JPH11163569A - Heat load cooling system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat load cooler capable of stably controlling a temperature of a primary cooling water, by keeping its power consumption, size, cost, parts, and the like almost as they are without depending on temperature and temperature variation of a secondary cooling water. SOLUTION: A cooling system circulates a primary cooling water directly cooling thermal load 5 in a closed loop 9 through a heat exchanger 7, supplies a secondary cooling water cooling the primary cooling water to the heat exchanger 7, and indirectly cools the thermal load 5 by the secondary cooling water. The cooling system comprises a feedback control means for detecting the temperature of the primary cooling water, and sustaining and controlling the temperature of the primary cooling water by varying the heat exchanged in the heat exchanger 7 through the flow control of the secondary cooling water based on the detected temperature; and a feedforward control means for controlling the flow of the secondary cooling water independent of the temperature of the primary cooling water, when the heat exchanged in the heat exchanger 7 is varied by the load variation of the heat load 5 and/or the temperature variation of the secondary cooling water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat load cooling system for cooling, for example, a laser medium of a solid-state laser oscillator.

[0002]

FIG. 5 shows a conventional heat load cooling system. This cooling system includes a tank 31 in which primary cooling water is stored. This primary cooling water is supplied to the circulation pump 33, heat load 35,
The closed loop 39 returns to the tank 31 via the heat exchanger 37. The primary cooling water is pure water, and the closed loop 39 is provided with an ion exchange resin 41 in order to maintain the purity of the primary cooling water. Secondary cooling water is supplied to the heat exchanger 37 via an open / close type electromagnetic water control valve 43 as indicated by a dotted arrow, and the secondary cooling water is discharged out of the system. The secondary cooling water is, for example, tap water (industrial water) and is supplied to cool the primary cooling water. 45 is a temperature sensor, 47
Is a controller for opening and closing the electromagnetic water control valve 43.

When the thermal load 35 is, for example, a laser medium of a solid-state laser oscillator, keeping the temperature of the laser medium constant is to keep the thermal lens effect, thermal birefringence effect, etc. uniform and constant, and to control the laser output and beam. It is indispensable to stabilize quality.

In this cooling system, the temperature of the heat load 35 can be kept constant by keeping the flow rate and temperature of the primary cooling water constant. Assuming that the pressure loss of the entire closed loop 39 of the circulation system is constant, the flow rate can be kept substantially constant by the capacity of the circulation pump 33. Regarding the temperature, the electromagnetic cooling valve 43 is opened and closed via a controller 47 based on the temperature detected by the temperature sensor 45 in the tank 31 of the primary cooling water to discharge the secondary cooling water to the outside of the system. It can be kept constant by adjusting the amount of heat. That is, while the electromagnetic water control valve 43 is closed, the temperature of the primary cooling water increases in proportion to the amount of heat applied to the heat load 35, and while the electromagnetic water control valve 43 is opened and the secondary cooling water flows. As the temperature of the primary cooling water decreases in proportion to the amount of heat exchanged by the heat exchanger 37, the temperature in the primary cooling water tank 31 is kept constant.

[0005] A temperature expansion type water control valve can be used in place of the electromagnetic water control valve 43. In this case, the same effect can be obtained by inserting the sensor unit into the primary cooling water tank 31 and limiting the flow rate of the secondary cooling water. However, in general, a temperature expansion type water control valve does not follow large and sudden load fluctuations and disturbances due to poor response of the sensor unit, and is therefore rarely used.

[0006]

In the above-described conventional temperature control method, when the amount of heat of the heat load 35 and the amount of heat exchanged by the heat exchanger 37 do not fluctuate, temperature equilibrium occurs and the electromagnetic water control valve 43 is opened. In this state, the temperature of the primary cooling water substantially coincides with the target temperature as shown in FIG. 6, and the temperature ripple and the temperature drift do not substantially occur. Below "temperature ripple"
Corresponds to the height of the temperature fluctuation, and "temperature drift" corresponds to the deviation of the average temperature.

