Piping System

Abstract

To provide a piping system for suppressing diffusion of oxygen into a retained liquid.SOLUTION: A piping system 1 includes: a circulation pipe 10 forming a closed circulation passage in which a liquid CH circulates; an open-type expansion tank 21; a connection pipe 23 for connecting the circulation pipe 10 and the expansion tank 21; and a cutout device 30 which closes the passage of the connection pipe 23 in a normal time and opens the passage when the liquid CH circulating in the circulation passage expands or shrinks. With this configuration, a diffusion of residue oxygen inside the liquid can be prevented when a passage of the connection pipe 23 is blocked by the cutout device 30.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to piping systems, and more particularly to piping systems having closed piping connected to an open expansion tank. [Background technology]

[0002] For example, for heating and cooling purposes within a building, a piping system is often constructed to supply cold and hot water generated by a heat source device such as a hot and cold water generator to air conditioning equipment such as an air handling unit or a fan coil unit. One such piping system has a closed circulation path between the heat source device and the air conditioning equipment for circulating the cold and hot water, and an open-to-air expansion tank connected to this circulation path to absorb expansion and contraction caused by temperature changes of the cold and hot water in the circulation path (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5708992 Summary of the Invention [Problem to be solved by the invention]

[0004] A piping system using an open-to-atmospheric expansion tank has no fluctuations in reference pressure, and is therefore superior in controllability and maintenance and running costs compared to a system using a sealed expansion tank. However, when an open-to-atmospheric expansion tank is used, oxygen can enter and diffuse into the liquid from the liquid surface exposed to the atmosphere in the tank, which can cause corrosion of the piping, etc.

[0005] In view of the above-mentioned problems, the present disclosure relates to providing a piping system that suppresses the diffusion of oxygen into a retained liquid. [Means for solving the problem]

[0006] A piping system according to a first aspect of the present disclosure includes a circulation pipe that forms a sealed circulation flow path and through which a liquid circulates, an open expansion tank, a connecting pipe that connects the circulation pipe and the expansion tank, and a shutoff device that closes the flow path of the connecting pipe under normal conditions and opens it when the liquid circulating through the circulation flow path may expand or contract. Here, the normal conditions typically refer to a time when there is no temperature change in the liquid inside the circulation flow path.

[0007] With this configuration, when the flow path of the connecting pipe is blocked by the blocking device, it is possible to prevent the diffusion of dissolved oxygen inside the liquid.

[0008] Furthermore, a piping system according to a second aspect of the present disclosure is the piping system according to the first aspect of the present disclosure, wherein the shutoff device includes a first pipe, a second pipe arranged in parallel to the first pipe, a first check valve provided in the first pipe to allow liquid inside the first pipe to flow from the circulation pipe side to the expansion tank side, and a second check valve provided in the second pipe to allow liquid inside the second pipe to flow from the expansion tank side to the circulation pipe side.

[0009] With this configuration, when there is no expansion or contraction of the held liquid under normal circumstances, the check valve blocks the flow path of the connecting pipe to prevent the diffusion of dissolved oxygen inside the liquid, while when expansion or contraction of the held liquid occurs, liquid can be allowed to flow in and out of the expansion tank.

[0010] Furthermore, a piping system according to a third aspect of the present disclosure is the piping system according to the first or second aspect of the present disclosure, wherein the shutoff device includes an on-off valve that opens and closes the flow path of the connecting pipe, and the piping system further includes a detector that directly or indirectly detects the pressure inside the circulation pipe or a physical quantity related to pressure, and a first control device that opens the on-off valve when the amount of change in the value detected by the detector over a predetermined period of time reaches a predetermined value.

[0011] With this configuration, under normal circumstances, the on-off valve blocks the flow path of the connecting pipe to prevent the diffusion of dissolved oxygen inside the liquid, but when the internal pressure changes, the on-off valve can be opened to allow liquid to flow in and out of the expansion tank.

[0012] Furthermore, a piping system according to a fourth aspect of the present disclosure is a piping system according to any one of the first to third aspects of the present disclosure, wherein the shut-off device includes an on-off valve that opens and closes the flow path of the connecting pipe, and the piping system further includes a heat source device provided in the circulation pipe, and a second control device that closes the on-off valve when the liquid inside the circulation pipe is substantially equal to the ambient temperature, and opens the on-off valve for at least a predetermined period of time while the heat source device is operating.

