JP2021046987A - Cold water manufacturing system - Google Patents

Abstract

To manufacture cold water having a desired temperature while preventing the freezing of water in a heat exchanger by accurately regulating the flow of brine passing through the brine-water heat exchanger.SOLUTION: A cold water manufacturing system includes a brine tank 2 for storing brine, a chiller 3 for chilling the brine from the brine tank 2, a heat exchanger 4 for making a heat exchange with the brine chilled by the chiller 3 to cool water, and a brine pump 12 for supplying the brine from the brine tank 2 via the chiller 3 to the heat exchanger 4. A brine supply path 10 from the chiller 3 to the heat exchanger 4, and a brine discharge path 11 from the heat exchanger 4 to the brine tank 2 are connected via a bypass passage 5. In a joint part between the brine discharge path 11 and the bypass passage 5, a brine valve 6 consisting of a three-way valve is provided. The brine valve 6 can cut off the supply of the brine to the heat exchanger 4 and regulate the supply flow of the brine to the heat exchanger 4.SELECTED DRAWING: Figure 1

Description

The present invention relates to a cold water production system in which cold water is produced by cooling water with brine cooled by a chiller.

Conventionally, as disclosed in Patent Document 1 below, (i) a refrigerator or a heat pump, (ii) a heat exchanger between brine and cold water, and (iii) a brine pipe connecting both, a brine circulation pump, and a brine. A chilled water production system including equipment having a tank and (iv) chilled water piping connected to a heat exchanger, a chilled water supply pump, and equipment having a chilled water tank is known. According to this system, the brine can be cooled by a chiller (refrigerator or the like), and the brine cools the water in the heat exchanger to produce cold water.

When producing cold water at a relatively low temperature (for example, 3 ° C. or lower) using this type of cold water production system, there are the following problems. That is, unless the flow rate of brine passed through the heat exchanger is adjusted accurately, cold water having a desired temperature cannot be produced, and the water may be frozen in the heat exchanger. It is difficult to solve the above-mentioned problems in relation to the minimum frequency (minimum flow rate) by simply controlling the brine circulation pump with an inverter.

In addition, the cold water production system cools the cold water in the cold water tank to the target temperature while adjusting the brine flow rate through the heat exchanger, but when this cooling is completed, further cooling of the cold water (and thus the heat exchanger). It is necessary to ensure that the supply of brine to the heat exchanger is cut off in order to prevent freezing of water in the heat exchanger. Furthermore, even if the cooling of the water is completed, it may be desired to circulate the brine in the brine tank to the chiller to cool it to the target brine temperature, but in that case, the cold water is cooled more than necessary (and thus in the heat exchanger). In order to prevent (freezing of water), it is necessary to have a configuration in which the brine can be circulated to the chiller while blocking the supply of the brine to the heat exchanger. Therefore, regarding the supply of brine to the heat exchanger, it is necessary to have a configuration in which not only the flow rate can be adjusted but also the supply of brine to the heat exchanger can be cut off if desired.

In addition, it is necessary to circulate the brine with the brine pump to the heat exchanger and to prevent the brine from leaking to the cold water side even if the heat exchanger is damaged while the cold water is circulated by the cold water pump. There is.

Furthermore, when the cooling of cold water is completed without the cold load (cold water or the load of using the cold water), the water temperature in the cold water tank remains low, but even in that state, the brine pump or cold water If the pumps continue to operate, the power of each pump will continue to be consumed. On the other hand, if both pumps are stopped, for example, the rise in water temperature cannot be detected on the cold water outlet side of the heat exchanger, and in the unlikely event that the heat exchanger is damaged, leakage of the brine to the cold water side cannot be prevented. ..

Japanese Patent Application Laid-Open No. 4-143570 (Claims)

An object to be solved by the present invention is to provide a cold water production system capable of accurately adjusting the flow rate of brine passing through a heat exchanger and producing cold water at a desired temperature while preventing water from freezing in the heat exchanger. It is in. Further, to provide a cold water production system capable of preventing leakage of brine to the cold water side in the unlikely event of damage to the heat exchanger, and saving energy by stopping the brine pump when desired. Is the subject.

