Open piping system and pressure control method

Abstract

To provide an open type piping system and a pressure control method that can suitably perform energy-saving operation.SOLUTION: An open type piping system 1 comprises: a pipe 3 connected to a liquid storage tank (heat storage tank 2) for storing liquid; a load device (air conditioner 4) connected to the pipe 3; a pump 5 arranged upstream of the air conditioner 4, and for circulating the liquid through the pipe 3 and the heat storage tank 2; a back pressure control valve 6 arranged downstream of the air conditioner 4; and a control device 7 comprising an opening degree adjustment unit 7a for adjusting the opening degree of the back pressure control valve 6. The opening degree adjustment unit 7a adjusts the opening degree of the back pressure control valve 6 so that an internal pressure in at least a portion of an uppermost part 3a of the pipe 3 becomes a negative pressure during normal operation of the pump 5.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an open piping system and a method for controlling pressure. [Background technology]

[0002] In piping systems that carry liquids such as refrigerants for air conditioners (AHUs), domestic water, or machine cooling water, and in which the end of the piping is open to a liquid storage tank, a mechanical self-operating water fall prevention valve can be installed on the return piping to the liquid storage tank. The water fall prevention valve prevents water in the return piping from falling into the liquid storage tank and escaping from the piping when the pump is stopped, and is configured to automatically close when the pressure in the piping drops. Air entering the piping can also cause the piping to rust.

[0003] In addition, to prevent air from entering the piping from the outside, it is common to select a pump that can create positive pressure inside the piping, and then operate the pump at a water supply pressure that is increased by the actual head so that positive pressure is always maintained inside the piping, thereby supplying liquid into the piping. However, with conventional self-operating water fall prevention valves, the set pressure (pressure loss) is added to the actual head, which means that the pump's water supply pressure needs to be increased by the amount of the set pressure, which hinders energy-saving operation.

[0004] It is also known that in a piping system with an actual pump head, creating a negative pressure in the piping reduces the pump's required pump head. For example, Patent Document 1 describes the use of an automatic air vent valve or, in addition, a vacuum pump to create a negative pressure inside the piping. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-313059 Summary of the Invention [Problem to be solved by the invention]

[0006] However, if the pressure inside the pipe becomes close to an absolute vacuum, adverse effects such as boiling of the liquid inside the pipe may occur, making it impossible to perform energy-saving operation in an optimal manner. The present invention has been made in consideration of the above-mentioned problems, and aims to provide an open piping system and a pressure control method in an open piping system that can perform energy-saving operation by performing pressure control. [Means for solving the problem]

[0007] The open piping system of the present invention includes a pipe connected to a liquid storage tank that stores a liquid, a loading device connected to the pipe, a pump that is arranged upstream of the loading device and circulates the liquid between the pipe and the liquid storage tank, a back pressure control valve that is arranged downstream of the loading device, and a control device having an opening adjustment unit that adjusts the opening of the back pressure control valve, wherein the opening adjustment unit adjusts the opening of the back pressure control valve so that the internal pressure in at least a part of the uppermost part of the pipe during normal operation of the pump is A pressure lower than atmospheric pressure The opening of the back pressure control valve is adjusted to create a negative pressure.

[0008] The pressure control method of the present invention is a pressure control method in the open piping system, wherein the control device includes a pump output adjustment unit that controls the rotation speed of the pump while creating a negative pressure in at least a part of the uppermost part of the piping so as to offset a part of the actual head during normal operation of the pump, and the control device adjusts the pressure in the piping by controlling in conjunction with the water supply pressure of the pump adjusted by the pump output adjustment unit and the back pressure adjusted by the opening adjustment unit. [Effects of the Invention]