[0013] With this configuration, when there is no temperature difference in the liquid inside the circulation flow path under normal conditions, the flow path of the connecting piping can be blocked by the on-off valve to prevent the diffusion of dissolved oxygen inside the liquid, and when the temperature of the liquid may change due to the operation of the heat source device, the on-off valve can be opened to allow liquid to flow in and out of the expansion tank. [Effects of the Invention]

[0014] According to the present disclosure, when the flow path of the connecting pipe is blocked by the blocking device, it is possible to prevent the diffusion of dissolved oxygen inside the liquid. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic diagram of a piping system according to a first embodiment. [Figure 2] FIG. 10 is a schematic diagram of a piping system according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment will be described with reference to the drawings. In the drawings, identical or similar reference numerals are used to designate identical or corresponding components, and redundant explanations will be omitted.

[0017] First, referring to FIG. 1, a piping system 1 according to a first embodiment will be described. FIG. 1 is a schematic diagram of the piping system 1. From an overview, the piping system 1 is a semi-closed system in which an open-type expansion tank 21 (hereinafter simply referred to as the "expansion tank 21") is connected to a closed-type circulation pipe 10. Here, a semi-closed system is a system in which the circulating liquid system is in contact with air only at the expansion tank 21. In a semi-closed system, there is almost no liquid flow between the circulation pipe and the expansion tank, and the circulating liquid is almost never in direct contact with air. Concepts that contrast with semi-closed systems include open systems and closed systems. An open system is a system in which the circulating liquid system has a portion open to air, such as a heat storage tank, and has a larger surface area in contact with air than a semi-closed system. In an open system, the circulating liquid passes through a portion open to air, such as a heat storage tank, and therefore comes into direct contact with air more often. A closed system is typically a system in which a closed-type expansion tank is connected, and the circulating liquid system has no portion in contact with air.

[0018] In open and semi-closed systems that have surfaces in contact with air, the presence of dissolved oxygen, which can cause corrosion of pipes, has been a problem. Both open and semi-closed systems have surfaces in contact with air, but in semi-closed systems, unlike open systems, the circulating liquid rarely comes into direct contact with air, which may limit the diffusion of dissolved oxygen. In other words, in semi-closed systems, convection is less likely to occur in the piping connecting the expansion tank and the circulation piping, so it is possible that dissolved oxygen will not diffuse into the liquid in the circulation piping unless the liquid that comes into contact with air in the expansion tank enters the circulation piping.

[0019] To verify the above theory, the inventors conducted the following investigation into whether dissolved oxygen diffuses in a semi-closed system even when there is no liquid movement. First, a 50A diameter VP pipe was installed vertically with a length of 4500 mm. A 400mm x 400mm x 400mm water tank was installed above the standpipe, acting as an open-type expansion tank, and a circulation pipe was installed below the standpipe. Then, using the bottom of the standpipe (where it connects to the circulation pipe) as the base point, dissolved oxygen meters (fluorescent type) were installed at positions 0mm, 500mm, 2500mm, and 4500mm above the base point (the top three dissolved oxygen meters were spaced 2000mm apart). Water was filled into this experimental setup, and the dissolved oxygen concentration was measured. Measurements showed that the oxygen concentration began to rise over time, starting with the dissolved oxygen meters closest to the tank. The oxygen concentration began to rise shortly after the start of measurements for the highest dissolved oxygen meter (located 4,500 mm above the base point), and seven days after measurements began for the lowest dissolved oxygen meter (located 0 mm from the base point). This confirmed that dissolved oxygen travels through a 50A diameter, approximately 5 m long pipe in about seven days. The dissolved oxygen concentration in the pipe increased over time, reaching near saturation in about 107 days. The saturation oxygen concentration here is a theoretical value calculated from the water temperature value at 0 mm from the base point using the JIS K0102 table for dissolved oxygen in water.

[0020] Verification revealed that dissolved oxygen diffuses even when the system is stopped (when there is no water movement). However, considering the actual operating conditions of a piping system, it is believed that temperature changes, i.e., changes in the density of the retained liquid (expansion and / or contraction), occur mostly during a certain period from the start of operation of the heat source device or a certain period after operation is stopped. Taking these points into consideration, the inventors came up with a piping system that can suppress the diffusion of dissolved oxygen. The following first describes the configuration of the piping system 1. The piping system 1 includes a circulation piping 10, an expansion tank 21, a connecting piping 23, and a shutoff device 30.

