JPS6042597A - Energy-saving operation controlling device for cooling tower - Google Patents

Abstract

PURPOSE:To save wasteful energy in the operation of cooling towers and to stabilize operation, by controlling the water temperature at an outlet to be constant, by detecting the water temperature at the inlets and the outlet of a group of cooling towers and the humidity in the atmosphere, and by controlling the number of units to be operated and the rate of air-flow for a group of cooling towers. CONSTITUTION:5 units have fans 4a-4e of constant air-flow rate, while 3 units have fans 5a- 5c of variable air-flow rate, respectively, among cooling towers which are independently operatable. The fans 4 of constant air-flow rate are ON/OFF controlled, and the number of units to be operated is controlled by a controlling signal ''a'' from a micro computer 6. The fans 5 of variable air-flow rate are constituted in such a manner that the rate of air flow can be changed by the change in angles of pitches of blades of fans or the change in the revolving number of a fan motor, for examples. A controlling signal ''b'' to control the draft rate for the cooling towers 3 of variable air-flow rate type is put out of the micro computer 6. While resistance input signals ''c'' are fed into the micro computer 6 from the detecting ends 7 and 8 of thermometers to detect the water temperature at the inlet and the outlet of cooling towers and from the detecting end 9 of a wet and dry-bulb thermometer to detect the atmosphere. The air-flow rate for the cooling units are controlled to make the water temperature at the outlet constant, and the energy consumption can be economically saved in the operation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to cooling tower equipment in which a cooling tower for supplying required cooling water to one load system is divided into a plurality of cooling tower groups each capable of operating independently.

The present invention relates to a power-saving operation control device for a cooling tower that performs microcomputer control so as to reduce the operating power cost and at the same time control the outlet water temperature to a constant level for stable operation.

Traditionally, cooling tower designs have been based on the statistically highest outdoor wet bulb temperature of 27°C.

Conventional cooling tower cooling fans are usually operated at a constant airflow rate, so if the outside air wet bulb temperature is lower than the design outside air wet bulb temperature (it is unlikely to be higher).

The actual outlet water temperature from the cooling tower is lower than the designed outlet water temperature. Therefore, in this point, operating power is wasted. Furthermore, in general, in industrial cooling towers, etc., it is desirable that the cooling water temperature be stably supplied as required water temperature, and it is desirable that the outlet water temperature be controlled to be constant regardless of any changes in conditions.

The present invention has been made with the object of eliminating waste in the operation of the cooling tower and controlling the Yamaguchi-guchi water temperature to a constant level to enable stable operation. The present invention provides cooling tower equipment that effectively achieves this objective by dividing the cooling tower for supplying the required cooling water to one load system into a plurality of cooling tower groups that can each operate independently. In the cooling tower equipment, at least one of the cooling tower groups is configured as a cooling tower with a variable air volume mechanism, and the inlet water temperature detection end to the cooling tower group, the outlet water temperature detection end from the cooling tower group, and the outside air humidity are configured. A power-saving operation control device for a cooling tower, characterized in that a microcomputer is installed to control the number of cooling towers and the air volume of the variable air volume cooling tower using a detection signal from a bulb temperature detection end as an input signal. This is what we provide.

The present invention will be specifically explained based on the drawings.

Figure 1 systematically shows the equipment arrangement of the device of the present invention, in which one load system 1 that requires cooling water is cooled by a group of cooling towers divided into a plurality of parts, each of which can operate independently. A cooling tower facility for producing water is shown. The illustrated embodiment shows an example in which the cooling tower is divided into eight independently operable cooling towers, of which five, 2a to 2e, have constant air volume fans 48 to 4e as cooling tower blowers, and three have fixed air volume fans 48 to 4e as cooling tower blowers. An example with variable air volume fans 5a to 5c is shown. The present invention is not limited to this example, and the number of nine divisions may be two or more, and the number of variable airflow cooling towers may be one or more. In the present invention, the microcomputer 6 controls the number of cooling towers and the variable air volume of the cooling tower group. Reference numerals 7, 8, and 9 indicate an inlet water temperature detection end, an outlet water temperature detection end, and an outside air wet bulb temperature detection end for obtaining control signals for this control, respectively. The inlet water temperature detection end 7 is located at a position to detect the water temperature before entering the cooling tower group, and the outlet water temperature detection end 8 is located at a position to detect the water temperature of the cooling water exiting from the cooling tower group (cooling water that is a collection of cooling water exiting from each cooling tower). will be installed. Each cooling tower 2 and 3 is provided with a cooling water pump.

