JPH04313695A - Temperature control method for cooling water on outlet of cooling tower - Google Patents

Abstract

PURPOSE:To make it possible to save energy, reduce noise, extend service life and carry out unmanned control with enhanced response in controlling the operating conditions of a plurality of cooling towers in response with load fluctuations. CONSTITUTION:Out of the squares of a lattice-shaped region diagram where the number of cooling tower is taken as an abscissa, while a fan mode in a plurality of stages which has as an element the rotary speed of a cooling fan is taken as an ordinate, portions under an operating status is defined as a block. A total cooling capacity is controlled by increasing and decreasing the number of blocks.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention is applicable to a plurality of refrigerators (hereinafter referred to as RF), such as a district heating and cooling heat source plant.
This is applied to plants equipped with a cooling tower (hereinafter referred to as CT) that has a cooling fan and a cooling fan. This invention relates to a water temperature control method.

0002

[Prior art] In district heating and cooling heat source plants, etc.
Annual and daily load fluctuations are large, and the time for partial load operation is long relative to the CT's total capacity, so it is important to operate appropriately in consideration of energy conservation during partial load. There are two known piping systems between RF and CT in such plants: individual systems and common systems.
It is well known that the latter common method, which allows control of the number of CTs, is superior in terms of energy savings and fine controllability of cooling water temperature.

[0003] By the way, methods often used to automatically control the cooling water temperature on the exit side of CT include (1) changing the cooling fan capacity, specifically, ■ cooling fan on/off control, ■ cooling Fan rotation speed control (pole change type,
(inverter type, etc.), ■Variable control of cooling fan on/off time, ■Control of number of operating cooling fans, (2) CT
(3) Changing the number of CTs in operation, etc. Most of the cooling water temperature control cases that have been actually adopted in the past are based on (1) above. The cooling fan capacity of (1), such as the combination with (2), or the combination of (1) (1) and (2) as disclosed in Japanese Patent Application Laid-open No. 58-37497, etc. This is a combination of the change in (2) and the change in the bypass flow rate of the cooling water on the inlet side of the CT (2). In addition, some of the above (3)
It is also known that the cooling capacity is controlled by changing the number of CTs in operation.

0004

[Problem to be solved by the invention] However, among the control cases described above, the combination of (1) and (2) is
There is no change in the number of Ts in operation, which not only lacks responsiveness to large load fluctuations, but is also unfavorable in terms of operational economy such as energy conservation. In addition, in (3), the number of units through which water flows must be determined while considering the relationship with the permissible range of cooling water flow rate, but there is no disclosure of the specific method for determining this, and the number of cooling water However, satisfactory results were not obtained in terms of both control performance and energy saving.

[0005] This invention was made in view of the above-mentioned circumstances, and it is easy to automate, save energy, reduce noise, and extend the service life of mechanical elements. An object of the present invention is to provide a method for controlling the temperature of cooling water on the outlet side of a cooling tower, which can exhibit control performance with good responsiveness.

[0006]

[Means for Solving the Problems] In order to achieve the above object, a cooling tower outlet side cooling water temperature control method according to the invention as set forth in claim 1 provides a method for controlling a cooling water temperature on the outlet side of a cooling tower according to the invention. Squares of a grid-like area diagram in which the horizontal axis is the number of operating towers and the vertical axis is the fan mode, which is set in stages in advance using the rotational speed of the cooling fan provided in each of the plurality of cooling towers. Among them, the number of parts in operation is controlled to increase or decrease in accordance with fluctuations in the temperature of cooling water on the outlet side of the cooling tower.

[0007] Furthermore, the method for controlling the temperature of cooling water at the exit side of a cooling tower according to the invention described in claim 2 is based on the total amount of cooling water and the temperature of each cooling tower when increasing or decreasing the number of square sections in the operating state. Determine the maximum and minimum number of operating cooling towers that can be used from the allowable cooling water flow range, and when the outlet side cooling water temperature rises, select one of the squares in operation that has the highest fan mode at that time. , the fan mode of the cooling fan of the cooling tower with the next startup priority after the one with the lowest startup priority is raised by one, and the cooling tower in the square with the lowest startup priority has the maximum value above. When the fan mode of the cooling fan of the cooling tower with the first startup priority is set to 1.
In addition, when the outlet side cooling water temperature decreases, the fan mode of the cooling tower cooling fan in the square with the lowest startup priority at that time is lowered by one, If the fan mode of the cooling fan in the lower grid is stopped and the number of operating cooling towers is the minimum value above, do not change the fan mode and change the bypass flow rate of cooling water on the inlet side of the cooling tower. It is characterized by being controlled so as to change.

