JP3308601B2 - Chilled water temperature control device of absorption refrigerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for controlling the temperature of chilled water in an absorption refrigerator, and more particularly to an apparatus for controlling the outlet temperature of chilled water obtained from an evaporator.

[0002]

2. Description of the Related Art Such cold water is used, for example, for cooling. Conventionally, a chilled water temperature control device using a double effect absorption refrigerator detects the outlet temperature of the chilled water and controls the flow rate of the heat source steam supplied to the high-pressure regenerator based on the deviation between the detected temperature and a target value. The outlet temperature is configured to be kept constant at a target value.

[0003]

In such prior art, since the flow rate of the heat source steam is controlled by detecting a change in the outlet temperature of the chilled water, when the inlet temperature of the chilled water changes, and When the flow rate of the heat source vapor changes, even if the flow rate of the heat source vapor is controlled, the reaction cannot be performed immediately because the rate of generation of the refrigerant, that is, the rate of rise in the concentration of the absorbent, is low due to the principle of the absorption refrigerator. Since a certain amount of dead time has occurred, the temperature of the cold water outlet cannot be stably maintained at a constant value.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a quick and sufficient follow-up control even when a load fluctuation occurs due to a change in inlet temperature or flow rate of a fluid to be cooled such as chilled water. It is an object of the present invention to provide a chilled water temperature control device for an absorption refrigerator that can be obtained.

[0005]

SUMMARY OF THE INVENTION The present invention provides an outlet temperature detector for detecting an outlet temperature T1 of chilled water cooled by an evaporator, an inlet temperature detector for detecting an inlet temperature T2 of the chilled water, Flow rate detector for detecting the flow rate of water, an absorbent heating means provided in a regenerator (high temperature regenerator in the case of a double effect type), and outputs of an outlet temperature detector, an inlet temperature detector, and a flow rate detector And the outlet temperature T1 and the inlet temperature T2
Feed-forward control of the amount of heat heated by the absorbent heating means so that the amount of heat corresponds to the cold water load (= (T2−T1) · Q1) which is the product of the difference ΔT (= T2−T1) and the flow rate Q1. A first control means for changing the pressure and a regenerator (or a high-temperature regenerator in the case of a double effect type) for detecting the temperature of the absorbent from the regenerator (or a regenerative pressure detection for detecting the pressure of the regenerator) Device), target value creating means for creating a target value of the temperature of the absorbent (or the pressure of the regenerator) in response to the outputs of the outlet temperature detector, the inlet temperature detector, and the flow rate detector; Temperature detector (or regenerator pressure detector)
PID control is performed in response to each output of the first control means and the target value creating means so that the difference between the detected temperature of the absorbent (or the pressure of the regenerator) and the target value becomes zero. Control means for correcting the control operation according to the above, a flow control valve for controlling the flow rate of the cooling water of the absorber, and the cooling water flow rate increases when the outlet temperature T1 rises in response to the output of the outlet temperature detector. And a third control means for controlling the flow control valve so as to provide a chilled water temperature control device for the absorption refrigerator.

Further, the present invention is characterized in that the second control means includes a calculation means for correcting the target value to be high so that the cooling water flow rate is less than the allowable maximum flow rate Q21 in a steady state.

Further, the present invention is characterized in that the second control means includes an arithmetic means for correcting the target value to be low so that the amount of heat heated by the absorbing liquid heating means does not exceed a predetermined upper limit value in a steady state. I do.

[0008]

According to the present invention, in the double effect absorption refrigerator and the single effect absorption refrigerator, in order to improve the response speed of the temperature control of the cold water, the outlet temperature T1 of the cold water, the inlet temperature T2, The feedforward control is performed by the first control means by changing the heating heat quantity by the absorbing liquid heating means so that the heat quantity corresponding to the cold water load which is the product (T2−T1) · Q1 of the flow rate Q1 is obtained. In order to finely adjust the amount of heating by the feedforward control, that is, the flow rate of heat source such as steam or fuel for a burner as a heat source, a regenerator corresponding to a chilled water load (a high temperature regenerator in the case of a double effect type) is used. Absorbent temperature (or regenerator pressure)
Is created by the target value creation means, and PID control is performed by the second control means so that the detected absorption liquid temperature (or pressure of the regenerator) becomes the target value. Since the operation of the first and second control means has a time delay of, for example, 10 to 15 minutes, a third control means is provided to further enhance the responsiveness of the chilled water load. Opens a flow control valve for controlling the flow rate of the cooling water such that the flow rate of the cooling water in the absorber is increased when the cold water outlet temperature T1 rises. When the chilled water outlet temperature T1 rises in this way, the flow rate of the chilled water in the absorber is increased, whereby the evaporation of the refrigerant in the evaporator is promoted, and fluctuations in the chilled water load can be dealt with with a large response speed. At this time, the amount of heating heat in the regenerator (or the high-temperature regenerator in the case of the double effect type) is changed by the first and second control means, so that a high-concentration absorbent is supplied to the absorber. (3) With the operation of the control means, the chilled water outlet temperature T1 decreases, thereby decreasing the flow rate of the cooling water of the absorber.

