Model selection and control method of regional cooling large-diameter electric control valve

Abstract

The invention discloses a model selection and control method for a regional cooling large-diameter electric control valve. The method comprises the following steps that a first database and a second database are established; calculating the pressure difference of the water flow before and after the regulating valve of which the model needs to be selected at the maximum flow and the minimum flow; calculating the flow coefficient of the regulating valve; performing data correction on the first maximum flow coefficient to obtain a second maximum flow coefficient; matching the second maximum flow coefficient with the minimum flow coefficient in a first database, outputting a result when a first condition is met, matching the second maximum flow coefficient with the minimum flow coefficient in a second database when the first condition is not met, and outputting a result when a second condition is met. When the second condition is not met, matching is conducted again in the second database, two second valve models are selected from the second database, and when the two second valve models meet the third condition at the same time, a result is output. Compared with the prior art, the model selection difficulty of the regulating valve of the regional cooling system is reduced.

Description

Technical Field

[0001] The present invention relates to the field of mechanical engineering, and particularly to a method for selecting and controlling a large-diameter electric control valve for district cooling. Background Art

[0002] With the rise of district cooling in China, the scale of the air-conditioning cold source system is getting larger and larger, and correspondingly, the diameter of the cooling pipes is also increasing. For the cold stations of district cooling, the size of the cooling pipes generally reaches DN800 (where DN is the diameter, with the unit of millimeter, mm) and above. The increase in the pipe size poses higher requirements for the control valves that need to be adjusted and controlled. In the past, in the HVAC water system, electric control valves were generally applied to the air-conditioning terminals, such as fan coils, air handling units, packaged air handling units, fresh air handling units, etc., and their diameters were generally within DN150, and only a few manufacturers could achieve DN250. The conventional electric control valves with a maximum DN250 diameter can no longer meet the requirements of the flow regulation of large pipes in district cooling, and there will be a series of problems such as construction and installation when the valve diameter and the pipe diameter differ greatly, and it also does not meet the requirement in the relevant specification (Specification for Selection and Design of Automation Instruments: HG / T20507-2014) that the selected diameter of the control valve should not be less than half of the diameter of the pipe where it is located. Therefore, how to select the type of large-diameter electric control valve and how to achieve effective regulation have become a difficult problem in district cooling design. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for selecting and controlling a large-diameter electric control valve for district cooling, and the technical problem to be solved is to reduce the difficulty of type selection.

[0004] To solve the above problems, the present invention is implemented by adopting the following technical solutions: A method for selecting and controlling a large-diameter electric control valve for district cooling includes the following steps:

[0005] Step S1: Establish a first database and a second database. The first database is a conventional control valve database;

[0006] Each piece of conventional control valve data includes a first valve model, the corresponding first valve diameter DN value of the first valve model, the first valve opening angle value, the first flow coefficient value, and the manufacturer;

[0007] The second database is a butterfly valve database. Each piece of butterfly valve data includes a second valve model, the corresponding second valve diameter DN value of the second valve model, the second valve opening angle value, and the second flow coefficient value;

[0008] Step S2: According to the pump head of the district cooling cold water pipeline system design, calculate the pressure difference between the water flows before and after the control valve to be selected at the maximum flow and the minimum flow.

[0009] Step S3: Calculate the flow coefficient of the regulating valve, where the flow coefficient includes the first maximum flow coefficient and the minimum flow coefficient;

[0010] Step S4: Perform data correction on the calculated first maximum flow coefficient to obtain the second maximum flow coefficient;

[0011] Step S5: Match the second maximum flow coefficient and the minimum flow coefficient in the first database. When the first condition is met, output the result. When the first condition is not met, execute Step S6;

[0012] Step S6: Match the second maximum flow coefficient and the minimum flow coefficient in the second database. When the second condition is met, output the result. When the second condition is not met, execute Step S7;

[0013] Step S7: Perform another match in the second database. Select two second valve models in the second database. When both second valve models meet the third condition, output the result;

[0014] The third condition is to find in the second database a second valve model A whose flow coefficient at an opening of 70° is greater than the second maximum flow coefficient, and a second valve model B whose flow coefficient at an opening of 70° is greater than the flow coefficient of the second valve model A at an opening of 40°, and at the same time, the flow coefficient of the second valve model B at 30° is less than the minimum flow coefficient.

