Laboratory energy-saving constant-pressure water supply system and water supply method thereof

Abstract

The invention discloses a laboratory energy-saving constant-pressure water supply system and a water supply method thereof.The laboratory energy-saving constant-pressure water supply system comprises a control system, a terminal water management system, a cooling tower, a water pump unit, a valve control system and a measuring system, and the valve control system comprises a refrigeration equipment electric water valve and a water pump electric valve; the terminal water management system is used for controlling the opening and closing state of an electric water valve of the refrigeration equipment according to an operation state signal of the refrigeration equipment, and the control system comprises a water pump energy-saving control module and a constant-pressure water supply control module. The water pump energy-saving control module is used for controlling the opening and closing state of a water pump electric valve according to the operation state signal of the refrigeration equipment transmitted by the terminal water management system; and the constant-pressure water supply control module is used for calculating water supply and return pressure difference according to the pressure value measured by the measuring system, and performing logical operation based on the water supply and return pressure difference and a set pressure difference to control the operation states of a power frequency pump and a variable frequency pump of the water pump unit. According to the invention, automatic control of laboratory cooling water supply is realized, and energy consumption is effectively reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of water supply control, and in particular relates to a laboratory energy-saving constant-pressure water supply system and a water supply method thereof. Background Art

[0002] A cooling tower is a device that uses water as a circulating coolant to absorb heat from a system and discharge it into the atmosphere to lower the water temperature. It uses the heat exchange between water and air flow to generate steam. The steam evaporates and takes away the heat to achieve the principles of evaporative heat dissipation, convection heat transfer and radiation heat transfer. It dissipates the waste heat generated in industry or refrigeration and air conditioning to lower the water temperature through evaporative heat dissipation to ensure the normal operation of the system. The device is generally barrel-shaped, hence the name cooling tower.

[0003] The circulating cooling water system is an important component of industrial production and also the part that accounts for the largest water and energy consumption. The water consumption of the circulating cooling water system accounts for 70% to 80% of the industrial water consumption. For example, the power consumption of the circulating water pump in a certain electric field accounts for 20% of the power consumption of the plant. Therefore, the consumption and emission reduction of the circulating cooling water system is of great significance to the consumption and emission reduction of industry.

[0004] Combined with the actual operation analysis of the existing reliability and environmental engineering laboratory, there is a lot of room for optimization in the laboratory's power consumption. After two years of operating data statistics, the laboratory's energy consumption in the cooling system accounts for 30% to 40% of the electricity cost, and may be higher in some special cases.

[0005] There have been studies on energy-saving renovation of cooling towers at home and abroad, which are mostly aimed at heavy factories or thermal power plants, etc., but there are very few energy-saving renovations of cooling towers for testing laboratories. During the operation of laboratory equipment, cooling water is not required for cooling throughout the process, and the compressor does not need to be enabled most of the time. However, the current requirements of testing equipment manufacturers for supporting equipment are only to meet the maximum water consumption, and no energy-saving design is carried out. Summary of the invention

[0006] The first purpose of the present invention is to overcome the shortcomings and deficiencies in the prior art and provide a laboratory energy-saving constant pressure water supply system, which is suitable for laboratory cooling water, realizes automatic control of laboratory cooling water supply and effectively reduces energy consumption.

[0007] The second object of the present invention is to provide a water supply method based on a laboratory energy-saving constant pressure water supply system.

[0008] The object of the present invention is achieved through the following technical solutions: a laboratory energy-saving constant-pressure water supply system, including a control system, a terminal water management system, a cooling tower, a water pump unit, a valve control system and a measurement system, the cooling tower and the water pump unit supply water to the refrigeration equipment through a water supply pipe, the refrigeration equipment is connected to the cooling tower through a return pipe, the valve control system includes an electric water valve of the refrigeration equipment and an electric valve of the water pump, the terminal water management system is used to control the opening and closing state of the electric water valve of the refrigeration equipment according to the operating status signal of the refrigeration equipment, the control system includes a water pump energy-saving control module and a constant-pressure water supply control module,

[0009] The water pump energy-saving control module is used to control the opening and closing state of the water pump electric valve according to the operating state signal of the refrigeration equipment transmitted by the terminal water management system;

[0010] The constant pressure water supply control module is used to calculate the supply and return water pressure difference according to the total water outlet pressure and the total return water pressure measured by the measurement system, and perform logical operations based on the supply and return water pressure difference and the set pressure difference to control the operating status of the industrial frequency pump and the variable frequency pump of the water pump unit.

[0011] Preferably, the terminal water management system includes a signal processing module, a time delay relay and an intermediate relay, and the signal processing module is used to receive and process the status signal of the refrigeration equipment, as follows:

[0012] When receiving a start signal from the refrigeration equipment, the signal processing module controls the electric water valve of the refrigeration equipment to open via an intermediate relay;

[0013] When receiving the shutdown signal of the refrigeration equipment, the signal processing module controls the delay relay to delay the set time limit, and then controls the electric water valve of the refrigeration equipment to close through the intermediate relay.

[0014] Preferably, the terminal water management system sends the operating status signal of the refrigeration equipment to the control system through the wireless transmission module, and the water pump energy-saving control module is specifically used to perform logical operations according to the operating status signal of the refrigeration equipment, determine the water consumption, and control the opening and closing states of the electric valves of each water pump according to the water consumption, as follows:

[0015] When the water consumption is greater than the system surplus, the water pump electric valve is controlled to open to increase the operation of the water pump unit;

[0016] When the water consumption is less than the system margin, the water pump electric valve is controlled to close to reduce the operation of the water pump unit.

[0017] Preferably, the water pump unit includes at least two industrial frequency pumps and one variable frequency pump, the variable frequency pump is equipped with a separate frequency converter for control, and the constant pressure water supply control module is specifically used for:

[0018] The supply and return water pressure difference is calculated based on the total water outlet pressure monitored by the water outlet pressure sensor at the water outlet of the pump unit and the total water supply pressure monitored by the return water pressure sensor at the return water end of the cooling tower to determine whether the supply and return water pressure difference is lower than the set pressure difference.

[0019] If yes, the inverter output frequency is increased first to increase the speed of the variable frequency pump. If the supply and return water pressure difference is still lower than the set pressure difference after the variable frequency pump reaches full frequency, the industrial frequency pump is started again until the supply and return water pressure difference increases to the set pressure difference.

[0020] If not, the output frequency of the inverter is reduced first to reduce the speed of the variable frequency pump. If the supply and return water pressure difference is still higher than the set pressure difference after the variable frequency pump reaches the minimum operating frequency, reduce the industrial frequency pump until the supply and return water pressure difference is reduced to the set pressure difference.