[0009] According to the open piping system and pressure control method of the present invention, by adjusting the opening of the back pressure control valve and making the internal pressure of at least a part of the top of the piping negative during normal pump operation, it is possible to reduce the required pump head and perform energy-saving operation in an optimal manner. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic explanatory diagram showing an open piping system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a functional block diagram illustrating a control device and related devices. [Figure 3] FIG. 1 is a pressure diagram showing the pressure and head for each position in the piping when the pump is started and when air is bled from the piping before the pump is stopped. [Figure 4] FIG. 4 is a pressure diagram showing the pressure and head for each position in the piping when the pump is stopped. [Figure 5] FIG. 2 is a pressure diagram showing the pressure and head for each position in the piping when the pump is operating. [Figure 6] FIG. 1 is a pressure diagram showing the pressure and head inside the piping when air is bled while the pump is operating. [Figure 7] FIG. 10 is a diagram illustrating the arrangement of pumps according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0011] An open piping system 1 and a pressure control method according to an embodiment of the present invention will be described below with reference to the drawings. The embodiment described below is merely an example to facilitate understanding of the present invention, and is not intended to limit the present invention. In other words, the system, types of devices, number of devices, etc. described below may be changed or improved without departing from the spirit of the present invention, and the present invention naturally includes equivalents thereof. In addition, in all the drawings, like components are given like reference numerals, and redundant explanations are omitted as appropriate. Note that the drawings are for explaining the present invention, and the dimensions, ratios, shapes, etc. of each part shown in the drawings can be changed as appropriate within the scope of the spirit of the present invention.

[0012] <Summary of the Invention> First, an overview of the present invention will be described mainly with reference to Figures 1 and 2. Figure 1 is a schematic explanatory diagram showing an open piping system 1 according to this embodiment. Figure 2 is a functional block diagram explaining a control device 7 and related devices.

[0013] The open piping system 1 includes a pipe 3 connected to a liquid storage tank (thermal storage tank 2) that stores liquid, a load device (in this embodiment, an air conditioner 4 (AHU)) connected to the pipe 3, a pump 5 arranged upstream of the air conditioner 4 and circulating the liquid through the pipe 3 and the thermal storage tank 2, a back pressure control valve 6 arranged downstream of the air conditioner 4, and a control device 7 having an opening adjustment unit 7a that adjusts the opening of the back pressure control valve 6. The opening adjustment unit 7a is characterized in that it adjusts the opening of the back pressure control valve 6 so that the internal pressure in at least a part of the uppermost part 3a of the pipe 3 becomes negative during normal operation of the pump 5.

[0014] The term "liquid storage tank" is not limited to those that store cooling water or hot water, but also includes those that store refrigerants other than water, such as water for daily use, industrial water (cooling water), and water for firefighting. "Load equipment" refers to equipment that uses liquid or liquid energy, and is not limited to thermal load equipment that receives and consumes thermal energy, such as heat exchangers and air conditioners, but also includes various equipment that receives and consumes mechanical energy, such as machine tools. The pipe 3 includes a low region and a high region in the direction of gravity, and the liquid is pumped from the low region to the high region by the pump 5. The "top" of the pipe 3 refers to the highest region in the direction of gravity in the pipe 3, but has a certain range in the height direction. "During normal operation" refers to the operating period excluding immediately after starting, immediately before stopping, and after stopping of the pump 5, and refers to the period during which the pressure in the pipe 3 is stable and does not substantially change over time. Whether or not air bleeding is possible during normal operation is optional. Also, "negative pressure" refers to a pressure lower than atmospheric pressure, that is, a negative pressure in terms of gauge pressure.

[0015] According to the above configuration, during normal operation of the pump, the opening of the back pressure control valve is adjusted to make the internal pressure of at least a part of the top of the piping negative, thereby reducing the required pump head compared to when positive pressure is used, allowing the system to function in an energy-saving manner.

[0016] <Configuration of each part> Next, the configuration of each part of the open piping system 1 will be described. The open piping system 1 includes a heat storage tank 2, a pipe 3 having both open ends disposed in the water of the heat storage tank 2, an air conditioner 4 having an internal coil (not shown) that constitutes the pipe 3, a pump 5 provided in the pumping pipe of the pipe 3, a back pressure control valve 6 provided in the return pipe of the pipe 3, and a control device 7 having an opening adjustment unit 7a shown in FIG. 2. The open piping system 1 according to this embodiment also includes a pressure gauge 12 shown in FIG.

