Liquid circulation system

Abstract

The present invention provides a liquid circulation system capable of appropriately preventing or suppressing problems such as water or other liquids overflowing from a tank or running out. [Solution] A liquid circulation system SY comprises multiple open-type tanks 6a, 6b, multiple flow paths 7a, 7b and multiple pumps Pa, Pb that enable the circulation of liquid through these multiple tanks 6a, 6b, and a control means 8 capable of controlling the liquid flow rate of each of the multiple flow paths 7a, 7b. The control means 8 selects one of the multiple flow paths 7a, 7b as a reference flow path and detects the flow rate difference ΔQ of the liquid flow rates of the other flow paths 7b based on the liquid flow rate of this reference flow path 7a. When this flow rate difference ΔQ exceeds a predetermined value α, it performs primary control, which changes the liquid flow rate of the other flow paths 7b in order to reduce the flow rate difference ΔQ to a predetermined value α or less while maintaining the liquid flow rate of the reference flow path 7a at a constant level.

Description

Technical Field

[0001] The present invention relates to a liquid circulation system for circulating a liquid such as water between a plurality of open tanks.

Background Art

[0002] As a specific example of a liquid circulation system, there is, for example, an aquaponic system (see Patent Documents 1 to 3). In this aquaponic system, two open (non-closed) tanks are connected via two flow paths, and water can be circulated by operating a pump. Of the two tanks, one tank contains water containing nutrients generated by aquaculture, and the other tank contains clean water produced by hydroponic cultivation of plants using the water sent from the one tank, and this water is returned to the one tank. According to such a configuration, it is possible to efficiently produce aquatic products and agricultural products in these symbiotic environments.

[0003] However, in the above prior art, there was room for improvement as described below.

[0004] That is, when circulating water between two tanks, a flow rate difference may occur in the water flowing from one of the two tanks to the other and from the other to the one, respectively. If this state with the flow rate difference is left as it is, there is a risk that water will overflow in one of the two tanks and drought (depletion) will occur in the other. In this case, the system using the two tanks cannot be properly used for its original purpose (for example, an aquaponic system). As a means for preventing drought in the tank, a means of attaching a water replenishing device to the tank can be considered, but this causes waste of water resources used for water replenishment. The above-described problems can occur not only in aquaponic systems but also in other liquid circulation systems. s

Prior Art Documents

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-56277 [Patent Document 2] Patent No. 6150413 [Patent Document 3] Patent No. 6047749 [Overview of the project] [Problems that the invention aims to solve]

[0006] This invention was conceived under the circumstances described above, and its objective is to provide a liquid circulation system that can appropriately prevent or suppress problems such as water or other liquids overflowing from a tank or running out. [Means for solving the problem]

[0007] To solve the above problems, the present invention employs the following technical measures.

[0008] The liquid circulation system provided by the present invention comprises a plurality of open tanks capable of storing liquid, a plurality of flow paths that enable the circulation of the liquid between the plurality of tanks, a plurality of pumps provided in the plurality of flow paths, and control means capable of controlling the liquid flow rate of each of the plurality of flow paths, wherein the control means designates one of the plurality of flow paths as a reference flow path, and controls the liquid flow rate of this reference flow path. The system is characterized by detecting a flow rate difference ΔQ of the liquid flow rate of other flow paths based on a reference flow path, and when this flow rate difference ΔQ exceeds a predetermined value α, it performs primary control to change the liquid flow rate of the other flow path in order to reduce the flow rate difference ΔQ to or below the predetermined value α while maintaining the liquid flow rate of the reference flow path at a constant level.

[0009] This configuration yields the following effects: In other words, according to the primary control described above, the liquid flow rates in each of the multiple flow paths connecting multiple tanks are kept within a predetermined value α such that the flow rate difference ΔQ between them is within a predetermined value α. Therefore, it is possible to avoid the liquid circulation operation continuing while the flow rate difference ΔQ is large, and problems such as liquid overflowing from the tanks or running out can be appropriately prevented or suppressed. Furthermore, it is possible to simplify the system configuration by eliminating or reducing the need for, for example, a water replenishment device to prevent liquid depletion, and if a water replenishment device is provided, the amount of water replenished can be kept from being excessive, thus reducing the waste of water resources. For these reasons, the liquid circulation system according to the present invention is suitable for use as a component of, for example, an aquaponic system.