[0021] Preferably, the control system further includes a cooling tower energy-saving control module, which is used to calculate the supply and return water temperature difference according to the supply water temperature detected by the supply water temperature sensor at the water outlet of the cooling tower and the return water temperature detected by the return water temperature sensor at the return water end of the cooling tower, and to perform a logical operation based on the supply and return water temperature difference and the set water temperature difference to determine the operating state of the cooling tower's heat dissipation system, as follows:

[0022] Determine whether the supply and return water temperature difference is higher than the set water temperature difference.

[0023] If yes, start the spray pumps of the closed cooling tower in sequence. When the supply and return water temperature difference is still higher than the set water temperature difference after all the spray pumps are turned on, turn on the fan again until the maximum cooling capacity of the cooling tower is reached;

[0024] If not, turn off the fan. When the supply and return water temperature difference is still higher than the set water temperature difference, turn off the spray pumps of the closed cooling tower in turn until the supply and return water temperature difference reaches the set water temperature difference.

[0025] Preferably, the control system also includes an online monitoring module, which is used to transmit the equipment operation status signal measured by the measurement system to the controller. The controller determines the fault condition of the equipment based on the equipment operation status signal and issues a fault alarm reminder, and at the same time displays the equipment operation status signal online through the human-machine interface of the industrial computer.

[0026] Preferably, the measurement system includes a sensing component and a measuring component, the sensing component includes a water outlet pressure sensor, a return water pressure sensor, a water supply temperature sensor and a return water temperature sensor, and the measuring component includes a pressure measurement component, a temperature measurement component and a power measurement component.

[0027] The pressure measurement component is used to collect pressure signals from the water outlet pressure sensor and the water return pressure sensor, and transmit the pressure signals to the control system;

[0028] The temperature measurement component is used to collect temperature signals from the water supply temperature sensor and the return water temperature sensor, and transmit the temperature signals to the control system;

[0029] The power measurement component is used to measure the electrical operating parameters of the corresponding equipment and transmit the electrical operating parameters to the control system.

[0030] Preferably, the cooling tower is an open cooling tower, the water outlet, the water reservoir, the water pump unit and the water inlet of the refrigeration equipment of the closed cooling tower are connected in sequence through a water supply pipe, and the water return port of the cooling tower is connected to the water outlet of the refrigeration equipment through a water return pipe.

[0031] The water storage tank is constructed with a primary water storage tank, a secondary water storage tank and a tertiary water storage tank, which are arranged horizontally, a barrier A is provided between the primary water storage tank and the secondary water storage tank, a coarse filter is installed above the barrier A, a barrier B is provided between the secondary water storage tank and the tertiary water storage tank, a fine filter is installed above the barrier B, the primary water storage tank is connected with the water outlet of the closed cooling tower through a water supply pipe, the tertiary water storage tank is connected with the water pump unit through a water supply pipe, a water replenishment port is provided at the top of the tertiary water storage tank, and maintenance ports are provided at the tops of the primary water storage tank, the secondary water storage tank and the tertiary water storage tank.

[0032] Preferably, it further comprises a soft water system, wherein the soft water system comprises a water softener, and the water softener is used to filter the municipal tap water in the water supply pipe before supplying the water to the refrigeration equipment.

[0033] A water supply method based on the above-mentioned laboratory energy-saving constant pressure water supply system comprises the following steps:

[0034] S1. Turn on the power of the laboratory energy-saving constant pressure water supply system and refrigeration equipment and enter the standby state;

[0035] S2. Start the refrigeration equipment. The signal processing module of the terminal water management system transmits the start signal to the control system through the wireless transmission module. The control system performs logical operations based on the start signal to determine the water consumption. The water pump unit is started in advance based on the water consumption. The water pump unit starts to run at a low frequency and pressurizes the system to a set pressure difference within a preset time.

[0036] S3, at the same time, the signal processing module sends a command to the intermediate relay to control the electric water valve of the refrigeration equipment to open, so as to realize the cooling water supply;

[0037] S4. The control system determines the water consumption in real time according to the operating status signal of the refrigeration equipment transmitted by the terminal water management system, and adjusts the operating status of the water pump unit according to the water consumption, as follows:

[0038] When the water consumption is greater than the system margin, the water pump electric valve is controlled to open to increase the operation of the water pump unit; when the water consumption is less than the system margin, the water pump electric valve is controlled to close to reduce the operation of the water pump unit;

[0039] S5. The control system calculates the supply and return water pressure difference based on the total supply water pressure and the total return water pressure measured by the measurement system, and controls the operation of the water pump unit according to the supply and return water pressure difference and the set pressure difference, as follows:

[0040] When the supply and return water pressure difference is lower than the set pressure difference, the output frequency of the inverter is increased first to increase the speed of the variable frequency pump. If the supply and return water pressure difference is still lower than the set pressure difference after the variable frequency pump reaches full frequency, the industrial frequency pump is started again until the supply and return water pressure difference increases to the set pressure difference.

[0041] When the supply and return water pressure difference is higher than the set pressure difference, the inverter output frequency is reduced first to reduce the speed of the variable frequency pump. If the supply and return water pressure difference is still higher than the set pressure difference after the variable frequency pump reaches the minimum operating frequency, the power frequency pump is reduced until the supply and return water pressure difference is reduced to the set pressure difference.

[0042] S6. Real-time online monitoring of the operating status of the water pump unit and cooling tower through the human-machine interface of the control system;

[0043] S7, the control system controls the power frequency pump and the variable frequency pump to operate the turbine according to the operation time of the water pump unit: when the operation time of the power frequency pump reaches the first preset time, the power frequency pump is operated according to the principle of first start first stop; when the operation time of the variable frequency pump reaches the second preset time, the two variable frequency pumps are operated to ensure that one variable frequency pump is in standby and the other is in use;

[0044] S8. Shut down the refrigeration equipment. The signal processing module of the terminal water management system sends the shutdown signal to the delay relay. After the set time delay, the intermediate relay controls the electric water valve of the refrigeration equipment to close. At the same time, the signal processing module transmits the shutdown signal to the control system. The control system controls the electric valve of the water pump to close, and the laboratory energy-saving constant pressure water supply system and refrigeration equipment return to standby state.