[0008]

[Operation] According to the invention of claim 1, the horizontal axis represents the number of operating CTs whose starting priorities are set in advance, and the fan modes are set in stages in advance using the rotational speed of the cooling fan as an element. The fan mode is kept as low as possible by controlling the total cooling capacity by increasing or decreasing the number of sections (hereinafter referred to as blocks) that are in operation among the squares of a grid-like area diagram with the vertical axis being At the same time, it is possible to increase the number of CTs in operation to respond to load fluctuations, thereby increasing energy savings and reducing the number of times mechanical elements such as fans, fan motors, and power transmission devices start and stop. By reducing the number of parts, the degree of wear and tear on them can be suppressed and the life span can be extended.

In particular, according to the invention of claim 2, when increasing or decreasing the number of blocks, the maximum and minimum values of the number of operating CTs are determined from the allowable cooling water flow range, and the determined CT
By increasing or decreasing the number of blocks within the range between the maximum and minimum number of operating units, it is possible to perform control with excellent energy saving performance while exhibiting control performance with little fluctuation in water temperature.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram of a control device for carrying out the method of this invention, and in the figure, 1A, 1B,...
1N is each CT, these CT1A, 1B,...1N
are cooling fans 2A, 2B, ... 2N and their rotation speed control devices (hereinafter referred to as VR) 3A, 3B, ... 3N, respectively.
It is equipped with 4A, 4B,...4N are each RF,
These RF4A, 4B,...4N and the above CT1A, 1B,
...1N are connected to the common inlet side cooling water pipe 5 and outlet side cooling water pipe 6 so that cooling water can be circulated, and each CT1A, 1B, ...1N has an on-off valve at its inlet. 7A, 7B,...7N, cooling water pump 8A is installed at the outlet.
, 8B, . 11 is a sensor that detects the temperature of the cooling water on the outlet side.

Reference numeral 12 denotes a control device consisting of a microcomputer, and this control device 12 includes a signal S1 for setting the CT starting priority, a signal S2 for setting the CT exit temperature and allowable width (for setting the mode for the number of CT operating units), and a signal S2 for setting the CT exit temperature and allowable width. For temperature setting (
Bypass flow rate control) signal S3 and CT maximum flow rate, minimum flow rate setting signal S4 are manually input, respectively, and CT outlet side cooling water temperature signal M4 detected by the sensor 11 and each of the above RF4A, 4B,...4N ON
/OFF signal M5 is input, and as a control signal,
A CT water flow unit command signal M1, a CT fan rotation speed command signal M2, and a bypass flow command signal M3 are output, respectively.

[0012] Next, CT using the above-mentioned control device
A method of controlling the outlet side cooling water temperature will be explained. In addition,
Here, the cooling fans 2A, 2B, ...2N of CT1A, 1B, ...1N are respectively set, and the number of motor poles is 4P,
A case will be described in which a pole change type motor is used, which can be changed to three rotation modes by switching to three stages: 6P and OFF.

The CTs 1A, 1B, 1B, whose starting priorities are set in advance by inputting the signal S1 to the control device 12,
...The horizontal axis is the number of operating units of 1N, cooling fans 2A, 2B,
...The number of poles of a 2N motor is set to 3 in advance by setting 4P, 6P, and OFF.
The number of blocks inserted with diagonal lines in the squares of the area diagram shown in Figure 2 with the fan mode set in each stage as the vertical axis is used as an index, and the number of blocks is calculated based on the total amount of cooling water and the allowable amount of each CT. The maximum value (CT MAX) and minimum value (CTMIN) of the number of CTs in operation determined from the cooling water amount range.
), the outlet side cooling water temperature is controlled to be constant by increasing it in the order of the dotted line arrow in FIG. 2 and decreasing it in the opposite order. In other words, as a control program, the number of blocks = ΣCTN (i) × CTM (i), where CT
It can be expressed as N(i)=0: No water flow, 1: Water flow CTM(i)=1: Fan OFF, 1: Fan 6P, 2: Fan 4P.