[0010] In the present invention, preferably, the plurality of tanks include first and second tanks for storing the liquid to be stored as a high-temperature liquid and a low-temperature liquid with a temperature difference, and the plurality of flow paths include first and second flow paths that can cause the liquid to flow from one of the first and second tanks to the other and from the other to the first, respectively, and the first and second flow paths are provided with heat exchangers that enable heat exchange between the liquids flowing through them.

[0011] With this configuration, heat exchange can occur between the liquids flowing through the first and second channels, thus saving energy when storing the liquids in the first and second tanks with a temperature difference, with one side being high temperature and the other low temperature.

[0012] In the present invention, preferably, the predetermined value α is a non-zero value, and when the flow rate difference ΔQ is less than or equal to the predetermined value α, the speed of the plurality of pumps is maintained so that the liquid flow rate of each of the plurality of flow paths remains constant.

[0013] With this configuration, even if a flow rate difference ΔQ occurs between the reference flow path and other flow paths, the speeds of the multiple pumps will not change if this flow rate difference ΔQ is a relatively small value less than or equal to a predetermined value α. Therefore, the speed control of the multiple pumps can be simplified. In addition, in this invention, unlike the above configuration, it is also possible to set the predetermined value α to zero. In this case, when a flow rate difference ΔQ occurs, control is performed to make this flow rate difference ΔQ zero, which is preferable for eliminating the flow rate difference ΔQ and maintaining a constant liquid storage amount in each of the multiple tanks.

[0014] In the present invention, preferably, if, during the execution of the primary control, the liquid flow rate of the other flow path is changed to a predetermined first limit, but the flow rate difference ΔQ does not decrease to a predetermined value α or less, the primary control is terminated, and then a secondary control is executed to change the liquid flow rate of the reference flow path in order to reduce the flow rate difference ΔQ to a predetermined value α or less, while keeping the liquid flow rate of the other flow path constant.

[0015] With this configuration, if, during the execution of primary control, the liquid flow rate in another channel is changed to a predetermined first limit, but the flow rate difference ΔQ does not decrease to a predetermined value α or less, the liquid flow rate in the other channel is prevented from being changed even further, thus appropriately preventing the liquid flow rate from becoming an inappropriate value. Furthermore, by primary control If the flow rate difference ΔQ cannot be kept below a predetermined value α, secondary control is initiated instead, and the liquid flow rate in the reference channel is changed, making it possible to accurately reduce the flow rate difference ΔQ. In secondary control, the liquid flow rates in the other channels are kept constant, making it easy to control the flow rate difference ΔQ between the reference channel and the other channels to be kept below a predetermined value α.

[0016] In the present invention, preferably, during the execution of the secondary control, even if the liquid flow rate in the reference flow path is changed to a predetermined second limit, when the flow rate difference ΔQ does not decrease to or below the predetermined value α, the operation of the plurality of pumps is configured to be stopped.

[0017] According to such a configuration, when the secondary control is executed and, even though the reference flow path is changed to a predetermined second limit, the flow rate difference ΔQ does not decrease to or below the predetermined value α, it is considered that some abnormality has occurred. In such a case, since the secondary control is aborted and the operation of the plurality of pumps is stopped, it is appropriately prevented that the liquid circulation system continues to operate in an abnormal state thereafter.

[0018] In the present invention, preferably, there is further provided liquid level detection means capable of detecting the liquid level of the liquid stored in each of the plurality of tanks, and when the difference in the liquid levels of the plurality of tanks becomes a predetermined value or more, control is executed to stop the inflow of liquid into the tank having the highest liquid level among the plurality of tanks or to reduce the inflow amount thereof.

[0019] According to such a configuration, when the liquid circulation system is operating, if the difference in the liquid levels of the liquid stored in the plurality of tanks becomes a predetermined value or more, it is considered that some abnormality has occurred. In this case, since control is executed to stop the inflow of liquid into the tank having the highest liquid level or to reduce the inflow amount thereof, it is possible to appropriately prevent the liquid from overflowing from the tank.