[0017] The back pressure control valve 6 is provided in the return pipe and controls the pressure in the pipe 3 in conjunction with the discharge pressure of the pump 5, and also has a function to prevent water from falling. When the pump 5 is in operation, the back pressure control valve 6 is controlled by the control device 7 to be in the open state, preventing the water from falling and thereby preventing unnecessary pressure loss. The back pressure control valve 6 also has the function of preventing unstable control by the control device 7 due to changes in the pipe resistance in the return pipe caused by changes in the flow rate.

[0018] In this way, the back pressure control valve 6 is opened under the control of the control device 7, and therefore pressure loss can be reduced compared to a mechanical valve that requires a pressure above a predetermined level (for example, 5 mAq) to open. Note that the back pressure control valve 6 is not an ON / OFF valve that has only two states, fully closed and fully open, but is configured to be controllable so as to open proportionally in accordance with the pressure detected by the pressure gauge 12. Therefore, the water supply pressure of the pump 5 can be reduced, which enables the pump 5 to be operated in an energy-saving manner.

[0019] The open piping system 1 further includes an air vent valve 9 provided at the uppermost part 3a of the piping 3. A pressure gauge 12 (compound pressure gauge) is installed downstream of the air vent valve 9 (and further downstream of the air conditioner 4). The air vent valve 9 in this embodiment is an automatic air vent valve with an intake-side check function, but a manually operated valve is also acceptable as it is less likely to malfunction, and both may be provided. The load equipment (air conditioner 4) is disposed at least at the uppermost part 3a of the piping 3. The location where the air vent valve 9 is provided (point B in Figure 1) is upstream of the air conditioner 4 and is at positive pressure during normal operation of the pump 5, as shown at A3 in Figure 5 and described below. According to the above configuration, the area where the air vent valve 9 is provided is under positive pressure, so that air can be suitably vented from inside the pipe 3. In a system in which the pump 5 can be stopped periodically, the air vent valve 9 may be provided downstream of the air conditioner 4 (load device).

[0020] In particular, it is preferable that the portion of the piping 3 where the air vent valve 9 is installed is made thicker than other portions, forming a Torii-style piping. The air vent valve 9 formed in this manner can more reliably capture air.

[0021] For example, the open piping system 1 according to this embodiment includes an "other pump" (volumetric pump 11 in this embodiment) that has a lower flow rate and a higher head than the pump 5, between the pump 5 and the uppermost portion 3a of the piping 3. The volumetric pump 11 is attached to a bypass piping that bypasses the pump 5. Furthermore, a check valve 10 is provided on the discharge side of each of the pump 5 and the volumetric pump 11. The check valve 10 prevents the liquid (water) discharged from the pump 5 from flowing into the volumetric pump 11, and also prevents the liquid discharged from the volumetric pump 11 from flowing into the pump 5.

[0022] The "other pump" other than the pump 5 may be, for example, a syringe-shaped volumetric pump 11, or a pump having the same configuration as the pump 5 but with a different water-transporting capacity. According to the above configuration, by additionally providing another pump (volumetric pump 11) in the open piping system 1, a high pump head can be achieved for bleeding the piping 3. For example, the volumetric pump 11 may be provided so as to be detachable from the piping 3. If the pump 5 alone is sufficient to bleed air from the piping 3, the open piping system 1 does not necessarily need to include the volumetric pump 11. Furthermore, a plurality of pumps 5 and a plurality of volumetric pumps 11 may be provided.

[0023] <Operation at each stage> Next, details of the operation of the open piping system 1 at each stage will be described with reference to FIGS. 3 to 6 in addition to FIGS. FIG. 3 is a pressure diagram showing the pressure and head at each position in the pipe 3 when the pump 5 is started and when the pipe 3 is bled (when the back pressure control valve 6 is fully closed) before the pump 5 is stopped. FIG. 4 is a pressure diagram showing the pressure and head at each position in the pipe 3 when the pump 5 is stopped. FIG. 5 is a pressure diagram showing the pressure and head at each position in the pipe 3 when the pump 5 is operating. FIG. 6 is a pressure diagram showing the pressure and head inside the pipe 3 when air is bled while the pump 5 is operating.

[0024] In this embodiment, the pump 5 and the back pressure control valve 6 are located at a position higher than the water surface in the heat storage tank 2, which is subjected to atmospheric pressure. Therefore, in Figures 3 to 6, a horizontal pressure change occurs from a portion where the head is higher than 0 m, and the area below the pump 5 and the back pressure control valve 6 is open, resulting in a negative pressure.