FIG. 3 is an overall flowchart showing the practical content of the above-mentioned CT operation control, in which a status check program is constantly running in parallel with the main program for increasing and decreasing the number of blocks. In the figure, the number of blocks is increased or decreased according to the activation priority order described above.
If the increase or decrease is not allowed due to limitations on the number of CTs, nothing is done. Further, in FIG. 3, T is the RF cooling water temperature, Tmin is the minimum temperature for RF protection, and Ttol is the margin temperature range for control.

FIG. 4 is a flowchart showing the procedure for increasing the number of blocks (+1), and FIG. 5 is a flowchart showing the procedure for decreasing the number of blocks (-1). These block numbers are filled from the lower left corner in FIG. The position of the most advanced block is expressed by RNO and CNO.

As described above, by increasing the number of operating CTs while keeping the fan mode low, and performing control such that the fan mode is raised by one only when the number of operating CTs reaches the maximum allowable value, the predetermined level can be increased. The power consumption required to obtain this cooling capacity is reduced compared to simple fan mode control, resulting in significant energy savings.

Incidentally, an example of an experiment conducted by the present inventor regarding the relationship between fan mode change and power increase is as follows. The current first block (the one with the lowest startup priority) is the H. B. , and when increasing the number of blocks to increase the cooling capacity from here, compare the increase in cooling capacity and power consumption between increasing the number in the A direction and B direction in the same figure. As a result, the area of A in Figure 7(a) (≒
35% x 1 unit), and when increasing 6P → 4P, the area of B in Figure 7(a) becomes (≒20% x 1 unit), and the fan power is 6
If the power of P is Po (KW), the power of 4P is Po
×(6/4)3 = 3.38Po(KW), Figure 7
The results shown in (b) were obtained. As is clear from this result, the increase in the number of blocks in the B direction from 6P to 4P increases the cooling capacity the same or less than the increase in the number of blocks in the A direction from OFF to 6P, and the power consumption It can be seen that the increase in is large.

In the above embodiment, a control method for optimal operation of a CT equipped with a pole-change type cooling fan has been explained. , which has similar effects, and the inverter type will be described in detail below.

In the case of the inverter type, as in the case of the pole change type, the number of operating CTs is gradually increased while the cooling fan is initially stopped. Set number of CTs and R
After completion of water flow up to CT MAX determined from the required cooling water amount of F, the operation of setting the fan rotation mode and the number of operating units will be described below. Generally, the fan air volume F and the cooling amount C have a relationship as shown in FIG. 8, and the amount of increase in the cooling amount from the water flow state is proportional to the fan air volume F, as shown by G in the figure. On the other hand, ideally, the relationship between the fan power P and the fan air volume F is expressed as P=aF2, as shown by the solid line in FIG.
is proportional to the square of the fan airflow F, but depending on inverter efficiency etc., the actual performance curve is expressed by P = aF2 + b, as shown by the dotted line in Figure 9. ) is approximated to the squared curvature. Therefore,
The relationship between the cooling amount C and the fan power P is as shown in FIG.

The following is an explanation for a single CT unit, but the relationship between the total power ΣP and the total cooling amplification width ΣG when n CTs are operating at the same rotation speed is as shown in FIG. become. In the figure, the solid line is for an ideal fan, and the dotted line is for an actual fan. Therefore, given the required cooling amount ΣG0, in the case of an ideal fan, n
The larger ΣP becomes, but in the case of reality fans,
Optimal n that minimizes ΣP depending on the region of ΣG0
is decided. In other words, n=1 when ΣG0 is 0 to ΣG1
, ΣG1 to ΣG2, n=2, ΣG2 to ΣG3, n=3, and ΣG4 to n=4. Furthermore, here,
The values of the required cooling amounts ΣG1, ΣG2, . . . are determined according to the performance curve of the inverter, such as the cut edge b described above.