[0020] Other features and advantages of the present invention will become clearer from the following description of the embodiments of the invention with reference to the accompanying drawings.

Brief Description of the Drawings

[0021] [Figure 1] It is an explanatory diagram showing a schematic configuration of an example of the liquid circulation system according to the present invention. [Figure 2] It is a flowchart showing an example of an operation control procedure executed in the liquid circulation system shown in FIG. 1. [Figure 3] It is an explanatory diagram showing a schematic configuration of another example of the liquid circulation system according to the present invention. [Figure 4] It is an explanatory diagram showing a schematic configuration of another example of the liquid circulation system according to the present invention. [Figure 5] It is a flowchart showing a partial example of an operation control procedure executed in the liquid circulation system shown in FIG. 4.

Embodiments for Carrying Out the Invention

[0022] Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings.

[0023] The liquid circulation system SY shown in FIG. 1 is configured to be suitable for use in, for example, an aquaponic system, and includes open-type first and second tanks 6a and 6b capable of storing water, first and second flow paths 7a and 7b, flow-type or other types of liquid level detectors 10 provided in each of the first and second tanks 6a and 6b, a heat exchanger 11, and a control unit 8 (corresponding to an example of the control means referred to in the present invention). The liquid to be circulated in this liquid circulation system SY is water.

[0024] The first and second flow paths 7a and 7b are flow paths for circulating water between the first and second tanks 6a and 6b, are configured using appropriate piping members, and are provided with first and second pumps Pa and Pb having variable discharge flow rates. By operating these first and second pumps Pa and Pb, it is possible to make the water in the first and second tanks 6a and 6b flow and circulate in the directions indicated by arrows Na and Nb. The flow rates Q1 and Q2 of the water in each of the first and second flow paths 7a and 7b (the flow rate per unit time, corresponding to an example of the "liquid flow rate" referred to in the present invention) can be detected by the control unit 8 using the flow rate sensors 12 provided in those flow paths 7a and 7b. The liquid level (water surface level) of the water stored in the first and second tanks 6a and 6b can be detected by the control unit 8 using the liquid level detector 10.

[0025] The water stored in the first and second tanks 6a and 6b has different temperatures, with the water in the first tank 6a being relatively hotter and the water in the second tank 6b being relatively colder. More specifically, the water in the first tank 6a is used for aquaculture, such as for raising fish, and is controlled to a temperature suitable for aquaculture (e.g., in the 20s Celsius) using a heater 13 attached to the first tank 6a. The water in the second tank 6b is used for cultivating crops, and is controlled to a temperature suitable for cultivation (e.g., in the 10s Celsius) using a chiller 14 attached to the second tank 6b.

[0026] The heat exchanger 11 is a liquid-liquid heat exchanger installed across both the first and second flow paths 7a and 7b, and it facilitates heat exchange between the high-temperature water pumped from the first tank 6a and flowing through the first flow path 7a, and the low-temperature water pumped from the second tank 6b and flowing through the second flow path 7b. Therefore, the water flowing through the first flow path 7a decreases in temperature as it passes through the heat exchanger 11, and the water flowing through the second flow path 7b increases in temperature as it passes through the heat exchanger 11. This reduces the amount of water heated by the heater 13 and cooled by the chiller 14, thereby saving energy.

[0027] The control unit 8 is configured using a microcomputer or the like, and is connected to the control unit 8 by an operation unit 80 that allows the user to input various data to the control unit 8, a display unit 81 that can display various data, and a notification operation unit 82 that can perform notification actions that the user can perceive visually and / or aurally (e.g., lighting up an alarm lamp, generating voice messages or alarm sounds). This control unit 8 controls the operation of each part of the liquid circulation system SY, and in doing so, it controls the operation of the first and second pumps Pa and Pb to prevent water from overflowing or running out in the first and second tanks 6a and 6b. The details will be described later.

[0028] Next, an example of the operation control procedure for the aforementioned liquid circulation system SY will be explained with reference to the flowchart shown in Figure 2. Its function will also be explained.

