JPH083879Y2 - Automatic temperature controller for heat exchanger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> This invention is a heat exchanger for exchanging heat from a heating fluid to an object to be heated, and automatically controls the temperature of the object to be heated to a constant value after heat exchange. Regarding the device.

<Prior Art> Conventionally, as the above-mentioned device, for example, there is one as shown in FIG. In the figure, 2 is a heat exchanger,
Heating fluid supplied from the heating fluid inlet 2a, for example steam,
Heat is exchanged with the object to be heated supplied from the object to be heated inlet 2b, and the object to be heated after heat exchange is delivered from the object to be heated outlet 2c. The heating fluid supplied to the heat exchanger is temperature-controlled by the control valve 4. As this control valve, a direct acting type such as a gauge type or a top guide type,
Alternatively, a rotary type valve such as a butterfly type or a ball type is used, and the temperature of the heating fluid is controlled by adjusting the valve opening degree. For this valve opening degree control, a pneumatic or electric type valve is used. A drive unit 6 is provided. To adjust the valve opening, the temperature of the heated object on the outlet side (hereinafter referred to as the detected temperature) detected by the temperature sensor 8 provided at the heated portion outlet 2c of the heat exchanger 2 is input to the PID controller 10. However, by performing PID control of the drive unit 6 so that the deviation between the temperature (hereinafter referred to as a set temperature) of the object to be heated on the outlet side preset in the PID controller 10 and the detected temperature becomes zero. Has been done.

<Problems to be Solved by the Invention> In the above-described device, the cause of the temperature change of the object to be heated on the outlet side of the heat exchanger is the temperature change due to the pressure change of the heating fluid and the flow rate of the object to be heated. A change or a change in the temperature of the object to be heated may be mentioned. The causes of such causes are as follows: when the temperature of the heating fluid changes only due to the pressure change, when the flow rate of the heated object changes or when only the temperature of the heated object changes, and when the pressure of the heated fluid changes. There may be a case where the accompanying temperature change and the flow rate change or temperature change of the object to be heated occur simultaneously. These fluctuations are corrected by the PID controller 10, but the optimum PID constant for correcting the temperature change due to the pressure change of the heating fluid and the optimum PID constant for correcting the flow rate change or temperature change of the object to be heated. , The optimum PID constants for compensating for both the temperature change due to the pressure change of the heating fluid and the flow rate or temperature change of the object to be heated are different, and for all these cases
There is a problem that the control becomes complicated when trying to cope with it by the PID controller 10.

<Means for Solving the Problems> The present invention has been made to solve the above problems, and is a pressure reducing valve as a self-regulating valve that self-adjusts the pressure of a heating fluid to a preset set pressure. A set pressure changing means for changing the set pressure of the pressure reducing valve, a heat exchanger for exchanging heat from the heating fluid sent from the pressure reducing valve to an object to be heated, and the target pressure sent from the heat exchanger. Temperature detection means for detecting the temperature of the heated object, and a preset temperature of the heated object after the heat exchange sent from the heat exchanger based on the output of the temperature detecting means. And a control unit that controls the set pressure changing unit so as to converge.

<Operation> According to the present invention, the pressure of the heating fluid supplied to the heat exchanger is self-adjusted to the set pressure by the pressure reducing valve. Since there is a correlation between the pressure of the heating fluid and its temperature, the pressure of the heating fluid is maintained at a constant value, which means that the temperature of the heating fluid is also maintained at a certain constant value. That is, the temperature of the heating fluid supplied to the heat exchanger is maintained at a constant value. On the other hand, the control unit controls the set pressure changing unit so as to converge to the preset set temperature of the heated object based on the temperature of the heated object after the heat exchange detected by the temperature detecting unit, and the pressure reducing valve. Change the set pressure of.

<Embodiment> In FIG. 1, 12 is a heat exchanger, 12a is a heating fluid inlet, 12b is a heated object inlet, and 12c is a heated object outlet. The heating fluid is supplied to the heating fluid inlet 12a via the pressure reducing valve 14. The pressure reducing valve 14 has a set pressure whose drive unit 16
It is configured to be changeable by. Then, the control is performed by the PID controller 18. Reference numeral 20 denotes a temperature sensor used for the control, which is provided at the heated portion outlet 12c of the heat exchanger 12.