[0021] In this embodiment, the circulation piping 10 includes a primary-side piping 11, a secondary-side piping 15, a supply header 18, and a return header 19. The primary-side piping 11 is provided with a heat source device 12, such as a refrigerator or a chilled / hot water generator, and a pump 13. The primary-side piping 11 guides liquid chilled / hot water CH from the return header 19 to the heat source device 12 by operation of the pump 13, and guides the chilled / hot water CH, whose temperature has been adjusted in the heat source device 12, to the supply header 18. The secondary-side piping 15 is provided with air conditioning equipment 16, such as an air handling unit or a fan coil unit. The secondary-side piping 15 guides the chilled / hot water CH from the supply header 18 to the air conditioning equipment 16, and guides the chilled / hot water CH, whose temperature has been changed by heat utilization in the air conditioning equipment 16, to the return header 19. In this embodiment, the secondary-side piping 15 is provided with three systems of secondary-side piping 15A, 15B, and 15C, and different or similar types of air conditioning equipment 16A, 16B, and 16C are arranged in each system. The number of systems constituting the secondary-side piping 15 is not limited to three, and may be one, two, or four or more. Although not shown in the figure, the heat source device 12, the pump 13, and the air conditioning equipment 16 are typically configured so that they can be started and stopped and their control amounts adjusted by commands from a control device.

[0022] The circulation pipe 10 forms a circulation flow path through which chilled / hot water CH circulates through the primary-side pipe 11 (including the heat source device 12), the supply header 18, the secondary-side pipe 15 (including the air conditioning equipment 16), and the return header 19 by operation of the pump 13. The circulation pipe 10 is a sealed flow path, with no parts coming into contact with air during the circulation of the chilled / hot water CH. In this embodiment, the pump 13 provides the head required for the chilled / hot water CH to flow through the secondary-side pipe 15. However, a secondary pump (not shown) may be installed in the secondary-side pipes 15A, 15B, and 15C of each system. By providing the secondary pump (not shown), it becomes possible to supply chilled / hot water CH to each of the air conditioning equipment 16A, 16B, and 16C at a flow rate corresponding to the load of each of the air conditioning equipment 16A, 16B, and 16C by inverter control. In this case, it is sufficient for the pump 13 to have a head sufficient to transport the chilled / hot water CH from the return header 19 to the supply header 18.

[0023] As described above, the expansion tank 21 is an open-type expansion tank. The expansion tank 21 is connected to the circulation pipe 10 by the connection pipe 23. In other words, the connection pipe 23 is a pipe that connects the circulation pipe 10 and the expansion tank 21. In this embodiment, the connection pipe 23 is connected to the circulation pipe 10 at the return header 19. Since the expansion tank 21 is an open-type expansion tank, when pressure fluctuations occur due to expansion or contraction of the chilled or hot water CH inside the circulation pipe 10, the pressure fluctuations are released to the atmosphere, so the reference pressure, which is atmospheric pressure, does not fluctuate, resulting in excellent controllability. The expansion tank 21 can also serve as a cushion tank. The expansion tank 21 is typically installed above the highest part of the circulation pipe 10, and preferably installed at least 1 meter above the highest point of the circulation pipe 10. A known open-type expansion tank can be used as the expansion tank 21, and is typically connected to an overflow pipe (not shown) and a make-up water pipe (not shown). The area below the liquid level in the expansion tank 21 is filled with liquid (water in this embodiment), including the interior of the connection pipe 23 and the circulation pipe 10. Therefore, the piping system 1 is not exposed to the atmosphere (air) except for the liquid level in the expansion tank 21.

[0024] The shutoff device 30 is a device capable of shutting off the flow path inside the connection pipe 23. The shutoff device 30 is provided in the connection pipe 23. The reason why the shutoff device 30 shuts off the flow path inside the connection pipe 23 is to prevent the diffusion of dissolved oxygen when there is no movement in the liquid inside the connection pipe 23, based on the verification of the diffusion of dissolved oxygen described above. On the other hand, when expansion or contraction occurs in the chilled or hot water CH inside the circulation pipe 10, it is necessary to unblock the flow path inside the connection pipe 23 in order to release the pressure fluctuations that occur at that time. In consideration of these points, the shutoff device 30 in this embodiment is configured as follows.

