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 a piping system, and more particularly to a piping system having a closed pipe to which an open expansion tank is connected.

Background Art

[0002] For example, for heating and cooling applications in a building, a piping system is often constructed that supplies chilled and heated water generated by a heat source device such as a chiller to air conditioning equipment such as an air handling unit or a fan coil unit. As such a piping system, a closed circulation path for circulating chilled and heated water is configured between the heat source device and the air conditioning equipment, and an atmospheric open type expansion tank is connected to this circulation path to absorb the expansion and contraction accompanying the temperature change of the chilled and heated water in the circulation path (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A piping system using an atmospheric open type expansion tank has excellent controllability compared to a system using a closed type expansion tank because the reference pressure does not fluctuate, and is also excellent in terms of maintenance and running costs. However, when using an atmospheric open type expansion tank, oxygen may enter the liquid from the liquid surface opened to the atmosphere in the tank and diffuse, causing corrosion of the piping and the like.

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

Means for Solving the Problems

[0006] The piping system according to the first aspect of the present disclosure forms a sealed circulation flow path, and includes a circulation pipe through which a liquid circulates in the circulation flow path, an open expansion tank, a connection pipe connecting the circulation pipe and the expansion tank, and a shut-off device that closes the flow path of the connection pipe during normal times and opens it when the liquid circulating in the circulation flow path can expand or contract. Here, during normal times, typically, it is when there is no temperature change in the liquid inside the circulation flow path.

[0007] With such a configuration, when the flow path of the connection pipe is blocked by the shut-off device, it is possible to prevent the diffusion of dissolved oxygen inside the liquid.

[0008] Further, the piping system according to the second aspect of the present disclosure is the piping system according to the first aspect of the present disclosure, wherein the shut-off device includes a first pipe, a second pipe arranged in parallel with the first pipe, a first check valve provided in the first pipe so as to permit the liquid inside the first pipe to flow from the side of the circulation pipe toward the side of the expansion tank, and a second check valve provided in the second pipe so as to permit the liquid inside the second pipe to flow from the side of the expansion tank toward the side of the circulation pipe.

[0009] With such a configuration, when there is no expansion or contraction of the retained liquid during normal times, the check valve blocks the flow path of the connection pipe to prevent the diffusion of dissolved oxygen inside the liquid, and when expansion or contraction of the retained liquid occurs, the entry and exit of the liquid to and from the expansion tank can be permitted.

[0010] Further, the piping system according to the third aspect of the present disclosure is the piping system according to the first aspect or the second aspect of the present disclosure, wherein the shut-off device includes an on-off valve that opens and closes the flow path of the connection 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 the pressure, and a first control device that opens the on-off valve when the amount of change in the value detected by the detector within a predetermined period reaches a predetermined value.

[0011] With such a configuration, during normal times, the flow path of the connecting pipe is blocked by the on-off valve to prevent the diffusion of dissolved oxygen inside the liquid. When the internal pressure changes, the on-off valve can be opened to allow the liquid to flow in and out of the expansion tank.

[0012] Moreover, the piping system according to the fourth aspect of the present disclosure is the piping system according to any one of the first to third aspects of the present disclosure. The shut-off device includes an on-off valve that opens and closes the flow path of the connecting pipe. 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 a predetermined period at least during the operation of the heat source device.

[0013] With such a configuration, when there is no temperature difference in the liquid inside the circulation flow path during normal times, the flow path of the connecting pipe is blocked by the on-off valve to prevent the diffusion of dissolved oxygen inside the liquid. When a temperature change of the liquid can occur due to the operation of the heat source device, the on-off valve can be opened to allow the liquid to flow in and out of the expansion tank.

Advantages of the Invention

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

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0016] Hereinafter, embodiments will be described with reference to the drawings. In the drawings, members that are the same or corresponding to each other are denoted by the same or similar reference numerals, and redundant descriptions are omitted.

