1.1 Hydraulic imbalance under design conditions An excellent HVAC system can fully guarantee that the equipment can obtain the required amount of water under full load conditions, and at the same time fully guarantee the safety of the system operation. And the economic benefits, effectively reducing the customer's water complaints and water waste, etc., only such a system can be regarded as a hydraulic balance system. If the system does not have these features, then this type of system can be called an unbalanced system. Under normal circumstances, if some users in the hydraulic system use the indenter larger than the designed indenter, then the actual water flow of the user will exceed the designed flow, which will affect the actual flow of other loops. We claim that the hydraulic imbalance generated under such conditions is a static hydraulic imbalance. The static hydraulic imbalance is usually caused by system design or construction. The static hydraulic imbalance is unavoidable by the system itself.
There is also a state in which the actual traffic of all user terminals in the system is greater than or equal to the value of the system design. In this case, the traffic can fully satisfy the customer's needs, so this state generally does not cause customer complaints, so this situation will not cause the designer's attention. In general, we use the formula ΔP=SG2 to describe the relationship between the physical factors of the hydraulic conditions in the closed loop network state (Δp is the differential pressure, S is the network impedance, and G is the flow).
In the domestic concept of static hydraulic balance valve has not been introduced, usually the use of shut-off valves or butterfly valves to control the static hydraulic system. These valves are widely used in China because of their simple structure, easy operation and economical benefits.
On the basis of clear design selection, the designer should open all temperature-controlled electric valves at the end under full load conditions, and design the end flow of No.1 to No.3 to 33m3/h. The valve has maintained a 100% opening. At this time, the actual flow at the end of No. 1 is 39m3/h; the second is 35m3/h; the third is 31m3/h. At this time, the pump operating point parameter head is about 19m. The flow rate is about 105m3/h, so the system has a hydraulic imbalance.
The system can be adjusted by adjusting the opening degree of the No. 1 and No. 2 valves. The specific operation is: reduce the differential pressure of the No. 1 temperature control valve by 40 kPa; the pressure difference of the No. 2 is reduced by 20 kPa to ensure the coils of the three end nodes. The resistance at both ends of the temperature control valve is maintained at 80 kPa, and at the same time it can meet the designed flow rate of 33 m3 / h, the pump head is 20 m, the flow rate reaches 100 m3 / h, thus achieving the static balance of the system. Therefore, we do not need to adjust all the throttle valves to achieve the static hydraulic balance of the system, so we do not need to configure one by one when configuring the static hydraulic balance valve for the end branch, that is to say static hydraulic balance. Valves are not the only way to deal with such problems.
In the current situation, the design of most HVAC hydraulic systems is only for the design of the end branch road design flow, basically does not pay attention to the relevant standards and requirements of the end pressure difference, in the specific operation process, some need manual To complete the balance adjustment basically depends on the design, construction and experience of the operation and maintenance personnel, which is a system adjustment method without theoretical support. However, from the practical point of view, this adjustment method without theoretical support does bring certain effects to the hydraulic imbalance of the system.
1.2 Static hydraulic balance valve and hydraulic balance The static hydraulic balance valve is essentially a multifunctional manual control valve. The static balance valve has the characteristics of single valve multi-function. "Based on the data of experimental characteristics, when Δp is constant State, when the static hydraulic balance valve does not have obvious adjustment advantages, so under the current technical conditions, the use of static hydraulic balance valve to directly replace the traditional hydraulic control valve is not mature enough.
In the current static hydraulic balance valve market, the balance valve products have the functions of flow measurement, valve opening screen display, pre-flow, emptying and so on. The static hydraulic balance valve allows the flow to be measured in a timely manner with a specific instrument and also acts as a switch. Once the balancing valve has been commissioned, we will not be able to make a smooth change in the valve opening. This mainly takes into account the later maintenance problems, and we have sealed the valve body spindle. Work such as measurement does not need to be run in the event of an interrupted system, it can be done in the field, and can be achieved without breaking the overall insulation state of the system. However, from the perspective of cost performance, the centrifugal pump with the same price is not superior to the same flow, and there are still some problems in the static hydraulic balance valve in the current domestic market. For incompressible fluids, a static hydraulic balance valve can be used as a localized drag-limiting component.
The static hydraulic balance valve can adjust the flow resistance of the valve by its valve opening degree. Each opening of the valve corresponds to a KV value, and the KV value of different opening degrees is fixed, then we can get the Δp on the spot. Out of its Q value. In order to facilitate the measurement, we usually set a special pressure test hole for the two ports of the static hydraulic balance valve. This part is usually used as a throttling. When we are working on engineering commissioning, we use the relevant hydraulic balance debugging equipment provided by the manufacturer to measure the Δp value, and then use the relevant software to find the corresponding KV value to calculate the specific Q value. At this time, Δp is taken as the specific measured value; KV is taken as the set value, when it satisfies the condition of ΔP=0.1 MPa; Q is the specific calculated value, and the factors affecting the calculation speed mainly include the actual over-current area of ​​the valve and The accuracy of the roughness estimation value, and the like.
