TU Braunschweig’s IfT has been working with CO2 for more than two decades.
TU (Technical University) Braunschweig, based in Braunschweig (Brunswick), Germany, is using a new ejector test rig that enables it to thoroughly assess the operating behavior of ejectors in transcritical CO2 refrigeration systems.
Ejectors are among the technologies that allow transcritical CO2 systems to be used efficiently in warm ambient climates. Ejectors have been increasingly employed in European supermarkets.
In the test rig, the temperatures on the suction and drive side as well as all three pressures at the nozzles of the ejector can be controlled, explained Professor Jürgen Köhler, Director of TU’s Institute for Thermodynamics (IfT).
In particular, the “innovative” adjustability of the medium pressure “allows predictions to be made about the operating behavior of ejectors for a wide range of refrigeration systems and heat pumps or a wide range of operating points,” said Köhler. The test rig can be used to measure ejectors with two-stage discharge as well as ejectors with gas discharge.
“[The test rig] allows predictions to be made about the operating behavior of ejectors for a wide range of refrigeration systems and heat pumps or a wide range of operating points.” – Professor Jürgen Köhler, Institute for Thermodynamics
In addition, IfT is able to assess flooded evaporation in refrigeration systems by setting two-phase area intake states with defined vapor content. The test rig can be used to measure ejectors with discharge areas in the two-phase area as well as in the gas area.
IfT also employs an oil separation system that allows the lubricant to be separated after the compressor and metered into the suction and drive side in a defined manner “in order to investigate the effect of the lubricant – even with uneven distribution in the circuit,” Köhler noted.
TU Braunschweig, through IfT, provides research that seeks to develop and improve energy- efficient thermal systems. IfT has been working with CO2 for more than two decades.
IfT specializes in working on ejectors, lubricants for CO2, and fault detection, via modeling and simulation. Work has focused on experimental investigations of refrigeration components and systems, the design and layout of test rigs, the development of complex control strategies, as well as system analysis.