[0045] Compared with the prior art, the present invention has the following advantages and effects:

[0046] (1) The present invention uses a terminal water management system to synchronously associate the operating status (start or stop) of the refrigeration equipment with the opening and closing status of the electric water valve of the refrigeration equipment. When the refrigeration equipment is started, water is supplied, and when the refrigeration equipment is stopped, water is cut off, thereby realizing automatic control of terminal water use without the need for human operation. Compared with the prior art, the water consumption is greatly reduced and electric energy is saved.

[0047] (2) The present invention uses a water pump energy-saving control module to synchronously associate the operating state of the refrigeration equipment with the opening and closing state of the water pump electric valve, and the electric valve is synchronized with the operation of the water pump (the electric valve opens the water pump to run, and the electric valve closes the water pump to stop), that is, the start and stop states of the refrigeration equipment are synchronously associated with the start and stop states of the water pump unit, thereby avoiding energy waste due to human negligence when the water equipment is not in use, thereby achieving energy saving.

[0048] (3) The present invention uses a constant pressure water supply control module to perform logical operations based on the system's supply and return water pressure difference and the set pressure difference, and controls the operation of the industrial frequency pump and the variable frequency pump to achieve intelligent constant pressure water supply; the industrial frequency pump and the variable frequency pump are combined to reduce the equipment purchase cost, and the water pumps serve as backup pumps for each other, thereby improving the reliability and stability of the system.

[0049] (4) The present invention uses a cooling tower energy-saving control module to perform centralized temperature control on the cooling system of the cooling tower according to the supply and return water temperature difference of the cooling tower, thereby ensuring that the system fully utilizes the water vapor entropy difference, avoiding energy waste and improving energy-saving effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0051] Figure 1 It is a schematic diagram of the system structure of the laboratory energy-saving constant pressure water supply system (the cooling tower adopts an open cooling tower) of the present invention;

[0052] Figure 2 It is a schematic diagram of the system structure of the laboratory energy-saving constant pressure water supply system (the cooling tower adopts a closed cooling tower) of the present invention;

[0053] Figure 3 It is a schematic diagram of the control link of the present invention;

[0054] Figure 4 It is a structural schematic diagram of a water storage tank of the present invention from a first viewing angle;

[0055] Figure 5 It is a structural schematic diagram of the water storage tank of the present invention from a second viewing angle;

[0056] Figure 6 It is a flow chart of the water supply method based on the laboratory energy-saving constant pressure water supply system of the present invention.

[0057] In the figure: 1 is the first-level water storage tank; 2 is the second-level water storage tank; 3 is the third-level water storage tank; 4 is the water replenishment port; 5 is the inspection port; 6 is the barrier A; 7 is the barrier B; 8 is the coarse filter screen; 9 is the fine filter screen. DETAILED DESCRIPTION

[0058] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0059] Example 1

[0060] like Figure 1 to Figure 2 As shown, a laboratory energy-saving constant-pressure water supply system includes a control system, a terminal water management system, a cooling tower, a water pump unit, a valve control system and a measurement system. The cooling tower and the water pump unit supply water to the refrigeration equipment through a water supply pipe, and the refrigeration equipment is connected to the cooling tower through a return pipe. The valve control system includes an electric water valve of the refrigeration equipment and an electric valve of the water pump. The terminal water management system is used to control the opening and closing state of the electric water valve of the refrigeration equipment according to the operating status signal of the refrigeration equipment. The control system includes a water pump energy-saving control module and a constant-pressure water supply control module.

[0061] The water pump energy-saving control module is used to control the opening and closing state of the water pump electric valve according to the operating state signal of the refrigeration equipment transmitted by the terminal water management system;

[0062] The constant pressure water supply control module is used to calculate the supply and return water pressure difference according to the total water outlet pressure and the total return water pressure measured by the measurement system, and perform logical operations based on the supply and return water pressure difference and the set pressure difference to control the operating status of the industrial frequency pump and the variable frequency pump of the water pump unit.

[0063] Specifically, the present invention provides an energy-saving constant-pressure water supply system suitable for laboratory cooling water. According to the characteristics of laboratory cooling water, the system realizes automatic control of cooling water supply and effectively reduces energy consumption from multiple aspects. The cooling tower, water pump unit, valve control system and refrigeration equipment of the present invention form a water circulation water supply system through water pipes. The measurement system transmits the measurement signal to the control system. The control system controls the state of the water pump unit by controlling the valve control system after logical operation. The cooling tower includes an open cooling tower and a closed cooling tower, respectively. Figure 1 and Figure 2 shown.

[0064] The present invention uses the terminal water management system to synchronously associate the operating status (start or stop) of the refrigeration equipment with the opening and closing status of the electric water valve of the refrigeration equipment. When the refrigeration equipment is started, water is supplied, and when the refrigeration equipment is stopped, water is cut off. In this embodiment, the terminal water management system monitors the operating status of water-cooled refrigeration equipment such as compressors at the water-using end in real time. When the start signal of the compressor is received, the terminal water management system controls the electric water valve to open. When the stop signal of the compressor is received, the electric water valve is controlled to close with a delay to cut off the use of cooling water. Compared with the prior art, while ensuring the stable operation of the equipment, the water consumption is greatly reduced and electric energy is saved.

[0065] Problems with the existing technology: The water-using end equipment must ensure the supply of cooling water during operation. The operation of the water-using end equipment is divided into heating, high temperature, cooling and low temperature stages. The compressor starts in the cooling and low temperature stages, and does not start in the heating and high temperature stages. In particular, there are multiple sets of compressors in large systems, and it is not necessary for all compressors to start in the cooling and low temperature stages. In the existing technology, cooling water is still continuously supplied during the compressor non-starting stage, which will cause a huge waste of energy. For example, the user-side equipment executes a 24-hour cycle, including 10 hours of high temperature, 2 hours of cooling, 10 hours of low temperature, and 2 hours of heating. The compressor does not work for 12 hours. The water-using end equipment does not actually need cooling water to operate, which causes 12 hours of energy waste. In the water supply system, assuming that two sets of cascade 30-HP compressors use 50T / h of water, a 10kW pump unit motor and a 4kW cooling tower fan are needed to supply 50T / h of cooling water. The 24-hour power loss reaches 168kWh, and the annual power consumption is more than 61,000kWh. If only one set of cascade 30-HP compressor needs to be operated in the low-temperature stage, the waste will be even more serious.

[0066] The control system of the present invention uses a PLC controller to achieve automatic control. The water pump energy-saving control module synchronizes the operating state of the refrigeration equipment with the opening and closing state of the water pump electric valve, and the electric valve is synchronized with the water pump operation (the electric valve opens the water pump to run, and the electric valve closes the water pump to stop), that is, the start and stop state of the refrigeration equipment is synchronized with the start and stop state of the water pump unit. In this embodiment, after the terminal water management system receives the operating state signal of the refrigeration equipment, it sends the signal to the control system at the same time. When the control system receives the shutdown signal of the compressor, the control system automatically determines and controls the water pump unit to shut down, avoiding energy waste due to personnel negligence and achieving energy saving.