The present invention has been made to solve the above problems, and the invention according to claim 1 has a brine tank for storing brine, a chiller for cooling the brine from the brine tank, and the chiller for cooling. A heat exchanger that cools water by heat exchange with the brine, a brine pump that supplies brine from the brine tank to the heat exchanger via the chiller, and a brine supply path from the chiller to the heat exchanger. At the junction of the bypass passage connecting the heat exchanger to the brine discharge passage and the brine discharge passage and the bypass passage, or at the branching portion of the brine supply passage and the bypass passage. A cold water production system comprising a three-way valve provided, which is provided with a brine valve capable of shutting off the supply of brine to the heat exchanger and adjusting the supply flow rate of brine to the heat exchanger. is there.

According to the invention of claim 1, the brine supply path from the chiller to the heat exchanger and the brine discharge path from the heat exchanger to the brine tank are connected by a bypass path, and the brine discharge path and the bypass path are connected. A brine valve consisting of a three-way valve is provided at the confluence (or the branch between the brine supply path and the bypass path). With this brine valve, it is possible to adjust the distribution ratio of returning the brine from the chiller to the brine tank via the heat exchanger or returning to the brine tank via the bypass path. As a result, the flow rate of brine passed through the heat exchanger can be adjusted accurately while maintaining the amount of brine circulating to the chiller, so that cold water at a desired temperature can be produced while preventing water from freezing in the heat exchanger. ..

Moreover, since the brine valve is composed of a three-way valve provided at the connection between the brine discharge path (or the brine supply path) and the bypass path, not only can the supply flow rate of the brine to the heat exchanger be adjusted. The supply of brine to the heat exchanger can be cut off when desired. Therefore, after the cold water has been cooled to the target temperature, the supply of brine to the heat exchanger can be reliably cut off, and unnecessary cooling of the cold water (and thus freezing of water in the heat exchanger) can be prevented. Furthermore, even if you want to cool the cold water to the target temperature and then circulate the brine in the brine tank to the chiller to cool it to the target brine temperature, the supply of brine to the heat exchanger is cut off and the brine is passed through the bypass path. The brine can be circulated through the chiller, preventing excessive cooling of cold water (and thus freezing of water in the heat exchanger).

According to the second aspect of the present invention, the heat exchanger is passed through the brine by the brine pump and water by the cold water pump, and the pressure of the water in the heat exchanger is higher than the pressure of the brine. The cold water production system according to claim 1, wherein the rotation speed of the cold water pump is controlled so as to be described.

According to the second aspect of the present invention, by controlling the rotation speed of the chilled water pump to make the pressure of water in the heat exchanger higher than the pressure of the brine, even in the unlikely event that the heat exchanger is damaged. It is possible to prevent leakage of the brine to the cold water side and enhance safety.

In the invention according to claim 3, the pressure of the brine is monitored by a brine pressure sensor provided in the brine supply path after branching from the bypass path, and the pressure of the water is the cold water of the heat exchanger. The chilled water production system according to claim 2, wherein the chilled water pressure sensor provided on the outlet side monitors the chilled water pressure sensor.

According to the third aspect of the invention, the brine pressure is monitored on the brine inlet side of the heat exchanger, while the water pressure is monitored on the chilled water outlet side of the heat exchanger. Considering the pressure loss in the heat exchanger, by monitoring each pressure at the place where the pressure of the brine is high and the place where the pressure of the water is low, even if the heat exchanger is damaged, the brine Leakage to the cold water side can be prevented more reliably, and safety can be enhanced.

In the invention according to claim 4, the opening degree of the brine valve is adjusted so that the water temperature on the outlet side of the heat exchanger becomes a set temperature, and the opening degree of supplying brine to the heat exchanger by the brine valve. The cold water production system according to claim 2 or 3, wherein the brine pump is stopped when the fully closed state is continued for the brine pump stop determination time.

According to the invention of claim 4, power consumption can be reduced by stopping the brine pump at a set timing after cooling the cold water to a target temperature.

Further, the invention according to claim 5 is the cold water production system according to claim 4, wherein the rotation speed of the chilled water pump is reduced after the brine pump is stopped.

According to the fifth aspect of the present invention, the power consumption can be further reduced by lowering the rotation speed of the chilled water pump after the brine pump is stopped. In addition, by continuing the operation of the chilled water pump with the brine pump stopped, even if the heat exchanger is damaged, leakage of the brine to the cold water side can be prevented and safety can be improved. .. Further, by continuing the operation of the chilled water pump, it is possible to detect an increase in water temperature (generation of a chilled heat load), for example, on the chilled water outlet side of the heat exchanger.

