JP4074955B2 - Cooling water flow rate control method for absorption chiller water heater - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cooling water flow rate control method for an absorption chiller / heater.
[0002]
[Prior art]
In the absorption chiller / heater, a cooling water variable flow rate system that changes the cooling water flow rate in response to fluctuations in the chilled / hot water load is employed. FIG. 2 shows a configuration of the cooling water variable flow rate system, and FIG. 4 shows a conventional control flowchart of the cooling water variable flow rate system.
[0003]
The illustrated controller, chiller inlet temperature T _CI of the cooling _water, chiller outlet temperature T _CO and high-temperature regenerator is input a signal indicating the solution temperature T _G in (HGE), the cooling water chiller The number of revolutions of the cooling water pump is controlled by the inverter so that the outlet temperature _TCO becomes the target temperature T, and the cooling water flow rate is changed. Further, as shown in FIG. 4, when elevated above the upper limit temperature T ₁ of the solution temperature T _G is set in advance in the hot regenerator, the flow rate of the cooling water to the rated maximum flow rate (100% flow) Protection control to return is performed.
[0004]
Regarding the control method for changing the cooling water flow rate based on the cooling / cooling water heater outlet temperature of the absorption chiller, for example, the examples shown in Japanese Patent Application Laid-Open Nos. 8-159596 and 2001-66011 are given. is there.
[0005]
[Problems to be solved by the invention]
However, independent of the variable flow rate control, as shown in FIG. 5, as the control of the chilled water heater, the cooling tower fan motor is started and stopped based on the chilled water inlet temperature of the cooling water, and the cooling water temperature is It prevents it from falling too much. That is, the cooling tower fan and chiller inlet temperature of the cooling water is lowered to temperature T ₂ set in advance is stopped, the cooling tower fan is stopped, chiller inlet temperature of the cooling water gradually increases. Along with this, the temperature of the cooling water cooler / heater outlet also rises. When the cooling water outlet temperature of the cooling water exceeds a preset control target temperature T, the rotational speed of the cooling water pump increases and the cooling water flow rate increases due to the variable flow rate control. Also, when the chiller inlet temperature of the cooling water exceeds the temperature T ₃ which is set in advance, cooling tower fan is activated, chiller inlet temperature of the cooling water starts to drop.
[0006]
Thus, the cooling water flow rate is not stable due to the fluctuation of the cooling water temperature accompanying the start / stop of the cooling tower fan.
[0007]
In FIG. 6, the example of a fluctuation | variation of the chiller / heater inlet temperature of the cooling water, the chiller / heater outlet temperature, and the cooling water flow rate in the conventional control is shown. As shown in the figure, the flow rate of the cooling water varies with the variation of the cooling water outlet temperature, and the fluctuation range of the cooling water chiller outlet temperature is suppressed by varying the cooling water flow rate. As a result, there is a problem in that the cooling water flow rate increases and the power cost of the cooling water pump increases.
[0008]
An object of the present invention is to reduce power costs while ensuring good stability of operation of an absorption chiller / heater.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a cooling tower fan that circulates cooling water to an absorption chiller / heater and cools the absorption chiller / heater according to the level of the cooling water chiller / heater inlet temperature. A method of controlling an absorption chiller / heater having a stopping procedure, wherein the cooling water outlet temperature flowing out of the absorption chiller / hot water machine is detected as a cooling water chiller / heater outlet temperature by moving average for a set time. , at a predetermined control period, when the chiller Atsushi Ideguchi exceeds the temperature range preset increases the coolant flow rate, when the chiller Atsushi Ideguchi has not reached the temperature range the cooling water flow rate reduces when the chiller Atsushi Ideguchi is within the temperature range, and executes the chiller outlet temperature control to maintain the cooling water flow rate at that time.
[0010]
By controlling as described above, it is possible to reduce the fluctuation of the cooling water flow rate due to the fluctuation of the cooling water temperature caused by the start / stop of the cooling tower fan. Therefore, the number of times of increasing the coolant flow rate is reduced, and there is an effect of reducing the power cost while ensuring good operation stability.
