JP2011137599A - Water quality management method for cooling tower, and the cooling tower using the water quality management method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain water quality management that stably maintains the concentration of impurities in cooling water, in a cooling tower to a tolerance or lower by a simple and easy-to-use facility. <P>SOLUTION: In maintaining the concentration of impurities to the tolerance or lower by controlling blown down amount by opening/closing an automatic water discharge valve 22 provided in a water discharge pipe 21 of the cooling tower 1, an inlet/outlet temperature difference of cooling water of a water cooler/heater 11, when the cooling water is circulated at a set flow rate at set load of the water cooler/heater, is represented as ΔT<SP>*</SP>. Reference opening time T2<SP>*</SP>for the automatic water discharge valve, necessary for discharging the blown down amount according to the evaporation amount of the cooling water, at this time in a control cycle T1, is set. Inlet/outlet temperature difference ΔT of the cooling water circulated and supplied to the water cooler/heater with respect to each control cycle is calculated. Opening time T2 of the automatic water discharge valve 22 is calculated by multiplying T2<SP>*</SP>by a ratio L of ΔT with respect to ΔT<SP>*</SP>, and according to the calculated opening time T2, the opening time of the automatic water discharge valve 22 is controlled in a next control cycle, so as to control the amount blown down. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a water quality management method for a cooling tower and a cooling tower using the water quality management method, and more specifically to a water quality management technique for an open type cooling tower such as a counter flow type or a cross flow type.

  Generally, low-temperature cooling water is supplied to a cooling load that requires cooling, such as a cooling device or a cooling / heating machine, and high-temperature cooling water returning from the cooling load is sprayed in the atmosphere to evaporate some of the cooling water. An open type cooling tower is widely used in which low-temperature cooling water is regenerated by the latent heat of vaporization and circulated again to the cooling load.

  An open type cooling tower receives, for example, a casing having an opening at the top, a water spray nozzle provided at the top of the casing, and cooling water sprayed from the water nozzle provided at the bottom of the casing. A water tank to be stored, a blower that is provided at the top opening of the casing and circulates air in the casing, a cooling water pump that sucks the cooling water in the water tank and supplies it to the cooling load and circulates it to the watering nozzle, A water level control means for supplying makeup water so as to keep the water level within a set range, and an overflow pipe having an opening position set at a water level higher than the upper limit of the water level set range.

  In such circulating cooling water of the open type cooling tower, a part of the cooling water evaporates for heat dissipation, so that impurities contained in the cooling water are concentrated. If the concentrated impurities adhere to the heat transfer tube or the like under a cold load as scale, the heat transfer performance may deteriorate and corrosion of the heat transfer tube or the like may occur. Therefore, in general, a part of the circulating cooling water is periodically drained (blow down) and replenished with new cooling water to dilute the concentration ratio of impurities and keep it below the control value. Yes. However, if the amount of blowdown that is drained regularly is set to a certain amount, it will be uneconomical because cooling water will be blown down more than necessary even though the cooling load is small and the amount of evaporation is small depending on the season and time. is there.

  Therefore, Patent Document 1 proposes that the conductivity of cooling water is measured to determine the concentration of impurities in the cooling water, and the cooling water is blown down so that the concentration ratio of impurities does not exceed the control value. . However, according to the method in which the blowdown amount is controlled by the conductivity of the cooling water, as described in Patent Document 2, an error occurs when the scale adheres to the conductivity meter. Therefore, it is necessary to periodically clean the sensor unit of the conductivity meter (for example, about once every three months) to keep the impurity concentration stably below the allowable value, and the maintenance of the sensor unit is troublesome. Take it. In addition, expensive conductivity meters need to be replaced periodically.

  Therefore, in Patent Document 2, the temperature difference between the inlet and outlet of the cooling water circulated and supplied to the cooling load and the circulation flow rate of the cooling water are measured. The amount of cooling water evaporated is calculated by dividing by the latent heat of evaporation. Based on the determined evaporation amount, the blowdown amount necessary to keep the impurity concentration ratio below the control value is obtained and detected by a flow rate detector provided in a drain pipe connected to the water tank of the cooling tower. It has been proposed to control a flow control valve provided in the drain pipe so that the flow rate to be matched with the blowdown amount. According to this, since the blowdown amount can be automatically controlled in accordance with the evaporation amount correlated with the cooling load, the cooling water is not wasted and the operating cost can be reduced.

