ACTIVAL+TM Flow Measurement and Control Valve

1. Product summary

Nowadays, energy saving for buildings is becoming in-creasingly important and countermeasures against global warming are urgently required. Energy consumption of air-conditioning systems occupies approximately 43% of the total energy used for buildings, and therefore additional en-ergy efficiency is required.

Under these circumstances, ACTIVAL+ has been developed by Azbil to control the flow rate of cold/hot water through air-condition systems with the aim of saving energy. ACTI-VAL+ is a completely motorized two-way valve which has the added functions of measuring flow rate and heat quantity, and feedback flow rate control.
Conventional control valves can only control to a specific valve position based on the input signal provided, not based on the actual flow rate. Because ACTIVAL+ measures the actual flow rate, it provides flow rate control corresponding to the desired flow rate under the any operating conditions. Moreover, it achieves a dramatic reduction in energy wasted on transfer power (fig. 2).

Furthermore, with conventional control, when the flow rate is changed through the air-conditioning coil by pressure fluctuation, in some cases the room temperature does not change as desired. Since ACTIVAL+ is able to control the actual flow rate precisely, it is able to maintain the optimum room temperature.
ACTIVAL+ is designed based on the concept of integrating the function of measuring heat quantity, flow rate, pressure, and temperature into the control valve itself. Therefore, energy management is possible by simply installing ACTIVAL+ in the air-conditioning system.

In China, Korea, and Southeast Asia, for large-capacity air-conditioning systems installed in office buildings, hospitals, and shopping malls, we developed an adaptable ACTI-VAL+ model with 15–150 A diameters for those markets.

Fig. 1. ACTIVAL+ appearance and cross section

Fig. 2. Verification of effectiveness. Comparison was made on days with almost the same pump conveyance and transfer power.

2. Technical features

This product has an added flow rate control function to control the valve based on the flow rate calculated from the flow coefficient CV, determined by the degree of opening and pressure difference before and after the plug.

A) Pressure measurement method
A stable pressure measurement method is required because internal pressure distribution is affected by the valve opening and the configuration of piping attached to the primary side of the valve. Primary side pressure measuring ports (fig. 3) are provided at four locations around the valve inlet to obtain average pressure. Because of the structure, stable pressure can be measured, without pressure fluctuation. Consequently, even if an elbow is installed before the valve, deterioration of the flow measurement accuracy is suppressed to less than 1% rdg.

Fig. 3. Structure of primary pressure measuring section.

B) Opening Compensation of Stem torsion
To improve flow measuring accuracy, accurate measuring of the plug opening by a potentiometer located in the actuator is needed.

Since the rotating torque of a plug in a large 100–150 A diameter unit is high, stem torsion causes an error in the measured angle.

To solve this problem, we devised a mechanism to estimate the amount of stem torsion from the state of the internal pressure. Software calculates the flow rate using the estimated amount of stem torsion, improving flow measurement accuracy.

Fig. 4. Result of compensation verification test (DN 125)

3. Sales Performance

In recent years global warming is worsening on a global scale, meaning that further energy efficiency will be demanded in the global market. Two thousand or more ACTI-VAL+ valves have been shipped and are helping businesses worldwide to save energy. Now that large-bore models have been added to the ACTIVAL+ lineup, further increase in sales volume is expected.

Azbil Corporation

Corporate Member,1-12-2, Kawana, Fujisawa, Kanagawa, 251-8522