As a result of the above, a diagram corresponding to FIG. 2, which is an optimal operation control diagram for the inverter type and pole change type, is as shown in FIG. 12, and the rectangles S1, S2,
The area of S3... corresponds to ΣG1, ΣG2, ΣG3,... in FIG. 11, and once up to CT MAX has been activated, it is better to increase the rotation modes of all CTs at the same time.

Although the above explanation uses an inverter type as an example, the same effect can be obtained even if it is applied to a CT having a cooling fan with a continuously variable air volume.

[0023]

[Effects of the Invention] As described above, according to the present invention, since the operating status of multiple CTs is managed using an index called the number of blocks, it is easy to program the control contents, and automation of complex CT operations is possible. , it is possible to achieve unmanned operation. Moreover, it is possible to respond to load fluctuations by increasing or decreasing the number of CTs operated while keeping the fan mode as low as possible.
By minimizing the power consumed by the fan, it is possible to achieve significant energy savings and reduce noise. Furthermore, since the number of times the cooling fan is turned on and off or the number of revolutions is changed can be reduced, there is less wear and tear on mechanical elements such as the fan, motor, power transmission device, etc., and the life of the entire device can be extended.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a control device for implementing the method of the present invention.

[Fig. 2] Pole change type C which is an embodiment of this invention
It is an operation control diagram in case of T.

FIG. 3 is an overall flowchart showing the details of the operation control in FIG. 2;

FIG. 4 is a flowchart showing a procedure for increasing the number of blocks.

FIG. 5 is a flowchart showing a procedure for reducing the number of blocks.

FIG. 6 is a diagram illustrating states of blocks in the flowcharts shown in FIGS. 4 and 5;

FIG. 7 is an explanatory diagram of the direction in which blocks increase in an experimental example and the results in different directions of increase.

FIG. 8 is a characteristic diagram showing the relationship between fan air volume and cooling amount by a single cooling fan in the case of an inverter type.

FIG. 9 is a characteristic diagram showing the relationship between fan power and fan air volume.

FIG. 10 is a characteristic diagram showing the relationship between fan power and cooling amount in the same as above.

FIG. 11 is a characteristic diagram illustrating the relationship between the total fan power and the total cooling amplification width during operation of a plurality of inverter-type CTs.

FIG. 12 is an operation control diagram for an inverter-type CT that is another embodiment of the present invention.

[Explanation of symbols]

1A, 1B,...1N CT 2A, 2B,...2N Cooling fan 3A, 3B,...3N VR 9 Bypass pipe 10 Bypass flow rate adjustment valve 12 Control device

Claims (2)

[Claims] [Claim 1] The horizontal axis represents the number of operating cooling towers for which startup priorities are set in advance, and the number of rotations of cooling fans provided in each of the cooling towers is set in advance in stages. Among the squares of a grid-like area map whose vertical axis is the fan mode, the number of parts in an operating state is controlled to increase or decrease in accordance with fluctuations in the cooling water temperature on the outlet side of the cooling tower. A method for controlling the temperature of cooling water on the outlet side of a cooling tower. [Claim 2] In controlling the increase/decrease of the number of square sections in operation, the maximum and minimum values of the number of operating cooling towers that can be used are determined from the total amount of cooling water and the allowable cooling water amount range of each cooling tower. However, when the temperature of the cooling water on the outlet side rises, the cooling fan of the cooling tower with the next startup priority after the one with the lowest startup priority among the squares in operation with the highest fan mode at that time is activated. Raise the fan mode by one, and if the cooling tower in the square with the lowest startup priority reaches the maximum value above, increase the fan mode of the cooling fan of the cooling tower with the first startup priority by one. Also, when the outlet side cooling water temperature decreases, the fan mode of the cooling tower cooling fan in the square with the lowest startup priority at that time is lowered by one level, and the fan mode of the cooling tower with the lowest startup priority is lowered by one. The fan mode of the cooling fan in the square part is stopped,
In addition, when the number of operating cooling towers is the above-mentioned minimum value, the fan mode is not changed and the bypass flow rate of the cooling water on the inlet side of the cooling tower is controlled to be changed. A method for controlling the temperature of cooling water on the outlet side of a cooling tower.