CN118442753A - A system for operating multiple open cold storage containers in series with static pressure difference and a control method thereof - Google Patents

Abstract

The present invention relates to a system for serial operation of multiple open cold storage containers with static pressure difference, wherein the return water main pipe of the process refrigeration system is connected with the water inlet of the upstream high-position open cold storage container, and the water outlet of the upstream high-position open cold storage container is connected with the water supply main pipe of the process refrigeration system; the upstream high-position open cold storage container is connected with the downstream low-position open cold storage container through a gravity flow pipeline, and the upper and lower water outlets of the downstream low-position open cold storage container are respectively connected with the water inlet end of the primary variable frequency pump of chilled water and the water supply main pipe of the process refrigeration system, the water outlet end of the primary variable frequency pump of chilled water is connected with the water inlet end of the electric refrigeration host, and the water outlet end of the electric refrigeration host is connected with the water supply main pipe of the process refrigeration system. The method of serially connecting two open cold storage containers with static pressure difference can directly drive water flow by using the liquid level difference, the system is simple, convenient for related transformation work, and reduces the configuration of related high-power circulating water pumps, which can obtain greater benefits in system construction investment and operation costs.

Description

A system for operating multiple open cold storage containers in series with static pressure difference and its control method

Technical Field

The present invention relates to the technical field of water cold storage system expansion, and in particular to a system for serially operating multiple open cold storage containers with static pressure difference and a control method thereof.

Background technique

At present, the most mainstream water storage system in the world is the natural temperature stratification type. The water storage device needs to be equipped with an efficient water distributor to guide the water flow to be evenly distributed, and use the temperature/density difference of water to achieve natural stratification, significantly reducing the undesirable cold and hot mixing that causes the system efficiency to decrease, ensuring that the system has a high volume utilization rate.

In engineering practice, cold storage containers are divided into two types: open and closed. Due to the relatively high working pressure, closed containers are generally manufactured according to the industrial standards of pressure vessels. The corresponding cost is relatively high, and it is difficult to achieve a design volume of more than 1,000 cubic meters. They are usually only used as short-term disaster recovery equipment in data centers and other occasions. For occasions where the design requires a large-scale cold storage capacity, open cold storage containers that are ventilated to the atmosphere are usually used. The unit volume cost is much lower than that of closed containers, which supports large-capacity cold storage at a relatively low cost. Common forms mainly include open cylindrical steel welded storage tanks, steel concrete pools, square or special-shaped steel welded water tanks, etc.

In engineering practice, with the changes in electricity price policies, production loads, and corporate operating profit and loss situations, some projects have a practical need to expand the scale of existing water storage cooling systems.

Summary of the invention

The technical problem to be solved by the present invention is to study a system for serially operating multiple open cold storage containers with static pressure difference and a control method thereof, which has low expansion cost, high system integration rate and little interference with the operation of the existing system.

The technical solution of the present invention to solve the above technical problems is as follows:

A system for serial operation of multiple open cold storage containers with static pressure difference comprises an electric refrigeration main unit, a primary variable frequency pump for chilled water, an upstream high-position open cold storage container and a downstream low-position open cold storage container, wherein a return water main pipe of a process refrigeration system is connected with an upper water inlet of the upstream high-position open cold storage container, and a lower water outlet of the upstream high-position open cold storage container is connected with a water supply main pipe of the process refrigeration system; the upstream high-position open cold storage container is connected with a downstream low-position open cold storage container through a gravity flow pipeline, and an upper water outlet and a lower water outlet of the downstream low-position open cold storage container are respectively connected with a water inlet end of a primary variable frequency pump for chilled water and a water supply main pipe of the process refrigeration system, a water outlet end of the primary variable frequency pump for chilled water is connected with a water inlet end of the electric refrigeration main unit, and a water outlet end of the electric refrigeration main unit is connected with a water supply main pipe of the process refrigeration system; the static pressure in the upstream high-position open cold storage container is greater than the static pressure in the downstream low-position open cold storage container.

The beneficial effect of the present invention is: directly utilizing the potential energy generated by the water level difference between multiple containers with a liquid level static pressure difference, under the cooling condition, the system chilled water return first enters the upstream high-position open cold storage container, and then flows into the downstream low-position open cold storage container with a low liquid level in the form of gravity flow through the gravity flow pipeline connecting the two cold storage containers driven by gravity potential energy. The above method of connecting two open cold storage containers with a static pressure difference in series can directly drive the water flow by utilizing the liquid level difference. The system is simple, convenient for related transformation work, and reduces the configuration of related high-power circulating water pumps, which can obtain greater benefits in system construction investment and operating costs.

