JP7362032B2 - cold water production system - Google Patents

Description

The present invention relates to a cold water production system that produces cold water 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) brine piping, a brine circulation pump, and a brine that connect the two. A cold water production system is known that includes equipment having a tank, and (iv) equipment having cold water piping connected to a heat exchanger, a cold water supply pump, and a cold water tank. According to this system, brine is cooled by a chiller (refrigeration machine, etc.), and water is cooled by the brine in a heat exchanger to produce cold water.

When producing chilled water at a relatively low temperature (for example, 2.5° C. or lower) using this type of chilled water production system, it is necessary to produce chilled water at a desired temperature while preventing water from freezing in the heat exchanger. For example, it is conceivable to provide a flow rate adjustment valve in the brine piping and adjust the opening degree of the valve (in other words, the flow rate of brine supplied to the heat exchanger) based on the water temperature on the outlet side of the heat exchanger.

However, for example, if you want to take out the water temperature at the outlet side of the heat exchanger at 1°C, if you control the valve to aim for the target value of 1°C, a certain control range will occur with respect to the target value, so the water temperature in the heat exchanger will be may freeze. If a temperature (eg, 1.5°C) higher than the target temperature (eg, 1°C) is set and controlled in an attempt to prevent this, the water temperature on the outlet side of the heat exchanger cannot be lowered to the target temperature.

JP-A-4-143570 (Claims)

The problem to be solved by the present invention is to provide a cold water production system that can cool water to a target temperature while preventing water from freezing in a heat exchanger.

The present invention has been made to solve the above problem, and the invention according to claim 1 includes: a brine tank for storing brine; a chiller for cooling brine from the brine tank; a heat exchanger that cools the water circulated between the cold water tank and the cold water tank by heat exchange with brine, and the chilled water production system cools the water to a target temperature with the heat exchanger , the heat exchanger a brine valve that adjusts the flow rate of brine passed through the heat exchanger, and a control means that controls the brine valve based on the water temperature on the outlet side of the heat exchanger, and the control means controls the brine flow rate within a range that does not fall below a preset lower limit opening degree. While supplying brine to the heat exchanger, the opening degree of the brine valve is adjusted so that the outlet side water temperature is "target temperature + set value", and the target temperature is a temperature exceeding 0 ° C. In addition, the control means determines whether the outlet side water temperature becomes below the target temperature, whether the outlet side water temperature continues to be below the target temperature for the target temperature attainment confirmation time, or whether the lower limit opening degree is The cold water production system is characterized in that when the opening degree continues to be below a predetermined degree for a predetermined period of time, the brine valve shuts off the supply of brine to the heat exchanger .

According to the invention described in claim 1, in a cold water production system that produces cold water by cooling water in a heat exchanger using brine cooled by a chiller, the brine valve is controlled based on the water temperature on the outlet side of the heat exchanger. , the brine flow rate through the heat exchanger can be adjusted. By adjusting the brine flow rate while monitoring the water temperature on the outlet side of the heat exchanger, cold water at a desired temperature can be produced while preventing water from freezing in the heat exchanger. At that time, by controlling the brine valve so that the water temperature on the outlet side of the heat exchanger is not the target temperature but a temperature higher than the target temperature, even if the target temperature is around 0℃, the Can prevent water from freezing. On the other hand, by supplying brine to the heat exchanger within a range that does not fall below the preset lower limit opening , brine can continue to flow into the heat exchanger as needed, cooling the water to the target temperature. be able to.
According to the invention described in claim 1, whether the water temperature on the outlet side of the heat exchanger becomes equal to or less than the target temperature, or the water temperature on the outlet side continues to be equal to or less than the target temperature for the target temperature attainment confirmation time, or the lower limit opening degree is determined by the predetermined opening degree. If the following conditions continue for a predetermined period of time, the brine valve can cut off the supply of brine to the heat exchanger and stop cooling the water. This makes it possible to cool the water as desired while preventing the water from freezing.

In the invention according to claim 2, a brine supply path from the chiller to the heat exchanger and a brine discharge path from the heat exchanger to the brine tank are connected by a bypass path, and the brine valve Claim characterized in that the distribution ratio of whether the brine from the chiller is returned to the brine tank via the heat exchanger or the brine tank via the bypass path is adjusted . 1. The cold water production system according to 1.