[0017] First, referring to FIG. 1, a piping system 1 according to the first embodiment will be described. FIG. 1 is a schematic system diagram of the piping system 1. Generally speaking, the piping system 1 is a semi-closed system in which an open expansion tank 21 (hereinafter simply referred to as "expansion tank 21") is connected to a closed-circuit circulation pipe 10. Here, the semi-closed system is a system in which the circulating liquid line is in contact with air only at the expansion tank 21. In a semi-closed system, there is almost no flow of liquid between the circulation pipe and the expansion tank, and the circulating liquid hardly comes into direct contact with air. As concepts contrasted with the semi-closed system, there are an open system and a closed system. The open system is a system in which there is a part of the circulating liquid line that is open to air such as a heat storage tank, and the area in contact with air is larger than that of the semi-closed system. In the open system, since the circulating liquid passes through the part open to air such as the heat storage tank, there are many opportunities for direct contact with air. The closed system is typically a system in which a closed expansion tank is connected and there is no part in contact with air in the circulating liquid line.

[0018] In open and semi-closed systems having a surface in contact with air, the presence of dissolved oxygen, which can cause corrosion of pipes and the like, has been regarded as a problem. Although both open and semi-closed systems have a surface in contact with air, in the semi-closed system, unlike the open system, since the circulating liquid hardly comes into direct contact with air, the diffusion of dissolved oxygen may be limited. That is, in the semi-closed system, since convection in the pipe connecting the expansion tank and the circulation pipe is unlikely to occur, it is also conceivable that dissolved oxygen does not diffuse into the liquid in the circulation pipe unless the liquid that has come into contact with air in the expansion tank enters the circulation pipe.

[0019] To verify the above inference, the inventors conducted verification in the following manner to determine whether dissolved oxygen diffuses even when there is no liquid movement in a semi-closed system. First, a VP pipe with a diameter of 50A was installed vertically with a length of 4500 mm. An open expansion tank was simulated by installing a water tank with dimensions of 400 mm × 400 mm × 400 mm at the upper part of this vertical pipe, and a circulation pipe was installed at the lower part of the vertical pipe. Then, taking the lower part of the vertical pipe (the connection part with the circulation pipe) as the reference point, dissolved oxygen meters (fluorescent type) were installed at positions 0 mm, 500 mm, 2500 mm, and 4500 mm above the reference point respectively (therefore, the upper three dissolved oxygen meters are spaced 2000 mm apart). This experimental equipment was filled with water, and the dissolved oxygen concentration was measured. As a result of the measurement, as time passed, an increase in oxygen concentration was observed in order from the dissolved oxygen meter closest to the water tank. In the uppermost dissolved oxygen meter (located 4500 mm above the reference point), the oxygen concentration started to increase shortly after the start of measurement, while in the lowermost dissolved oxygen meter (located at the 0 mm position from the reference point), the oxygen concentration started to increase 7 days after the start of measurement. From this, it was confirmed that dissolved oxygen moves through a pipe with a diameter of 50A and a length of about 5 m in about 7 days. In addition, the dissolved oxygen concentration in the pipe increased over time and reached near the saturated oxygen concentration in about 107 days. The saturated oxygen concentration here is the theoretical value calculated from the value of the water temperature at the 0 mm position from the reference point using the table of dissolved oxygen in water in JIS K0102.

[0020] As a result of the verification, it was found that dissolved oxygen diffuses even when stopped (when there is no water movement). On the other hand, considering the actual operation of the piping system, it is considered that temperature changes, that is, changes in the density of the retained liquid (expansion and / or contraction), mostly occur during a certain period after the start of operation of the heat source device or a certain period after the stop of operation. Based on these points, the inventors came up with a piping system capable of suppressing the diffusion of dissolved oxygen. First, the configuration of piping system 1 will be described below. Piping system 1 includes a circulation pipe 10, an expansion tank 21, a connection pipe 23, and a shut-off device 30.

