JPH06101928A - Control device for temperature of cold water in absorptive refrigerating apparatus - Google Patents

Abstract

PURPOSE:To obtain a cold water having an invariably specified temp. by a method wherein an absorbing liquid is heated according to load on cold water under feedforward control, PID control is conducted to raise the temp. of the absorbing liquid to the objective value and the flow amount of cooling water is controlled according to the temp. of the cold water at its outlet. CONSTITUTION:The quantity of heat required for heating an absorbing liquid in a regenerator is subjected to feedforward control by a first control means 48 so as to attain the heat quantity corresponding to the load on cold water obtained by multiplying the difference between the outlet temp. 7 and the inlet temp. 40 of the cold water cooled through an evaporator by the flow amount 45 of the cold water. The absorbing liquid is subjected to PID control by a second control means 53 to compensate for the control action of the first control means 48, so that the difference between the absorbing liquid temp. 43 and the objective temp. value produced through an objective value producing circuit 54 will become zero. When the temp. of cold water at its outlet rises, a flow amount control valve 44 for cooling water in the absorber is controlled by a third control means 61, so that the amount of the cooling water will increase. In this way a follow-up control of the load variations takes place rapidly to obtain the cold water having an invariably specified temp.

Description

Detailed Description of the Invention

[0001]

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

[0002]

Such cold water is used, for example, for cooling. Conventionally, a chilled water temperature control device using a dual-effect absorption chiller detects an outlet temperature of chilled water and controls a flow rate of a heat source steam to be supplied to a high-pressure regenerator by a deviation between the detected temperature and a target value. It is configured to keep the outlet temperature constant at the target value.

[0003]

In such a prior art, since the change of the cold water outlet temperature is detected to control the flow rate of the heat source steam, when the cold water inlet temperature is changed and the cold water is changed, Even if the flow rate of the heat source vapor is controlled when the flow rate of the heat source changes, the refrigerant generation rate, that is, the rate of increase in the concentration of the absorbing solution is low due to the principle of the absorption refrigerator, so that the reaction cannot be immediately performed. Since some dead time is generated, the temperature of the cold water outlet cannot be stably maintained at a constant value.

An object of the present invention is to enable quick and sufficient follow-up control even if the inlet temperature or flow rate of a fluid to be cooled, such as cold water, changes to cause a load change, and to obtain cold water of a desired constant temperature. It is an object of the present invention to provide a chilled water temperature control device for an absorption chiller that can be obtained.

[0005]

According to the present invention, an outlet temperature detector for detecting an outlet temperature T1 of cold water cooled by an evaporator, an inlet temperature detector for detecting an inlet temperature T2 of the cold water, and the cold water are provided. Flow rate detector for detecting the flow rate of water, the absorption liquid heating means provided in the regenerator (high temperature regenerator in case of double effect type), each output of the outlet temperature detector, the inlet temperature detector and the flow rate detector In response to the outlet temperature T1 and the inlet temperature T2
And the difference ΔT (= T2-T1) from the flow rate Q1 and the heat quantity corresponding to the cold water load (= (T2-T1) · Q1) which is the product of the flow rate Q1. And the first control means for changing the temperature, and the absorption liquid temperature detector (or the regeneration pressure detection for detecting the pressure of the regenerator) for detecting the temperature of the absorption liquid from the regenerator (the high temperature regenerator in the case of the double effect type). And a target value creating means for creating a target value of the absorbing liquid temperature (or the pressure of the regenerator) in response to each output of the outlet temperature detector, the inlet temperature detector, and the flow rate detector, and the absorbing liquid. Temperature detector (or regenerator pressure detector)
In response to the respective outputs of the target value creating means and the target value creating means, PID control is performed so that the difference between the detected temperature of the absorbing liquid (or the pressure of the regenerator) and the target value becomes zero, and the first control means is provided. When the outlet temperature T1 rises in response to the output of the second control means for correcting the control operation by the controller, the flow control valve for controlling the cooling water flow rate of the absorber, and the outlet temperature detector, the cooling water flow rate increases. A chilled water temperature control device for an absorption chiller, comprising:

Further, the present invention is characterized in that the second control means includes a calculation means for correcting the target value to a high value 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 a calculation means for correcting the target value to a low value so that the heat quantity of heating by the absorbing liquid heating means does not exceed a predetermined upper limit value in a steady state. To do.