According to the cold water production system of the present invention, it is possible to accurately adjust the flow rate of brine passing through the heat exchanger and produce cold water at a desired temperature while preventing water from freezing in the heat exchanger. Further, in the unlikely event that the heat exchanger is damaged, leakage of the brine to the cold water side can be prevented, and if desired, the brine pump can be stopped to save energy.

It is the schematic which shows the cold water production system of one Example of this invention. It is a flowchart which shows the transition process from the normal operation to the energy-saving operation. It is a flowchart which shows the return process from the energy saving operation to the normal operation.

Hereinafter, specific examples of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic view showing a cold water production system 1 according to an embodiment of the present invention.

The cold water production system 1 of the present embodiment cools water by heat exchange between a brine tank 2 for storing brine, a chiller 3 for cooling the brine from the brine tank 2, and the brine cooled by the chiller 3. The heat exchanger 4, the bypass path 5 connecting the inlet side and the outlet side of the brine to the heat exchanger 4, the supply of the brine to the heat exchanger 4 can be cut off, and the brine to the heat exchanger 4 can be cut off. A brine valve 6 capable of adjusting the supply flow rate of the water exchanger 4 and a cold water tank 7 in which water is circulated between the heat exchanger 4 and the heat exchanger 4 are provided.

The brine tank 2 is a container for storing brine, and in this embodiment, the inside is open to atmospheric pressure. The brine tank 2 is provided with a liquid level detector 8 to store brine up to a set liquid level. The type of brine is not particularly limited, but when cold water produced by heat exchange with brine is used for food cooling, it is a food additive so that it is safe against leakage of brine due to damage to the heat exchanger 4. It is preferable to use brine (for example, propylene glycol) which is also acceptable.

The chiller 3 includes a refrigerator (not shown). The refrigerator is a vapor compression type refrigerator in this embodiment. In this case, the refrigerator is configured by sequentially connecting a compressor, a condenser, an expansion valve and an evaporator in an annular shape. The compressor compresses the refrigerant into a high-temperature, high-pressure gas. The condenser liquefies the refrigerant from the compressor. The expansion valve reduces the pressure and temperature of the refrigerant by allowing the refrigerant from the condenser to pass through. The evaporator then evaporates the refrigerant from the expansion valve. In the evaporator, heat can be exchanged between the brine from the brine tank and the refrigerant of the refrigerator without mixing, and the brine can be cooled by the heat of vaporization of the refrigerant.

The heat exchanger 4 includes a flow path on the brine side and a flow path on the water side so that heat can be exchanged without mixing the brine and water. The structure of the heat exchanger 4 is not particularly limited, but is, for example, a plate heat exchanger.

Brine is supplied from the brine tank 2 to the chiller 3 (more specifically, the evaporator of the refrigerator) via the brine delivery path 9. The brine cooled by the chiller 3 can be supplied to the heat exchanger 4 via the brine supply path 10. The brine after heat exchange in the heat exchanger 4 is returned to the brine tank 2 via the brine discharge path 11. A brine pump 12 is provided in the brine delivery path 9, and by operating the brine pump 12, the brine in the brine tank 2 can be circulated to and from the heat exchanger 4 via the chiller 3. Will be done. The brine pump 12 may be built in the chiller 3 in some cases.

The brine supply path 10 from the chiller 3 to the heat exchanger 4 and the brine discharge path 11 from the heat exchanger 4 to the brine tank 2 are connected by a bypass path 5. A brine valve 6 composed of a three-way valve is provided at the confluence of the brine discharge path 11 and the bypass path 5. By controlling the brine valve 6, the distribution ratio of returning the brine from the chiller 3 to the brine tank 2 via the heat exchanger 4 or returning to the brine tank 2 via the bypass path 5 is adjusted. Can be done.