The constant air volume fan 4 of each constant air volume cooling tower 2 is controlled on and off by a microcomputer 6.
The number of operating units is controlled by a control signal (non-voltage contact signal a) from. In this case, even in the cooling tower 2 where the constant air volume fan 4 is stopped, the cooling water pump continues to operate and the cooling tower operates in such a way that circulating cooling water is sprayed into the tower without forced ventilation. On the other hand, the variable air volume fan 5 of the variable air volume cooling tower 3 is configured so that the air volume can be freely changed by, for example, changing the pinch angle of the blades or by changing the rotation speed of the fan motor. In other words, 1. Although not shown in the figure, the fan blade pitch angle can be freely changed using a control panel, or a transistor inverter with a variable power supply frequency mechanism can be used to freely change the rotation speed of the fan motor. Configure.

By outputting a control signal to this control panel or transistor inverter, the ventilation air volume of the variable air volume cooling tower 3 can be automatically and remotely controlled. This control signal (a control signal of 4 to 20+nA indicated by b in FIG. 1) is output from the microcomputer 6 in the present invention. On the other hand,
The microcomputer 6 is connected to the inlet water temperature detection terminal 7. A resistance input signal C from an outlet water temperature detection terminal 8 and an outside air wet bulb temperature detection terminal 9 is introduced.

FIGS. 2 to 5 show examples of a series of calculation flows for this control, and the outline of the control procedure will be explained below.

It is as follows.

■, Design outside air wet bulb temperature...fl Design inlet water temperature...tll Design outlet water temperature..., spinal water air ratio... (, L/G) From the equation, find the enthalpy corresponding to the state using an approximate formula, Calculate the theoretical value of the cooling driving force (Ka-V/L).

② Determine the cooling driving force under the design conditions from the experimental formula (see the flowchart in Figure 2), and calculate the correction coefficient (safety factor) between the theoretical value and the planned value.

(2) All the variable air volume cooling towers 3 are sequentially activated at time intervals set by the timer Tl. In this case, in the case of two-blade angle control, the blade angle is set to O, and in the case of adopting variable power supply frequency, the starting current is started by starting at the minimum starting rotation speed.

■、The control microcomputer is ＾u to / M
Monitor the annual changeover switch.

■In the case of I, Auto (fully automatic operation) (a), Sample the outside air wet bulb temperature and the inlet water temperature 10 times each, exclude the highest and lowest values of each, and use the remaining 8 data to calculate the average outside air wet bulb temperature. Temperature, average inlet water temperature.

(b) Calculate the optimal number of 0-100% cooling towers (constant air flow cooling tower 2) to be stopped when the number is controlled so that the design outlet water temperature is reached. 0-100% at the time interval set by timer T2
The cooling tower fans 4 of the cooling towers 2 are sequentially started to reduce the starting current.

(C) Sample the outlet water temperature 10 times, exclude the highest and lowest values, and use the remaining 8 data as the average outlet water temperature.

(d) Based on the deviation between the average outlet water temperature and the target value, which is the design outlet water temperature, feedback control is performed using PI operation to adjust the blade angle or rotation speed of the fan 5 of the variable air volume cooling tower 3 so that the target outlet water temperature is achieved. control.

(e) If the two-blade angle or rotational speed is 80% or more of the maximum blade angle or maximum rotational speed, at the same time command the two-blade angle or rotational speed to be the minimum blade angle or the minimum rotational speed, The number of operating constant air volume cooling towers 2 is increased by one, and the feed bank control after C1 is performed.