What needs to be paid attention to is that we use the balancing valve to deal with the related hydraulic imbalance problem, which requires certain supporting conditions. "Based on the operating mechanism of the static hydraulic balancing valve, we can know that after the static hydraulic balancing valve is locked, the Δp value Fluctuations can cause a constant damage to the amount of water flowing through the valve, resulting in a change in the calibrated flow value.
In the current market, many suppliers of static hydraulic balance valves have explained that their products have a flow preset function, but in actual operation, it is difficult to choose a suitable KVS value, because the current market balance valve The continuous KVS value is not given, and the adjustment value of KVS is not given according to the actual needs. Therefore, when we set the flow rate according to the KVS value provided by the supplier, there will be a certain deviation, which cannot meet the actual adjustment needs. . Since it is impossible to clarify the Δp value of the field and the change of the KV value caused by the adjustment of the valve opening degree, it is found in the specific practice that if the fouling coefficient of the inner wall of the valve cannot be clarified or when the RE value does not exceed 3,000, the flow rate A large calculation deviation may occur for the Q value. Therefore, in the judgment of static hydraulic balance, it is necessary to ensure that all self-operated valves have reached the corresponding design parameter values, ensuring that all the end device temperature control valves are fully open, and that the flow rate can meet the design requirements. .
Regardless of whether the balancing valve has the preset function of the flow rate, after the installation of the water system is completed, all the valves must be adjusted to ensure that the flow Q value of the static water balance valve can meet the design requirements, thereby ensuring that the pipe network can be realized. Water balance under working conditions. At this time, the opening degree of the static water balance valve is locked, and the set opening degree cannot be adjusted smoothly during the running. At the same time, it is necessary to do the corresponding record work, and save the relevant data to the system equipment debugging file to facilitate the future maintenance work.
In addition, because the KV values ​​of the computer software provided by different equipment suppliers are not uniform, the product debugging instruments provided by different suppliers cannot be interoperable. In the static hydraulic balancing valve, all static hydraulic balancing valves are provided with a cavity behind their plugs, which becomes the main retention point for dirt during on-line operation.
2 self-operated flow control valve 2.1 working principle of self-operated flow control valve Self-operated flow control valve is a new type of regulating valve currently on the market. Self-operated flow control valve is superior to traditional manual flow regulating valve. It is capable of automatic flow regulation without the need for external power. In the actual use process, it is found that the use of the self-operated flow control valve in the closed water circulation system can facilitate the flow distribution and dynamic balance of the system, thereby simplifying the system debugging. Based on these advantages, the self-operated control valve has been favored by many manufacturers in the heating and air conditioning project. The self-operated flow control valve is a two-valve combination structure consisting of a manual regulating valve and an automatic balancing valve, which are responsible for setting the flow rate and maintaining the flow constant operation.
In the manual regulating valve, KVS is the flow coefficient of the valve port of the manual regulating valve, and P2-P3 is the pressure difference coefficient of the valve port of the manual regulating valve. The size of KVS is closely related to the opening degree, the opening is unchanged, and KVS is a variable. If P2-P3 is unchanged, C does not change. P2-P3 remains unchanged mainly depending on the balancing valve. For example, if the pressure difference Pl-P3 of the inlet and outlet becomes larger, the force of the dynamic pressure film and the spring is used to make the balance switch automatically adjust, and the P1-P2 will become larger, keeping the P2-P3 unchanged, thus forming a fixed; P3 becomes smaller, the balance switch is automatically turned up, P1-P2 will become smaller, and P2-P3 will remain unchanged, thus completing the fixed "manual switch adjustment group. Each valve opens at an angle corresponding to the flow rate. The relationship between the angle of opening of each valve and the flow rate is determined by the experimental standard presented by the test bench, and there is also a corresponding opening display and locking device.