JP 47-24392 A JP-A-63-243695

  By the way, according to the water quality management method for the cooling tower described in Patent Document 2, problems such as periodic cleaning and replacement of the sensor unit for avoiding measurement errors caused by the scale adhering to the conductivity meter are solved. it can. Moreover, since the blowdown amount is controlled according to the evaporation amount of the cooling water, the cooling water is not blown down more than necessary.

  However, in Patent Document 2, since the flow rate of the circulating cooling water is detected in order to obtain the heat dissipation amount of the circulating cooling water proportional to the evaporation amount, the flow rate control valve is set according to the evaporation amount of the circulating cooling water. Since the blow-down amount is controlled by this, a flow rate detector and a flow rate control valve for the circulating cooling water must be provided, which not only increases the equipment cost, but also requires maintenance costs.

  The problem to be solved by the present invention is to realize water quality management that stably keeps the impurity concentration in the cooling water of the cooling tower below an allowable value with simple and simple equipment.

  In order to solve the above-mentioned problem, a first aspect of the present invention is to spray high-temperature cooling water returned from a cooling load in the air and store it in a water tank, and cool the cooling water by the evaporation latent heat of water. Then, in the water quality management method of the cooling tower that circulates again to the cooling load at a set flow rate, the drain valve provided in the drain pipe connected to the water tank is controlled to open and close to control the blowdown amount, It is assumed that the impurity concentration in the cooling water is maintained below the allowable value.

  In particular, the control of the blowdown amount is obtained as a reference inlet / outlet temperature difference as a reference inlet / outlet temperature difference when the cooling water is circulated at the set flow rate when the cooling load is set. The drainage valve required to discharge the blowdown amount obtained in order to maintain the impurity concentration in the cooling water below the allowable value by obtaining the evaporation amount of the cooling water at the inlet / outlet temperature difference in the set control cycle A reference opening time of the cooling water is set, and an inlet / outlet temperature difference of the cooling water circulated and supplied to the cooling load is obtained for each control cycle, and a ratio of the cooling water inlet / outlet temperature difference to the reference inlet / outlet temperature difference is determined as the reference The opening time of the drain valve is obtained by multiplying the opening time, and the opening time of the drain valve is controlled in the next control cycle according to the obtained opening time.

Here, the principle of the present invention will be described. The evaporation amount of the cooling water in the cooling tower is proportional to the heat dissipation amount of the cooling water. As shown in the following equation (1), the heat dissipation amount Q is the difference in the inlet / outlet temperature ΔT (= the outlet temperature To (cooling tower inlet temperature) of the cooling load and the inlet temperature Ti (cooling tower outlet temperature) of the cooling load. To-Ti) is a value obtained by dividing the product of the cooling water circulation flow rate V by the latent heat of vapor evaporation Qs.
Q = ΔT · V / Qs (1)
Here, there are many cooling towers that circulate at a constant set flow rate V ^* (for example, the rated flow rate of the cooling water pump or the flow rate at the rated load of the cooling load) without changing the circulating flow rate V. In this case, since the circulation flow rate V ^* is a constant and the latent heat of vaporization Qs is originally a constant, the heat release amount Q is proportional only to the coolant inlet / outlet temperature difference ΔT.

  Therefore, in the case of a cooling tower that circulates cooling water at a set flow rate, the present invention detects the cooling water inlet / outlet temperature difference ΔT and controls the cooling water blow-down amount in proportion to the inlet / outlet temperature difference ΔT. For example, the cooling water flow rate detector is not required. However, in order to control the amount of blowdown, a flow control valve is generally required, so that equipment costs and maintenance costs are required.

Therefore, in view of the fact that the cooling load generally does not fluctuate abruptly and does not fluctuate for a short time, the blowdown amount control response speed is not required to be so high. The down amount is controlled by controlling the opening time of the drain valve. That is, since the circulating flow rate of the cooling water is maintained at the set flow rate, the heat dissipation amount Q correlated with the evaporation amount Vb is proportional only to the cooling water inlet / outlet temperature difference ΔT, and the necessary blowdown amount Vb is also equal to the inlet / outlet temperature difference ΔT. Proportional only to Therefore, the cooling water is circulated at the set flow rate (for example, the rated flow rate of the cooling water pump) at the time of the set load (for example, the rated load) of the cooling load, and at a time corresponding to an arbitrary control cycle T1 (for example, 30 minutes). The temperature difference of the cooling water inlet / outlet (average of time if necessary) is defined as the reference inlet / outlet temperature difference ΔT ^*, and the amount of cooling water evaporated at this reference inlet / outlet temperature difference ΔT ^* is determined. To obtain a reference blowdown amount Vb ^* that keeps the value below the allowable value. Further, the drain valve opening time T2 required for discharging the reference blowdown amount Vb ^* in the set control cycle T1 is set as the reference opening time T2 ^* .