The pressure reducing valve 14 and the drive unit 16 are configured, for example, as shown in FIG. That is, the motor 22 provided at the top of the main body 21
The rotation of the speed reducer 24, the adjustment screw 28 through the spline shaft 26
The adjustment screw 28, the male screw 30
Is screwed into the screw portion 32 for fixing in the main body 21, the adjusting screw 28 descends, and the pressure adjusting spring 38 is passed through the ball 34 and the spring receiver 36 which are in contact with the tip of the adjusting screw 28. Compress one end of. This compression causes the diaphragm 42 to pass through the spring bearing 40 provided at the other end of the pressure adjusting spring 38.
Is compressed, the pilot guide 44 is lowered, and the pilot valve 46 is pushed down against the acting force of the coil spring 48. In this state, when a heating fluid, such as steam, is introduced from the inlet 49, a part of this steam enters the chamber below the pilot valve 46 through the first passage 50 and the opened pilot valve 46 , Through the second passage 52 into the chamber above the piston 54. As a result, the piston 54 descends against the acting force of the coil spring 55 and opens the main valve body 56. Most of the primary pressure steam introduced from the inlet 49 is sent to the heat exchanger 12 from the outlet 58 as secondary pressure steam through the opened main valve body 56. A portion of this secondary pressure steam enters the chamber below diaphragm 42 through third passage 60. When the pressure of the secondary pressure steam is higher than the set pressure set by the pressure adjusting spring 38, the diaphragm 42 is pushed up against the acting force of the coil spring 48, and the opening degree of the pilot valve 46 becomes small. Therefore, the steam pressure applied to the piston 54 is reduced, the opening of the main valve body 56 is reduced by the acting force of the coil spring 55, and the secondary pressure is reduced to maintain the set pressure. On the other hand, when the secondary pressure is lower than the set pressure, the secondary pressure is increased by the operation reverse to the above, and the set pressure is maintained. Thus, in the pressure reducing valve 10,
The secondary pressure is self-adjusted to the set pressure set by the pressure setting spring 38.

Incidentally, 62 is a tubular body arranged so as to surround the main valve body 56, and a separator portion 64 is provided between the outer peripheral surface of the tubular body 62 and the inner wall surface of the main body 21 in the form of a steam introduction passage. Has been. The separator portion 64 is for separating condensate from the steam introduced from the inlet 49. The separated condensate accumulates at the bottom of the main body 21, but when the accumulated condensate exceeds a predetermined amount, the float 66 separates from the drain valve seat 68, and the condensate is discharged from the drain valve seat 68 to the outside. To do. 70 is a float cover. Float 66, drain valve seat 68, floater cover 70
Etc. constitute a steam trap.

The pressure is set by moving the pressure adjusting screw 28 by the motor 22 as described above. The PID controller 18 controls the motor 22. This PID controller 18 is designed so that when there is a change in the flow rate or temperature of the heated object on the inlet side,
In order to maintain the temperature of the heated object on the outlet side at the set temperature input to
PID control is performed based on the output of. The PID constant used for this PID control is selected as an optimum value for promptly converging to the set temperature when the flow rate or temperature of the object to be heated changes.

According to the automatic temperature control device in the heat exchanger configured as described above, for example, when only the temperature of the heating fluid changes, the pressure reducing valve 14 adjusts itself, so that the pressure of the heating fluid supplied to the heat exchanger 12 is It is maintained at the set pressure. Since there is a correlation between the pressure and the temperature of the heated fluid, the temperature of the heated fluid is kept at a constant value as long as the pressure is constant. That is, the temperature of the heating fluid supplied to the heat exchanger 12 is maintained at a constant value.

Further, when the flow rate or temperature of the heated object changes, the outlet side temperature of the heated object of the heat exchanger changes, but this temperature change is kept constant by the self-adjustment of the pressure reducing valve 14. Therefore, it is purely based on the flow rate or temperature change of the object to be heated. This temperature change is detected by the temperature sensor 20 and supplied to the PID controller 18. The PID controller 18 controls the drive unit 16 based on the output of the temperature sensor 20, the preset temperature and the PID constant to change the set pressure of the pressure reducing valve 14, that is, the heat exchanger. The temperature of the heating fluid supplied to 12 is controlled to maintain the outlet side temperature of the heat exchanger at the set temperature.