Further, according to the present invention, the flow rate of the cooling water supplied to the absorber is limited by a pump or the like, and is produced by the target value producing means so as to be less than the allowable maximum flow rate Q21 in a steady state. The set target value is corrected by, for example, a high temperature of about 1 ° C., and the target value is finely adjusted. Thus, the cooling water flow rate is equal to the allowable maximum flow rate Q
When the cooling water outlet temperature T1 rises, the cooling water flow rate can be increased to reliably improve the responsiveness.

Further, according to the present invention, the flow rate of steam or fuel serving as a heat source to be supplied to the regenerator (or the high-temperature regenerator in the case of the double effect type), and hence the amount of heating heat, is limited. The target value is corrected to a low value so as not to exceed the predetermined upper limit value in the steady state, thereby reliably achieving the responsiveness when the chilled water load increases.

[0011]

FIG. 1 is an overall system diagram of an embodiment of the present invention. The heat transfer tube 3 provided in the evaporator 2 of the double effect absorption refrigerator is usually supplied with cold water as a fluid to be cooled at, for example, 12 to 13 ° C. from the pipe line 4.
The cooled water thus cooled, for example at 5 ° C., is supplied via line 5 from a pump 6 for cooling or the like. The pipe line 5 is provided with an outlet temperature detector 7 for detecting the outlet temperature of the cold water.
The outlet temperature T1 of the chilled water is always a predetermined temperature regardless of the change of the inlet temperature T2 in the chilled water pipe 4 and the change of the chilled water flow rate Q1, that is, the chilled water load fluctuation.
That is, the temperature is kept at 5 ° C. as described above.

The operation principle of the double effect absorption refrigerator will be described. The refrigerant liquid sprayed from the nozzle 8 onto the heat transfer tube 3 in the evaporator 2 evaporates by removing heat from the cold water passing through the heat transfer tube 3, and the evaporated refrigerant vapor is absorbed by the suction of the absorber 9. It is guided to the vessel 9 and is sprayed from the nozzle 11 onto the outer surface of the heat transfer tube 10 to be absorbed by the concentrated solution sprayed. The heat absorbed during the absorbing operation is removed by the cooling water flowing through the heat transfer tube 10 from the cooling tower or the like supplied through the pipe 12 and flows through the pipe 13. The absorbing solution whose concentration has been reduced by absorbing the refrigerant is sent from the storage section 14 to the high-temperature regenerator 19 via the low-temperature heat exchanger 16 and the high-temperature heat exchanger 18 by the regenerator pump 15. In the low-temperature heat exchanger 16, the thinned absorption solution is heated by the high-temperature concentrated solution returned from the low-temperature regenerator 21, and in the high-temperature heat exchanger 18 is heated by the intermediate-concentration high-temperature solution from the high-temperature regenerator 19. You.

The dilute solution that has entered the high-temperature regenerator 19 is heated by the heat source vapor from the high-pressure pipe 23 in the heat transfer tube 22, boiled, concentrated, and increased in concentration to an intermediate concentration. The solution having the increased concentration enters the low-temperature regenerator 21 via the high-temperature heat exchanger 18. The refrigerant vapor generated in the high-temperature regenerator 19 is guided into the heat transfer tube 24 provided in the low-temperature regenerator 21, and heated by the high-temperature regenerator 19.
The solution of intermediate concentration in is boiled and concentrated to a high concentration. This high-concentration solution is sprayed to the heat transfer tube 10 from the nozzle 11 provided in the absorber 9 via the pump 25.