Since the core temperature setting of the system does not need to be adjusted, the inevitable decrease in system efficiency, energy storage density and effective cold storage and release capacity under the indirect connection form is avoided. Combined with the peak and valley time-of-use electricity prices, it can save more operating electricity costs for the operator and further improve the economic benefits of the system. The series operation of multiple open cold storage containers with static pressure differences can utilize the liquid level difference to form gravity flow to complete the working cycle, reducing the complexity of the system, reducing the configuration of the circulation pump and the corresponding energy consumption, and can further improve the economy of the water storage system renovation and expansion project.

Based on the above technical solution, the present invention can also be improved as follows.

Furthermore, a cold storage variable frequency water pump is arranged on the upper water outlet of the downstream low-position open cold storage container, and a cold release variable frequency water pump is arranged on the lower water outlet of the downstream low-position open cold storage container, and the cold storage variable frequency water pump and the cold release variable frequency water pump are arranged in the same direction along the water flow direction; the process refrigeration system water supply main pipe is provided with a chilled water secondary variable frequency pump downstream of the cold release variable frequency water pump, and the chilled water secondary variable frequency pump is arranged in the same direction as the cold release variable frequency water pump; the lower water outlet of the downstream low-position open cold storage container is connected with the water outlet end of the electric refrigeration main unit through a first connecting pipeline; the process refrigeration system return water main pipe is connected with the water inlet end of the chilled water primary variable frequency pump through a second connecting pipeline.

Furthermore, electric two-way quick-opening valves are provided on the water inlet at the top of the upstream high-position open cold storage container, the water outlet at the bottom of the upstream high-position open cold storage container, the water outlet at the top of the downstream low-position open cold storage container, the water outlet at the bottom of the downstream low-position open cold storage container, the first connecting pipeline, the second connecting pipeline and the pipelines on both sides of the node where the first connecting pipeline is connected to the water outlet end of the electric refrigeration host.

Furthermore, liquid level measuring devices are provided in both the upstream high-position open cold storage container and the downstream low-position open cold storage container; a liquid level switch and a traditional analog liquid level sensor are provided on the inner wall of the downstream low-position open cold storage container.

Furthermore, flow sensors are provided on the upper water inlet of the upstream high-position open cold storage container, the gravity flow pipeline, the upper water outlet of the downstream low-position open cold storage container, and the lower water outlet of the downstream low-position open cold storage container.

Furthermore, an electric two-way regulating valve is provided on the gravity flow pipeline.

Another technical solution of the present invention is as follows:

A control method for the series operation of multiple open cold storage containers with a static pressure difference adopts the series operation system of multiple open cold storage containers with a static pressure difference as described above, and the control method includes: selecting a fixed time interval to calculate the rate of liquid level rise/fall based on accurate real-time data of liquid level measurement, and pre-calculating the time difference to reach the set low/high liquid level in combination with the current actual liquid level; when the liquid level rises, the high limit liquid level corresponding to the liquid level switch installed on the container is used to calculate the remaining liquid level height difference; when the liquid level drops, the low limit liquid level corresponding to the liquid level switch installed on the container is used to calculate the remaining liquid level height difference, leaving a certain safety margin; calculating the estimated time to reach the critical liquid point through a formula, and performing a switch valve action.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic structural diagram of a system for serially operating multiple open cold storage containers with a static pressure difference according to the present invention.

In the accompanying drawings, the components represented by the reference numerals are listed as follows:

1. Electric refrigeration main unit; 2. Chilled water primary variable frequency pump; 3. Chilled water secondary variable frequency pump; 4. Upstream high-position open cold storage container; 5. Downstream low-position open cold storage container; 6. Cold storage variable frequency water pump; 7. Cold release variable frequency water pump; 8. Flow sensor; 9. Electric two-way switching valve; 10. Electric two-way regulating valve; 11. Liquid level measuring device; 12. Liquid level switch; 13. Traditional analog liquid level sensor; 14. Gravity flow pipeline; 15. First connecting pipeline; 16. Second connecting pipeline.