[0029] First, when an operation to start water circulation is performed on the control unit 80, the operation of the first and second pumps Pa and Pb is started (S1, S2). Subsequently, the control unit 8 detects the flow rate difference ΔQ between the water flow rates Q1 and Q2 of the first and second flow paths 7a and 7b, and determines whether this flow rate difference ΔQ is less than or equal to a predetermined value α (S3). In this embodiment, the predetermined value α is a non-zero value. In this embodiment, since the multiple flow paths referred to in the present invention are the first and second flow paths 7a and 7b, the value of the flow rate difference ΔQ is the same regardless of which of these is designated as the "reference flow path" of the present invention. However, in this embodiment, in the primary control described later, the operating speed of the first pump Pa is fixed, and the operating speed of the second pump Pb is changed. Therefore, the first flow path 7a corresponds to an example of a "reference flow path" as defined in the present invention, and the second flow path 7b corresponds to an example of another flow path as defined in the present invention.

[0030] In step S3 described above, if the flow rate difference ΔQ is less than or equal to a predetermined value α, the first and second pumps Pa and Pb are operated at their initial set speeds without any speed changes (S3:YES, S4). Subsequently, when an operation to terminate water circulation is performed on the control unit 80, the operation of the first and second pumps Pa and Pb stops and ends (S5:YES, S6, End). The case where step S5 is NO will be discussed later.

[0031] In step S3, if the flow rate difference ΔQ exceeds a predetermined value α, primary control is initiated (S3:NO, S7). Here, primary control is a control that changes the flow rate Q2 of the second flow path 7b in order to reduce the flow rate difference ΔQ to a predetermined value α or less, while keeping the flow rate Q1 of the first flow path 7a, which serves as the reference flow path, constant. In this control, the operating speed of the first pump Pa is not changed, and only the operating speed of the second pump Pb is changed, making the control to reduce the flow rate difference ΔQ to a predetermined value α or less simple. When the flow rate difference ΔQ decreases to a predetermined value α or less due to the execution of the primary control described above, the primary control is terminated and the process proceeds to step S4 (S8:YES, S9).

[0032] As described above, if the primary control sets the flow rate difference ΔQ to a small value of α or less, it is possible to prevent or suppress water overflow or depletion by ensuring that there is no large bias in the amount of water entering and leaving both the first and second tanks 6a and 6b. Furthermore, if the predetermined value α is set to zero, as in this embodiment, primary control will be executed even with a small flow rate difference ΔQ, resulting in a higher frequency of primary control execution. This would have the disadvantage of increasing the burden on the second pump Pb due to frequent speed changes, but this embodiment makes it possible to avoid such disadvantages.

[0033] On the other hand, contrary to the above, if primary control is performed and the flow rate Q2 of the second flow path 7b is changed to a predetermined first limit, but the flow rate difference ΔQ does not decrease to a predetermined value α or less, the primary control is terminated (S8: NO, S10: YES, S11). This prevents the primary control from being performed excessively for an extended period, and appropriately prevents the flow rate Q2 from being changed to an inappropriate flow rate due to excessive changes.

[0034] After primary control is stopped, secondary control is started (S12). Here, secondary control, unlike primary control, is a control that changes the flow rate Q1 of the first flow path 7a in order to reduce the flow rate difference ΔQ to a predetermined value α or less while keeping the flow rate Q2 of the second flow path 7b constant. In this control, the operating speed of the second pump Pb is not changed, and only the operating speed of the first pump Pa is changed, so the control to reduce the flow rate difference ΔQ to a predetermined value α or less is simple. In addition, the flow rate Q2 of the second flow path 7b can be maintained at an appropriate flow rate that does not exceed the first limit. When the flow rate difference ΔQ decreases to a predetermined value α or less due to the execution of the secondary control described above, the secondary control is terminated and the process proceeds to step S4 (S13:YES, S14).

[0035] Unlike the above, if, when secondary control is performed, the flow rate Q1 of the first flow path 7a is changed to a predetermined second limit, but the flow rate difference ΔQ does not decrease to a predetermined value α or less, the control unit 8 determines that there is some kind of abnormality, and the notification unit 82 makes a notification to that effect (S13: NO, S15: YES, S16). In addition, the secondary control is stopped, and the operation of the first and second pumps Pa and Pb is stopped. This appropriately prevents the liquid circulation system SY from continuing to operate improperly despite an abnormality occurring.

