Application of Dynamic Flow Balance Valve and Electric Control Valve Combination

Abstract: In this paper, the dynamic balance electric control valve and dynamic flow balance valve and electric control valve combination of dynamic balance function and electric adjustment function were analyzed and compared, and finally pointed out that dynamic flow balance valve and electric control valve combination can not replace the dynamic balance of electric adjustment valve. Keywords: Dynamic Balance Electric Regulator Electric Regulator With the continuous improvement of people's living standards and awareness of energy saving, variable-flow systems occupy an increasingly important position in HVAC engineering. At the same time, a new type of hydraulic system-complete balance The hydraulic system is also more and more widely used in HVAC projects. A fully balanced hydraulic system generally regulates the temperature in the target area by dynamically adjusting the flow of the end-effec- tive electric regulating valve (such as an air conditioner box). It dynamically balances the pressure changes in the system so that the flow between two or more end devices The adjustment does not interfere with each other, so this system is highly energy-efficient. At present, in some air-conditioning projects, some designers use the combination of dynamic flow balance valve and electric control valve instead of the dynamic balance electric control valve in order to achieve the same function, claiming that the two configurations have the same function. Then the dynamic flow balance valve and electric control valve combination can replace the dynamic balance of electric control valve what, the following two features of these configurations for some analysis and comparison. First, the dynamic balance of electric control valve performance analysis: Dynamic balance of electric control valve is different from the traditional electric control valve of a new generation of products, dynamic balance and electric regulation of integrated products, it has the following characteristics: 1, with dynamic balance function : Dynamic balance function refers to the end equipment load changes require the electric regulator valve to a certain opening, no matter how the system pressure changes, the valve can dynamically balance the system's resistance, the flow from the system pressure fluctuations And keep constant. Shown in Figure 1, for a group of multiple air-handling machine parallel loop (only two shown in the figure). Each way through the dynamic balance of electric valve to adjust the return air temperature in the target area, which set the temperature of a region 25 ℃, region 2 set the temperature of 27 ℃. Assuming the summer conditions, the first one has been adjusted to the balance, that is, the target zone temperature T1 has stabilized at 25 ℃, then the dynamic balance of the electric valve opening maintained at a certain position to maintain a constant output flow. Zone 2 is still in an unstable state, the measured return air temperature T2 is 24 ℃, lower than the set temperature 27 ℃, then the measured temperature and the set temperature in the temperature controller to compare the output signal will be dynamic balance valve closed So as to reduce the amount of cold water flowing through the air handler 2. At this moment, the cooling capacity will be reduced, so that the measured temperature T2 will increase to be close to the set temperature. At the same time, the pressure difference at two points of the system risers C and D will increase, A loop air balance valve pneumatic valve DV1 at both ends of the two C, B1 two point pressure increases accordingly. However, due to the dynamic balance of the dynamic balancing valve (the function of the constant pressure difference of the dynamic balancing valve core PV1), the pressure difference at the two ends A1 and B1 of the valve does not change, so the air handling machine loop Of the flow remained unchanged, the cooling capacity unchanged, the corresponding area is still in a state of balance (Figure 2 for the dynamic balance of electric control valve dynamic balance curve). It can be seen from the above that the adjustment of the second loop of the air handler does not disturb the first loop of the air handler that has been balanced, so there is no dynamic hydraulic imbalance between the two loops. For a multi-loop system, the adjustment of any one loop will not interfere with the other loops, and any one loop will not be affected by other loop adjustments. The larger the system, the more dynamic balance Obviously, each loop is only affected by the change of regional load, and not affected by system pressure fluctuations, so it is easy to reach and maintain equilibrium. 2, with excellent electric adjustment function: electric adjustment function is the valve according to the target area temperature control signal changes automatically adjust the valve opening, thus changing the water flow, and ultimately the target area of ​​the actual temperature and the set temperature. Evaluation of electric regulation function is good or bad is the flow characteristics of electric control valve. In the air conditioning system, the ideal flow characteristics of the common electric control valve is straight or equal percentage. However, for the general electric control valve, the actual flow characteristic curve deviates from the ideal flow characteristic curve due to the lesser valve authority in actual use. As shown in Fig. 3, the ideal flow characteristic curve of a motorized control valve is a straight line (curve 1), but the actual flow rate curve close to the quick-open type (curve 2) after installation on the system line deteriorates the adjustment characteristics. Dynamic balance of electric control valve due to the unique structure of the valve in the actual use of the project the valve is basically 1, so the actual flow characteristics and the ideal flow characteristics of the same curve (Figure 4), there is no deviation, it has Excellent electric adjustment function. Second, the dynamic flow balance valve and electric control valve combination of performance analysis shown in Figure 5, for a group of multiple air box parallel loop (only draw 2 Road). Each road at the entrance to install a dynamic flow balance valve and electric control valve. Figure 6 shows the characteristics of these two valve combinations. The left side of the dynamic flow balance valve (flow - pressure) curve, the right side of the electric control valve flow characteristics (flow - opening). 