[0025] The shutoff device 30 has a first pipe 31 and a second pipe 32. The first pipe 31 and the second pipe 32 are connected in parallel. A first check valve 33 is provided in the first pipe 31. The first check valve 33 is disposed in the first pipe 31 in a direction that allows liquid to flow from the circulation pipe 10 side to the expansion tank 21 side and prevents liquid from flowing in the opposite direction. A second check valve 34 is provided in the second pipe 32. The second check valve 34 is disposed in the second pipe 32 in a direction that allows liquid to flow from the expansion tank 21 side to the circulation pipe 10 side and prevents liquid from flowing in the opposite direction. In the shutoff device 30, the first pipe 31 corresponds to the first pipe, the second pipe 32 corresponds to the second pipe, the first check valve 33 corresponds to the first check valve, and the second check valve 34 corresponds to the second check valve. The shutoff device 30 configured in this manner is inserted into the connecting pipe 23, so that one of the connections between the first pipe 31 and the second pipe 32 is connected to the connecting pipe 23 on the circulation pipe 10 side, and the other is connected to the connecting pipe 23 on the expansion tank 21 side. The shutoff device 30 is preferably provided as far away as possible from the circulation pipe 10, and is preferably provided closer to the expansion tank 21 than at least half the total length of the connecting pipe 23, and is more preferably provided within 1 / 10 of the total length of the connecting pipe 23 from the expansion tank 21.

[0026] Next, the operation of the piping system 1 will be described. When the pump 13 of the piping system 1 is stopped and a considerable amount of time has passed since the flow of chilled or hot water CH inside the circulation piping 10 stopped, and the temperature of the chilled or hot water CH is approximately the same as the ambient temperature (normal), the water inside the connecting piping 23 and the expansion tank 21 is also stationary. At this time, the first check valve 33 and the second check valve 34 of the shutoff device 30 are closed. In this state, the water surface of the expansion tank 21 is exposed to air. Based on the aforementioned verification results of the diffusion of dissolved oxygen, oxygen in the air dissolves in the water from the water surface of the expansion tank 21 and tends to diffuse toward the circulation piping 10 over time. However, in the piping system 1 according to this embodiment, the first check valve 33 and the second check valve 34 block the flow path of the connecting piping 23, thereby preventing the diffusion of dissolved oxygen.

[0027] When the pump 13 is started, the chilled / hot water CH inside the circulation pipe 10 flows, and the flowing chilled / hot water CH circulates inside the circulation pipe 10. When there is no change in temperature, the chilled / hot water CH circulating inside the circulation pipe 10 typically does not flow into or out of the connecting pipe 23, so the first check valve 33 and the second check valve 34 remain closed. Therefore, when the chilled / hot water CH circulates through the circulation pipe 10 but does not flow into or out of the connecting pipe 23, it is possible to prevent the diffusion of dissolved oxygen from the expansion tank 21 into the circulation pipe 10.

[0028] Thereafter, when the heat source device 12 operates and the chilled / hot water CH circulating inside the circulation piping 10 is heated, for example, in the heat source device 12, the chilled / hot water CH with an increased temperature flows out of the heat source device 12. The chilled / hot water CH flowing out of the heat source device 12 is heated to a temperature suitable for use in the air conditioning equipment 16. The temperature of the chilled / hot water CH flowing out of the air conditioning equipment 16 and into the heat source device 12 is lower than the temperature of the chilled / hot water CH flowing out of the heat source device 12 by the amount of heat used in the air conditioning equipment 16, but is generally higher than the ambient temperature. Therefore, when the heat source device 12 starts heating operation, the temperature of the chilled / hot water CH circulating through the circulation piping 10 rises. The chilled / hot water CH circulating through the circulation piping 10 expands as its temperature rises. The expanded chilled / hot water CH flows from the circulation piping 10 into the connecting piping 23. When chilled or hot water CH flows into the connecting pipe 23, a force acts to lift the chilled or hot water CH inside the connecting pipe 23, and this force opens the first check valve 33, causing the water to move toward the expansion tank 21 and push up the water level in the expansion tank 21. When the chilled or hot water CH equivalent to the expansion of the circulation pipe 10 has completely flowed into the connecting pipe 23, the movement of water inside the connecting pipe 23 and the expansion tank 21 stops and the first check valve 33 closes. During the movement of water in this direction, the second check valve 34 remains closed throughout. In this way, since the shutoff device 30 is equipped with the first check valve 33, it is possible to move only the necessary amount of water that is trying to move from the circulation pipe 10 side to the expansion tank 21 side. In addition, when the temperature of the cold / hot water CH circulating through the circulation pipe 10 stabilizes during heating operation of the heat source device 12 and the movement of water inside the connecting pipe 23 stops, the first check valve 33 and the second check valve 34 close, preventing the diffusion of dissolved oxygen from the expansion tank 21 to the circulation pipe 10.