[0067] The constant pressure water supply control module of the present invention controls the operation of the variable frequency pump and the power frequency pump in the water pump unit according to the supply and return water pressure difference, thereby realizing intelligent constant pressure control. In this embodiment, the supply and return water pressure difference between the water inlet end (corresponding to the water outlet end of the water pump unit) and the water outlet end (corresponding to the return water end of the cooling tower) of the water end device is used to determine whether the system water supply meets the use flow requirements. According to the change in water consumption, by adjusting the pump speed of the variable frequency pump or increasing or decreasing the number of operating power frequency pumps, the water supply is controlled, constant pressure water supply is realized, and the basic energy consumption of laboratory operation is reduced.

[0068] The valve control system also includes a manual switch for the cooling tower and a manual switch for the water pump, ensuring that the water supply system can not only realize automatic control of water supply, but also manual control of water supply, which increases reliability and facilitates maintenance of the system equipment.

[0069] The terminal water management system includes a signal processing module, a time delay relay and an intermediate relay. The signal processing module is used to receive and process the status signal of the refrigeration equipment, as follows:

[0070] When receiving a start signal from the refrigeration equipment, the signal processing module controls the electric water valve of the refrigeration equipment to open through an intermediate relay;

[0071] When receiving the shutdown signal of the refrigeration equipment, the signal processing module controls the delay relay to delay the set time limit, and then controls the electric water valve of the refrigeration equipment to close through the intermediate relay.

[0072] Specifically, in this embodiment, each terminal water management module corresponds to one refrigeration equipment. When the system is large and the system spacing is relatively large, multiple signal processing modules need to be set for management. The signal processing module uses multi-channel input and output, and the number of channels is matched according to the size of the refrigeration equipment system. When the water-using end refrigeration equipment is running, it will send a refrigeration instruction to control the start and stop of the refrigeration equipment. When the refrigeration equipment is started, the signal processing module obtains the refrigeration instruction. The signal processing module controls the electric water valve of the refrigeration equipment to open through the intermediate relay, and introduces cooling water for cooling; when the refrigeration equipment is shut down, because the heat exchange has not been completed in the system, the signal processing module sends the refrigeration equipment shutdown signal to the delay relay. After the delay setting is realized, the delay relay controls the electric water valve of the refrigeration equipment to close through the intermediate relay to achieve water saving and reduce energy consumption. The signal processing module has an active sending and receiving function. The signal processing module has a high priority in the water supply system and obeys the control instruction of the refrigeration equipment first to ensure the operation or stop of the refrigeration equipment.

[0073] The terminal water management system sends the operating status signal of the refrigeration equipment to the control system through the wireless transmission module. The water pump energy-saving control module is specifically used to perform logical operations according to the operating status signal of the refrigeration equipment, determine the water consumption, and control the opening and closing states of the electric valves of each water pump according to the water consumption, as follows:

[0074] When the water consumption is greater than the system surplus, the water pump electric valve is controlled to open to increase the operation of the water pump unit;

[0075] When the water consumption is less than the system margin, the water pump electric valve is controlled to close to reduce the operation of the water pump unit.

[0076] Specifically, the wireless transmission module is completed through a wireless radio frequency transmitter and receiver. Figure 3 The wireless transmission module includes a wireless transmission module-terminal provided at the terminal water management system end and a wireless transmission module-switchboard provided at the control system end. The signal processing module of the terminal water management system has an active transceiver function, and the wireless transmission module-terminal has an active and passive signal transmission function, thereby realizing wireless transmission without wiring and realizing information collection function.

[0077] When the water-using end equipment is running, it will send a refrigeration command to control the start and stop of the refrigeration equipment. When the refrigeration equipment starts or stops, the terminal water management system will receive the command and transmit the operating status signal of the refrigeration equipment to the wireless transmission module-switchboard through the wireless transmission module-terminal. The control system determines the system margin through logical operation based on the operating status signal of the refrigeration equipment to prepare for water use. The signal processing module of each terminal water management system has an independent identification code in the water supply system, corresponding to the cooling water required by the corresponding refrigeration equipment. For example, when the variable frequency pump operating frequency of the water pump unit reaches 49Hz, the system water supply is 230T / h, and when the variable frequency pump is at full frequency of 50Hz, the system water supply is 250T / h. At this time, the system margin is 20T / h. When the control system determines through logical operation that there is an increase of 40T / h in the demand for refrigeration equipment, the water pump energy-saving control module will automatically determine to deliver the power frequency pump of the water pump unit in advance to avoid sudden changes in system pressure due to sudden increase in water consumption and insufficient system margin, which may affect other water-using end equipment.

[0078] The water pump unit includes at least two power frequency pumps and one variable frequency pump, the variable frequency pump is equipped with a separate frequency converter for control, and the constant pressure water supply control module is specifically used for:

[0079] The supply and return water pressure difference is calculated based on the total water outlet pressure monitored by the water outlet pressure sensor at the water outlet of the pump unit and the total water supply pressure monitored by the return water pressure sensor at the return water end of the cooling tower to determine whether the supply and return water pressure difference is lower than the set pressure difference.

[0080] If yes, the inverter output frequency is increased first to increase the speed of the variable frequency pump. If the supply and return water pressure difference is still lower than the set pressure difference after the variable frequency pump reaches full frequency, the industrial frequency pump is started again until the supply and return water pressure difference increases to the set pressure difference.

[0081] If not, the output frequency of the inverter is reduced first to reduce the speed of the variable frequency pump. If the supply and return water pressure difference is still higher than the set pressure difference after the variable frequency pump reaches the minimum operating frequency, reduce the industrial frequency pump until the supply and return water pressure difference is reduced to the set pressure difference.

[0082] Specifically, the constant pressure water supply control module adopts variable frequency constant pressure programmable control, fully automatic operation, and significant energy saving effect: by controlling the coordinated operation of the industrial frequency pump and the variable frequency pump, the frequency converter is used to adjust the speed of the variable frequency pump, thereby realizing variable frequency constant pressure water supply. Among them, the frequency converter is used to supply power to the output of the variable frequency pump. The frequency converter outputs power of different frequencies to control the operating frequency of the variable frequency pump to adjust the speed of the variable frequency pump. When the frequency converter is at full frequency, the variable frequency pump will also work at full frequency. At this time, the variable frequency pump is equivalent to the industrial frequency pump, so that the pressure of the pipeline network is free of impact, the water supply pressure is stable, and the working pressure can be set as needed, which greatly improves the unstable pressure phenomenon when the water pump is running at full speed; in addition, by controlling the operation and stop of the soft starter to realize the operation and stop of the industrial frequency pump, the water pump is soft-started in a cycle, and the start and stop are smooth, reducing equipment loss; when there is no water in use, the water pump can be shut down slowly without water hammer.