[0025] [When filled with water] When filling the inside of the pipe 3 with liquid (water in this embodiment), water is supplied from directly above the pump 5, and then the pump 5 is operated to fill the inside of the pipe 3 with water stored in the heat storage tank 2. By filling the pipe 3 from below in this way, air can be pressed from below by the high-density water, compared to a method in which the inside of the pipe 3 is filled with water from the top 3a of the pipe 3, and air can be removed from the inside of the pipe 3 more effectively.

[0026] Pump 5 applies water pressure to the inside of pipe 3, making it easier to release air from pipe 3 to the outside. In particular, air release valve 9 attached to the top 3a of pipe 3 makes it possible to efficiently release air that has accumulated in the top 3a of pipe 3 to the outside from pipe 3. Furthermore, although pump 5 has an actual head, filling the pipe with a small amount of water can reduce pipe resistance and keep the pump head small.

[0027] [Air bleeding when starting the pump] When bleeding air at the start of the pump 5, the back pressure control valve 6 (two-way valve) is kept fully closed, and the inverter output of the pump 5 is gradually increased to increase the water supply pressure so that the pressure gauge 12 measuring the pressure inside the piping 3 reaches the operating pressure of the air bleeding valve 9 (the pressure at which air is released).

[0028] At this time, if the control valve 13 of the air conditioner 4 or the like is fully closed, open the control valve 13 to apply fluid pressure to the entire piping 3, thereby removing air from inside the piping 3 (including the coil, etc.). By making the pressure inside the piping 3 positive, it becomes possible to remove air from inside the piping 3.

[0029] When the pump 5 is stopped, no water flow occurs, so naturally the resistance to the water flow from the pipe 3 is zero. As soon as the pump 5 starts, the actual head is generated at 100%. If the flow rate is gradually increased from this state, the resistance of the pipe 3 will gradually increase. If the pressure gauge 12 is set to negative pressure, the pump 5 can be operated so that the increasing resistance of the pipe 3 is offset by the amount of reduction in the actual head due to the negative pressure in the pipe 3.

[0030] In other words, if the pressure in the pipe is made negative after the pump is started before the flow rate reaches 100%, the actual head will decrease, and the pump head will be smaller than in a system where the pressure in the pipe is made positive and the actual head is 100%. Furthermore, for this open piping system 1, it is possible to select a pump 5 with a small water conveyance capacity. In other words, it is possible to select a pump 5 with a water conveyance capacity lower than the total head of the open piping system 1 during rated operation of the pump 5.

[0031] Furthermore, the pump motor may be selected at 100% flow rate and 100% actual head, and the pump output adjusting unit 7b may control the water supply pressure of the pump 5 to perform energy-saving operation.

[0032] When the pump 5 is started, the pump output adjustment unit 7b gradually increases the power supply frequency of the pump 5 in conjunction with the opening adjustment unit 7a gradually increasing the opening of the back pressure control valve 6 via the pressure indicating regulator 8, thereby increasing the water supply pressure and adjusting the pressure in the piping 3, and raising the pressure in the piping to the pressure at which the air vent valve 9 operates.

[0033] The above "linked" does not necessarily mean that they operate simultaneously. Back pressure control valve 6 This means that the power supply frequency of the pump 5 is increased as the opening of the valve 11 changes. According to the above configuration, when the opening degree of the back pressure control valve 6 is increased at the start of the pump 5, air can be suitably bled from the inside of the pipe 3.

[0034] [Bleeding air before stopping the pump] In this embodiment, before stopping the pump 5, air is bled from inside the pipe 3 in the reverse order to that used when starting the pump 5. Specifically, before stopping the pump 5, the control device 7 (opening adjustment unit 7a) places the back pressure control valve 6 (two-way valve) slightly closed rather than fully closed, creating a temporary dammed state. Then, the control device 7 (pump output adjustment unit 7b) controls the pressure so that the internal pressure at the top 3a of the pipe 3 also becomes positive. If the internal pressure of the pipe 3 does not increase, the control device 7 fully closes the back pressure control valve 6, increases the inverter output of the pump 5, and creates a positive pressure inside the pipe 3, thereby discharging the air inside the pipe 3 to the outside via the air bleed valve 9, etc.