[0029] Thereafter, when the heat source device 12 is stopped and the heating of the chilled / hot water CH circulating inside the circulation piping 10 is no longer performed, the temperature of the chilled / hot water CH circulating inside the circulation piping 10 gradually drops and approaches the ambient temperature. The chilled / hot water CH circulating inside the circulation piping 10 contracts as its temperature drops. The contracted chilled / hot water CH flows from the connecting piping 23 into the circulation piping 10. At this time, water moves inside the connecting piping 23 from the expansion tank 21 side to the circulation piping 10 side. At this time, the second check valve 34 opens, and the water flows through the second piping 32. When the flow of the chilled / hot water CH corresponding to the contraction in the circulation piping 10 from the connecting piping 23 into the circulation piping 10 is complete, the movement of water inside the connecting piping 23 and the expansion tank 21 stops, and the second check valve 34 closes. When viewed from the second check valve 34, when water on the expansion tank 21 side passes through the second check valve 34 toward the circulation pipe 10 side, water on the expansion tank 21 side that may contain dissolved oxygen will flow into the circulation pipe 10 side. However, because the water passing through the second check valve 34 remains only as much as the chilled or hot water CH inside the circulation pipe 10 has contracted, the amount of dissolved oxygen flowing into the circulation pipe 10 side can be minimized. When water on the expansion tank 21 side passes through the second check valve 34 toward the circulation pipe 10 side, the first check valve 33 remains closed throughout. In this way, because the shutoff device 30 is equipped with the second check valve 34, the amount of water attempting to move from the expansion tank 21 side to the circulation pipe 10 side can be kept to a necessary amount, thereby suppressing the diffusion of dissolved oxygen from the expansion tank 21 into the circulation pipe 10. Furthermore, when the temperature of the chilled / hot water CH circulating through the circulation pipe 10 stabilizes after the heat source device 12 is stopped and the movement of water inside the connection pipe 23 stops, the first check valve 33 and the second check valve 34 close, preventing the diffusion of dissolved oxygen from the expansion tank 21 to the circulation pipe 10. Note that the pump 13 typically stops after performing any necessary residual operation after the heat source device 12 is stopped.

[0030] As described above, the piping system 1 according to this embodiment is provided with the shutoff device 30, which can prevent the diffusion of dissolved oxygen from the expansion tank 21 to the circulation piping 10 when there is no flow of chilled or hot water CH between the circulation piping 10 and the connection piping 23. Furthermore, the shutoff device 30 has the first check valve 33 that allows the flow of liquid from the circulation piping 10 to the expansion tank 21 and blocks the flow in the reverse direction, so that only a necessary amount of chilled or hot water CH expanded inside the circulation piping 10 can be moved out of the circulation piping 10 without delay. Furthermore, the shutoff device 30 has the second check valve 34 that allows the flow of liquid from the expansion tank 21 to the circulation piping 10 and blocks the flow in the reverse direction, so that the amount of water containing dissolved oxygen that flows into the circulation piping 10 when the chilled or hot water CH in the circulation piping 10 contracts can be minimized. In the above explanation, an example was shown in which the heat source device 12 heats the chilled / hot water CH, but it goes without saying that even when the heat source device 12 operates to cool the chilled / hot water CH, the expansion and contraction of the chilled / hot water CH inside the circulation pipe 10 can be released to the expansion tank 21 while suppressing the diffusion of dissolved oxygen. When the heat source device 12 operates to cool the chilled / hot water CH, the chilled / hot water CH contracts when the heat source device 12 is operating and expands when the heat source device 12 is stopped, and the action of the shut-off device 30 during the expansion and contraction of the chilled / hot water CH is as described above.