[0008]

According to the present invention, in the double-effect absorption refrigerating machine and the single-effect absorption refrigerating machine, 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, and The feed-forward 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 with the flow rate Q1, is obtained. In order to finely adjust the above-mentioned heating amount by the feedforward control, that is, the heat source flow rate such as steam or fuel for the burner, which is the heat source, from the regenerator (high-temperature regenerator in the case of double effect type) corresponding to the cold water load. Absorbent temperature (or regenerator pressure)
The target value is generated by the target value generating means, and the second control means performs PID control so that the detected absorbing liquid temperature (or the pressure of the regenerator) becomes the target value. Since the operations by the first and second control means have a time delay of, for example, 10 to 15 minutes, a third control means is provided to further improve the responsiveness of the cold water load, and the third control means is provided. Opens the flow control valve that controls the cooling water flow rate so that the cooling water flow rate of the absorber increases when the cold water outlet temperature T1 rises. When the cold water outlet temperature T1 rises in this way, the cooling water flow rate of the absorber is increased, whereby evaporation of the refrigerant in the evaporator is promoted, and fluctuations in the cold water load can be coped with at a high response speed. At this time, the amount of heat of heating in the regenerator (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 absorbing liquid is supplied to the absorber, The cold water outlet temperature T1 decreases along with the operation of the three control means, which reduces the flow rate of the cooling water in the absorber.

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

Further, according to the present invention, there is a limit to the flow rate of steam, fuel, etc., which is a heat source to be supplied to the regenerator (high temperature regenerator in the case of the double effect type), and accordingly, the heating calorie is limited. The target value is corrected to a low value so as not to exceed the predetermined upper limit value of (1) in a steady state, and thereby the responsiveness when the chilled water load increases is reliably achieved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 normally supplied with cold water as a fluid to be cooled, for example, at 12 to 13 ° C., from the conduit 4, and the heat transfer tube 3 is
The chilled water which has been cooled through and is cooled in this way, for example, at 5 ° C., is supplied from a pump 6 through a pipe 5 for cooling or the like. An outlet temperature detector 7 for detecting the outlet temperature of the cold water is provided in the pipe line 5, and according to the present invention,
The chilled water outlet temperature T1 is a constant temperature that is always constant regardless of changes in the inlet temperature T2 and the chilled water flow rate Q1 in the chilled water pipe 4, that is, chilled water load fluctuations.
That is, it is maintained at 5 ° C. as described above.

The operating principle of the double-effect absorption refrigerator will be described. The refrigerant liquid sprayed from the nozzles 8 on the heat transfer tubes 3 in the evaporator 2 takes heat from the cold water passing through the heat transfer tubes 3 to evaporate, and the evaporated refrigerant vapor is absorbed by the suction action of the absorber 9. It is guided to the vessel 9, and is absorbed by the concentrated solution sprayed from the nozzle 11 onto the outer surface of the heat transfer tube 10. The absorbed heat during the absorbing action is removed by the cooling water supplied from the cooling tower or the like flowing through the heat transfer tube 10 via the conduit 12 and flows through the conduit 13. The absorbing solution that has absorbed the refrigerant and has a low concentration 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 diluted concentrated 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, it is heated by the intermediate concentration high temperature solution from the high temperature regenerator 19. It

The dilute solution that has entered the high temperature regenerator 19 is heated by the heat source vapor from the high-pressure conduit 23 in the heat transfer tube 22, is boiled and concentrated to have a high concentration and become 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 introduced into the heat transfer pipe 24 provided in the low temperature regenerator 21, and the high temperature regenerator 19 heated by the refrigerant vapor is introduced.
The medium-concentration solution inside boils and concentrates to a high concentration. This high-concentration solution is sprayed on 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 is transferred from the heat transfer tube 24 of the low temperature regenerator 21 to the nozzle 27 of the condenser 26.
Is condensed with the cooling water of the heat transfer tube 28 that is sprayed from the heat transfer tube 28 through the conduit 12 from the cooling tower or the like flowing in the heat transfer tube 28 together with the refrigerant vapor generated in the low temperature regenerator. The refrigerant liquid condensed in the condenser 26 is sprayed from the reservoir 29 through the pipe 30 to the heat transfer pipe 3 from the nozzle 8 of the evaporator 2. The absorbing solution of the absorber 9 is supplied from the reservoir 14 to the nozzle 11 by the absorber pump 32.

In the evaporator 2, the refrigerant stored in the storage portion 34 is supplied to the nozzle 38 provided in the evaporator 2 via the refrigerant pump 36 and the pipe line 37, and the heat transfer tube 3 is provided.
It is sprayed on and circulated.