[0035] In this embodiment, when the pump 5 is started and when air is bled before the pump 5 is stopped, as shown in Fig. 3, the pressure inside the pipe 3 at the position of the pump 5 is 22 mAq, and the pressure at point A in Fig. 1, which is the top 3a of the pumping pipe of the pipe 3, is 2 mAq, as indicated by A1 in Fig. 3. The pressure at point B in Fig. 1, which is the top 3a of the return pipe of the pipe 3, is 0.5 mAq, as indicated by B1 in Fig. 3, and the pressure at the position of the back pressure control valve 6 is 18.5 mAq. The pressure difference of 1.5 mAq between A1 and B1 is the operating pressure of the air bleed valve 9.

[0036] [When the pump is stopped] When the pump 5 is stopped, the control device 7 controls the inside of the pipe 3 to maintain a positive pressure as shown in Figure 4 in order to prevent air from entering the pipe 3. The back pressure control valve 6 is fully closed by the control device 7 (opening adjustment unit 7a) when the pump 5 is stopped. In addition, the relief bypass valve is fully closed by the control device 7 when the pump 5 is stopped.

[0037] [When the pump is running] In this embodiment, when the pump is operating, as shown in Fig. 5, the pressure inside the pipe 3 at the position of the pump 5 is 21 mAq, and the pressure at point A in Fig. 1, which is the top 3a of the pumping pipe of the pipe 3, is 1 mAq, as shown by A3 in Fig. 5. The pressure at point B in Fig. 1, which is the top 3a of the return pipe of the pipe 3, is -8 mAq, as shown by B3 in Fig. 5, and the pressure at the position of the back pressure control valve 6 is 9 mAq. That is, the control device 7 controls the pressure at least at point B in the pipe 3 to become negative.

[0038] When the pump 5 is operating, the inside of the top 3a of the pipe 3 is made negative pressure, and the actual head is offset, thereby achieving energy-saving operation. By controlling the pressure gauge 12 to become negative pressure when the pump 5 is operating, the frequency of the inverter 5a of the pump 5 can be lowered, enabling energy-saving operation. For example, the control device 7 automatically measures the pressure at the top 3a of the pipe 3 using a pressure gauge 12, and automatically (or manually) changes the output setting value of the inverter control of the pump 5 and the output setting value of the back pressure control valve 6 according to the pressure.

[0039] Specifically, the control device 7 gradually reduces the inverter output of the pump 5 to reduce the water supply pressure and change the back pressure according to the opening degree of the back pressure control valve 6 so as to control the pump 5 and the back pressure control valve 6 in conjunction with each other. For example, the control device 7 can increase energy savings by fully opening the back pressure control valve 6 to minimize pressure loss, while adjusting the inverter output of the pump 5 to control the pressure at the top 3a of the pipe 3 to a set value (VWV control).

[0040] The control device 7 also adjusts the pressure at the top 3a of the pipe 3 (point B at the top end of the return pipe section in FIG. 1, point B3 in FIG. 5) to a set value (for example, -4 mAq to -8 mAq). Note that if the inside of the pipe 3 becomes close to an absolute vacuum, adverse effects such as boiling of water will occur, so care must be taken to prevent it from becoming close to an absolute vacuum (for example, -9 mAq).

[0041] In the above description, the water supply pressure of the pump 5 or the aperture of the back pressure control valve 6 is adjusted in accordance with the pressure value at the uppermost part 3a of the pipe 3, based on the pressure signal measured by the pressure gauge 12 provided at the uppermost part 3a of the pipe 3. However, the present invention is not limited to this configuration. For example, a pressure gauge may be provided at any position on the pipe 3, and whether the uppermost part 3a of the pipe 3 is under negative or positive pressure may be calculated based on the signal from a pressure gauge provided near the back pressure control valve 6, taking into account the head and pressure loss.