However, in practice, the amount of heat of the heat load 35 fluctuates greatly depending on the purpose of use, and the amount of heat exchanged by the heat exchanger 37 fluctuates greatly due to fluctuations in the temperature and flow rate of the secondary cooling water. For example, as a general characteristic of the heat exchanger 37, as shown in FIG. 7, the temperature difference ΔT between the primary cooling water and the secondary cooling water and the exchanged heat amount have a positive characteristic relationship. There is a relation that the exchange heat quantity becomes large. FIG.
As shown in (2), the flow rate of the secondary cooling water also has a positive characteristic, and the larger the flow rate of the secondary cooling water, the larger the exchanged heat quantity. When setting the heat exchange quantity of the heat exchanger 37, a margin is provided so that the heat exchange can be performed when the heat load 35 is the maximum and the temperature of the inlet side of the heat exchanger 37 of the secondary cooling water is the maximum. The exchange heat quantity, specifically, the maximum flow rate of the secondary cooling water is set. However, since tap water (industrial water), which is not controlled for water pressure and temperature, is often used as secondary cooling water, not only the average temperature of secondary cooling water but also the amount of temperature change due to differences in temperature between day and night and the four seasons. Various. Also, the amount of heat of the heat load varies greatly depending on the purpose of use.

If tap water (industrial water) or the like is used as the secondary cooling water and the heat exchange amount of the heat exchanger 37 is set, for example, if an excessive margin is set on the safe side, a conventional electromagnetic water control valve is used. In the temperature control system in which only the valve 43 is opened and closed, the temperature ripple is generated in the primary cooling water by opening and closing the electromagnetic water control valve 43. Of course, shortening the opening / closing cycle of the electromagnetic water control valve also reduces the temperature ripple, but in this case, the mechanical life of the electromagnetic water control valve and the like will shorten the service life of itself. Further, the temperature ripple can be reduced by adopting a variable opening valve as the electromagnetic water control valve, but this is disadvantageous in terms of cost required for the control system. It is also possible to reduce the temperature ripple by increasing the internal capacity of the primary cooling water tank, but in this case, the device becomes large.

An object of the present invention is to provide a cooler adopting a cooling system represented by a cooler of a conventional solid-state laser oscillator,
Achieves high stability of the control temperature of the primary cooling water without depending on the temperature of the secondary cooling water used or its temperature change, while keeping the power consumption, size, cost, used parts life, etc. almost unchanged. It is in.

[0010]

According to the first aspect of the present invention,
The primary cooling water that directly cools the heat load is circulated through a closed loop through a heat exchanger, and the heat exchanger is supplied with secondary cooling water that cools the primary cooling water. In the heat load cooling system for cooling, the temperature of the primary cooling water is detected, and the amount of heat exchanged in the heat exchanger is changed by controlling the flow rate of the secondary cooling water based on the detected temperature. Feedback control means for maintaining and controlling the temperature of the primary cooling water, and the temperature of the primary cooling water when the heat exchange amount of the heat exchanger changes due to the load fluctuation of the heat load and / or the temperature fluctuation of the secondary cooling water. And feed-forward control means for controlling the flow rate of the secondary cooling water independently of the above.

According to the first aspect of the present invention, when there is a load fluctuation of the heat load or a temperature fluctuation of the secondary cooling water during the feedback control, the heat exchanger is replaced in response to these fluctuations. Since the amount of heat changes, a temperature drift occurs in the temperature of the primary cooling water due to overshoot and undershoot. In this case, if feedforward control is performed to control the flow rate of the secondary cooling water irrespective of the temperature of the primary cooling water, a temperature balance occurs in the heat exchanger, and temperature drift and temperature ripple are suppressed.

According to a second aspect of the present invention, in the first aspect, the feedforward control means controls the flow rate of the secondary cooling water according to the temperature of the secondary cooling water passing through the heat exchanger. It is characterized by having a water control valve.

According to a third aspect of the present invention, in the second aspect, the sensor section of the temperature expansion type water control valve bypasses a pipe line for flowing the secondary cooling water passing through the heat exchanger. It is provided in a bypass pipe having a pipe diameter smaller than the pipe diameter of the path.

According to the second and third aspects of the present invention, an inexpensive temperature expansion type water control valve is used for feedforward control, so that manufacturing costs can be reduced.

The invention described in claim 4 is the first to third aspects of the present invention.
The heat load is a laser medium of a solid-state laser oscillator.

According to a fifth aspect of the present invention, in accordance with the fourth aspect, the primary cooling water is pure water, and the closed loop through which the primary cooling water circulates has a purity of the primary cooling water. It is characterized by providing an ion exchange resin for maintaining.