[0015] Further, the first maximum flow coefficient is the flow under the peak cooling load condition, and the minimum flow coefficient is the flow at 25% of the peak cooling load condition.

[0016] Further, the data correction includes amplifying and rounding up the first maximum flow coefficient. The amplification factor is 1.1 - 1.15, and then rounding up the amplified flow coefficient upward to obtain the second maximum flow coefficient.

[0017] Further, the amplification factor for amplification is 1.1 - 1.15, and then rounding up is upward rounding.

[0018] Further, the first condition is that the flow coefficient at an opening of 90° in the first database is greater than the second maximum flow coefficient, the flow coefficient at an opening of 10° is less than the minimum flow coefficient, and the valve diameter is greater than 1 / 2 of the diameter of the pipeline where it is located.

[0019] Further, the second condition is that the flow coefficient at an opening of 70° in the second database is greater than the second maximum flow coefficient, and the flow coefficient at an opening of 30° is less than the minimum flow coefficient.

[0020] Further, in step S5, when there are multiple second valve models that meet the second condition, further judgment is made. Among all the second valve data that meet the second condition, the second valve model with a second valve diameter DN value greater than half of the diameter of the pipeline where it is located and the smallest second valve diameter DN value is selected as the result for output.

[0021] Further, in step S7, when there are multiple second valve models that meet the requirements of the second valve model A, among all the second valve models that meet the conditions, the second valve model with a second valve diameter DN value greater than half of the diameter of the pipeline where it is located and the smallest second valve diameter DN value is used as the second valve model A; when there are multiple second valve signals that meet the requirements of the second valve model B, among all the second valve models that meet the conditions, the second valve model with a second valve diameter DN value greater than half of the diameter of the second valve model A and the smallest second valve diameter DN value is used as the second valve model B.

[0022] Further, in step S7, after the result is output, the selected butterfly valves are connected in parallel according to the output result and the two butterfly valves are controlled. The control includes: when the flow coefficient through the valve is greater than the flow coefficient CmidA at the 40° opening of the second valve model A, the second valve model A is used; when the flow coefficient through the valve is greater than the flow coefficient CmidA at the 40° opening of the second valve model A, the second valve model B is used.

[0023] Compared with the prior art, the present invention automatically matches valves in the database according to the maximum flow coefficient, the minimum flow coefficient, and the valve diameter and outputs the result, which not only reduces the selection difficulty and control problems of the regulating valves in the district cooling system (system), but also realizes the adjustability of the system under different working conditions, ensuring the safety and efficiency of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a flowchart of the present invention.

[0025] Figure 2 is a flow characteristic curve diagram of two butterfly valves with different diameters.

[0026] Figure 3 is a flow characteristic curve diagram after two butterfly valves with different diameters are connected in parallel. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The present invention will be further described in detail below with reference to the drawings and embodiments.

[0028] As Figure 1 shown, the present invention discloses a method for selecting and controlling a large-diameter electric regulating valve for district cooling, including the following steps:

[0029] Step S1: Establish the first database and the second database, specifically including: The first database is a conventional regulating valve database. Each piece of conventional regulating valve data includes the first valve model, the corresponding first valve diameter DN value of the first valve model, the first valve opening angle value, the first flow coefficient value, and the manufacturer. The data in the first database is obtained after being provided and input by each valve manufacturer.

[0030] The second database is a butterfly valve database. Each piece of butterfly valve data includes the second valve model, the corresponding second valve diameter DN value of the second valve model, the second valve opening angle value, and the second flow coefficient value. The second valve opening angle value includes the openable angle range value of the butterfly valve (for example: between 30° - 70°) and the corresponding second flow coefficient value for this angle range value, and the manufacturer. The data in the second database is obtained after being provided and input by each butterfly valve manufacturer.

[0031] Step S2: According to the pump head of the regional cooling water pipeline system design, calculate the pressure difference ΔP of the water flow before and after the regulating valve when selecting the regulating valve at the maximum flow rate and the minimum flow rate (referring to the pressure difference between before and after the water passes through the regulating valve). max and ΔP min , ΔP max is the pressure difference before and after the regulating valve at the maximum flow rate, and ΔP min is the pressure difference before and after the regulating valve at the minimum flow rate. The pressure difference before and after the regulating valve is the total pressure difference of the pipeline where the regulating valve is located minus the pressure differences of other valve parts and the pipeline except this regulating valve. It is specifically calculated using the following formula:

[0032] ΔP = SQ 2

[0033] where S is the comprehensive coefficient resistance of the pipeline system, which can be obtained according to the pipeline designed in the system; Q is the flow rate passing through the pipeline system.