1, the electric adjustment function analysis: Assuming the ideal electric flow characteristics of the selected valve flow curve is linear, as mentioned above, the actual installation due to reduced valve power, electric control valve of the actual flow curve will deviate from the ideal The flow characteristic curve, when it is connected in series with the dynamic flow balance valve, further reduces the valve authority of the electrically adjustable valve due to the partial pressure of the dynamic flow balance valve to a greater extent than the ideal flow characteristic curve. As shown on the right side of Fig. 6, curve 1 is the ideal flow characteristic curve of the electric control valve, curve 2 is the actual flow characteristic curve without the dynamic balance valve installed, curve 3 is the actual flow characteristic curve after the dynamic flow balance valve is connected in series, Curve 3 deviates to a greater extent, with poorer conditioning. Therefore, this series system due to the installation of a dynamic balance valve, the electric adjustment characteristics not only did not increase, but worse than the average electric control valve, so it can be said that the series combination weakened the electrically adjustable valve electric adjustment characteristics. 2, whether the dynamic balance function: Check whether the combination valve dynamic balance function must understand the dynamic balance function requirements. For this combination valve, the dynamic balance function refers to the end equipment load changes require the electric regulating valve adjusted to a certain opening, regardless of system pressure changes, the valve can dynamically balance the system's resistance, so that its flow from the system Pressure fluctuations and the impact of constant. As shown in Figure 5, the design flow of both valves in the combination valve is the design flow of the air conditioner box. The system adjusts the flow rate between the 0-Q design according to the change of the end equipment load during the actual operation. Therefore, the actual flow rate of the system is lower than the design flow most of the time. As the system requires that the flow be changed between 0-Q design, the dynamic flow balance valve, as shown in Fig. 6, has its actual operating range in the slanted area of ​​non-operating range (pressure difference is 0-P min) In fact the valve of the dynamic balance valve is always in the fully open position, equivalent to a fixed throttle element. Such as the end equipment load changes require the system actually needs flow Q0, when the electric control valve to accept the temperature control signal to the opening of the valve to 63% of the B point, at the same time, dynamic flow balance valve operating point A, The corresponding pressure difference is P0, the flow is Q0, then the dynamic flow balance valve bile in the fully open position. When the system pressure fluctuation fluctuates within a certain range, the dynamic balance valve is always in the fully open position, and can not play the role of balancing the pressure fluctuation of the system and keeping the output of the electric control valve constant. Therefore, this combination does not have the dynamic balance Features. And can only rely on the regulation of the electric control valve itself to change the opening to adjust the flow when the system pressure changes, but this adjustment is very inert to the large system, it is difficult to achieve good results. When the pressure difference between point A and point C in Figure 5 fluctuates more than the designed differential pressure of the P + dynamic control valve, the dynamic balancing valve enters the actual working area of ​​the differential pressure and the valve starts to act to limit the flow of the pipe Exceed design flow 3, the combination of the current limiting valve effect is what Mody: Combined valve has the role of current limiting, but this limit is limited to the maximum flow does not exceed the design flow, compared with the dynamic balance of dynamic balancing valve Trivial, but this function is to weaken the electric regulating valve electric adjustment function, increase the cost of resistance. In fact, even without dynamic balance valve installed, electric control valve in the system to increase the pressure so that the flow exceeds the design flow will automatically reduce the opening, thus limiting and regulating flow. Therefore, the limiting effect of the combination valve is only a characteristic rather than an advantage. Third, the dynamic balance of electric control valve and the "dynamic flow balance valve + electric control valve," a combination of programs: technical characteristics of the dynamic balance of electric control valve dynamic flow balance valve + electric control valve Remarks Dynamic balance function with a dynamic balance does not have Dynamic balance function Dynamic balance function refers to the end equipment load changes require the electric regulator valve to a certain opening, no matter how the system pressure changes, the valve can dynamically balance the system's resistance, the flow from the system pressure fluctuations Of the impact and maintain a constant whether electric adjustment with electric adjustment function, and because of the internal structure of the valve body, so that the actual valve operating characteristics of the curve and the ideal flow characteristics of the same, there is no deviation, the electric adjustment characteristics are particularly good, far Higher than the average electric control valve due to the dynamic flow balance valve partial pressure of the valve to make this configuration than the average authority of the lower valve, the actual operating characteristic curve deviate from the ideal flow characteristics of a greater extent, so adjust Characteristics of the valve than the average valve worse The actual working characteristic curve is the most important performance that reflects the valve's ability to regulate the signal such as temperature and the accuracy. The bigger the actual