[0031] Next, a piping system 2 according to a second embodiment will be described with reference to Fig. 2. Fig. 2 is a schematic system diagram of the piping system 2. In this embodiment, the piping system 2 differs from the piping system 1 mainly in that a shutoff device 30A is provided instead of the shutoff device 30 (see Fig. 1), a pressure sensor 38 is provided in the forward header 18, and a control device 50 is provided.

[0032] The shutoff device 30A includes an on-off valve 36 that opens and closes the flow path inside the connecting pipe 23 in response to an external control signal. The on-off valve 36 allows liquid to flow in both directions when open. Known types of on-off valve 36, such as a gate valve, ball valve, or butterfly valve, can be used, taking into consideration the diameter of the connecting pipe 23 to be installed and the type of fluid flowing inside the connecting pipe 23. The on-off valve 36 has an actuator that moves a valve element between an open position and a closed position, and the actuator moves the valve element in response to an external control signal. Similar to the shutoff device 30 (see FIG. 1), the shutoff device 30A (on-off valve 36) is preferably provided as far away as possible from the circulation pipe 10 (as close as possible to the expansion tank 21).

[0033] The pressure sensor 38 is a device that primarily detects the pressure inside the circulation pipe 10. The pressure sensor 38 is a device that directly detects the pressure inside the circulation pipe 10 and corresponds to a detector. The pressure sensor 38 is capable of outputting the detected pressure as a signal to the outside. In this embodiment, the pressure sensor 38 is provided in the forward header 18 that constitutes part of the circulation pipe 10. However, the pressure sensor 38 may be provided in a portion of the circulation pipe 10 other than the forward header 18, such as the secondary side pipe 15. Alternatively, the pressure sensor 38 may be provided in the connecting pipe 23 so as to detect the pressure inside the connecting pipe 23, which is in communication with the inside of the circulation pipe 10 and is affected by pressure fluctuations inside the circulation pipe 10, thereby indirectly detecting the pressure inside the circulation pipe 10. Alternatively, a temperature sensor that directly detects the temperature of the chilled / hot water CH, which affects pressure fluctuations inside the circulation pipe 10, may be provided in the circulation pipe 10 instead of the pressure sensor 38 as a detector. In this case, the temperature of the chilled / hot water CH corresponds to a physical quantity related to the internal pressure of the circulation pipe 10.

[0034] The control device 50 is a device that controls the operation of the piping system 2. The control device 50 is connected to the heat source device 12 by a communication line (wired or wireless; the same applies below) and is configured to be able to control the start and stop of the heat source device 12. The control device 50 is also connected to the pump 13 by a communication line and is able to control the start and stop of the pump 13, and is configured to be able to adjust the discharge flow rate of the pump 13 if the pump 13 has an inverter. The control device 50 is also connected to the on-off valve 36 by a communication line and is configured to be able to control the opening and closing operation of the on-off valve 36. The control device 50 is also connected to the pressure sensor 38 by a communication line and is configured to be able to receive the value detected by the pressure sensor 38 as a signal.

[0035] In this embodiment, the control device 50 further includes a first control unit 51 and a second control unit 52. The first control unit 51 controls the on-off valve 36 to open when a change in the value detected by the pressure sensor 38 over a predetermined period of time reaches a predetermined value, and corresponds to the first control device. Here, the "predetermined period" may typically be a period during which the temperature of the chilled or hot water CH accompanying the operation of the heat source device 12 is reflected in a change in the pressure inside the circulation piping 10, and may be, for example, several minutes to several tens of minutes or several hours. The "predetermined value" is the difference in the value when the pressure inside the circulation piping 10 fluctuates to an extent that it is preferable to release the pressure to the outside when the on-off valve 36 is closed, for example, the amount of change in pressure that could damage the circulation piping 10 if the fluctuating pressure is not released to the outside.

