Attaining a higher flexibility degree in CO₂ compressor racks

CO₂ compressor racks have shown their suitability for commercial and industrial refrigeration systems at any
location and climate. Even if some references state that CO₂ units can compete in capital cost with any other
alternative solution, often investment costs are still the main barrier for the global expansion of CO₂.
This work explores, numerically and experimentally, the implementation of “pivoting” compressors, i.e.
compressors that can operate in the medium temperature (MT) and parallel compressor suction groups,
depending on ambient conditions, cooling loads and use of ejector. The objective is to increase the flexibility
of CO₂ compressor racks, keeping the efficiency and, potentially, reducing the investment. This study shows
that this solution with “pivoting” compressors is beneficial in ejector-supported systems, since the investment
cost of the ejectors is compensated by a lower number of installed compressors, as compressor capacities can
be applied in more flexible ways.
Keywords: Refrigeration, Carbon Dioxide, Compressors, Switching, Pivoting.