The refrigerant vapor generated in the high-temperature regenerator 19 flows from the heat transfer tube 24 of the low-temperature regenerator 21 to the nozzle 27 of the condenser 26.
, And is cooled and condensed by the cooling water of the heat transfer tube 28 via the pipe 12 from a cooling tower or the like flowing through the heat transfer tube 28 together with the refrigerant vapor generated by the low-temperature regenerator. The refrigerant liquid condensed in the condenser 26 is scattered from the nozzle 8 of the evaporator 2 to the heat transfer tube 3 through the pipe 30 from the storage portion 29 and is injected. The absorbing solution in the absorber 9 is supplied to the nozzle 11 from the storage section 14 by the absorber pump 32.

In the evaporator 2, the refrigerant stored in the storage section 34 is supplied to a nozzle 38 provided in the evaporator 2 via a refrigerant pump 36 and a pipe 37, and
Sprayed and circulated.

A temperature detector 40 for detecting the inlet temperature T2 of the cold water is provided in the middle of the pipe 4 for supplying the cold water to be cooled to the evaporator 2. The flow rate of the cold water is detected by a flow rate detector 45 provided in the pipe 5. An absorption liquid temperature detector 43 for detecting the temperature of the absorption liquid is interposed in the middle of a pipe 42 for guiding the intermediate concentration absorption liquid from the high temperature regenerator 19 to the heat exchanger 18. In the case of the pressure control method of the regenerator, a pressure detector 64 is interposed in the refrigerant vapor line 63 of the high-temperature regenerator 19. Further, a flow control valve 44 is interposed in the pipe 13 to control the flow rate of the cooling water of the absorber 9. Heat transfer tube 22 provided in high temperature regenerator 19
A flow control valve 46 is interposed in the pipe line 23 into which steam as a heat source is supplied.

FIG. 2 is a block diagram showing an electrical configuration of one embodiment of the present invention shown in FIG. The feed-forward control is performed by the first control means 48 in order to improve the response speed to the load fluctuation of the chilled water cooled by the evaporator 2. Temperature detector 7
Of the chilled water outlet temperature T1 detected by the
0 and the chilled water flow rate detected by the flow rate detector 45 are determined by the first control means 48.
And the temperature difference ΔT between the inlet and outlet of the cold water (= T2−T
Calculate the chilled water load, which is the product of (1) and the flow rate Q1 (T2−T1) · Q1, and correct the signal representing the calorific value corresponding to the chilled water load by the signal from the line 49 as described below. Then, a signal is given to the steam flow control valve 46 via the line 50 to change the opening of the flow control valve 46 by feedforward control.

FIG. 3 is a graph for explaining the operation of the first control means 48. Lines 51 and 52 are obtained corresponding to the difference ΔT between the outlet temperature T1 of the chilled water and the inlet temperature T2 of the chilled water in relation to the flow rate V1 of the heat source steam supplied to the line 23 and the flow rate Q1 of the chilled water. In the first control means 48,
When the chilled water flow rate Q1 is the value Q11 and ΔT is 8 ° C. as shown by the line 51, the flow rate of the heat source steam is the value V1.
A signal for obtaining 1 is obtained. The steam supplied to the pipe 23 may be a saturated steam of 180 ° C. and 8 kg / cm ² .