In this manner, the reference inlet / outlet temperature difference ΔT ^* and the reference opening time T2 ^* are set, and the inlet / outlet temperature difference ΔT of the cooling water circulated and supplied to the cooling load is obtained every arbitrary control cycle T1 to obtain the reference inlet / outlet temperature. by multiplying the difference [Delta] T ^* ratio of inlet and outlet temperature difference [Delta] T for the [Delta] T / [Delta] T ^* based open time T2 ^* Request opening time T2 of the drain valve. If the drain valve open time T2 is controlled in the next control cycle in accordance with the obtained open time T2, the impurity concentration in the cooling water can be maintained below the allowable value. Thereby, the water quality management of a cooling tower is realizable with simple and simple equipment, without using the flow volume detector and flow control valve of a cooling water. In this case, the control cycle for controlling the drain valve opening time T2 based on the evaporation amount is delayed by one control cycle with respect to the control cycle for obtaining the inlet / outlet temperature difference ΔT corresponding to the evaporation amount. In the case of continuous operation, there is no problem.

  According to a second aspect of the present invention, an inlet / outlet temperature difference of the cooling water circulated and supplied to the cooling load is obtained for each sampling period, and the inlet / outlet temperature difference is integrated during an integration time corresponding to the control period. The integrated value of the inlet / outlet temperature difference obtained by integrating the inlet / outlet temperature difference when the cooling water is circulated at the set flow rate at the reference load of the cooling load during the integrated time is used as a reference. Obtain the ratio of the integrated value of the temperature difference, multiply the reference opening time of the drain valve determined in correspondence with the reference integrated value to determine the opening time of the drain valve by multiplying the ratio, according to the opening time The opening time of the drain valve in the next control cycle is controlled.

  In the first and second aspects of the present invention, the control period or accumulated time is set to be equal to or longer than the reference open time. Moreover, the said drainage pipe can be set as the structure connected to the drain pan installed above the water surface of the said water tank which receives some cooling water sprayed in the said air instead of the said water tank.

  A cooling tower for carrying out the water quality management method according to the first aspect of the present invention includes a casing having an opening at the top, a water spray nozzle provided in the upper part of the casing, and cooling water sprayed from the water spray nozzle. A water tank provided at the bottom of the casing to be received and stored, a blower provided at the top opening of the casing that circulates air in the casing, and sucking the cooling water in the water tank and supplying it to the cooling load to the watering nozzle A cooling water pump to be circulated, a water level control means for supplying makeup water so as to keep the water level of the water tank within a set range, an overflow pipe whose opening position is set at a water level higher than the upper limit of the water level setting range, and the cooling A cooling tower comprising water quality management means for controlling the blow-down amount of water to maintain the impurity concentration in the cooling water below an allowable value is intended.

  In such a cooling tower, the water quality management means includes a drain pipe communicating with the water tank, an electric or electromagnetic automatic drain valve provided in the drain pipe, and a cooling water circulated and supplied to the cooling load. Control means for controlling the blow-down amount of the cooling water by controlling the opening and closing of the automatic drain valve based on the inlet / outlet temperature difference, and the control means at the set flow rate when the cooling load is set. The cooling water inlet / outlet temperature difference of the cooling load when the cooling water is circulated is defined as a reference inlet / outlet temperature difference, and the evaporation amount of the cooling water at the reference inlet / outlet temperature difference is obtained, and the impurity concentration in the cooling water is allowed. A reference blowdown amount to be maintained below is obtained, a reference opening time of the automatic drain valve necessary for discharging the reference blowdown amount in a set control cycle is set, and the cooling / heating is set for each control cycle. The temperature difference between the inlet and outlet of the cooling water circulated and supplied to the load is obtained, and the opening time of the automatic drain valve is obtained by multiplying the reference opening time by the ratio of the temperature difference between the inlet and outlet of the cooling water to the reference inlet and outlet temperature difference. The opening time of the automatic drain valve is controlled in the next control cycle according to the opening time.