According to the invention described in claim 2, the brine supply path and the brine discharge path to the heat exchanger are connected by a bypass path, and the brine from the chiller is transferred to the heat exchanger by the brine valve serving as the brine flow rate adjusting means. It is possible to adjust the distribution ratio of whether the water is returned to the brine tank via the vessel or via the bypass path. This kind of distribution control makes it possible to accurately adjust the flow rate of brine passing through the heat exchanger while maintaining the amount of brine circulating to the chiller, making it possible to produce chilled water at the desired temperature while preventing water from freezing in the heat exchanger. can do.

In the invention according to claim 3, the brine valve consisting of a three-way valve is provided at a confluence of the brine discharge path and the bypass path, or a branching portion of the brine supply path and the bypass path, and 3. The cold water production system according to claim 2, wherein the opening degree of the brine valve is adjusted within a range that does not fall below a lower limit opening degree for supplying brine to the heat exchanger by the valve.

According to the invention described in claim 3, by using a three-way valve as the brine valve, the flow rate of brine passing through the heat exchanger can be adjusted with a simple configuration and control while maintaining the amount of brine circulation to the chiller. I can do it. Furthermore, the opening degree of the brine valve for supplying brine to the heat exchanger by the brine valve can be adjusted within a range that does not fall below the lower limit opening degree. Therefore, in order to prevent water from freezing in the heat exchanger, even if a temperature higher than the target temperature is set and controlled, brine can continue to flow through the heat exchanger as needed, and the water can reach the target temperature. cooling can be achieved.

In the invention according to claim 4, the opening of the brine valve is adjusted within a range of an upper limit opening and a lower limit opening, the upper limit opening and the lower limit opening are changeable, and the upper opening The process from closing to fully opening is divided into multiple steps, and a lower limit opening is assigned corresponding to one or more steps regarding the upper limit opening. 4. The cold water production system according to claim 3, wherein the cold water production system is set to a relatively large size.

According to the fourth aspect of the invention, the opening degree of the brine valve is adjusted within the range of the upper limit opening degree and the lower limit opening degree. By setting the lower limit opening degree according to the upper limit opening degree, brine can continue to flow into the heat exchanger as needed, and water can be cooled.

Furthermore, in the invention as set forth in claim 5, brine is passed through the heat exchanger by a brine pump, and water is passed by a cold water pump, and the control means is configured to control the outlet side water temperature to be equal to or lower than a target temperature. If the target temperature attainment confirmation time continues, the brine valve is closed to cut off brine supply to the heat exchanger, and then the chiller and the brine pump are stopped. The cold water production system according to any one of the items.

The invention according to claim 6 is the cold water production system according to claim 5, characterized in that the rotation speed of the cold water pump is lowered after the brine pump is stopped.

According to the cold water production system of the present invention, water can be cooled to a target temperature while preventing water from freezing in a heat exchanger.

1 is a schematic diagram showing a cold water production system according to an embodiment of the present invention. It is a schematic diagram showing a combination of an upper limit opening degree and a lower limit opening degree, and is shown with a part omitted. 7 is a flowchart illustrating an example of step-up determination processing. 7 is a flowchart illustrating an example of step-down determination processing.

Hereinafter, specific embodiments of the present invention will be described in detail based on the drawings.
FIG. 1 is a schematic diagram showing a cold water production system 1 according to an embodiment of the present invention.

The cold water production system 1 of this 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. It includes a heat exchanger 4 and a cold water tank 5 in which water is circulated between the heat exchanger 4 and the heat exchanger 4.

The brine tank 2 is a container that stores brine, and in this embodiment, the inside thereof is open to atmospheric pressure. The brine tank 2 is provided with a liquid level detector 6, and brine is stored up to a set liquid level. The type of brine is not particularly limited, but when using cold water produced by heat exchange with brine to cool food, food additives should be added to ensure safety in the event that the brine leaks due to damage to the heat exchanger 4. It is preferred to use a brine (eg propylene glycol) which is also acceptable as a solvent.