[0083] The water pump is composed of two variable frequency pumps and more than two power frequency pumps. The variable frequency pumps are used as backup for each other (for turbine use) and the power frequency pumps are used as backup for each other. In the prior art, one power frequency pump is used and the other is used as backup. In the present invention, a power frequency pump and one variable frequency pump are configured according to the maximum demand for cooling water in the water supply system, which greatly reduces the system's requirements for water pump backup and reduces the equipment purchase cost.

[0084] This embodiment illustrates the configuration and use of the industrial frequency pump and the variable frequency pump in the present invention through a typical application case. The maximum demand for laboratory cooling water is 1250T / h (the cooling demand of the refrigeration equipment is 2000T / h, and there is a common coefficient for cooling water, that is, not all equipment is running at the highest load), the water pump is configured to 250T / h, and the total of 6 water pumps is 1500T / h, including 2 variable frequency pumps and 4 processing frequency pumps, the power of a single water pump is 45kW, the minimum operating energy consumption of the variable frequency pump is 16kW, the cooling tower is configured to 1250T / h, and the water consumption of the water-using end equipment is 25 tons / hour / unit, of which each refrigeration equipment is equipped with 2 sets of refrigeration units, and a total of 38 sets of refrigeration equipment are in operation.

[0085] When the water-using refrigeration equipment just starts to operate, the constant pressure water supply system of the present invention is started, and the variable frequency pump operates at a minimum of 16kW to meet the system working requirements;

[0086] When half of the 38 refrigeration equipment are in normal operation, the water consumption is 950T / h (without considering the sharing coefficient), and the water pumps are operated by 1 variable frequency pump and 3 power frequency pumps;

[0087] At full load, that is, all 38 sets of refrigeration equipment are running, the sharing coefficient is 0.7, the water consumption is 1330T / h, and the water pumps consist of 2 variable frequency pumps and 4 industrial frequency pumps working simultaneously.

[0088] Under underload, that is, when 1 / 4 of the 38 refrigeration equipment are in operation, the water consumption is 475T / h (without considering the sharing coefficient). At this time, the water pumps consist of 1 variable frequency pump and 1 industrial frequency pump working simultaneously.

[0089] The control system further includes a cooling tower energy-saving control module, which is used to calculate the supply and return water temperature difference according to the supply water temperature detected by the supply water temperature sensor at the water outlet of the cooling tower and the return water temperature detected by the return water temperature sensor at the return water end of the cooling tower, and to perform a logical operation based on the supply and return water temperature difference and the set water temperature difference to determine the operating state of the heat dissipation system of the cooling tower, as follows:

[0090] Determine whether the supply and return water temperature difference is higher than the set water temperature difference.

[0091] If yes, start the spray pumps of the closed cooling tower in sequence. When the supply and return water temperature difference is still higher than the set water temperature difference after all the spray pumps are turned on, turn on the fan again until the maximum cooling capacity of the cooling tower is reached;

[0092] If not, turn off the fan. When the supply and return water temperature difference is still higher than the set water temperature difference, turn off the spray pumps of the closed cooling tower in turn until the supply and return water temperature difference reaches the set water temperature difference.

[0093] Specifically, the cooling tower includes a closed cooling tower and a start cooling tower, and only the closed cooling tower is equipped with a spray pump. After the number of cooling towers is automatically controlled according to the water consumption, the heat dissipation of each cooling tower is preferentially activated by the cooling tower's heat dissipation pipe, that is, the cooling tower's own heat dissipation area is used for heat dissipation. At this time, the spray pump of the closed cooling tower is not turned on and the fan of the cooling tower is not running. When the supply and return water temperature difference is higher than the set water temperature difference, the spray pump will be gradually increased to realize the use of spray water evaporation to take away heat. When the supply and return water temperature difference is still higher than the set water temperature difference after all the spray pumps are turned on, the fan, that is, the heat dissipation fan, will be gradually increased to finally reach the maximum cooling capacity of the cooling tower. After the supply and return water temperature difference is lower than the set water temperature difference, it will gradually reverse and close. This process can reduce energy consumption, ensure that the temperature in the water supply system is relatively stable, and improve the stability of the water end system. The energy-saving control module realizes intelligent control of the cooling tower by utilizing the temperature difference between the supply and return water of the cooling tower, ensuring that the water vapor entropy difference can be fully utilized to improve the energy-saving effect.

[0094] The control system also includes an online monitoring module, which is used to transmit the equipment operation status signal measured by the measurement system to the controller. The controller determines the fault condition of the equipment based on the equipment operation status signal and issues a fault alarm reminder. At the same time, the equipment operation status signal is displayed online through the human-machine interface of the industrial computer.

[0095] The measuring system comprises a sensing component and a measuring component, wherein the sensing component comprises a water outlet pressure sensor, a return water pressure sensor, a water supply temperature sensor and a return water temperature sensor, and the measuring component comprises a pressure measuring component, a temperature measuring component and a power measuring component.

[0096] The pressure measurement component is used to collect pressure signals from the water outlet pressure sensor and the water return pressure sensor, and transmit the pressure signals to the control system;

[0097] The temperature measurement component is used to collect temperature signals from the water supply temperature sensor and the return water temperature sensor, and transmit the temperature signals to the control system;

[0098] The power measurement component is used to measure the electrical operating parameters of the corresponding equipment and transmit the electrical operating parameters to the control system.

[0099] Specifically, the power measurement component includes an ammeter, a voltmeter and an electric energy meter, which measure current, voltage and energy parameters respectively. Each parameter signal is transmitted to the control system through RS485 and displayed by the industrial computer of the control system. The control system determines whether the motor of the water pump unit has abnormal operation by analyzing the current and voltage, such as phase loss or three-term imbalance. When an abnormality occurs, an online alarm reminder is implemented; the corresponding equipment includes water pump units, fans, spray pumps and cooling towers, and the power consumption of the above equipment is monitored online through the electric energy meter. The operating conditions of each equipment in the water supply system are monitored in real time through the online monitoring module to reduce safety risks and improve the stability of equipment operation.