The brine valve 6 not only allows the flow rate of brine supply to the heat exchanger 4 to be adjusted, but also allows the supply of brine to the heat exchanger 4 to be cut off, if desired. In a state where the supply of brine to the heat exchanger 4 by the brine valve 6 is cut off (that is, a state in which the entire amount is bypassed), the brine in the brine tank 2 is blown by the brine pump 12 through the chiller 3 and the bypass path 5. It can be returned to 2 to promote circulation. Thereby, when desired, the brine in the brine tank 2 can be circulated to the chiller 3 to cool the brine without passing the brine through the heat exchanger 4.

The cold water tank 7 is a container for storing water, and in this embodiment, the inside is open to atmospheric pressure. The cold water tank 7 is provided with a water level detector (not shown). By controlling the supply of water to the chilled water tank 7 based on the detection signal of the water level detector, the inside of the chilled water tank 7 is maintained at the set water level.

Water is supplied from the chilled water tank 7 to the heat exchanger 4 via the chilled water inlet passage 13. The water cooled by the heat exchanger 4 is returned to the chilled water tank 7 via the chilled water outlet passage 14. A chilled water pump 15 is provided in the chilled water inlet passage 13, and by operating the chilled water pump 15, the water in the chilled water tank 7 can be circulated to and from the heat exchanger 4.

If desired, the cold water in the cold water tank 7 is supplied to a cold water demanding place (for example, a food machine) and used. The used water at the cold water demand point is either thrown away or returned to the cold water tank 7. Even in the former case (disposable cold water), water can be appropriately supplied to the cold water tank 7 as described above, so that the cold water tank 7 is maintained at the set water level. In the latter case (cold water circulation), the chilled water in the chilled water tank 7 can be circulated to and from the chilled water demanding portion, and after cooling the object to be cooled at the chilled heat demanding portion, it is returned to the chilled water tank 7.

The cold water production system 1 includes a brine temperature sensor (not shown) for detecting the temperature of brine, and a cold water temperature sensor 16 for detecting the temperature of cold water. The brine temperature sensor is built in the chiller 3 in this embodiment, and detects the brine temperature on the brine outlet side of the chiller 3. On the other hand, the chilled water temperature sensor 16 is provided in the chilled water outlet path 14 in this embodiment, and detects the water temperature on the chilled water outlet side of the heat exchanger 4.

Further, the chilled water production system 1 includes a brine pressure sensor 17 that detects the pressure of the brine in the heat exchanger 4, and a chilled water pressure sensor 18 that detects the pressure of water in the heat exchanger 4. The brine pressure sensor 17 preferably detects the brine pressure on the brine inlet side with respect to the heat exchanger 4. In this embodiment, the brine pressure sensor 17 is provided in the brine supply path 10 after branching from the bypass path 5 in the brine supply path 10 to the heat exchanger 4. On the other hand, the chilled water pressure sensor 18 preferably detects the pressure of chilled water on the chilled water outlet side with respect to the heat exchanger 4. In this embodiment, the chilled water pressure sensor 18 is provided in the chilled water outlet path 14 from the heat exchanger 4.

Next, an operation example of the cold water production system 1 of this embodiment will be described. The operation described below is automatically performed by a controller (not shown). That is, the controller is connected to the chiller 3, the brine valve 6, the brine pump 12, the chilled water pump 15, the brine temperature sensor (not shown), the chilled water temperature sensor 16, the brine pressure sensor 17, the chilled water pressure sensor 18, and the like. The chiller 3, the brine valve 6, and the pumps 12, 15 and the like are controlled based on the detection signals and elapsed time of these sensors. In this embodiment, the brine pump 12 and the chilled water pump 15 can change the drive frequency of the motor and the rotation speed by the inverter.

With the start of operation of the cold water production system 1, the pumps 12, 15 and the chiller 3 are operated. By operating the brine pump 12, the brine in the brine tank 2 circulates with the heat exchanger 4 via the chiller 3. By operating the chilled water pump 15, the water in the chilled water tank 7 circulates with the heat exchanger 4. The brine is cooled in the chiller 3, and the cooled brine cools the water in the heat exchanger 4. As described above, the cold water in the cold water tank 7 or the cold heat thereof is made available at the cold water demand point.

During the circulation of the brine by the brine pump 12, the brine can be cooled by the chiller 3. In this embodiment, the chiller 3 is volume-controlled so that the outlet side brine temperature is set to the brine target temperature (for example, -2 ° C.). Specifically, the compressor motor is inverter-controlled so as to maintain the detection temperature of the brine temperature sensor at the brine target temperature. At this time, the following control may be performed.