[0011]
It is desirable that the rate of increase / decrease in the cooling water amount is set in advance as to what percentage of the rated flow rate is increased / decreased.
[0012]
Also, when the chiller Atsushi Ideguchi has not reached the temperature range, when determining whether the cooling water flow rate at that time exceeds the minimum flow amount set in advance, above the minimum flow rate, cooling It is desirable to reduce the water flow rate and maintain the cooling water flow rate at that time when the flow rate is below the minimum flow rate .
[0013]
Further, when the solution temperature in the high temperature generator of the absorption chiller heater exceeds a predetermined control target value, instead of the chiller Atsushi Ideguchi control, sets the cooling water flow rate to the rated maximum flow rate When the solution temperature control is executed and the solution temperature is equal to or lower than the control target value , it is desirable to execute the cold / hot water outlet temperature control .
[0014]
Further, when the solution temperature is below the control target Ne以, before running chiller outlet temperature control, to compare the time that is set in advance and the elapsed time from the previous flow rate change, the elapsed time is the set time when on the following, run the chiller outlet temperature control, when the elapsed time is less than time setting, it is desirable to the cooling water flow as it is.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0016]
FIG. 2 shows an overall configuration of an absorption chilled / hot water device to which the present invention is applied, and FIG. 1 shows a flowchart of cooling water flow rate control according to an embodiment of the present invention. The illustrated flowchart shows a control procedure of cooling water flow rate control (cooling water variable flow rate control) during cooling operation of the absorption chiller / heater.
[0017]
The absorption chiller / heater shown in FIG. 2 includes an absorption chiller / heater 1 with a high-temperature regenerator HGE2, a cooling water return pipe 11 connected to a cooling water outlet of the absorption chiller / hot water machine, and the cooling water return pipe. A cooling tower 4 provided with a cooling water inlet connected to the downstream end of the passage 11 and driven by a fan motor M3, a cooling water outlet of the cooling tower 4, and a cooling water of the absorption chiller / heater 1 Cooling water at the cooling water outlet position of the absorption chiller-heater in the cooling water return pipe 11 connected to the cooling water containing side pipe 12 having an inlet connected and a cooling water pump 7 whose rotation speed is controlled by the inverter 6 A temperature sensor 8 that detects and outputs the temperature (cooling / heating water machine outlet temperature T _CO ), and a cooling water temperature (cooling / heating water machine inlet temperature T at the cooling water inlet position of the absorption chilling water heating / cooling water inlet side pipe 12. _Ci )) detecting and outputting the temperature sensor 9; A temperature sensor 10 that detects and outputs the solution temperature _TG in the high-temperature regenerator 2, and is connected to these temperature sensors 8, 9, 10, and the inverter 6 and the fan motor M3 are connected based on the outputs of these temperature sensors. And a controller 5 to be controlled.
[0018]
Each temperature sensor outputs a detection value at intervals of 1 minute and is stored in the memory of the controller 5. Each temperature sensor may output analog signals continuously, and the controller 5 may sample at 1 minute intervals and store the data in the memory of the controller.
[0019]
Incidentally, the controller 5, when raised above the upper limit temperature T ₁ of the solution temperature T _G is set in advance in the high-temperature regenerator 2, regardless of the value of chiller heater outlet temperature T _CO, coolant The flow rate is controlled to return to the rated maximum flow rate (100% flow rate). The controller 5 also independently of the chiller outlet temperature of the cooling water, chiller inlet temperature of the cooling water stops cooling tower fan and decreases to temperature T ₂ that is set in advance, hot and cold water in the cooling water beyond the temperature T ₃ of the machine inlet temperature is set in advance, is configured to start the cooling tower fan.
[0020]
An example of a control procedure when the present invention is applied to the apparatus having the above configuration will be described with reference to FIG. Note that the procedure 1 indicated by (1) in FIG. 1 is for displaying the repetition of the procedure, and does not mean a specific operation.