  Further, the water quality management means of the cooling tower for carrying out the water quality management method of the second aspect of the present invention includes a drain pipe communicating with the water tank, and an electric or electromagnetic automatic drain valve provided in the drain pipe And a control means for controlling the blow-down amount of the cooling water by controlling the opening and closing of the automatic drain valve based on the temperature difference between the inlet and outlet of the cooling water circulated and supplied to the cooling load, the control means, The inlet / outlet temperature difference of the cooling water circulated and supplied to the cooling load is obtained for each sampling period, and the inlet / outlet temperature difference is integrated for an integration time corresponding to the control period to obtain an integrated value of the inlet / outlet temperature difference. The ratio of the integrated value of the inlet / outlet temperature difference is obtained on the basis of the integrated value of the inlet / outlet temperature difference obtained by integrating the inlet / outlet temperature difference when the cooling water is circulated at the set flow rate at the reference load. , The reference product The open time of the automatic drain valve is obtained by multiplying the reference open time of the open time of the automatic drain valve corresponding to the value by the ratio, and the open time of the automatic drain valve in the next control cycle according to the open time. It is characterized by controlling time.

  Moreover, the said drainage pipe of the cooling tower which implements the water quality management method of the 1st and 2nd aspect of this invention is replaced with the said water tank, The said water tank which receives a part of cooling water sprayed in the said air It can be set as the structure connected to the drain pan installed above the water surface.

  ADVANTAGE OF THE INVENTION According to this invention, the water quality management which hold | maintains stably the impurity density | concentration in the cooling water of a cooling tower below to an allowable value is realizable with a simple and simple installation.

1 is a configuration diagram of a cooling water system including a cooling tower and a cooling load according to an embodiment to which a water quality management method of the present invention is applied. It is a flowchart of the water quality management procedure of one embodiment of this invention. It is a diagram explaining how to obtain the opening time of the automatic drain valve corresponding to the blowdown amount. It is a flowchart of the water quality management procedure of other embodiment of this invention.

Hereinafter, the present invention will be described based on embodiments.
(Embodiment 1)
FIG. 1 shows a cooling water system configuration diagram including a cooling tower and a cooling load of one embodiment to which the water quality management method of the present invention is applied, and FIG. 2 shows a flow chart of a water quality management procedure of this embodiment.

  As shown in FIG. 1, the cooling tower 1 includes a cylindrical casing 2, an air inlet 3 is formed on the lower side surface of the casing 2, and a cooling water tank 4 is provided at the bottom. In addition, the filler 5 is accommodated in the casing 2 above the position of the air inlet 3, and the cooling water sprinkling nozzle 6 is disposed above the filler 5. An opening 7 is provided at the top of the casing 2, and a blower 8 is provided in the opening 7. The suction port of the cooling water pump 9 communicates with the vicinity of the bottom of the water tank 4, and the discharge port of the cooling water pump 9 is a heat exchanger that is a cooling / heating load provided in the chiller / heater 11 via the cooling water supply pipe 10. Is connected to one end of the heat transfer coil 12. The other end of the heat transfer coil 12 is connected to the watering nozzle 6 of the cooling tower 1 through a cooling water return pipe 13.

  A water supply pipe 14 is inserted into the water tank 4, and a ball tap type automatic valve 15 as a water level control means is provided at the tip of the water tank 4. As is well known, the ball tap type automatic valve 15 opens the valve to supply water when the water level of the water tank 4 falls below the lower limit value, and closes the valve to stop water supply when the water level reaches the upper limit value. The water level is kept within the set range. The water supply pipe 14 is supplied with makeup water 16 such as tap water. Further, the water tank 4 is provided with an overflow pipe 19 opened in a drain groove 17 (not shown) so that the cooling water does not overflow from the upper end of the water tank 4 to the surroundings. The upper end opening of the overflow pipe 19 is set at a position higher than the upper limit of the water level setting range of the water tank 4.

  A drain pan 20 is installed above the water surface of the water tank 4, and a drain pipe 21 for blowdown is connected to the bottom of the drain pan 20. An automatic drain valve 22 comprising an electric valve or an electromagnetic valve is interposed in the drain pipe 21, and the tip of the drain pipe 21 joins the overflow pipe 19 and is opened in a drain groove 17 (not shown). The drain pan 20 is a dish-like container having an open upper surface, and receives a part of the cooling water sprayed from the watering nozzle 6 and flowing down the filler 5, and can be stored as blow-down cooling water. Yes. However, in the present invention, the drain pan 21 can be provided in communication with the bottom of the water tank 4 without providing the drain pan 20.

  On the other hand, a temperature sensor 23 for detecting a cooling water inlet temperature to the chiller / heater 11 is provided at a connection portion between the cooling water supply pipe 10 and the heat transfer coil 12, and the cooling water return pipe 13 and the heat transfer coil 12 are provided. The temperature sensor 24 which detects the cooling water exit temperature from the cold / hot water machine 11 is provided in the connection part. The chiller / heater 11 is provided with a control panel 25 that controls opening and closing of the cooling water pump 9 and the automatic drain valve 22. Detection signals from the temperature sensors 23 and 24 are input to the control panel 25. Here, the control panel 25 controls the chiller / heater 11, but in this embodiment, a water quality management means for managing the water quality of the cooling water based on the detection signals of the temperature sensors 23 and 24 is incorporated. ing.

Next, the configuration of the water quality management means in the control panel 25 of the cooling tower 1 of the present embodiment configured as described above will be described together with the operation with reference to the flowchart of FIG. First, how to determine the blowdown amount for maintaining the impurity concentration in the cooling water below the allowable value will be described. The meanings of symbols in the formulas described below are as follows.
Cooling load inlet / outlet temperature difference: ΔT
Heat dissipation: Q
Evaporation amount: Va
Makeup water volume: Vq
Blowdown amount (drainage): Vb
Impurity concentration in makeup water: c
Permissible concentration ratio of impurities: F
Evaporation latent heat of water: Qs (for example, 600 kcal / L)
Here, the amount of impurities entering the cooling water by the makeup water 16 is c · Vq, and the amount of impurities coming out of the cooling water by blowdown is c · F · Vb. Since the condition that the amount of impurities enters and exits is c · Vq = c · F · Vb, the following equation (2) is established.
Vb = Vq / F (2)
In addition, the following equation (3) is established from the balance of water supply / exit.
Vq = Va + Vb (3)
If the heat radiation amount Q in the cooling tower 1 is entirely due to the water evaporation latent heat Qs, the evaporation amount Va is expressed by the following equation (4).
Va = Q / Qs (4)
Here, from the equations (2) to (4), the blowdown amount Vb necessary to maintain the allowable concentration ratio F of impurities is obtained by the following equation (5).
Vb = Q / ((F-1) Qs) (5)
Next, if the circulating flow rate of the cooling water is maintained at the set flow rate V ^* , the heat release amount Q can be expressed by the following equation (6).
Q = ΔT · V ^* / Qs (6)
Therefore, Formula (5) can be expressed by the following Formula (7).
Vb = ΔT · V ^* / ((F−1) Qs ² ) (7)
In Expression (7), since constants other than ΔT are constants, when proportional constant K is used, it can be expressed by Expression (8).
Vb = K · ΔT (8)
That is, the blowdown amount Vb may be controlled in proportion to the cooling water inlet / outlet temperature difference ΔT, so that it is understood that the cooling water flow rate detector is unnecessary.

  Here, in order to control the blowdown amount Vb, a flow control valve is generally required, which is not preferable. Therefore, in the present embodiment, the cooling / heating load of the chiller / heater 11 generally does not fluctuate rapidly, and since there is little fluctuation in a short time, control of the blowdown amount does not require a high response speed. In view of this, the blowdown amount Vb is controlled by controlling the opening time of the automatic drain valve 22 in a constant control cycle.

  That is, when the fluctuation of the cooling water inlet / outlet temperature difference ΔT is small in an arbitrary control cycle (for example, 30 minutes), the inlet / outlet temperature of the cooling water circulated and supplied to the cooling load of the chilled water heater 11 every control cycle T1. By obtaining the difference ΔT, the necessary blowdown amount (drainage amount) Vb can be obtained. Here, when the inlet / outlet temperature difference ΔT fluctuates, for example, it is preferable to use the time average value of the inlet / outlet temperature difference ΔT in the control cycle.

Next, features of the present embodiment will be described. The cooling water inlet / outlet temperature difference ΔT when the cooling water is circulated at the set flow rate V ^* at the set load of the chiller / heater 11 is defined as a reference inlet / outlet temperature difference ΔT ^* . For example, the rated load of the cooling / heating load of the chiller / heater 11 can be adopted as the setting load, but the present invention is not limited to this, and an arbitrary load within the rated load can be set. The reference inlet / outlet temperature difference ΔT ^* can be obtained in advance in the design stage or trial operation. The cooling water evaporation amount Va at the reference inlet / outlet temperature difference ΔT ^* is obtained by calculation, and the reference blowdown amount Vb ^* for maintaining the impurity concentration in the cooling water below the allowable value is obtained by the previous equation (7).

Next, the valve opening time required to open the automatic drain valve 22 and discharge the reference blowdown amount Vb ^* is set as the reference opening time T2 ^* . Since the drain pressure at this time is the water surface height (hydrostatic head) in the drain pan 20, at least the combined volume of the drain pan 20 and the drain pipe 21 is equal to or greater than the reference blowdown amount Vb ^* , preferably the reference blowdown amount Vb. It is preferable to match ^* . In addition, when adjustment of the combined volume of the drain pan 20 and the drain pipe 21 is necessary, it is preferable to provide a lid that can adjust the opening area of the drain pan 20 and adjust the amount of cooling water that falls. In addition, when the drain pan 21 is connected to the bottom of the water tank 4 without providing the drain pan 20, the drain pressure is the water surface height (hydrostatic head) of the water tank 4, but the water surface is kept within the set range. The standard opening time T2 ^* is set with a margin in consideration of some errors.

Thus, the reference inlet / outlet temperature difference ΔT ^* at the set flow rate V ^* and the reference opening time T2 ^* of the automatic drain valve 22 required to discharge the reference blowdown amount Vb ^* in that case are stored in, for example, a memory. To set. Thus, if the inlet / outlet temperature difference ΔT in an arbitrary control cycle T1 is obtained, the opening time T2 of the automatic drain valve 22 required to discharge the blowdown amount at that time can be obtained by the following equation (9).
T2 = T2 ^* · ΔT / ΔT ^* (9)
An example of the relationship of Formula (9) is shown in FIG. And the required blow-down amount Vb can be discharged | emitted by carrying out open control of the automatic drain valve 22 according to the open time T2 calculated | required in arbitrary control periods T1. As a result, according to the present embodiment, a flow control valve for controlling the blowdown amount is not necessary.

  Here, with reference to the flowchart of FIG. 2, the blowdown amount control according to the present embodiment will be described in detail. In FIG. 2, when the current control cycle (cycle T1) is started, the calculated value of the inlet / outlet temperature difference ΔT obtained in the previous control cycle is reset as an initialization process, and the timer of the control cycle T1 is reset (S1). . Next, it is determined whether or not the cooling water pump 9 is in operation (S2). If it is stopped, sampling of ΔT is stopped (S11), and the process proceeds to S6. On the other hand, if the cooling water pump 9 is in operation, the inlet / outlet temperature difference ΔT (= To−Ti) is sampled every sampling period T0 (<T1). Next, it is determined whether or not the opening time T2 of the automatic drain valve 22 set in the previous control cycle has expired (S4). If it has expired, the automatic drain valve 22 is closed to complete the blowdown (S12). If it has not expired, the automatic drain valve 22 is kept open (S5). Then, it is determined whether or not the current control cycle T1 has expired (S6). If it has not expired, the process returns to S3 and the process is repeated. If the current control cycle T1 has expired, sampling of ΔT is terminated, and the calculated value of the inlet / outlet temperature difference ΔT in the current control cycle is obtained (S7). For the calculation of ΔT, if the variation of ΔT sampled a plurality of times in the current control cycle is within an allowable range, a representative sampling value of ΔT is adopted. If the fluctuation exceeds the allowable range, the average value of ΔT sampled a plurality of times can be obtained and used as the calculated value of ΔT.

Next, a reference water inlet / outlet temperature difference ΔT ^* stored in a memory (not shown ⁾ is read, and a ratio L (%) of the inlet / outlet temperature difference ΔT obtained in the current control cycle T1 with respect to ΔT ^* is obtained ( S8). Then, reading the reference opening time T2 ^* of the automatic drain valve 22 that is stored in a memory or the like, automatic drainage necessary for discharging the blowdown rate Vb for the current control cycle is multiplied by L on the reference open time T2 ^* An opening time T2 of the valve 22 is obtained (S9). Next, the opening time T2 is set in the automatic drain valve 22, the automatic drain valve 22 is opened, the process returns to S1, and the process of the next control cycle is continuously executed.

  As described above, according to the present embodiment, the water quality management for stably maintaining the impurity concentration in the cooling water of the cooling tower below the allowable value is performed using the flow meter for the cooling water and the flow control valve for the blow-down. It can be realized with simple and simple equipment.

(Embodiment 2)
FIG. 4 shows a flowchart of a water quality management procedure of another embodiment to which the water quality management method of the present invention is applied. Since the present embodiment is different from the first embodiment in the configuration of the water quality management means of the control panel 25, the system configuration of the cooling tower and the hot and cold water machine will be described with reference to FIG.

  As shown in FIG. 4, the water quality management procedure of the present embodiment is different from the water quality management procedure of the first embodiment in the case where the fluctuation of the inlet / outlet temperature difference ΔT in the control cycle T1 is small in the first embodiment. Although shown as an example, the present embodiment can also be applied when the fluctuation of the inlet / outlet temperature difference ΔT within the control cycle T1 is relatively large. That is, in FIG. 4, the integrated value of ΔT and the control cycle T1 (integrated time) are initialized (S21). Next, if the cooling water pump 9 is in operation (S22), ΔT is integrated every sampling period T0 (<T2) (S23). Next, it is determined whether or not the open time T2 of the automatic drain valve 22 set in the previous control cycle T1 has expired (S24). If it has expired, the automatic drain valve 22 is closed and the blow-down is finished (S32). If it is determined in S24 that the opening time T2 has not expired, the automatic drain valve 22 is kept open, and the sampling period T0 is subtracted from the opening time T2 to obtain a new T2 (S25). Next, it is determined whether or not the control cycle T1 has expired (S26). If it has not expired, the process returns to S23 and is repeated.

If it is determined in S26 that the control cycle T1 has expired, the integration of ΔT is terminated (S27). Next, a reference inlet and outlet temperature difference ΔT of the cooling water integrated during control period T1 reads the accumulated value ShigumaderutaT ^* stored in the memory or the like, inlet and outlet temperature difference obtained in the current control period T1 for the integrated value ShigumaderutaT ^* A ratio L (%) of the integrated value ΣΔT of ΔT is obtained (S28). Then, reading the reference opening time T2 ^* of the automatic drain valve 22 that is stored in a memory or the like, automatic drainage necessary for discharging the blowdown rate Vb for the current control cycle is multiplied by L on the reference open time T2 ^* An opening time T2 of the valve 22 is obtained (S29). Next, an open time T2 is set in the automatic drain valve 22, the automatic drain valve 22 is opened, and the process returns to S21 to continue the next control cycle.

  As described above, according to the present embodiment, the water quality management for stably maintaining the impurity concentration in the cooling water of the cooling tower below the allowable value is performed using the flow meter for the cooling water and the flow control valve for the blow-down. It can be realized with simple and simple equipment. In particular, the present embodiment controls the blow-down amount based on the integrated value ΣΔT of the inlet / outlet temperature difference ΔT, so that the cooling / heating load in which the inlet / outlet temperature difference ΔT varies relatively compared to the first embodiment. Even in this case, the impurity concentration in the cooling water can be stably maintained with high accuracy below the allowable value.

DESCRIPTION OF SYMBOLS 1 Cooling tower 2 Casing 4 Water tank 6 Sprinkling nozzle 8 Blower 9 Cooling water pump 11 Cold / hot water machine 12 Heat transfer coil 15 Ball tap type automatic valve 19 Overflow piping 20 Drain pan 21 Drain pipe 22 Automatic drain valve 23 Temperature sensor 24 Temperature sensor 25 Control panel

Claims (4)