[0036] The control unit 8 constantly detects the difference in liquid levels between the first and second tanks 6a and 6b. Therefore, as shown when step S5 is NO, if for any reason a difference greater than a predetermined amount occurs in the liquid levels of the first and second tanks 6a and 6b, the control unit 8 detects this (S17: YES). In this case, control is performed to reduce the amount of water flowing into the tank with the higher liquid level by reducing the operating speed of one of the first and second pumps Pa and Pb, or by temporarily stopping it (S18). Furthermore, when the difference in liquid levels decreases to less than a predetermined amount by the above control, the control is stopped at that point, and the process returns to step S3 (S19: YES, S20). This series of controls makes it possible to more thoroughly prevent water from overflowing from the first and second tanks 6a and 6b, thereby increasing the reliability and sense of security of the liquid circulation system SY.

[0037] Figures 3 and 4 show other embodiments of the present invention. In these figures, elements identical or similar to those in the above embodiments are denoted by the same reference numerals, and redundant explanations are omitted.

[0038] In the liquid circulation system SYa shown in Figure 3, a water treatment section 2 is provided in the middle of the first flow path 7a, which uses water to cool or wash desired items. The upstream area 70 of the first flow path 7a is the part that supplies water from the first tank 6a to the water treatment section 2, and the downstream area 71 is the part that supplies the water used in the water treatment section 2 to the second tank 6b.

[0039] A heat exchanger 18 for cooling is provided in the middle of the second flow path 7b. The cooling heat exchanger 18 is for cooling the water in the second flow path 7b. A cooling medium is supplied to this heat exchanger 18 from a separately provided chiller 17, and the water in the second flow path 7b is cooled by heat exchange between it and the cooling medium.

[0040] In the aforementioned liquid circulation system SYa, water can be supplied from the first tank 6a to the water treatment process section 2. Furthermore, water used for cooling and washing items in the water treatment process section 2 can be collected in the second tank 6b, recycled as cooled water, returned to the first tank 6a, and then resupplied to the water treatment process section 2. In addition, the same control as described with reference to Figure 2 is performed in this liquid circulation system SYa. As a result, overflow and depletion of water from the first and second tanks 6a and 6b are appropriately prevented, and processing in the water treatment process section 2 can be properly continued.

[0041] The liquid circulation system SYb shown in Figure 4 comprises third to fifth tanks 6c to 6e, third to fifth flow paths 7c to 7e for circulating water between them, third to fifth pumps Pc to Pe installed in them, and a flow sensor 12. In this liquid circulation system SYb, for example, the third flow path 7c is designated as the reference flow path, and operation control as shown in the flowchart of Figure 5 is performed. That is, after water circulation is started and the operation of the third to fifth pumps Pc to Pe is started, the control unit 8 determines whether the flow rate difference ΔQa is less than or equal to a predetermined value α, and whether the flow rate difference ΔQb is less than or equal to a predetermined value α (S31:YES, S32, S33, S35). Here, the flow rate difference ΔQa is the difference in flow rate Q4 of the fourth flow path 7d with respect to the flow rate Q3 of the third flow path 7c. The flow rate difference ΔQb is the difference in flow rate Q5 of the fifth flow path 7e with respect to the flow rate Q3 of the third flow path 7c. If both the flow rate differences ΔQa and ΔQb are less than or equal to a predetermined value α, the third to fifth pumps Pc to Pe continue to operate as is (S33:YES, S35:YES, S37).

[0042] In contrast to the above, if the flow rate difference ΔQa exceeds a predetermined value α, Primary control is initiated (S33:NO, S34). In this primary control, the flow rate of the third flow rate Q3 is kept constant while the flow rate of the fourth flow rate Q4 is changed so that the flow rate difference ΔQa is less than or equal to a predetermined value α. Primary control is also initiated if the flow rate difference ΔQb exceeds a predetermined value α (S35:NO, S36). In this primary control, the flow rate of the third flow rate Q3 is kept constant while the flow rate of the fifth flow rate Q5 is changed. In this way, if the flow rate of the third flow rate Q3 is kept constant, it is not necessary to control the speed of all of the third through fifth pumps Pc to Pe, and the operating speed of the third pump Pc can remain constant, thus simplifying control. Although omitted in Figure 5, in the liquid circulation system SYb shown in Figure 4, the secondary control of the flowchart shown in Figure 2 is also executed using the third flow rate Q3 as the reference flow rate, similar to the primary control described above.