According to the fourth and fifth aspects of the present invention, the temperature of the laser medium of the solid-state laser oscillator is kept constant.
The thermal lens effect, thermal birefringence effect, and the like can be kept uniform and constant, and laser output and beam quality can be stabilized.

The invention according to claim 6 is the invention according to claims 1 to 5
Wherein the feedback control means includes an open / close type electromagnetic water control valve for flowing and blocking the flow of the secondary cooling water.

According to the sixth aspect of the present invention, since the flow of the secondary cooling water is controlled by the feedback control means, an electromagnetic water control valve of a simple construction and a shut-off type is used. Manufacturing costs can be reduced.

[0020]

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

FIG. 1 shows a heat load cooling system according to this embodiment. The cooling system includes a tank 1 in which primary cooling water is stored. This primary cooling water circulates through the closed loop 9 returning to the tank 1 via the circulation pump 3, the heat load 5, and the heat exchanger 7, as shown by the solid arrow.
The primary cooling water is pure water, and the closed loop 9 is provided with an ion exchange resin 11 in order to maintain the purity of the primary cooling water.

The heat exchanger 7 has an open / close type electromagnetic water control valve 13.
The secondary cooling water is supplied as shown by the dotted arrow through
The secondary cooling water exchanges heat with the primary cooling water while passing through the heat exchanger 7, and is then discharged out of the system through the temperature expansion type water control valve 23. The secondary cooling water is, for example, tap water and is supplied to cool the primary cooling water. Reference numeral 15 denotes a temperature sensor, and 17 denotes a controller that opens and closes the electromagnetic water control valve 13. When the thermal load 5 is, for example, a laser medium of a solid-state laser oscillator, keeping the temperature of the laser medium constant is to keep the thermal lens effect, thermal birefringence effect and the like uniform and constant, It is indispensable to stabilize quality.

In this cooling system, the temperature of the heat load 5 can be kept constant by keeping the flow rate and temperature of the primary cooling water constant. Assuming that the pressure loss in the entire closed loop 9 of the circulation system is constant, the flow rate can be kept substantially constant by the capacity of the circulation pump 3. The temperature of the secondary cooling water is controlled by opening and closing the electromagnetic water control valve 13 via the controller 17 based on the temperature detected by the temperature sensor 15 in the tank 1 of the primary cooling water. It can be kept constant by adjusting the amount of exhaust heat. That is, while the electromagnetic water control valve 13 is closed, the temperature of the primary cooling water increases in proportion to the amount of heat applied to the heat load 5, and the electromagnetic water control valve 1
The temperature in the primary cooling water tank 1 is kept constant by lowering the temperature of the primary cooling water in proportion to the amount of heat exchanged by the heat exchanger 7 while the valve 3 is open. The temperature sensor 15, the controller 17, and the electromagnetic water control valve 13 constitute feedback control means of the closed loop 9.

In this embodiment, the above-mentioned temperature expansion type water control valve 23 is provided on the outlet side of the heat exchanger 7 forming the open loop 20. The temperature expansion type water control valve 23 includes a valve body 24 and a sensor unit 25, and the valve body 24 is provided in the secondary cooling water pipe 21. The sensor unit 25 bypasses the pipeline 21,
The bypass pipe 27 having a smaller diameter than the diameter of the pipe 21 is provided. The temperature expansion type water control valve 23 is connected to the bypass pipe 2 first.
7 restricts the minimum flow rate, the valve element 24 responds to a gentle temperature change of the secondary cooling water passing therethrough and a change in the heat load 5.
Is controlled to control the flow rate of the secondary cooling water.

The structure of the temperature expansion type water control valve 23 is such that a medium such as gas sealed in
The opening degree of the temperature expansion type water control valve 23 is automatically adjusted by utilizing the characteristic of expansion and contraction depending on the temperature of the secondary cooling water flowing through the water, and is generally available at a relatively low cost. The temperature expansion type water control valve 23 including the sensor section 25 constitutes a feed forward control means.

Next, the operation will be described with reference to FIG.

In this embodiment, the primary cooling water such as pure water circulates in the closed loop 9 in the direction of the arrow, and the heat load 5 is cooled by the primary cooling water. Also, secondary cooling water such as tap water is supplied to the heat exchanger 7 of the open loop 20 in the direction of the arrow, heat exchange is performed in the heat exchanger 7, and primary cooling water for cooling the heat load 5 is supplied. Cooled.

