Circulating water variable flow energy-saving system based on resistance coefficient optimization

Abstract

The embodiment of the utility model discloses a circulating water variable-flow energy-saving system based on resistance coefficient optimization. The circulating water variable-flow energy-saving system comprises a variable-flow energy-saving control system, cold and heat source equipment, end equipment, a bypass regulating valve, a circulating water pump, a frequency converter connected with the circulating water pump, a differential pressure sensor, a flow meter, a water supply temperature sensor and a return water temperature sensor. The embodiment provided by the utility model has the beneficial effects that the resistance coefficient and the pressure difference set value are dynamically adjusted according to the flow and the temperature difference change in the operation process, the pressure difference of the system is optimized in real time, the supply and demand consistency of the operation of the system is ensured, and the energy consumption is reduced; the circulating water flow is controlled through variable flow regulation, the reaction is sensitive, and the adverse effect of hysteresis of conventional temperature difference regulation is eliminated; and the comfort of the user and the energy-saving performance of the system are both considered.

Description

Technical Field

[0001] The utility model relates to the technical field of motor control, in particular to a circulating water variable flow energy-saving system based on resistance coefficient optimization. Background Art

[0002] Central air conditioning systems can be divided into three categories: central air conditioning water system, fluorine system and wind system. Water system central air conditioning uses water as refrigerant and is larger than traditional fluorine system. Water system central air conditioning is generally used in large buildings, mainly in the commercial market. The water system type is a small semi-centralized fan coil system, and all indoor loads are borne by the hot and cold water units. The fan coils in each room are connected to the hot and cold water units through pipes, and the cold and hot water provided are used for cooling and heating. The water system has flexible layout, good independent adjustment, and very high comfort. It can meet the needs of complex room types and independent operation of each room. In the central air conditioning water system or hot water system, if the circulating water flow is too small, it will not be able to meet the flow demand of the terminal equipment; if the circulating water flow is too large, it will increase the pipeline resistance and increase the energy consumption of distribution. Therefore, the primary pump variable flow technology is gradually applied to the central air conditioning water system and hot water system. The control method of water pump variable frequency speed regulation can automatically adjust the circulating water flow according to the load demand of the terminal equipment to achieve energy saving effect. The control methods of variable frequency speed regulation of water pumps can be divided into two types: temperature difference control method and pressure difference control method. The temperature difference control method controls the temperature difference of the supply and return pipes to keep constant so that the flow rate changes with the load. When the load decreases, the circulating water flow rate is reduced by reducing the speed of the water pump through the temperature difference controller and the water pump inverter. However, this regulation method is not suitable for systems with large end load differences, and the hysteresis of the temperature difference control method is poor, which affects the effect of the terminal equipment. The pressure difference control method refers to setting a pressure difference controller between the supply and return water mains. When the user's load demand changes, the electric regulating valve on the user's branch adjusts the opening to change the circulating water flow rate so that the terminal equipment is maintained at the set value. In order to maintain a constant pressure difference in the main pipe, the water pump adjusts the speed to adjust the flow rate and head to achieve a new balance between supply and demand. However, under partial load conditions, the user's demand for water decreases, and the constant pressure difference in the main pipe will cause unnecessary energy waste.

[0003] In order to respond to the change of terminal load in time, there have been related reports on variable flow control energy-saving technology. By adjusting the pressure difference set value with the valve opening at the most unfavorable terminal, the pump's delivery energy consumption is saved. However, the existing variable flow control scheme is not suitable for the case of non-uniform changes in terminal load, and no calculation method for updating the pressure difference set value is proposed. The adverse effects of the deviation of operating parameters on the user's comfort during the system dynamic adjustment process are ignored. Utility Model Content

[0004] The embodiment of the utility model provides a circulating water variable flow energy-saving system based on resistance coefficient optimization to solve the above technical problems.

[0005] In order to solve the above technical problems, the embodiment of the utility model proposes a circulating water variable flow energy-saving system based on resistance coefficient optimization, including: a variable flow energy-saving control system, a cold and heat source device, a terminal device, a bypass regulating valve, a circulating water pump and a frequency converter connected thereto, a pressure difference sensor, a flow meter, a water supply temperature sensor and a return water temperature sensor, wherein:

[0006] The terminal equipment includes one or a plurality of devices arranged in parallel, the bypass regulating valve is located on the water supply and return main pipe, and the circulating water flow rate is changed by adjusting the valve opening, the circulating water pump is located on the water supply main pipe and is frequency-controlled by a frequency converter, the differential pressure sensor is connected to the supply and return pipes to measure the pressure difference between the supply and return pipes, the flow meter is located on the water supply main pipe to measure the circulating water flow rate, the supply water temperature sensor and the return water temperature sensor are respectively located on the supply and return water main pipes to measure the supply and return water temperature difference; the frequency converter, bypass regulating valve, differential pressure sensor, flow meter, supply water temperature sensor and return water temperature sensor are all connected to the variable flow energy-saving control system.