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

FIG. 2 is a block diagram showing an electrical configuration of the embodiment of the present invention shown in FIG. The feed-forward control is performed by the first control unit 48 in order to improve the response speed with respect to the load fluctuation of the cold water cooled by the evaporator 2. Temperature detector 7
Chilled water outlet temperature T1 detected by the temperature detector 4
The cold water inlet temperature T2 detected by 0 and the cold water flow rate detected by the flow rate detector 45 are the first control means 48.
The temperature difference ΔT (= T2-T
The cold water load, which is the product (T2-T1) · Q1 of 1) and the flow rate Q1, is calculated, and the signal that is the amount of heat corresponding to the value of the cold water load is corrected 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 degree 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 cold water and the inlet temperature T2 of the cold water in relation to the flow rate V1 of the heat source steam and the flow rate Q1 of the cold water supplied to the line 23. In the first control means 48,
When the cold 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 conduit 23 may be saturated steam at 180 ° C. and 8 kg / cm ² .

The second control means 53 is provided for finely adjusting the signal representing the flow rate of the vapor which becomes the above-mentioned flow rate value V11 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 rate detector 4
In response to the respective outputs from 5 and 5, the cold water load (T2-
T1) · Q1 is calculated and obtained, and the target value T4 of the temperature of the absorbing liquid having an intermediate concentration introduced from the high temperature regenerator 19 to the pipe line 42 corresponding to the cold water load is obtained from the line 55 shown in FIG. The target value T4 of the absorbing liquid temperature obtained by the target value creating circuit 54 is finely adjusted and corrected by the calculating means 56 in the range of + 1 ° C. to −1 ° C. It is given to the subtraction circuit 57.
The subtraction circuit 57 is supplied with the output of the absorption liquid temperature detector 43 provided in the conduit 42. Second control means 53
Responding to the output of the subtraction circuit 57, the absorption liquid temperature detector 4
The proportional and integral control is carried out so that the difference between the temperature of the absorbing liquid detected by 3 and the target value corrected by the calculating means 56 becomes zero, and the output is given from the line 49 to the first controlling means 48. Thus, the cascade control is performed.
In the second control means 53, for example, the proportional control coefficient P = 200, the integration control integration time I = 300 sec. ,
The derivative control constant D = 0. In this way, the negative feedback control is performed by the absorption liquid 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 9, the signal representing the opening degree of the steam flow control valve 46 obtained in response to the cold water load is corrected. Third control means 61 is provided in order to further improve the responsiveness to the cold water load. The third control means 61 responds to the cold water outlet temperature T1 detected by the temperature detector 7 and changes the flow rate Q2 of the cooling water flowing through the pipe lines 12 and 13 of the absorber 9 in accordance with the line 62 shown in FIG. A signal representing the opening degree of the cooling water flow rate control valve 44 is obtained through calculation (or a controller) and is derived via the line 63. As a result, when the cold water outlet temperature T1 increases,
When the cooling water flow rate Q2 is increased and conversely the cooling water outlet temperature T1 is lowered, the cooling water flow rate Q2 is decreased.
For example, when the chilled water outlet temperature T1 becomes high, the flow rate Q2 of the chilled water is increased as described above, whereby the evaporation of the refrigerant in the evaporator 2 is promoted, and the chilled water is irrespective of the rapid change in the chilled water load. The outlet temperature T1 can be kept constant.

When the allowable maximum flow rate of the cooling water in the absorber 9 is Q21, the opening degree of the cooling water flow rate control valve 44 is set so that the cooling water flow rate is less than the allowable maximum flow rate Q21.
Must be controlled and therefore during normal operation
The calculation unit 56 adds, for example, + 1 ° C. (or + several mmHg) to the target value T4 created by the target value creating unit 54 so that the value Q22 is less than the maximum allowable flow rate Q21, and performs fine adjustment correction. . The allowable maximum flow rate Q21
Is, for example, 1,000 ton / hour, and the normal flow rate Q22 is, for example, 800 ton / hour. By correcting the target value T4 as described above to be high as described above, the opening degree of the steam flow control valve 46 is corrected, and thus the disclosure of the cooling water flow control valve 44 is reduced. Therefore, in normal times, the opening degree of the cooling water flow rate control valve 44 is kept at a value less than the allowable maximum flow rate Q21 of the cooling water, which allows the opening degree of the cooling water flow rate control valve 44 to be opened when the cooling water load sharply increases. It becomes possible to increase the flow rate of the cooling water to a value near the maximum flow rate Q21.