[0021]
During the cooling operation, the controller compares the input solution temperature _TG in the high-temperature regenerator with a preset upper limit temperature T ₁ at a predetermined time interval (in this embodiment, one minute interval). It is determined whether it is larger (procedure 2). That is, the control cycle shown in FIG. 1 is executed at 1-minute intervals.
[0022]
If the detected temperature of the solution T _G is greater than the upper limit temperature T ₁ of a preset, go to step 3, the controller, as a protective control, maximum rated cooling water flow rate is the rotational speed of the cooling water pump via the inverter Set to the number of revolutions at which the flow rate (100% flow rate) is achieved. When the number of rotations of the cooling water pump is set, the procedure returns to procedure 1 and the above procedure is repeated.
[0023]
If the detected temperature of the solution T _G is the upper limit temperature T ₁ of less that is set in advance, go to step 4, the controller, the amount of time elapsed since the modified last cooling water flow rate, or t minutes which is set in advance Determine whether or not. If the elapsed time is not equal to or longer than the preset t minutes, the procedure proceeds to step 5, and the procedure returns to step 1 with the cooling water flow rate unchanged, and the above procedure is repeated. The time t in the procedure 4 is to be referred to as a control cancellation time, and is set in order to prevent the flow rate fluctuation signal from being continuously transmitted due to a response delay of the cooling water temperature change. How long the length is set may be determined by the amount of water retained in the cooling water system, but in this embodiment, the length is set to 15 minutes.
[0024]
Elapsed time, if it is more than t minutes, which is set in advance, go to step 6, the chiller heater outlet temperature T _CO, the target temperature range _{T 4} ~T 5 (T ₄ which is set in advance _<T Compare with ₅ ). T ₄ and T ₅ were set according to the following policy. T ₄ was an arbitrary temperature below the cooling water inlet temperature during rated operation in equipment design, and T ₅ was also an arbitrary temperature below the cooling water outlet temperature during rated operation. For example, in the present embodiment, T ₄ is set to 32 ° C. with respect to the cooling water inlet temperature 32 ° C. during rated operation, and T ₅ is set to 34 ° C. with respect to the cooling water outlet temperature 37.5 ° C. during rated operation.
[0025]
This control is performed in a state where there is no adverse effect on the operation of the equipment even if the cooling water temperature is low due to low load operation or low outside air temperature and the cooling water flow rate falls below the design flow rate (rated maximum flow rate = 100%). Is reduced. For this reason, T ₄ and T ₅ are set so that the operation is performed under a condition where a slight margin is further provided for the rating (design) condition.
[0026]
Controller, the moving average value of the past t _m min the cooling water outlet temperature of the cooling water flowing out from the absorption chiller heater 1 and chiller outlet temperature T _CO. In this embodiment, the t _m min to min 15, the detection value of every minute of the past 15 minutes, that is, the average of the detected values of the 15 points and chiller outlet temperature T _CO. Since the temperature detection interval is every one minute, this chiller / heater outlet temperature _TCO is also calculated every minute.
[0027]
As a result of the comparison in step 6, if T ₄ ≦ T _CO ≦ T ₅ , that is, if the value of T _CO is determined to be within the target temperature range, the process proceeds to step 7, and the flow rate of the cooling water remains unchanged and the process returns to step 1. Repeat the above procedure.
[0028]
As a result of the comparison, if it is determined that T ₅ <T _CO , that is, the value of T _CO exceeds the target temperature range, the procedure proceeds to step 8, and the controller sets the ratio of the cooling water flow rate (the maximum rated value). The number of revolutions of the cooling water pump is increased via the inverter so as to increase (X% of the flow rate, 10% in the present embodiment). When the number of rotations of the cooling water pump is set, the procedure returns to procedure 1 and the above procedure is repeated.
