Schiessl Bulgaria, a Sofia-based industrial refrigeration manufacturer, recently delivered, to a new German logistics center, two low-temperature DX (direct expansion) CO2 (R744) racks that are linked to three propane (R290) chillers.
The customized system was manufactured according to the customer’s requirements. “All of our projects are specially designed for a particular usage as per the customer’s needs,” said Plamen Traychev, Schiessl’s Project Manager.
Each DX CO2 rack provides a cold room 50kW (14.2TR) of cooling capacity, with a CO2 evaporating temperature of -32°C (-25.6°F) and a condensing temperature of -3°C (26.6°F). “The cold rooms are kept below -20°C [-4°F],” noted Traychev.
The low-temperature DX CO2 unit contain Bitzer compressors and oil-level monitoring, ESK Schultze liquid collector and oil separator/control system, Alfa Laval heat exchangers, Güntner gas coolers, Danfoss valves and filters, and a Carel controller.
In the R290 chillers, the chilled glycol is used “to keep the CO2 in subcritical mode,” and to cool down medium temperature cold rooms, Traychev said. The chillers each deliver a cooling capacity of 209.2kW (59.5TR) at an evaporating temperature of -10°C (14°F). They use the same equipment as the CO2 racks except that the chillers employ SRM screw compressors.
The CO2 units are located inside, “almost at the level of the ceiling of the facility,” said Plamen, while the propane chillers are installed outside on the ground level.
In addition to the German logistics center, the end user has many logistics facilities globally. “We have another big project in Russia for the same company, but due to the events in Ukraine [it] is currently on hold,” said Traychev.
As well as chillers and racks, Schiessl provides condensing units, among other equipment. Schiessl has been producing CO2-based systems for five years “Usually we are producing on average six to seven units per year,” said Traychev.
Schiessl currently has a low-temperature industrial transcritical CO2 rack under production with a cooling capacity of 100 KW (28.4TR) at an evaporating temperature of -32 °C (-25.6°F) and a condensing temperature of -10 °C (14°F).
“All of our projects are specially designed for a particular usage as per the customer’s needs.”
Plamen Traychev, Schiessl