[0036] The second control unit 52 controls the on-off valve 36 so as to close the on-off valve 36 when the temperature of the chilled / hot water CH inside the circulation pipe 10 is substantially equal to the ambient temperature, and to close the on-off valve 36 when a temperature change is occurring or is likely to occur. A typical example of a case in which the chilled / hot water CH inside the circulation pipe 10 becomes substantially equal to the ambient temperature is the period from a predetermined time after the heat source device 12 is stopped until the heat source device 12 is started. Here, the predetermined period is typically the time required for the temperature of the chilled / hot water CH inside the circulation pipe 10 to become substantially equal to the ambient temperature after the heat source device 12 is stopped. The term "temperature substantially equal to the ambient temperature" is intended to include not only a case in which the temperature is equal to the ambient temperature, but also a difference from the ambient temperature that is small enough that pressure fluctuations inside the circulation pipe 10 due to a temperature difference from the ambient temperature do not adversely affect (damage, etc.) the circulation pipe 10. Typical examples of cases where a temperature change occurs in the chilled / hot water CH inside the circulation piping 10 include the period from when the heat source device 12 is started until a predetermined period has elapsed, and the period from when the heat source device 12 is stopped until the above-mentioned predetermined time has elapsed. The predetermined period is typically the time required from when the heat source device 12 is started until the chilled / hot water CH supplied by the heat source device 12 reaches the target temperature. In this way, the second control unit 52 controls the on-off valve 36 to close when the temperature of the chilled / hot water CH inside the circulation piping 10 is substantially equal to the ambient temperature, and to open the on-off valve 36 at least for a predetermined period while the heat source device 12 is operating, and corresponds to a second control device.

[0037] In this embodiment, the first control unit 51 and the second control unit 52 are shown as separate entities distinguished by their control functions for convenience of explanation, but typically the two are configured as an integrated whole, or the two may be configured as physically separate entities. Note that in this embodiment, the shutoff device 30A, the pressure sensor 38, and the control device 50 have been described so far, but the configuration of the piping system 2 other than the above is the same as that of the piping system 1 (see FIG. 1), so duplicated explanations will be omitted.

[0038] In the piping system 2 configured as described above, when the pump 13 is stopped, a considerable amount of time has passed since the flow of the chilled or hot water CH inside the circulation piping 10 stopped, and the temperature of the chilled or hot water CH is approximately the same as the ambient temperature (normal), the on-off valve 36 is closed. Because the on-off valve 36 is closed and the flow path of the connection piping 23 is blocked, diffusion of dissolved oxygen from the expansion tank 21 to the circulation piping 10 can be prevented.

[0039] When the heat source device 12 is started by a signal from the control device 50, the second control unit 52 opens the on-off valve 36. When the on-off valve 36 is opened, the flow path of the connection pipe 23 opens, and the circulation pipe 10 and the expansion tank 21 are connected. As a result, even if the operation of the heat source device 12 causes the temperature of the chilled or hot water CH supplied from the heat source device 12 to change from the ambient temperature, causing the chilled or hot water CH to expand or contract, the chilled or hot water CH can be released to the expansion tank 21, and excessive pressure fluctuations inside the circulation pipe 10 can be suppressed.

[0040] The second control unit 52 closes the on-off valve 36 after a predetermined period of time has elapsed since the on-off valve 36 was opened (since the heat source device 12 was started up). By the time the predetermined period of time has elapsed since the heat source device 12 was started up, the chilled or hot water CH supplied from the heat source device 12 will normally have stabilized at a target temperature, and there will be no temperature changes, or even if there is a temperature change, it will be to a degree that does not adversely affect the structure of the circulation piping 10. For this reason, in this embodiment, when the heat source device 12 is in steady operation and there is substantially no temperature change in the chilled or hot water CH supplied (normal time), the on-off valve 36 is closed to prevent diffusion of dissolved oxygen from the expansion tank 21 to the circulation piping 10.

[0041] During steady-state operation of the heat source device 12, the temperature of the chilled / hot water CH circulating inside the circulation pipe 10 may fluctuate due to fluctuations in the heat load to be processed by the air conditioning equipment 16 and other factors. If the temperature of the chilled / hot water CH inside the circulation pipe 10 changes and causes expansion or contraction, this phenomenon will appear in the detected value of the pressure sensor 38. When the amount of change in the detected value of the pressure sensor 38 received by the control device 50 reaches a predetermined value, the first control unit 51 opens the on-off valve 36. This allows the pressure fluctuations occurring inside the circulation pipe 10 to be released to the expansion tank 21. Thereafter, once the temperature of the chilled / hot water CH circulating inside the circulation pipe 10 has stabilized, the first control unit 51 preferably closes the on-off valve 36 to prevent diffusion of dissolved oxygen from the expansion tank 21 into the circulation pipe 10. The determination of whether the temperature of the cold / hot water CH circulating inside the circulation pipe 10 has stabilized may be made by installing a temperature sensor (not shown) in the circulation pipe 10 and checking the detected value of the temperature sensor, or by checking whether a predetermined time has elapsed based on data from the trial operation.