[0100] like Figure 1 As shown, the cooling tower adopts an open cooling tower, the water outlet, the water reservoir, the water pump unit and the water inlet of the refrigeration equipment of the closed cooling tower are connected in sequence through a water supply pipe, and the return water outlet of the cooling tower is connected to the water outlet of the refrigeration equipment through a return water pipe.

[0101] The water storage tank is constructed with a primary water storage tank, a secondary water storage tank and a tertiary water storage tank, which are arranged horizontally, a barrier A is provided between the primary water storage tank and the secondary water storage tank, a coarse filter is installed above the barrier A, a barrier B is provided between the secondary water storage tank and the tertiary water storage tank, a fine filter is installed above the barrier B, the primary water storage tank is connected with the water outlet of the closed cooling tower through a water supply pipe, the tertiary water storage tank is connected with the water pump unit through a water supply pipe, a water replenishment port is provided at the top of the tertiary water storage tank, and maintenance ports are provided at the tops of the primary water storage tank, the secondary water storage tank and the tertiary water storage tank.

[0102] Specifically, Figure 4 and Figure 5As shown, the cooling water after cooling by the open cooling tower flows through the water pipe to the first-level water storage tank, where the cooling water is collected to settle large particles of impurities in this first-level water storage tank; after the water flow slows down, it flows smoothly through the coarse filter to further filter the large particles of impurities and then enters the second-level water storage tank. After secondary sedimentation in this second-level water storage tank, the cooling water passes through the fine filter to filter the mayfly particles, and then enters the third-level water storage tank to wait for the water pump unit to absorb water. The water pump unit takes water from the water tank through the water supply pipe, wherein the coarse filter and the fine filter use honeycomb filter cotton, the inspection port is a channel for personnel to enter and exit for cleaning and to check the water quality, and the water replenishment port is the filling port for cooling water. This embodiment is provided with a quick water replenishment port and a conventional water replenishment port. The quick water replenishment port is convenient for quick filling after equipment cleaning, and the conventional water replenishment port is convenient for replenishing the water loss caused by evaporation of the cooling tower. The water storage tank of the present invention can greatly reduce the vertical water demand, reduce the foundation load of the cooling tower and the equipment manufacturing process requirements; the use of a sedimentation and filtration structure can greatly reduce the risk of equipment failure due to dirt and blockage in the later stage; the use of a segmented structure and a honeycomb filter can ensure the effective filtration of suspended solids and reduce the impact of the surrounding environment of the cooling tower.

[0103] It also includes a soft water system, which includes a water softener. The water softener is used to filter the municipal tap water in the water supply pipe before supplying the water to the refrigeration equipment.

[0104] Specifically, the water softener includes a quartz sand tank, an activated carbon tank and an ion exchange resin. The tap water is filtered through a quartz sand tank to remove large particles and impurities in the tap water, and then enters the activated carbon tank to further adsorb and filter harmful substances and suspended matter. Finally, the water enters the ion exchange resin to replace metal ions such as calcium and magnesium in the water with sodium ions, thereby achieving the purpose of softening the water quality.

[0105] When the cooling tower adopts a closed cooling tower, the soft water system also includes a constant pressure water pump and a liquid level sensor. The cooling water of the water softener is pressurized by the constant pressure water pump and then supplied to the refrigeration equipment. When the liquid level monitored by the liquid level sensor at the water outlet of the water softener is lower than the set water replenishment level (has not reached the alarm water level), the water softener will make water and replenish the water to the water reservoir. When the liquid level reaches the set water level, the water softener stops making water. When the liquid level reaches the alarm water level, the control system will receive an alarm signal and perform shutdown protection.

[0106] When the cooling tower adopts an open cooling tower, the cooling water of the water softener is directly pressurized by the water pump unit and then supplied to the refrigeration equipment.

[0107] Example 2

[0108] like Figure 6 The figure shows a flow chart of a water supply method based on the above-mentioned laboratory energy-saving constant pressure water supply system, including the following steps:

[0109] S1. Turn on the power of the laboratory energy-saving constant pressure water supply system and refrigeration equipment and enter the standby state;

[0110] S2. Start the refrigeration equipment. The signal processing module of the terminal water management system transmits the start signal to the control system through the wireless transmission module. The control system performs logical operations based on the start signal to determine the water consumption. The water pump unit is started in advance based on the water consumption. The water pump unit starts to run at a low frequency and pressurizes the system to a set pressure difference within a preset time.

[0111] S3, at the same time, the signal processing module sends a command to the intermediate relay to control the electric water valve of the refrigeration equipment to open, so as to realize the cooling water supply;

[0112] S4. The control system determines the water consumption in real time according to the operating status signal of the refrigeration equipment transmitted by the terminal water management system, and adjusts the operating status of the water pump unit according to the water consumption, as follows:

[0113] When the water consumption is greater than the system margin, the water pump electric valve is controlled to open to increase the operation of the water pump unit; when the water consumption is less than the system margin, the water pump electric valve is controlled to close to reduce the operation of the water pump unit;

[0114] S5. The control system calculates the supply and return water pressure difference based on the total supply water pressure and the total return water pressure measured by the measurement system, and controls the operation of the water pump unit according to the supply and return water pressure difference and the set pressure difference, as follows:

[0115] When the supply and return water pressure difference is lower than the set pressure difference, the output frequency of the inverter is increased first to increase the speed of the variable frequency pump. If the supply and return water pressure difference is still lower than the set pressure difference after the variable frequency pump reaches full frequency, the industrial frequency pump is started again until the supply and return water pressure difference increases to the set pressure difference.

[0116] When the supply and return water pressure difference is higher than the set pressure difference, the inverter output frequency is reduced first to reduce the speed of the variable frequency pump. If the supply and return water pressure difference is still higher than the set pressure difference after the variable frequency pump reaches the minimum operating frequency, the power frequency pump is reduced until the supply and return water pressure difference is reduced to the set pressure difference.

[0117] S6. Real-time online monitoring of the operating status of the water pump unit and cooling tower through the human-machine interface of the control system;

[0118] S7, the control system controls the power frequency pump and the variable frequency pump to operate the turbine according to the operation time of the water pump unit: when the operation time of the power frequency pump reaches the first preset time, the power frequency pump is operated according to the first-start-first-stop principle; when the operation time of the variable frequency pump reaches the second preset time, the two variable frequency pumps are operated;

[0119] S8. Shut down the refrigeration equipment. The signal processing module of the terminal water management system sends the shutdown signal to the delay relay. After the set time delay, the intermediate relay controls the electric water valve of the refrigeration equipment to close. At the same time, the signal processing module transmits the shutdown signal to the control system. The control system controls the electric valve of the water pump to close, and the laboratory energy-saving constant pressure water supply system and refrigeration equipment return to standby state.