[0034] Step S3: Calculate the flow coefficient of the regulating valve, which represents the volume of fluid passing through per unit time under specific conditions. The flow coefficient includes the first maximum flow coefficient Cmax and the minimum flow coefficient Cmin. The maximum flow rate is the flow rate under the cooling peak load condition, and the minimum flow rate is 25% of the cooling peak load condition. The flow coefficient is calculated using the following formula:

[0035]

[0036] where Q is the flow rate passing through the regulating valve, with the unit of m 3 / h; Δp is the pressure difference before and after the regulating valve, with the unit of kPa; C is the flow coefficient, indicating that the density of water is 1 g / cm 3, when the pressure difference across the control valve is 100 kPa, the number of cubic meters of water flowing through the control valve per hour.

[0037] Step S4: Perform data correction on the calculated first maximum flow coefficient Cmax. The correction includes: amplifying the first maximum flow coefficient Cmax by a factor of 1.1 - 1.15 (preferably 1.1), and then rounding up the amplified flow coefficient to obtain the second maximum flow coefficient Cmax1.

[0038] Step S5: Match the second maximum flow coefficient Cmax1 and the minimum flow coefficient Cmin in the first database. When the first condition is met, output the result, which includes the matched conventional valve data, including the first valve model, the first valve diameter DN value, the first valve opening angle value, the first flow coefficient value, and the manufacturer.

[0039] The first condition is that the flow coefficient at 90° opening (i.e., when the valve is fully open) in the first database is greater than the second maximum flow coefficient Cmax1, and the flow coefficient at 10° opening is less than the minimum flow coefficient Cmin, and the valve diameter is greater than half of the diameter of the pipeline where it is located.

[0040] When the first condition is not met, then execute Step S6. Match the second maximum flow coefficient Cmax1 and the minimum flow coefficient Cmin in the second database. When the second condition is met, output the result, which includes the matched butterfly valve data, including the second valve model, the second valve diameter DN value, the second valve opening angle value, the second flow coefficient value, and the manufacturer.

[0041] Since the selection of a large - diameter butterfly valve requires ensuring that the adjustment range of the butterfly valve is between 30° and 70°, the second condition is that the flow coefficient at 70° opening in the second database is greater than the second maximum flow coefficient Cmax1, and the flow coefficient at 30° opening is less than the minimum flow coefficient Cmin. At this time, a single butterfly valve is selected as the control valve. When there are multiple second valve models that meet the second condition, further judgment is made. Among all the second valve data that meet the second condition, select the second valve model with a second valve diameter DN value greater than half of the diameter of the pipeline where it is located and the smallest second valve diameter DN value as the result for output.

[0042] In actual process cases, since the district cooling system needs to adjust the flow rate under different loads and the range of its flow rate variation is large, the following problems may occur when selecting a butterfly valve: The butterfly valve of the second valve model selected according to the second maximum flow coefficient Cmax1 cannot meet the adjustment requirements of the district cooling system under the minimum flow coefficient, that is, the minimum flow coefficient Cmin is less than the flow coefficient of the butterfly valve of the second valve model at 30° opening, or the minimum flow coefficient Cmin is greater than the flow coefficient of the butterfly valve of the second valve model at 30° opening, but does not exceed 1%-5% of the flow coefficient of the butterfly valve of the second valve model at 30° opening, resulting in the valve working at a small opening for a long time under low load conditions. Although the number of days of low load conditions is not long for the entire cooling period, such a practice will reduce the service life of the valve and increase the cost of later maintenance, so it should also be avoided as much as possible.

[0043] When the second condition is not met, step S7 is executed to perform another match in the second database, and two second valve models are selected. When the two selected second valve models simultaneously meet the third condition, the result is output. The result includes the matched butterfly valve data, including the second valve model, the second valve diameter DN value, the second valve opening angle value, the second flow coefficient value, and the manufacturer.

[0044] The third condition is to find in the second database a second valve model A whose flow coefficient at 70° opening is greater than the second maximum flow coefficient Cmax1, and a second valve model B whose flow coefficient at 70° opening is greater than the flow coefficient CmidA of the second valve model A at 40° opening, and at the same time, the flow coefficient of the second valve model B at 30° is less than the minimum flow coefficient Cmin.