The temperature in the primary cooling water tank 1 is detected by the sensor 1
If the temperature is detected at 5 and the detected temperature is lower than the predetermined temperature, the electromagnetic water control valve 13 is closed via the controller 17 and the supply of the secondary cooling water to the heat exchanger 7 is stopped. . While the electromagnetic water control valve 13 is closed, the temperature of the primary cooling water increases in proportion to the amount of heat applied to the heat load 5. When the temperature of the primary cooling water rises and reaches a predetermined temperature, the electromagnetic water control valve 13 is opened via the controller 17 and the supply of the secondary cooling water to the heat exchanger 7 is started. . While the electromagnetic water control valve 13 is open, the temperature of the primary cooling water decreases in proportion to the amount of heat exchanged between the primary cooling water and the secondary cooling water by the heat exchanger 7. By adjusting the amount of heat exhausted from the secondary cooling water to the outside of the system in this manner, the temperature in the tank 1 of the primary cooling water is kept substantially constant. The above is the feedback control.

According to this embodiment, the heat exchanger 7
When the heat load 5 is the maximum and the temperature of the inlet side of the heat exchanger 7 of the secondary cooling water is the maximum, the exchange heat amount is set so that the heat exchange can be performed with a margin. Therefore, in this case, the maximum flow rate of the secondary cooling water becomes considerably large.

Therefore, when the feedback control is performed in the region A where the heat exchange efficiency of the heat exchanger 7 is low, for example, when the heat load 5 is large or the temperature of the secondary cooling water is high, the primary cooling in the tank 1 is performed. For example, a large “temperature ripple” as shown in FIG. 6 and a large “temperature drift” due to overshoot occur in water. On the other hand, when the feedback control is performed in the region B where the heat exchange efficiency of the heat exchanger 7 is high, such as when the heat load 5 is small or the temperature of the secondary cooling water is low, the tank 1 Large "temperature ripple" occurs in the primary cooling water,
Undershoot causes large "temperature drift".

In this embodiment, the load fluctuation of the heat load 5
When the exchanged heat amount of the heat exchanger 7 changes due to the temperature fluctuation of the secondary cooling water, feedforward control for controlling the flow rate of the secondary cooling water is performed regardless of the temperature of the primary cooling water.

This control is controlled by the temperature expansion type water control valve 23.
For example, when a large “temperature drift” occurs due to the overshoot, the temperature of the secondary cooling water on the outlet side of the heat exchanger 7 increases.
(FIG. 1), and according to this temperature, the valve element 24
Is controlled in the opening direction. According to this, since the flow rate of the secondary cooling water increases, for example, the area A shown in FIG. 6 shifts to the area C where the heat load 5 and the exchanged heat amount are balanced. Is performed. If a large “temperature drift” occurs due to undershoot, the temperature of the secondary cooling water on the outlet side of the heat exchanger 7 becomes low.
(FIG. 1), and according to this temperature, the valve element 24
Is controlled in the closing direction. According to this, since the flow rate of the secondary cooling water decreases, for example, the region B shown in FIG.
From the area C where the heat load 5 and the exchanged heat quantity are balanced.
The heat exchange in the heat exchanger 7 is performed in this region C.

As described above, in the present embodiment, the overshoot / undershoot of the temperature of the primary cooling water, that is, the “temperature drift” is suppressed.

According to the result of an experiment relating to the present embodiment regarding "temperature ripple", the conventional control using only feedback control generates a temperature ripple of about 3.7 ° C. as shown in FIG. In the control according to the present embodiment to which the forward control is added, as shown in FIG.
A temperature ripple of 8 ° C. occurs, and in this embodiment, about 1/4
It has been found that "temperature ripple" can be reduced to a certain extent.

Although the present invention has been described based on one embodiment, it is apparent that the present invention is not limited to this.

For example, a variable opening valve is adopted as the electromagnetic water control valve 13, and in performing feedforward control, the temperature of the secondary cooling water is detected by a temperature sensor (not shown), and based on this temperature, Thus, it is possible to control the valve opening of the electromagnetic water control valve 13. In this case, the temperature expansion type water control valve 23
Has the advantage that it is unnecessary.

