heat exchanger 10 is set to be lower than the heat transfer surface, the water level in the heat exchanger 10 is sufficiently low at the rated load due to the rated steam pressure P, and the heat transfer area A is effectively used as it is. Can be.

When the load is reduced, the flow rate of the steam for heating is reduced by the flow rate control valve 11 and the condensing pressure is reduced.
Conversely, water can be sent to the heat exchanger by the water pressure in the water tank 15 to reduce the heat transfer area A. At this time, since the water level in the water tank 15 is sufficiently high, the water is automatically sent to the heat exchanger 10 side by the differential pressure H, and the water level is balanced with the heat transfer area A corresponding to the load. It is preferable that the water pipe (the drain pipe 16) be sufficiently thick with a small resistance, so that the water moves quickly, so that the response at the time of load reduction is greatly enhanced, and the response delay is negligibly small. it can.

Further, when the amount of water increases due to the condensation of water vapor, overflow water can be drained from a predetermined level in the water tank 15 through the drain line 17 so that the internal water level within the water tank 15 falls within a certain range. Can be adjusted automatically.
Further, in particular, in the capacity adjusting device 14, since water is sent in due to a decrease in condensing pressure due to a decrease in load, no special control device is required, and high reliability can be obtained.

FIG. 2 is a configuration diagram of a heat exchanger capacity adjusting device according to a second embodiment of the present invention. In this figure,
The water tank 15 is an airtight tank, and is maintained at a constant pressure by gas supplied from a gas line 18 having a flow control valve 18a. This gas may be air or nitrogen gas. The drain line 17 drains directly from the drain pipe 16.

The capacity adjusting device 14 of the present invention further includes a water level sensor 19 for detecting the water level in the water tank 15 and a drain valve 17a for opening and closing the drain line 17. The drain valve 17a is operated by the water level sensor 19. Then, the water level in the water tank 15 is adjusted to a predetermined range. Further, in this embodiment, a pressure sensor 20 for detecting the pressure in the water tank 15 is provided, and the internal pressure is detected by the pressure sensor 20. The internal pressure is used for 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 steam chamber 10a. Other configurations are the same as those in FIG.

The invention of FIG. 2 is particularly suitable when the pressure (and temperature) of the pressurized steam is high. According to the configuration of the present invention described above, the water tank 15 is an airtight tank pressurized with gas, and the internal pressure of the water tank 15 is equal to the water level in the heat exchanger at the rated steam pressure P of the heat exchanger 10. Since the pressure is set to be lower, even when the pressure of the pressurized steam is, for example, 10 atg or more, it is possible to function in the same manner as in the first aspect of the invention, with the water tank 15 installed at a low position. That is, if the load decreases, the condensation pressure decreases,
Water is supplied from the water tank 15 to control the heat transfer area A, and the drain tank 17 a 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 steam 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.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified without departing from the gist of the present invention.

[0027]

As described above, the capacity adjusting device for a heat exchanger according to the present invention does not cause overheating of the fluid to be heated or negative pressure of the condensing pressure, and has a low load (theoretical 0%). It has an excellent effect that a stable operating state can be obtained, and the responsiveness of the heat exchanger when the load is reduced can be greatly increased.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a capacity adjusting device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a capacity adjusting device according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a conventional heat exchanger.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pressure-resistant container (shell) 2 Heat transfer tube (tube) 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 rate Control valve 14 Capacity adjusting device 15 Water tank 16 Drain pipe 17 Drain line 17a Drain valve 18 Gas line 18a Flow control valve 19 Water level sensor 20 Pressure sensor

Claims (3)

[Claims] 1. A water tank having a larger water holding capacity than a steam chamber capacity of a heat exchanger having a heat transfer surface using steam as a heating source, a drain pipe communicating between a lower portion of the steam chamber and a lower portion of the water tank, and A drain line for draining overflow water from a predetermined level in the tank, and the installation height of the water tank is set such that the water level in the heat exchanger is lower than the heat transfer surface at the rated steam pressure. And a heat exchanger capacity adjusting device. 2. A water tank having a larger water holding capacity than a steam chamber capacity of a heat exchanger having a heat transfer surface using steam as a heating source, a drain pipe communicating between a lower portion of the steam chamber and a lower portion of the water tank, and a drain. A drain line for draining from a pipe, wherein the water tank is an airtight tank pressurized with gas, and the internal pressure is such that the water level in the heat exchanger is lower than the heat transfer surface at the rated steam pressure of the heat exchanger. Is set to be
A capacity adjusting device for a heat exchanger. 3. A water level sensor for detecting a water level in a water tank, and a drain valve for opening and closing a drain line, wherein the water level sensor operates the drain valve to adjust the water level in the water tank to a predetermined range. The capacity adjusting device for a heat exchanger according to claim 2, wherein: