JP5264366B2 - Cooling tower and heat source system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably hold a cooling water temperature within a target temperature range, while restraining a fan frequency from being switched frequently. <P>SOLUTION: This cooling tower sprays a high temperature of cooling water returned from a heat load into air, and cools the cooling water by evaporation latent heat due to air flow in accompaniment to rotation of the fan, to be circulation-supplied again to the heat load, and is provided with a control means for controlling a rotation speed of the fan by a plurality of stages of frequencies, in response to a detected temperature of the cooled cooling temperature. The control means switches the frequency of the fan in each of a lower limit value (25&deg;C) and an upper limit value (28&deg;C), to hold the cooling water temperature CTI within the preset target temperature range (25&deg;-28&deg;C) of the cooling water. The frequency of the fan is switched stepwise in a higher temperature side and a lower temperature side than the target temperature range, to prevent the frequencies of the fan from being switched at once in the plurality of stages. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a cooling tower and a heat source apparatus system, and more particularly to a technique for controlling a rotation frequency of a cooling tower fan.

  For example, the cooling water heated to a high temperature by cooling the heat load with a heat source machine such as an absorption chiller / heater is led to the cooling tower through a pipe, cooled by the cooling tower, and then again through the pipe. Circulated to the heat load. The cooling tower is known as one in which high-temperature cooling water guided from a heat source device is sprayed in a casing and cooled by latent heat of vaporization by a fan provided in the cooling tower.

  By the way, in order to respond to recent energy-saving requirements, energy-saving research on a heat-source unit system including a heat-source unit and a cooling tower has been conducted, and the efficiency of the heat-source unit itself has been improved to some extent.

  However, it is not sufficient to save the energy of the heat source unit itself. For example, it is required to improve the efficiency of the power of a fan used for a pump or a cooling tower that transports cooling water between the heat source unit and the cooling tower.

  In this regard, as described in Patent Document 1, the temperature of the cooling water cooled by the cooling tower is detected, and the number of rotations of the cooling tower fan is controlled by the inverter in a variable manner according to the detected temperature. It is known to increase fan efficiency.

  That is, conventionally, the fan is driven at a frequency of 100% when the cooling water temperature becomes a certain set temperature (for example, 27 ° C.) or more, and the fan is stopped when the temperature becomes a certain set temperature (for example, 24.5 ° C.) or less. Since it was on-off control, the fan was frequently started and stopped, which was not preferable from the viewpoint of fan efficiency. On the other hand, in Patent Document 1, when the detected temperature is between the lower limit set temperature (for example, 24.5 ° C.) and the upper limit set temperature (for example, 27 ° C.), the detected temperature has a one-to-one correspondence. It is said that the number of times the fan is started and stopped can be reduced by driving the fan at a frequency set to be approximately proportional.

JP-A-5-340690

  However, as described in Patent Document 1, when the fan is driven at a frequency set to be approximately proportional to the detected temperature, the fan frequency changes sensitively to the temperature change of the cooling water. Cooling water temperature may be hunting and not stable.

  In this respect, the detected temperature is in a certain temperature range by giving a constant temperature width to each of the set frequencies of the plurality of stages and controlling the fan frequency in a stepwise manner by continuing this stepwise. Since the frequency sometimes does not change, it is considered that the cooling water temperature can be stabilized to some extent.

  By the way, in order to suppress frequent switching of the fan frequency, it is desirable to widen the temperature range at each of the plurality of setting frequencies, but this has a limit. For example, if the range between the lower limit value and upper limit value of the target temperature range is set as the temperature width at each set frequency in order to keep the cooling water temperature within the target temperature range, the frequency can be switched at the same temperature at each set frequency. Therefore, a case where frequency switching over a plurality of stages is performed at a time is not preferable.

  Accordingly, an object of the present invention is to stably keep the cooling water temperature within the target temperature range while suppressing frequent switching of the fan frequency.

  The cooling tower of the present invention sprays high-temperature cooling water returned from the heat load into the air, cools the cooling water with latent heat of vaporization caused by the air flow accompanying the rotation of the fan, and circulates and supplies it again to the heat load. The control unit is configured to control the rotational speed of the fan at a plurality of stages according to the detected temperature of the cooled cooling water.

The control means switches the fan frequency to a higher frequency when the detected temperature of the cooling water rises and reaches an upper limit value of a preset target temperature range with the fan being driven, Further, when the detected temperature of the cooling water rises to a high temperature side that is equal to or higher than the upper limit value, the frequency of the fan is switched higher stepwise in response to the rise in the detected temperature of the cooling water.

On the other hand, when the detected temperature of the cooling water falls from the high temperature side that is equal to or higher than the upper limit value of the target temperature range, the frequency of the fan is not switched until the lower limit value of the target temperature range is reached. When the lower limit of the range is reached, the frequency of the fan is switched to a lower frequency, and when the detected temperature of the cooling water falls to a low temperature lower than the lower limit, the detected temperature of the cooling water is lowered. Correspondingly, the frequency of the fan is switched low in a stepwise manner .

  That is, by providing a temperature range from the lower limit value to the upper limit value of the target temperature range of the cooling water at each frequency of the plurality of stages, it is possible to reduce the frequency of switching the fan frequency due to the temperature variation of the cooling water. In addition to this, since the fan frequency is switched at the lower limit value and the upper limit value of the target temperature range at each frequency of the plurality of stages, the cooling water temperature should be kept stable within the target temperature range. Can do.

  Furthermore, although the frequency of the fan is switched at the lower limit value and the upper limit value of the target temperature range at each frequency of the plurality of stages, for example, switching the frequency at the upper limit value switches the frequency one step lower. Since the condition is set such that the switching is performed only when the cooling water temperature rises thereafter, frequency switching over a plurality of stages can be avoided. As a result, it is possible to stably keep the cooling water temperature within the target temperature range while suppressing frequent switching of the fan frequency.

  In this case, the control means can set the set temperature for switching the frequency of the fan from the set upper limit frequency to a frequency one step lower than the lower limit value of the target temperature range of the cooling water.

  In other words, when the fan frequency is at the set upper limit frequency, it indicates that the load of the heat source unit is high, and the detected temperature is until the temperature at which the fan frequency is switched from the set upper limit frequency to the next lower frequency. It takes time to drop. Therefore, by setting the set temperature that switches the fan frequency from the set upper limit frequency to a frequency that is one step lower than the lower limit value of the target temperature range as an exception, the set temperature is set as early as possible when the detected temperature falls. The fan can be driven with low power by switching the frequency one step down. As a result, the state where the fan is continuously driven at the set upper limit frequency can be avoided as much as possible, and energy saving can be achieved.

  Also, a heat source unit, the above-described cooling tower, a pipe for guiding the high-temperature cooling water returned from the heat load of the heat source unit to the cooling tower, and a pipe for leading the cooling water cooled by the cooling tower to the heat load of the heat source unit The heat source machine system can be configured.

  According to the present invention, the cooling water temperature can be stably maintained within the target temperature range while suppressing frequent switching of the fan frequency.

  Hereinafter, embodiments of a cooling tower and a heat source system to which the present invention is applied will be described. FIG. 1 is a diagram illustrating an overall configuration of a heat source apparatus system according to the present embodiment. As shown in FIG. 1, the heat source apparatus system 100 includes a cooling tower 10, a heat source apparatus 20, and a cooling water pipe 30. The heat source device 20 is a device that needs to cool a heat load using cooling water cooled by a cooling tower, such as an absorption chiller / heater.

  The cooling tower 10 includes a cylindrical casing 11, an air inlet 12 is formed on the lower side surface of the casing 11, and a cooling water tank 13 is provided at the bottom. The air inlet 12 is formed in a louver shape. A filler 14 is accommodated in the casing 11 above the position of the air inlet 12, and a cooling water sprinkling nozzle 15 is disposed above the filler 14.

  An opening 16 is provided at the top of the casing 11. A fan motor 18 is fixed to the opening 16 by a fixture 17, and a fan 19 is fixed to the rotation shaft of the fan motor 18. In addition, the replenishment water of the cooling water to the water tank 13 of the cooling tower 10 is supplied from the water supply port which has a ball tap etc. which are not shown in figure.

  The cooling water pipe 30 includes an outgoing pipe 31 and a return pipe 32. In the outgoing pipe 31, a cooling water pump 33 and a check valve 34 are arranged in order from the cooling tower 10 toward the heat source unit 20. The suction port of the cooling water pump 33 communicates with the vicinity of the bottom of the water tank 13. The discharge port of the cooling water pump 33 is connected via a check valve 34 to a heat exchanger (not shown) that can exchange heat with the heat load of the heat source unit 20. A cooling water temperature sensor 51 is provided between the check valve 34 of the outgoing pipe 31 and a heat exchanger (not shown) (inlet part of the heat source unit 20). An output signal of the cooling water temperature sensor 51 is provided. Is input to an operation control device 50 described later.

  The return pipe 32 is provided with an electric three-way valve 41 and a bypass pipe 42 that guides cooling water of the return pipe 32 to the water tank 13 when the electric three-way valve 41 is opened by a bypass command.

  The operation control device 50 includes a control device 53 and an inverter device 55. The control device 53 forms a frequency signal for rotationally driving the fan motor 18 and the fan 19 at a frequency set in advance according to the temperature signal detected by the cooling water temperature sensor 51, and gives it to the inverter device 55.

  Further, the control device 53 forms a bypass command signal based on the detected temperature signal from the cooling water temperature sensor 51 and gives it to the electric three-way valve 41 to bypass the cooling water. For example, when the detected temperature of the cooling water is lower than the lower limit set temperature (for example, 24 ° C.), the electric three-way valve 41 is switched to drop the return cooling water from the heat source unit 20 directly into the water tank 13 of the cooling tower 10. Prevents cooling water from being overcooled.

  In the present embodiment, for convenience of explanation, the control device 53 is provided independently of the cooling tower 10 and the heat source unit 20, but is provided attached to the cooling tower 10 as one component of the cooling tower 10. Alternatively, it can be attached to the heat source unit 20 and can be a component of the heat source unit system 100.

  FIG. 2 is a block diagram showing a detailed configuration of the control device 53. The control device 53 shown in FIG. 2 includes a central processing unit 531, a storage device 532, an input signal unit 533, an output signal unit 534, and the like. The control device 53 starts to operate as the cooling tower 10 starts operating. Then, the central processing unit 531 operates based on the program stored in the storage device 532, and the frequency set in advance according to the data fetched from the cooling water temperature sensor 51 via the input signal unit 533. Thus, a frequency signal for rotationally driving the fan motor 18 and the fan 19 can be formed and supplied to the inverter device 55 via the output signal unit 534.

  In the heat source apparatus system 100 configured as described above, the temperature detected by the cooling water temperature sensor 51 of the cooling water is conventionally set between the lower limit set temperature (for example, 24.5 ° C.) and the upper limit set temperature (for example, 27 ° C.). The rotational frequency of the fan 19 is controlled so that the temperature is maintained. For example, the fan frequency is set to be proportional to the detected temperature so that the fan frequency is increased when the detected temperature is higher than the set temperature, and the fan frequency is decreased when the detected temperature is lower. It is known to drive the fan 19 at a frequency of

  However, in such a conventional technique, the frequency of the fan 19 changes sensitively to the temperature change of the cooling water, so that the cooling water temperature may be hunted and unstable.

  In this respect, the detected temperature is in a certain temperature range by giving a constant temperature width to each of the set frequencies of the plurality of stages and controlling the fan frequency in a stepwise manner by continuing this stepwise. Since the frequency sometimes does not change, it is considered that the cooling water temperature can be stabilized to some extent.

  However, in order to keep the cooling water temperature stable within the target temperature range while suppressing frequent switching of the fan frequency, it is desirable to widen the temperature range at each of the multiple set frequencies. There is. For example, if the temperature range of each set frequency is set between the lower limit value and the upper limit value of the target temperature range of the cooling water temperature, the frequency can be switched at the same temperature at each set frequency. The case where it is performed at once occurs is not preferable.

  The heat source machine system 100 and the cooling tower 10 of this embodiment are made to cope with such a problem. Hereinafter, the frequency control contents of the fan of the control device 53 that is a characteristic part of the heat source apparatus system 100 and the cooling tower 10 of the present embodiment will be described in detail for each example.

  FIG. 3 is a diagram showing the frequency control contents of the fan of the first example of the control device 53 in the heat source apparatus system 100 and the cooling tower 10 of the present embodiment. In FIG. 3, the horizontal axis represents the cooling water inlet temperature (° C.) (hereinafter referred to as CTI as appropriate) detected by the cooling water temperature sensor 51, and the vertical axis represents the ratio when the frequency rating of the fan 19 is 100%. ing.

  Each arrow in FIG. 3 indicates a control content for switching the frequency of the fan 19 higher or lower corresponding to the CTI. After the frequency is switched, the control condition on the control line indicated by each arrow Frequency switching is performed. For example, when the CTI increases from less than 28 ° C. to 28 ° C. while the fan 19 is driven at a frequency of 70%, the frequency of the fan 19 is switched to 80% according to the arrow, and thereafter the control line indicated by the arrow. When the control condition of whether the above CTI falls to 25 ° C. or rises to 29 ° C. is satisfied, the frequency is switched.

  In addition, although two control lines are shown across the frequencies of the fan 19 at 80% and 90%, respectively, this is shifted from 80% and 90% for convenience of explanation. Are assumed to have two control lines on 80% and 90%, respectively.

  First, as shown in FIG. 3, the control of the fan frequency of the control device 53 of this embodiment is performed by turning off the fan 19 or 70%, 80%, 90%, 100 with respect to the detected temperature of the cooling water. It is designed to be driven to rotate at any frequency of%. In this embodiment, the case where the frequency of the fan 19 is switched to four stages will be described as an example. However, the frequency of the fan 19 may be set with other stages. Further, the set value of the cooling water inlet temperature and the set value of the frequency of the fan 19 can be appropriately changed and used.

  In addition, the control of the fan frequency of the control device 53 of the present embodiment is such that a certain temperature range is provided at each stage in a plurality of stages of frequency setting, and the fan 19 frequency is increased stepwise. It is configured to switch.

  More specifically, in this embodiment, the target temperature of the cooling water is set in advance to 25 ° C. to 28 ° C., and the fan 19 is switched from the OFF state to the 70% frequency with the exception of any set frequency. The frequency is not switched within the target temperature range. In other words, a temperature range of 25 ° C. to 28 ° C. is provided at each stage in the frequency setting of a plurality of stages.

  An example of the operation of controlling the fan frequency of the control device 53 of the present embodiment will be described. For example, if the CTI rises from less than 28 ° C. to 28 ° C. while the fan 19 is driven at 70% frequency, the frequency of the fan 19 is increased. Is switched to 80%. If the CTI further increases to 29 ° C. in this state, the frequency of the fan 19 is switched to 90%. If the CTI further rises to 30 ° C. in this state, the frequency of the fan 19 is switched to 100%.

  That is, in response to an increase in CTI after the frequency of the fan 19 is switched to a higher frequency, the fan frequency is switched in a stepwise manner on the high temperature side that is equal to or higher than the upper limit (28 ° C.) of the target temperature range of the cooling water. It is supposed to be.

  For example, when the CTI rises from less than 28 ° C. to 28 ° C. while the fan 19 is driven at a frequency of 70% and the frequency of the fan 19 is switched to 80%, the CTI falls to 25 ° C. The frequency of the fan 19 is switched to 70%. Similarly, when the CTI drops to 25 ° C. while the frequency of the fan 19 is switched from 80% to 90% and from 90% to 100%, the frequency of the fan 19 is switched to 80% and 90%, respectively. It is done.

  That is, after the frequency of the fan 19 is switched to a higher frequency, when the CTI falls to the lower limit value (25 ° C.) of the target temperature range of the cooling water, the frequency of the fan 19 can be switched to a lower frequency. ing. It should be noted that the case where the fan 19 is driven off at 70% is excluded as an exception, and the fan 19 is not turned off even when the CTI is lowered to 25 ° C., and is turned off only after the temperature is lowered to 23 ° C. The

  On the other hand, for example, when the CTI is lowered from 25 ° C. to 25 ° C. while the fan 19 is driven at 100% frequency, the frequency of the fan 19 is switched to 90%. If the CTI further decreases in this state, the frequency of the fan 19 is sequentially switched to 80%, 70%, and OFF.

  That is, the frequency of the fan 19 is gradually decreased on the low temperature side below the lower limit (25 ° C.) of the target temperature range of the cooling water in response to the decrease in CTI after the frequency of the fan 19 is switched to a lower frequency. It can be switched.

  Further, for example, when the fan 19 is driven at a 100% frequency, the CTI increases from 25 ° C. to 25 ° C. and the frequency of the fan 19 is switched to 90%, and the CTI increases to 28 ° C. In this case, the frequency of the fan 19 is switched to 100%. Similarly, when the CTI rises to 28 ° C. while the frequency of the fan 19 is switched from 90% to 80% and from 80% to 70%, the frequency of the fan 19 is switched to 90% and 80%, respectively. It is done.

  That is, when the CTI rises to the upper limit (28 ° C.) of the target temperature range of the cooling water after the frequency of the fan 19 is switched to a lower frequency, the frequency of the fan 19 can be switched to a higher frequency. ing. Note that the case where the frequency is switched to 70% from the state where the fan 19 is OFF is excluded as an exception. When the CTI rises to 26 ° C., the frequency of the fan 19 is switched to 70%.

  As described above, the control of the fan frequency of the control device 53 of the present embodiment has a stage of switching the frequency of the fan 19 from 70% to 80%, from 80% to 90%, and from 90% to 100% at CTI 28 ° C. However, there is a step of switching the frequency of the fan 19 from 100% to 90%, from 90% to 80%, and from 80% to 70% at CTI 25 ° C.

  According to this, since the temperature range from the lower limit value to the upper limit value of the target temperature range of the cooling water is provided at each frequency of the plurality of stages, switching of the frequency of the fan 19 with respect to the fluctuation of the cooling water temperature is reduced. can do.

  Further, since the frequency of the fan 19 is switched at the lower limit value and the upper limit value of the target temperature range at each of the multiple stages of frequencies, the frequency of the fan 19 is maintained so as to keep the cooling water temperature within the target temperature range. Control is performed.

  In addition, although the frequency of the fan 19 is switched at the lower limit value and the upper limit value of the target temperature range at each frequency of the plurality of stages, these are, for example, the upper limit value of the target temperature range. The frequency of the fan 19 is switched only when the CTI rises to the upper limit value after the frequency of the fan 19 is switched one step lower. In other words, the switching of the frequency of the fan 19 between the lower limit value and the upper limit value of the target temperature range is a conditionally controlled control. As a result, switching of frequencies at two or more stages at a time is avoided.

  FIG. 4 is a diagram showing the frequency control contents of the fan of the second example of the control device 53 in the heat source apparatus system 100 and the cooling tower 10 of the present embodiment.

  In the present embodiment, the set temperature for switching the frequency of the fan 19 from the set upper limit frequency (100%) to the lower frequency (90%) is changed, and the CTI is further lowered after the frequency of the fan 19 is further lowered by this change. The first embodiment is that the temperature condition for switching the frequency to a low level when the air pressure decreases is changed, and the temperature condition for switching the frequency to 100% after the frequency of the fan 19 is switched from 100% to 90%. Is different. A description of the same parts as in the first embodiment will be omitted.

  As shown in FIG. 4, in this embodiment, the set temperature for switching the frequency of the fan 19 from the set upper limit frequency (100%) to the lower frequency (90%) is set to the lower limit value (25 ° C.) of the target temperature range of the cooling water. ) Is set to 26 ° C. on the higher temperature side. In addition, the set temperature for switching the frequency of the fan 19 low when the CTI further decreases after the frequency of the fan 19 is lowered to 90% is set to 25 ° C. Further, the set temperature at which the frequency of the fan 19 is switched low when the CTI further decreases after the frequency of the fan 19 is lowered to 80% is set to 24 ° C. Further, the set temperature for switching the frequency of the fan 19 to 100% when the CTI increases after the frequency of the fan 19 is switched from 100% to 90% is set to 29 ° C.

  That is, the fact that the fan 19 is driven at a frequency of 100% of the rating indicates that the load of the heat source device 20 is high. When the heat source device 20 has a high load, the CTI is unlikely to decrease, but when it begins to decrease, it is preferable to switch the frequency of the fan 19 from the upper limit frequency (100%) to the next lower frequency (90%) as soon as possible. Therefore, when the fan 19 is driven at a rated frequency of 100%, the CTI set temperature for switching the frequency of the fan 19 from the upper limit frequency (100%) to the next lower frequency (90%) is 25 ° C. to 26 ° C. It is shifted to.

  According to this, by setting the apparent target temperature of the CTI to be higher, the frequency can be switched to a lower stage earlier when the CTI is lowered, and the fan 19 can be driven with low power. As a result, it is possible to avoid the state where the fan is continuously driven at the set upper limit frequency (100%) as much as possible, and energy saving can be achieved.

  Further, according to the present embodiment, the cooling water temperature is set within the target temperature range of 25 ° C. to 28 ° C. while saving energy by driving the frequency of the fan 19 at 70%, 80%, 90% lower than the rated frequency. It becomes possible to control the frequency of the fan 19 so as to enter.

It is a figure showing the whole heat source machine system composition of this embodiment. It is a block diagram which shows the detailed structure of a control apparatus. It is a figure which shows the frequency control content of the fan of the 1st Example of the control apparatus in the heat-source equipment system and cooling tower of this embodiment. It is a figure which shows the frequency control content of the fan of 2nd Example of the control apparatus in the heat-source equipment system and cooling tower of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Cooling tower 11 Casing 12 Air inlet 14 Filling material 15 Sprinkling nozzle 16 Opening 18 Fan motor 19 Fan 20 Heat source machine 30 Cooling water piping 31 Outward pipe 32 Return pipe 50 Operation control apparatus 51 Cooling water temperature sensor 53 Control apparatus 55 Inverter apparatus 100 heat source system

Claims (3)

The high-temperature cooling water returned from the heat load is dispersed in the air, the cooling water is cooled by the latent heat of vaporization caused by the air flow accompanying the rotation of the fan, and is circulated again to the heat load. In the cooling tower comprising a control means for controlling the rotational speed of the fan at a plurality of stages according to the detected temperature of the cooling water,
The control means switches the frequency of the fan to a higher frequency when the detected temperature of the cooling water rises and reaches an upper limit value of a preset target temperature range with the fan being driven. Furthermore, when the detected temperature of the cooling water rises to a high temperature side that is equal to or higher than the upper limit value, the frequency of the fan is switched stepwise in response to an increase in the detected temperature of the cooling water,
When the detected temperature of the cooling water falls from a high temperature side that is equal to or higher than the upper limit value of the target temperature range, the frequency of the fan is not switched until the lower limit value of the target temperature range is reached, When the lower limit value is reached, the frequency of the fan is switched to a lower frequency, and when the detected temperature of the cooling water falls to a low temperature lower than the lower limit value, this corresponds to a decrease in the detected temperature of the cooling water. The cooling tower is characterized by switching the frequency of the fan in a stepwise manner . Said control means, the set temperature of the detected temperature of the cooling water switched to one step lower frequencies the frequency of the fan from a preset upper limit frequency, and set to the high temperature side than the lower limit of the target temperature range of the cooling water cooling tower of claim 1 comprising Te.   A heat source unit, a cooling tower according to claim 1 or 2, a pipe for guiding high-temperature cooling water returned from a heat load of the heat source unit to the cooling tower, and cooling water cooled by the cooling tower of the heat source unit A heat source system configured with piping leading to a heat load.

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