[0021] In this embodiment, the circulation pipe 10 includes a primary-side pipe 11, a secondary-side pipe 15, a supply header 18, and a return header 19. The primary-side pipe 11 is provided with a heat source device 12 such as a refrigerator or a cold and hot water generator, and a pump 13. The primary-side pipe 11 is a pipe that guides the chilled and hot water CH as a liquid from the return header 19 to the heat source device 12 by the operation of the pump 13, and guides the chilled and hot water CH whose temperature has been adjusted in the heat source device 12 to the supply header 18. The secondary-side pipe 15 is provided with air conditioning equipment 16 such as an air handling unit or a fan coil unit. The secondary-side pipe 15 is a pipe that guides the chilled and hot water CH from the supply header 18 to the air conditioning equipment 16, and guides the chilled and hot water CH whose temperature has changed due to heat utilization in the air conditioning equipment 16 to the return header 19. In this embodiment, the secondary-side pipe 15 is provided with three systems of secondary-side pipes 15A, 15B, and 15C, and different or the same types of air conditioning equipment 16A, 16B, and 16C are arranged therein. The number of systems constituting the secondary-side pipe 15 is not limited to three, and may be one or 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 to be started and stopped and the control amount adjusted according to commands from the control device.

[0022] Due to the operation of the pump 13, the circulation pipe 10 forms a circulation flow path through which the chilled and 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. The circulation pipe 10 has no part that comes into contact with air during the circulation of the chilled and hot water CH, and is a sealed flow path. In this embodiment, the pump 13 provides the lift required for the chilled and hot water CH to flow through the secondary-side pipe 15, but a secondary pump (not shown) may be installed in each of the secondary-side pipes 15A, 15B, and 15C of each system. By providing a secondary pump (not shown), it becomes possible to supply the chilled and hot water CH with a flow rate corresponding to the load of each air conditioning equipment 16A, 16B, and 16C to each air conditioning equipment 16A, 16B, and 16C by inverter control. Also, in this case, it is sufficient for the pump 13 to have a lift capable of transporting the chilled and 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 a 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 the present embodiment, the connection pipe 23 is connected to the circulation pipe 10 at the return header 19. By using an open-type expansion tank as the expansion tank 21, when pressure fluctuations occur due to the expansion or contraction of the cold and hot water CH inside the circulation pipe 10, the pressure fluctuations are released to the atmosphere, so the reference pressure, which is the atmospheric pressure, does not fluctuate, and the controllability is excellent. Further, 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 it is preferably installed more than 1 m above the highest position of the circulation pipe 10. As the expansion tank 21, a known open-type expansion tank can be used, and typically, an overflow pipe (not shown) and a makeup water pipe (not shown) are connected. Below the liquid level of the expansion tank 21, including the inside of the connection pipe 23 and the circulation pipe 10, is filled with a liquid (water in the present embodiment). Therefore, the piping system 1 is not in contact with the atmosphere (air) except for the liquid level of the expansion tank 21.

[0024] The shut-off device 30 is a device capable of shutting off the flow path inside the connection pipe 23. The shut-off device 30 is provided in the connection pipe 23. The significance of the shut-off device 30 shutting 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 the aforementioned dissolved oxygen. On the other hand, when expansion or contraction occurs in the cold and hot water CH inside the circulation pipe 10, it is required to release the shut-off of the internal flow path of the connection pipe 23 in order to release the pressure fluctuations at that time. Based on these points, the shut-off device 30 in the present embodiment has the following configuration.

[0025] The shut-off 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 arranged in the first pipe 31 in a direction that allows the flow of liquid from the side of the circulation pipe 10 to the side of the expansion tank 21 and blocks the flow in the reverse direction. A second check valve 34 is provided in the second pipe 32. The second check valve 34 is arranged in the second pipe 32 in a direction that allows the flow of liquid from the side of the expansion tank 21 to the side of the circulation pipe 10 and blocks the flow in the reverse direction. In the shut-off 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 shut-off device 30 configured in this way is inserted and arranged in the connection pipe 23, so that one of the connection parts of the first pipe 31 and the second pipe 32 is connected to the connection pipe 23 on the side of the circulation pipe 10, and the other is connected to the connection pipe 23 on the side of the expansion tank 21. The shut-off device 30 is preferably provided at a position as far as possible from the circulation pipe 10, preferably provided on the side of the expansion tank 21 at least more than half of the total length of the connection pipe 23, and more preferably provided within 1 / 10 of the total length of the connection 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 after the flow of the cold and hot water CH inside the circulation pipe 10 has stopped, and the temperature of the cold and hot water CH is about the same as the ambient temperature (normal time), the water inside the connection pipe 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 shut-off device 30 are in a closed state. In this state, since the water surface of the expansion tank 21 is in contact with the air, based on the verification result of the diffusion state of the dissolved oxygen described above, the oxygen in the air dissolves in the water from the water surface of the expansion tank 21 and tends to diffuse toward the circulation pipe 10 over time. However, in the piping system 1 according to the present embodiment, since the flow path of the connection pipe 23 is blocked by the first check valve 33 and the second check valve 34, the diffusion of the dissolved oxygen can be prevented.