The chiller 3 includes a refrigerator (not shown). In this embodiment, the refrigerator is a vapor compression type refrigerator. In this case, the refrigerator is configured by sequentially connecting a compressor, a condenser, an expansion valve, and an evaporator in an annular manner. The compressor compresses the refrigerant into a high-temperature, high-pressure gas. The condenser condenses and liquefies the refrigerant from the compressor. The expansion valve reduces the pressure and temperature of the refrigerant by passing the refrigerant from the condenser. The evaporator then evaporates the refrigerant from the expansion valve. In the evaporator, the brine from the brine tank 2 and the refrigerant of the refrigerator can be heat exchanged 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 to enable heat exchange between brine and water without mixing them. Although the structure of the heat exchanger 4 is not particularly limited, it may be a plate heat exchanger, for example.

Brine is supplied from the brine tank 2 to the chiller 3 (more specifically, the evaporator of the refrigerator) via a brine delivery path 7. The brine cooled by the chiller 3 can be supplied to the heat exchanger 4 via a brine supply path 8. The brine after heat exchange in the heat exchanger 4 is returned to the brine tank 2 via the brine discharge path 9. A brine pump 10 is provided in the brine delivery path 7, and by operating this brine pump 10, the brine in the brine tank 2 can be circulated between the brine tank 2 and the heat exchanger 4 via the chiller 3. be done.

A brine supply path 8 from the chiller 3 to the heat exchanger 4 and a brine discharge path 9 from the heat exchanger 4 to the brine tank 2 are connected by a bypass path 11. A brine valve 12 consisting of a three-way valve is provided at the confluence of the brine discharge path 9 and the bypass path 11. By controlling this brine valve 12, the distribution ratio of whether the brine from the chiller 3 is returned to the brine tank 2 via the heat exchanger 4 or returned to the brine tank 2 via the bypass path 11 is adjusted. I can do it. Note that the brine pump 10 may be built into the chiller 3 depending on the case.

The cold water tank 5 is a container that stores water, and in this embodiment, the inside thereof is open to atmospheric pressure. The cold water tank 5 is provided with a water level detector (not shown). By controlling the water supply to the cold water tank 5 based on the detection signal of the water level detector, the water level in the cold water tank 5 is maintained at the set water level.

Water is supplied from the cold water tank 5 to the heat exchanger 4 via a cold water inlet path 13 . The water cooled by the heat exchanger 4 is returned to the cold water tank 5 via the cold water outlet path 14. A cold water pump 15 is provided in the cold water inlet passage 13, and by operating the cold water pump 15, water in the cold water tank 5 can be circulated between the cold water tank 5 and the heat exchanger 4.

The cold water in the cold water tank 5 is supplied to and used at a place that requires cold water (for example, a food machine), if desired. After being used at a cold water demand point, the water is either thrown away or returned to the cold water tank 5. Even in the case of the former (disposable cold water), water can be appropriately supplied into the cold water tank 5 as described above, so the water level in the cold water tank 5 is maintained at the set water level. In the case of the latter (chilled water circulation), the cold water in the cold water tank 5 can be circulated to and from the cold water demand location, and is returned to the cold water tank 5 after cooling the objects to be cooled at the cold heat demand location.

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. In this embodiment, the brine temperature sensor is built into the chiller 3 and detects the brine temperature on the brine outlet side of the chiller 3. On the other hand, the cold water temperature sensor is provided in the cold water outlet path 14 in this embodiment, and detects the water temperature on the cold water outlet side of the heat exchanger 4.

Next, an example of operation of the cold water production system 1 of this embodiment will be explained. The operation described below is automatically performed by a controller (not shown). In other words, the controller is connected to the chiller 3, brine valve 12, brine pump 10, cold water pump 15, as well as a brine temperature sensor (not shown), a cold water temperature sensor 16, etc., and detects the detection signals of these sensors and the elapsed time. Based on the above, the chiller 3, brine valve 12, pumps 10 and 15, etc. are controlled.