That is, a plurality of temperature ranges are provided above and below the target temperature range including the brine target temperature, and the increase / decrease value of the inverter frequency is set according to each temperature range. Then, it monitors which temperature range it is in every set time and maintains the current frequency if it is in the target temperature range, while lowering the frequency if it is in the temperature range on the lower temperature side than the target temperature range, while on the high temperature side. If it is in the temperature range, it is controlled to raise the frequency.

During the operation of each of the pumps 12 and 15, the brine valve 6 is controlled so that the water temperature on the outlet side of the heat exchanger 4 becomes a set temperature. Specifically, the brine valve 6 is controlled so that the detection temperature of the chilled water temperature sensor 16 is maintained at the set temperature, and the brine from the chiller 3 is returned to the brine tank 2 via the heat exchanger 4. The distribution ratio of returning to the brine tank 2 via the bypass path 5 is adjusted. Thereby, the flow rate of the brine passing through the heat exchanger 4 can be adjusted while maintaining the amount of brine circulating to the chiller 3.

Even if a temperature exceeding 0 ° C. is set as the cooling target temperature of the chilled water, the actual chilled water temperature (cold water temperature after cooling by the heat exchanger 4) fluctuates slightly up and down near the target temperature. Therefore, when the cooling target temperature of the cold water is relatively low (for example, 3 ° C. or lower), there is a possibility that the water freezes in the heat exchanger 4. In order to prevent this, the opening degree of the brine valve 6 may be adjusted (preferably PID control) so that the water temperature on the outlet side of the heat exchanger 4 is set to "target temperature + set value" as the set temperature. ..

The opening degree of the brine valve 6 is the opening degree of supply of the brine to the heat exchanger 4 by the brine valve 6, and in the fully closed state (opening 0%), the total amount of brine from the chiller 3 is the bypass path 5. In the fully open state (opening 100%), all the brine from the chiller 3 is supplied to the heat exchanger 4 and is not passed through the bypass path 5.

When adjusting the opening degree of the brine valve 6, the opening degree may be adjusted within the range of the upper limit opening degree and the lower limit opening degree. In that case, the upper limit opening and the lower limit opening can be changed according to the situation. The upper limit opening (in other words, the upper limit of the flow rate passed through the heat exchanger 4) and the lower limit opening (in other words, the lower limit value of the flow rate passed through the heat exchanger 4) are determined by experiments or the like so as to exert the desired effects. Desired.

When starting the brine supply from the stopped state of the brine supply to the heat exchanger 4, the brine supply to the heat exchanger 4 is started within the range not exceeding the upper limit opening to prevent a sudden decrease in the chilled water temperature. Therefore, it is possible to prevent the water in the heat exchanger 4 from freezing. Further, even if the temperature of the brine is lower than expected, it is possible to prevent the water in the heat exchanger 4 from freezing. Further, even if the water temperature on the outlet side of the heat exchanger 4 is controlled to be "target temperature + set value", by supplying brine to the heat exchanger 4 within a range not below the lower limit opening, if necessary. The brine can continue to flow through the heat exchanger 4, and the water can be gradually cooled to the target temperature.

Instead of controlling the brine valve 6 so that the outlet side water temperature of the heat exchanger 4 is "target temperature + set value", the brine valve 6 is set so that the outlet side water temperature of the heat exchanger 4 is "target temperature". May be controlled (preferably PID control). In this control, when adjusting the opening degree of the brine valve 6, it is preferable to set at least the lower limit opening degree and adjust the opening degree at the lower limit opening degree or more. As described above, the lower limit opening may be changed depending on the situation. Then, before the water temperature on the outlet side of the heat exchanger 4 reaches the target temperature, the cold water may be cooled with the brine valve 6 as the lower limit opening degree. For example, when the water temperature on the outlet side of the heat exchanger 4 becomes lower than a predetermined temperature (for example, 1.4 ° C) higher than the target temperature (for example, 1 ° C) while cooling cold water, or the temperature is kept below the predetermined temperature for a predetermined time. Occasionally, the opening degree of the brine valve 6 may be fixed to the lower limit opening degree and cooled to the target temperature. When the water temperature on the outlet side of the heat exchanger 4 becomes equal to or lower than the target temperature, the brine valve 6 may be fully closed to shut off the supply of brine to the heat exchanger 4. By holding the brine valve 6 at the lower limit opening degree when the chilled water temperature approaches the target temperature, the chilled water can be cooled to the target temperature while limiting the supply flow rate of the brine to the heat exchanger 4. Therefore, even if the cooling target temperature of the cold water is relatively low, the cold water can be cooled to the target temperature while preventing the water in the heat exchanger 4 from freezing.