[0027] When the pump 13 is started, the cold and hot water CH inside the circulation pipe 10 flows, and the flowing cold and hot water CH circulates inside the circulation pipe 10. The cold and hot water CH circulating inside the circulation pipe 10 typically does not enter or exit the connection pipe 23 when there is no temperature change, so the first check valve 33 and the second check valve 34 remain closed. Therefore, when the cold and hot water CH is circulating in the circulation pipe 10 but there is no entry or exit to the connection pipe 23, the diffusion of dissolved oxygen from the expansion tank 21 into the circulation pipe 10 can be prevented.

[0028] After that, when the heat source device 12 operates and the chilled and hot water CH circulating inside the circulation pipe 10 is heated in the heat source device 12, for example, the chilled and hot water CH with an increased temperature flows out from the heat source device 12. The chilled and hot water CH flowing out from the heat source device 12 is heated to a temperature suitable for use in the air-conditioning equipment 16. The temperature of the chilled and hot water CH flowing out from the air-conditioning equipment 16 and flowing into the heat source device 12 is lower than the temperature of the chilled and hot water CH flowing out from the heat source device 12 by the amount of heat utilized in the air-conditioning equipment 16, but generally higher than the ambient environmental temperature. Therefore, when the heat source device 12 starts the heating operation, the temperature of the chilled and hot water CH circulating in the circulation pipe 10 rises. The chilled and hot water CH circulating in the circulation pipe 10 expands as the temperature rises. The expanded chilled and hot water CH flows into the connection pipe 23 from the circulation pipe 10. When the chilled and hot water CH flows into the connection pipe 23, a force acts to lift the chilled and hot water CH inside the connection pipe 23 upward. Due to this force, the first check valve 33 opens, and the water moves toward the expansion tank 21, pushing up the water surface of the expansion tank 21. When the inflow of the expanded chilled and hot water CH in the circulation pipe 10 into the connection pipe 23 is completed, the movement of the water inside the connection pipe 23 and the expansion tank 21 stops, and the first check valve 33 closes. During the movement of the water in this direction, the second check valve 34 remains closed throughout. Thus, since the shut-off device 30 is provided with the first check valve 33, it can move the necessary amount of water attempting to move from the side of the circulation pipe 10 to the side of the expansion tank 21. Also, when the temperature of the chilled and hot water CH circulating in the circulation pipe 10 stabilizes during the heating operation of the heat source device 12 and the movement of the 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.

[0029] Thereafter, when the heat source device 12 stops and the heating of the chilled and hot water CH circulating inside the circulation pipe 10 ceases, the temperature of the chilled and hot water CH circulating inside the circulation pipe 10 gradually decreases and approaches the ambient environmental temperature. The chilled and hot water CH circulating in the circulation pipe 10 contracts as the temperature decreases. The amount of chilled and hot water CH corresponding to the contraction flows into the circulation pipe 10 from the connection pipe 23. At this time, inside the connection pipe 23, water moves from the side of the expansion tank 21 toward the side of the circulation pipe 10. At this moment, the second check valve 34 opens, and water flows through the second pipe 32. When the inflow of the chilled and hot water CH corresponding to the contraction in the circulation pipe 10 from the connection pipe 23 is completed, the movement of water inside the connection pipe 23 and the expansion tank 21 stops, and the second check valve 34 closes. When water on the side of the expansion tank 21 passes through the second check valve 34 toward the side of the circulation pipe 10 as viewed from the second check valve 34, water containing dissolved oxygen on the side of the expansion tank 21 will flow into the side of the circulation pipe 10. However, since the water passing through the second check valve 34 remains only in the amount corresponding to the contraction of the chilled and hot water CH inside the circulation pipe 10, the diffusion of dissolved oxygen flowing into the side of the circulation pipe 10 can be minimized. When water on the side of the expansion tank 21 passes through the second check valve 34 toward the side of the circulation pipe 10, the first check valve 33 remains closed throughout. Thus, since the shut-off device 30 includes the second check valve 34, it can retain the water attempting to move from the side of the expansion tank 21 to the side of the circulation pipe 10 in the necessary amount, and can suppress the diffusion of dissolved oxygen from the expansion tank 21 to the circulation pipe 10. Also, when the temperature of the chilled and hot water CH circulating in the circulation pipe 10 stabilizes after the heat source device 12 stops and the movement of water inside the connection pipe 23 stops, the first check valve 33 and the second check valve 34 close, and the diffusion of dissolved oxygen from the expansion tank 21 to the circulation pipe 10 can be prevented. Note that the pump 13 typically stops after performing necessary residual operation after the heat source device 12 stops.