A second control means 53 is provided for finely adjusting the signal representing the flow rate of the steam, which is the above-mentioned flow rate value V11, which is calculated and provided by the first control means 48. The target value creation circuit 54 includes the temperature detectors 7 and 40 and the flow detector 4.
5 in response to each output from the above-mentioned chilled water load (T2-
T1) · Q1 is obtained by calculation, and a target value T4 of the temperature of the intermediate-concentration absorbent guided to the pipe 42 from the high-temperature regenerator 19 corresponding to the cold water load is obtained from the line 55 shown in FIG. The target value T4 of the absorption liquid temperature obtained by the target value creation circuit 54 is corrected after the target value of the absorption liquid temperature is finely adjusted by, for example, a range of + 1 ° C. to −1 ° C. It is provided to a subtraction circuit 57.
The output of the absorption liquid temperature detector 43 provided in the pipe 42 is given to the subtraction circuit 57. Second control means 53
Responds to the output of the subtraction circuit 57,
The proportional and integral control is performed so that the difference between the temperature of the absorbing liquid detected by the step 3 and the target value corrected by the calculating means 56 becomes zero, and the output is supplied from the line 49 to the first controlling means 48. Thus, cascade control is performed.
In the second control means 53, for example, the proportional control coefficient P = 200, the integration time I = 300 sec. ,
The differential control constant D = 0. In this way, negative feedback control is performed by the absorbent temperature detector 43 (or the regenerator pressure detector 64), the target value creation circuit 54, the subtraction circuit 57, and the second control means 53. In the first control means 48, the line 4
In response to the output from the second control means 53 via the control unit 9, the signal representing the opening of the steam flow control valve 46 determined according to the chilled water load is corrected. To further improve the responsiveness to the cold water load, a third control means 61 is provided. The third control means 61 responds to the chilled water outlet temperature T1 detected by the temperature detector 7 and adjusts the flow rate Q2 of the chilled water flowing through the conduits 12 and 13 of the absorber 9 according to the line 62 shown in FIG. A signal, which is obtained by calculation (or a controller) and indicates the opening of the cooling water flow control valve 44, is derived via a line 63. As a result, when the cold water outlet temperature T1 increases,
When the flow rate Q2 of the cooling water is increased, and conversely, when the outlet temperature T1 of the cooling water is lowered, the flow rate Q2 of the cooling water is reduced.
For example, when the chilled water outlet temperature T1 is increased, the flow rate Q2 of the chilled water is increased as described above, and thereby the evaporation of the refrigerant in the evaporator 2 is promoted. The outlet temperature T1 can be kept constant.

When the maximum allowable flow rate of the cooling water of the absorber 9 is Q21, the opening of the cooling water flow rate control valve 44 is set so that the cooling water flow rate is less than the maximum allowable flow rate Q21.
Must be controlled, so during normal operation,
The calculating means 56 corrects the fine adjustment by adding, for example, + 1 ° C. (or + several mmHg) to the target value T4 created by the target value creating means 54 so that the value Q22 becomes smaller than the allowable maximum flow rate Q21. . The allowable maximum flow rate Q21
Is, for example, 1,000 ton / hour, and the flow rate Q22 in a normal state is, for example, 800 ton / hour. By correcting the target value T4 to a high value as described above, the opening of the steam flow control valve 46 is corrected, and accordingly, the disclosure of the cooling water flow control valve 44 is reduced. Therefore, in normal times, the opening of the cooling water flow control valve 44 is maintained at a value less than the allowable maximum flow rate Q21 of the cooling water, whereby the opening of the cooling water flow control valve 44 is opened when the load of the cooling water suddenly increases. The flow rate of the cooling water can be increased to a value near the maximum flow rate Q21.

There is an upper limit to the flow rate of steam, which is a heat source supplied to the pipe 23, and therefore to the amount of heating heat. In a steady state, the target value is set so as not to exceed such a predetermined upper limit. The target value T4 is corrected to be low by subtracting, for example, 1 ° C. (or several mmHg) from the target value created by the creating unit 54, for example, by the arithmetic unit 56. In this manner, the flow rate Q2 of the cooling water shown in FIG.
Is determined.

FIG. 6 is an overall system diagram of another embodiment of the present invention. In this embodiment, the present invention is implemented in connection with a single-effect absorption refrigerator, and portions corresponding to the above-described embodiment are denoted by the same reference numerals. The regenerator 21a includes a heat transfer tube 22
The heat transfer tube 22 is provided with a heat source steam
And a steam flow control valve 44 is interposed in the middle of the pipe 23. Other configurations are the same as those of the above-described embodiment.

As still another embodiment of the present invention, instead of using the heat source steam, the absorbing liquid heating means of the high-temperature regenerator 19 shown in FIG. 1 and the regenerator 21a shown in FIG. And a fuel flow control valve for changing the flow rate of the liquid or gas fuel to the burner, and the opening degree of the fuel flow control valve is changed by a signal from the first control means 48 via a line 50. It may be.

[0024]

As described above, according to the present invention, the outlet temperature T1, the inlet temperature T2, and the flow rate Q of the chilled water cooled by the evaporator.
The chilled water load, which is 1, is calculated, and the absorption liquid heating means is feedforward controlled so as to have a heating heat amount corresponding to the chilled water load, and the chilled water load is adjusted in order to finely adjust the feedforward control. Create a target value for the absorbent temperature (or regenerator pressure) at the outlet from the corresponding regenerator (or high-temperature regenerator for the dual-effect type),
When the chilled water load is increased and the chilled water outlet temperature T1 is increased in order to further improve the responsiveness to the chilled water load by performing the PID control so as to reach the target value, the cooling water supplied to the absorber is increased. The flow control valve is controlled so as to increase the flow rate, thereby increasing the amount of refrigerant evaporated in the evaporator, and thus can follow the fluctuation of the chilled water load with a good response speed.