[0042] When the heat source device 12 is stopped by a signal from the control device 50, the second control unit 52 opens the on-off valve 36 to connect the circulation pipe 10 and the expansion tank 21. When the heat source device 12 is stopped, the temperature of the chilled or hot water CH inside the circulation pipe 10 changes from the target temperature to approach the ambient temperature, and this changes the temperature, causing contraction or expansion. However, because the flow path of the connecting pipe 23 is open, this contraction or expansion can be released to the expansion tank 21. When a predetermined time has elapsed since the heat source device 12 was stopped, the second control unit 52 closes the on-off valve 36 to prevent diffusion of dissolved oxygen from the expansion tank 21 to the circulation pipe 10.

[0043] As described above, in the piping system 2, when expansion or contraction of the chilled or hot water CH inside the circulation pipe 10 does not occur, the on-off valve 36 is closed to prevent diffusion of dissolved oxygen from the expansion tank 21 to the circulation pipe 10. On the other hand, when expansion or contraction of the chilled or hot water CH inside the circulation pipe 10 occurs or is likely to occur, the on-off valve 36 is opened to release pressure fluctuations inside the circulation pipe 10 to the expansion tank 21. In this way, in the piping system 2, as in the piping system 1 (see FIG. 1 ), pressure fluctuations inside the circulation pipe 10 can be released to the expansion tank 21 while suppressing diffusion of dissolved oxygen from the expansion tank 21 to the circulation pipe 10.

[0044] In the example of the piping system 2 described above, the control device 50 has the first control unit 51 and the second control unit 52, but if control by the second control unit 52 is not required, the second control unit 52 may not be provided. On the other hand, if control by the first control unit 51 is not required, the first control unit 51 and the pressure sensor 38 may not be provided.

[0045] On the other hand, the on-off valve 36, the detector (pressure sensor 38), and the control device 50 disclosed in the piping system 2 may be superimposed and applied to the configuration of the piping system 1. In this configuration, even if the first check valve 33 and / or the second check valve 34 does not fully close due to the inclusion of debris or the like, the on-off valve 36 is closed, thereby preventing the dissolved oxygen in the expansion tank 21 from diffusing into the circulation piping 10.

[0046] In the above description, the liquid circulating inside the circulation pipe 10 is cold / hot water CH, but it may be a liquid other than cold / hot water CH, such as brine. [Explanation of symbols]

[0047] 1, 2 Piping system 10 Circulation piping 21 Expansion tank 23 Connecting piping 30 Circuit Breaker 31 First Pipe (First Pipe) 32 Second piping (second piping) 33 First check valve (first check valve) 34 Second check valve (second check valve) 36 On-off valve 38 Pressure sensor (detector) 50 Control device 51 First control unit (first control device) 52 Second control unit (second control device) CH Cold and hot water (liquid)

Claims

1. a circulation pipe that forms a sealed circulation flow path and through which a liquid circulates; An open expansion tank, a connecting pipe that connects the circulation pipe and the expansion tank; a shutoff device that normally closes the flow path of the connecting pipe and opens it when the liquid circulating through the circulation flow path may expand or contract, the shutoff device includes an on-off valve that opens and closes a flow path of the connection pipe, Furthermore, a heat source device provided in the circulation piping; a second control device that closes the on-off valve when the temperature of the liquid inside the circulation pipe is substantially equal to the ambient temperature, and opens the on-off valve for at least a predetermined period during operation of the heat source device; Piping system.

2. The shutoff device is A first pipe; a second pipe arranged in parallel with the first pipe; a first check valve provided in the first pipe to allow the liquid inside the first pipe to flow from the circulation pipe side to the expansion tank side; a second check valve provided in the second pipe to allow the liquid inside the second pipe to flow from the expansion tank side to the circulation pipe side; having The piping system of claim 1 .

3. A detector that directly or indirectly detects the pressure inside the circulation pipe or a physical quantity related to the pressure; a first control device that opens the on-off valve when a change in the value detected by the detector over a predetermined period of time reaches a predetermined value; The piping system according to claim 1 or 2.

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