working curve deviates from the ideal flow characteristic curve, the worse the regulating characteristic and the lower the regulating accuracy. Product Function Description Dynamic Balance and The function of electric adjustment integration Only electric adjustment function, and the adjustment characteristics have been weakened Because the dynamic flow balance valve in the combination valve has been in non-work area, the valve bile does not move, and its use weakens the electric control valve Adjustment characteristics; and its so-called maximum current limiting function of the electric control valve itself, but also better according to temperature control requirements to automatically limit and regulate the flow, it is generally considered that the function of this combination valve is lower than the general electric control valve combination Valves in the dynamic flow balance valve useful Why dynamic flow balance valve flow is customized according to the design flow, the actual flow in the variable flow water system operation is equal to or less than the design flow, so the dynamic balance of the electric control valve has actually been in the non Work area, equivalent to a fixed throttle can not be adjusted , There is no role Combination valve maximum flow restriction is the advantage One valve has the temperature control signal in accordance with the requirements of any opening position in any limit to regulate and balance the flow of traffic far superior to the maximum flow limit function Electric control valve itself has Better ability to limit and regulate flow based on temperature control requirements, including and superior to the maximum flow limit function Installation Installation is quick and easy Installation is complicated due to the fact that two valves are required Installation Recommended Dynamic Balance Electric Control Valve Recommended Because investment problems do not use one valve, it is recommended to use only "electric control valve" or "static balance valve + electric control valve" instead of "dynamic flow balance valve + electric control valve" dynamic flow balance valve is essentially a 4, Conclusion: In summary, the "dynamic flow balance valve + electric control valve" combination does not have the dynamic balance function, and its electric adjustment function compared to the general electric control valve has also been weakened, therefore "Dynamic flow balance valve + electric control valve" can not replace the dynamic balance of electric Regulating valve. About the author: Wang Xiaosong, male, born in July 1969, bachelor, chief engineer; 100176, No.5 Tongji Middle Road, Beijing Economic and Technological Development Zone; (010); Email: a.com Technical Features Comparison Dynamic Balance Electric control valve Dynamic flow balance valve + electric control valve Remarks Whether with dynamic balance function With dynamic balance function Does not have dynamic balance function Dynamic balance function refers to the end equipment load changes require the electric control valve to a certain degree of opening, How the system pressure changes, the valve can dynamically balance the system's resistance, so that the flow from the pressure fluctuations of the system to maintain a constant whether Electric adjustment function with electric adjustment function, and because of the internal structure of the valve so that the actual valve Of the working characteristic curve and the ideal flow characteristics of the same line, there is no deviation, the electric adjustment characteristics are particularly good, far higher than the general electric valve due to the dynamic flow balance valve partial pressure, so that this configuration valve more general authority The lower the self-control valve, the actual working characteristic curve Deviation from the ideal flow characteristics of a greater extent, so the adjustment characteristics than the average self-control valve worse The actual valve characteristic curve is to reflect the valve temperature and other signal conditioning ability and accuracy of the most important performance deviation from the actual working curve of the ideal flow curve The greater the degree, the worse the adjustment characteristics, the lower the adjustment accuracy Product Function Description Dynamic balance and electric adjustment The integration of the only electric adjustment function, and the adjustment characteristics have been weakened Because the combination valve dynamic flow balance valve is always in Non-work area, the valve bile does not move, and its use weakens the regulation characteristics of the electric control valve; and its so-called maximum-current function electric control valve itself, and is better according to the temperature control requirements of the automatic limit And regulate the flow, it is generally considered that the function of this combination valve is lower than the dynamic flow balance valve in a typical electric control valve combination valve is useful? Because the flow of the dynamic flow balance valve is customized according to the design flow, when the variable flow water system is operating The actual traffic is equal to or less than the design flow, so dynamic balance Actuating control valve is actually in the non-work area, equivalent to a fixed throttle element can not be adjusted, there is no effect Combination of the maximum flow rate limiting valve is the advantage Merged valve has the temperature control signal in accordance with the requirements of any opening position limit , Adjust and balance the flow of the function far superior to the maximum flow limit function The electric control valve itself has better according to the temperature control requirements automatically limit and adjust the flow of the function contains and better than the maximum flow limit function installation is simple and quick installation Actually need to install two valves, so the installation is more complicated. Recommended Dynamic Balance Electric Control Valve If you do not use one valve because of investment problems, it is recommended to use only the "electric control valve" or "static balance valve + electric control valve", and Do not use "dynamic flow balance valve + electric control valve" Dynamic flow balance valve is essentially a constant flow valve