(f) If one blade angle or rotation command becomes the minimum blade angle or minimum rotation speed, at the same time command the one blade angle or rotation speed to become the maximum blade angle or maximum rotation speed,
By reducing the number of operating constant air volume cooling towers 2 by one, the above (C
Performs feed hack control from 1 onwards.

(g) If the commanded blade angle or rotation speed is 80% or less, a command is sent to the 9-blade variable pinch mechanism or the transistor inverter, and the above (C) is performed at the time interval set by timer T3.
Performs subsequent feed bank control.

(h) After the time set by the timer T5 has passed, the process returns to step (2) above.

■U, Manual (manual operation) ial, 0-100% The cooling tower fans 4 of the cooling tower 2 are manually started sequentially, and the feed bank control from +01 onwards is performed.

As described above, according to 1 Motobu, controlling the number of cooling fans by controlling the on/off of cooling fans in a constant air volume cooling tower and controlling the air volume in a variable air volume cooling tower can be implemented in the most energy-saving way so that the outlet water temperature remains constant. Become. The characteristics of the above control operation are summarized as follows.

(11, Auto and Manual selector switch allows you to select between fully automatic and manual.
io.

% After commanding the operation or stop of the cooling fan 4 of the cooling tower 2, the variable air volume cooling tower 3 is feedback-controlled by the calculation of the microcomputer 6 so that the outlet water temperature is constant. And fully automatic.

The microcomputer 6 calculates the optimum number of 0--100% cooling towers 2 to be stopped, sequentially starts the number of operating units, and controls the variable air volume cooling tower 3 so that the outlet water temperature is constant.

(2) The outlet water temperature is controlled numerically by PI operation. At that time, (a) increase the number of constant air volume cooling towers 2 by one at 80% of the maximum blade angle or maximum rotation speed of the variable air volume cooling tower fan, and (b) increase the number of constant air flow cooling towers 2 by one at the minimum blade angle or minimum rotation speed. The number of operating air volume cooling towers 2 is reduced by one. At this time, in case (a), simultaneously command the minimum blade angle or minimum rotation speed, and in case of peak), command the maximum blade angle or maximum rotation speed to decrease by one unit, and the outlet water temperature will rise above the design outlet water temperature. prevent

(3) When variable air volume control is performed by controlling the rotation speed using a variable power supply frequency, the rotation speed of the propeller fan is controlled by issuing a command that jumps over the natural vibration range of 15 to 20 hz of the cooling tower body. .

[Brief explanation of the drawing]

FIG. 1 is an equipment layout system diagram of the cooling tower power saving control device of the present invention, and FIGS. 2 to 5 are a series of calculation flow diagrams of the control device of the present invention. 1. Load that requires cooling water, 2. Constant air volume cooling tower,
3. Constant air volume fan controlled on/off, 4. Variable air volume cooling tower, 5. Fan controlled with variable air volume, 6.
Microcomputer, 7... Inlet water temperature detection end, 8...
Outlet water temperature detection end, 9... Outside air wet bulb temperature detection end.

Claims (1)

[Claims] (l) In cooling tower equipment in which a cooling tower is divided into a plurality of cooling tower groups each capable of independently operating in order to supply the required cooling water to one load system. , at least one of the cooling tower groups is configured as a cooling tower with a variable air volume mechanism, and from the inlet water temperature detection end to the cooling tower group, the outlet water temperature detection end from the cooling tower group, and the outside air wet bulb temperature detection end. A power-saving operation control device for a cooling tower, characterized in that a microcomputer is installed for controlling the number of cooling towers in a group and controlling the air volume of the variable air volume cooling tower using the unloading signal as an input signal. (2) The power-saving operation control device for a cooling tower according to claim 1, wherein the variable air volume mechanism is a mechanism that changes the blade pinch angle of the cooling tower fan. (3) The power-saving operation control device for a cooling tower according to claim 1, wherein the variable air volume mechanism is a mechanism that changes the rotation speed of the electric motor of the cooling tower fan.