With the start of operation of the cold water production system 1, each pump 10, 15 and chiller 3 are activated. By operating the brine pump 10, the brine in the brine tank 2 is circulated between the chiller 3 and the heat exchanger 4. By operating the cold water pump 15, water in the cold water tank 5 is circulated between it and the heat exchanger 4. Brine is cooled in the chiller 3, and water is cooled in the heat exchanger 4 by the cooled brine. As described above, the cold water in the cold water tank 5 or its cold energy can be used at locations where cold water is required. After that, each pump 10, 15 basically continues to operate.

While the brine is being circulated by the brine pump 10, the brine can be cooled by the chiller 3. In this embodiment, the capacity of the chiller 3 is controlled so that the brine temperature on the outlet side is the brine target temperature (for example, −2° C.). Specifically, the compressor motor is controlled by an inverter so as to maintain the temperature detected by 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 a target temperature range including the brine target temperature, and an increase/decrease value of the inverter frequency is set according to each temperature range. Then, it monitors which temperature range it is in at each set time, and if it is in the target temperature range, it maintains the current frequency, but if it is in a temperature range lower than the target temperature range, it lowers the frequency, and if it is in the high temperature range, it maintains the current frequency. If the temperature is within the range, control is performed to increase the frequency.

While each pump 10, 15 is in operation, the brine valve 12 is controlled so that the water temperature on the outlet side of the heat exchanger 4 is brought to the set temperature. Specifically, the brine valve 12 is controlled to maintain the temperature detected by the chilled water temperature sensor 16 at the set temperature, and the brine from the chiller 3 is returned to the brine tank 2 via the heat exchanger 4, or The distribution ratio of returning to the brine tank 2 via the bypass path 11 is adjusted. Thereby, the flow rate of brine passed through the heat exchanger 4 can be adjusted.

Even if a temperature exceeding 0° C. is set as the cooling target temperature of the cold water, the actual cold water temperature (chilled water temperature after being cooled by the heat exchanger 4) fluctuates up and down somewhat around the target temperature. Therefore, when the cooling target temperature of the cold water is relatively low (for example, 3° C. or lower), there remains a risk that the water may freeze in the heat exchanger 4. In order to prevent this, in this embodiment, the opening degree of the brine valve 12 is adjusted (preferably by PID control )do.

Note that the target temperature is set at a temperature higher than 0°C, and typically set at 3°C or lower. In this embodiment, the target temperature is, for example, 1.0°C. Further, the set value is set to a positive value of less than 1°C, preferably less than 0.5°C. In this embodiment, the set value is, for example, 0.5°C.

When starting brine supply from a state where brine supply to the heat exchanger 4 is stopped, the brine supply to the heat exchanger 4 is started within a range that does not exceed a preset upper limit flow rate. In this embodiment, an upper limit opening degree is set for the opening degree for supplying brine to the heat exchanger 4 by the brine valve 12, and the opening degree of the brine valve 12 is adjusted within a range that does not exceed the upper limit opening degree. . The upper limit opening degree can be changed depending on the situation.

Further, in this embodiment, the lower limit opening degree is also set according to the upper limit opening degree, and the opening degree of the brine valve 12 is adjusted within a range that does not fall below the lower limit opening degree. The lower limit opening degree can be changed depending on the situation. Note that the upper limit opening degree (upper limit flow rate) and the lower limit opening degree (lower limit flow rate) are determined through experiments or the like so that the desired effect can be achieved.

Thus, in this embodiment, the opening degree of the brine valve 12 is adjusted within the range of the upper limit opening degree and the lower limit opening degree. The upper limit opening degree and the lower limit opening degree can be changed depending on the situation. This will be explained in more detail below.

FIG. 2 is a schematic diagram showing a combination of an upper limit opening degree and a lower limit opening degree, with some parts omitted. As shown in this figure, the upper limit opening of the brine supply to the heat exchanger 4 by the brine valve 12 is divided into multiple steps (stages) from fully closed (opening 0%) to fully open (opening 100%). It is divided.