Detailed ways

The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

As shown in Figure 1, embodiment 1 of the present invention is a system for operating multiple open cold storage containers in series with a static pressure difference, including an electric refrigeration host 1, a primary variable frequency pump 2 for chilled water, an upstream high-position open cold storage container 4 and a downstream low-position open cold storage container 5, a process refrigeration system return water main pipe is connected to the upper water inlet of the upstream high-position open cold storage container 4, and a lower water outlet of the upstream high-position open cold storage container 4 is connected to the process refrigeration system water supply main pipe; the upstream high-position open cold storage container 4 is connected to the downstream low-position open cold storage container 5 through a heavy The force flow pipeline 14 is connected with the downstream low-level open cold storage container 5, the upper water outlet and the lower water outlet of the downstream low-level open cold storage container 5 are respectively connected with the water inlet end of the primary frequency conversion pump 2 of chilled water and the water supply main pipe of the process refrigeration system, the water outlet end of the primary frequency conversion pump 2 of chilled water is connected with the water inlet end of the electric refrigeration host 1, and the water outlet end of the electric refrigeration host 1 is connected with the water supply main pipe of the process refrigeration system; the static pressure in the upstream high-level open cold storage container 4 is greater than the static pressure in the downstream low-level open cold storage container 5.

Directly utilizing the potential energy generated by the water level difference between multiple containers with a static pressure difference in the liquid level, under the cooling condition, the system chilled water return water first enters the upstream high-position open cold storage container 4, and then flows into the downstream low-position open cold storage container 5 with a low liquid level in the form of gravity flow through the gravity flow pipeline 14 connecting the two cold storage containers driven by the gravity potential energy. The above method of connecting two open cold storage containers with a static pressure difference in series can directly drive the water flow by utilizing the liquid level difference, the system is simple, and is convenient for related transformation work, and reduces the configuration of related high-power circulating water pumps, which can obtain greater benefits in system construction investment and operating costs.

Since the core temperature setting of the system does not need to be adjusted, the inevitable decrease in system efficiency, energy storage density and effective cold storage and release capacity under the indirect connection form is avoided. Combined with the peak and valley time-of-use electricity prices, it can save more operating electricity costs for the operator and further improve the economic benefits of the system. The series operation of multiple open cold storage containers with static pressure differences can utilize the liquid level difference to form gravity flow to complete the working cycle, reducing the complexity of the system, reducing the configuration of the circulation pump and the corresponding energy consumption, and can further improve the economy of the water storage system renovation and expansion project.

Embodiment 2 of the present invention is a system for serial operation of multiple open cold storage containers with a static pressure difference. On the basis of Embodiment 1, a cold storage variable frequency water pump 6 is arranged on the upper water outlet of the downstream low-level open cold storage container 5, and a cold release variable frequency water pump 7 is arranged on the lower water outlet of the downstream low-level open cold storage container 5. The cold storage variable frequency water pump 6 and the cold release variable frequency water pump 7 are both arranged in the same direction along the water flow direction; a chilled water secondary variable frequency pump 3 is arranged on the water supply main pipe of the process refrigeration system downstream of the cold release variable frequency water pump 7, and the chilled water secondary variable frequency pump 3 is arranged in the same direction as the cold release variable frequency water pump 7; the lower water outlet of the downstream low-level open cold storage container 5 is connected to the water outlet end of the electric refrigeration main unit 1 through a first connecting pipe 15; the return water main pipe of the process refrigeration system is connected to the water inlet end of the chilled water primary variable frequency pump 2 through a second connecting pipe 16.

Embodiment 3 of the present invention is a system for operating multiple open cold storage containers in series with a static pressure difference. Based on Embodiment 2, the water inlet at the upper part of the upstream high-position open cold storage container 4, the water outlet at the lower part of the upstream high-position open cold storage container 4, the water outlet at the upper part of the downstream low-position open cold storage container 5, the water outlet at the lower part of the downstream low-position open cold storage container 5, the first connecting pipeline 15, the second connecting pipeline 16, and the pipelines on both sides of the node where the first connecting pipeline 15 is connected to the water outlet end of the electric refrigeration host 1 are all provided with electric two-way quick-opening valves 9. In specific implementation, the electric two-way quick-opening valve 9 can be a quick-opening electric switch valve and a pneumatic two-way switch valve. When conditions permit, a pneumatic two-way switch valve is preferably used.