[0042] In the pressure control method in the open piping system 1, the control device 7 includes a pump output adjustment unit 7b shown in Fig. 2. During normal operation of the pump 5, the pump output adjustment unit 7b controls the rotation speed of the pump 5 while creating a negative pressure in at least a part of the uppermost part 3a of the piping 3 so as to offset at least a part of the actual head. The control device 7 adjusts the pressure in the piping by controlling the water supply pressure of the pump 5, which is adjusted by the pump output adjustment unit 7b, and the back pressure, which is adjusted by the opening adjustment unit 7a, in conjunction with each other.

[0043] Specifically, the control device 7 can adjust the pressure in the piping 3 by controlling the rotation speed of the pump 5 via the inverter 5a and the opening degree of the back pressure control valve 6 in the return piping (the piping section returning from the top 3a to the heat storage tank 2) in conjunction with each other in response to the pressure signal from the pressure gauge 12. According to the above configuration, by controlling the water supply pressure and the back pressure in conjunction with each other, it is possible to finely adjust the output of the pump 5 and enable energy-saving operation.

[0044] It is preferable that the control device 7 controls the internal pressure in at least a portion of the uppermost portion 3a of the pipe 3 so that when a low-temperature liquid (cold water) is passed through the pipe 3, the negative pressure is greater than when a relatively high-temperature liquid (hot water) is passed through the pipe 3.

[0045] For example, when cold water between 10 and 20 degrees Celsius is passed through the pipe 3, the set pressure at the top 3a of the pipe 3 is set to -8 mAq, and when hot water between 40 and 50 degrees Celsius is passed through the pipe 3, the set pressure at the top 3a of the pipe 3 is set to -7 mAq. According to the above configuration, by creating a larger negative pressure in at least a part of the uppermost portion 3a of the pipe 3 when cold water is flowing than when hot water is flowing, it is possible to reduce the pump head while preventing water evaporation.

[0046] When the pump 5 is operating, a portion of the piping 3 is made negative pressure for energy-saving operation, which naturally increases the possibility of air entering the piping 3 from the outside in the negative pressure portion compared to when the piping 3 is made positive pressure. If the pressure measurement value in the top 3a of the pipe 3 rises above the set negative pressure value when the pump 5 is operating, it is possible that air has entered through gaps or other areas in the pipe section that has become negative pressure. For example, if the pump 5 is operated with an initial pressure of -5 mAq at the top 3a of the pipe 3, but the pressure measured by the pressure gauge 12 at the top 3a of the pipe 3 becomes 0 mAq, this indicates that the pressure inside the pipe 3 has become the same as atmospheric pressure, and there is a high possibility that air has entered from outside.

[0047] If air gets into the piping 3 from the outside, the pressure inside the piping will try to become 0 mAq, that is, the pressure will try to equalize to atmospheric pressure, which may cause problems in the operation of the pump 5. Furthermore, the differential pressure before and after the air conditioner 4 decreases by the amount starting from the negative pressure (here, it decreases by 5 mAq, from -5 mAq to 0 mAq), so the required differential pressure cannot be obtained at the air conditioner 4 and the desired flow rate cannot be achieved.

[0048] In the summer, when the refrigerant is circulated by the pump 5, the flow is restricted, which has the effect of causing the room temperature to rise. Therefore, if the pressure in the pipe 3 fluctuates from negative pressure to 0 mAq while the pump 5 is operating, an alarm is issued externally, the power supply frequency of the pump 5 is increased, energy-saving operation in the negative pressure state is stopped, and the top 3a of the pipe 3 is controlled to maintain positive pressure.

[0049] As shown by A3 in FIG. 5, point A at the uppermost portion 3a of the pipe 3 is under positive pressure when the pump 5 is operating. However, without being limited to such settings, the control device 7 (opening adjustment unit 7a and / or pump output adjustment unit 7b) may control the pump 5 and / or the back pressure control valve 6 so that if the area at point A is at positive pressure when air is bled, it becomes negative pressure when the pump 5 is operating.

[0050] <When pump is running and air is being removed> If the pump 5 is operated 24 hours a day, the pump 5 cannot be stopped, and therefore the above-mentioned "air bleeding when starting and before stopping the pump" cannot be performed. In this case, the pump 5 must be operated while the air bleeding is performed periodically (for example, once a day).