[0029]
As a result of the comparison, if it is determined that T _CO <T ₄ , that is, the value of T _CO has not reached the target temperature range, the procedure proceeds to step 9, and the controller sets the minimum flow rate of the cooling water at that point in time. Whether or not the flow rate (50% of the rated maximum flow rate in this embodiment) has been exceeded is determined based on the number of revolutions at that time (instruction signal to the inverter or signal of a revolution number transmitter not shown). When the cooling water flow rate is 50% or less of the rated flow rate, the cooling water flow rate is left as it is and the procedure returns to Procedure 1 and the above procedure is repeated. If the cooling water flow rate exceeds 50% of the rated flow rate, proceed to step 10 and the controller cools through the inverter so that the cooling water flow rate is reduced by a preset percentage (X% of the rated maximum flow rate). Reduce water pump speed. When the number of rotations of the cooling water pump is set, the procedure returns to procedure 1 and the above procedure is repeated.
[0030]
In the present embodiment, the flow rate control range is 50 to 100% of the rated maximum flow rate, and the flow rate is reduced in increments of X%. Therefore, if there is no flow rate of (50 + X)% at the minimum, then X% It cannot be reduced. Therefore, as described above, it is determined whether or not the cooling water flow rate exceeds 50% of the rated flow rate, and after it is confirmed that the cooling water flow rate exceeds 50%, the flow rate reduction process is performed.
[0031]
When the flow rate reduction process of X% is performed when the flow rate is 50 + α (0 <α <X)%, the controller may be configured to automatically perform the flow rate reduction process of α%.
[0032]
In setting the unit X% of the increase / decrease in the cooling water flow rate, the following points were taken into consideration.
[0033]
First, when the amount of fluctuation is too large, the control is not stable. When the fluctuation amount is too small, the control is stabilized, but the flow rate decrease is slow and the energy saving effect is reduced. Also, when the flow rate needs to be increased, the response is slow, and protection control by _TG works. In this embodiment, X% is set to 10% in consideration of these points, but it is desirable to set according to the size and characteristics of the plant.
[0034]
FIG. 3 schematically shows changes in the cooling water flow rate and cooling water temperature when the above variable flow rate control is applied with the elapsed time on the horizontal axis and the cooling water temperature and cooling water flow rate on the vertical axis. Indicated.
[0035]
As shown, the activated cooling tower fan with the cooling water inlet temperature T _3, it accompanied it with the cooling water inlet temperature and the cooling water outlet temperature begins to decrease. The cooling water inlet temperature by operation of the cooling tower fan cooling tower fan to decrease the T ₂ is stopped, the cooling water inlet temperature and the cooling water outlet temperature it becomes accompanied has begun to rise.
[0036]
In the figure, the cooling water outlet temperature has risen beyond the T _5, the cooling water flow rate has a remains constant. This is because it uses the moving average for the past 15 minutes as chiller outlet temperature T _CO to be compared with T _5, chiller outlet temperature T _CO is because does not exceed T _5. On the other hand, before chiller outlet temperature T _CO is more than T _5, it reaches the cooling water inlet temperature gradually rises and the T _3, the cooling tower fan is started. As a result, the cooling water inlet temperature and the cooling water outlet temperature begin to decrease, and the chiller / heater outlet temperature _TCO also decreases. That is, the cooling water outlet temperature rises, while the drops, chiller outlet temperature T _CO no higher than T _5, the increase of the cooling water flow rate is not indicated. Therefore, the power cost is saved because there is no increase in the coolant flow rate.
[0037]
The fluctuation width of the cooling water outlet temperature itself caused by the start / stop of the cooling tower fan is larger than that in the prior art shown in FIG. However, the reference temperature of the chiller outlet temperature of the cooling water (control target value) is set as the temperature range having a width of between the upper control temperature T ₅ and the lower control temperature T _4, the cooling water outlet temperature past tm minutes a moving average value of the (15 minutes in this embodiment), the use as a chiller outlet temperature T _CO serving as a control input, the upper control temperature T ₅ than the cooling water outlet temperature planned during rated operation By setting it low, there is room in the cooling water system. Therefore, although the cooling water temperature fluctuates in a temperature range that does not affect the equipment, there is an effect that the amount of cooling water is stabilized at a low level and the pump power cost is reduced.