Further, when both the temperature of the heating fluid and the flow rate or temperature of the object to be heated change, the temperature change of the heating fluid is corrected by the self-adjustment of the pressure reducing valve, so the flow rate or temperature of the object to be heated eventually changes. Similar to the case, the PID controller 18 controls the drive unit 16 in the same manner as described above to maintain the outlet side temperature of the heat exchanger at a constant value.

In the above embodiment, the drive unit is an electric type using the motor 22, but a pneumatic type can be used. Also,
Although PID control is performed using the PID controller 18, other control methods such as P control and PI control may be performed.

<Effect of Device> As described above, according to this device, since the heating fluid whose pressure is adjusted to the set pressure by the pressure reducing valve as the self-adjusting valve is supplied to the heat exchanger, it is supplied to the pressure reducing valve. Even if the pressure or load of the heating fluid (the amount or temperature of the fluid to be heated) varies, the pressure of the heating fluid supplied to the heat exchanger, and thus the temperature, is maintained constant. Therefore, the control unit does not need to consider the temperature change of the heating fluid, and only needs to control so as to quickly converge the outlet side temperature change of the heat exchanger due to the flow rate or temperature change of the object to be heated. Will be easier.

For example, in the conventional example shown in FIG. 3, FIG.
When the flow rate of the object to be heated increases as shown in (b)
As shown in, the outlet pressure of the control valve 4 decreases. If the flow rate of the object to be heated only increases, the outlet temperature of the heat exchanger 2 only decreases as shown by the dotted line in FIG. 7C, but the outlet pressure of the control valve 4 also decreases, so The increase in the flow rate of the product and the decrease in the outlet pressure of the control valve 4 combine to decrease the outlet temperature of the heat exchanger 2 as shown by the solid line in FIG. As described above, the PID controller 10 has to control the temperature decrease due to the synergistic effect of the two factors, which makes the control complicated.

On the other hand, in the present invention, even if the flow rate of the object to be heated increases as shown in FIG. 5 (a), the outlet pressure of the pressure reducing valve 14 is self-adjusted and set as shown in FIG. 5 (b). Maintained at pressure. Therefore, as shown in FIG. 7C, the outlet temperature of the heat exchanger is reduced by the amount of change in the flow rate of the object to be heated.
Since the control unit (PID controller 18) only has to correct this decrease by changing the set pressure, the control becomes simple. The same applies when the temperature of the object to be heated changes.

Further, in this embodiment, as the self-regulating valve, a pressure reducing valve in which a separator and a steam trap are integrated is used. Therefore, the water droplets contained in the heating fluid (steam) are removed by these separators and steam traps and are not supplied to the heat exchanger, so the dryness of the steam supplied to the heat exchanger is always kept constant. Also, there is no change in the outlet temperature due to the change in dryness.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment of an automatic temperature control device for a heat exchanger according to the present invention, FIG. 2 is a longitudinal sectional view of a pressure reducing valve used in the same embodiment, and FIG. 3 is an automatic heat exchanger for a conventional heat exchanger. FIG. 4 is a schematic diagram of the temperature control device, FIG. 4 is a diagram showing pressure and temperature change states of respective parts of a conventional automatic temperature control device, and FIG. 5 is a diagram showing pressure and temperature change states of respective parts of this embodiment. 12 …… Heat exchanger, 14 …… Pressure reducing valve (self-regulating valve), 16 ……
Drive section (set pressure change means), 18 ... PID controller (control section), 20 ... Temperature sensor (temperature detection means).

Claims (1)

[Scope of utility model registration request] Claim: What is claimed is: 1. A pressure reducing valve as a self-adjusting valve for self-adjusting the pressure of a heating fluid to a preset pressure, a set pressure changing means for changing the set pressure of the pressure reducing valve, and a delivery from the pressure reducing valve. A heat exchanger for exchanging heat from the heated fluid to the object to be heated, and a temperature detecting means for detecting the temperature of the object to be heated after heat exchange sent from the heat exchanger,
Based on the output signal of the temperature detecting means, the set pressure changing means is provided so that the temperature of the heated object after heat exchange sent from the heat exchanger converges to a preset temperature of the heated object. An automatic temperature control device in a heat exchanger comprising a control unit for controlling.