More specifically, step 0 is a fully closed state (opening degree 0%), step N is a fully open state (opening degree 100%), and the whole is divided into "N+1" equal parts, step 0, step 1, step 2. , . . . is divided up to step N. Further, an upper limit opening degree is set for each step such that the upper limit opening degree increases as the step increases. That is, if the upper limit opening of step 0 is U0 (=0), the upper limit opening of step 1 is U1, the upper limit opening of step 2 is U2, ... the upper limit opening of step N is UN (=100), The relationship is U0<U1<U2<...<UN. At this time, it is preferable that the upper limit opening degree is set to increase by a predetermined opening degree each time the step is increased.

The lower limit opening degree is set as follows. First, the lower limit opening degree of step 0 is set to 0%, the same as the upper limit opening degree. Further, the lower limit opening LN of step N is set below the upper limit opening UN (100%), preferably below half open (50%), and in this embodiment is set to 30%, for example. The lower limit opening degree of each step from step 1 to step N-1 is set to be less than the upper limit opening degree of that step. At this time, the lower limit opening degree may be 0, but in at least one or more of the steps, the lower limit opening degree is set to an opening degree exceeding 0.

Further, a lower limit opening degree is assigned corresponding to one or more steps regarding the upper limit opening degree, and the assigned lower limit opening degree is set to be larger as the upper limit opening degree becomes larger. For example, the lower limit opening degrees L0 to L4 of steps 0 to 4 are set to 0, the lower limit opening degree L5 of step 5 is set to a value exceeding 0, and the lower limit opening degree L6 of step 6 is set to the lower limit opening degree L5 of step 5. The lower limit opening degree L7 to LN after step 7 is set to a predetermined value larger than the lower limit opening degree L6 in step 6. That is, in adjacent steps, the lower limit opening degree may be the same or different, but overall, the lower limit opening degree is set to increase as the upper limit opening degree increases.

As described above, when the cold water production system 1 starts operating, the brine pump 10 and the cold water pump 15 are activated. Then, the opening degree of the brine valve 12 is adjusted so that the temperature detected by the chilled water temperature sensor 16 becomes "target temperature + set value". When opening from the fully closed state, first start from step 1 in FIG. That is, first, the opening degree of the brine valve 12 is adjusted within the range of the upper limit opening degree and the lower limit opening degree in step 1. Then, depending on the situation, the brine valve 12 is opened so as to maintain the detected temperature of the chilled water temperature sensor 16 at "target temperature + set value" while changing the step (in other words, the upper limit opening degree or the lower limit opening degree). Adjust the degree.

FIG. 3 is a flowchart illustrating an example of step-up determination processing, and FIG. 4 is a flowchart illustrating an example of step-down determination processing.

The opening degree of brine supply to the heat exchanger 4 by the brine valve 12 is changed from the fully closed state in step 0 (that is, the state in which brine supply to the heat exchanger 4 is cut off) to the opening degree in step 1. After opening, the step-up determination process in FIG. 3 and the step-down determination process in FIG. 4 are executed in parallel. Whether or not to increase the step is determined based on the step-up determination process shown in FIG. 3, and whether or not to decrease the step is determined based on the step-down determination process shown in FIG.

In the step-up determination process of FIG. 3, the outlet side water temperature of the heat exchanger 4 (the temperature detected by the cold water temperature sensor 16) is equal to or higher than the "target temperature + set value" (S11), and the upper limit at the current operation step is determined. When the opening degree continues for the step-up determination time (S12), the step is increased by one step (S13). For example, assuming that the operation is currently in step 1, the water temperature on the outlet side of the heat exchanger 4 is equal to or higher than "target temperature + set value", and the upper limit opening degree U1 of step 1, which is the current operation step, is stepped up. When the determination time (for example, 5 seconds) continues, the process moves to step 2 and the upper limit opening degree is increased. In this way, the upper limit opening degree (and thus the flow rate at which brine can be supplied to the heat exchanger 4) can be increased. Although it depends on the step, as the upper limit opening increases, the lower limit opening can also increase.

In the step-down determination process of FIG. 4, when the brine valve 12 is fully closed (S21) regarding the opening degree of supplying brine to the heat exchanger 4 by the brine valve 12 while executing step 1 or more, the process moves to step 0. (S22). As mentioned above, since a lower limit opening degree is set for the brine valve 12, a transition to step 0 may occur in steps where 0 is set as the lower limit opening degree (for example, steps 0 to 4). Become. Alternatively, if the brine valve 12 is fully closed due to the cold water reaching the target temperature, etc., the process will proceed to step 0.