[0030] As described above, according to the piping system 1 according to the present embodiment, since the shut-off device 30 is provided, when there is no inflow or outflow of the chilled and hot water CH between the circulation pipe 10 and the connection pipe 23, the diffusion of dissolved oxygen from the expansion tank 21 into the circulation pipe 10 can be prevented. Further, since the shut-off device 30 has a first check valve 33 that allows the flow of the liquid from the circulation pipe 10 side to the expansion tank 21 side and blocks the reverse direction, the chilled and hot water CH expanded inside the circulation pipe 10 can be moved outside the circulation pipe 10 without delay as needed. Further, since the shut-off device 30 has a second check valve 34 that allows the flow of the liquid from the expansion tank 21 side to the circulation pipe 10 side and blocks the reverse direction, the amount of water containing dissolved oxygen flowing into the circulation pipe 10 side when the chilled and hot water CH in the circulation pipe 10 contracts can be minimized. In the above description, an example in which the heat source device 12 heats the chilled and hot water CH is shown, but it goes without saying that when the heat source device 12 cools the chilled and hot water CH, the expansion and contraction of the chilled and 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 performs a cooling operation of the chilled and hot water CH, the chilled and hot water CH contracts during the operation of the heat source device 12, and the chilled and hot water CH expands when the heat source device 12 stops. However, the action of the shut-off device 30 during the expansion and contraction of the chilled and hot water CH is as described above.

[0031] Next, with reference to FIG. 2, a piping system 2 according to the second embodiment will be described. FIG. 2 is a schematic system diagram of the piping system 2. In the present embodiment, the piping system 2 is mainly different from the piping system 1 in that a shut-off device 30A is provided in place of the shut-off device 30 (see FIG. 1), a pressure sensor 38 is provided in the supply header 18, and a control device 50 is provided.

[0032] The shut-off device 30A includes a shut-off valve 36 that opens and closes the flow path inside the connecting pipe 23 in response to a control signal from the outside. The shut-off valve 36 is a valve that can allow liquid to flow in both directions when open. As its type, a known valve such as a gate valve, ball valve, butterfly valve, etc. can be adopted in consideration of the diameter of the connecting pipe 23 to be installed and the type of fluid flowing inside the connecting pipe 23. The shut-off valve 36 has an actuator that moves the valve body between an open position and a closed position, and the actuator is configured to move the valve body in response to a control signal from the outside. Similar to the shut-off device 30 (see FIG. 1), the shut-off device 30A (shut-off valve 36) is preferably provided at a position as far as possible from the circulation pipe 10 (a position as close as possible to the expansion tank 21).