2.2 Self-operated flow Zui control valve can be applied in the water mixing system. The self-operated flow control valve does not need external power but relies on the pressure difference of its own medium to realize the control. The self-operated flow control valve is equipped with components that automatically control the flow. This component can achieve flow balance, and this function fundamentally solves the problem of hydraulic imbalance. The installation of the self-operated flow control valve is very simple and easy to adjust. The energy consumed during use is less, and the increased heating area can reach between 25% and 30%, which greatly improves the stability of its operation and ensures heating. the quality of. When we carry out the transformation of the water mixing system, we first calculate the hydraulic power, and after analyzing the heating area, the ring flow rate, and the corresponding heating pipe diameter, etc., according to the data information, select the appropriate flow control valve, according to the temperature. By adjusting the flow rate, the unique function of the self-operated flow control valve is used to achieve stable pressure, flow and temperature, thus ensuring a relatively stable flow between the mixing stations and ensuring the balance of the system. run. -Sanjing Valve Technology Department provides
There is also a state in which the actual traffic of all user terminals in the system is greater than or equal to the value of the system design. In this case, the traffic can fully satisfy the customer's needs, so this state generally does not cause customer complaints, so this situation will not cause the designer's attention. In general, we use the formula ΔP=SG2 to describe the relationship between the physical factors of the hydraulic conditions in the closed loop network state (Δp is the differential pressure, S is the network impedance, and G is the flow).
In the domestic concept of static hydraulic balance valve has not been introduced, usually the use of shut-off valves or butterfly valves to control the static hydraulic system. These valves are widely used in China because of their simple structure, easy operation and economical benefits.
On the basis of clear design selection, the designer should open all temperature-controlled electric valves at the end under full load conditions, and design the end flow of No.1 to No.3 to 33m3/h. The valve has maintained a 100% opening. At this time, the actual flow at the end of No. 1 is 39m3/h; the second is 35m3/h; the third is 31m3/h. At this time, the pump operating point parameter head is about 19m. The flow rate is about 105m3/h, so the system has a hydraulic imbalance.
The system can be adjusted by adjusting the opening degree of the No. 1 and No. 2 valves. The specific operation is: reduce the differential pressure of the No. 1 temperature control valve by 40 kPa; the pressure difference of the No. 2 is reduced by 20 kPa to ensure the coils of the three end nodes. The resistance at both ends of the temperature control valve is maintained at 80 kPa, and at the same time it can meet the designed flow rate of 33 m3 / h, the pump head is 20 m, the flow rate reaches 100 m3 / h, thus achieving the static balance of the system. Therefore, we do not need to adjust all the throttle valves to achieve the static hydraulic balance of the system, so we do not need to configure one by one when configuring the static hydraulic balance valve for the end branch, that is to say static hydraulic balance. Valves are not the only way to deal with such problems.
In the current situation, the design of most HVAC hydraulic systems is only for the design of the end branch road design flow, basically does not pay attention to the relevant standards and requirements of the end pressure difference, in the specific operation process, some need manual To complete the balance adjustment basically depends on the design, construction and experience of the operation and maintenance personnel, which is a system adjustment method without theoretical support. However, from the practical point of view, this adjustment method without theoretical support does bring certain effects to the hydraulic imbalance of the system.
1.2 Static hydraulic balance valve and hydraulic balance The static hydraulic balance valve is essentially a multifunctional manual control valve. The static balance valve has the characteristics of single valve multi-function. "Based on the data of experimental characteristics, when Δp is constant State, when the static hydraulic balance valve does not have obvious adjustment advantages, so under the current technical conditions, the use of static hydraulic balance valve to directly replace the traditional hydraulic control valve is not mature enough.
In the current static hydraulic balance valve market, the balance valve products have the functions of flow measurement, valve opening screen display, pre-flow, emptying and so on. The static hydraulic balance valve allows the flow to be measured in a timely manner with a specific instrument and also acts as a switch. Once the balancing valve has been commissioned, we will not be able to make a smooth change in the valve opening. This mainly takes into account the later maintenance problems, and we have sealed the valve body spindle. Work such as measurement does not need to be run in the event of an interrupted system, it can be done in the field, and can be achieved without breaking the overall insulation state of the system. However, from the perspective of cost performance, the centrifugal pump with the same price is not superior to the same flow, and there are still some problems in the static hydraulic balance valve in the current domestic market. For incompressible fluids, a static hydraulic balance valve can be used as a localized drag-limiting component.
The static hydraulic balance valve can adjust the flow resistance of the valve by its valve opening degree. Each opening of the valve corresponds to a KV value, and the KV value of different opening degrees is fixed, then we can get the Δp on the spot. Out of its Q value. In order to facilitate the measurement, we usually set a special pressure test hole for the two ports of the static hydraulic balance valve. This part is usually used as a throttling. When we are working on engineering commissioning, we use the relevant hydraulic balance debugging equipment provided by the manufacturer to measure the Δp value, and then use the relevant software to find the corresponding KV value to calculate the specific Q value. At this time, Δp is taken as the specific measured value; KV is taken as the set value, when it satisfies the condition of ΔP=0.1 MPa; Q is the specific calculated value, and the factors affecting the calculation speed mainly include the actual over-current area of ​​the valve and The accuracy of the roughness estimation value, and the like.