[0038]
According to this embodiment, as described above, a moving average value of the past tm minutes the cooling water outlet temperature, by a cooling water outlet temperature T _CO used in the control input, caused by start-stop of the cooling tower fan The fluctuation of the cooling water flow caused by the fluctuation of the cooling water temperature can be suppressed, the amount of cooling water can be stabilized at a low level while ensuring good stability of the operation of the absorption chiller water heater, and the pump power cost can be reduced. It became possible.
[0039]
【The invention's effect】
According to the present invention, it is possible to stabilize the flow rate of cooling water at a low level and reduce the power cost while ensuring good stability of the operation of the absorption chiller / heater.
[Brief description of the drawings]
FIG. 1 is a flowchart showing a cooling water flow rate control method according to an embodiment of the present invention.
FIG. 2 is a system diagram showing an overall configuration of an absorption chiller / heater to which the present invention is applied.
FIG. 3 is a conceptual diagram showing an example of fluctuations in cooling water temperature and cooling water flow rate in the embodiment of the present invention.
FIG. 4 is a flowchart showing a cooling water flow rate control method according to the prior art.
FIG. 5 is a conceptual diagram showing control of a cooling tower fan.
FIG. 6 is a conceptual diagram showing an example of fluctuations in cooling water temperature and cooling water flow rate in the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Absorption chiller / heater 2 High temperature regenerator 3 Fan motor 4 Cooling tower 5 Controller 6 Inverter 7 Cooling water pump 8 Temperature sensor 9 Temperature sensor 10 Temperature sensor

Claims (5)

An absorption chiller / heater comprising a procedure for circulating a cooling water to an absorption chiller / heater to cool the absorption chiller / heater according to the level of the cooling water chiller / heater inlet temperature. Control method,
The set cooling water outlet temperature flowing out from the absorption chiller time moving average detected as chiller outlet temperature of the cooling water, in a predetermined control cycle, the chiller Atsushi Ideguchi is predetermined when exceeding the temperature range increases the coolant flow rate, when the chiller Atsushi Ideguchi has not reached the temperature range reduces the cooling water flow rate, the chiller Atsushi Ideguchi is the temperature range when there within, the cooling water flow rate control method of the absorption chiller which is characterized in performing said chiller outlet temperature control to maintain the cooling water flow rate at that time. In the cooling water flow rate control method of the absorption chiller heater according to claim 1, the cooling water flow rate of the absorption chiller which is characterized in that the increase or decrease of the cooling water flow rate at a ratio predetermined for the rated maximum flow rate Control method. In the cooling water flow rate control method according to claim 1 or 2 absorption chiller heater according, when the chiller Atsushi Ideguchi has not reached the temperature range, the minimum flow quantity which the cooling water flow rate at that time preset determining whether more than a, when it exceeds the minimum flow rate, the absorption cold the cooling water flow rate reduces, the minimum flow rate below when and maintains the cooling water flow rate at that time Cooling water flow rate control method for water machine. In the cooling water flow rate control method of the absorption chiller according to any one of claims 1 to 3, control the solution temperature in the high temperature generator of the absorption chiller has been determined Me pre control target value when the difference exceeds the, instead of the chiller outlet temperature control, is the cooling water flow rate to perform the solution temperature control is set to the rated maximum flow rate, when the solution temperature is below the control target Ne以, A cooling water flow rate control method for an absorption chiller / heater, wherein the chiller / heater outlet temperature control is executed. In the cooling water flow rate control method of the absorption chiller of claim 4, wherein the solution temperature when under the control target Ne以, before performing the chiller outlet temperature control, from the previous flow rate change compared between when the elapsed time with a predetermined, when the time is over time settings, perform the chiller outlet temperature control, when the elapsed time is less than the set time, the cooling water A cooling water flow rate control method for an absorption chiller / heater, wherein the flow rate is left as it is.

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