[0033] The pressure sensor 38 is a device that mainly 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 can output the detected pressure to the outside as a signal. In the present embodiment, the pressure sensor 38 is provided in the forward header 18 that constitutes a part of the circulation pipe 10. However, it may be provided in a part 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 that communicates with the inside of the circulation pipe 10 and is affected by the pressure fluctuation inside the circulation pipe 10, and indirectly detect the pressure inside the circulation pipe 10. Or, a temperature sensor that directly detects the temperature of the cold and hot water CH that affects the pressure fluctuation 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 cold and 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 via a communication line (wired or wireless; the same applies hereinafter) and is configured to be able to control the startup and shutdown of the heat source device 12. Further, the control device 50 is connected to the pump 13 via a communication line, can control the startup and shutdown of the pump 13, and is configured to be able to adjust the discharge flow rate of the pump 13 when the pump 13 has an inverter. Also, the control device 50 is connected to the on-off valve 36 via a communication line and is configured to be able to control the opening and closing operation of the on-off valve 36. Moreover, the control device 50 is connected to the pressure sensor 38 via 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 has a first control unit 51 and a second control unit 52. The first control unit 51 is a part that controls the on-off valve 36 to open when the change amount of the value detected by the pressure sensor 38 in a predetermined period reaches a predetermined value, and corresponds to the first control device. Here, the "predetermined period" is typically preferably set as the period during which the temperature of the chilled and hot water CH accompanying the operation of the heat source device 12 appears in the change of the internal pressure of the circulation pipe 10, and may be, for example, several minutes to several tens of minutes or several hours. Also, the "predetermined value" is the difference in values when the internal pressure of the circulation pipe 10 when the on-off valve 36 is closed fluctuates to an extent that it is preferably released to the outside. For example, it is the amount of change in pressure where there is a risk of damage to the circulation pipe 10 if the fluctuating pressure is not released to the outside.

[0036] The second control unit 52 controls the on-off valve 36 such that the on-off valve 36 is closed when the cold and hot water CH inside the circulation pipe 10 is at a temperature substantially equal to the ambient temperature, and the on-off valve 36 is closed when a temperature change has occurred or may occur. As a case where the cold and hot water CH inside the circulation pipe 10 becomes a temperature substantially equal to the ambient temperature, typically, it includes the period from after a predetermined time has elapsed after the heat source device 12 stops until the heat source device 12 starts up. The predetermined time here is typically the time required for the temperature of the cold and hot water CH inside the circulation pipe 10 to become substantially equal to the ambient temperature after the heat source device 12 stops. The temperature substantially equal to the ambient temperature is intended to include not only the case where it is equal to the ambient temperature, but also the difference from the ambient temperature to such an extent that the pressure fluctuation inside the circulation pipe 10 due to the temperature difference from the ambient temperature does not have an adverse effect (such as damage) on the circulation pipe 10. As a case where a temperature change has occurred in the cold and hot water CH inside the circulation pipe 10, typically, it includes the period until a predetermined period elapses after the heat source device 12 is started up, and the period until the above-mentioned predetermined time elapses after the heat source device is stopped. The predetermined period is typically the time required for the cold and hot water CH supplied by the heat source device 12 to reach the target temperature after the heat source device 12 is started up. In this way, the second control unit 52 closes the on-off valve 36 when the cold and hot water CH inside the circulation pipe 10 is at a temperature substantially equal to the ambient temperature, and controls to open the on-off valve 36 during at least the predetermined period during the operation of the heat source device 12, and corresponds to the second control device.

[0037] In the present embodiment, the first control unit 51 and the second control unit 52 are shown as separate bodies distinguished by their control functions for convenience of explanation, but typically, the two are integrally configured, or they may be physically separated and configured. In the present embodiment, the shut-off device 30A, the pressure sensor 38, and the control device 50 have been described so far. However, since the configurations of the piping system 2 other than the above are the same as those of the piping system 1 (see FIG. 1), duplicate explanations are omitted.

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

[0039] When the heat source device 12 is activated 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 is opened, and the circulation pipe 10 and the expansion tank 21 communicate with each other. As a result, even if the temperature of the cold and hot water CH supplied from the heat source device 12 changes from the ambient temperature due to the operation of the heat source device 12, causing expansion or contraction of the cold and hot water CH, it 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 when a predetermined period has elapsed after opening the on-off valve 36 (after the heat source device 12 is activated). By the time a predetermined period has elapsed after the heat source device 12 is activated, usually, the cold and hot water CH supplied from the heat source device 12 will stabilize at the target temperature, and the temperature change will disappear or, even if there is a temperature change, it will not have an adverse effect on the structure of the circulation pipe 10. For this reason, in the present embodiment, when the temperature change of the cold and hot water CH supplied when the heat source device 12 is in steady operation has substantially disappeared (normal time), the on-off valve 36 is closed to prevent the diffusion of dissolved oxygen from the expansion tank 21 into the circulation pipe 10.

