Among the most common causes for an oversupply or undersupply occurring at consumer installations in heating systems, or cooling distribution systems for air-conditioners, is the lack of hydraulic balancing.
For this reason hydraulic balancing of existing systems (Figure 1) is crucial. Furthermore, when modernisation measures have been taken to improve the energy efficiency of a system, a different energy input changes considerably the thermal and hydraulic conditions.
Measuring flow rates per ultrasoun
The energy required to heat and cool buildings is influenced by many factors. Apart from heat losses through the building fabric, the type of use and periods of use together with the settings made at the hydraulic system play a significant role.
Simultaneous control and monitoring of the flow rate in a pipe section to meet the set point can be performed using a measurement and control valve developed by KSB. The BOA-Control measurement and control valve (Figure 2) uses ultrasonic sensors, so it has no physical contact with the fluid flowing through the pipe. The flow rate is determined by sensors measuring the transit time difference of the ultrasound waves. Because the sensors are located on the outside of the valve, neither dissolved substances nor impurities in the water can influence the accuracy of the measurement.
A BOATRONIC measuring computer, which is part of the system, calculates the flow rate directly via the ultrasonic sensors. With the ultrasound measurement method the flow rate can be determined regardless of valve positions and minimum differential pressures. During commissioning of the system the flow rate can be verified directly with the measuring computer to see if the valve was adjusted correctly to the set value.
Periodic or continuous measurement of flow rate and temperature
The BOA-Control version enables users to connect their BOATRONIC MS measuring computer to several valves of the same type to measure the respective flow rates. For this purpose the valve bodies are provided with two measurement contacts to which the sensor set can be attached via a magnetic connector. Optimum contact is achieved by applying coupling grease between the measurement contacts and the sensors. This valve version is perfectly suited to hydraulic balancing, followed by periodic monitoring of flow rates and fluid temperatures.
The BOA-Control IMS version is factory-fitted with permanently integrated ultrasonic sensors. The sensor cable of the ultrasonic sensors is permanently fixed to the valve body and therefore can be fed through the pipe insulation. This version is specifically designed for systems where the pipe insulation is either of high quality, or where it has to satisfy specific requirements on diffusion tightness and protection from condensation.
If the operation of the heating and cooling circuit being controlled requires continuous monitoring of the flow rate, a BOA-Control IMS measurement and control valve can be used together with a BOATRONIC MS-420 measuring computer. This computer continuously transmits the flow rate and temperature values in real time to a higher-level building management system via a 4 - 20 mA signal.
The solution for automated set point control is a BOA-CVE Control IMS control valve, which forms an autonomous control loop together with an actuator. The valve position can be adjusted to the required set point for the corresponding pipe section. The valve automatically controls the set point when temperature or flow rate fluctuate.