[0120] Specifically, in this embodiment, if a unit is in long-term operation, the second preset duration is set to 2 days, that is, the two variable frequency pumps operate the turbine every 2 days, and the first preset duration is set to 1 day, that is, the power frequency pump operates the turbine once a day, so as to avoid excessive load on a single water pump; when there are more than 2 power frequency pumps, the first preset duration is set according to the actual operation situation to switch the power frequency pump operation, and the first-on-first-off strategy is adopted to extend the life of the water pump. In order to ensure the water demand at the water user end, the electric valves of the power frequency pump and the variable frequency pump act synchronously during the operation switching process to avoid problems such as liquid backflow.

[0121] The method of the present invention synchronously associates the operating state (start or stop) of the refrigeration equipment with the opening and closing state of the electric water valve of the refrigeration equipment. When the refrigeration equipment is started, water is supplied, and when the refrigeration equipment is stopped, water is cut off. In this embodiment, the terminal water management system monitors the operating state of the water-cooled refrigeration equipment such as the compressor at the water-using end in real time. When the start signal of the compressor is received, the terminal water management system controls the electric water valve to open. When the stop signal of the compressor is received, the electric water valve is controlled to close with a delay to cut off the use of cooling water. Compared with the prior art, while ensuring the stable operation of the equipment, the water consumption is greatly reduced and electric energy is saved.

[0122] The method of the present invention adopts PLC automatic control technology to realize automatic control of water supply, and synchronously associates the operating state of the refrigeration equipment with the opening and closing state of the electric valve of the water pump, and the electric valve is synchronized with the operation of the water pump (the electric valve opens the water pump to run, and the electric valve closes the water pump to stop), that is, the start and stop states of the refrigeration equipment are synchronously associated with the start and stop states of the water pump unit. When the refrigeration equipment is shut down and no water is needed, the water pump is automatically shut down, thereby avoiding energy waste due to negligence of personnel and achieving energy saving.

[0123] The method of the present invention controls the operation of the variable frequency pump and the power frequency pump in the water pump unit according to the supply and return water pressure difference, thereby realizing intelligent constant pressure control. The pump speed of the variable frequency pump is adjusted according to the change in water consumption, or the number of running power frequency pumps is increased or decreased, thereby controlling the water supply, realizing constant pressure water supply, and reducing the basic energy consumption of laboratory operation.

[0124] The above embodiments are preferred implementations of the present invention and are not intended to limit the present invention. Any other changes or other equivalent replacement methods that do not deviate from the technical solutions of the present invention are included in the protection scope of the present invention.

Claims

1. A laboratory energy-saving constant-pressure water supply system, characterized in that, it includes a control system, a terminal water management system, a cooling tower, a water pump unit, a valve control system and a measurement system. The cooling tower and the water pump unit supply water to the refrigeration equipment through a water supply pipe, and the refrigeration equipment is connected to the cooling tower through a return water pipe. The valve control system includes an electric water valve for the refrigeration equipment and an electric water valve for the water pump. The terminal water management system is used to control the opening and closing state of the electric water valve for the refrigeration equipment according to the operation status signal of the refrigeration equipment. The control system includes a water pump energy-saving control module and a constant-pressure water supply control module. The water pump energy-saving control module is used to control the opening and closing state of the electric water valve for the water pump according to the operation status signal of the refrigeration equipment transmitted by the terminal water management system; The constant-pressure water supply control module is used to calculate the pressure difference between the supply water and the return water according to the total outlet pressure measured by the measurement system and the total return water pressure, and perform logical operations based on the pressure difference between the supply water and the return water and the set pressure difference to control the operation states of the industrial-frequency pump and the variable-frequency pump of the water pump unit.

2. The laboratory energy-saving constant-pressure water supply system according to claim 1, characterized in that, the terminal water management system includes a signal processing module, a time-delay relay and an intermediate relay. The signal processing module is used to receive and process the status signal of the refrigeration equipment, specifically as follows: When receiving the start signal of the refrigeration equipment, the signal processing module controls the opening of the electric water valve for the refrigeration equipment through the intermediate relay; When receiving the stop signal of the refrigeration equipment, the signal processing module controls the time-delay relay for a set time limit through the time-delay relay, and then controls the closing of the electric water valve for the refrigeration equipment through the intermediate relay.

3. The laboratory energy-saving constant-pressure water supply system according to claim 1, characterized in that, the terminal water management system sends the operation status signal of the refrigeration equipment to the control system through a wireless transmission module. The water pump energy-saving control module is specifically used to perform logical operations according to the operation status signal of the refrigeration equipment, determine the water consumption, and control the opening and closing states of each electric water valve for the water pump according to the water consumption, specifically as follows: When the water consumption is greater than the system margin, control the electric water valve for the water pump to open to increase the operation of the water pump unit; When the water consumption is less than the system margin, control the electric water valve for the water pump to close to reduce the operation of the water pump unit.

4. The laboratory energy-saving constant-pressure water supply system according to claim 1, characterized in that, the water pump unit includes at least 2 industrial-frequency pumps and 1 variable-frequency pump. The variable-frequency pump is equipped with a separate frequency converter for control. The constant-pressure water supply control module is specifically used for: Calculating the pressure difference between the supply water and the return water according to the total outlet pressure monitored by the outlet pressure sensor at the water outlet end of the water pump unit and the total supply water pressure monitored by the return water pressure sensor at the return water end of the cooling tower, and judging whether the pressure difference between the supply water and the return water is lower than the set pressure difference. If so, preferentially increase the output frequency of the frequency converter to increase the speed of the variable-frequency pump. If the pressure difference between the supply water and the return water is still lower than the set pressure difference after the variable-frequency pump reaches the full frequency, then start the industrial-frequency pump until the pressure difference between the supply water and the return water increases to the set pressure difference. If not, the output frequency of the frequency converter is preferentially reduced to lower the rotational speed of the variable-frequency pump. If the differential pressure between the supply and return water still exceeds the set differential pressure after the variable-frequency pump reaches the minimum operating frequency, the power-frequency pump is further reduced until the differential pressure between the supply and return water is reduced to the set differential pressure.

