The city centre of Dresden has experienced numerous constructional changes after the German reunification with the reconstruction of the Frauenkirche (Our Lady s Church) as well as the new construction of the surrounding “Quarters at the Neumarkt”.
In doing so, the damages, which occurred during World War II were finally repaired and the city centre got back its historical appearance. Today, attractive hotels, shopping malls and freehold flats unite sophisticated architecture with state-of-the-art building services – including a demand-oriented and energy-efficient air-conditioning. For this reason a refrigeration control centre was established in the basement of the Kulturpalast (Palace of Culture) located in the nearby of Neumarkt. The refrigeration control centre supplies the surrounding buildings with cooling energy. There pumps and state-of-the-art control technology of the Dortmund pump expert WILO SE are applied. These pumps optimally meet the high demands for sound insulation which had arouse due to an information centre located directly above the refrigeration control centre.
Generation of cooling energy is divided into three circuits: A re-cooling circuit supplies the refrigeration machines with cooling water from a groundwater well built especially for that purpose. The refrigeration machines provide the required temperature for the cold-water flow in a generator circuit. The isolated consumer circuit supplies the connected consumers. Wilo in-line pumps are applied in all three segments.
In the new center, two energy-efficient and low-noise turbo refrigeration machines have a total maximum cooling performance of 2.48 MW. The two units can be adjusted to the actual performance demand by means of variable speed control. Thanks to a magnetic bearing they operate in a particularly vibration-free and silent way. The refrigeration control centre in the Kulturpalast supplies the consumers with cold water via a local cooling network at nominal pressure (PN) of 10 and a maximum operating pressure of 10 bar (overpressure).
The refrigeration machines are operated in the primary or generator circuit with a cold-water feed temperature (tkW, VL) of 5°C. For a sliding temperature increase in partial load operation and to prevent the systems from freezing, the cold-water pumps provide a constant volume flow. For this purpose uncontrolled in-line pumps from the "Wilo-CronoLine-IL" series are applied. The supply of the evaporator circuits is realised locally via a joint distribution pipe in which the cold-water pumps are allocated to each refrigeration machine. Thus a constant nominal volume flow can be maintained for every refrigeration system also without the pump s speed control.
The generator circuit is isolated from the secondary or consumer circuit by means of a hydraulic shunt. Three speed-controlled "Wilo-CronoLine" in-line pumps of the "IL 125/340-30/4" type are responsible for a volume flow of about 555 m3/h in the cold-water network. Due to their monobloc construction with a lantern and a rigidly coupled standard flange motor the pumps are particularly vibration-free and silent. Flow energy losses are extremely low thanks to very smooth surfaces in the pump housing and in the impeller so that an optimum efficiency is achieved. Furthermore, the geometry of the pump housing noticeably reduces axial and radial forces, thus providing a smoother running and more operational reliability.
The mains-operated circulation pumps are controlled via a new comfortable control device. The “Wilo-Controller CC-HVAC” enables a fully automatic control of up to six pumps possible with a maximum total power of 200 kW. The pump operation can be exactly adjusted to the respective system with the control device. So only the really required cold-water quantity is circulated which is a decisive energetic advantage in seasonally varying utilisation profiles and in partial load periods of the consumers. For this reason, “Wilo-CC-HVAC” is equipped with a frequency converter which continuously controls the speed of the base load pumps.
All relevant functions and data like pump and system state or the current actual value can be called up via a multi-functional touch screen with a clearly arranged menu navigation. Moreover, extension modules are available which, e.g., allow for remote diagnosis and maintenance via Internet or mobile phone. The “Wilo-CC-HVAC” was delivered as a complete function unit ready for operation. Therefore on-site installation effort is reduced to a minimum.
Picture: Dresden Neumarkt