[0051] In this embodiment, when air is bled simultaneously with pump operation, as shown in Fig. 6, the pressure inside pipe 3 at the position of pump 5 is 22 mAq, and the pressure at point A in Fig. 1, which is the top 3a of the pumping pipe of pipe 3, is 2 mAq, as shown by A4 in Fig. 6. The pressure at point B in Fig. 1, which is the top 3a of the return pipe of pipe 3, is -7 mAq, as shown by B4 in Fig. 6, and the pressure at the position of back pressure control valve 6 is 10 mAq.

[0052] In other words, when air is bled from the piping 3 while the pump 5 is operating, the pump output adjustment unit 7b of the control device 7 controls the pump head so that the pressure inside the piping 3 is higher than the pressure inside the piping during normal operation of the pump 5. Specifically, during pump operation plus air bleeding, the internal pressure in the piping 3 from the pump 5 to the back pressure control valve 6 is controlled by the control device 7 to be 1 mAq higher than during normal operation of the pump 5 shown in Figure 5. According to the above configuration, air can be removed while the pump 5 is operating.

[0053] <Energy saving effect> Conventionally, in an open piping system with a rated flow rate of 2000 L / min, a piping length of 80 m, and an actual head of 20 m, when using a mechanical water fall prevention valve (not shown) with a pressure drop of 25 mAq, a pump head of 30 kW was required to create positive pressure throughout the entire piping 3. On the other hand, according to the method of this embodiment, by varying the pressure drop of the back pressure control valve 6 from 9 to 11 mAq and creating a partial negative pressure inside the piping 3, a significant energy saving effect of 15 kW was confirmed. In other words, energy can be saved by selecting a pump 5 with a low head. Note that energy can also be saved by reducing the power output of the pump 5 without changing the pump 5.

[0054] <Modification> In the above embodiment, the pump 5 is illustrated in Fig. 1 as being provided above the water surface of the heat storage tank 2, but the present invention is not limited to this configuration. A modified example will be described with reference to Fig. 7. 7 is a diagram illustrating the arrangement of the pump 5 according to a modified example. The pump 5 according to this example is arranged below the water surface of the heat storage tank 2. The pump 5 may also be provided inside the heat storage tank 2 (underwater).

[0055] The various components of the open piping system 1 and pressure control method of the present invention do not need to exist independently of one another. It is acceptable for multiple components to be formed as a single member, for one component to be formed from multiple members, for one component to be part of another component, or for part of one component to overlap with part of another component, etc.

[0056] The present embodiment encompasses the following technical ideas. (1) A pipe connected to a liquid storage tank that stores the liquid; A load device connected to the piping; a pump disposed upstream of the load device and configured to circulate the liquid through the pipe and the liquid storage tank; a back pressure control valve disposed downstream of the load device; a control device having an opening adjustment unit that adjusts the opening of the back pressure control valve, The open piping system is characterized in that the opening adjustment unit adjusts the opening of the back pressure control valve so that the internal pressure in at least a portion of the uppermost part of the piping becomes negative during normal operation of the pump. (2) Further, an air vent valve is provided at the top of the piping, the load device is disposed at least at the uppermost portion of the piping, The open piping system according to (1), wherein the location where the air vent valve is provided is upstream of the load equipment and is under positive pressure during normal operation of the pump. (3) An open piping system as described in (1) or (2), further comprising another pump between the pump and the top of the piping, the other pump having a lower flow rate and a higher head than the pump. (4) A pressure control method in an open piping system according to any one of (1) to (3), The control device includes a pump output adjusting unit, the pump output adjusting unit controls the rotation speed of the pump while creating a negative pressure in at least a part of the uppermost part of the piping so as to offset at least a part of the actual head during normal operation of the pump; A pressure control method characterized in that the control device adjusts the pressure in the piping by controlling the water supply pressure of the pump adjusted by the pump output adjustment unit and the back pressure adjusted by the opening adjustment unit in conjunction with each other. (5) the open piping system includes an air vent valve provided at the top of the piping; The pressure control method according to (4), wherein the pump output adjustment unit, when the pump is started, gradually increases the power supply frequency of the pump in conjunction with the opening adjustment unit gradually increasing the opening of the back pressure control valve, thereby increasing the water supply pressure and adjusting the pressure inside the piping, and increases the pressure inside the piping to a pressure at which the air vent valve operates. (6) The pressure control method according to (4) or (5), wherein the pump output adjustment unit controls the pump head when bleeding air from the piping while the pump is operating so that the pressure inside the piping is higher than the pressure inside the piping during normal operation of the pump. (7) The control device controls the internal pressure in at least a portion of the top of the pipe so that when a low-temperature liquid is passed through the pipe, the internal pressure becomes a larger negative pressure than when a relatively high-temperature liquid is passed through the pipe. [Explanation of symbols]