On the other hand, even if the brine valve 12 is not fully closed, while the steps (steps X+1 to N) exceeding the low temperature transition step ” If the step-down determination time (for example, 2 seconds) continues (S23), the process moves to low temperature transition step X (S24). Note that the predetermined value is set to be less than the set value, preferably less than half of the set value. For example, in this embodiment, for a target temperature of 1.0°C, a set value of 0.5°C and a predetermined value of 0.1°C are set.

Through the step-down determination process, after the brine valve 12 is fully closed and the process moves to step 0, the control can be restarted from step 1 at a predetermined timing. For example, if the temperature detected by the chilled water temperature sensor 16 is monitored and this temperature (that is, the water temperature on the outlet side of the heat exchanger 4) exceeds the "target temperature + set value" (or if this state continues for the step-up determination period) (e.g.), the control can be restarted from step 1.

By the way, during the series of controls described above, if the water temperature on the outlet side of the heat exchanger 4 becomes equal to or lower than the target temperature, the brine valve 12 is fully closed to cut off the supply of brine to the heat exchanger 4. Furthermore, even if the water temperature on the outlet side of the heat exchanger 4 does not fall below the target temperature, if the lower limit opening remains below the predetermined opening (for example, the state below step 6) for a predetermined period of time (for example, 15 minutes), The brine valve 12 may be completely closed to cut off the supply of brine to the heat exchanger 4. Thereby, it is possible to prevent wasteful continuation of operation (not entering into the energy saving control described later) due to balance with the minimum load (heat radiation and pump heat input) of the chilled water side equipment.

Note that the chiller 3 and each pump 10, 15 continue to operate even after the brine valve 12 is fully closed, except when performing energy saving control to be described later. Therefore, the brine can be cooled to below the brine target temperature.

During the series of controls described above, the following energy saving control may be performed. That is, if the water temperature on the outlet side of the heat exchanger 4 continues to be below the target temperature for the target temperature attainment confirmation period, the brine valve 12 is closed to cut off the brine supply to the heat exchanger 4, and then the chiller 3 is stopped and the brine pump is turned off. 10 may be stopped. Further, after stopping the brine pump 10, the rotation speed of the cold water pump 15 may be lowered to a predetermined value. After that, if the water temperature on the outlet side of the heat exchanger 4 continues to be equal to or higher than the "target temperature + cold water pump return value" for the cold water pump return determination period, the rotation speed of the cold water pump 15 is returned to the steady rotation speed, and if a predetermined condition is satisfied, After starting the brine pump 10 and starting the chiller 3, the opening degree adjustment of the brine valve 12 may be resumed. In this case, the process will start from step 1 in FIG. With such control, it is possible to stop the brine pump 10 and the chiller 3 or to lower the rotational speed of the cold water pump 15 depending on the situation, and it is possible to reduce power consumption.

According to the cold water production system 1 of this embodiment, in the cold water production system 1 which produces chilled water by cooling water in the heat exchanger 4 with brine cooled by the chiller 3, the brine supply path 8 to the heat exchanger 4 and the brine The discharge passage 9 was connected to the discharge passage 9 by a bypass passage 11, and a brine valve 12 consisting of a three-way valve was provided at the junction of the brine discharge passage 9 and the bypass passage 11. Then, by controlling the brine valve 12 based on the water temperature on the outlet side of the heat exchanger 4, the brine from the chiller 3 is returned to the brine tank 2 via the heat exchanger 4, or is returned to the brine tank via the bypass path 11. You can adjust the distribution ratio to return to 2. With such distribution control, the flow rate of brine passing through the heat exchanger 4 can be adjusted accurately while maintaining the amount of brine circulating to the chiller 3, so that the desired temperature can be maintained while preventing water from freezing in the heat exchanger 4. Cold water can be produced.