[0007] Furthermore, the variable flow energy-saving control system has two built-in supply and return water pressure difference setting value algorithm models, which are used to correct the pressure difference according to the flow rate and the supply and return water temperature difference. Changes in the circulating water flow rate or temperature difference can cause changes in the resistance coefficient and change the flow setting value.

[0008] Furthermore, the variable flow energy-saving control system receives the temperature difference signals from the flow and temperature sensors and then inputs the built-in algorithm model to correct the resistance coefficient to obtain a supply and return water pressure difference set value, which is used to compare the PID regulation of the circulating water pump flow or the valve opening of the bypass regulating valve according to the supply and return water pressure difference set value and the actual supply and return water pressure difference measured value collected by the pressure difference sensor.

[0009] The beneficial effects of the embodiments provided by the utility model are as follows: the resistance coefficient and the pressure difference setting value are dynamically adjusted according to the flow rate and temperature difference changes during the operation process, and the system pressure difference is optimized in real time to ensure that the supply and demand of the system operation are consistent and energy consumption is reduced; the circulating water flow rate is controlled by variable flow regulation, which is sensitive and eliminates the adverse effects of the lag of conventional temperature difference regulation; and both user comfort and system energy saving are taken into account. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a schematic diagram of the framework of a circulating water variable flow energy-saving system based on resistance coefficient optimization in an embodiment of the utility model.

[0011] Figure 2 It is a model curve of a circulating water variable flow energy-saving system based on resistance coefficient optimization according to flow rate correction pressure difference in an embodiment of the utility model.

[0012] Description of Figure Numbers

[0013] Variable flow energy-saving control system 101, cold and heat source equipment 102, terminal equipment 103, bypass regulating valve 104, circulating water pump 105 and its connected frequency converter 106, pressure difference sensor 201, flow meter 202, water supply temperature sensor 203, return water temperature sensor 204. DETAILED DESCRIPTION

[0014] It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments may be combined with each other. The present utility model is further described in detail below in conjunction with the drawings and specific embodiments.

[0015] In the embodiments of the present invention, if there are directional indications (such as up, down, left, right, front, back, etc.), they are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0016] In addition, in the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0017] Please refer to Figure 1 The utility model embodiment of a circulating water variable flow energy-saving system based on resistance coefficient optimization includes a variable flow energy-saving control system 101, a cold and hot source device 102, a terminal device 103, a bypass regulating valve 104, a circulating water pump 105 and a frequency converter 106 connected thereto, a pressure difference sensor 201, a flow meter 202, a water supply temperature sensor 203 and a return water temperature sensor 204, wherein,

[0018] The terminal device 103 may include one or multiple devices arranged in parallel. The bypass regulating valve 104 is located on the water supply and return main pipes, and the circulating water flow rate is changed by adjusting the valve opening. The circulating water pump 105 is located on the water supply main pipe and is frequency-controlled by the frequency converter 106. The differential pressure sensor 201 is connected to the water supply and return pipes to measure the pressure difference between the water supply and return pipes. The flow meter 202 is located on the water supply main pipe to measure the circulating water flow rate. The water supply temperature sensor 203 and the return water temperature sensor 204 are respectively located on the water supply and return main pipes to measure the supply and return water temperature difference. The frequency converter 106, the bypass regulating valve 104, the differential pressure sensor 201, the flow meter 202, the water supply temperature sensor 203 and the return water temperature sensor 204 are all connected to the variable flow energy-saving control system 101.

[0019] Furthermore, the variable flow energy-saving control system 101 has two built-in supply and return water pressure difference setting value algorithm models, which are used to correct the pressure difference according to the flow rate and the supply and return water temperature difference. Changes in the circulating water flow rate or temperature difference can lead to changes in the resistance coefficient, thereby changing the flow setting value. By tracking the measured flow rate and temperature difference changes to adjust the supply and return water pressure difference setting value in real time, energy saving and comfort can be taken into account during system operation.

[0020] Furthermore, the variable flow energy-saving control system 101 receives the temperature difference signals from the flow and temperature sensors and then inputs the built-in algorithm model to correct the resistance coefficient to obtain the supply and return water pressure difference set value, and then compares the PID to adjust the flow of the circulating water pump 105 or the valve opening of the bypass regulating valve 104 based on the supply and return water pressure difference set value and the actual supply and return water pressure difference measured by the pressure difference sensor 201.

[0021] See also Figure 2 In order to better understand the embodiments of the present invention, the working of the embodiments of the present invention is described exemplarily below.