According to the cold water production system 1 of the present embodiment, the brine supply path 10 from the chiller 3 to the heat exchanger 4 and the brine discharge path 11 from the heat exchanger 4 to the brine tank 2 are connected by a bypass path 5. A brine valve 6 composed of a three-way valve is provided at the confluence of the brine discharge path 11 and the bypass path 5. Then, the brine valve 6 can adjust the distribution ratio of returning the brine from the chiller 3 to the brine tank 2 via the heat exchanger 4 or returning to the brine tank 2 via the bypass path 5. As a result, the flow rate of brine passed through the heat exchanger 4 can be adjusted accurately while maintaining the amount of brine circulating to the chiller 3, so that cold water at a desired temperature is produced while preventing the water in the heat exchanger 4 from freezing. be able to.

Moreover, since the brine valve 6 is composed of a three-way valve provided at the connection portion between the brine discharge path 11 and the bypass path 5, not only the flow rate of brine supply to the heat exchanger 4 can be adjusted, but also desired. Sometimes it is possible to cut off the supply of brine to the heat exchanger 4. Therefore, after cooling the cold water to the target temperature, the supply of brine to the heat exchanger 4 can be reliably cut off to prevent further cooling of the cold water (and thus freezing of water in the heat exchanger 4). it can. Further, even if it is desired to circulate the brine in the brine tank 2 to the chiller 3 to cool it to the target brine temperature after cooling the cold water to the target temperature, the bypass is performed while cutting off the supply of the brine to the heat exchanger 4. Brine can be circulated to the chiller 3 through the passage 5 to prevent unnecessary cooling of cold water (and thus freezing of water in the heat exchanger 4).

By the way, it is preferable to control the rotation speed of the chilled water pump 15 so that the pressure of water in the heat exchanger 4 becomes higher than the pressure of the brine during the operation of the pumps 12 and 15. Specifically, the controller monitors the detection pressures of the brine pressure sensor 17 and the chilled water pressure sensor 18, and the detected pressure of the chilled water pressure sensor 18 is higher than the detected pressure of the brine pressure sensor 17 (or higher than a predetermined value). ), The rotation speed of the chilled water pump 15 is controlled by the inverter. The brine pump 12 may continue to operate at a predetermined rotation speed (steady rotation speed).

By controlling the rotation speed of the chilled water pump 15 to make the pressure of water in the heat exchanger 4 higher than the pressure of the brine, even if the heat exchanger 4 is damaged, the brine leaks to the cold water side. It can be prevented and safety can be increased. Since the viscosity (and thus the pressure) of brine changes with temperature, it is possible to monitor each pressure of brine and water for reliable control. Moreover, in consideration of the pressure loss in the heat exchanger 4, each pressure is monitored at the place where the brine pressure is high and the place where the water pressure is low, so that in the unlikely event that the heat exchanger 4 is damaged. However, it is possible to surely prevent the brine from leaking to the cold water side and enhance the safety. That is, in the flow path on the brine side of the heat exchanger 4, the inlet side has a higher pressure than the outlet side, and in the flow path on the water side of the heat exchanger 4, the outlet side has a lower pressure than the inlet side. By monitoring and controlling the pressure at the increased location (the pressure on the brine inlet side and the chilled water outlet side of the heat exchanger 4), even if the heat exchanger 4 is damaged, the brine leaks to the cold water side. Can be reliably prevented.

During the operation of each of the pumps 12 and 15, as described below, if the predetermined transition condition is satisfied, the operation shifts to the energy-saving operation, and if the predetermined return condition is satisfied, the normal operation is shifted (return from the energy-saving operation). Good.

FIG. 2 is a flowchart showing a transition process to the energy-saving operation, and FIG. 3 is a flowchart showing a return process from the energy-saving operation.