[0037]

According to the first aspect of the present invention, the feedforward control for controlling the flow rate of the secondary cooling water is performed irrespective of the temperature of the primary cooling water. Even if there is a fluctuation in the temperature of the secondary cooling water, the exchange heat of the heat exchanger does not change in response to these fluctuations, and the temperature balance in this heat exchanger is maintained.
Temperature drift and temperature ripple are suppressed.

According to the second and third aspects of the present invention, an inexpensive temperature expansion type water control valve is used for feedforward control, so that manufacturing costs can be reduced.

According to the fourth and fifth aspects of the present invention, the temperature of the laser medium of the solid-state laser oscillator is kept constant.
The thermal lens effect, thermal birefringence effect, and the like can be kept uniform and constant, and laser output and beam quality can be stabilized.

According to the sixth aspect of the present invention, since the feedback control means controls the flow of the secondary cooling water, the electromagnetic water control valve having a simple structure of a flow-through / shut-off type is used. Manufacturing costs can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a heat load cooling system according to the present invention.

FIG. 2 is a block diagram of the same.

FIG. 3 is a diagram showing a measurement result of a temperature ripple in a tank according to the embodiment.

FIG. 4 is a view showing a measurement result of a temperature ripple in a tank according to a conventional technique.

FIG. 5 is a configuration diagram showing a conventional thermal load cooling system.

FIG. 6 is a diagram showing temperature fluctuation of primary cooling water.

FIG. 7 is a diagram showing characteristics of a general heat exchanger.

FIG. 8 is a diagram showing characteristics of a general heat exchanger.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tank 3 Circulation pump 5 Heat load 7 Heat exchanger 9 Closed loop 11 Ion exchange resin 13 Electromagnetic water control valve 15 Temperature sensor 17 Controller 20 Open loop 21 Secondary cooling water pipe 23 Temperature expansion type water control valve 24 Valve 25 Sensor part 27 Bypass pipe

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[Procedure amendment]

[Submission date] December 11, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

[0010]

According to the first aspect of the present invention,
The primary cooling water that directly cools the heat load is circulated through a closed loop through a heat exchanger, and the heat exchanger is supplied with secondary cooling water that cools the primary cooling water. In the heat load cooling system for cooling, the temperature of the primary cooling water is detected, and the amount of heat exchanged in the heat exchanger is changed by controlling the flow rate of the secondary cooling water based on the detected temperature. Feedback control means for maintaining and controlling the temperature of the heat exchanger and the heat exchanger
When a change in the amount of heat exchanged by the heat exchanger is detected due to a change in the load of the heat load and / or a change in the temperature of the secondary cooling water due to the temperature of the secondary cooling water, the temperature is not related to the temperature of the primary cooling water. Feed forward control means for controlling the flow rate of the secondary cooling water.

Claims (6)

[Claims] 1. A primary cooling water for directly cooling a heat load is circulated through a closed loop through a heat exchanger, and a secondary cooling water for cooling the primary cooling water is supplied to the heat exchanger. In the heat load cooling system that indirectly cools the heat load, the amount of heat exchanged by the heat exchanger is changed by detecting the temperature of the primary cooling water and controlling the flow rate of the secondary cooling water based on the detected temperature. Feedback control means for maintaining and controlling the temperature of the primary cooling water to be constant, and when the heat exchange amount of the heat exchanger changes due to a load fluctuation of the heat load and / or a temperature fluctuation of the secondary cooling water. A feed-forward control unit for controlling a flow rate of the secondary cooling water irrespective of a temperature of the primary cooling water. 2. The feed-forward control means includes a temperature expansion type water control valve for controlling a flow rate of the secondary cooling water according to a temperature of the secondary cooling water passed through the heat exchanger. 2. The heat load cooling system according to 1. 3. A bypass line having a pipe diameter smaller than a pipe diameter of a pipe through which a secondary cooling water flowing through a heat exchanger passes through a sensor section of the temperature expansion type water control valve. 3. The heat load cooling system according to claim 2, wherein 4. The heat load cooling system according to claim 1, wherein the heat load is a laser medium of a solid-state laser oscillator. 5. The primary cooling water is pure water, and the closed loop in which the primary cooling water circulates is provided with an ion exchange resin for maintaining the purity of the primary cooling water. The heat load cooling system according to claim 4. 6. The control device according to claim 1, wherein the feedback control means includes an open / close type electromagnetic water control valve for flowing and blocking the flow of the secondary cooling water.
The heat load cooling system according to the paragraph.