Furthermore, according to the present invention, the outlet water from the regenerator (or the high-temperature regenerator in the case of the double effect type) is absorbed so that the flow rate of the cooling water in the absorber is less than the allowable maximum flow rate Q21 in a steady state. The target value of the liquid temperature (or the pressure of the regenerator) is corrected to a high value, so that when the load of the chilled water is increased, the flow rate of the chilled water is increased as described above, so that the improvement of the responsiveness can be reliably achieved.

Further, according to the present invention, in order to prevent the flow rate of the heat source by the absorbing liquid heating means from excessively increasing, the temperature of the absorbing liquid (or the temperature of the regenerator) is controlled so as not to exceed a predetermined upper limit of the heating heat amount. The target value of (pressure) is corrected to be low in a steady state, so that when the chilled water load increases, it is possible to cope with a good response speed.

[Brief description of the drawings]

FIG. 1 is an overall system diagram of a double effect absorption refrigerator according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of the embodiment shown in FIG.

3 is a graph for explaining the operation of a first control means 48. FIG.

FIG. 4 is a graph for explaining the operation of a target value creating means 54;

FIG. 5 is a graph for explaining an operation of a third control means 61;

FIG. 6 is an overall system diagram of a single-effect absorption refrigerator according to another embodiment of the present invention.

[Explanation of symbols]

 2 Evaporator 3 Heat transfer tube 7 Outlet temperature detector 9 Absorber 19 High temperature regenerator 21 Low temperature regenerator 26 Condenser 40 Inlet temperature detector 43 Absorbent temperature detector 44 Cooling water flow control valve 45 Cold water flow control valve 46 Steam flow Control valve 64 Pressure detector

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-61-235654 (JP, A) JP-A-58-19669 (JP, A) JP-A-3-294758 (JP, A) JP-A-3-19658 140759 (JP, A) JP-A-4-93563 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F25B 15/00 306

Claims (3)

(57) [Claims] 1. An outlet temperature T1 of cold water cooled by an evaporator.
Temperature detector, an inlet temperature detector for detecting the cold water inlet temperature T2, a flow rate detector for detecting the flow rate of the cold water, and a regenerator (a high temperature regenerator in the case of a double effect type). And a difference ΔT between the outlet temperature T1 and the inlet temperature T2 in response to the outputs of the outlet temperature detector, the inlet temperature detector, and the flow rate detector.
(= T2-T1) and the flow rate Q1 of the chilled water load (=
(T2-T1) · Q1)
A first control means for changing the amount of heat heated by the absorption liquid heating means by feedforward control; and an absorption liquid temperature detector (for detecting the temperature of the absorption liquid from a regenerator (a high-temperature regenerator in the case of a double effect type)) Or a pressure detector that detects the pressure of the regenerator) and the target value of the absorbent temperature (or the pressure of the regenerator) in response to the outputs of the outlet temperature detector, the inlet temperature detector, and the flow rate detector. In response to the respective outputs of the target value creating means to be created, the absorbent temperature detector (or the regenerator pressure detector) and the target value creating means, the detected temperature of the absorbent (or the pressure of the regenerator) and A second control means for performing PID control such that a difference from a target value becomes zero to correct a control operation by the first control means; a flow control valve for controlling a cooling water flow rate of the absorber; Outlet temperature T1 rises in response to detector output That the cold water temperature control system of the absorption type refrigerator which comprises a third control means for controlling the flow rate control valve so that the cooling water flow rate is increased. 2. The absorption system according to claim 1, wherein the second control means includes an arithmetic means for correcting the target value to a high value such that the flow rate of the cooling water is less than the allowable maximum flow rate Q21 in a steady state. Cold water temperature control device for refrigerator. 3. The apparatus according to claim 2, wherein the second control means includes a calculation means for correcting the target value to be low so that the amount of heat of heating by the absorbing liquid heating means does not exceed a predetermined upper limit value in a steady state. 2. A chilled water temperature control device for an absorption refrigerator according to claim 1.