Now, both pumps 12 and 15 are operated to circulate brine and water in the heat exchanger 4, and the water temperature on the outlet side of the heat exchanger 4 (detected temperature of the chilled water temperature sensor 16) is set to "target temperature + set value". It is assumed that the opening degree of the brine valve 6 is being adjusted so as to be. The target temperature is, for example, 1.0 ° C, and the set value is, for example, 0.5 ° C.

As shown in FIG. 2, when the water temperature on the outlet side of the heat exchanger 4 continues to be below the target temperature for the target temperature arrival confirmation time (for example, 5 seconds) (S21), the supply of brine to the heat exchanger 4 is opened by the brine valve 6. The brine valve 6 is fully closed to shut off the supply of brine to the heat exchanger 4 (S22).

Although not shown, when the opening of the brine valve 6 is adjusted within the range of the upper limit opening and the lower limit opening, even when the lower limit opening is kept below the predetermined opening for a predetermined time (for example, 15 minutes). The brine valve 6 may be fully closed to shut off the supply of brine to the heat exchanger 4 and the chiller 3 may be stopped. As a result, it is possible to prevent unnecessary continuation of operation (not to enter energy-saving operation) due to balancing with the minimum load (heat dissipation and pump heat input) of the cold water side equipment when the opening degree of the brine valve 6 is small. Can be done.

In any case, when the brine pump 6 is fully closed for the brine pump stop determination time (for example, 300 seconds) (S23), the chiller 3 is stopped (S24). Then, after stopping the chiller 3, the brine pump 12 is stopped (S25). After that, when the stop of the brine pump 12 continues for the chilled water pump stop determination time (for example, 30 seconds) (S26), it is preferable to reduce the rotation speed of the chilled water pump 15 to a predetermined energy-saving rotation speed (for example, 36 Hz) (S27).

In this way, the chilled water production system 1 shifts to the energy-saving operation in which the chiller 3 and the brine pump 12 are stopped and the rotation speed of the chilled water pump 15 is reduced. Power consumption can be reduced by stopping the chiller 3 and the brine pump 12 or lowering the operating frequency of the chilled water pump 15 while the brine valve 6 is fully closed. By continuing the operation of the chilled water pump 15 with the brine pump 12 stopped, even if the heat exchanger 4 is damaged, leakage of the brine to the cold water side is prevented and safety is improved. be able to. Moreover, by continuing the operation of the chilled water pump 15, the chilled water temperature sensor 16 can detect an increase in water temperature (generation of a cold heat load).

During such energy-saving operation, as shown in FIG. 3, the water temperature on the outlet side of the heat exchanger 4 continues to be "target temperature + chilled water pump return value (for example, 1 ° C.)" or more for the chilled water pump return determination time (for example, 15 seconds). Then (S31), the rotation speed of the chilled water pump 15 is returned to the steady rotation speed (for example, 48 Hz) (S32).

After that, the water temperature on the outlet side of the heat exchanger 4 becomes equal to or higher than the "target temperature + brine pump return value (for example, 1 ° C.)" (S33), and the operation of the cold water pump 15 at the steady rotation speed is the brine pump return determination time. If it continues (for example, 30 seconds) (S34), the brine pump 12 is started at a steady rotation speed (for example, 55 Hz) (S35).

After that, after waiting for the chiller activation waiting time (for example, 20 seconds) to elapse (S36), the chiller is activated (S37). Then, the opening degree adjustment control of the brine valve 6 based on the water temperature on the outlet side of the heat exchanger 4 may be restarted (S38). That is, the operation shifts to the normal operation in which the opening degree of the brine valve 6 is adjusted so that the detection temperature of the chilled water temperature sensor 16 is set to "target temperature + set value".

The cold water production system 1 of the present invention is not limited to the configuration (including control) of the above embodiment, and can be appropriately changed. In particular, water is cooled by heat exchange between (a) a brine tank 2 for storing brine, (b) a chiller 3 for cooling the brine from the brine tank 2, and (c) the brine cooled by the chiller 3. Heat exchanger 4 to be used, (d) a brine pump 12 that supplies brine from the brine tank 2 to the heat exchanger 4 via the chiller 3, and (e) a brine supply path 10 from the chiller 3 to the heat exchanger 4. , The bypass path 5 connecting the brine discharge path 11 from the heat exchanger 4 to the brine tank 2, and (f) the confluence of the brine discharge path 11 and the bypass path 5, or the brine supply path 10 and the bypass path 5. If it is composed of a three-way valve provided at the branch portion of the above, and is provided with a brine valve 6 capable of shutting off the supply of brine to the heat exchanger 4 and adjusting the supply flow rate of brine to the heat exchanger 4. Other configurations can be changed as appropriate.