[0041] During the steady operation of the heat source device 12, the temperature of the chilled and hot water CH circulating inside the circulation pipe 10 may vary due to fluctuations in the heat load to be processed in the air-conditioning equipment 16 or other factors. When the temperature of the chilled and hot water CH inside the circulation pipe 10 changes and expands or contracts, this phenomenon appears in the detected value of the pressure sensor 38. When the change amount of 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. By doing so, the pressure fluctuation generated inside the circulation pipe 10 can be released to the expansion tank 21. After that, when the temperature of the chilled and hot water CH circulating inside the circulation pipe 10 stabilizes, the first control unit 51 may close the on-off valve 36 to prevent the diffusion of dissolved oxygen from the expansion tank 21 to the circulation pipe 10. The determination of whether the temperature of the chilled and hot water CH circulating inside the circulation pipe 10 has stabilized may be made based on the detected value of a temperature sensor (not shown) provided in the circulation pipe 10, or may be made depending on whether a time obtained in advance based on the data during the trial operation has elapsed.

[0042] When the heat source device 12 stops due to 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 stops, the temperature of the chilled and hot water CH inside the circulation pipe 10 changes so as to approach the ambient temperature from the target temperature, and at this time, it is accompanied by contraction or expansion. However, since the flow path of the connection pipe 23 is open, the contraction or expansion can be released to the expansion tank 21. The second control unit 52 closes the on-off valve 36 after a predetermined time has elapsed since the heat source device 12 stopped, so as to prevent the diffusion of dissolved oxygen from the expansion tank 21 to the circulation pipe 10.

[0043] As described above, when expansion or contraction of the cold and warm water CH inside the circulation pipe 10 does not occur, the on-off valve 36 can be closed to prevent diffusion of dissolved oxygen from the expansion tank 21 into the circulation pipe 10. On the other hand, when expansion or contraction of the cold and warm water CH inside the circulation pipe 10 is occurring or may occur, the on-off valve 36 can be opened to release pressure fluctuations inside the circulation pipe 10 to the expansion tank 21. Thus, also in the piping system 2, similar to the piping system 1 (see FIG. 1), while releasing pressure fluctuations inside the circulation pipe 10 to the expansion tank 21, diffusion of dissolved oxygen from the expansion tank 21 into the circulation pipe 10 can be suppressed.

[0044] In the example of the piping system 2 described above, it was assumed that the control device 50 has the first control unit 51 and the second control unit 52. However, when it is not necessary to perform control by the second control unit 52, the second control unit 52 may not be provided. On the other hand, when it is not necessary to perform control by the first control unit 51, 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. When configured in this way, even when the first check valve 33 and / or the second check valve 34 do not fully close due to garbage jamming or the like, it is possible to suppress diffusion of the dissolved oxygen in the expansion tank 21 into the circulation pipe 10 due to the on-off valve 36 being closed.

[0046] In the above description, it was assumed that the liquid circulating inside the circulation pipe 10 is the cold and warm water CH, but it may be a liquid other than the cold and warm water CH such as brine.

Explanation of Reference Numerals

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

Claims

1. A closed circulation passage is formed, including a circulation pipe through which a liquid circulates in the circulation passage, an open expansion tank, a connection pipe connecting the circulation pipe and the expansion tank, and a shut-off device that closes the flow path of the connection pipe during normal times and opens it when the liquid circulating in the circulation passage can expand or contract. A piping system.

2. The shut-off device includes 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 side of the circulation pipe to the side of the expansion tank, and a second check valve provided in the second pipe to allow the liquid inside the second pipe to flow from the side of the expansion tank to the side of the circulation pipe. It has The piping system according to Claim 1.

3. The shut-off device includes an on-off valve that opens and closes the flow path of the connection 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 the pressure, and a first control device that opens the on-off valve when the change amount of the value detected by the detector within a predetermined period reaches a predetermined value. The piping system according to Claim 1 or Claim 2.

4. The shut-off device includes an on-off valve that opens and closes the flow path of the connection 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 during the operation of at least the heat source device. The piping system according to Claim 1 or Claim 2.

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