[0045] When there are multiple second valve models that meet the requirements of the second valve model A, select the second valve model with the second valve diameter DN value greater than 1 / 2 of the pipeline diameter and the smallest second valve diameter DN value among all the second valve models that meet the conditions as the second valve model A; when there are multiple second valve signals that meet the requirements of the second valve model B, select the second valve model with the second valve diameter DN value greater than 1 / 2 of the diameter of the second valve model A and the smallest second valve diameter DN value among all the second valve models that meet the conditions as the second valve model B.

[0046] In the present invention, the flow coefficient of the second valve model A is greater than the flow coefficient of the second valve model B.

[0047] After the output result, the selected butterfly valves are connected in parallel according to the output result and the two butterfly valves are controlled. The control includes: when the flow coefficient through the valve is greater than the flow coefficient CmidA at the 40° opening of the second valve model A, use the second valve model A; when the flow coefficient through the valve is greater than the flow coefficient CmidA at the 40° opening of the second valve model A, use the second valve model B.

[0048] Since the adjustable ratio of the butterfly valve is too small to meet the usage requirements, the adjustable ratio can be enlarged by connecting valves in parallel.

[0049] The adjustable ratio is divided into ideal adjustable ratio and actual adjustable ratio.

[0050] The ideal adjustable ratio refers to the ratio of the maximum flow rate to the minimum flow rate that can be controlled under the condition of constant valve pressure drop. The controllable minimum flow rate is usually 2%-4% of the maximum flow rate, that is, the adjustable ratio is between 25 and 50. From the perspective of use, the larger the adjustable ratio of the valve, the wider its adjustment range. However, due to the limitations of the spool structure design and processing, the adjustable ratio cannot be made very large. The ideal adjustable ratio of domestic regulating valves is generally 30. In actual operation, the pressure drop of the regulating valve changes with the change of the hydraulic conditions of the system pipeline network. At this time, the ratio of the maximum flow rate to the minimum flow rate actually controlled by it is called the actual adjustable ratio. At this time, since the valve is connected in series with pipelines, valve parts, heat exchangers, etc. in the pipeline system, its actual adjustable ratio is less than the ideal adjustable ratio.

[0051] Taking the example of two butterfly valves connected in parallel, the maximum and minimum flow rates that butterfly valve A can control are Q A100 and Q A0 , and the maximum and minimum flow rates that butterfly valve B can control are Q B100 and Q B0 . Then the ideal adjustable ratio after the two valves are connected in parallel is:

[0052] R = (Q A100 + Q B100 ) / Q AB0

[0053] where Q AB0 is the smaller value of Q A0 and Q B0

[0054] If butterfly valves A and B have the same diameter, the ideal adjustable ratio after parallel connection will double. Thus, it can be seen that connecting valves in parallel can greatly improve the adjustable ratio and meet the usage requirements of a wider adjustable range.

[0055] As an example, as Figure 2 shows the relationship between the opening angle and the flow coefficient of a large-diameter butterfly valve and a small-diameter butterfly valve. If these two butterfly valves are connected in parallel, asFigure 3 Flow curve. Through parallel connection, the opening angles of both butterfly valves are between 30° and 70°. At the same time, there is an overlapping range between the flow coefficient of the large-diameter butterfly valve at a small opening and the flow coefficient of the small-diameter butterfly valve at a large opening, so that the two butterfly valves can have a smooth transition at the connection.

[0056] The present invention automatically selects the large-diameter regulating valve for the district cooling system according to the system design, making the valve selection more accurate and capable of meeting the flow regulation requirements under different working conditions; when the calculated valve diameter is large and the conventional regulating valve cannot meet the requirements, a butterfly valve is selected to be used as the large-diameter regulating valve for the district cooling system. When the adjustable range of a single butterfly valve does not meet the usage requirements, two butterfly valves are selected to be connected in parallel to expand the adjustable ratio to meet the usage requirements. It effectively realizes the adjustability of the system under different working conditions and ensures the safety and high efficiency of the system.