Further, (g) the brine is passed through the heat exchanger 4 by the brine pump 12 and water is passed through the cold water pump 15, so that the pressure of the water in the heat exchanger 4 becomes higher than the pressure of the brine. , The opening degree of the brine valve 6 is adjusted so as to control the rotation speed of the cold water pump 15 and / or (h) the water temperature on the outlet side of the heat exchanger 4 to be the set temperature, and the heat generated by the brine valve 6 is adjusted. Regarding the supply opening degree of the brine to the exchanger 4, the present invention is not limited to the above embodiment as long as the brine pump 12 is stopped when the fully closed state is continued for the brine pump stop determination time.

For example, in the above embodiment, the brine valve 6 composed of a three-way valve is provided at the confluence of the brine discharge path 11 and the bypass path 5, but may be provided at the branch portion between the brine supply path 10 and the bypass path 5. ..

Further, in the above embodiment, when adjusting the flow rate of brine passing through the heat exchanger 4 so that the water temperature on the outlet side of the heat exchanger 4 is set to the "set temperature", the "set temperature" is set to "target temperature + set value". However, this set value may be 0 ° C. in some cases. That is, the set temperature may be equal to the target temperature.

Further, in the above embodiment, the water in the cold water tank 7 is circulated with the heat exchanger 4, but the water supply / drainage system for the heat exchanger 4 can be appropriately changed. For example, the installation of the cold water tank 7 may be omitted, the water from the water supply source may be passed through the heat exchanger 4 to be cooled, and then the cold water may be supplied to the cold water demand location.

Further, in the above-described embodiment, as the brine tank 2, the chiller 3, and the heat exchanger 4, the existing (existing) configuration is used, and a bypass passage 5, a brine valve, and the like are added to the cold water production system of the above-described embodiment. 1 may be configured.

1 Cold water production system 2 Brine tank 3 Chiller 4 Heat exchanger 5 Bypass path 6 Brine valve 7 Cold water tank 8 Liquid level detector 9 Brine delivery path 10 Brine supply path 11 Brine discharge path 12 Brine pump 13 Brine inlet path 14 Cold water outlet path 15 Cold water pump 16 Cold water temperature sensor 17 Brine pressure sensor 18 Cold water pressure sensor

Claims (5)

A brine tank that stores brine and
With a chiller that cools the brine from this brine tank,
A heat exchanger that cools water by exchanging heat with the brine cooled by this chiller,
A brine pump that supplies brine from the brine tank to the heat exchanger via the chiller.
A bypass path connecting the brine supply path from the chiller to the heat exchanger and the brine discharge path from the heat exchanger to the brine tank.
It is composed of a three-way valve provided at a confluence of the brine discharge path and the bypass path or a branch portion of the brine supply path and the bypass path, and can cut off the supply of brine to the heat exchanger. A cold water production system characterized by having a brine valve that can adjust the flow rate of brine supplied to the heat exchanger. Brine is passed through the heat exchanger by the brine pump, and water is passed through the heat exchanger by the cold water pump.
The cold water production system according to claim 1, wherein the rotation speed of the cold water pump is controlled so that the pressure of water in the heat exchanger becomes higher than the pressure of brine. The pressure of the brine is monitored by a brine pressure sensor provided in the brine supply path after branching from the bypass path.
The chilled water production system according to claim 2, wherein the pressure of the water is monitored by a chilled water pressure sensor provided on the chilled water outlet side of the heat exchanger. The opening degree of the brine valve is adjusted so that the water temperature on the outlet side of the heat exchanger becomes the set temperature.
The second or third aspect of the present invention, wherein the brine pump is stopped when the brine pump stop determination time is continued in the fully closed state with respect to the supply opening degree of the brine to the heat exchanger by the brine valve. Cold water production system. The cold water production system according to claim 4, wherein the rotation speed of the cold water pump is reduced after the brine pump is stopped.

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