Water quality management method for a cooling tower in which high-temperature cooling water returned from a cooling load is dispersed in the air, the cooling water is cooled by the latent heat of water evaporation, stored in a water tank, and circulated again to the cooling load at a set flow rate In
By controlling the blowdown amount by opening and closing a drain valve provided in a drain pipe communicated with the water tank, the impurity concentration in the cooling water is maintained below an allowable value,
The control of the blowdown amount is obtained by calculating a reference inlet / outlet temperature difference as a reference inlet / outlet temperature difference when cooling water is circulated at the set flow rate when the cooling load is set. The drain valve standard required for discharging the amount of cooling water at the time of the difference and discharging the blow-down amount determined to maintain the impurity concentration in the cooling water below the allowable value in the set control cycle An opening time is set, an inlet / outlet temperature difference of the cooling water circulated and supplied to the cooling load for each control cycle is obtained, and a ratio of the cooling water inlet / outlet temperature difference to the reference inlet / outlet temperature difference is determined as the reference opening time. To determine the opening time of the drain valve, and control the opening time of the drain valve in the next control cycle according to the determined opening time. Water quality management method for a cooling tower in which high-temperature cooling water returned from a cooling load is dispersed in the air, the cooling water is cooled by the latent heat of water evaporation, stored in a water tank, and circulated again to the cooling load at a set flow rate In
Controlling the amount of blowdown by controlling the opening and closing of a drain valve provided in a drain pipe connected to the water tank, so as to maintain the impurity concentration in the cooling water below an allowable value,
The control of the blowdown amount is performed by obtaining the inlet / outlet temperature difference of the cooling water circulated and supplied to the cooling load for each sampling period, and integrating the inlet / outlet temperature difference for the integration time corresponding to the control period to An integrated value is obtained, and the inlet / outlet temperature is based on the integrated value of the inlet / outlet temperature difference obtained by integrating the inlet / outlet temperature difference when the cooling water is circulated at the set flow rate during the reference load of the cooling load during the integrated time. The ratio of the integrated value of the difference is obtained, and the opening time of the drain valve is obtained by multiplying the ratio by the reference opening time of the drain valve opening time determined in correspondence with the reference integrated value, and according to the opening time. The water quality management method of a cooling tower characterized by controlling the open time of the said drain valve in the control period of this. A casing having an opening at the top, a sprinkling nozzle for cooling water provided at the top of the casing, a water tank for receiving and storing cooling water provided at the bottom of the casing and sprayed from the sprinkling nozzle, and a top opening of the casing A blower that circulates air through the casing, a cooling water pump that sucks the cooling water in the water tank, supplies it to the cooling load and circulates it to the watering nozzle, and maintains the water level of the water tank in the set range A water level control means for supplying makeup water, an overflow pipe whose opening position is set at a water level higher than the upper limit of the water level setting range, and an amount of impurities in the cooling water controlled by controlling the blow-down amount of the cooling water In the cooling tower comprising the water quality management means to maintain below,
The water quality management means is based on a drainage pipe communicating with the water tank, an electric or electromagnetic automatic drainage valve provided in the drainage pipe, and a temperature difference between the inlet and outlet of cooling water circulated and supplied to the cooling load. A control means for controlling the blow-down amount of the cooling water by controlling opening and closing of the automatic drain valve,
The control means obtains a cooling water inlet / outlet temperature difference when the cooling water is circulated at the set flow rate when the cooling load is set as a reference inlet / outlet temperature difference. The reference opening time of the automatic drain valve required to discharge the blowdown amount obtained to determine the evaporation amount of the cooling water in order to maintain the impurity concentration in the cooling water below the allowable value in the set control cycle The inlet / outlet temperature difference of the cooling water circulated and supplied to the cooling load at each control cycle is determined, and the ratio of the inlet / outlet temperature difference of the cooling water to the reference inlet / outlet temperature difference is multiplied by the reference opening time. A cooling tower characterized in that an open time of the automatic drain valve is obtained and the open time of the automatic drain valve is controlled in the next control cycle according to the obtained open time. A casing having an opening at the top, a sprinkling nozzle for cooling water provided at the top of the casing, a water tank for receiving and storing cooling water provided at the bottom of the casing and sprayed from the sprinkling nozzle, and a top opening of the casing A blower that circulates air through the casing, a cooling water pump that sucks the cooling water in the water tank, supplies it to the cooling load and circulates it to the watering nozzle, and maintains the water level of the water tank in the set range A water level control means for supplying makeup water, an overflow pipe whose opening position is set at a water level higher than the upper limit of the water level setting range, and an amount of impurities in the cooling water controlled by controlling the blow-down amount of the cooling water In the cooling tower comprising the water quality management means to maintain below,
The water quality management means is based on a drainage pipe communicating with the water tank, an electric or electromagnetic automatic drainage valve provided in the drainage pipe, and a temperature difference between the inlet and outlet of cooling water circulated and supplied to the cooling load. A control means for controlling the blow-down amount of the cooling water by controlling opening and closing of the automatic drain valve,
The control means obtains the inlet / outlet temperature difference of the cooling water circulated and supplied to the cooling load for each sampling period, integrates the inlet / outlet temperature difference for the integration time corresponding to the control period, and obtains the integrated value of the inlet / outlet temperature difference. The integration of the inlet / outlet temperature difference based on the integrated value of the inlet / outlet temperature difference obtained by integrating the inlet / outlet temperature difference when the cooling water is circulated at the set flow rate during the reference load of the cooling load. The ratio of the value is obtained, the opening time of the automatic drain valve is obtained by multiplying the reference opening time of the automatic drain valve determined in correspondence with the reference integrated value by the ratio, and according to the opening time, A cooling tower for controlling an opening time of the automatic drain valve in a control cycle.

Images