[0043] The present invention is not limited to the embodiments described above. The specific configuration of each part of the liquid circulation system according to the present invention can be modified in various ways within the scope intended by the present invention.

[0044] In the embodiments described above, the cases with two or three tanks were explained as examples, but there are no limitations on the specific number of tanks; any number of tanks is acceptable. Furthermore, while the liquid circulation system is suitable for use in aquaponic systems and systems that use water for cooling and cleaning items, as shown in Figure 3, it is not limited to these applications and can be used for a variety of purposes. Therefore, the specific configuration of the tank (shape, material, size, etc.) can be varied in various ways. The liquid to be circulated can also be a liquid other than water. To change the liquid flow rate in multiple channels, one can change the operating speed of the pump. Alternatively, or in addition to this, a flow control valve can be installed in the channel, and the liquid flow rate can be changed using this valve. There are no specific numerical limits for the predetermined value α, the first limit, the second limit, etc. As previously mentioned, the predetermined value α can also be set to zero. [Explanation of symbols]

[0045] SY, SYa, SYb Liquid Circulation System Pa~Pe Pumps 1 through 5 6a-6e The first to fifth tanks (tanks) 7a~7e First to fifth channels (channels) 8. Control Unit (Control Means) 10. Liquid level detector (liquid level detection means) 11 Heat exchanger

Claims

1. Multiple open tanks capable of storing liquids, Multiple flow paths that enable the circulation of the liquid in these multiple tanks, and multiple pumps provided in these multiple flow paths, Control means capable of controlling the liquid flow rate of each of the aforementioned plurality of flow paths, A liquid circulation system equipped with, A liquid circulation system characterized in that the control means is configured to designate one of the plurality of flow paths as a reference flow path, detect the flow rate difference ΔQ of the liquid flow paths of the other flow paths based on the liquid flow rate of the reference flow path, and when this flow rate difference ΔQ exceeds a predetermined value α, execute primary control to change the liquid flow rate of the other flow paths in order to reduce the flow rate difference ΔQ to the predetermined value α or less while maintaining the liquid flow rate of the reference flow path at a constant level.

2. A liquid circulation system according to claim 1, The aforementioned plurality of tanks include first and second tanks for storing the liquid to be stored in a state with a temperature difference, as a high-temperature liquid and a low-temperature liquid. The plurality of flow paths include first and second flow paths capable of causing the liquid to flow from one of the first and second tanks to the other, and from the other to the first, respectively. A liquid circulation system comprising heat exchangers in the first and second flow paths, which enable heat exchange between the liquids flowing through them.

3. A liquid circulation system according to claim 1, The predetermined value α is a non-zero value. A liquid circulation system configured to maintain the speed of the multiple pumps so that the liquid flow rate of each of the multiple flow paths remains constant when the flow rate difference ΔQ is less than or equal to the predetermined value α.

4. A liquid circulation system according to claim 1, A liquid circulation system configured such that, during the execution of the primary control, if the flow rate difference ΔQ does not decrease to a predetermined value α or less despite the liquid flow rate of the other flow path being changed to a predetermined first limit, the primary control is terminated and a secondary control is executed to change the liquid flow rate of the reference flow path in order to reduce the flow rate difference ΔQ to a predetermined value α or less while maintaining the liquid flow rate of the other flow path at a constant level.

5. A liquid circulation system according to claim 4, A liquid circulation system configured such that, during the execution of the secondary control, if the liquid flow rate of the reference flow path is changed to a predetermined second limit, but the flow rate difference ΔQ does not decrease to a predetermined value α or less, the operation of the plurality of pumps is stopped.

6. A liquid circulation system according to claim 1, The system further includes a liquid level detection means capable of detecting the liquid level of the liquid stored in each of the aforementioned multiple tanks, A liquid circulation system configured such that when the difference in the liquid levels of the plurality of tanks exceeds a predetermined level, control is performed to stop the inflow of liquid to the tank with the highest liquid level among the plurality of tanks, or to reduce the amount of liquid inflow.

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