In addition, freezing of water in the heat exchanger 4 is prevented by adjusting the opening degree of the brine valve 12 within a range that does not exceed the upper limit opening degree for supplying brine to the heat exchanger 4 by the brine valve 12. can do. In particular, when starting brine supply from the stopped state of brine supply to the heat exchanger 4 (during which the brine can be cooled down to below the brine target temperature as described above), heat exchange is performed within a range not exceeding the upper limit opening degree. Since the supply of brine to the vessel 4 is started, a sudden drop in cold water temperature can be prevented, and freezing of water in the heat exchanger 4 can be prevented. Further, even if the temperature of the brine is lower than expected, freezing of water in the heat exchanger 4 can be prevented.

In addition, while adjusting the opening degree of the brine valve 12 based on the outlet side water temperature of the heat exchanger 4, if the outlet side water temperature is equal to or higher than "target temperature + set value", the upper limit opening degree in the current operation step is stepped up for the judgment time. If it continues, the step (in other words, the upper limit opening degree) is increased. Reaching the upper limit opening is basically a situation in which it is necessary to increase the flow rate of brine supplied to the heat exchanger 4 (that is, increasing the cooling capacity), but not only does it require the upper limit opening, By confirming the continuation of the step-up determination time, it is possible to prevent the influence of water temperature fluctuations and the like, and to prevent cold water temperature undershoot due to excessive opening of the brine valve 12. Further, even if an undershoot occurs, the opening degree (cooling capacity) of the brine valve 12 is maintained at the upper limit value, so that expansion of the undershoot can be suppressed. Furthermore, by confirming that the water temperature on the outlet side of the heat exchanger 4 is higher than the target temperature, rather than simply reaching the upper limit opening, it is possible to prevent the upper limit opening from being raised excessively.

By the way, when the target temperature for cooling water in the heat exchanger 4 is a relatively low temperature around 0°C (for example, 1°C), the temperature of the cold water fluctuates slightly around the target temperature, so the brine is adjusted to the target temperature. If the opening degree of the valve 12 is adjusted, water in the heat exchanger 4 may freeze. However, in this embodiment, since the water temperature on the outlet side of the heat exchanger 4 is controlled to be "target temperature + set value", freezing of the water in the heat exchanger 4 can be prevented. On the other hand, if the cold water is controlled to be "target temperature + set value", it is not possible to bring the cold water to the target temperature. However, in this embodiment, the brine supply opening degree to the heat exchanger 4 by the brine valve 12 By setting a lower limit on the opening, cooling to the target temperature was made possible. That is, by supplying brine to the heat exchanger 4 within a range that does not fall below the preset lower limit opening degree, brine can be continued to flow into the heat exchanger 4 as needed (in other words, depending on the step), It is possible to gradually cool water to the target temperature.

The cold water production system 1 of the present invention is not limited to the configuration (including control) of the embodiment described above, and can be modified as appropriate. In particular, the cold water includes a brine tank 2 that stores brine, a chiller 3 that cools the brine from the brine tank 2, and a heat exchanger 4 that cools water by heat exchange with the brine cooled by the chiller 3. The manufacturing system 1 includes a brine flow rate adjustment means (for example, a brine valve 12) that adjusts the flow rate of brine passed through the heat exchanger 4, and a control means that controls the brine flow rate adjustment means based on the water temperature on the outlet side of the heat exchanger 4. The control means controls the brine flow rate adjustment means so that the outlet side water temperature becomes "target temperature + set value" while supplying brine to the heat exchanger 4 within a range that does not fall below a preset lower limit flow rate. If so, the other configurations can be changed as appropriate.

For example, in the embodiment described above, the brine valve 12 consisting of a three-way valve was provided at the confluence of the brine discharge path 9 and the bypass path 11, but it may be provided at the branch point of the brine supply path 8 and the bypass path 11. . In addition, the brine flow rate adjusting means for adjusting the flow rate of brine passing through the heat exchanger 4 is not limited to the brine valve 12 which is a three-way valve, but includes, for example, the brine supply path 8 (and/or brine discharge path 9) and the bypass path 11. Electrically operated valves may be provided for each of the valves to adjust their opening degrees. Furthermore, in some cases, the installation of the bypass path 11 may be omitted, and the opening degree of the electric valve provided in the brine supply path 8 (or brine discharge path 9) may be adjusted, or the brine pump 10 may be controlled by an inverter. .

