System efficiency and energy saving with parallel compression and ejectors under flooded conditions.

In the recent years various installation of CO2 systems consisting of parallel compression and ejectors has emerged on the market. The installations include the MultiEjector system provided by Danfoss which is consisted of a number of fixed geometry ejectors operating in parallel. The ejectors can function both with vapor, unloading the compressor, and liquid as pump enabling flooded operation of the evaporators. Installations have been commissioned in various locations with different climate characteristics.
The paper present field data from one supermarket installation consisting of parallel compressors and ejectors supporting flooded operation. The purpose is to evaluate the level of energy savings that can be the obtained running the system flooded. The installation was operated in respectively a superheated and flooded configuration to investigate the benefits of running the system with flooded evaporators versus dry expansion mode. The performance was evaluated based on energy measurements and the computed system efficiency (COP), the data shows an improvement in medium temperature COPMT of 30% and estimated reduction yearly energy consumption of 4.5% corresponding to 13050 kWh – running flooded vs. dry expansion mode.