Embodiment 4 of the present invention is a system for serial operation of multiple open cold storage containers with static pressure difference. On the basis of embodiment 3, a liquid level measuring device 11 is provided in both the upstream high-level open cold storage container 4 and the downstream low-level open cold storage container 5; a liquid level switch 12 and a traditional analog liquid level sensor 13 are provided on the inner wall of the downstream low-level open cold storage container 5. The high-precision liquid level measuring device 11 is configured to measure the actual accurate liquid level height in the container at the millimeter level; at the same time, in order to improve the robustness of the automatic control system, in addition to the aforementioned liquid level measuring device 11, the liquid level measurement system is also configured with a traditional analog liquid level sensor 11 as a backup, and its measurement data is also real-time online, which can be used as a rough calibration of the data of the high-precision liquid level measuring device 11, and assist in the mutual calibration of the liquid level rise and fall trend.

Embodiment 5 of the present invention is a system for operating multiple open cold storage containers in series with a static pressure difference. On the basis of embodiment 4, flow sensors 8 are provided on the upper water inlet of the upstream high-level open cold storage container 4, the gravity flow pipeline 14, the upper water outlet of the downstream low-level open cold storage container 5, and the lower water outlet of the downstream low-level open cold storage container 5. For general systems, a flow sensor 8 is usually provided at the inlet or outlet of the container to measure the real-time working cycle flow of the cold storage container. For a process system with multiple containers in series with a static pressure difference, the flow sensor 8 at the outlet of the container with a high liquid level and the flow sensor 8 at the inlet of the container with a low liquid level can be used together.

Embodiment 6 of the present invention is a system for operating multiple open cold storage containers in series with static pressure difference. Based on Embodiment 5, an electric two-way regulating valve 10 is provided on the gravity flow pipeline 14. Cooperating with the primary variable frequency pump 2 of chilled water, fast water flow tracking response regulation is achieved; the electric two-way regulating valve 10 has the advantages of equal percentage regulation characteristics of the seat valve system and full regulation stroke time within 60S.

Embodiment 7 of the present invention is a control method for the series operation of multiple open cold storage containers with a static pressure difference. The system of multiple open cold storage containers with a static pressure difference in embodiment 4 is adopted. The control method includes: selecting a fixed time interval to calculate the rate of liquid level rise/fall based on accurate real-time data of liquid level measurement, and pre-calculating the time difference to reach the set low/high liquid level in combination with the current actual liquid level; when the liquid level rises, the upper limit liquid level corresponding to the liquid level switch 12 installed in the container is taken to calculate the remaining liquid level height difference; when the liquid level drops, the lower limit liquid level corresponding to the liquid level switch 12 installed in the container is taken to calculate the remaining liquid level height difference, leaving a certain safety margin (1.2 times the full stroke time of the valve switch); calculating the time expected to reach the critical liquid point by a formula, and performing the valve switching action.

In specific implementation, taking 30s as an example, when the calculated critical liquid level point still needs 30*1.2+15=51s, the program prepares for valve closing but does not immediately execute the valve closing action. The 15 in the calculation formula refers to the delay of 15s to determine whether the unfavorable trend has ended, so as to avoid the automatic control system from reacting too sensitively and causing the amplitude of the controlled target parameter of the system to be too large. If it has ended, the second round of judgment is stopped and the liquid level change rate is solved again. If the unfavorable trend has not stopped, the action command of valve closing is issued to control the liquid level. The corresponding requirement is that the electric two-way switch valve 9 is a fast-opening type, and the entire switch time should not exceed 30s.

The PID adjustment of the water pump frequency conversion can achieve the tracking response of zeroing the difference between the inlet and outlet water flow of the rapid container. In terms of control methods, the PID adjustment of the water pump frequency conversion needs to be carried out according to the liquid level in the container and the relative difference between the inlet and outlet flow of a single container. The setting characteristics of the water pump frequency conversion PID are the "high frequency + small amplitude" fast response mode. The PID parameters are reasonably set to make the response sensitive and not over-adjusted, and the difference between the inlet and outlet flow of the upstream container is maintained within ±50cmh as much as possible.