Further, in the embodiment described above, the brine in the brine tank 2 was circulated so as to be returned to the brine tank 2 via the chiller 3 and the heat exchanger 4 (or the bypass path 11), but the following configuration was adopted. Good too. That is, while the brine in the brine tank 2 is circulated with the chiller 3, the brine in the brine tank 2 may be circulated with the heat exchanger 4 in a separate circulation path. Also in this case, the brine supply path 8 from the brine tank 2 to the heat exchanger 4 and the brine discharge path 9 from the heat exchanger 4 to the brine tank 2 are connected by a bypass path 11, and a brine valve consisting of a three-way valve is connected. 12, the flow rate of brine passing through the heat exchanger 4 may be adjusted.

Furthermore, in the embodiment described above, the water in the cold water tank 5 was circulated between the heat exchanger 4 and the water supply and drainage system for the heat exchanger 4, but the water supply and drainage system for the heat exchanger 4 can be changed as appropriate. For example, the installation of the cold water tank 5 may be omitted, and after water from the water supply source is passed through the heat exchanger 4 to be cooled, the cold water may be supplied to the cold water demand location.

Further, in the above embodiment, while using the existing (existing) configuration as the brine tank 2, chiller 3, and heat exchanger 4, a bypass passage 11, a brine valve 12, etc. are added to the chilled water production system of the above embodiment. 1 may be configured.

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

Claims (6)

A brine tank for storing brine,
A chiller that cools the brine from this brine tank,
A cold water production system comprising: a heat exchanger that cools water circulated between a cold water tank by heat exchange with brine cooled by the chiller , and wherein the heat exchanger cools the water to a target temperature. ,
a brine valve that adjusts the flow rate of brine passed through the heat exchanger;
and control means for controlling the brine valve based on the water temperature on the outlet side of the heat exchanger,
The control means controls the opening of the brine valve so that the outlet side water temperature becomes "target temperature + set value" while supplying brine to the heat exchanger within a range that does not fall below a preset lower limit opening. adjust the degree,
The target temperature is set to a temperature exceeding 0 °C and below 3 °C,
The control means is configured to determine whether the outlet side water temperature becomes equal to or less than the target temperature, or the outlet side water temperature continues to be equal to or less than the target temperature for a target temperature confirmation period, or the lower limit opening continues to be equal to or less than a predetermined opening for a predetermined time. Then, the brine valve shuts off the supply of brine to the heat exchanger.
A cold water production system characterized by: A brine supply path from the chiller to the heat exchanger and a brine discharge path from the heat exchanger to the brine tank are connected by a bypass path,
The brine valve adjusts the distribution ratio of returning brine from the chiller to the brine tank via the heat exchanger or returning to the brine tank via the bypass path.
The cold water production system according to claim 1, characterized in that: The brine valve, which is a three-way valve, is provided at a confluence between the brine discharge path and the bypass path, or at a branch between the brine supply path and the bypass path,
The cold water production system according to claim 2, wherein the opening degree of the brine valve is adjusted within a range that does not fall below a lower limit opening degree for supplying brine to the heat exchanger by the brine valve. The brine valve has an opening degree adjusted within a range of an upper limit opening degree and a lower limit opening degree,
The upper limit opening and lower limit opening can be changed,
Regarding the upper limit opening, the range from fully closed to fully open is divided into multiple steps.
A lower limit opening is assigned corresponding to one or more steps regarding the upper limit opening.
The chilled water production system according to claim 3, wherein the assigned lower limit opening degree is set larger as the upper limit opening degree becomes larger. Brine is passed through the heat exchanger by a brine pump, and water is passed by a cold water pump,
The control means is configured to close the brine valve to cut off brine supply to the heat exchanger, and then stop the chiller and stop the brine pump when the outlet side water temperature continues to be equal to or lower than the target temperature for a target temperature attainment confirmation time. stop
The cold water production system according to any one of claims 1 to 4, characterized in that:. After stopping the brine pump, reduce the rotation speed of the cold water pump.
The cold water production system according to claim 5, characterized in that :

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