What needs to be paid attention to is that we use the balancing valve to deal with the related hydraulic imbalance problem, which requires certain supporting conditions. "Based on the operating mechanism of the static hydraulic balancing valve, we can know that after the static hydraulic balancing valve is locked, the Δp value Fluctuations can cause a constant damage to the amount of water flowing through the valve, resulting in a change in the calibrated flow value.
In the current market, many suppliers of static hydraulic balance valves have explained that their products have a flow preset function, but in actual operation, it is difficult to choose a suitable KVS value, because the current market balance valve The continuous KVS value is not given, and the adjustment value of KVS is not given according to the actual needs. Therefore, when we set the flow rate according to the KVS value provided by the supplier, there will be a certain deviation, which cannot meet the actual adjustment needs. . Since it is impossible to clarify the Δp value of the field and the change of the KV value caused by the adjustment of the valve opening degree, it is found in the specific practice that if the fouling coefficient of the inner wall of the valve cannot be clarified or when the RE value does not exceed 3,000, the flow rate A large calculation deviation may occur for the Q value. Therefore, in the judgment of static hydraulic balance, it is necessary to ensure that all self-operated valves have reached the corresponding design parameter values, ensuring that all the end device temperature control valves are fully open, and that the flow rate can meet the design requirements. .
Regardless of whether the balancing valve has the preset function of the flow rate, after the installation of the water system is completed, all the valves must be adjusted to ensure that the flow Q value of the static water balance valve can meet the design requirements, thereby ensuring that the pipe network can be realized. Water balance under working conditions. At this time, the opening degree of the static water balance valve is locked, and the set opening degree cannot be adjusted smoothly during the running. At the same time, it is necessary to do the corresponding record work, and save the relevant data to the system equipment debugging file to facilitate the future maintenance work.
In addition, because the KV values ​​of the computer software provided by different equipment suppliers are not uniform, the product debugging instruments provided by different suppliers cannot be interoperable. In the static hydraulic balancing valve, all static hydraulic balancing valves are provided with a cavity behind their plugs, which becomes the main retention point for dirt during on-line operation.
2 self-operated flow control valve 2.1 working principle of self-operated flow control valve Self-operated flow control valve is a new type of regulating valve currently on the market. Self-operated flow control valve is superior to traditional manual flow regulating valve. It is capable of automatic flow regulation without the need for external power. In the actual use process, it is found that the use of the self-operated flow control valve in the closed water circulation system can facilitate the flow distribution and dynamic balance of the system, thereby simplifying the system debugging. Based on these advantages, the self-operated control valve has been favored by many manufacturers in the heating and air conditioning project. The self-operated flow control valve is a two-valve combination structure consisting of a manual regulating valve and an automatic balancing valve, which are responsible for setting the flow rate and maintaining the flow constant operation.
In the manual regulating valve, KVS is the flow coefficient of the valve port of the manual regulating valve, and P2-P3 is the pressure difference coefficient of the valve port of the manual regulating valve. The size of KVS is closely related to the opening degree, the opening is unchanged, and KVS is a variable. If P2-P3 is unchanged, C does not change. P2-P3 remains unchanged mainly depending on the balancing valve. For example, if the pressure difference Pl-P3 of the inlet and outlet becomes larger, the force of the dynamic pressure film and the spring is used to make the balance switch automatically adjust, and the P1-P2 will become larger, keeping the P2-P3 unchanged, thus forming a fixed; P3 becomes smaller, the balance switch is automatically turned up, P1-P2 will become smaller, and P2-P3 will remain unchanged, thus completing the fixed "manual switch adjustment group. Each valve opens at an angle corresponding to the flow rate. The relationship between the angle of opening of each valve and the flow rate is determined by the experimental standard presented by the test bench, and there is also a corresponding opening display and locking device.
2.2 Self-operated flow Zui control valve can be applied in the water mixing system. The self-operated flow control valve does not need external power but relies on the pressure difference of its own medium to realize the control. The self-operated flow control valve is equipped with components that automatically control the flow. This component can achieve flow balance, and this function fundamentally solves the problem of hydraulic imbalance. The installation of the self-operated flow control valve is very simple and easy to adjust. The energy consumed during use is less, and the increased heating area can reach between 25% and 30%, which greatly improves the stability of its operation and ensures heating. the quality of. When we carry out the transformation of the water mixing system, we first calculate the hydraulic power, and after analyzing the heating area, the ring flow rate, and the corresponding heating pipe diameter, etc., according to the data information, select the appropriate flow control valve, according to the temperature. By adjusting the flow rate, the unique function of the self-operated flow control valve is used to achieve stable pressure, flow and temperature, thus ensuring a relatively stable flow between the mixing stations and ensuring the balance of the system. run. -Sanjing Valve Technology Department provides
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