Claims

1. A method for selecting and controlling a large-caliber electric regulating valve for district cooling, characterized by: The steps include: Step S1: establishing a first database and a second database, wherein the first database is a conventional regulating valve database; Each conventional regulating valve data includes the first valve model, the first valve diameter DN value corresponding to the first valve model, the first valve opening angle value, the first flow coefficient value, and the manufacturer; The second database is a butterfly valve database, and each butterfly valve data includes a second valve model, a second valve diameter DN value corresponding to the second valve model, a second valve opening angle value, and a second flow coefficient value; Step S2: Calculate the pressure difference of the water flow before and after the regulating valve at the maximum flow rate and the minimum flow rate of the regulating valve to be selected based on the designed water pump head of the district cooling water piping system; Step S3, calculating the flow coefficient of the regulating valve, where the flow coefficient includes a first maximum flow coefficient and a minimum flow coefficient; Step S4: performing data correction on the calculated first maximum flow coefficient to obtain a second maximum flow coefficient; Step S5, matching the second maximum flow coefficient and the minimum flow coefficient in the first database, and outputting the result when the first condition is met, and executing step S6 when the first condition is not met; Step S6, matching the second maximum flow coefficient and the minimum flow coefficient in the second database, and outputting the result when the second condition is met, and executing step S7 when the second condition is not met; Step S7, performing another match in the second database, selecting two second valve models from the second database, and outputting a result when the two second valve models simultaneously meet the third condition; The third condition is to search the second database for a second valve model A that satisfies a flow coefficient greater than the second maximum flow coefficient at a 70° opening, and a second valve model B that satisfies a flow coefficient greater than the flow coefficient of the second valve model A at a 40° opening, and a flow coefficient less than the minimum flow coefficient at a 30° opening.

2. The method for selecting and controlling a large-diameter electric regulating valve for district cooling according to claim 1 is characterized in that: The first maximum flow coefficient is the flow rate under the cooling peak load condition, and the minimum flow coefficient is the flow rate under 25% of the cooling peak load condition.

3. The method for selecting and controlling a large-diameter electric regulating valve for district cooling according to claim 1 is characterized in that: The data correction includes amplifying and rounding the first maximum flow coefficient to obtain the second maximum flow coefficient.

4. The method for selecting and controlling a large-diameter electric regulating valve for district cooling according to claim 3 is characterized in that: The magnification factor of the magnification is 1.1 to 1.15, and the rounding is performed in an upward direction.

5. The method for selecting and controlling a large-diameter electric regulating valve for district cooling according to claim 1 is characterized in that: The first condition is that the flow coefficient at 90° opening in the first database is greater than the second maximum flow coefficient and the flow coefficient at 10° opening is less than the minimum flow coefficient, and the valve diameter is greater than 1 / 2 of the pipe diameter.

6. The method for selecting and controlling a large-diameter electric regulating valve for district cooling according to claim 1 is characterized in that: The second condition is that the flow coefficient at an opening of 70° in the second database is greater than the second maximum flow coefficient and the flow coefficient at an opening of 30° is less than the minimum flow coefficient.

7. The method for selecting and controlling a large-diameter electric regulating valve for district cooling according to claim 1 or 6, characterized in that: In step S5, when there are multiple second valve models that meet the second condition, further judgment is made, and the second valve model with a second valve diameter DN value greater than 1 / 2 of the pipe diameter and the smallest second valve diameter DN value is selected from all second valve data that meet the second condition and output as the result.

8. The method for selecting and controlling a large-diameter electric regulating valve for district cooling according to claim 1 is characterized in that: In step S7, when there are multiple second valve models that meet the requirements of second valve model A, the second valve model with a second valve caliber DN value greater than 1 / 2 of the pipe caliber and the smallest second valve caliber DN value is selected from all second valve models that meet the conditions as second valve model A; when there are multiple second valve signals that meet the requirements of second valve model B, the second valve model with a second valve caliber DN value greater than 1 / 2 of the second valve model A caliber and the smallest second valve caliber DN value is selected from all second valve models that meet the conditions as second valve model B.

9. The method for selecting and controlling a large-diameter electric regulating valve for district cooling according to claim 1 or 8, characterized in that: In step S7, after the result is output, the selected butterfly valves are connected in parallel and the two butterfly valves are controlled according to the output result. The control includes: when the flow coefficient through the valve is greater than the flow coefficient CmidA of the second valve model A when it is 40° open, the second valve model A is used; when the flow coefficient through the valve is greater than the flow coefficient CmidA of the second valve model A when it is 40° open, the second valve model B is used.

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