Finally, all open cold storage containers are equipped with high and low limit liquid level switches. Once the high or low liquid level limit is triggered, the action instruction that must be cut out of the cooling release condition will be directly issued at the highest priority control level to ensure that the container does not overflow abnormally or that the liquid level of the upper water distributor is exposed above the water surface.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (7)

1. The series operation system of the plurality of open cold accumulation containers with static pressure difference is characterized by comprising an electric refrigeration host (1), a chilled water primary variable frequency pump (2), an upstream high-level open cold accumulation container (4) and a downstream low-level open cold accumulation container (5), wherein a process refrigeration system backwater main pipe is communicated with a water inlet at the upper part of the upstream high-level open cold accumulation container (4), and a water outlet at the lower part of the upstream high-level open cold accumulation container (4) is communicated with a process refrigeration system water supply main pipe; the upstream high-level open cold accumulation container (4) is communicated with the downstream low-level open cold accumulation container (5) through a gravity flow pipeline (14), an upper water outlet and a lower water outlet of the downstream low-level open cold accumulation container (5) are respectively communicated with a water inlet end of the chilled water primary variable frequency pump (2) and a water supply main pipe of the process refrigeration system, a water outlet end of the chilled water primary variable frequency pump (2) is communicated with a water inlet end of the electric refrigeration host machine (1), and a water outlet end of the electric refrigeration host machine (1) is communicated with the water supply main pipe of the process refrigeration system; the static pressure in the upstream high-position open cold accumulation container (4) is larger than the static pressure in the downstream low-position open cold accumulation container (5).

2. The series operation system of a plurality of open cold accumulation containers with static pressure difference according to claim 1, wherein a cold accumulation variable frequency water pump (6) is arranged on a water outlet at the upper part of the downstream low-level open cold accumulation container (5), a cold release variable frequency water pump (7) is arranged on a water outlet at the lower part of the downstream low-level open cold accumulation container (5), and the cold accumulation variable frequency water pump (6) and the cold release variable frequency water pump (7) are both arranged along the same direction of water flow; the process refrigeration system water supply main pipe is provided with a chilled water secondary variable frequency pump (3) at the downstream of the cold releasing variable frequency water pump (7), and the chilled water secondary variable frequency pump (3) and the cold releasing variable frequency water pump (7) are arranged in the same direction; the water outlet at the lower part of the downstream low-level open cold accumulation container (5) is communicated with the water outlet end of the electric refrigeration host (1) through a first connecting pipeline (15); and the process refrigeration system backwater main pipe is communicated with the water inlet end of the chilled water primary variable frequency pump (2) through a second connecting pipeline (16).

3. The series operation system of a plurality of open cold accumulation containers with static pressure difference according to claim 2, wherein an electric two-way quick-opening valve (9) is arranged on each of the water inlet at the upper part of the upstream high-position open cold accumulation container (4), the water outlet at the lower part of the upstream high-position open cold accumulation container (4), the water outlet at the upper part of the downstream low-position open cold accumulation container (5), the water outlet at the lower part of the downstream low-position open cold accumulation container (5), the first connecting pipeline (15), the second connecting pipeline (16) and the pipelines at two sides of the node where the first connecting pipeline (15) is communicated with the water outlet end of the electric refrigerating host machine (1).

4. A multiple open regenerator vessel tandem operation system with static pressure difference according to claim 3, wherein a liquid level measuring device (11) is arranged in each of the upstream high-level open regenerator vessel (4) and the downstream low-level open regenerator vessel (5); the inner wall of the downstream low-level open cold accumulation container (5) is provided with a liquid level switch (12) and a traditional analog liquid level sensor (13).

5. The series operation system of a plurality of open cold accumulation containers with static pressure difference according to claim 4 is characterized in that a water inlet at the upper part of the upstream high-level open cold accumulation container (4), the gravity flow pipeline (14), a water outlet at the upper part of the downstream low-level open cold accumulation container (5) and a water outlet at the lower part of the downstream low-level open cold accumulation container (5) are all provided with flow sensors (8).

6. A series operation system of a plurality of open cold storage containers with static pressure difference according to claim 5, characterized in that an electric two-way regulating valve (10) is arranged on the gravity flow pipeline (14).

7. A control method for serial operation of a plurality of open cold storage containers with static pressure difference, using the serial operation system of a plurality of open cold storage containers with static pressure difference according to claim 4, characterized in that the control method comprises: selecting a fixed time interval based on accurate liquid level measurement real-time data to calculate the liquid level rising/falling speed, pre-calculating the time difference reaching a set limit low/high liquid level by combining the current actual liquid level, calculating the residual liquid level height difference by taking the high limit liquid level corresponding to a liquid level switch (12) installed on the container when the liquid level rises, and calculating the residual liquid level height difference by taking the low limit liquid level corresponding to the liquid level switch (12) installed on the container when the liquid level falls, so as to leave a certain safety margin; and calculating the expected time reaching the critical liquid site through a formula, and performing valve opening and closing actions.