[0057] 1. Open piping system 2 Heat storage tank (liquid storage tank) 3 Piping 3a Top 4 Air conditioner (load equipment) 5. Pump 5a inverter 6 Back pressure control valve 7 Control Device 7a Opening adjustment part 7b Pump output adjustment section 8 Pressure Indicating Controller (PIC) 9 Air vent valve 10. Check valve 11. Volumetric pump 12 Pressure gauge 13 Control valve

Claims

1. A pipe connected to a liquid storage tank that stores the liquid; A load device connected to the piping; a pump disposed upstream of the load device and configured to circulate the liquid through the pipe and the liquid storage tank; a back pressure control valve disposed downstream of the load device; a control device having an opening adjustment unit that adjusts the opening of the back pressure control valve, The opening adjustment unit adjusts the opening of the back pressure control valve so that the internal pressure in at least a portion of the top of the piping becomes a negative pressure that is lower than atmospheric pressure during normal operation of the pump.

2. Further, an air vent valve is provided at the top of the piping, the load device is disposed at least at the uppermost portion of the piping, 2. The open piping system according to claim 1, wherein the location where the air vent valve is provided is upstream of the load equipment and is under positive pressure during normal operation of the pump.

3. 3. The open piping system according to claim 1, further comprising another pump between the pump and the top of the piping, the other pump having a lower flow rate and a higher head than the pump.

4. The opening adjustment unit is adjusting an opening degree of the back pressure control valve so that the internal pressure in the piping, including the part at the top of the piping, becomes positive when the pump is started, before the pump is stopped, and when the pump is stopped; 4. The open piping system according to claim 1, wherein the opening degree of the back pressure control valve is adjusted so that the internal pressure in at least a part of the uppermost portion of the piping becomes negative during normal operation of the pump.

5. A method for controlling pressure in an open piping system according to any one of claims 1 to 4, comprising: The control device includes a pump output adjusting unit, the pump output adjusting unit controls the rotation speed of the pump while creating a negative pressure in at least a part of the uppermost part of the piping so as to offset at least a part of the actual head during normal operation of the pump; A pressure control method characterized in that the control device adjusts the pressure in the piping by controlling the water supply pressure of the pump adjusted by the pump output adjustment unit and the back pressure adjusted by the opening adjustment unit in conjunction with each other.

6. the open piping system includes an air vent valve provided at the top of the piping; 6. The pressure control method according to claim 5, wherein, when the pump is started, the pump output adjustment unit gradually increases the power supply frequency of the pump in conjunction with the opening adjustment unit gradually increasing the opening of the back pressure control valve, thereby increasing the water supply pressure and adjusting the pressure in the piping, thereby increasing the pressure in the piping to a pressure at which the air vent valve operates.

7. 7. The pressure control method according to claim 5, wherein the pump output adjustment unit controls the pump head when bleeding air from the piping while the pump is operating so that the pressure inside the piping is higher than the pressure inside the piping during normal operation of the pump.

8. A pressure control method described in any one of claims 5 to 7, wherein the control device controls the internal pressure in at least a portion of the top of the pipe so that when a low-temperature liquid is passed through the pipe, the internal pressure becomes a greater negative pressure than when a relatively high-temperature liquid is passed through the pipe.

9. When the internal pressure in the portion of the uppermost part of the pipe changes from a negative pressure to 0 mAq, Issue an alarm, The pressure control method according to claim 5 , further comprising increasing a power supply frequency of the pump to control the uppermost portion of the pipe to maintain a positive pressure.

Images