There is an upper limit to the flow rate of steam, which is the heat source supplied to the pipe line 23, and therefore to the heating heat quantity, and in a steady state, the target value is set so as not to exceed such a predetermined upper limit value of the heating heat quantity. From the target value created by the creating means 54, for example, by the calculating means 56, 1 ° C. (or several mmHg) is subtracted to correct the target value T4 low. In this way, the flow rate Q2 of the cooling water shown in FIG. 5 corresponds to the predetermined upper limit value of the amount of heat of heating by the steam as the heat source.
Lower limit value Q23 is determined.

FIG. 6 is an overall system diagram of another embodiment of the present invention. In this embodiment, the present invention is carried out in connection with a single-effect absorption refrigerator, and parts corresponding to those in the above-mentioned embodiments are designated by the same reference numerals. The regenerator 21a includes a heat transfer tube 22
The heat transfer pipe 22 is provided with
A steam flow rate control valve 44 is provided in the middle of the pipeline 23. Other configurations are the same as those in the above-mentioned embodiment.

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

[0024]

As described above, according to the present invention, the outlet temperature T1, the inlet temperature T2, and the flow rate Q of the cold water cooled by the evaporator.
The chilled water load, which is 1, is calculated, and the absorption liquid heating means is feed-forward-controlled so that the heating heat quantity corresponding to the chilled-water load is obtained, and the chilled-water load is adjusted to finely adjust the feed-forward control. Create a target value for the absorbent temperature (or pressure of the regenerator) at the outlet from the corresponding regenerator (high-temperature regenerator in the case of double-effect type).
In order to perform the PID control so as to reach the target value and further improve the responsiveness to the cold water load, when the cold water load increases and the cold water outlet temperature T1 rises, the cooling water supplied to the absorber is increased. It is possible to control the flow rate control valve so that the flow rate becomes large, thus increasing the evaporation amount of the refrigerant in the evaporator, and thus to follow the fluctuation of the cold water load with a good response speed.

Further, according to the present invention, the absorption of the outlet from the regenerator (high temperature regenerator in the case of the double effect type) is adjusted so that the cooling water flow rate of the absorber is less than the allowable maximum flow rate Q21 in the steady state. The target value of the liquid temperature (or the pressure of the regenerator) is corrected to a high value, whereby the cooling water flow rate can be increased and the responsiveness can be surely improved when the cold water load increases.

Further, according to the present invention, in order to prevent the heat source flow rate by the absorption liquid heating means from increasing too much, the absorption liquid temperature (or the regenerator's temperature should not exceed the upper limit value of the heating amount). The target value of (pressure) is corrected to a low value in a steady state, whereby a high response speed can be dealt with when the chilled water load increases.

[Brief description of 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.

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

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

FIG. 5 is a graph for explaining the operation of the 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 Absorbing liquid temperature detector 44 Cooling water flow rate control valve 45 Cold water flow rate control valve 46 Steam flow rate Control valve 64 Pressure detector

Claims (3)

[Claims] 1. An outlet temperature T1 of cold water cooled by an evaporator
Outlet temperature detector for detecting the cold water, inlet temperature detector for detecting the inlet temperature T2 of the cold water, flow rate detector for detecting the flow rate of the cold water, and regenerator (high temperature regenerator in the case of double effect type) The difference ΔT between the outlet temperature T1 and the inlet temperature T2 in response to the outputs of the absorption liquid heating means provided in the outlet temperature detector, the outlet temperature detector, the inlet temperature detector, and the flow rate detector.
Cold water load (= T2-T1) multiplied by flow rate Q1 (=
(T2-T1) · Q1)
First control means for changing the amount of heat to be 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 the regenerator (high temperature regenerator in the case of the double effect type) ( Or the pressure detector that detects the pressure of the regenerator), and the target value of the absorbing liquid temperature (or the pressure of the regenerator) in response to the output of the outlet temperature detector, the inlet temperature detector, and the flow rate detector. In response to each output of the target value creation means to be created, the absorption liquid temperature detector (or regenerator pressure detector) and the target value creation means, the detected absorption liquid temperature (or regenerator pressure) and PID control so that the difference from the target value becomes zero, second control means for correcting the control operation by the first control means, a flow rate control valve for controlling the cooling water flow rate of the absorber, and outlet temperature The outlet temperature T1 rises in response to the output of the detector 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 formula according to claim 1, wherein the second control means includes a calculation means for correcting the target value to a high value so that the cooling water flow rate is less than the allowable maximum flow rate Q21 in a steady state. Chilled water temperature control device for refrigerator. 3. The second control means includes an arithmetic means for correcting the target value to a low value so that the amount of heat to be heated by the absorption liquid heating means does not exceed a predetermined upper limit value in a steady state. 1. The cold water temperature control device for an absorption refrigerator according to 1.