[0022] Exemplarily, in this embodiment, when the circulating water flow rate changes, the variable flow energy-saving control system 101 receives the flow change signal and adjusts the pressure difference setting value according to the built-in flow correction pressure difference algorithm model. The correction algorithm model of the pressure difference setting value is:

[0023] , when the flow Q changes, It changes accordingly, thereby changing the resistance coefficient. When the measured pressure difference ΔP>0.2ΔPd, the pressure difference setting value ΔPset is first adjusted by the measured flow change according to the algorithm model of the flow-corrected pressure difference, and it is compared with the measured ΔP, and then the frequency of the circulating water pump is changed, and the PID adjusts the water pump flow. When the measured value of the supply and return water pressure difference is less than the set value, the variable flow energy-saving control system 101 PID controls the frequency converter 106 to increase the operating frequency of the circulating water pump 105, thereby increasing the circulating water flow. When the measured value of the supply and return water pressure difference is greater than the set value, the variable flow energy-saving control system 101 PID controls the frequency converter 106 to reduce the operating frequency of the circulating water pump 105, thereby reducing the circulating water flow. The measured value of the supply and return water pressure difference is maintained consistent with the set value through the variable frequency adjustment of the circulating water pump 105, avoiding energy waste caused by mismatch between system supply and demand; when the measured pressure difference ΔP≤0.2ΔPd, the water pump frequency is first increased to increase the pressure difference of the supply and return pipes to 0.2ΔPd to ensure minimum pressure difference control. When the frequency is adjusted to the maximum and still does not meet the minimum pressure difference, the bypass regulating valve 104 is opened to increase the valve opening so that the pressure difference meets ΔP=0.2ΔPd. hour, Follow The increase is exponential, The minimum value is 0.2. The pressure difference setting value and the measured value change in real time with the flow rate, and the response is sensitive. hour, The set value is 0.2, and the system ensures the minimum pressure difference control operation. The system saves energy and ensures the comfort of the terminal equipment.

[0024] For example, in this embodiment, when the temperature difference between the circulating water supply and return water changes, the variable flow energy-saving control system 101 receives the temperature difference change signal and adjusts the pressure difference setting value according to the built-in temperature difference correction pressure difference algorithm model. The correction algorithm model of the pressure difference setting value is: , when the temperature difference T changes, The pressure difference is changed accordingly, thereby changing the resistance coefficient. The algorithm model for correcting the pressure difference according to the temperature difference adjusts the pressure difference set value ΔPset according to the measured temperature difference change, and compares it with the measured ΔP, and then PID adjusts the water pump flow. The adjustment method for correcting the pressure difference according to the temperature difference is the same as the adjustment method for correcting the pressure difference according to the flow.

[0025] The beneficial effects of the embodiments provided by the utility model are as follows: the resistance coefficient and the pressure difference setting value are dynamically adjusted according to the flow rate and temperature difference changes during the operation process, and the system pressure difference is optimized in real time to ensure that the supply and demand of the system operation are consistent and energy consumption is reduced; the circulating water flow rate is controlled by variable flow regulation, which is sensitive and eliminates the adverse effects of the lag of conventional temperature difference regulation; and both user comfort and system energy saving are taken into account.

[0026] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A circulating water variable flow energy-saving system based on resistance coefficient optimization, characterized in that: include: Variable flow energy-saving control system, cold and heat source equipment, terminal equipment, bypass regulating valve, circulating water pump and its connected frequency converter, differential pressure sensor, flow meter, water supply temperature sensor and return water temperature sensor, including: The terminal equipment includes one or a plurality of devices arranged in parallel, the bypass regulating valve is located on the water supply and return main pipe, and the circulating water flow rate is changed by adjusting the valve opening, the circulating water pump is located on the water supply main pipe and is frequency-controlled by a frequency converter, the differential pressure sensor is connected to the supply and return pipes to measure the pressure difference between the supply and return pipes, the flow meter is located on the water supply main pipe to measure the circulating water flow rate, the supply water temperature sensor and the return water temperature sensor are respectively located on the supply and return water main pipes to measure the supply and return water temperature difference; the frequency converter, bypass regulating valve, differential pressure sensor, flow meter, supply water temperature sensor and return water temperature sensor are all connected to the variable flow energy-saving control system.

2. The circulating water variable flow rate energy-saving system according to claim 1, characterized in that: The variable flow energy-saving control system has two built-in supply and return water pressure difference setting value algorithm models, which are used to correct the pressure difference according to the flow rate and the supply and return water temperature difference. Changes in the circulating water flow rate or temperature difference can cause changes in the resistance coefficient and change the flow setting value.

3. The circulating water variable flow rate energy-saving system according to claim 2, characterized in that: The variable flow energy-saving control system is used to receive the temperature difference signals of the flow and temperature sensors and then input the built-in algorithm model to correct the resistance coefficient to obtain the supply and return water pressure difference set value. The PID is used to adjust the flow of the circulating water pump or the valve opening of the bypass regulating valve according to the comparison between the supply and return water pressure difference set value and the actual supply and return water pressure difference value collected by the pressure difference sensor.

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