5. A laboratory energy-saving constant-pressure water supply system according to claim 1, characterized in that, the control system further includes a cooling tower energy-saving control module, and the cooling tower energy-saving control module is used to calculate the differential temperature between the supply and return water according to the supply water temperature detected by the supply water temperature sensor at the outlet end of the cooling tower and the return water temperature detected by the return water temperature sensor at the return water end of the cooling tower, and perform a logical operation based on the differential temperature between the supply and return water and the set differential temperature to determine the operating state of the heat dissipation system of the cooling tower, specifically as follows: Judge whether the differential temperature between the supply and return water is higher than the set differential temperature, If so, the spray pumps of the closed cooling tower are sequentially turned on. When the differential temperature between the supply and return water still exceeds the set differential temperature after all the spray pumps are turned on, the fan is then turned on until the maximum cooling capacity of the cooling tower is reached; If not, the fan is turned off. When the differential temperature between the supply and return water still exceeds the set differential temperature, the spray pumps of the closed cooling tower are sequentially turned off until the differential temperature between the supply and return water reaches the set differential temperature.

6. A laboratory energy-saving constant-pressure water supply system according to claim 1, characterized in that, the control system further includes an on-line monitoring module, and the on-line monitoring module is used to transmit the equipment operating state signal measured by the measurement system to the controller. The controller judges the fault condition of the equipment according to the equipment operating state signal and gives a fault alarm reminder, and at the same time displays the equipment operating state signal on-line through the human-machine interface of the industrial control computer.

7. A laboratory energy-saving constant-pressure water supply system according to claim 6, characterized in that, the measurement system includes a sensing component and a measurement component. The sensing component includes an outlet pressure sensor, a return water pressure sensor, a supply water temperature sensor and a return water temperature sensor. The measurement component includes a pressure measurement component, a temperature measurement component and a power measurement component. The pressure measurement component is used to collect the pressure signals of the outlet pressure sensor and the return water pressure sensor and transmit the pressure signals to the control system; The temperature measurement component is used to collect the temperature signals of the supply water temperature sensor and the return water temperature sensor and transmit the temperature signals to the control system; The power measurement component is used to measure the electrical operating parameters of the corresponding equipment and transmit the electrical operating parameters to the control system.

8. A laboratory energy-saving constant-pressure water supply system according to claim 1, characterized in that, the cooling tower adopts an open cooling tower. The outlet of the closed cooling tower, the water storage tank, the water pump unit and the inlet of the refrigeration equipment are sequentially connected by a water supply pipe. The return water inlet of the cooling tower is connected to the outlet of the refrigeration equipment by a return water pipe. The reservoir structure has a first - stage water storage bin, a second - stage water storage bin, and a third - stage water storage bin. The first - stage water storage bin, the second - stage water storage bin, and the third - stage water storage bin are arranged horizontally. A barrier A is provided between the first - stage water storage bin and the second - stage water storage bin, and a coarse filter screen is installed above the barrier A. A barrier B is provided between the second - stage water storage bin and the third - stage water storage bin, and a fine filter screen is installed above the barrier B. The first - stage water storage bin is communicated with the water outlet of the closed - type cooling tower through a water supply pipe. The third - stage water storage bin is communicated with the water pump unit through a water supply pipe. A water replenishment port is opened at the top of the third - stage water storage bin. Maintenance ports are opened at the tops of the first - stage water storage bin, the second - stage water storage bin, and the third - stage water storage bin.

9. A laboratory energy - saving constant - pressure water supply system according to claim 1, characterized in that, it further includes a soft - water system. The soft - water system includes a water softener, and the water softener is used to filter the tap water supplied by the municipal government in the water supply pipe before supplying water to the refrigeration equipment.

10. A water supply method for a laboratory energy - saving constant - pressure water supply system according to any one of claims 1 - 9, characterized in that, it includes the steps: S1. Turn on the power of the laboratory energy - saving constant - pressure water supply system and the refrigeration equipment, and enter the standby state; S2. Start the refrigeration equipment. The signal processing module of the terminal water management system transmits the start signal to the control system through the wireless transmission module. The control system performs logical operations according to the start signal to determine the water consumption, starts the water pump unit in advance according to the water consumption. The water pump unit starts to operate at a low frequency and increases the system pressure to the set pressure difference within a preset time; S3. At the same time, the signal processing module sends an instruction to the intermediate relay to control the opening of the electric water valve of the refrigeration equipment to realize the supply of cooling water; S4. The control system continuously judges the water consumption according to the operation state signal of the refrigeration equipment transmitted by the terminal water management system, and adjusts the operation state of the water pump unit according to the water consumption. Specifically as follows: When the water consumption is greater than the system margin, control the opening of the water pump electric valve to increase the operation of the water pump unit. When the water consumption is less than the system margin, control the closing of the water pump electric valve to reduce the operation of the water pump unit; S5. The control system calculates the pressure difference between the supply water and the return water based on the total supply water pressure and the total return water pressure measured by the measurement system, and controls the operation of the water pump unit according to the pressure difference between the supply water and the return water and the set pressure difference. Specifically as follows: When the pressure difference between the supply water and the return water is lower than the set pressure difference, preferentially increase the output frequency of the frequency converter to increase the speed of the variable - frequency pump. If the pressure difference between the supply water and the return water is still lower than the set pressure difference after the variable - frequency pump reaches the full frequency, then start the industrial - frequency pump until the pressure difference between the supply water and the return water is increased to the set pressure difference; When the pressure difference between the supply water and the return water is higher than the set pressure difference, preferentially reduce the output frequency of the frequency converter to reduce the speed of the variable - frequency pump. If the pressure difference between the supply water and the return water is still higher than the set pressure difference after the variable - frequency pump reaches the lowest operating frequency, then reduce the industrial - frequency pump until the pressure difference between the supply water and the return water is reduced to the set pressure difference; S6. Real - time online monitor the operation states of the water pump unit and the cooling tower through the human - machine interface of the control system; S7. The control system controls the industrial-frequency pump and the variable-frequency pump for operation according to their running durations: when the running duration of the industrial-frequency pump reaches the first preset duration, the industrial-frequency pump is operated according to the principle of "first start, first stop"; when the running duration of the variable-frequency pump reaches the second preset duration, the two variable-frequency pumps are operated to ensure that one variable-frequency pump is in standby mode. S8. Stop the refrigeration equipment. The signal processing module of the terminal water management system sends the stop signal to the time-delay relay. After a delay of the set time limit, the electric water valve of the refrigeration equipment is controlled to close through the intermediate relay. At the same time, the signal processing module transmits the stop signal to the control system, and the control system controls the closing of the water pump electric valve, and the laboratory energy-saving constant-pressure water supply system and the refrigeration equipment return to the standby state.

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